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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Science of the Total Environment 441 (2012) 125–131 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv pH-dependent aquatic criteria for 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol Liqun Xing a, Hongling Liu a,⁎, John P. Giesy a, b, c, Hongxia Yu a,⁎ a b c State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 20046, China Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada Department of Biology & Chemistry and State Key Laboratory for Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong H I G H L I G H T S ► The effects of pH on toxicity of CPs to Daphnia magna and Scenedesmus obliquus were studied. ► There were strong correlations between the logarithmic EC50s and pH values for both D. magna and S. obliquus. ► The manipulation of data (intra-species variation or/and proportions of taxonomic groups) is important to the result of WQC. a r t i c l e i n f o Article history: Received 26 June 2012 Received in revised form 18 September 2012 Accepted 24 September 2012 Available online xxxx Keywords: Chlorophenol Species sensitivity weighted distribution (SSWD) Intra-species variation Taxonomic groups Water quality criteria Pesticides a b s t r a c t Due to their agricultural as well as industrial uses, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) are ubiquitous in the environment and recognized as priority pollutants in many countries. In this study, effects of pH on toxicity to the crustacean Daphnia magna and the alga Scenedesmus obliquus were investigated. Combined published toxicity data of the three chlorophenols along with; relationships between toxicity and pH reported here were used to establish pH-dependent water quality criteria (WQC). The WQC expressed as a function of pH, also considered intra-species variation and proportions of taxonomic groups. At pH 7.8, the recommended acute exposure water quality criteria (WQC) were 286.2 μg 2,4-DCP/l, 341.5 μg 2,4,6-TCP/l and 11.4 μg PCP/l. The recommended chronic exposure WQC were 16.3 μg 2,4-DCP/l, 54.6 μg 2,4,6-TCP/land 3.9 μg PCP/l. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. 1. Introduction In China water quality criteria (WQC) refer to concentrations of individual pollutants that are developed for specified uses of surface waters, including drinking water, recreation, production of fish, propagation of other aquatic life, and industry and agriculture. WQC are used in environmental management and pollution control. Several methods have been developed for derivation of WQC (ANZECC and ARMCANZ, 2000; CCME, 2007; EU, 2003; Stephan et al., 1985). In China, WQC have been established for some chemicals; but they are mainly derived from environmental quality standards or criteria of more developed countries, which may be over- or under-protected aquatic organisms due to differences between hydrographic conditions and species in China and those in other countries (Wu et al., 2010; Yan et al., 2012). The Major State Basic Research Development Program and the National Major Project of Science & Technology Ministry of China on the Development of China were initiated in 2008. ⁎ Corresponding authors. Tel./fax: +86 25 89680356. E-mail addresses: hlliu@nju.edu.cn (H. Liu), yuhx@nju.edu.cn (H. Yu). Until now, studies on WQC in China have been based on effects of chemicals on several native species, but the methods used to derive WQC were those of more developed countries, such as those of the United States Environmental Protection Agency (USEPA) (USEPA-FAV method), or Canada, Australia and New Zealand (mainly species sensitivity distributions (SSDs) method). SSDs have some advantages compared to USEPA approaches. The SSD approach considers all available toxicity data and uses the entire species distribution to calculate the protection level with a graphical component that allows visualization of the SSD. Another criticism of the EPA-FAV method is that the procedure can give poor extrapolations from small datasets or with datasets with severe outliers in toxicity values (Stephan et al., 1985). SSD methods are increasingly used in derivation of water quality criteria by many countries including China. In China, historically WQC had not considered intra-species variation or/and proportions of taxonomic groups, and/or physical–chemical properties of water. Due to their use in agriculture and industry as pesticides, wood preservatives, personal care formulations, and in the production of other products chlorophenols (CPs) are ubiquitous globally in 0048-9697/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2012.09.060 Author's personal copy 126 L. Xing et al. / Science of the Total Environment 441 (2012) 125–131 surface waters, groundwater, wastewater, sludge and drinking waters (Czaplicka, 2004; Davì and Gnudi, 1999; Gao et al., 2008; Olaniran and Igbinosa, 2011; Zheng et al., 2011). CPs have received worldwide attention due to their toxicity to aquatic life, persistence, and potential to bioaccumulate (Ge et al., 2007; Olaniran and Igbinosa, 2011; Xing et al., 2012a; Zheng et al., 2011; Zheng et al., 2012). In China among CPs, 2,4-dichlorophenol (2,4-DCP), 2,4,6trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) are ubiquitous at concentrations of as much as 103.70 μg/l (Gao et al., 2008; Zheng et al., 2012; Zhong et al., 2010). Such concentrations pose risks to humans and aquatic organisms (Cooper and Jones, 2008; Ma et al., 2011; Ruder and Yiin, 2011; Xing et al., 2012a). For these reasons, CPs are classified as priority pollutants in the United States (USEPA, 1991) and China (Zhou et al., 1990). Recently, WQC for 2,4-DCP, 2,4,6-TCP and PCP for protection of aquatic life based on resident aquatic biota have been derived in China (Jin et al., 2012a; Jin et al., 2012b; Jin et al., 2011; Yin et al., 2003a; Yin et al., 2003b). However, these WQC did not consider effects of water characteristics such as pH on toxicity of CPs. Because chlorophenols have an OH functional group depending on pH they can exist as protonated or ionic forms (Kishino and Kobayashi, 1995). The proportion of the CPs in each form is governed by their pKa (Erickson et al., 2006a,b). The degree of dissociation of weak acids, such as phenols and specifically CPs is thus a function of pH. The fraction of weakly acidic organic compounds is directly proportional to acidity and thus inversely proportional to pH (Kishino and Kobayashi, 1995; Saarikoski and Viluksela, 1981). Unionized molecules are more soluble in lipids and can diffuse more easily across membranes to exert their effects. This effect is important because the toxicity of some compounds is affected by the degree of dissociation (USEPA, 1991). In the case of CPs, the protonated form, which is unionized, is more accumulated and thus more toxic than the unionized form. For this reason, in 1995, the USEPA developed criteria for protection of aquatic life from the effects of CPs in ambient water that were dependent on pH. WQC for PCP are expressed as functions of pH (http://www.epa.gov/ost/criteria/wqctable/). Intra-species variation or/and proportions of taxonomic groups is also an important consideration in the derivation of WQC. The effects of the species considered in deriving the WQC are more important than the statistical methods employed (Duboudin et al., 2004; Maltby et al., 2005; Wheeler et al., 2002). WQC for the three CPs were derived by the use of a log-logistic model, a typical species sensitivity distribution (SSD) approach (CCME, 2007; Duboudin et al., 2004; Maltby et al., 2005; Wheeler et al., 2002) and corrected for the effects of pH. The effects of pH on toxicity of the three CPs, including 2,4-DCP, 2,4,6-TCP and PCP, to the crustacean, Daphnia magna and green alga, Scenedesmus obliquus were investigated. According to Duboudin et al. (2004), four cases in SSD analyses should be considered when deriving a criterion (Fig. A.1 of the Supplementary information): (1) intra-species variation weighted by the use of geometric means, and unweighted proportions of taxonomic groups; (2) intra-species variation weighted by each data to give each species the same weight, and unweighted proportions of taxonomic groups; (3) intra-species variation weighted by geometric mean, and weighted proportions of taxonomic groups; (4) intra-species variation weighted by each data to give each species the same weight, and weighted proportions of taxonomic groups. 2. Materials and methods 2.1. Test chemicals and culture of daphnids and alga 2,4-DCP (CAS No. 120-83-2, 99% purity) and 2,4,6-TCP (CAS No. 88-06-2, 98% purity) were purchased from Acros Organics (Morris Plains, NJ, USA), and PCP (CAS No. 87-86-5, 98% purity) was purchased from Sigma-Aldrich (St Louis, MO, USA). All chemicals were used as supplied and prepared in HPLC-grade dimethyl sulfoxide (DMSO) and were kept in thoroughly cleaned glass containers and stored at − 20 °C. Final concentrations of DMSO in experimental media were equal to or less than 0.05% for D. magna and 0.1% for S. obliquus, respectively. S. obliquus was cultured in 250 ml Erlenmeyer flasks containing 150 ml of WC medium (Kilham et al., 1998) under continuous light conditions (illuminance 5000 lx) in incubator at 25± 1 °C. Cells during exponential phase were used for experiments. D. magna were cultured and maintained following previously published methods (Xing et al., 2012b). Tap water, aerated for more than three days, was used as culture medium, which had a pH of 8.12± 0.11, dissolved oxygen concentration of 6.07± 0.24 mg/l, conductivity of 319 ± 9.1 μs/cm, alkalinity of 95.48 ±4.64 mg/l as CaCO3, and hardness of 125.5 ±4.95 mg/l as CaCO3. Neonates (b 24 h) were used for the experiments. 2.2. Experimental design Three different pH values adjusted by the use of buffers (MES (2-(N-morpholino) ethanesulfonic acid, CAS No. 4432-31-9) for pH 6.5, MOPS (3-(N-morpholino) propanesulfonic acid, CAS No. 1132-61-2) for pH 7.5 and CHES (2-(cyclohexylamino) ethanesulfonic acid, CAS No. 103-47-9) for pH 9.0). Buffers with purities of ≥98% and 0.1 mol/l NaOH were used to maintain constant nominal pH (Neuwoehner and Escher, 2011). Concentrations of buffers in media were 5 mmol/l for D. magna, 20 mmol/l for S. obliquus, respectively. Static non-renewal tests were conducted for all the experiments and the pH values were measured by pH meter (Thermo Scientific Orion 5-Star Plus) at the beginning and end of the experiments. Studies of S. obliquus were initiated with a cell density approximately 10 5 cells/ml in 50 ml Erlenmeyer flasks containing 20 ml sterilized WC medium for 72 h (OECD, 2002; Yeesang and Cheirsilp, 2011). The other conditions were the same as those during cultivation. For each chemical and each pH, algae were exposed to seven concentrations, one solvent control and one medium control with three replicates. Algae were pre-cultured in medium at various designed pH values for at least 3 days before the experiment in order to allow for adaptation. Algae cell numbers were determined every 24 h from 0 to 72 h. Studies of D. magna experiments were conducted in 6-well Costar® plates with 10 ml medium according to OECD method 202 (OECD, 2004). The observed endpoint, immobilization, was judged by the inability to move during 10 s after exposure for 24 and 48 h. Experimental conditions were the same as those used during culture. For each chemical and each pH, seven concentration groups, solvent control and medium control with five repeats containing five neonates were carried out. Simultaneously, tests with the reference chemical K2Cr2O7 were conducted to ensure that the test organisms exhibited constant sensitivities to this reference toxicant as an indicator of the physiological status of the organisms. D. magna were pre-cultured in medium at designed pHs for at least 2 weeks before the experiment in order to allow for adaptation. 2.3. Collection and selection of toxicity data Values for toxicities to fish, amphibians, molluscs, crustaceans, algae for the three CPs considered here were collected from the ECOTOX database (http://cfpub.epa.gov/ecotox/) or published literature. The acceptability of toxicity data was assessed according to the principles of aquatic life criteria with accuracy, relevance and reliability (CCME, 2007; Klimisch et al., 1997; Stephan et al., 1985). If endpoints were extrapolated beyond the range of concentrations tested or greater than the limit of solubility, the studies were not included in the database. Briefly, only toxicity data for species existing broadly or cultivated widely in freshwaters of China were considered and characterized by a specific endpoint, duration time and pH value. In Author's personal copy L. Xing et al. / Science of the Total Environment 441 (2012) 125–131 addition, median effective concentration (EC50) or half lethal concentration (LC50) was chosen as measurement endpoints of acute toxicity. Since derivation of no observed effect concentrations (NOECs) or lowest observed effect concentrations (LOECs) is dependent on experimental design and hypothesis testing; while the maximum acceptable toxicant concentration (MATC) or 10% effective concentration (EC10) are more invariability and preferred (CCME, 2007) either the MATC or EC10 was selected as the measurement endpoint chronic toxicity. Only when MATC and EC10 are not available, values of NOECs or LOECs were used as substitutes in deriving WQC (See Table A.1–A.6 of the Supplementary information). 2.4. Data analysis The algae cell density was determined by measurement of optical density (OD) by the use of a Synergy H4 Hybrid Microplate Reader (excitation/emission: 485 nm/685 nm) (BioTek Instruments Inc., Winooski, VT). Two aliquants of 100-μl media from each Erlenmeyer flask were added wells of a 96-well plate and read by Synergy H4 Hybrid Microplate Reader. A linear standard curve (r 2 = 0.9996, p b 0.01) between fluorometric measurements and cell density was developed. Percent inhibition of growth rate was calculated from (Eqs. (1) and (2)) according to OECD (OECD, 2002). μi ¼ lnðN i =N0 Þ ti ð1Þ Ii ¼ μ C −μ T μC ð2Þ Where: μi is the average growth rate from the initial to time i (i= 24, 48, 72 h); Ni, N0 are the biomass concentrations at the initial and time i, respectively; ti is the exposure period; Ii is the percent inhibition on average growth rate at ti; μC, μT are the growth rates in the control and treatment, respectively. Values for EC50 and EC10 with 95% confidence intervals (CI) for S. obliquus were calculated by the use of a four-parameter log-logistic regression model (Chalifour and Juneau, 2011). EC50 values with 95% CI for D. magna were calculated through three-parameter log-logistic regression model (Syberg et al., 2008; Xing et al., 2012b). WQC with 95% CI were derived by use of previously published methods (Duboudin et al., 2004), in which three taxonomic groups, algae, invertebrates and vertebrates, were divided and corresponding proportions were 64%, 26% and 10% (taking a value of 2.5 for the factor change in species number between trophic levels), respectively (Forbes and Calow, 2002). Final values of WQC were calculated by taking the geometric mean of two weighted taxonomic groups (cases (3) and (4) in introduction section intra-species variation weighted by geometric mean, and weighted proportions of taxonomic groups; intra-species variation weighted by each data to give each species the same weight, and weighted proportions of taxonomic groups). Regression analyses were performed by the use of the statistical computing software R (R version 2.10.1, R Development Core Team, http://www.r-project.org/). 127 16.87 mg PCP/l, respectively. Lesser values of pH resulted in lesser values for the EC50 (more toxic potency). Values for the 72 h EC10 were 9.76 to 50.45 mg 2,4-DCP/l, 2.00 to 14.20 mg 2,4,6-TCP/l, 0.17 to 12.44 mg PCP/l. The 24-h EC50 values were used as acute toxicity and the 72-h EC10 values were used as chronic toxicity due to rapid cell division rate of algae (CCME, 2007). The 24-h EC50 for the reference, positive control chemical K2Cr2O7 indicated that the physiological condition and thus sensitivity of D. magna were consistent among experiments. Mean values of the measured final pH values were 7.13, 8.05, 8.81, with ranges of 6.86–7.39, 7.82–8.27, and 8.71–8.90, for 2,4-DCP, 2,4,6-TCP and PCP, respectively. There were some deviations between the measured pH values and the desired pH values, but the effects of pH values on the toxicity were still demonstrable (Table 2). Similarly, the 48-h EC50 values were directly proportional to pH with lesser toxic potencies observed at greater pHs, which increased (lesser toxicity) from 0.76 to 1.83 mg 2,4-DCP/l, 1.17 to 6.62 mg 2,4,6-TCP/l, 0.062 to 1.23 mg PCP/l, at 7.13 to 8.81 pHs, respectively. The measured pH values were used in establishing relationships between toxicity and pH. 3.2. Relationships between toxicity and pH values for three chlorophenols The experimental results presented here as well as the data from published literature were used to develop statistically significant predictive relationships between pH and toxicity for the three CPs to aquatic organisms. Acute toxicity values were log-transformed (lnEC50/LC50) and regressed as a function of pH (-log of concentration of hydrogen ion) (Eqs. (3)–(4); Fig. 1). In the linear regression analyses, data were available for three species for 2,4-DCP, four species for 2,4,6-TCP, and nine species for PCP. The taxa for which data were available included algae, crustaceans, and fish (Tables A.1, A.3, A.5 of the Supplementary information for details). The regression results indicated significant corrections between log-transformed acute toxicity data (lnEC50/LC50) and pH (Fig. 1): 2 For 2; 4−DCP : lnEC50 ¼ 0:6274 pH−2:6567 r ¼ 0:42; p ¼ 0:02364 ð3Þ 2 For 2; 4; 6−TCP : lnEC50 ¼ 0:8937 pH−5:3075 r ¼ 0:86; p < 0:00001 ð4Þ 2 For PCP : lnEC50 ¼ 0:7330 pH−6:3261 r ¼ 0:33; p ¼ 0:00020 ð5Þ There were few studies on effects of pH on chronic toxicity to aquatic organisms such that there was insufficient information from which to develop relationships between chronic toxicity data and pHs. In this study, the chronic toxicity related to pH use the same slope of acute toxicity. In one study (Chèvre et al., 2006), the theory that slopes of the acute and chronic species sensitivity distribution (SSD) are parallel has been espoused. Also, the use of acute to chronic ratios to develop criteria that is used by USEPA is based on the slopes being equal. 3. Results 3.3. Distribution of selected toxicity data 3.1. Effect of pH on toxicity of chlorophenols According to the relationships between toxic potency of chlorophenols and pH (Eqs. (3)–(5)), the toxicity data were normalized to a pH of 7.8 (Supporting information Table A.1–A.6), and plotted concurrently (Fig. 2). Based on the distribution of the toxicity data (Fig. 2), PCP (lesser EC/LC50 or EC10/MATC) was more potently toxic than were 2,4-DCP or 2,4,6-TCP; while the toxic potencies of 2,4-DCP and 2,4,6-TCP were nearly the same. When normalized to a pH of 7.8 acute toxic potency ranged from 1770.5 (D. magna) to 321,024.5 μg/l (Lemna minor) with a median 7902.1 μg/l for Algae grew well in all media at various pHs with or without 0.1% DMSO. The measured final values for pH were 6.47–6.54, 7.46–7.53, 8.78–9.05 for 2,4-DCP, 2,4,6-TCP and PCP, respectively. Relationships between concentrations–responses were observed in all experiments with exposure concentrations causing 0–100% effects (Table 1). Values of 48-h EC50 were directly proportional pH with values ranging from 13.81 to 71.81 mg 2,4-DCP/l, 2.71 to 25.83 mg 2,4,6-TCP/l, 0.29 to Author's personal copy 128 L. Xing et al. / Science of the Total Environment 441 (2012) 125–131 Table 1 Toxicity (mg/l) of three chlorophenols to S. obliquus at various pH. Chemicals 2,4-DCP Endpoints pH = 9.0 72 h 24 h 48 h 72 h 24 h 48 h 72 h 8.72 (7.76–9.67) 13.81 (13.06–14.57) 2.38 9.76 (8.91–10.61) 14.14 (13.42–14.86) 2.00 2.71 2.46 15.08 (12.84–17.32) 19.61 (18.97–20.25) 2.45 (1.66–3.25) 3.47 (2.79–4.16) 0.30 65.92 (41.02–90.82) 71.81 (58.36–85.26) 18.82 (11.11–26.53) 25.83 (18.76–32.91) 14.87 EC50 0.26 0.17 (0–0.35) 0.28 (0.20–0.35) 15.69 (12.39–18.99) 19.53 (18.90–20.15) 2.84 (2.19–3.5) 3.43 (2.23–4.63) 0.19 50.45 (45.04–55.86) 54.26 (35.43–73.1) 14.2 (2.86–25.55) 34.76 0.24 (0.09–0.39) 0.29 29.35 (21.33–37.38) 32.08 (20.86–43.29) 3.59 (0.230–56.06) 3.76 (0.25–57.11) 0.12 114.03 (109.21–118.85) 137.48 (130.45–144.52) 28.13 EC10 21.61 (18.55–24.68) 30.16 (28.98–31.33) 1.56 (0.18–2.94) 4.37 (2.65–6.08) 0.26 0.93 (0.09–1.77) 0.89 (0.31–1.47) 1.23 (0.47–1.99) 16.87 18.07 (7.57–28.58) EC10 EC10 EC50 PCP pH= 7.5 48 h EC50 2,4,6-TCP pH= 6.5 24 h 30.69 (22.5–38.87) 15.03 (5.805–24.26) 24.06 (13.40–34.73) 12.440 Note: numerical values in brackets represent 95% confidence intervals. 2,4-DCP, from 591.5 (Lepomis macrochirus) to 69,114.0 μg/l (Corbicula fluminea) with a median 5712.8 μg/l for 2,4,6-TCP, from 85.9 (L. macrochirus) to 34,376.7 μg/l (Rhabditis sp.) with a median 277.7 μg/l for PCP, respectively. Chronic toxic potencies at pH 7.8 ranged from 99.5 (Macrobrachium superbum) to 21,211.3 μg/l (S. obliquus) with a median 918.2 μg/l for 2,4-DCP, from 115.5 (Mylopharyngodon piceus) to 4668.0 μg/l (C. fluminea) with a median 578.5 μg/l for 2,4,6-TCP, from 18.1 (M. superbum) to 7470.0 μg/l (Chlorella kessleri) with a median of 85.8 μg/l for PCP. by functions of pH (Eqs. (6)–(11)):WQC for chronic exposure (μg/l): WQC2;4−DCP ¼ expð0:6274 pH þ 0:7630Þ ð6Þ WQC2;4;6−TCP ¼ expð0:8937 pH−1:1374Þ ð7Þ WQCPCP ¼ expð0:7330 pH−3:2847Þ ð8Þ WQC for chronic exposure (μg/l): WQC2;4−DCP ¼ expð0:6274 pH−2:1056Þ ð9Þ WQC2;4;6−TCP ¼ expð0:8937 pH−2:9706Þ ð10Þ WQCPCP ¼ expð0:7330 pH−4:3564Þ ð11Þ 3.4. Derivation of water quality criteria for three chlorophenols Toxicity potencies at various pH values were adjusted to a common pH 7.8. Then, based on the intra-species variation and proportions of taxonomic groups, four cases (see Section 1) were derived and SSD analyses were used to estimate WQC (Table 3 and Fig. 3). Values of HC5s (5% hazard concentrations) based on SSDs of data normalized to pH 7.8 for acute exposure ranged 446.8–953.3 μg 2,4-DCP/l, 570.6–872.6 μg 2,4,6-TCP/l and 21.2–30.9 μg PCP/l, respectively considering the four cases such as intra-species variation weighted by the use of geometric means, and unweighted proportions of taxonomic groups; intra-species variation weighted by each data to give each species the same weight, and unweighted proportions of taxonomic groups; intra-species variation weighted by geometric mean, and weighted proportions of taxonomic groups; intra-species variation weighted by each data to give each species the same weight, and weighted proportions of taxonomic groups. Values of HC5s based on SSDs of data normalized to pH 7.8 for chronic exposure ranged 10.6– 31.8 μg 2,4-DCP/l, 49.0–62.5 μg 2,4,6-TCP/l and 3.4–5.1 μg PCP/l (Table 3). The final WQC for acute exposure were calculated by dividing the HC5s by 2 (EU, 2003; Stephan et al., 1985). Combined with the linear relationships (Eqs. (3)–(5)), the final WQC expressed as μg/l are given 4. Discussion The effects of pH on toxic potency of three CPs on two domestic organisms existing widely in aquatic environment were investigated to provide complementary toxicity data. Values of pH studied ranged from 6.86 to 8.90 for D. magna, and 6.47 to 9.05 for S. obliquus; which are proper survival or growth pH range (Neuwoehner and Escher, 2011; OECD, 2004). There were some deviations between measured pH values and the desired pH values for D. magna, a result that is consistent with the results of a previous study by Altenburger et al. (2010) which showed that only when the buffer constitution of the medium was increased to 20 mmol/l, would the pH remain constant over the test period. However, the greater concentration of buffer can affect survival of D. magna (De Schamphelaere et al., 2004). In spite of the fact that pH values are not always consistent with the desired pH values, the Table 2 Toxicity (mg/l) of three chlorophenols to D. magna at various pH. Chemicals 2,4-DCP 2,4,6-TCP PCP pH = 7.13 pH = 8.05 pH = 8.81 24-h EC50 48-h EC50 24-h EC50 48-h EC50 24-h EC50 48-h EC50 3.46 (2.90–4.01) 2.30 (1.91–2.69) 0.16 (0.16–0.17) 0.76 (0.55–1.05) 1.17 (0.71–1.63) 0.06 (0.03–0.09) 4.44 (4.13–4.76) 10.92 (7.58–14.26) 0.99 (0.99–1.00) 1.50 (0.56–4.03) 3.76 (1.07–6.45) 0.35 (0.32– 0.37) 16.53 (14.42–18.64) – 1.83 (0.63–5.37) 6.26 3.77 (3.75–3.79) 1.23 (0.85–1.61) Note: numerical values in brackets represent 95% confidence intervals. Author's personal copy L. Xing et al. / Science of the Total Environment 441 (2012) 125–131 6 7 8 9 5 10 2 0 -4 -1 -1 5 1 Algae 4 Crustaceans 2 Fish 1 Molluscs 1 Insects -2 ln(EC50)(mg/l) 1 2 3 4 1 Algae 1 Crustacean 2 Fish 0 ln(EC50)(mg/l) 4 3 2 1 PCP (n=37) 4 2,4,6-TCP (n=13) 1 Algae 1 Crustacean 1 Fish 0 ln(EC50)(mg/l) 5 2,4-DCP (n=12) 129 6 pH 7 8 9 10 4 5 pH 6 7 8 9 10 pH Fig. 1. Relationships between log-transformed acute toxicity data of three chlorophenols and pH values. n is the total number of toxicity data. 1.2E+6 derived from this study were similar to those determined in previous studies (Jin et al., 2011; Jin et al., 2012a; Jin et al., 2012b). Based on the endpoints selected for use in generating SSD (generally MATC or EC10 ≥NOEC), the previous values would be expected to be greater than WQC derived in this study. These results are not consistent with those of some previous studies which showed no significant difference between native species sensitivity and non-native species sensitivity to 2,4-DCP (Jin et al., 2011). Since these CPs contain a basic OH group that is protonated and thus positively charged at physiological pH. Only non-ionized molecules are lipid-soluble and can diffuse easily across the cell membranes. In contrast, the ionized molecules are usually unable to penetrate the lipid membrane transport and distribution of drugs that are weak organic acids or bases that are usually determined by their pKa and the pH gradient across the membrane. The different acidity constant (pKa) values of the three CPs are 7.89 for 2,4-DCP, 5.99 for 2,4,6-TCP and 4.70 for PCP, respectively (Czaplicka, 2004). The fraction of neutral molecules f(A-OH) was calculated (Eq. 12). fðA OHÞ ¼ Chemicals Intra-species variation 2,4-DCP Geometric (acute) Weighted (acute) Geometric (chronic) Weighted (chronic) Geometric (acute) Weighted (acute) Geometric (chronic) Weighted (chronic) Geometric (acute) Weighted (acute) Geometric (chronic) Weighted (chronic) n=18 2,4,6-TCP n=18 4.0E+2 2.2E+4 n=32 n=13 PCP 2,4-DCP 2,4,6-TCP PCP Fig. 2. Boxplot of toxicity data distribution of three chlorophenols. n is the number of aquatic species; geometric mean was used when there were more than one toxicity values for a species. ð12Þ Table 3 The results of calculated HC5 and 95% CI (μg/L) for three chlorophenols (pH = 7.8). Acute Chronic n=11 1 1 þ 10ðpKapHÞ At pH 7.8, there are only 50% of non-ionized molecules for 2,4-DCP, much lesser than the 2,4,6-TCP and PCP. There are some inevitable uncertainties in the process of deriving WQC including n=22 7.4E+0 E(L)C50 or MATC/EC10 (µg/l) achieved measured pH values were sufficient to develop a relationship between toxic potency and pH. There were strong correlations between log EC50s and pH for both D. magna and S. obliquus. For D. magna, 24-h EC50 for 2,4-DCP, 48-h EC50s for 2,4,6-TCP and PCP were used to establish linear regressions due to stronger correlations with pH; while for S. obliquus, 48-h EC50s for all three chlorophenols were used to establish the function between toxic potency (Table A.1, A.3, A.5 of the Supplementary information). Relationships between toxic potency and pH observed in the study results of which are reported here are consistent with those of the previous studies (Fisher et al., 1999; Fisher and Wadleigh, 1986; Saarikoski and Viluksela, 1982; Salkinoja-Salonen et al., 1981; Spehar et al., 1985), in which obvious linear correlation between toxic potency with pH was observed. The linear regression between the log of potency and pH was significant (p b 0.05) for acute toxicity. However, there were insufficient studies on the effect of pH on chronic toxicity to aquatic organisms, and not enough evidence to establish relationships between chronic toxicity and pH. In the study upon which we reported here, the slopes calculated from acute toxicity were used to adjust toxicity values and estimate WQC for chronic (continuous concentration) exposures. Slopes of the functions between pH and toxic potency based on 48-h EC50 and 72-h EC10 of S. obliquus are similar (Fig. A.2 of the Supplementary Information). This result is consistent with the slope (1.005) used by the USEPA for both acute and chronic WQC for PCP (http://www.epa.gov/ost/criteria/wqctable/). The slope for PCP based on Chinese species was 0.7330, which was lesser than the slope of 1.005 used by USEPA. In addition, at pH 7.8, the recommended WQC for PCP given USEPA were 19 and 15 μg/l for acute and chronic exposures, respectively; while the calculated WQC for PCP based on Chinese species were lesser with values of 11.4 μg/l for acute and 3.9 μg/l for chronic continuous exposures. Although the WQC results mean mean mean mean mean mean Proportions of taxonomic groups Unweighted Weighted 953.3 (669.1–1428.0) 511.9 (407.1–639.7) 31.8 (18.6–55.9) 17.1 (11.0–27.4) 738.2 (587.0–937.3) 872.6 (733.6–1042.1) 59.7 (42.7–84.4) 62.5 (45.6–87.4) 30.9 (20.3–48.1) 29. (24.8–34.1) 4.1 (2.4–7.3) 5.1 (3.2–8.1) 733.3 (358.2–1496. 7) 446.8 (306.4–635.9) 24.9 (10.3–52.9) 10.6 (4.7–23.1) 570.6 (370.9–814.0) 817.8 (618.9–1087.9) 49.0 (31.0–72.3) 60.9 (41.6–89.7) 21.2 (11.3–39.5) 24.5 (19.3–31.1) 3.4 (1.8–6.547) 4.5 (2.8–7.2) Note: HC5 is the 5% hazard concentration; numerical values in brackets represent 95% confidence intervals (CI). Author's personal copy 12 6 8 10 12 2 4 6 8 10 12 100 60 acute chronic 4 6 8 10 10 12 14 100 60 20 0 Species affected [%] 100 60 20 8 2 4 6 8 10 12 log Conc (µg/l) 12 acute chronic 4 6 8 10 12 14 100 B-4 60 acute chronic 2 4 6 8 10 12 log Conc (µg/l) C-3 2 10 20 60 acute chronic 4 8 0 100 B-3 2 6 log Conc (µg/l) log Conc (µg/l) C-2 2 6 20 100 0 20 60 acute chronic 0 20 Species affected [%] 100 60 20 0 Species affected [%] acute chronic 4 4 log Conc (µg/l) C-1 log Conc (µg/l) 2 log Conc (µg/l) B-2 log Conc (µg/l) 2 14 Species affected [%] 10 12 12 log Conc (µg/l) C-4 100 8 10 acute chronic 60 6 8 acute chronic 20 4 Species affected [%] 100 20 60 acute chronic 0 Species affected [%] B-1 2 6 log Conc (µg/l) A-4 0 4 0 100 60 20 2 Species affected [%] 14 0 12 Species affected [%] 10 100 8 acute chronic 60 6 log Conc (µg/l) A-3 0 20 4 acute chronic Species affected [%] 2 A-2 Species affected [%] 0 20 60 acute chronic 0 100 A-1 Species affected [%] L. Xing et al. / Science of the Total Environment 441 (2012) 125–131 Species affected [%] 130 2 4 6 8 10 12 log Conc (µg/l) Fig. 3. The simulated species sensitivity distribution curves for 2,4-DCP (A), 2,4,6-TCP (B) and PCP (C) calculated using log-logistic. Letters A, B, C stand for different chemicals; numbers stand for consideration of toxicity data: (1) intra-species variation weighted by geometric mean, and unweighted proportions of taxonomic groups; (2) intra-species variation weighted by each data to give each species the same weight, and unweighted proportions of taxonomic groups; (3) intra-species variation weighted by geometric mean, and weighted proportions of taxonomic groups; (4) intra-species variation weighted by each data to give each species the same weight, and weighted proportions of taxonomic groups. applied statistical method, toxicity data and other hypotheses (Duboudin et al., 2004; Versteeg et al., 1999). Different results can be obtained based on the same toxicity data due to different methods, hypotheses or data choice (Duboudin et al., 2004; Wheeler et al., 2002). In this study, intra-species variation, inclusion of taxonomic groups and pH were considered when deriving WQC that would be protective under actual eco-environment (Duboudin et al., 2004; Forbes and Calow, 2002). The WQC derived based on four cases were similar (Table 3), a result that might be due to the distribution of toxicity data, in which for most species the toxic potency has been developed at only one pH (Maltby et al., 2005). Until now, intra-species variation sensitivities were incorporated into WQC by the use of geometric mean (CCME, 2007; EU, 2003; Stephan et al., 1985; Zhong et al., 2010). In order to avoid a bias that might be introduced by the use of this method, geometric means of HC5 calculated by cases (3) and (4) (see Section 1) were used to estimate the final WQC. The results obtained in this study are based on toxicity tests conducted under laboratory conditions. When site-specific WQC are derived, water-effect ratio (WER) is an important method to adjust the difference between the toxicity in laboratory dilution water and that in the water at the site. A WER is calculated by dividing the toxicity value (e.g., LC50) determined in water of interest (certain site), by the corresponding toxicity value determined in a standard laboratory water. Thus, studies on WER are further needed to set site-specific WQC. 5. Conclusions The toxic potencies of 2,4-DCP, 2,4,6-TCP and PCP to aquatic organisms were inversely proportional to pHs. Recommended WQC values were functions of pH (Eqs. (6)–(11)). When normalized to a pH of 7.8, the acute WQC values were 286.2 μg 2,4-DCP/l, 341.5 μg 2,4,6-TCP/l and 11.4 μg PCP/l, while chronic WQC values were 16.3 μg 2,4-DCP/l, 54.6 μg 2,4,6-TCP/l and 3.9 μg PCP/l. Acknowledgments This research was supported by the Natural Science Foundation of China (No. 20977047), Major State Basic Research Development Program (No. 2008CB418102) and the National Major Project of Science & Technology Ministry of China (No. 2012ZX07529-003-02, 2008ZX08526-003, 2012ZX07506-001). Prof. Giesy was supported by the Canada Research Chair program, an at large Chair Professorship at the Department of Biology and Chemistry and State Key Laboratory in Marine Pollution, City University of Hong Kong, and the Einstein Professor Program of the Chinese Academy of Sciences. Appendix A. Supplementary data Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.scitotenv.2012.09.060. References Altenburger R, Krüger J, Eisenträger A. Proposing a pH stabilised nutrient medium for algal growth bioassays. Chemosphere 2010;78:864–70. ANZECC, ARMCANZ. Australian and New Zealand guidelines for fresh and marine water quality. National water quality management strategy paper no 4. Canberra: ANZECC and ARMCANZ; 2000. CCME. A protocol for the derivation of water quality guidelines for the protection of aquatic life. Winnipeg, Manitoba: Canadian Council of Ministers of the Environment; 2007. Chalifour A, Juneau P. Temperature-dependent sensitivity of growth and photosynthesis of Scenedesmus obliquus, Navicula pelliculosa and two strains of Microcystis aeruginosa to the herbicide atrazine. Aquat Toxicol 2011;103:9-17. Author's personal copy L. Xing et al. / Science of the Total Environment 441 (2012) 125–131 Chèvre N, Loepfe C, Singer H, Stamm C, Fenner K, Escher BI. Including mixtures in the determination of water quality criteria for herbicides in surface water. Environ Sci Technol 2006;40(2):426–35. Cooper GS, Jones S. Pentachlorophenol and cancer risk: focusing the lens on specific chlorophenols and contaminants. Environ Health Perspect 2008;116:1001–8. Czaplicka M. Sources and transformations of chlorophenols in the natural environment. Sci Total Environ 2004;322:21–39. Davì ML, Gnudi F. Phenolic compounds in surface water. Water Res 1999;33:3213–9. De Schamphelaere KAC, Heijerick DG, Janssen CR. Comparison of the effect of different pH buffering techniques on the toxicity of copper and zinc to Daphnia magna and Pseudokirchneriella subcapitata. Ecotoxicology 2004;13:697–705. Duboudin C, Ciffroy P, Magaud H. Effects of data manipulation and statistical methods on species sensitivity distributions. Environ Toxicol Chem 2004;23:489–99. Erickson RJ, Mckim JM, Lien GJ, Hoffman AD, Batterman SL. Uptake and elimination of ionizable organic chemicals at fish gills: i. model formulation, parameterization, and behavior. Environ Toxicol Chem 2006 aa;25:1512–21. Erickson RJ, Mckim JM, Lien GJ, Hoffman AD, Batterman SL. Uptake and elimination of ionizable organic chemicals at fish gills: II. model formulation, parameterization, and behavior. Environ Toxicol Chem 2006 bb;25:1522–32. [EU, 2003. Technical guidance document on risk assessment. EUR 20418 EN/2.]. Fisher SW, Hwang H, Atanasoff M, Landrum PF. Lethal body residues for pentachlorophenol in zebra mussels (Dreissena polymorpha) under varying conditions of temperature and pH. Ecotoxicol Environ Saf 1999;43:274–83. Fisher SW, Wadleigh RW. Effects of pH on the acute toxicity and uptake of [14C] pentachlorophenol in the midge, Chironomus riparius. Ecotoxicol Environ Saf 1986;11:1–8. Forbes VE, Calow P. Species sensitivity distributions revisited: a critical appraisal. Hum Ecol Risk Assess 2002;8:473–92. Gao JJ, Liu LH, Liu XR, Zhou HD, Huang SB, Wang ZJ. Levels and spatial distribution of chlorophenols 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol in surface water of China. Chemosphere 2008;71:1181–7. Ge JC, Pan JL, Fel ZL, Wu GH, Giesy JP. Concentrations of pentachlorophenol (PCP) in fish and shrimp in Jiangsu Province, China. Chemosphere 2007;69:164–9. Jin XW, Zha JM, Xu YP, Giesy JP, Richardson KL, Wang ZJ. Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species. Chemosphere 2012a;86:17–23. Jin XW, Zha JM, Xu YP, Giesy JP, Wang ZJ. Toxicity of pentachlorophenol to native aquatic species in the Yangtze River. Environ Sci Pollut Res 2012b;19:609–18. Jin XW, Zha JM, Xu YP, Wang ZJ, Kumaran SS. Derivation of aquatic predicted no-effect concentration (PNEC) for 2,4-dichlorophenol: comparing native species data with non-native species data. Chemosphere 2011;84:1506–11. Kilham SS, Kreeger DA, Lynn SG, Goulden CE, Herrera L. COMBO: a defined freshwater culture medium for algae and zooplankton. Hydrobiologia 1998;377:147–59. Kishino T, Kobayashi K. Relation between toxicity and accumulation of chlorophenols at various pH, and their absorption mechanism in fish. Water Res 1995;29:431–42. Klimisch HJ, Andreae M, Tillmann U. A systematic approach for evaluating the quality of experimental toxicological and ecotoxicological data. Regul Toxicol Pharmacol 1997;25:1–5. Ma YB, Liu CS, Lam PKS, Wu RSS, Giesy JP, Hecker M, et al. Modulation of steroidogenic gene expression and hormone synthesis in H295R cells exposed to PCP and TCP. Toxicology 2011;282:146–53. Maltby L, Blake N, Brock TC, van den Brink PJ. Insecticide species sensitivity distributions: importance of test species selection and relevance to aquatic ecosystems. Environ Toxicol Chem 2005;24:379–88. Neuwoehner J, Escher BI. The pH-dependent toxicity of basic pharmaceuticals in the green algae Scenedesmus vacuolatus can be explained with a toxicokinetic ion-trapping model. Aquat Toxicol 2011;101:266–75. OECD. OECD guideline for testing chemicals. Proposal for updating guideline 201, freshwater alga and cyanobacteria, Growth Inhibition Test; 2002. OECD. OECD guideline for testing of chemicals. Daphnia sp., Acute Immobilisation Test; 2004. Olaniran AO, Igbinosa EO. Chlorophenols and other related derivatives of environmental concern: properties, distribution and microbial degradation processes. Chemosphere 2011;83:1297–306. 131 Ruder AM, Yiin JH. Mortality of US pentachlorophenol production workers through 2005. Chemosphere 2011;83:851–61. Saarikoski J, Viluksela M. Influence of pH on the toxicity of substituted phenols to fish. Arch Environ Contam Toxicol 1981;10:747–53. Saarikoski J, Viluksela M. Relation between physicochemical properties of phenols and their toxicity and accumulation in fish. Ecotoxicol Environ Saf 1982;6:501–12. Salkinoja-Salonen M, Saxelin ML, Pere J, Jaakkola T, Saarikoski J, Hakulinen R, et al. Analysis of toxicity and biodegradability of organochlorine compounds released into the environment in bleaching effluents of kraft pulping. In: Keith LH, editor. Advances in the identification and analysis of organic pollutants in water, Butterworth, Stoneham. MA2; 1981. p. 1131–64. Spehar RL, Nelson HP, Swanson MJ, Renoos JW. Pentachlorophenol toxicity to amphipods and fathead minnows at different test pH values. Environ Toxicol Chem 1985;4:389–97. Stephan CE, Mount DI, Hansen DJ, Gentile JH, Chapman GA, Brungs WA. Guidelines for deriving numerical national water quality criteria for the protection of aquatic organisms and their uses. PB85-227049. Springfield, VA, USA: National Technical Information Service; 1985. Syberg K, Elleby A, Pedersen H, Cedergreen N, Forbes VE. Mixture toxicity of three toxicants with similar and dissimilar modes of action to Daphnia magna. Ecotoxicol Environ Saf 2008;69:428–36. USEPA. Water quality criteria summary. Ecological risk assessment branch (WH-585) and human risk assessment branch (WH-550D). Washington, DC, USA: Health and Ecological Criteria Division, USEPA; 1991. Versteeg DJ, Belanger SE, Carr GJ. Understanding single-species and model ecosystem sensitivity: data-based comparison. Environ Toxicol Chem 1999;18:1329–46. Wheeler JR, Grist EPM, Leung KMY, Morritt D, Crane M. Species sensitivity distributions: data and model choice. Mar Pollut Bull 2002;45:192–202. Wu FC, Meng W, Zhao XL, Li HX, Zhang RQ, Cao YJ, et al. China embarking on development of its own national water quality criteria system. Environ Sci Technol 2010;44:7992–3. Xing LQ, Liu HL, Giesy JP, Zhang XW, Yu HX. Probabilistic ecological risk assessment for three chlorophenols in surface waters of China. J Environ Sci (China) 2012a;24: 329–34. Xing LQ, Sun J, Liu HL, Yu HX. Combined toxicity of three chlorophenols 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol to Daphnia magna. J Environ Monit 2012b;14(6):1677–83. Yan ZG, Zhang ZS, Wang H, Liang F, Li J, Liu HL, et al. Development of aquatic life criteria for nitrobenzene in China. Environ Pollut 2012;162:86–90. Yeesang C, Cheirsilp B. Effect of nitrogen, salt, and iron content in the growth medium and light intensity on lipid production by microalgae isolated from freshwater sources in Thailand. Bioresour Technol 2011;102:3034–40. Yin DQ, Hu SQ, Jin HJ, Yu LW. Deriving freshwater quality criteria for 2,4,6-trichlorophenol for protection of aquatic life in China. Chemosphere 2003a;52:67–73. Yin DQ, Jin HJ, Yu LW, Hu SQ. Deriving freshwater quality criteria for 2,4-dichlorophenol for protection of aquatic life in China. Environ Pollut 2003b;122:217–22. Zheng WW, Wang X, Yu H, Tao XG, Zhou Y, Qu WD. Global trends and diversity in pentachlorophenol levels in the environment and in humans: a meta-analysis. Environ Sci Technol 2011;45:4668–75. Zheng WW, Yu H, Wang X, Qu WD. Systematic review of pentachlorophenol occurrence in the environment and in humans in China: not a negligible health risk due to the re-emergence of schistosomiasis. Environ Int 2012;42:105–16. Zhong WJ, Wang DH, Xu XW, Luo QA, Wang BY, Shan XQ, et al. Screening level ecological risk assessment for phenols in surface water of the Taihu Lake. Chemosphere 2010;80:998-1005. Zhou WM, Fu DQ, Sun ZG. List for priority pollutants in waters. Environ Monit in China 1990;6:1–3. [in Chinese]. pH-dependent aquatic life criteria for 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol Liqun Xing1, Hongling Liu1*, John P. Giesy1,2,3, and Hongxia Yu1* 1 State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 20046, China 2 Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada 3 Department of Biology & Chemistry and State Key Laboratory for Marine Pollution,, City University of Hong Kong, Kowloon, Hong Kong, SAR, China Authors for correspondence: School of the Environment Nanjing University Nanjing 210046, China Tel: 86-25-89680356 Fax: 86-25-89680356 E-mail: hlliu@nju.edu.cn (H. Liu); yuhx@nju.edu.cn (H.Yu) Table S1 Species Group Acute toxicity data for Chinese species used to calculate water quality criteria for 2,4-dichlorophenol. Duration time (d) Effect Methods Endpoints R, U LC50 MORT measurements Concentrations Concentrations (μg/l) (μg/l) pH=7.8 7.24 19250 pH Geomean References 27347.66 27347.66 (Jin, et al., 2009) 4524.73 (Yin, et al., 2003b) Corbicula fluminea Invertebrate 4 Chironomus sp. Invertebrate 4 S, U LC50 MORT 7.0 2740 4524.73 Daphnia magna Invertebrate 2 S, M LC50 MORT 8 3680 3246.29 (Kim, et al., 2006) Daphnia magna Invertebrate 2 S, U LC50 MORT 7.0 2120 3500.89 (Yin, et al., 2003b) Daphnia magna* Invertebrate 1 S, U EC50 IMBL 7.1 3460 This study Daphnia magna* Invertebrate 1 S, U EC50 IMBL 8.0 4440 This study Daphnia magna* Invertebrate 1 S, U EC50 IMBL 8.8 16530 This study Daphnia magna Invertebrate 2 S, U EC50 IMBL 7.1 763 1165.01 This study Daphnia magna Invertebrate 2 S, U EC50 IMBL 8.0 1500 1286.43 This study Daphnia magna Invertebrate 2 S, U EC50 IMBL 8.8 1830 974.51 1134.58 This study Limnodrilus hoffmeisteri Invertebrate 4 S, U LC50 MORT 7.0 9890 16331.96 16331.96 (Yin, et al., 2003b) Radix plicatula Invertebrate 4 R, U LC50 MORT 7.0 3370 5565.09 5565.09 (Yin, et al., 2003b) Vertebrate 4 R, U LC50 MORT 7.0 9460 15621.88 15621.88 (Yin, et al., 2003b) Vertebrate 4 R, U MORT 7.0 5250 8669.65 8669.65 (Yin, et al., 2003b) Carassius auratus Vertebrate 4 R, U LC50 MORT 7.0 7940 13111.81 (Yin, et al., 2003b) Carassius auratus Vertebrate 4 F, M LC50 MORT 7.8 1240 1240 (Birge, et al., 1979) Carassius auratus Vertebrate 4 F, M LC50 MORT 7.8 1760 1760 Ictalurus punctatus Vertebrate 4.5 F, M LC50 MORT 7.8 1700 1700 Ictalurus punctatus Vertebrate 4.5 F, M LC50 MORT 7.8 1850 1850 1773.42 (Birge, et al., 1979) Vertebrate 4 R, NR MORT 7.24 4010 5696.84 5696.84 (Jin, et al., 2010) Vertebrate 4 R, NR MORT 6.21 2630 7127.17 7127.17 (Kennedy, 1990) Bufo bufo gargarizans Ctenopharyngodon idellus Mylopharyngodon piceus Oncorhynchus mykiss LC50 LC50 LC50 3058.67 (Birge, et al., 1979) (Birge, et al., 1979) Species Group Duration time (d) Methods Poecilia reticulata* Vertebrate 4 R, NR Poecilia reticulata* Vertebrate 4 R, NR Poecilia reticulata* Vertebrate 4 R, NR Poecilia reticulata* Vertebrate 14 R, NR Poecilia reticulata* Vertebrate 14 R, NR Poecilia reticulata* Vertebrate 14 R, NR Vertebrate 4 R, NR Rana nigromaculata Vertebrate 4 R, U Tilapia mossambica Vertebrate 4 Tilapia zilli Vertebrate Lemna minor Endpoints LC50 Effect measurements pH Concentrations Concentrations (μg/l) (μg/l) pH=7.8 Geomean References (Saarikoski and Viluksela, MORT 6 3483.37 10768.24 MORT 7 5520.77 9116.79 MORT 8 7620.79 6722.63 MORT 6.1 3250.87 MORT 7.3 4187.94 MORT 7.8 5915.62 MORT 7.24 2480 3523.23 3523.23 (Jin, et al., 2010) LC50 MORT 7.0 9850 16265.91 16265.91 (Yin, et al., 2003b) R, U LC50 MORT 7.0 8350 13788.37 13788.37 (Yin, et al., 2003b) 2 R, U LC50 MORT 6.6 2297 4874.43 4874.43 (Yen, et al., 2002) Plant 3 S, U LC50 MORT 5.1 59000 320678 320678 (Blackman, et al., 1955) Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 6.5 13810 This study Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 7.5 19530 This study Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 9.0 71810 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 6.5 30160 68143.55 Scenedesmus obliquus Plant 1 S, U EC50 GGRT 7.5 32080 38719.09 Scenedesmus obliquus Plant 1 S, U EC50 GGRT 9.0 137480 64785.28 Plagiognathops microlepis LC50 LC50 LC50 LC50 LC50 LC50 1982) (Saarikoski and Viluksela, 1982) 8706.47 (Saarikoski and Viluksela, 1982) (Könemann and Musch, 1981) (Könemann and Musch, 1981) (Könemann and Musch, 1981) This study This study 55497.75 This study Table S2 Chronic toxicity data for Chinese species used to calculate water quality criteria for 2,4-dichlorophenol. Species Group Duration time (d) Methods Endpoints Effect measurements pH Concentrations Concentrations (μg/l) (μg/l) pH=7.8 Geomean References (Jin, et al., 2011) Corbicula fluminea Invertebrate 21 R, M MATC SURV 7.24 1410 2003.12 2003.12 Daphnia magna Invertebrate 21 R, U MATC GREP 7.0 556 918.16 918.16 Vertebrate 30 R, U MATC WGHT 7.0 707 1167.51 1167.51 Vertebrate 60 F, U MATC GREP 7.0 707 1167.51 1167.51 Carassius auratus Vertebrate 8 F, M LC01 MORT 7.8 39.8 39.8 Carassius auratus Vertebrate 8 F, M LC01 MORT 7.8 48.1 48.1 Carassius auratus Vertebrate 30 R, U MATC GREP 7.0 354 584.58 103.82 Vertebrate 28 R, M MATC GGRO 7.24 490 696.12 696.12 Ictalurus punctatus Vertebrate 8.5 F, M LC01 MORT 7.8 1.6 1.6 Ictalurus punctatus Vertebrate 8.5 F, M LC01 MORT 7.8 2.8 2.8 Vertebrate 28 R, NR MATC GGRO 7.24 141.42 200.91 Vertebrate 28 R, M MATC GGRO 7.24 140 198.89 Bufo bufo gargarizans Ctenopharyngodon idellus Erythroculter ilishaeformis Mylopharyngodon piceus Mylopharyngodon piceus (Yin, et al., 2003b) (Yin, et al., 2003b) (Yin, et al., 2003b) (Birge, et al., 1979) (Birge, et al., 1979) (Yin, et al., 2003b) (Jin, et al., 2011) (Birge, et al., 1979) 2.12 (Birge, et al., 1979) (Jin, et al., 2010) 199.90 (Jin, et al., 2011) Macrobrachium Vertebrate 21 R, M MATC SURV 7.24 70 99.45 Oncorhynchus mykiss Vertebrate 27 F, M LC01 MORT 7.8 1.7 1.7 Oncorhynchus mykiss Vertebrate 27 F, M LC01 MORT 7.8 2.8 2.8 Vertebrate 28 R, NR MATC GGRO 7.24 282.84 401.82 Vertebrate 28 R, M MATC GGRO 7.24 280 397.78 399.79 (Jin, et al., 2011) Soirodela polyrhiza Plant 10 R, M MATC CHLO 7.24 2500 3551.64 3551.64 (Jin, et al., 2011) Scenedesmus obliquus Plant 3 S, U EC10 GGRT 6.5 9760 22051.76 Scenedesmus obliquus Plant 3 S, U EC10 GGRT 7.5 15080 18200.87 Scenedesmus obliquus Plant 3 S, U EC10 GGRT 9.0 50450 23773.77 superbum Plagiognathops microlepis Plagiognathops microlepis 99.45 (Jin, et al., 2011) (Birge, et al., 1979) 2.18 (Birge, et al., 1979) (Jin, et al., 2010) This study This study 21210.19 This study Table S3 Species Acute toxicity data for Chinese species used to calculate water quality criteria for 2,4,6-trichlorophenol. Group Duration time (d) Methods Endpoints Invertebrate 4 S, U LC50 Brachionus calyciflorus Invertebrate 2 S, U Chironomus sp. Invertebrate 4 S, U Corbicula fluminea Invertebrate 4 Daphnia magna Invertebrate Daphnia magna Effect measurements pH Concentrations Concentrations (μg/l) (μg/l) pH=7.8 Geomean References MORT 7.39 5500 7934.06 7934.06 (Holcombe, et al., 1987) EC50 PROG 7.5 3000 3922.47 3922.47 (Radix, et al., 1999) LC50 MORT 7.0 2060 4210.86 4210.86 (Yin, et al., 2003a) R, U LC50 MORT 7.24 41900 69114.04 69114.04 (Jin, et al., 2012a) 2 S, M LC50 MORT 8 6640 5553.19 (Kim, et al., 2006) Invertebrate 2 S, U LC50 MORT 6.5 270 862.84 (Virtanen, et al., 1989) Daphnia magna Invertebrate 2 S, U LC50 MORT 6.5 330 1054.59 (Virtanen, et al., 1989) Daphnia magna Invertebrate 2 S, U LC50 MORT 7.0 1730 3536.30 (Yin, et al., 2003a) Daphnia magna* Invertebrate 2 S, U EC50 IMBL 7.1 1167 2181.53 This study Daphnia magna* Invertebrate 2 S, U EC50 IMBL 8.0 3760 3144.58 This study Daphnia magna* Invertebrate 2 S, U EC50 IMBL 8.8 6260 2561.21 2273.51 This study Limnodrilus hoffmeisteri Invertebrate 4 S, U LC50 MORT 7.0 7520 15371.67 15371.67 (Yin, et al., 2003a) Macrobrachium superbum Invertebrate 4 R, U LC50 MORT 7.24 2050 3381.47 3381.47 (Jin, et al., 2012a) Radix plicatula Invertebrate 4 R, U LC50 MORT 7.0 2950 6030.11 6030.11 (Yin, et al., 2003a) Bufo bufo gargarizans Vertebrate 4 R, U LC50 MORT 7.0 8630 17640.63 17640.63 (Yin, et al., 2003a) Ctenopharyngodon idellus Vertebrate 4 R, U LC50 MORT 7.0 3540 7236.13 7236.13 (Yin, et al., 2003a) Carassius auratus* Vertebrate 0.208 S, U LC50 MORT 10 70000 9799.73 (Kishino and Kobayashi, 1995) Carassius auratus* Vertebrate 0.208 S, U LC50 MORT 8 7000 5854.26 (Kishino and Kobayashi, 1995) Carassius auratus* Vertebrate 0.208 S, U LC50 MORT 6 1500 7494.17 (Kishino and Kobayashi, 1995) Carassius auratus* Vertebrate 0.208 S, U LC50 MORT 7 4008.24 8193.26 (Kishino and Kobayshi, 1996) Carassius auratus Vertebrate 4 R, U LC50 MORT 7.0 4310 8810.09 8810.09 (Yin, et al., 2003a) Erythroculter ilishaeformis Vertebrate 4 R, U LC50 MORT 7.24 1990 3282.50 3282.50 (Jin, et al., 2012a) Lepomis macrochirus Vertebrate 4 F, M LC50 MORT 7.39 410 591.45 591.45 (Holcombe, et al., 1987) Aplexa hypnorum Species Group Duration time (d) Methods Endpoints Effect measurements pH Concentrations Concentrations (μg/l) (μg/l) pH=7.8 Geomean References 2012.39 (Jin, et al., 2012a) Mylopharyngodon piceus Vertebrate 4 R, U LC50 MORT 7.24 1220 2012.39 Oncorhynchus mykiss Vertebrate 4 R, NR LC50 MORT 6.2 1991 8319.13 Oncorhynchus mykiss Vertebrate 4 S, U LC50 MORT 7.8 572.03 572.03 Oncorhynchus mykiss Vertebrate 4 F, M LC50 MORT 7.39 730 1053.07 Poecilia reticulata Vertebrate 4 R, M LC50 MORT 7 2200 4497.03 (Salkinoja-Salonen, et al., 1981) Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 7 2288.1 4677.12 (Saarikoski and Viluksela, 1981) Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 5 611.48 7466.95 (Saarikoski and Viluksela, 1981) Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 8 7850.55 6565.60 (Saarikoski and Viluksela, 1981) Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 6 887.63 4434.70 5395.57 (Saarikoski and Viluksela, 1981) Plagiognathops microlepis Vertebrate 4 R, U LC50 MORT 7.24 1100 1814.45 1814.45 (Jin, et al., 2012a) Rana nigromaculata Vertebrate 4 R, U LC50 MORT 7.0 7460 15249.02 15249.02 (Yin, et al., 2003a) Plant 3 S, U LC50 MORT 5.1 5900 65887.08 65887.08 (Blackman, et al., 1955) Lemna minor (Kennedy, 1990) (Hodson, 1985) 1711.27 (Holcombe, et al., 1987) Spirostomum teres Plant 1 S, U LC50 MORT 7 2000 4088.21 4088.21 (Twagilimana, et al., 1998) Soirodela polyrhiza Plant 4 R, U LC50 MORT 7.24 8490 14004.25 14004.25 (Jin, et al., 2012a) Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 6.5 2710 This study Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 7.5 3430 This study Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 9.0 25830 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 6.5 4370 13965.26 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 7.5 3760 4916.17 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 9.0 30690 10501.28 8966.84 This study Table S4 Chronic toxicity data for Chinese species used to calculate water quality criteria for 2,4,6-trichlorophenol. Species Group Duration Methods Endpoints 2 S, U EC10 time (d) Brachionus calyciflorus Invertebrate Corbicula fluminea Invertebrate 21 R, M Daphnia magna Invertebrate 21 R, U Daphnia magna Invertebrate 21 Bufo bufo gargarizans Vertebrate Carassius auratus Effect measurements pH Concentrations Concentrations (μg/l) (μg/l) pH=7.8 Geomean References (Radix, et al., 1999) PROG 7.5 420 549.15 549.15 MATC SURV 7.24 2830 4668.08 4668.08 (Jin, et al., 2012a) NOEC PROG 8.5 500 267.47 267.47 (Radix, et al., 1999) R, U MATC GREP 7.0 283 578.48 578.48 (Yin, et al., 2003a) 30 R, U MATC GGRO 7.0 707 1445.18 1445.18 (Yin, et al., 2003a) Vertebrate 30 R, U MATC GMOR 7.0 354 723.61 723.61 (Yin, et al., 2003a) Ctenopharyngodon idellus Vertebrate 60 F, U MATC GREP 7.0 707 1445.18 1445.18 (Yin, et al., 2003a) Erythroculter ilishaeformis Vertebrate 28 R, M MATC GGRO 7.24 350 577.33 577.33 (Jin, et al., 2012a) Macrobrachium superbum Vertebrate 21 R, M MATC SURV 7.24 140 230.93 230.93 (Jin, et al., 2012a) Mylopharyngodon piceus Vertebrate 28 R, M MATC GGRO 7.24 70 115.47 115.47 (Jin, et al., 2012a) Plagiognathops microlepis Vertebrate 28 R, M MATC GGRO 7.24 140 230.93 230.93 (Jin, et al., 2012a) 2606.21 (Jin, et al., 2012a) Soirodela polyrhiza Plant 10 R, M MATC CHLO 7.24 1580 2606.21 Scenedesmus obliquus Plant 3d S, U EC10 GGRT 6.5 2000 6391.43 This study Scenedesmus obliquus Plant 3d S, U EC10 GGRT 7.5 2450 3203.35 This study Scenedesmus obliquus Plant 3d S, U EC10 GGRT 9.0 14200 4858.85 4633.53 This study Table S5 Species Ceriodaphnia dubia Group Invertebrate Acute toxicity data for Chinese species used to calculate water quality criteria for pentachlorophenol. Duration time Methods Endpoints 2 F, M LC50 (d) Effect measurements pH MORT 8 Concentrations Concentrations (μg/l) (μg/l) pH=7.8 307 Geomean References 265.14 265.14 (Hedtke, et al., 1986) Corbicula fluminea Invertebrate 4 R, M LC50 MORT 7.24 230 346.73 346.73 (Jin, et al., 2012b) Ceriodaphnia reticulata Invertebrate 2 F, M LC50 MORT 7.3 150 216.40 216.40 (Hedtke, et al., 1986) Invertebrate 4 F, M LC50 MORT 8.5 1344 804.57 (Spehar, et al., 1985) Invertebrate 4 F, M LC50 MORT 6.5 139 360.46 (Spehar, et al., 1985) Invertebrate 4 F, M LC50 MORT 7.5 465 579.37 (Spehar, et al., 1985) Invertebrate 4 F, M LC50 MORT 8 929 802.32 Chironomus riparius* Invertebrate 1 S, U LC50 MORT 9 1948 808.32 (Fisher and Wadleigh, 1986) Chironomus riparius* Invertebrate 1 S, U LC50 MORT 4 384 6223.22 (Fisher and Wadleigh, 1986) Chironomus riparius* Invertebrate 1 S, U LC50 MORT 6 465 1739.65 2060.73 (Fisher and Wadleigh, 1986) Brachionus calyciflorus Invertebrate 2 S, U EC50 HTCH 7.5 1310 1632.2 1632.2 (Radix, et al., 2000) Daphnia magna Invertebrate 2 S, M LC50 MORT 8.58 145 81.86 (Spehar, et al., 1985) Daphnia magna Invertebrate 2 S, U LC50 MORT 6.5 55 142.63 (Oikari, et al., 1992) Daphnia magna Invertebrate 2 S, U LC50 MORT 6.5 38 98.54 (Virtanen, et al., 1989) Daphnia magna Invertebrate 2 S, U LC50 MORT 6.5 55 142.63 (Virtanen, et al., 1989) Daphnia magna Invertebrate 2 S, M LC50 MORT 8 860 742.73 (Kim, et al., 2006) Daphnia magna* Invertebrate 2 S, U EC50 IMBL 7.1 61.5 102.73 This study Daphnia magna* Invertebrate 2 S, U EC50 IMBL 8.0 346 298.82 Daphnia magna* Invertebrate 2 S, U EC50 IMBL 8.8 1232 591.93 Crangonyx pseudogracilis* Crangonyx pseudogracilis* Crangonyx pseudogracilis* Crangonyx pseudogracilis* 605.94 (Spehar, et al., 1985) This study 196.41 This study Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 6.5 23.97 62.16 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 7.5 53.27 66.37 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 6.5 213.07 552.54 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 8.5 319.61 191.33 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 7.5 3089.54 3849.42 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 7.5 612.58 763.25 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 6.5 932.19 2417.37 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 8.5 9135.46 5468.82 (Fisher, et al., 1999) Dreissena polymorpha* Invertebrate 1 S, U LC50 MORT 8.5 2077.45 1243.64 Invertebrate 4 F, M LC50 MORT 7.5 121 150.76 (Spehar, et al., 1985) Invertebrate 4 F, M LC50 MORT 8 484 418.00 (Spehar, et al., 1985) Invertebrate 4 F, M LC50 MORT 8.5 790 472.92 (Spehar, et al., 1985) Invertebrate 4 F, M LC50 MORT 6.5 92 238.58 290.38 (Spehar, et al., 1985) Lymnaea acuminata Invertebrate 2 R, U LC50 MORT 7.9 228 211.89 211.89 (Gupta and Rao, 1982) Limnodrilus hoffmeisteri Invertebrate 4 R, U LC50 MORT 7 500 898.75 898.75 (Chapman, et al., 1982) Mesocyclops leuckarti Invertebrate 2 S, U LC50 MORT 7.3 138 199.09 Mesocyclops leuckarti Invertebrate 2 S, U LC50 MORT 7.3 173 249.58 222.91 (Willis, 1999) Invertebrate 4 R, M LC50 MORT 7.24 140 211.06 211.06 (Jin, et al., 2012b) Rhabditis sp. Invertebrate 2 S, U LC50 MORT 6 9188.73 34376.7 34376.7 (Kammengaet al., 1994) Simocephalus vetulus* Invertebrate 2 F, M LC50 MORT 7.3 160 230.83 (Hedtke, et al., 1986) Simocephalus vetulus* Invertebrate 2 F, M LC50 MORT 7.7 250 269.01 (Hedtke, et al., 1986) Gammarus pseudolimnaeus Gammarus pseudolimnaeus* Gammarus pseudolimnaeus* Gammarus pseudolimnaeus* Macrobrachium superbum 651.23 (Fisher, et al., 1999) (Willis, 1999) Simocephalus vetulus* Invertebrate 2 F, M LC50 MORT 8 255 220.23 Simocephalus vetulus* Invertebrate 2 F, M LC50 MORT 8.3 364 252.31 242.36 (Hedtke, et al., 1986) Tylenchus elegans Invertebrate 2 S, U LC50 MORT 6 1704.58 6377.12 6377.12 (Kammenga, et al., 1994) Viviparus bengalensis Invertebrate 2 S, U LC50 MORT 7.9 1570 1459.04 1459.04 (Gupta and Durve, 1984) Carassius auratus* Vertebrate 1 S, U LC50 MORT 9 2200 (Stehly and Hayton, 1990) Carassius auratus* Vertebrate 1 S, U LC50 MORT 8 250 (Stehly and Hayton, 1990) Carassius auratus* Vertebrate 1 S, U LC50 MORT 7 82 (Stehly and Hayton, 1990) Carassius auratus Vertebrate 4 S, U LC50 MORT 7.3 23 33.18 (Inglis and Davis, 1972) Carassius auratus Vertebrate 4 S, U LC50 MORT 7.7 49 52.73 (Inglis and Davis, 1972) Carassius auratus Vertebrate 4 S, U LC50 MORT 7.5 55 68.53 (Inglis and Davis, 1972) Carassius auratus Vertebrate 4 S, U LC50 MORT 7.3 56 80.79 (Inglis and Davis, 1972) Carassius auratus Vertebrate 4 F, M LC50 MORT 7.84 200 194.22 (Thurstonet al., 1985) Carassius auratus Vertebrate 4 F, M LC50 MORT 7.94 328 296.01 90.70 (Thurston, et al., 1985) Vertebrate 4 R, M LC50 MORT 7.24 130 195.98 195.98 (Jin, et al., 2012b) Gambusia affinis Vertebrate 4 F, M LC50 MORT 8.02 278 236.60 Gambusia affinis Vertebrate 4 F, M LC50 MORT 8.05 288 239.78 Ictalurus punctatus Vertebrate 4 S, NR LC50 MORT 7.4 66 88.49 (Mayer and Ellersieck, 1986) Ictalurus punctatus Vertebrate 4 S, NR LC50 MORT 7.4 68 91.17 (Mayer and Ellersieck, 1986) Ictalurus punctatus Vertebrate 4 F, M LC50 MORT 7.71 132 141.00 Lepomis macrochirus Vertebrate 4 S, U LC50 MORT 7.7 24 25.83 (Inglis and Davis, 1972) Lepomis macrochirus Vertebrate 4 F, NR LC50 MORT 7.4 215 288.25 (Mayer and Ellersieck, 1986) Lepomis macrochirus Vertebrate 4 S, NR LC50 MORT 7.4 32 42.90 Lepomis macrochirus Vertebrate 4 F, M LC50 MORT 8.03 202 170.66 85.92 (Thurston, et al., 1985) Mylopharyngodon piceus Vertebrate 4 R, M LC50 MORT 7.24 95 143.22 143.22 (Jin, et al., 2012b) Micropterus salmoides Vertebrate 4 R, U LC50 MORT 7.2 287 445.54 Erythroculter ilishaeformis (Hedtke, et al., 1986) (Thurston, et al., 1985) 238.18 104.39 (Thurston, et al., 1985) (Thurston, et al., 1985) (Mayer and Ellersieck, 1986) (Johansen, et al., 1985) Micropterus salmoides Vertebrate 4 R, U LC50 MORT 7.2 275 426.91 (Johansen, et al., 1985) Micropterus salmoides Vertebrate 4 R, U LC50 MORT 7.2 136 211.13 (Johansen, et al., 1985) Micropterus salmoides Vertebrate 4 R, U LC50 MORT 7.2 189 293.40 Oncorhynchus mykiss Vertebrate 4 S, NR LC50 MORT 7.4 115 154.18 (Mayer and Ellersieck, 1986) Oncorhynchus mykiss Vertebrate 4 S, NR LC50 MORT 7.4 34 45.58 (Mayer and Ellersieck, 1986) Oncorhynchus mykiss Vertebrate 4 S, NR LC50 MORT 7.4 52 69.72 (Mayer and Ellersieck, 1986) Oncorhynchus mykiss Vertebrate 4 S, NR LC50 MORT 7.4 121 162.23 (Mayer and Ellersieck, 1986) Oncorhynchus mykiss Vertebrate 4 F, U LC50 MORT 7.4 66 88.49 Oncorhynchus mykiss Vertebrate 4 F, M LC50 MORT 7.85 115 110.86 (Thurston, et al., 1985) Oncorhynchus mykiss Vertebrate 4 S, U LC50 MORT 8 160 138.18 (Sappington, et al., 2001) Oncorhynchus mykiss Vertebrate 4 R, NR LC50 MORT 6.22 153 487.15 (Kennedy, 1990) Oncorhynchus mykiss Vertebrate 4 S, U LC50 MORT 8 160 138.18 124.63 (Dwyer, et al., 2005) Vertebrate 4 R, M LC50 MORT 7.24 90 135.68 135.68 (Jin, et al., 2012b) Poecilia reticulata Vertebrate 4 R, M LC50 MORT 7 400 719.00 Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 5 42.61 331.82 Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 6 117.19 438.43 Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 7 442.12 794.72 Plagiognathops microlepis Poecilia reticulata* Vertebrate 4 R, U LC50 MORT 8 910.88 786.67 Poecilia reticulata Vertebrate 4 R, U LC50 MORT 7.7 204 219.52 329.46 (Johansen, et al., 1985) (Dominguez and Chapman, 1984) (Salkinoja-Salonen, et al., 1981) (Saarikoski and Viluksela, 1981) (Saarikoski and Viluksela, 1981) (Saarikoski and Viluksela, 1981) (Saarikoski and Viluksela, 1981) (Khangarot, 1983) Vertebrate 4 R, U LC50 MORT 7.9 970 901.44 537.37 (Gupta, et al., 1982) Plant 4 S, U EC50 ABND 7.5 130 161.97 161.97 (Mostafa and Helling, 2002) Plant 4 F, U EC50 PGRT 7 410 736.98 736.98 (Schafer, et al., 1994) Chlorella kessleri Plant 4 S, U EC50 ABND 8 34300 29622.8 29622.8 (Mostafa and Helling, 2002) Lemna minor Plant 3 S, U LC50 MORT 5.1 190 1374.88 1374.88 (Blackman, et al., 1955) Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 6.5 293 This study Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 7.5 889 This study Scenedesmus obliquus* Plant 2 S, U EC50 GGRT 9.0 16867 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 6.5 261 676.83 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 7.5 927 1155 This study Scenedesmus obliquus Plant 1 S, U EC50 GGRT 9.0 24063 9984.91 Poecilia reticulata Anabaena inaequalis Chlamydomonas reinhardtii 1983.67 This study Table S6 Chronic toxicity data for Chinese species used to calculate water quality criteria for pentachlorophenol. Species Group Duration time (d) Effect methods Endpoints S, M EC10 HTCH Measurements Concentrations Concentrations (μg/l) (μg/l) pH=7.8 7.5 600 pH Geomean References 747.57 747.57 (Radix, et al., 2000) Brachionus calyciflorus Invertebrate 2 Ceriodaphnia dubia Invertebrate 14 R, U MATC PROG 7.9 158 146.83 146.83 (Hickey, 1989) Corbicula fluminea Invertebrate 21 R, M MATC SURV 7.24 70 105.53 105.53 (Jin, et al., 2012b) Daphnia carinata Invertebrate 14 R, U MATC PROG 7.9 354 328.98 328.98 (Hickey, 1989) Daphnia magna Invertebrate 14 R, U MATC PROG 7.9 71 65.98 65.98 (Hickey, 1989) Mesocyclops leuckarti Invertebrate 6 S, U MATC MORT 7.3 104 150.04 150.04 (Willis, 1999) Macrobrachium superbum Invertebrate 21 R, M MATC SURV 7.24 12 18.09 18.09 (Jin, et al., 2012b) Simocephalus vetulus Invertebrate 14 R, U MATC PROG 7.9 71 65.98 65.98 (Hickey, 1989) Vertebrate 28 R, M MATC GGRO 7.24 25 37.69 37.69 (Jin, et al., 2012b) Mylopharyngodon piceus Vertebrate 28 R, M MATC GGRO 7.24 14 21.11 21.11 (Jin, et al., 2012b) Oncorhynchus mykiss Vertebrate 30 F, M EC10 DBMS 8.3 60 41.59 41.59 (Besser, et al., 2005) Oncorhynchus mykiss Vertebrate 30 F, M MATC DWGT 8.3 51 35.35 35.35 (Besser, et al., 2005) Vertebrate 28 R, M MATC GGRO 7.24 14 21.11 21.11 (Jin, et al., 2012b) Plant 4 S, U EC10 ABND 7.5 20 24.92 24.92 Plant 10 F, M NOEC PGRT 7 360 647.10 647.10 Chlorella kessleri Plant 2 S, U EC10 ABND 8 8650 7470.48 7470.48 Soirodela polyrhiza Plant 10 R, M MATC CHLO 7.24 350 527.64 527.64 Scenedesmus obliquus Plant 3 S, U EC10 GGRT 6.5 174 451.22 Erythroculter ilishaeformis Plagiognathops microlepis Anabaena inaequalis Chlamydomonas reinhardtii (Mostafa and Helling, 2002) (Schafer, et al., 1994) (Mostafa and Helling, 2002) (Jin, et al., 2012b) This study Scenedesmus obliquus Plant 3 S, U EC10 GGRT 7.5 301 375.03 Scenedesmus obliquus Plant 3 S, U EC10 GGRT 9.0 12440 1516.96 This study 635.54 This study Note: *, species used to establish relationship between toxicity and pH. F, flow through; R, renewal; S, static; NR, not reported; U, unmeasured; M, measured; LC01/LC50, lethal concentration to 1%/50% of test organisms; EC10/EC50, effective concentration to 10%/50% of test organisms; MATC, maximum acceptable toxicant concentration; NOEC, no-observable-effect-concentration; MORT, mortality; IMBL, immobile; GGRO, growth, general; GGRT, general growth rate; SURV, survival; reproduction, general; WGHT, weight; CHLO, chlorophyll; HTCH, hatch; ABND; abundance; PROG, progeny counts/numbers; PGRT, population growth rate; DWGT, dry weight; DBMS, dry biomass. Fig. S1 Four cases considerate in SSD analyses modified from Duboudin et al.(2004):(1) intra-species variation weighted by geometric mean, but unweighted proportions of taxonomic groups; (2) intra-species variation weighted by each data to give each species the same weight, but unweighted proportions of taxonomic groups; (3) intra-species variation weighted by geometric mean, and weighted proportions of taxonomic groups; (4) weighted both intra-species variation (each data to give each species the same weight) and proportions of taxonomic groups. The total available data were divided into three taxonomic groups: vertebrates (VE), invertebrates (INV) and algae (AL). Fig. S2 Relationships between pH values and acute toxicity data (48 h-EC50) or chronic toxicity data (72 h-EC10) of three chlorophenols. References Besser, J.M., Wang, N., Dwyer, F.J., Mayer, F.L., Ingersoll, C.G. Assessing contaminant sensitivity of endangered and threatened aquatic species: Part II. Chronic toxicity of copper and pentachlorophenol to two endangered species and two surrogate species. Arch. Environ. Contam. Toxicol. 2005; 48: 155-65. Birge, W.J., Black, J.A., Bruser, D.M. Toxicity of Organic Chemicals to Embryo-Larval Stages of Fish. PA-560/11-79-007, U.S.EPA, Washington, D.C. 1979; 60 p. Blackman, G.E., Parke, M.H., Garton, G. The physiological activity of substituted phenols. I. Relationships between chemical structure and physiological activity. Arch. Biochem Biophy, 1955; 54: 45-54. Chapman, P.M., Farrell, M.A., Brinkhurst, R.O. Relative tolerances of selected aquatic oligochaetes to combinations of pollutants and environmental-factors. Aquat. Toxicol. 1982; 2: 69-78. Dominguez, S.E., Chapman, G.A. Effect of pentachlorophenol on the growth and mortality of embryonic and juvenile steelhead trout. Arch. Environ. Contam. Toxicol. 1984; 13: 739-43. Duboudin, C., Ciffroy, P., Magaud, H. Effects of data manipulation and statistical methods on species sensitivity distributions. Environ. Toxicol. Chem. 2004; 23: 489-99. Dwyer, F.J., Mayer, F.L., Sappington, L.C., Buckler, D.R., Bridges, C.M., Greer, I.E., Hardesty, D.K., Henke, C.E., Ingersoll, C.G., Kunz, J.L., Whites, D.W., Augspurger, T., Mount, D.R., Hattala, K., Neuderfer, G.N. Assessing contaminant sensitivity of endangered and threatened aquatic species: part I. Acute toxicity of five chemicals. Arch. Environ. Contam. Toxicol. 2005; 48: 143-154. Fisher, S.W., Hwang, H., Atanasoff, M., Landrum, P.F. Lethal body residues for pentachlorophenol in zebra mussels (Dreissena polymorpha) under varying conditions of temperature and pH. Ecotox. Environ. Safe. 1999; 43: 274-283. Fisher, S.W., Wadleigh, R.W. Effects of ph on the acute toxicity and uptake of c-14 pentachlorophenol in the midge, chironomus-riparius. Ecotox. Environ. Safe. 1986; 11: 1-8. Gupta, P.K., Durve, V.S. Evaluation of the toxicity of sodium pentachlorophenate, pentachlorophenol and phenol to the snail viviparus-bengalensis (L.). Arch. Hydrobiol. 1984; 101: 469-75. Gupta, P.K., Mujumdar, V.S., Rao, P.S., Durve, V.S. Toxicity of phenol, pentachlorophenol and sodium pentachlorophenolate to a fresh-water teleost Lebistes-reticulatus (Peters). Acta Hydroch. Hydrob. 1982; 10: 177-81. Gupta, P.K., Rao, P.S. Toxicity of phenol, pentachlorophenol and sodium pentachlorophenate to a fresh-water pulmonate snail Lymnaea-acuminata (Lamarck). Arch. Hydrobiol. 1982; 94: 210-7. Hedtke, S.F., West, C.W., Allen, K.N., Norbergking, T.J., Mount, D.I. Toxicity of pentachlorophenol to aquatic organisms under naturally varying and controlled environmental-conditions. Environ.Toxicol. Chem. 1986; 5: 531-42. Hickey, C.W. Sensitivity of four new zealand cladoceran species and Daphnia magna to aquatic toxicants. New Zeal. J. Mar. Fresh. 1989; 23: 131-7. Hodson, P.V. A comparison of the acute toxicity of chemicals to fish, rats and mice. J. Appl. Toxicol. 1985; 5: 220-6. Holcombe, G.W., Phipps, G.L., Sulaiman, A.H., Hoffman, A.D. Simultaneous multiple species testing-acute toxicity of 13 chemicals to 12 diverse fresh-water amphibian, fish, and invertebrate families. Arch. Environ. Contam. Toxicol. 1987; 16: 697-710. Inglis, A., Davis, E.L. Effects of water hardness on the toxicity of several organic and inorganic herbicides to fish. Tech.Pap.No.67, Bur.Sport Fish.Wildl., Fish Wildl.Serv., U.S.D.I., Washington, DC: 1972; 22 p. Jin, X., Zha, J., Xu, Y., Giesy, J.P., Richardson, K.L., Wang, Z. Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species. Chemosphere 2012a; 86: 17-23. Jin, X., Zha, J., Xu, Y., Giesy, J.P., Wang, Z. Toxicity of pentachlorophenol to native aquatic species in the Yangtze River. Environ. Sci. Pollut. Res. Int. 2012b; 19: 609-18. Jin, X., Zha, J., Xu, Y., Wang, Z. Toxicity and oxidative stress of three chlorophenols to freshwater clam Corbicula fluminea. Asian J. Ecotox. 2009; 4: 816-22 (in Chinese) Jin, X., Zha, J., Xu, Y., Wang, Z. Acute and chronic toxicities of three chlorophenols to Mylopharyngodon piceus and Plagiognathops microlepis at early life stage. Acta Scientiae Circumstantiae 2010; 30: 1235-42 (in Chinese) Jin, X., Zha, J., Xu, Y., Wang, Z., Kumaran, S.S. Derivation of aquatic predicted no-effect concentration (PNEC) for 2,4-dichlorophenol: comparing native species data with non-native species data. Chemosphere 2011; 84: 1506-11. Johansen, P.H., Mathers, R.A.S., Brown, J.A., Colgan, P.W. Mortality of early life stages of largemouth bass, micropterus-salmoides due to pentachlorophenol exposure. Bull. Environ. Contam. Tox. 1985; 34: 377-84. Könemann, H., Musch, A. Quantitativestructure-activityrelationships in fishtoxicity studies Part 2: The influence of pH on the QSAR of chlorophenols. Toxicology 1981; 19: 223-8. Kammenga, J.E., Vangestel, C.A.M., Bakker, J. Patterns of sensitivity to cadmium and pentachlorophenol among nematode species from different taxonomic and ecological groups. Arch. Environ. Contam. Toxicol. 1994; 27: 88-94. Kennedy, C.J. Toxicokinetic studies of chlorinated phenols and polycyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) Ph.D.Thesis, Simon Fraser Univ., Canada: 1990; 188 p. Khangarot, B.S. Acute toxicity of pentachlorophenol and antimycin to common guppy (Lebistes reticulatus Peters). Indian J. Phys. Nat. Sci. 1983; 3A: 25-9. Kim, K.T., Lee, Y.G., Kim, S.D. Combined toxicity of copper and phenol derivatives to Daphnia magna: effect of complexation reaction. Environ. Int. 2006; 32: 487-92. Kishino, T., Kobayashi, K. Relation between toxicity and accumulation of chlorophenols at various pH, and their absorption mechanism in fish. Water Res. 1995; 29: 431-42. Kishino, T., Kobayshi, K. Studies on the mechanism of toxicity of chlorophenols found in fish through quantitative structure-activity relationships. Water Res. 1996; 30: 393-9. Mayer, F.L., Ellersieck, M.R. Manual of Acute Toxicity: Interpretation and Data Base for 410 Chemicals and 66 Species of Freshwater Animals. Resour. Publ. No.160, U.S. Dep. Interior, Fish Wildl. Serv., Washington, DC: 1986; 505 p. Mostafa, F.I., Helling, C.S. Impact of four pesticides on the growth and metabolic activities of two photosynthetic algae. J. Environ. Sci. Health B 2002; 37: 417-44. Oikari, A., Kukkonen, J., Virtanen, V. Acute toxicity of chemicals to Daphnia magna in humic waters. Sci. Total Environ. 1992; 118:367-77. Radix, P., Leonard, M., Papantoniou, C., Roman, G., Saouter, E., Gallotti-Schmitt, S., Thiebaud, H., Vasseur, P. Comparison of brachionus calyciflorus 2-d and microtox (r) chronic 22-h tests with Daphnia magna 21-d test for the chronic toxicity assessment of chemicals. Environ. Toxicol. Chem. 1999; 18: 2178-85. Radix, P., Leonard, M., Papantoniou, C., Roman, G., Saouter, E., Gallotti-Schmitt, S., Thiebaud, H., Vasseur, P. Comparison of four chronic toxicity tests using algae, bacteria, and invertebrates assessed with sixteen chemicals. Ecotox. Environ. Safe. 2000; .47: 186-94. Saarikoski, J., Viluksela, M. Influence of pH on the toxicity of substituted phenols to fish. Arch. Environ. Contam. Toxicol. 1981; 10: 747-53. Saarikoski, J., Viluksela, M. Relation between physicochemical properties of phenols and their toxicity and accumulation in fish. Ecotox. Environ. Safe. 198; .6: 501-12. Salkinoja-Salonen, M., Saxelin, M.L., Pere, J., Jaakkola, T., Saarikoski, J., Hakulinen, R., Koistinen, O. Analysis of toxicity and biodegradability of organochlorine compounds released into the environment in bleaching effluents of kraft pulping. In: L.H.Keith (Ed.), Advances in the Identification and Analysis of Organic Pollutants in Water, Butterworth, Stoneham. MA, 1981; 2: 1131-64. Sappington, L.C., Mayer, F.L., Dwyer, F.J., Buckler, D.R., Jones, J.R., Ellersieck, M.R. Contaminant sensitivity of threatened and endangered fishes compared to standard surrogate species. Environ. Toxicol. Chem. 2001; 20: 2869-76. Schafer, H., Hettler, H., Fritsche, U., Pitzen, G., Roderer, G., Wenzel, A. Biotests using unicellular algae and ciliates for predicting long-term effects of toxicants. Ecotox. Environ. Safe. 1994; 27: 64-81. Spehar, R.L., Nelson, H.P., Swanson, M.J., Renoos, J.W. Pentachlorophenol toxicity to amphipods and fathead minnows at different test pH values. Environ. Toxicol. Chem. 1985; 4: 389-97. Stehly, G.R., Hayton, W.L. Effect of pH on the accumulation kinetics of pentachlorophenol in goldfish. Arch. Environ. Contam. Toxicol. 1990; 19: 464-70. Thurston, R.V., Gilfoil, T.A., Meyn, E.L., Zajdel, R.K., Aoki, T., Veith, G.D. Comparative toxicity of ten organic chemicals to ten common aquatic species. Water Res. 1985; 19: 1145-55. Twagilimana, L., Bohatier, J., Groliere, C.A., Bonnemoy, F., Sargos, D. A new low-cost microbiotest with the Protozoan spirostomum teres: culture conditions and assessment of sensitivity of the ciliate to 14 pure chemicals. Ecotox. Environ. Safe. 1998; 41: 231-44. Virtanen, V., Kukkonen, J., Oikari, A. Acute Toxicity of Organic Chemicals to Daphnia magna in Humic Waters. In: A.Oikari (Ed.), Nordic Symposium on Organic Environmental Chemicals, University of Joensuu, Finland. , 1989; 29: 84-6. Willis, K.J. Acute and chronic bioassays with New Zealand freshwater copepods using pentachlorophenol. Environ. Toxicol. Chem. 1999; 18: 2580-6. Yen, J.H., Lin, K.H., Wang, Y.S. Acute lethal toxicity of environmental pollutants to aquatic organisms. Ecotox. Environ. Safe. 2002; 52: 113-6. Yin, D., Hu, S., Jin, H., Yu, L. Deriving freshwater quality criteria for 2,4,6-trichlorophenol for protection of aquatic life in China. Chemosphere 2003a; 52: 67-73. Yin, D., Jin, H., Yu, L., Hu, S. Deriving freshwater quality criteria for 2,4-dichlorophenol for protection of aquatic life in China. Environ. Pollut. 2003b; 122: 217-22.