Predicted and Observed Therapeutic Dose Exceedences of Ionizable Pharmaceuticals in Fish
Plasma from Urban Coastal Systems
W. Casan Scott1, Bowen Du1, Samuel P. Haddad1, Christopher S. Breed1, Gavin N. Saari1, Martin
Kelly2, Linda Broach2, C. Kevin Chambliss1,34, Bryan W. Brooks1*
1
Department of Environmental Science, Center for Reservoir and Aquatic Systems Research,
Baylor University, Waco, TX, USA
2
Texas Commission on Environmental Quality, Houston, TX, USA
3
Department of Chemistry and Biochemistry, Baylor University, Waco, TX, USA
*To whom correspondence may be addressed (Bryan_Brooks@baylor.edu).
Supporting Information
Methods
Spatiotemporal water chemistry
Diel changes in pH, salinity, DO, and temperature for surface (0.3 m from the surface) and
bottom water (0.3 m from sediment-water interface) were determined with multiparameter
datasondes (YSI model 600 XLM or model 6920, YSI Instruments, Yellow Springs, OH, USA)
at each site for ~24 hours. This approach followed the Texas Commission on Environmental
Quality’s (TCEQ) surface water quality monitoring procedures [1]. Data were collected at 15minute intervals from each of the four study systems once during the fall of 2012 and once
during the fall of 2013; in addition, Buffalo Bayou was sampled once during the winter 2013 and
once during the spring of 2013 for seasonal comparison. Buffalo Bayou was sampled on October
8, 2012 and September 10, 2013. Brazos River was sampled on September 5, 2012 and
September 8, 2013. Guadalupe River was sampled on September 3, 2012 and September 11,
2013. Dickinson Bayou was sampled on October 9, 2012 and September 12, 2013. These dates
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were chosen to be representative of the “Critical Monitoring Period” by the TCEQ and to not
coincide with substantial rain events [1]. Datasondes were calibrated at room temperature within
24 hours prior to data collection, and then rechecked after deployment, as previously described
[2,3]. Post-calibration checks following data collection were completed using error limits for pH,
DO, specific conductivity, and temperature of 0.5 standard units, ±5% error at saturation, ±5% in
μS/cm, and ±1 °C, respectively [2,3].
Spatiotemporal nutrient analysis
Surface and bottom water samples for total nitrogen, total phosphorus, and dissolved
nitrogen (nitrate/nitrite) and orthophosphate were collected from each site during data sonde
deployment and transported back to the laboratory for analysis. Total N concentrations were
determined using sulfanilamide method on persulfate digested samples (EPA 353.2). Total P
concentrations were determined using the molybdate-blue method on persulfate digested samples
(EPA 365.1). Nitrogen and phosphorous concentrations were measured colorimetrically using a
Lachat Quickchem 8500 Flow Injection Autoanalyzer (Loveland, CO, USA). Ammonia
concentration, and site-specific pH and temperature profiles were used to examine site-specific
National Ambient Water Quality Criteria (NAWQC) for ammonia [4,5].
Results
Spatiotemporal variability of diel water chemistry parameters
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Variability among study systems. Results from continuous datasonde monitoring of the four
study sites revealed that there were statistically significant (p < 0.05) differences between daily
means for surface and bottom pH, salinity, dissolved oxygen, and temperature. Daily oscillations
differed between the surface and bottom water among all four systems and between 2012 and
2013 (Figure S1). Further, summer stratification and winter mixing appears to have influenced
variability of surface-to-bottom water chemistry of Buffalo Bayou (Figure S2). Water chemistry
profiles taken during the fall of 2012 revealed significant (p < 0.05) differences in pH, salinity,
dissolved oxygen, and temperature between each of these tidally influenced rivers. Only the
surface water pH of the Guadalupe River and Dickinson Bayou, and surface water salinity
between the Brazos River and Dickinson Bayou were not significantly different (p > 0.05).
Further, surface and bottom water chemistry parameters at each site were significantly different
(p < 0.05) with dissolved oxygen in the Guadalupe River as the only exception (Figure S1).
During the fall 2013 sampling period, pH differed (p < 0.05) among water bodies with the
exception of the Guadalupe River and the Brazos River, and the Guadalupe River and Dickinson
Bayou, and Dickinson Bayou and the Brazos River. As expected for tidally influenced systems,
salinities were significantly higher in bottom water samples than surface (p < 0.05), except for
Dickinson Bayou and Buffalo Bayou. Temperature across all tidally influenced systems was
significantly different (p < 0.05) with the exception of the Brazos River and Dickinson Bayou
surface water (Figure S1). Dissolved oxygen in Brazos River surface water was not significantly
different from the surface water of the Guadalupe River, Buffalo Bayou, or Dickinson Bayou.
Dissolved oxygen of Dickinson Bayou bottom water was not significantly different than bottom
waters of Buffalo Bayou or the Brazos River, all with median values below 2 mg/L.
Subsequently, we examined exceedences of near-surface (0.3m from surface) dissolved oxygen
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water quality criteria for both surface and bottom sites (Table S1). Though depressed dissolved
oxygen was occasionally observed in surface water samples (e.g., Guadalupe River in Fall 2012
and 2013), dissolved oxygen was commonly observed below water quality criteria in bottom
locations of all four systems during Fall 2012 and 2013 (Table S1).
Seasonal variability within Buffalo Bayou. In the present study, we also explored seasonal pH
dynamics of Buffalo Bayou. Median pH values were typically significantly different (p < 0.05)
across the four seasons sampled except for surface water in the fall of 2012, winter 2013, and fall
of 2013, and the bottom water between the fall of 2012 and fall of 2013. Salinity was not
significantly different between surface and bottom water during the winter of 2013. Surface
water salinity measurements in winter and spring 2013 also did not significantly differ, while
only the bottom water in spring 2013 exhibited some marine influence with intermittent salinities
above 1.0 ppt. Temperature was greater at the surface compared to the bottom across all seasons
except during the Fall of 2013 (Figure S2). Dissolved oxygen was significantly different (p <
0.05) across all four seasons and higher in surface water, compared to bottom, at all sample
locations. Depressed dissolved oxygen levels were observed in bottom water samples of Buffalo
Bayou during Fall 2012 and 2013 sampling events but not during Winter or Spring 2013 (Table
S1).
Spatiotemporal variability of nutrients
Sampling period did not have a significant effect on total nitrogen, total phosphorous,
orthophosphate, ammonia, or nitrate/nitrite concentrations (Table S2). Concentrations of total
nitrogen, total phosphorous, orthophosphate, and nitrate/nitrite did significantly differ (p < 0.05)
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among the four sampling sites, while ammonia did not. Concentrations of all nutrients were not
significantly different with depth, nor was there a significant interaction between site and depth
(Table S2). Probabilistic distributions of measured ammonia concentrations and site-specific
Criterion Continuous Concentrations (CCC), which are applied to near-surface samples (0.3m
from surface) for regulatory purposes, are reported in Figure S3. The CCC is an estimate of the
highest concentration of a pollutant to which an aquatic community can be exposed indefinitely
(chronic limit) without resulting in unacceptable adverse effects. It is important to note that the
bottom water sample from Dickinson Bayou in Fall 2013 was the only water body to exceed the
ammonia CCC (Figure S3), but this observation would not have been made if only surface water
samples were collected.
References
1. Texas Commission on Environmental Quality. 2012. Surface Water Quality Monitoring
Procedures Volume 1: Physical and Chemical Monitoring Methods for Water. Sediment, and
Tissue. Austin, TX.
2. Texas Commission of Environmental Quality. 2012 Guidance for Assessing and Reporting
Surface Water Quality in Texas. Monitoring Operations, Surface Water Quality Monitoring
Program, Austin, TX.
3. Texas Commission of Environmental Quality. 2003. Surface Water Quality Monitoring
Procedures Volume 1: Physical and Chemical Monitoring Methods for Water, Sediment and
Tissue. Publication NO. RG-415, December 2003, Austin, TX.
4. U.S. Environmental Protection Agency. 2009. Draft 2009 Update aquatic life ambient water
quality criteria for ammonia-Freshwater. EPA-822-D-09-001. Office of Water, Washington,
DC.
5. U.S. Environmental Protection Agency. 2013. Update aquatic life ambient water quality
criteria for ammonia-Freshwater. EPA-822-D-09-001. Office of Water, Washington, DC.
5
Figure S1: A box-and-whisker plot showing diel distributions of pH in Fall 2012 (A) and in Fall
2013 (B), salinity in Fall 2012 (C) and in Fall 2013 (D), dissolved oxygen in Fall 2012 (E) and in
Fall 2013 (F), and temperature in Fall 2012 (G) and in Fall 2013 (H) in Buffalo Bayou, Brazos
River, Guadalupe River, and Dickinson Bayou, Texas, USA.
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Figure S2: A box-and-whisker plot showing diel distributions of pH (A), salinity (B), dissolved
oxygen (C), and temperature (D) in Buffalo Bayou, Texas, USA, during 2012 and 2013.
7
Figure S3: Probability distributions of Ammonia Criterion Continuous Concentration (CCC)
overlaid with measured surface and bottom water concentrations of ammonia for Buffalo Bayou
in 2012 (A) and 2013 (B), Brazos River in 2012 (C) and 2013 (D), Guadalupe River in 2012 (E)
and 2013 (F), and Dickinson Bayou in 2012 (G) and 2013 (H).
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Table S1: Site-specific daily mean and minimum dissolved oxygen for Buffalo Bayou, Brazos
River, Guadalupe River, and Dickinson Bayou. Daily mean and minimum water quality criteria
are based on designated Aquatic Life Uses as described by the Texas Commission on
Environmental Quality for surface water samples (0.3m from surface). This table includes the
probability of exceeding dissolved oxygen criteria over a 24-hour deployment (n=96) during
each sampling period for both surface and bottom waters.
Dissolved Oxygen Criteria
(mg/L)
Percent Below Criteria
Sampling Period
Site
Depth
Daily Mean
Daily Minimum
Fall 2012
Buffalo Bayou
Surface
1
1
0%
0%
Bottom
1
1
13%
13%
Surface
4
3
0%
0%
Bottom
4
3
96%
92%
Surface
5
4
99%
0%
Bottom
5
4
99%
0%
Surface
4
3
4%
0%
Bottom
4
3
82%
76%
Surface
1
1
0%
0%
Bottom
1
1
19%
19%
Surface
4
3
40%
14%
Bottom
4
3
100%
96%
Surface
5
4
96%
31%
Bottom
5
4
100%
93%
Surface
4
3
15%
3%
Bottom
4
3
86%
79%
Surface
1
1
0%
0%
Brazos River
Guadalupe River
Dickinson Bayou
Fall 2013
Buffalo Bayou
Brazos River
Guadalupe River
Dickinson Bayou
Winter 2013
Spring 2013
Buffalo Bayou
Daily Mean
Daily Minimum
Bottom
1
1
0%
0%
Surface
1
1
0%
0%
Bottom
1
1
0%
0%
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Table S2: Nutrient concentrations in mean (N =2) surface and bottom waters of four Gulf of
Mexico estuaries in Texas, USA, during different sampling events. TN, total nitrogen; TP, total
phosphorous; Phosphate; Ammonia; Nitrate/Nitrite; MDL, method detection limit.
Sampling Period
Site
Depth
TN
(µg/L)
TP
(μg/L)
Phosphate
(μg/L)
Ammonia
(μg/L)
Nitrate/Nitrite
(μg/L)
Fall 2012
Buffalo
Surface
6440
1330
1260
206
5550
Bottom
4590
1090
1020
138
4570
Brazos
Surface
705
148
48.6
< MDL
2.05
Bottom
1350
363
113
186
255
Surface
1020
188
115
22.3
544
Bottom
NA
NA
NA
NA
NA
Surface
961
225
169
< MDL
0.35
Bottom
954
310
262
237
67.2
Surface
5820
1450
1310
275
5030
Bottom
4520
1360
1090
68.7
4030
Surface
758
264
171
< MDL
22.2
Bottom
689
268
193
< MDL
25.1
Guadalupe
Surface
3280
399.5
264
< MDL
2730
Bottom
2930
377
302
< MDL
2520
Dickinson
Surface
1090
361
233
< MDL
0.35
Bottom
1710
691
511.5
915.5
5.11
Guadalupe
Dickinson
Fall 2013
Buffalo
Brazos
Sampling Period
Site
Depth
TN(ug/L)
TP(ug/L)
Phosphate
(ug/L)
Ammonia
(ug/L)
Nitrate/Nitrite
(ug/L)
Fall 2012
Buffalo Bayou
Surface
6440
1330
1260
206
5550
Bottom
4590
1090
1020
138
4570
Surface
2000
415
248
< MDL
1430
Bottom
1670
398
266
16.1
1090
Spring 2013
Surface
7275
579
343
551
2470
Bottom
1752
419
517
482
1680
Fall 2013
Surface
5820
1450
1310
275
5030
Bottom
4520
1360
1090
68.7
4030
MDL:
2.15
1.05
1.35
8.46
0.82
Winter 2013
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