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Heavy metal levels in water supply of the Tapacurá River Basin, Pernambuco
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State - Northeastern Brazil
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Fabio M. Aprile a;* , Marc Bouvy b, Welington B. C. Delitti c
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a
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E-mail address:aprilefm@hotmail.com
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b
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France. E-mail address:bouvy@ird.fr
Oceanography Institute, São Paulo University, São Paulo, Brazil.
Institut de Recherche pour le Développement, Université du Montpellier II, Montpellier,
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c
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E-mail address:delitti@ib.usp.br
Institute of Biosciences, São Paulo University, São Paulo, Brazil.
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Short title: Heavy metal in water supply of the Tropical River
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Abstract
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Distribution and enrichment of heavy metals (Fe, Mn, Cu, Pb and Zn) in waters at the Tapacurá
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River basin were examined. The basin is situated in Zona da Mata region (7.90º-8.50ºS; 35º-
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35.85ºW) in Pernambuco State, Northeastern Brazil. Water samples from eight sites in the basin
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were collected monthly in the period from March/1997 to December/1998. Metal mean levels in
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surface waters ranged from 0.30 to 4.22 for Fe, 0.02 to 1.09 for Mn, <0.001 to 0.014 for Cu,
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<0.006 to 0.029 for Pb and <0.003 to 0.020 for Zn mg.l-1. Heavy metals showed a large
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heterogeneous horizontal distribution with hotspots in the industrial and agricultural areas. Data
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Corresponding Author: Tel: +55 11 38149949 Oceanography Institute, São Paulo University, Rua
Doralice P. Teixeira 48/13 São Paulo 05417-070 Brazil.
E-mail address:aprilefm@hotmail.com
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analyses by EF and Cp indicated moderate contamination by Cu and Zn in the basin. Linear
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regression analysis showed independence between Fe/Mn, Zn/Cu and Zn/Pb. The results
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indicated the potential pathways of heavy metals via the transport of soil and sediment from the
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agricultural areas to the reservoir. The first step to apply a remedial measure is the inspection of
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the agricultural areas and the use controlled of fertilizers and herbicides.
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Keywords: trace metal; distribution; remediation; water supply; river basin; Enrichment factor;
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Index of contamination; anthropogenic sources; linear regression; Tropical River.
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1. Introduction
Some heavy metals are considered as essential as well as toxic for organism health. Many
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of the toxic properties of metals are expressed as behavioral aberrations. Some of these arise
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from direct actions on the central nervous system; others arise from primary events elsewhere,
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but still influence behavior (Clarisse, Amorim & Lucas, 1999; Aprile, Siqueira & Parente, 2005).
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Human exposure to metals can be assessed by measuring metal levels on man himself or by
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measuring their levels in the various compartments of the environment, including the aquatic
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ecosystems. There are natural levels of trace metals in various forms in air, soil and water (IPCS,
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2001). Water column is an intrinsic part of the ecosystem, and ionic balance in the water is in
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equilibrium between input and binding capacity of the system. These background levels are
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generally innocuous to plant and animal life (WHO, 1996), which have adapted to them.
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Elevated concentrations of trace metals in aquatic ecosystems pose toxicological risks to biota
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and may impair water quality (Baird & Cann, 2005).
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The collection of data related to the levels of toxic metals in the environment is not
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satisfying especially in view of the setting of future permissible concentrations. However,
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research on heavy metals has met with strongly growing interest in recent years. This is partly a
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consequence of concern for protection of the environment, and is due to increasing awareness of
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the role and effect of metallic elements on living organisms. Trace metals distributions in river
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waters of the world have been reported by Gibbs (1977); Sakai, Kojima & Saito (1986);
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Tanizakl, Shimokawa & Nakamura (1992); Garbarino, Hayes, Roth, Antweiler, Brinton, et al.
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(1995); Abu-Saba & Flegal (1997); Guieu, Martin, Tankéré, Mousty, Trincherini, et al. (1998);
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Aprile, Parente & Bouvy (2003). The necessary presence of metals in trace amounts in all living
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organisms seems to obey to equilibrium laws between the different metals. To understand the
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behavior of heavy metals in an aquatic ecosystem it is necessary to identify the major reservoirs
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of these elements, as well as to determining the rates of elemental turnover among reservoirs.
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The present paper aims (1) to establish the dissolved heavy metal (Fe, Mn, Cu, Pb and Zn)
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concentrations in natural waters to evaluate managing strategies of the Tapacurá River basin used
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to supply urban and rural areas; (2) to estimate significant relationships between trace metals, and
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(3)
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These reports on the distribution of heavy metals at the Tapacurá River can provide valuable
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contribution to the program of sanitation at the Pernambucana Company of Environment.
to provide data-base necessary for developing strategies for pollution control of the basin.
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2. Materials and methods
The Tapacurá River basin is located in the Zona da Mata in Pernambuco State, Northeast
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of Brazil (Fig. 1). The basin is responsible to 9.5% of the water supply to Recife Metropolitan
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Region. Rainfall ranges about 2,000 mm.year-1 in the Zona da Mata (see Fig. 2) and 700
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mm.year-1 in the Agreste. However, many people in Agreste and Zona da Mata have no access to
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potable water. Water depths are generally less than eight meters with lower spring tidal
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(exception of the reservoir), resulting in vertically not well-mixed and lowly dynamic
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environments. There is not efficiently sewage treatment system in the municipalities until today,
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and over 80% of domestic wastewaters are directly discharged into the tributaries without
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treatment. Furthermore, there are agricultural and industrial areas located in or around of the
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basin than contribute with significant amount of untreated effluents to the tributaries in the
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Pombos and Vitória de Santo Antão Cities. Agriculture is the most important economic sector in
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semi-arid and Zona da Mata of the Pernambuco State. In Pombos City, there is improvement of
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cassava starch. The result is the production of manipueira, a solid/liquid waste that has enormous
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impact on the biota due to high toxicity by heavy metals and cyanide acid (Aprile, Parente &
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Bouvy, 2004).
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(Fig 1 and Fig 2)
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Eight sampling sites were established along the river, taking into account the area
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influenced by municipal sewage (zone I), agricultural runoff (zone II) and industrial plant (zone
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III). Sampling locations and description of the sites are shown in Fig. 1 and Table 1, respectively.
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Latitude and longitude at sampling sites were determined with a portable GPS Garmin model
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12X. Temperature ( 0.1 ºC) and pH ( 0.1) of the surface waters were measured with a termistor
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and ohmmeter, respectively. At each site, surface water samples (0-20 cm) were collected
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monthly from March 1997 to December 1998 with a Van-Dor bottle. The samples were then
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refrigerated at 4 ºC before chemical analysis.
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(Table 1)
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The following is a brief description of analytical methods used in this research. Water
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samples for chemical analysis were acidified to pH 2 using HCl (0.1 N) and filtered through a
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GF/C filter to remove suspension material. All the manipulations were conducted inside a clean
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room. Heavy metals (Fe, Mn, Cu, Pb and Zn) in the filtered samples were digested with 5ml each
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of aqua-regia (HNO3+HCl) + HClO4 (Merck) at 200 ºC, made up to 50 ml in a volumetric tube,
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and measured using a Perkin-Elmer AAS Model 3300 equipped with an air–acetylene flame. All
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sampling and analytical determinations followed the suggestions by Loring & Rantala (1992) and
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APHA (1998). Quantification of metals was based upon calibration curves of standard solutions
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of respective metals. These calibration curves were determined several times during the period of
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analysis to check the efficiency of the extraction technique for waters. The detection limits for
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the metallic ions were 0.05 Fe; 0.02 Mn; 0.001 Cu; 0.006 Pb and 0.003 Zn mg.l-1. Values were
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always within the certified range.
The heavy metal contamination levels were compared to the background level in an area
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near (Fig. 1) using the enrichment factor (EF, Aloupi & Angelidis, 2001; Woitke, Wellmitz,
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Helm, Kube, Lepom, et al., 2003; Selvaraj, Ram-Mohan & Szefer, 2004), and the potential
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contamination index (Cp, Davaulter & Rognerud, 2001). Metal levels were normalized to the
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surface waters characteristics with respect to iron. Therefore, EF and Cp were defined as:
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EF = [Metal] surface water/[Fe] surface water / [Metal] background/[Fe] background (equation 1)
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Cp = [Metal] maximum / [Metal] background (equation 2)
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Ratios between dissolved heavy metals were determined to the waters of the Tapacurá
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River. Linear regressions with theirs respectively standardized residual plot were performed on
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the flux data to estimate significant relationships between dissolved metals.
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3. Results and discussion
Dissolved trace metals concentrations in surface waters are summarized in Table 2 (levels
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by sites) and Fig. 3 (total means). The concentrations of dissolve trace metals in Tapacurá River
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basin indicate contamination with regard to anthropogenic metals. The lower distribution of
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dissolved metals in surface water can indicate that sedimentation process affects the suspended
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particle composition. The total dissolved level of Fe were high, the results were characterized by
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Fe concentrations range from 0.30 to 4.22 mg.l-1 and average of 1.35 mg.l-1 (Fig. 3A), exceeding
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those elements in the respective river by an order of magnitude. A strong link between high
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surface soil and water iron levels is consistent with major erosion observed along the riverbanks.
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However, in the Tapacurá River basin was not observed indications of this process. Dissolved
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manganese shows concentrations ranged from 0.02 to 1.09 mg.l-1 (mean = 0.27 mg.l-1, Fig. 3A).
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The highest levels of Fe and Mn were found at sites T4, T5 and T6. Were found cooper values
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ranged from  0.001 (detection limit) to 0.014 mg.l-1, with mean concentration of 0.0058 mg.l-1
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(Fig. 3B), and the lower concentration was observed at site T1 (mean = 0.002 mg.l-1). Pb
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concentrations were low ranged from  0.006 (detection limit) to 0.029 mg.l-1. Lead was below
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detection limit in the sites T1, T5, T6, and T8. The highest concentrations were found at sites T3
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and T4, localized in the Tapacurá River downstream at the spirit company Pitú Ltd and in the
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Natuba River in an agricultural region, respectively. Dissolved zinc ranged from  0.003
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(detection limit) to 0.020 mg.l-1 (mean = 0.009 mg.l-1, see Table 2 and Fig.3B).
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In general, dissolved metals concentration increased between T2 and T5, because of
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municipal sewage from Pombos and Vitória de Santo Antão Cities. Metals are common
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environmental contaminants arising from metal mining and processing as well as from numerous
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other industrial, municipal, and agricultural activities (Foy, Chaney & White, 1978). Local
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geological and anthropogenic influences determine the concentrations of heavy metals in aquatic
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systems (IPCS, 2001). According to National Recommended Water Quality Criteria Correction
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by U.S. Office of Water Drinking Water and Health (US-EPA, 1999), and the limits of safe
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established by CETESB (2001) and Brazilian Health Ministry (2004) to drinking water directive,
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in the Tapacurá River basin was not observed high levels of contamination by heavy metals in
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the water. However, in some samples the concentrations of Fe, Mn and Pb exceeded the limits
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established.
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(Table 2; Fig. 3)
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The degree of anthropogenic impact estimated with enrichment factor (EF) and potential
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contamination indices (Cp) are showed in the Table 3. Based in the classification of Taylor
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(1964), Mn and Pb had the lower enrichments with EF ranged from 0 to 4 (mean 1.3) for Mn,
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and 0 to 1.8 (mean 0.5) for Pb. Enrichment factor is a good tool to distinguish the natural and
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anthropogenic sources (Selvaraj et al., 2004). Five sampling sites with EF <1 for Mn and six sites
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with EF <1 for Pb indicated there is not enrichment by these metals in the water column. In other
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words, these metals are close to background levels. In other hand, copper and zinc had, according
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to Taylor’s classification, enrichment moderate to severe in the sampling sites T2, T7, and T8.
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This result can mean a moderate to high amount of metallic discharge from urban area (zone I)
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and agricultural runoff (zone II). According to the classification of Davaulter & Rognerud
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(2001), 30% of the samples had potential contamination indices ranged from severe to very
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severe contamination by heavy metals in the water column. The heavy metals showing the most
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extensive contamination were Mn ranged from 0.2 to 9.1 and Cu ranged from 1.7 to 4.6. The
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metal that showing the most narrow contamination was Pb with Cp ranged from 0 to 4.8 (mean
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1.6).
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(Table 3)
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In water systems are estimates that amorphous forms of Fe (FeOOH) and Mn (MnOOH)
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are predominantly (Lakind & Stone, 1989). The ratio of FeOOH to MnOOH (Fe/Mn) gives an
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indication of the relative abundance of each sorbent phase. A summary of the ratios between
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trace elements in each sampling site is given in Table 4. The mean ratios of Fe/Mn for the
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Tapacurá River varied from 1:1 (T6) to over 145:1 (T4). Duff (1992) reported that are the ratios
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of 20:1, which represents the ratio in which Fe:Mn is found in aqueous solution due to the
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anthropogenic activities, such as mining. Inter-Riverine variations in Fe and Mn in the Tapacurá
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River may be associated to municipal sewage. Fe and Mn are diagenetically mobile in aqueous
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ecosystems. Reduced Fe and Mn can migrate to the marsh surface via the pore fluids, to be re-
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oxidized and precipitated as (oxy)hydroxides. This process produces higher concentrations of Fe
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and Mn at the surface sediments (Turner & Millward, 2000), and consequently, to reduce the
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levels at the water column. Other significantly ratios obtained were: Fe:Cu ranged from 60:1 (T7)
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to 1039:1 (T1); Fe:Zn ranged from 38:1 (T7 and T8) to 354:1 (T4); Mn:Cu ranged from 4:1 (T4)
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to 189:1 (T6). Were observed relationships very closely too between Cu:Pb ranged from 0.4:1
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(T4) to 1.4:1 (T2) and Cu:Zn ranged from 0.1:1 (T1) to 2:1 (T2). Copper and zinc levels are
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strongly influenced by anthropogenic sources (IPCS, 1998) that may occur to two metals
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simultaneous.
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(Table 4)
Linear regression analysis was applied between dissolved trace metals for the sampling
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sites and the results that gave significant fits (at the 95% confidence interval) are reported in the
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Figure 4. The results showed that Fe and Mn are independent variables, that is, the present of
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dissolved iron does not affect the concentrations of Mn and vice versa (Fig. 4A). Was determined
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a factor F of 0.044 with P = 0.836 for Fe versus Mn. The results of analysis for Zn versus Cu (F
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= 0.368 with P = 0.550, see Fig. 4B) and Zn versus Pb (F = 0.461 with P = 0.505, see Fig. 4C)
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showed that the variables are independents too. Correlations were significant in the sites T3, T4
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and T7 because industrial and agricultural effluents. The results reflecting a well-defined source
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of contamination that are common to some trace metals. A composite plot of all samples
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indicates a general relationship between concentrations of Pb and Cu (F = 7.762 and P = 0.010,
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see Fig. 4D), which is not governed by the abundance, and availability of oxide material, such as
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iron and manganese. The distribution of lead in surface waters of the Tapacurá River is
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characterized by relative anthropogenic mobilization rates.
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(Fig 4)
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The precision and accuracy were very good, with most relative standard deviations and
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relative errors below 10% over the data tested for AAS method. The municipal heavy metal
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loading was small compared to those from industrial and agricultural areas. The metals showed a
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horizontal distribution very heterogeneous. In the Tapacurá River basin, there is not a program to
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remediate the contaminated water by heavy metals. We believe that the first step to apply a
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remedial measure and management strategies is the inspection of the agricultural areas
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surrounding of the basin with control of the use of fertilizers and herbicides.
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4. Conclusions
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According to limits of safe established by US-EPA (1999), CETESB (2001), and
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Brazilian Health Ministry (2004), in the Tapacurá River basin was not observed highly levels of
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contamination by heavy metals in surface waters during this work. However, the sampling sites
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T3, T4, and T7 require more attention in future works. Heavy metals showed a large
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heterogeneous horizontal distribution with hotspots in the industrial and agricultural areas. Data
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analyses by EF and Cp indicated moderate contamination by Cu and Zn in surface waters of the
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basin. Linear regression analysis showed independence between Fe/Mn, Zn/Cu and Zn/Pb, and a
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strong link between Cu and Pb. The results indicated the potential pathways of heavy metals via
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the transport of soil and sediment from the agricultural areas to the reservoir. The results can help
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to develop management strategies for pollution control mainly in the agricultural areas
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surrounding of the basin with severe contamination.
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Acknowledgements
The authors gratefully acknowledge the colleagues at the Pernambucana Company of
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Environment - CPRH and Technological Institute of Pernambuco - ITEP for valuable help with
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the sampling and chemical analyses, and to CNPq for the important financially support (Project
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number # 301746/96.6).
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Figure legends
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Fig. 1 - Location of sampling sites in the Tapacurá River basin, Pernambuco State, Northeastern
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Brazil
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Fig. 2 – Month mean of rainfall in the Tapacurá River basin from 1996 to 1998. Source:
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EMATER, IPA, LAMEPE.
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Fig. 3 - Total mean ± SD of trace metals in waters of the Tapacurá River basin.
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Fig. 4 - Linear regression with its standardized residual plot to A) Fe versus Mn; B) Zn versus
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Cu; C) Zn versus Pb and D) Pb versus Cu.
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