Total, dissolved, and bioavailable metals at Lake Texoma marinas

Total, dissolved, and bioavailable metals at Lake Texoma marinas

Environmental Pollution 122 (2003) 253–259 www.elsevier.com/locate/envpol Total, dissolved, and bioavailable metals at Lake Texoma marinas Youn-Joo A...

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Environmental Pollution 122 (2003) 253–259 www.elsevier.com/locate/envpol

Total, dissolved, and bioavailable metals at Lake Texoma marinas Youn-Joo Ana,*, Donald H. Kampbellb a

Department of Environmental Science and Engineering, Ewha Womans University, 11-1 Daehyun-dong, Seodaemun-gu, Seoul, 120-750, South Korea b US Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, PO Box 1198, Ada, OK 74820, USA Received 23 February 2002; accepted 5 July 2002

‘‘Capsule’’: Boating and boat activities may be a potential source of metal pollution at lake marinas. Abstract Dissolved metals in water and total metals in sediments were measured at marina areas in Lake Texoma during June 1999 to October 2001, and October 2001, respectively. The metals most often found in the highest concentrations in marina water were Na and Ca, followed by Mg and K. Elevated Cu levels detected in lake water appeared to be associated with Cu based anti-fouling paint used on boats. Metal concentrations in sediment were much higher than in water. The relative order of the concentration in sediment was Ca > Al > Fe > K > Mg > Na. Elevated Cu level at specific locations appeared to be associated with local anthropogenic sources of boat repair activities. There were positive relationships between several metal elements in water and sediment. Metals in 16 sediments from lake marinas were extracted with a weak electrolyte solution [0.1 M Ca(NO3)2] to predict the bioavailability of metals. Among the five heavy metals studied (As, Cd, Cr, Cu and Zn), Cu was the most bioavailable in Lake Texoma marinas. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Metal; Bioavailability; Sediment; Copper; Marina

1. Introduction Metals enter the aquatic environment from a variety of sources. Although most metals are naturally occurring through the biogeochemical cycle (Garrett, 2000), they may also be added to environments through anthropogenic sources, including industrial and domestic effluents, urban storm water runoff, landfill leachate, atmospheric sources (Forstner and Wittmann, 1979), and boating activities (Thomson et al., 1984). Sediments are the sink of metals in freshwater and marine environments (Arjonilla et al., 1994; Louma, 1989; Weimin et al., 1994). Total concentrations of most metals in sediments are several orders of magnitude higher than aqueous concentrations (Louma, 1989). However, total metals concentrations in sediments are not necessarily related to the biologically available metal concentrations. Many chemical extraction procedures have been proposed to estimate the concentration * Corresponding author. Tel.: +82-2-3277-4238; fax: +82-2-32773275. E-mail address: [email protected] (Y.-J. An).

of metals in soils or sediments, which may be directly or indirectly available to organisms. Other studies report a good correlation between extractable metal concentrations and metal content in some biota. (Conder et al., 2001; Pierzynski and Schwab, 1993; Weimin et al., 1994). Extractants employed most often in studies of metal bioavailability in soils or sediments are weak acids (Pierzynski and Schwab, 1993; Weimin et al., 1994) and weak electrolytes (Basta and Gradwohl, 2000; Conder and Lanno, 2000; Conder et al., 2001). A suite of metals was monitored in five marinas at Lake Texoma. The lake (93,000 surface acres) is a manmade impoundment of the Red and Washita rivers on the border of Oklahoma and Texas. It is an important multi-use reservoir and the focus of the recreation, real estate, and farming industries in the region. Boating activities were reported in Lake Texoma marinas (An et al., 2000; An et al., 2001; An et al., 2002) and boatrepair activities may cause the contamination at marinas that lead to metal pollution. The occurrence and concentrations of a suite of metals (26 elements) in Lake Texoma is reported. Dissolved metals in lake water were monitored from June

0269-7491/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00291-9

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1999 through October 2001 and the total metals in lake sediments were measured in October of 2001. We predicted the bioavailability of metals by a chemical extraction method because bioavailability is related to the solubility of exchangeable metals. Cu, Cr, Cd, As, and Zn were chosen as the metals of interest in the chemical extraction because they are toxic to many organisms.

2. Materials and methods 2.1. Lake water sampling and metal analysis A map of Lake Texoma showing sampling locations is shown in Fig. 1. The study area is located on the border of Oklahoma and Texas. Lake water was collected at 15 locations in five different marinas from June 1999 to October 2001. Water samples were collected through 14 inch (6 mm) diameter polyethylene tubing connected to a peristaltic pump. New tubing was used at each sampling location. Samples for metal analysis were filtered and collected in acid-washed polyethylene bottles and preserved with nitric acid to pH < 2. Ten percent or more of the samples were duplicated as a quality assurance requirement. Metal scans in lake water were performed by inductively coupled plasma atomic emission spectroscopy (Optima 3300 DV ICP, Perkin-Elmer Instruments, Shelton, CT) as described in

EPA Method 6010A. The metals scan analyzed 26 elements as listed in Table 1. Detection limits ranged from 0.001 mg l 1 for Mg, Be and Sr to 0.479 mg l 1 for Na. 2.2. Sediment sampling and metal analysis Sediment samples were collected at eight locations in five different marinas in October 2001. Sediment samples were taken using a modified Peterson dredge sampler (Code 1097, LaMotte Company, Chestertown, MA) that was rinsed between sample collection with lake water. Surface sediment (approximated 0–1 cm depth) was collected and placed into polyethylene bottles. Sediment temperature, pH and redox potential (Eh) were measured in situ from the boat using a stainless steel probe meter (Model IQ150-07, IQ Scientific Instruments, San Diego, CA). All water and sediment samples collected were stored in an insulated cooler containing blue ice and delivered the same day to the analytical laboratory. Total concentration of metals in sediment was determined by microwave assisted acid digestion based on a modification of EPA Method 3051. Ten percent nitric acid was added to 0.25 g of dried sediment sample in a digestion vessel and heated in a microwave unit prior to analysis. Elemental analyses in digests were performed using the ICP. Percent organic Table 1 Detectable dissolved metal concentrations (mg l 1) in marina waters, Lake Texoma, June 1999–October 2001 Metal

MeanSD

(range) a

% Occurrence b

Na Ca Mg K Sr Ba B Fe Al Zn As Tl Sb Se Cu Cd Ti Mn Ni Mo Cr Be Ag V Co Pb

204 65 102 23 3810 5.3420.799 1.3010.312 0.2470.062 0.2250.049 0.1190.093 0.0920.096 0.0590.036 <0.033 0.0330.006 0.0240.009 0.0240.005 0.0240.020 0.0200.061 0.0110.005 0.0070.018 0.0050.003 0.0050.002 0.0040.002 0.0040.007 0.0030.001 0.0030.002 <0.002 <0.015

(46–365) (59–143) (18–51) (2.793–6.883) (0.559–1.899) (0.139–0.533) (0.116–0.361) (< 0.035–0.430) (< 0.026–0.622) (< 0.012–0.246) (< 0.033–0.033) (< 0.027–0.047) (< 0.017–0.047) (< 0.030–0.035) (< 0.011–0.104) (< 0.002–0.249) (< 0.003–0.024) (< 0.001–0.152) (< 0.001–0.012) (< 0.003–0.011) (< 0.002–0.008) (< 0.001–0.020) (< 0.002–0.004) (< 0.002–0.019)

100.0 100.0 100.0 100.0 100.0 100.0 100.0 28.3 46.9 87.9 0.3 18.3 7.2 4.5 7.9 5.5 6.6 52.8 4.1 9.3 1.4 14.1 9.7 32.8 0.0 0.0

a

Fig. 1. Lake Texoma showing the sampling locations.

b

Number of water samples is 290. At given detection limit in this study

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matter content of the sediment was measured using an organic matter soil test kit (Model ST-OR 5020, LaMotte Company, Chestertown, MD, USA). The acid-dichromate soil solution was titrated with 0.4 N ferrous ammonium sulfate until color changed from dark brown to a deep green endpoint. Quality assurance measures performed on water and sediment samples included analytical duplicates, known analytical quality controls (AQCs) and trip blanks. 2.3. Metal extraction using calcium nitrate General procedures for chemical extraction were adapted from Conder et al. (2001) and Basta and Gradwohl (2000). The extraction was done on three replicates at an ambient laboratory temperature of 24 1  C. Sediment was dried for 24 h at an oven temperature of 105  C. One gram as dry weight of sediment was placed in 50-ml polycarbonate centrifuge tubes. Then 20 ml of 0.1 M Ca(NO3)2 solution was added. Samples were shaken on a reciprocal shaker for 16 h and centrifuged (Beckman GS-6KR Centrifuge) at 1500 rpm for 15 min to separate the sediments from the aqueous phase. The supernatant was then filtered using a 0.45 mm membrane filter and acidified with 0.5 ml concentrated trace metal-grade HNO3. The metal concentrations in extractants were quantified by inductively coupled plasma mass spectrometer (ICPMS; Model PQ Excell, Thermo Elemental, Franklin, MA).

3. Results and discussion 3.1. Dissolved metals in lake water The detectable dissolved metal analytes at marina waters in Lake Texoma are listed in Table 1. The metals most often found in the highest concentrations in marina waters were Na and Ca, followed by Mg and K. Most of these base cations are provided by the geochemical weathering processes and ion exchange reactions between the soils and bedrocks (Papineau and Haemmerli, 1992). Mean Na, Ca, Mg, and K concentrations in all marinas were 204 65, 102 23, 38 10, and 5.34  0.799 mg l, 1 respectively. The high Na concentration in Lake Texoma is a result of marine evaporates in the upper Red River Basin. In the upper basin tributaries there are numerous salt seeps and springs that result in salt loading into the Red River and ultimately the Lake. Sr, Ba, and B were also found at low concentrations in all samples as shown in Table 1. Detected metals generally had fairly uniform distribution over the marinas and there was very little seasonal variability. Zn and Mn were widely distributed in 87.9 and 52.8%, respectively, of samples with very low

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concentrations that would be below a toxic level. Other toxic metals such as As and Pb were present, but below the analytical detection limit during this study. Copper was detected in 7.9% of marina water samples. Samples collected at Lake Texoma marinas had < 0.011–0.104 mg Cu l 1 with the mean  SD of 0.024  0.020 mg l 1. Dissolved Cu levels detected in marina waters exceeded the normal Cu levels in uncontaminated freshwaters, which usually range from 0.0005 to 0.001 mg l 1 (Moore and Ramamoorthy, 1984). The single largest source of Cu at marinas may be Cu-based paints of boat. Copper was the active anti-fouling agent, and it was used historically as a component of paint material on the bottom of boats. Although Cu-based antifouling paint has been phased out, recreational boats with Cu-based bottom paints still exist at marinas in Lake Texoma. Copper can be continuously released into the water when the boat bottoms contact the water. In addition, we investigated the correlation between metal elements that are always present in lake water. Pearson product moment correlation coefficient (r) ranged from 0.968 to 0.776. Calcium had a strong positive correlation with Mg (r=0.946) and Sr (r=0.889) as shown in Fig. 2, where the correlation coefficients between other metals were also listed. 3.2. Total metals in sediments The average concentration of the total metal analytes in lake sediments is listed in Table 2. Metal concentration in sediment was much higher than in water, as previously documented elsewhere (Louma, 1989). Among the 25 metals scanned, 18 metal elements, including Zn, Cu, Cr, Pb, and Cd, were usually present in sediments. Detectable As was found in 87.5% of samples. The metals most often found in the highest concentrations in sediments were Ca and Al, followed by Fe, K, and Mg. There is a difference in terms of the relative order of the concentration rankings in lake water. Copper concentration in the 16 sediment samples analyzed ranged from 9 to 136 mg kg 1 (Table 2). Elevated Cu levels (136 mg Cu kg 1) at a specific sampling station appeared to be associated with local anthropogenic sources. This station was located next to a boat repair shop. Boat repair activities occurring near the sampling station appeared to be the main source of Cu contamination in marina sediments. When the boat bottoms need to be repainted, old Cu-based paints are stripped off and discarded into the lake, which accumulate at the lake bottom. Since sediments used in this study were collected from different field sites, their physicochemical properties (e.g. organic matter content) varied which also affects the metal concentration in sediments. When percent organic matter (as listed in Table 3) was related with the metal concentration in sediment, Copper had the lowest correlation with per-

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Fig. 2. Correlation between commonly found metals including Ca, Mg, and Sr at lake water collected from June 1999 to October 2001, Lake Texoma. Pearson product–moment correlation coefficient values (r) between other metals were listed. Number of water samples was 290. Table 2 Total metal concentrations (mg kg 1 dry wt.) in marina sediments, Lake Texoma, September–October 2001 Metal

MeanSD

(range)a

% Occurrenceb

Ca Al Fe K Mg Na Mn Ti Sr Ba Zn V Cu Cr Ni Pb Co Cd As Be Tl Ag B Mo Se

5681153142 3109514638 193937835 60892954 51282727 713 360 377 161 231 67 183 116 163 69 89 53 59 24 38 34 30 13 17 8 10 3 9 3 2 3 11 2 1 0.8 3 0.4

(5385–160664) (9445–53285) (7989–32046) (1921–10914) (1216–9692) (242–1538) (145–643) (123–361) (36–350) (68–272) (33–242) (24–99) (9–136) (12–51) (6–31) (5–15) (4–14) (1–3) (6–16) (1–2) (1–6) 0 0 0 0

100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 87.5 75 37.5

a b

Number of sediment samples is 16. At given detection limit in this study

cent organic matter compared to the other metals studies. The r-values of exponential fit for As, Cd, Cr, Zn, and Cu were 0.66, 0.44, 0.52, 0.79, and 0.0089, respectively. This indicated that Cu contamination was associated with anthropogenic sources in marina sediments. Correlation for metal elements in sediment samples was also determined. Among the toxic heavy metals analyzed, Cd was had a strong positive correlation with Cr (r=0.981), Ni (r=0.984), and Pb (r=0.831) as shown in Fig. 3. The r-values between Cr and Ni, and Cr and Pb are 0.995 and 0.760, respectively. Al, Cd, Ni, and V have positive relationships with many other metals. Copper had low correlations with other heavy metal elements presumably due to the incorporation of anthropogenic sources. 3.3. Total/extractable (bioavailable) metals The total concentrations and Ca(NO3)2-extractable concentrations of five selected metal elements (As, Cd, Cr, Cu, and Zn) in test sediments are listed in Table 3. The total metal concentrations in sediments had a wide range of values as shown in Table 3 and Fig. 4 A. Among the five elements analyzed in sediments, Zn was present in the highest concentrations, followed by Cu (or Cr), As, and Cd in this order. The median concentrations of Zn, Cu, Cr, As, and Cd were 78.6, 28.4, 28.1, 11.4, and 2.2 mg kg 1, respectively.

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Fig. 3. Correlation between selected heavy metals at lake sediment collected in Fall 2001, Lake Texoma. Pearson product–moment correlation coefficient values (r) between other metals were listed. Number of water samples was 16.

Table 3 Total metal concentrations and Ca(NO3)2-extractable metal concentrations in test sediments (mg kg Temp ( F)

pH

Eh

OM (%)

As

Cd TM

EM

%

TM

EM

%

TM

EM

%

TM

EM

%

2.96 3.26 1.58 2.20 2.98 0.86 1.09 1.68

0.009 0.046 0.005 0.016 0.018 0.020 0.016 0.004

0.30 1.41 0.30 0.75 0.61 2.33 1.44 0.24

39.88 48.31 21.78 29.25 46.27 12.02 18.03 25.20

0.156 0.160 0.077 0.051 0.530 0.232 0.238 0.039

0.39 0.33 0.35 0.18 1.14 1.93 1.32 0.15

9.94 16.35 18.52 83.91 30.82 37.38 58.15 13.23

0.629 0.992 1.135 1.657 1.240 1.590 1.194 1.102

6.33 6.06 6.13 1.97 4.02 4.25 2.05 8.33

60.45 79.51 50.98 157.43 111.91 58.35 53.50 91.16

0.109 0.347 0.075 4.817 0.972 0.400 20.390 0.283

0.18 0.44 0.15 3.06 0.87 0.68 38.11 0.31

2.72 3.40 2.36 2.19 2.90 1.33 1.17 1.89

0.004 < DL < DL < DL < DL 0.006 0.005 < DL

0.17 NAe NA NA NA 0.44 0.43 NA

37.89 50.63 31.51 26.47 41.76 13.88 14.61 27.59

< DL < DL < DL < DL < DL < DL < DL < DL

NA NA NA NA NA NA NA NA

9.35 17.87 26.83 136.07 29.31 51.51 53.90 13.65

0.322 0.323 0.360 0.340 0.377 0.368 0.390 0.340

3.44 1.81 1.34 0.25 1.29 0.71 0.72 2.49

63.81 92.90 77.61 241.98 125.57 32.78 35.89 92.83

< DL < DL 0.248 1.930 0.315 < DL 0.300 0.044

NA NA 0.32 0.80 0.25 NA 0.84 0.05

17.0 2.0 – – – – – 17.3

2.77 3.74 3.85 4.60 4.90 2.45 – 4.32

11.76 13.26 8.41 13.92 13.88 < DLd 5.93 10.96

0.117 0.168 0.183 0.222 0.240 0.185 0.175 0.165

1.00 1.27 2.18 1.59 1.73

2nd EPA-01 EPA-03 EPA-06 EPA-08 EPA-09 EPA-11 EPA-12 EPA-15

64.0 65.6 67.2 65.4 66.0 65.8 63.8 64.4

7.85 7.56 7.31 6.91 7.25 6.97 6.93 7.65

51.6 33.5 18.9 3.8 14.3 0.1 0.4 37.4

2.69 2.57 2.92 4.09 4.45 1.14 1.32 3.97

10.60 12.60 11.00 15.78 13.68 < DL 5.64 9.80

0.060 0.078 0.104 0.107 0.107 0.071 0.074 0.089

0.57 0.62 0.95 0.68 0.78

d e

Zn

%c

6.70 6.92 – – – – – 7.27

c

Cu

EMb

77.1 74.4 – – – – – 76.1

b

dry wt.)

TMa 1st EPA-01 EPA-03 EPA-06 EPA-08 EPA-09 EPA-11 EPA-12 EPA-15

a

Cr

1

Total metal Extractable metal, values are means of triplicate. Extractable/Total (percentage) Below detection limit Not available

2.95 1.50

1.31 0.91

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Fig. 4. Total metal concentrations, extractable metal concentrations, and recovery rate (%) of As, Cd, Cr, Cu, and Zn in lake sediments on Lake Texoma.

Fig. 4B shows Ca(NO3)2-extractable metal concentrations for five metal elements. Copper (median of 0.51 mg kg 1) was highest, followed by Zn (0.32 mg kg 1), Cr (0.16 mg kg 1), As (0.11 mg kg 1), and Cd (0.01 mg kg 1). The order of the extractable metal concentration rankings was not the same as the order of the total metal concentration rankings. There was no direct relationship between total and bioavailable metal concentrations. Ca(NO3)2-extractable metal recoveries were within approximately 5% of the total metal concentrations, as shown in Table 3 and Fig. 4C. Copper had the greatest extraction efficiency and Cd the least. Since metal bioavailability is related to metal solubility, extractable metal concentrations may correspond to the bioavailable metal concentrations. Results from the extraction experiments indicated that Cu should be the most bioavailable metal compared to the other metals studied. In addition, overall extraction efficiencies for the first set of sediments were higher than the second set of sediments, as shown in Table 3. This may have been due to the pH effect. Sediment pH values were more acidic in the first set of sediments for those that were measured. The lower pH caused a higher solubilization of metals from solid phases.

4. Conclusions Dissolved metals in lake water and total metals in lake sediments were monitored in marina areas at Lake

Texoma during June 1999–October 2001, and October 2001, respectively. The metallic elements found in the highest concentrations in marina waters were Na and Ca, followed by Mg and K. They showed uniform distribution over all marinas with very little seasonal variability. Dissolved Cu levels detected in marina waters occasionally exceeded the background Cu levels, which indicated that the single largest source of Cu at marinas may be Cu-based anti-fouling boat paints. The metals most often found in the highest concentrations in sediments were Ca and Al, followed by Fe, K, and Mg. There was a difference in the relative order of the concentration rankings in lake water. Elevated Cu levels at specific sampling stations appeared to be associated with local anthropogenic sources and boat repairing activities. Among the five heavy metals (As, Cd, Cr, Cu and Zn), Cu was the most bioavailable in Lake Texoma marinas according to the extraction technique used.

Acknowledgements The US Environmental Protection Agency through its Office of Research and Development funded and managed the research described here through in-house efforts. It has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. This research was supported in part by an appointment

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to the Postgraduate Research Participation Program at the National Risk Management Research Laboratory administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and the US Environmental Protection Agency. We thank Mike Cook at US EPA, Ada, OK for his assistance with sampling. Jason Masoner of US Geological Survey assisted with map preparation. We thank Tony Clyde of US Army Corps of Engineers for providing background information regarding Lake Texoma. The analytical support provided by ManTech Environmental Research Services Corp. was appreciated.

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