Mean Concentrations Of Contaminants Research Articles

Contaminant Concentrations and Reproductive Rate of Lake Superior Bald Eagles, 1989–2001

We investigated the trend in contaminant concentrations in Lake Superior bald eagles ( Haliaeetus leucocephalus) from 1989–2001, and examined the relationship of contaminant concentrations to eagle reproductive rate during that time. Concentrations of dichloro-diphenyl-dichloroethylene (DDE) and total polychlorinated biphenyls (PCBs) in nestling blood plasma samples decreased significantly from 1989-2001 (p = 0.007 for DDE, p = 0.004 for total PCBs). Mean contaminant concentrations in eaglet plasma, 21.7 μg/kg DDE (n=51) and 86.7 μg/kg total PCBs (n = 54), were near or below the estimated threshold levels for impairment of reproduction as determined in other studies. A preliminary assessment of polybrominated diphenyl ether (PBDE) concentrations indicated a mean of 7.9 μg/kg total PBDEs in Lake Superior eaglet plasma (n = 5). The number of occupied bald eagle nests along the Wisconsin shore of Lake Superior increased from 15 to 24 per year, between 1989 and 2001 (p < 0.001, r 2 = 0.70, n = 13 years). Eagle reproductive rate did not increase or decrease significantly between 1989 and 2001 (p = 0.530, r 2 = 0.037, n = 13 years, mean productivity = 0.96 young per occupied nest). The lack of correlation between reproductive rate and contaminant concentrations, as well as the comparison of contaminant concentrations to the estimated thresholds for impairment of reproduction, suggest that DDE and PCBs no longer limit the reproductive rate of the Lake Superior eagle population in Wisconsin.

Contaminants Associated with Suspended Sediments in Lakes Erie and Ontario, 1997–2000

Sediment traps were installed at individual index stations in the western basin of Lake Erie and the Mississauga (central) basin of Lake Ontario, and refurbished seasonally during the period 1997–2000. In Lake Ontario, sediment down flux rates and corresponding contaminant down flux rates were highest in winter and increased with depth due to the influence of resuspended bottom sediments. Sediment down flux rates in western Lake Erie (22 to 160 g m −2 d −1) were far greater than in Lake Ontario (0.19–3.0 g m −2 d −1). Suspended material in western Lake Erie was characterized as predominately resuspended bottom sediments; down flux rates were roughly 5- to 10-fold higher in spring and fall, compared to summer. Suspended sediment concentrations of PCBs and other organochlorine contaminants, represented by both annual means and individual seasonal values, were higher in Lake Ontario throughout the duration of the study, compared to Lake Erie. The mean annual concentration of PCBs in suspended sediments over the period 1997–2000 was 330 ng/g in western Lake Erie and 530 ng/g in Lake Ontario. Based on a comparison with historical data from Lake Ontario, mean contaminant concentrations over the period 1997–2000 for PCBs, hexachlorobenzene, and mirex corresponded to decreases of 38%, 74%, and 40%, respectively, since the mid-1980s. Corresponding down flux rates for PCBs, hexachlorobenzene, and mirex decreased by approximately 70%, 90%, and 80%, respectively, since the 1980s.

Comparison of nutrient and contaminant fluxes in two areas with different hydrological regimes (Empordà Wetlands, NE Spain)

Nutrient (N and P), heavy metal (Ni, Cd, Cr, Cu and Pb) and pesticide (DDT, DDD, DDE, lindane, aldrin, endrin, dieldrin, permethrin, atrazine and simazine) concentrations in water and sediment were analysed in the Empordà Wetlands, a Mediterranean wetland area in NE Spain. Mean nutrient and contaminant concentrations and input and output loads via tributaries were compared in two marshes with different water turnover: a freshwater marsh (FWM), with a high water turnover rate due to continuous surface water inputs and outputs, and a brackish water marsh (BWM), with lower turnover and no continuous surface output, where water remains confined during dry periods. Mean concentrations of most heavy metals exceeded the maximum permissible concentration (MPC) in BWM, whilst only some pesticides reached MPC in FWM. The confined waters of BWM showed higher sensitivity to contaminant input loadings than FWM due to the lack of continuous water outputs. Non-point source pollution inputs during runoff (mainly in FWM) and concentration during confinement (mainly in BWM) showed as the main environmental problems related to nutrients and contaminants in these ecosystems. Thus, the importance of confinement and its effect on pollutant concentrations must be borne in mind to achieve correct management of Mediterranean wetlands.

Association of Low Reproductive Rates and High Contaminant Levels in Bald Eagles on Green Bay, Lake Michigan

Bald eagles ( Haliaeetus leucocephalus) nesting on the shores of Green Bay, Lake Michigan, had reproductive rates significantly lower than those of neighboring eagles nesting in inland Wisconsin (0.55 vs. 1.1 young per occupied territory). This study investigated effects of two factors which have depressed eagle reproductive rates at other locations: exposure to organochlorine contaminants and low food availability. Levels of dichloro-diphenyl-dichloroethylene (DDE) and total polychlorinated biphenyls (PCBs) in addled eggs and eaglet blood samples from Lake Michigan and inland Wisconsin reference sites were measured. An index to food availability, the food delivery rates by parent eagles to nestlings, and other behavioral indices that have been associated with food availability, were measured and compared to inland reference data. Mean contaminant concentrations in addled eggs from Green Bay were 8.3 μg/g wet weight DDE and 31.3 μg/g wet weight total PCBs (1987 to 1996, n = 9). Mean concentrations in nestling blood plasma were 53 μg/kg wet weight DDE and 207 μg/kg wet weight total PCBs (1987 to 1995, n = 8). Indices of food availability were generally normal in comparison to inland reference data. Mean food delivery rate to the nestlings was 2.55 items per nestling per day (n = 7 nests). None of the behavioral measures differed significantly from inland reference values, suggesting that prey was adequate. It was concluded that organochlorine contaminants caused all or most of the depression in reproductive rates of Green Bay bald eagles.

Distribution of Toxic Organic Contaminants in Water and Sediments in the Detroit River

Contamination of sediments in the Detroit River has been shown to have impacts upon the health of benthic fish in direct contact with the sediments. It was hypothesized that hydrophobic contaminants partition from sediments into the aqueous phase in the Detroit River, subsequently bioaccumulating in fish and causing toxic effects. In order to assess the distribution of organic contaminants dissolved in water relative to contamination in the sediments, semi-permeable membrane devices (SPMDs) were deployed and sediments were collected from five sites in the Detroit River and from one site in western Lake Erie. Sample extracts were analyzed for concentrations of PAHs, PCBs, and selected organochlorine insecticides (DDT compounds, chlordane compounds, and HCH isomers). Both SPMD and sediment extracts were tested for lethality in an early life-stage mortality assay with Japanese medaka (Oryzias latipes). The mean concentrations of PCBs, PAHs, and DDT compounds in sediments and SPMDs were highest at three sites in industrialized regions of the Detroit River; at Zug Island near the outflow of the Rouge River, at Elizabeth Park in the Trenton Channel, and at Celeron Island downstream of the Trenton Channel. The mean concentrations of contaminants in sediments and in SPMDs from the various sites were highly correlated, indicating that contaminants in the Detroit River are partitioning between sediments and the dissolved phase of the water column. The lethal concentrations (LC50s) of extracts to early life stages of medaka were highly correlated with the concentrations of PAHs in the samples. This study illustrates the value of using SPMDs as devices for monitoring aquatic contamination, and the ease with which in vivo toxicity tests can be used to screen SPMD extracts prior to analytical studies.

Suspended Solids, Trace Metal and PAH Concentrations and Loadings from Coal Pile Runoff to Hamilton Harbour, Ontario

The Kenilworth boatslip has been identified as a “hotspot” within the Hamilton Harbour Area of Concern because of highly contaminated bottom sediments. There are a variety of sources potentially contributing to this sediment contamination, including runoff from industrial coal piles. The objective of this study was to assess the contaminant characteristics associated with coal pile runoff and identify potential impacts that the runoff might have on sediment quality. Flow-proportioned samples of the coal pile runoff were collected from June through October, 1996 and analyzed for total suspended solids, trace metals, and PAHs. Loadings for selected metals and PAHs were determined using a volumetric approach that considered mean contaminant concentrations and measured or modeled flow volumes. The suspended solids and total trace metal concentrations (Al, Fe, Mn, V, Cd, Cr, Cu, Pb, Zn) often exceeded Canadian Water Quality Guidelines for the Protection of Aquatic Life. Concentrations of fluoranthene, phenanthrene, pyrene, and chrysene exceeded the provincial “Severe Effect Level” for sediment, although the bioavailability of these PAHs should be examined more thoroughly. In general, suspended solids concentration and coal pile volume were significantly correlated with the concentrations of trace metals in the coal pile runoff, while hydrometeorologic variables such as rainfall intensity, rainfall depth, and runoff volume were weakly correlated with metals concentrations. The ratios of various PAHs to naphthalene suggested that coal pile runoff could be an important contributing source to bed sediment contamination. Given the concentrations and loadings of solids, metals, and PAHs and the relatively low volume of runoff, it would be prudent to treat the coal pile discharge as a remedial action for the harbor.

Levels of selected chlorinated hydrocarbons in edible fish tissues from polluted areas in the Georges/Cooks Rivers and Sydney Harbour, New South Wales, Australia

During the period from February to March 1995 edible fish were sampled from various locations known to be polluted with chlorinated hydrocarbons. Samples were collected from five locations in the Georges/Cooks Rivers and four locations in Sydney Harbour. The muscle tissue of a range of fish species from each location was analysed for selected chlorinated hydrocarbons (i.e. polychlorinated biphenyls (PCBs) and organochlorine pesticides). The Georges/Cooks Rivers locations were in Prospect Creek. Chipping Norton, Saltpan Creek, Cooks River and Alexandra Canal. The Sydney Harbour locations were in Duck River, Parramatta River, Homebush Bay, Iron Cove and Long Bay. Chlorinated hydrocarbons were found in the tissues of fish sampled from every location. The major contaminants were PCBs and the Group A organochlorine pesticides, which include chlordane, dieldrin and heptachlor epoxide. At some locations, the mean concentration of one or more of these contaminants was significantly greater than the National Food Authority Maximum Residue Limit (MRL) in certain fish species. DDT and/or its metabolites were not found above their MRL at any location, but were detected at all locations. The highest mean concentrations of PCBs were detected in fish from Prospect Creek, Chipping Norton, Duck River, Alexandra Canal and Homebush Bay. The highest mean concentrations of Group A pesticides, particularly chlordane and dieldrin, were detected in fish from Alexandra Canal, Cooks River and Duck River. The highest mean concentrations of DDT were found in the tissues of fish from Prospect Creek. The fish species which accumulated contaminants to concentrations exceeding the relevant MRLs were yellow-fin bream (Alexandra Canal, Cooks River, Saltpan Creek, Duck River, Homebush Bay and Parramatta River), sea mullet (Prospect Creek, Chipping Norton, Cooks River, Alexandra Canal, Saltpan Creek, Duck River, Homebush Bay and Iron Cove), pink-eye mullet (Prospect Creek) and silver biddy (Prospect Creek, Chipping Norton, Alexandra Canal and Iron Cove), whereas the luderick, fan-tail mullet and sand whiting had mean concentrations of contaminants below the relevant MRLs.

Inference About the Mean in Log‐Regression with Environmental Applications

A standard practice in the analysis of contaminant concentrations is to conduct the statistical analyses in the logarithmic scale. This practice finds support in the empirical fact that many contaminant concentration data appear to be lognormally distributed. However, regulatory rules such as those followed by the US Environmental Protection Agency require that risks should be characterized in terms of the mean contaminant concentration. Furthermore, recent studies suggest that the lognormal distribution may exhibit heavier tails than required in practice for adequate description of contaminant concentrations. Most of the studies on contaminant concentration data deal with one-sample or several sample problems. In this article, we examine the above issues in situations where the contaminant concentration data are supplemented with measurements on concomitant variables such as environmental factors. We use log-regression with arbitrary error distributions as the underlying models and develop estimation and inferential methods for the moments of the contaminant concentration at a new set of experimental conditions. We focus on maximum likelihood, bias correction, minimum variance unbiased estimation, nonparametric estimation and confidence intervals. To illustrate the methods we provide a detailed analysis of data on calcium and magnesium concentrations in samples of water from the Fraser River, British Columbia, Canada, as well as some comparisons using a small sample of the year production and price of ground nuts and cotton in Israel. © 1997 John Wiley & Sons, Ltd.

Inference About the Mean in Log-Regression with Environmental Applications

A standard practice in the analysis of contaminant concentrations is to conduct the statistical analyses in the logarithmic scale. This practice finds support in the empirical fact that many contaminant concentration data appear to be lognormally distributed. However, regulatory rules such as those followed by the US Environmental Protection Agency require that risks should be characterized in terms of the mean contaminant concentration. Furthermore, recent studies suggest that the lognormal distribution may exhibit heavier tails than required in practice for adequate description of contaminant concentrations. Most of the studies on contaminant concentration data deal with one-sample or several sample problems. In this article, we examine the above issues in situations where the contaminant concentration data are supplemented with measurements on concomitant variables such as environmental factors. We use log-regression with arbitrary error distributions as the underlying models and develop estimation and inferential methods for the moments of the contaminant concentration at a new set of experimental conditions. We focus on maximum likelihood, bias correction, minimum variance unbiased estimation, nonparametric estimation and confidence intervals. To illustrate the methods we provide a detailed analysis of data on calcium and magnesium concentrations in samples of water from the Fraser River, British Columbia, Canada, as well as some comparisons using a small sample of the year production and price of ground nuts and cotton in Israel.

Contaminant Trends in Lake Trout and Walleye From the Laurentian Great Lakes

Trends in PCBs, DDT, and other contaminants have been monitored in Great Lakes lake trout and walleye since the 1970s using composite samples of whole fish. Dramatic declines have been observed in concentrations of PCB, ΣDDT, dieldrin, and oxychlordane, with declines initially following first order loss kinetics. Mean PCB concentrations in Lake Michigan lake trout increased from 13 μg/g in 1972 to 23 μg/g in 1974, then declined to 2.6 μg/g by 1986. Between 1986 and 1992 there was little change in concentration, with 3.5 μg/g observed in 1992. ΣDDT in Lake Michigan trout followed a similar trend, decreasing from 19.2 μg/g in 1970 to 1.1 μg/g in 1986, and 1.2 μg/g in 1992. Similar trends were observed for PCBs and ΣDDT in lake trout from Lakes Superior, Huron and Ontario. Concentrations of both PCB and ΣDDT in Lake Erie walleye declined between 1977 and 1982, after which concentrations were relatively constant through 1990. When originally implemented it was assumed that trends in the mean contaminant concentrations in open-lake fish would serve as cost effective surrogates to trends in the water column. While water column data are still extremely limited it appears that for PCBs in lakes Michigan and Superior, trends in lake trout do reasonably mimic those in the water column over the long term. Hypotheses to explain the trends in contaminant concentrations are briefly reviewed. The original first order loss kinetics used to describe the initial decline do not explain the more recent leveling off of contaminant concentrations. Recent theories have examined the possibilities of multiple contaminant pools. We suggest another hypothesis, that changes in the food web may have resulted in increased bioaccumulation. However, a preliminary exploration of this hypothesis using a change point analysis was inconclusive.

Forecasting scale-dependent dispersion from spills in heterogeneous aquifers

Existing theories of flow and contaminant transport in aquifers are either based on Monte Carlo simulations or small perturbation solutions of the governing stochastic partial differential equations, which limit the applications to cases of small variances in the physical parameters. In this article scale-dependent models to predict mean contaminant concentration from point sources (well injection), and non-point sources (ground surface spills) in heterogeneous aquifers are developed and tested. A general analytic technique, the Neumann expansion, is used in the solution of the equations. This method does not require the assumptions of small perturbation, logarithmic transformations, or a specific probability law in the random quantities. In addition, aquifer parameters such as the mean pore velocity are functionally defined in terms of the underlying groundwater flow problem, and field-measurable aquifer hydrogeologic properties such as mean transmissivity, mean hydraulic gradient, mean porosity and aquifer thickness. Comparison with theoretical models, and verification with field tracer tests at the Borden aquifer indicated that the proposed models reproduced the enhanced longitudinal dispersion as a function of distance reported in the literature.

Procedures for Formation of Composite Samples from Segmented Populations

We used a simulation approach to investigate the implication of two methods of forming composite samples to characterize segmented populations. We illustrate the case where the weight of individual segments varies randomly, a situation common with fish samples. Composite samples from segments such as whole fish or muscle tissue should be formed by homogenizing each segment separately and combining equalsized portions randomly drawn from each homogenate. This approach permits unbiased estimation of the mean concentration per fish. Estimates of mean contaminant concentration varied little with variation in the number of composite samples analyzed or with composite size (number of segments in a composite sample). However, for a fixed number of composite samples, the precision of the variance estimate increased as composite size increased. In addition, for a fixed number of composites, the estimate of the variance stabilized as more segments were included in the composite samples. Estimates of the variance among fish or other population segments can be recovered using appropriate compositing procedures and specially-designed studies

An Alternative Approach for Computation of Annual Toxic Contaminant Loadings in Urban Runoff

Abstract An alternative approach was presented for estimating annual toxic contaminant loadings in urban runoff. In this method, the mean contaminant concentrations are calculated by a regression method. In the computation of contaminant loadings, the load component transported by the liquid phase was estimated by multiplying the mean concentration in water by the runoff volume simulated by the STORM model. The load component transported by suspended solids was calculated by multiplying the mean concentration in solids by the event mean solids concentrations reported in the NURP Program. The loadings calculated by this method were compared with those obtained from whole water samples, and the differences are within an order of magnitude. Since more parameters are used in this approach, it appears more suitable for use in sensitivity analysis of parameters, and more flexible in evaluations of controls measures.

Emerging insects as a biotic pathway for movement of 2,3,7,8-tetrachlorodibenzofuran from lake sediments

Emerging insects are a potential biotic transport route for export of contaminants sequestered in lake sediments to surrounding aquatic and terrestrial ecosystems Emerging insects (mainly Diptera) were collected from four lake mesocosms treated with 10 μg of sediment-sorbed 2,3,7,8-tetrachlorodibenzofuran Insects emerging from the mesocosms had a mean contaminant concentration of 228 pg/g wet weight Contaminant export by emerging insects was from 0 2 to 2 1% of the total sediment contaminant content annually

EMERGING INSECTS AS A BIOTIC PATHWAY FOR MOVEMENT OF 2,3,7,8-TETRACHLORODIBENZOFURAN FROM LAKE SEDIMENTS

Emerging insects are a potential biotic transport route for export of contaminants sequestered in lake sediments to surrounding aquatic and terrestrial ecosystems Emerging insects (mainly Diptera) were collected from four lake mesocosms treated with 10 μg of sediment-sorbed 2,3,7,8-tetrachlorodibenzofuran Insects emerging from the mesocosms had a mean contaminant concentration of 228 pg/g wet weight Contaminant export by emerging insects was from 0 2 to 2 1% of the total sediment contaminant content annually

Geostatistics Applied to Groundwater Pollution. III: Global Estimates

Kriging, a geostatistical technique, can be used to obtain the best (minimum estimation error), linear, unbiased estimates of contaminant concentrations at points within a contaminant plume from a set of measured contaminant concentrations. The present paper presents the theoretical and numerical procedures needed to combine these local estimates to obtain global estimates for the mean contaminant concentration in any specified portion of the plume. Procedures for computing global estimation errors are also presented. Global estimates and estimation errors can then be used to compute standard confidence intervals. The use of the developed methods is illustrated by a set of measured groundwater contaminant concentrations from a hazardous waste site.