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PubMed1997

Experimental effects of tributyltin (TBT) contaminated sediment on a range of meiobenthic communities.

Microcosm experiments have been carried out with whole natural meiobenthic communities to look at the effects of TBT sediment contamination on the community structure of the dominant nematode component of the meiobenthos. TBT has a high affinity for aquatic sediments, yet this is the first study of the effects of this contaminant in sediment on natural benthic communities. Three communities were studied from contrasting locations in south-west England: the intertidal of the Lynher estuary (muddy sediment) and the Exe estuary (sandy sediment) and the subtidal (50m depth) at Rame Head off Plymouth (muddy sand). Fresh sediment with natural meiobenthic communities was incubated for 2 months with TBT-contaminated sediment (three dose levels) in bottles. Nematodes were identified and enumerated and subjected to multivariate data analysis. The sandy Exe estuary fauna was significantly affected by TBT-contaminated sediment at all three doses (0.3, 0.6 and 0.9 microg g(-1) dry wt (as Sn) sediment), whereas the offshore fauna from Rame Head was significantly affected only at the highest dose. The muddy Lynher estuary meiofauna was affected (somewhat peculiarly) at the medium dose level only. Meiobenthic nematodes may not be as sensitive to TBT-contaminated sediment as other infaunal benthos but exhibited responses to levels of contamination still persisting in some UK estuaries and harbours. Comparing the effects of TBT with those of copper and zinc in the same laboratory experiments, our observations suggest that the relative impact of TBT on meiobenthic community structure is not as great as these contaminants in marine sediments. Although there are very few observations of TBT toxicity in sediment, it appears that TBT is toxic at much lower concentrations in seawater (ppb) than it is in sediment (ppm).

Journal Article↗

PubMed2000

Arsenic contamination in wood mice (Apodemus sylvaticus) and bank voles (Clethrionomys glareolus) on abandoned mine sites in southwest Britain.

Arsenic can be highly toxic to mammals but there is relatively little information on its transfer to and uptake by free-living small mammals. The aim of this study was to determine whether intake and accumulation of arsenic by wild rodents living in arsenic-contaminated habitats reflected environmental levels of contamination and varied between species, sexes and age classes. Arsenic concentrations were measured in soil, litter, wood mice (Apodemus sylvaticus) and bank voles (Clethrionomys glareolus) from six sites which varied in the extent to which they were contaminated. Arsenic residues on the most contaminated sites were three and two orders of magnitude above background in soil and litter, respectively. Arsenic concentrations in the stomach contents, liver, kidney and whole body of small mammals reflected inter-site differences in environmental contamination. Wood mice and bank voles on the same sites had similar concentrations of arsenic in their stomach contents and accumulated comparable residues in the liver, kidney and whole body. Female bank voles, but not wood mice, had significantly higher stomach content and liver arsenic concentrations than males. Arsenic concentration in the stomach contents and body tissues did not vary with age class. The bioaccumulation factor (ratio of arsenic concentration in whole body to that in the diet) in wood mice was not significantly different to that in bank voles and was 0.69 for the two species combined, indicating that arsenic was not bioconcentrated in these rodents. Overall, this study has demonstrated that adult and juvenile wood mice and bank voles are exposed to and accumulate similar amounts of arsenic on arsenic-contaminated mine sites and that the extent of accumulation depends upon the level of habitat contamination.

Journal Article↗

PubMed2000

Ecotoxicity revealed in parasite communities of Sigmodon hispidus in terrestrial environments contaminated with petrochemicals.

Several studies have documented contaminant-induced alterations in host-parasite relationships of vertebrate hosts in aquatic environments, suggesting this functional relationship may be useful for monitoring community-level effects of stressors in terrestrial systems. We hypothesized that gastrointestinal helminth communities of hispid cotton rat (Sigmodon hispidus) hosts would be sensitive to exposure to complex mixtures of petrochemicals in soils of tallgrass prairie habitats contaminated with oil refinery wastes. Parasite communities were surveyed (1993-95) on three contaminated and two reference sites on an oil refinery complex in Oklahoma. Abundance of Schizotaenia sigmodontis infections was two-fold higher in hosts from reference than contaminated sites. Strongyloides sigmodontis exhibited pronounced seasonal differences in prevalence and abundance in host populations from reference sites, with much higher seasonal variation compared to hosts from contaminated sites. Other helminth species, including Schizotaenia sigmodontis, Protospirura muris, Longistriata adunca, also exhibited seasonal fluctuations in abundance. Differences in species richness and composition were also observed, with hosts from the reference sites consistently supporting a higher mean number of species compared to those from contaminated sites. Differences in community structure indicate that host-parasite relationships can provide another useful method for monitoring community-level impacts of contamination in a terrestrial system.

Journal Article↗

PubMed2000

The epidemiology of chemical contaminants of drinking water.

A number of chemical contaminants have been identified in drinking water. These contaminants reach drinking water supplies from various sources, including municipal and industrial discharges, urban and rural run-off, natural geological formations, drinking water distribution materials and the drinking water treatment process. Chemical contaminants for which epidemiologic studies have reported associations include the following: aluminium, arsenic, disinfection by-products, fluoride, lead, pesticides and radon. Health effects reported have included various cancers, adverse reproductive outcomes, cardiovascular disease and neurological disease. In evaluating epidemiologic studies for risk assessment, considering whether the study design was qualitative (hypothesis generating) or quantitative (hypothesis testing) is important and whether sufficient epidemiologic data of a quantitative nature exists to determine the dose-response curve. Each of the chemical contaminants mentioned are summarized by study designs (qualitative and quantitative) and whether a dose-response curve based on epidemiologic data has been proposed. Environmental epidemiology studies are driven by environmental exposures of interest. For drinking water contaminants, the design of epidemiologic studies and their interpretation should consider the following exposure issues: the source of the contaminant; other sources of the contaminant; the route of exposure; the frequency, duration and magnitude of exposure; the ability to document an actual internal dose; and the ability to document the dose to the target organ. Health effects of concern have other risk factors that must be measured in the conduct of these studies. In evaluating epidemiologic studies, potential errors and biases that may occur must be considered given the very low magnitude of associations (less than 2.0 for either odds ratio or risk ratio). Given the issues, the next generation of drinking water epidemiologic studies should include a multidisciplinary team beyond traditional epidemiologists and statisticians. Study teams will require toxicologists, chemists, engineers and exposure assessors. Arsenic is briefly discussed as an example of the importance of susceptible populations. Disinfection by-products are discussed as an example of epidemiologic studies of mixtures.

Animals↗

PubMed2003

Groundwater pollution and remediation options for multi-source contaminated aquifers (Bitterfeld/Wolfen, Germany).

Large-scale contaminated megasites like Bitterfeld/Wolfen in the eastern part of Germany are characterized by a regional pollution of soil, surface water and groundwater due to the long and varied history of the chemical industry on location. The pollutants in groundwater may spread to uncontaminated areas and endanger receptors like surface water and drinking water wells according to the site-specific hydrologic regime. In addition, the sheer extension of the contamination at megasites as well as the existence of large densely populated areas and land of high-reuse value prevent a simple risk management strategy of use restriction for the whole area. Since a complete clean-up of the groundwater on a megasite is neither economically feasible nor technically possible within a reasonable time-frame, a multi-approach remediation strategy is needed, taking into account the immediate risks for human health, ecosystem and so-called "protectable goods". Moreover, the contaminants at megasites typically represent a dangerous cocktail of multiple harmful substances stemming from a variety of sources, which may interact with each other and complicate the search for an appropriate remediation strategy. At the SAFIRA-project site in Bitterfeld approaches for in situ remediation of multiple contaminants in groundwater are being tested. Alternatives in local implementation strategies as well as consequences of long-term restrictions for megasites like Bitterfeld need an independent evaluation of the situation using a risk-based approach. For this reason, a GIS-based 3D model of the area including geology, contaminants, hydrogeology, land-use and protected areas has been built. The regional groundwater pollution is characterized by contamination profiles of all monitored substances. In the area of investigation, e.g. threefold and fourfold threshold levels of chlorinated methane, ethane and ethene as well as HCH-isomers, mono-, di- and tetrachlorobenzene, DDT-isomers and benzene are frequently detected in groundwater, that means in at least 60% of the wells that were sampled. High median values of more than 10 microg/l were calculated for cis/trans-1,2-dichloroethene, 1,2-dichloroethane, chloroethene and monochlorobenzene. In general, the regional distribution of contaminants reflect the different sources and pathways, and give first results from a regional point of view, depending on a land-use classification of specific areas.

Chemical Industry↗

PubMed2000

The contribution of statistics in the forensic appraisal of post-transfusion contamination by hepatitis C virus.

Many patients were contaminated by blood products in the 1980s and early 1990s, a period during which there was no means of detecting hepatitis C virus (HCV) and measures of vigilance in French blood transfusion centers were lacking in rigor, and it has become a real public health issue by now. The blood transfusion centers which produce and distribute the products are liable for such contamination, as long as the expert appraisal has established a link of causality between the transfusion and the contamination. When the viral serologic status (i.e. the contaminating potential) of the donors is not known, experts often resort to indirect evidence, including use of probability estimates calculated according to the following method. The probability (P) that there was at least one contaminating donor among those having provided the blood given to a patient, is calculated using the following formula:P=1.(1.pHCV)(N)where pHCV is the prevalence of subjects who have tested positive for anti-C virus antibodies in a population of blood donors, and N is the number of donors having contributed to the transfusion in question. Although the polymerase chain reaction (PCR) is very sensitive, its threshold, below which weak replication is undetectable, varies depending on the technique used. One study has demonstrated that below a dilution of 10(-4), RNA is no longer detected by the majority of laboratories. The specificity of PCR is not flawless either, since false-positive results are found, probably resulting from contamination of the samples. Considering that 0.10% is a reasonable approximation of the prevalence of subjects who had anti-HCV antibodies that were detectable by recombinant immunoblot assay during that period, one can calculate the probability that there is a contaminating donor among the blood donors who contributed to the product that was administered and determine a curve.

Algorithms↗

PubMed1999

Bacterial contamination rates during bone allograft retrieval.

A retrospective study of allograft bone retrieved from 401 donors between January 1987 and March 1996 was performed to determine the incidence of bacterial contamination. Contamination according to type of donor (live, multiorgan, cadaveric) was also determined. Live donors donating a femoral head demonstrated a contamination rate of 13%; multiorgan donors, 24%; and cadaveric donors, 35%. Donor contamination by type of bone (hemipelvis, femur, tibia) showed no significant difference in the multiorgan donors. In cadaveric donors, there was a significant increase in contamination of the hemipelves as compared to the femur and tibias. Recommendations for contamination control in allograft retrieval are given. Our findings are of great significance for musculoskeletal banks that do not secondarily irradiate and rely on screening of allograft bone for contamination alone.

Bacteria↗

PubMed2000

A contaminated binormal model for ROC data: Part III. Initial evaluation with detection ROC data.

RATIONALE AND OBJECTIVES: The authors' purpose was to evaluate how well the contaminated binormal receiver operating characteristic (ROC) model fits (a) degenerate data for which standard ROC models commonly fail and (b) nondegenerate data from exemplary experiments, for which the standard binormal model should be appropriate. MATERIALS AND METHODS: The authors studied two examples of binormally degenerate data, with and without interior points, and ROC rating data from four experiments in visual psychophysics and radiology. The plots of contaminated binormal ROC curves of the binormal degenerate data were examined. For ROC data with at least one interior point, the new model was compared with conventional models on the basis of likelihood-ratio chi2 statistics (G2). RESULTS: With no interior points, the contaminated binormal model gave results consistent with the fundamental principle underlying ROC analysis, that is, for a fixed false-positive probability, the higher the true-positive probability, the better the diagnostic performance. Contaminated binormal ROC curves go through the empirical ROC points of the degenerate data without crossing the chance line or climbing far above the true-positive fractions of the points. For several model ROC studies, the contaminated binormal model gave smaller G2 results than conventional ROC models, although the differences tended to be small, usually with little difference in ROC area. CONCLUSION: The contaminated binormal model fits binormal degenerate data better than conventional ROC models, and it offers an explanation for the degeneracy. The lower G2 values on some classic, nondegenerate ROC data suggest that contamination may not be limited to degenerate ROC data.

Ankle Injuries↗

PubMed1996

Enhancing contaminant control to mitigate aeroallergies.

BACKGROUND: Modern construction techniques such as sealing buildings and reducing air exchange rates to conserve energy often increase indoor air contaminant concentrations, a problem for people with asthma and aeroallergies. Further, a large proportion of the contaminants that are found in indoor air do not reach the filters because the motion of particulates less than about 3 microns in size, 99% of all particulates, is determined more by the normal electrical forces in a room than by the air currents. OBJECTIVE: To determine whether the natural process of aerosol coagulation, which increases particle size, can be speeded-up, thereby enhancing the effectiveness of air currents in returning contaminants to the filters and improving contamination control. METHOD: A set of four experiments using various methods involving particulate and gaseous contaminants are presented. RESULTS: Statistically significant differences in room contaminant load were found in the various experiments as a function of the treatment used. CONCLUSIONS: The effectiveness of filters can be significantly enhanced and the concentration of contaminants in indoor air can be significantly reduced in a straight-forward direct way. The physics underlying the phenomena is described. The implications for allergy and asthma patients are significant, for we now have a new means to substantially improve indoor air quality.

Aerosols↗

PubMed2000

Direct determination of soil surface-bound polycyclic aromatic hydrocarbons in petroleum-contaminated soils by real-time aerosol mass spectrometry

Soil surface-bound polycyclic aromatic hydrocarbons (PAHs) were identified by use of Real-Time Aerosol Mass Spectrometry (RTAMS) in two NIST standard research material (SRM) soils (Montana SRM 2710 and Peruvian SRM 4355) each contaminated separately with three common petroleum hydrocarbons (diesel fuel, gasoline, and kerosene). The described contaminated soil analysis required no sample preparation. Direct laser desorption/ionization mass spectrometric analysis of individual soil particles contaminated with each of the petroleum hydrocarbons at three different contamination levels (0.8, 8, and 80 ppth (wt/wt)) yielded detectable PAH cation distributions that ranged from m/z 128 to 234, depending on the fuel contaminant. The same analysis performed on uncontaminated SRM soils revealed very little (Peruvian) to no (Montana) detectable PAH species. Size analysis showed that most of the individual soil particles analyzed were between 1 and 5 microm in diameter. Tandem mass spectrometry (MS/MS) experiments identified alkyl-substituted two- and three-ringed PAHs in all three petroleum hydrocarbon contaminated soils. However, due to similarities in fragmentation patterns, MS/MS analysis of higher MW species (m/z > 200) was unable to distinguish between the possibility of highly alkyl-substituted three-ringed PAHs and hydrogenated four-ringed PAHs. The described technique offers the direct, rapid determination and characterization of surface-bound PAHs in petroleum-contaminated soils at part-per-million levels without prior extraction, separation, or other sample preparation methods.

Journal Article↗

PubMed2002

Characterization and FATE of PAH-contaminated sediments at the Wyckoff/Eagle Harbor Superfund Site.

Eagle Harbor, a shallow marine embayment of Bainbridge Island, WA approximately 10 miles west of Seattle, WA), was formerly the site of the Wyckoff wood-treatment facility. The facility used large quantities of creosote in its wood-treating processes from the early 1900s to 1988. Historical creosote seepage into the harbor resulted in substantial accumulation of polycyclic aromatic hydrocarbon (PAH) contamination in the harbor sediments over time. This investigation focused on the distribution and fate of the PAH-contaminated harbor sediments. Analyses of 10 sediment cores using total petroleum hydrocarbon (TPH) fingerprinting, the distribution of 50 PAH analytes, and sediment age dating revealed the contributions of three distinct sources of PAHs to sediment contamination in the harbor during various periods over the past 100 years; namely, creosote, urban runoff, and natural background. Surface sediments (upper 20-30 cm) in the cores closestto the Wyckoff wood-treatment facility and southeast of an existing cap were dominated by urban runoff and weathered creosote; the deeper sediments (> 30 cm) were heavily contaminated with relatively unweathered creosote and some pure-phase creosote. Cores located the furthest from the area of contamination, in the center of the harbor, were dominated by urban runoff, showed no signs of creosote contamination, and had much lower PAH and TPH concentrations than those adjacent to the facility. In the four cores in the center of the Harbor, farthest from the former Wyckoff facility, PAH concentrations increased significantly (p < 0.01) with proximity to the northern shore of the harbor, which is more heavily developed than the southern shore and is where all automobile traffic enters and exits the island through the Bainbridge Island ferry terminal. Deeper portions of these cores were contaminated primarily with natural background PAHs, likely representing preurbanization sediments. Sedimentation rates ranged from 0.54 to 1.10 gm/ cm2 in the four cores located in the middle of the harbor, and for the single nearshore core that could be used to calculate sedimentation rates. Recognition that urban runoff has been a fairly consistent and ongoing source of PAHs to the harbor's sediments for the past 50-70 years may influence future sediment management decisions for this site with respect to long-term monitoring of surface sediments to assess cap performance. The results provided information on the ability of Eagle Harbor sediments to recover under natural conditions, identified the occurrence of creosote-derived PAH weathering in off-cap surface sediments, and distinguished between these distinct PAH sources in the harbor (creosote, urban runoff, and natural background).

Environmental Monitoring↗

PubMed2002

Anaerobic, sulfate-dependent degradation of polycyclic aromatic hydrocarbons in petroleum-contaminated harbor sediment.

It has previously been demonstrated that [14C]-labeled polycyclic aromatic hydrocarbons (PAHs) can be oxidized to 14CO2 in anoxic, PAH-contaminated, marine harbor sediments in which sulfate reduction is the terminal electron-accepting process. However, it has not previously been determined whether this degradation of [14C]-PAHs accurately reflects the degradation of the in situ pools of contaminant PAHs. In coal tar-contaminated sediments from Boston Harbor, [14C]-naphthalene was readily oxidized to 14CO2, but, after 95 d of incubation under anaerobic conditions, there was no significant decrease in the detectable pool of in situ naphthalene in these sediments. Therefore, to better evaluate the anaerobic biodegradation of the in situ PAH pools, the concentrations of these contaminants were monitored for ca. 1 year during which the sediments were incubated under conditions that mimicked those found in situ. There was loss of all of the PAHs that were monitored (2-5 ring congeners), including high molecular weight PAHs, such as benzo[a]pyrene, that have not previously been shown to be degraded under anaerobic conditions. There was no significant change in the PAH levels in the sediments amended with molybdate to inhibit sulfate-reducing bacteria or in sediments in which all microorganisms had been killed with glutaraldehyde. In some instances, over half of the detectable pools of in situ 2-3 ring PAHs were degraded. In general, the smaller PAHs were degraded more rapidly than the larger PAHs. A distinct exception in the Boston Harbor sediment was naphthalene which was degraded very slowly at a rate comparable to the larger PAHs. In a similar in situ-like study of fuel-contaminated sediments from Liepaja Harbor, Latvia, there was no decline in PAH levels in samples that were sulfate-depleted. However, when the Latvia sediments were supplemented with sufficient sodium sulfate or gypsum to elevate pore water levels of sulfate to approximately 14-25 mM there was a 90% decline in the naphthalene and a 60% decline in the 2-methylnaphthalene pool within 90 days. These studies demonstrate for the first time that degradation by anaerobic microorganisms can significantly impact the in situ pools of PAHs in petroleum-contaminated, anoxic, sulfate-reducing harbor sediments and suggest that the self-purification capacity of contaminated harbor sediments is greater than previously considered.

Bacteria, Anaerobic↗

PubMed2003

Interactions of organic contaminants with mineral-adsorbed surfactants.

Sorption of organic contaminants (phenol, p-nitrophenol, and naphthalene) to natural solids (soils and bentonite) with and without myristylpyridinium bromide (MPB) cationic surfactant was studied to provide novel insightto interactions of contaminants with the mineral-adsorbed surfactant. Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. The Kss values for contaminants were always higher than respective partition coefficients with surfactant micelles (Kmc) and natural organic matter (Koc). At examined MPB concentrations in water the three organic contaminants showed little solubility enhancement by MPB. At low sorbed-surfactant levels, the resulting mineral-adsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very high Kss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulklike medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The results provide a reference to the use of surfactants for remediation of contaminated soils/sediments or groundwater in engineered surfactant-enhanced washing.

Adsorption↗

PubMed2003

"Humic coverage index" as a determining factor governing strain-specific hydrocarbon availability to contaminant-degrading bacteria in soils.

We report development of a novel parameter for quantifying the amount of humic and fulvic acids per unit surface area in a particular soil. This quantity, the "humic coverage index" (HCI), provides a measurement of the relative spatial extents and/or thicknesses of the humic/fulvic overlayers in different soils, and, therefore, can be used in modeling various soils' behavior in sequestration processes in which humic materials are involved. HCI is herein applied to modeling biodegradation of aromatic and aliphatic hydrocarbons (phenanthrene, pyrene, and hexadecane) by several bacterial strains. Results indicate that, for the cases studies here, contaminant biodegradation is highest at a particular HCI and decreases if the coverage density of humic material is lower or higher than this optimum value. The HCI value at which maximal degradation was observed varied across different strains (indicating strain-specific differences in ability to degrade contaminants sorbed to humic materials) and, to a lesser extent, across different contaminants. The HCI concept is also demonstrated to be useful in explaining soil-, strain-, and contaminant-specific variations in the ability of fulvic acid supplementation to enhance contaminant biodegradation. Finally, we show that, in general, strains which are comparatively better at degrading contaminants in high-HCI soils also show enhanced contaminant mineralization in vitro in the presence of humic acids, such as when hydrocarbons are adsorbed onto these materials.

Alkanes↗

PubMed2004

Long-term recovery of PCB-contaminated surface sediments at the Sangamo-westonl Twelvemile Creek/lake Hartwell Superfund Site.

Natural recovery of contaminated sediments relies on burial of contaminated sediments with increasingly clean sediments over time (i.e., natural capping). Natural capping reduces the risk of resuspension of contaminated surface sediments, and it reduces the potential for contaminant transport into the food chain by limiting bioturbation of contaminated surface or near-surface sediments. This study evaluated the natural recovery of surface sediments contaminated with polychlorinated biphenyls (PCBs) at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site (Lake Hartwell), Pickens County, SC. The primary focus was on sediment recovery resulting from natural capping processes. Total PCB (t-PCB), lead-210 (210Pb), and cesium-137 (137Cs) sediment core profiles were used to establish vertical t-PCB concentration profiles, age date sediments, and determine surface sedimentation and surface sediment recovery rates in 18 cores collected along 10 transects. Four upgradient transects in the headwaters of Lake Hartwell were impacted by historical sediment releases from three upgradient sediment impoundments. These transects were characterized by silt/ clay and sand layering. The highest PCB concentrations were associated with silt/clay layers (1.8-3.5% total organic carbon (TOC)), while sand layers (0.05-0.32% TOC) contained much lower PCB concentrations. The historical sediment releases resulted in substantial burial of PCB-contaminated sediment in the vicinity of these four cores; each core contained less than 1 mg/kg t-PCBs in the surface sand layers. Cores collected from six downgradient Lake Hartwell transects consisted primarily of silt and clay (0.91-5.1% TOC) and were less noticeably impacted by the release of sand from the impoundments. Vertical t-PCB concentration profiles in these cores began with relatively low PCB concentrations at the sediment-water interface and increased in concentration with depth until maximum PCB concentrations were measured at approximately 30-60 cm below the sediment-water interface, ca. 1960-1980. Maximum t-PCB concentrations were followed by progressively decreasing concentrations with depth until the t-PCB concentrations approached the detection limit, where sediments were likely deposited before the onset of PCB use at the Sangamo-Weston plant. The sediments containing the maximum PCB concentrations are associated with the period of maximum PCB release into the watershed. Sedimentation rates averaged 2.1 +/- 1.5 g/(cm2 yr) for 12 of 18 cores collected. The 1994 Record of Decision cleanup requirement is 1.0 mg/kg; two more goals (0.4 and 0.05 mg/kg t-PCBs) also were identified. Average surface sedimentation requirements to meet the three goals were 1.4 +/- 3.7, 11 +/- 4.2, and 33 +/- 11 cm, respectively. Using the age dating results, the average recovery dates to meet these goals were 2000.6 +/- 2.7, 2007.4 +/- 3.5, and 2022.7 +/- 11 yr, respectively. (The 95% prediction limits for these values also are provided.) Despite the reduction in surface sediment PCB concentrations, PCB concentrations measured in largemouth bass and hybrid bass filets continue to exceed the 2.0 mg/kg FDA fish tolerance level.

Aluminum Silicates↗

PubMed2004

Enhanced contaminant desorption induced by phosphate mineral additions to sediment.

Apatite, Ca10(PO4)6(OH,F)2, has been successfully used as a soil amendment at numerous sites to immobilize metals and radionuclides. Such sites commonly contain multiple contaminants; the impact of apatite on these contaminants is expected to vary greatly. The objective of this study was to determine the influence of apatite on nontargeted sediment contaminants. Laboratory batch experiments were conducted under oxidized (several weekly wet/dry cycles) and reduced (water-saturated) conditions with a sediment collected from a wetland contaminated with numerous metals and radionuclides. Apatite additions resulted in the significant (p < or = 0.05) reduction of porewater Cd, Co, Hg, Pb, and U concentrations. However, apatite additions also resulted in the enhanced desorption of As, Se, and Th. Increases in porewater As and Se concentrations were the result of phosphate competitive exchange and not to the release of these contaminants directly from the apatite, which contained 29 mg kg(-1) As and 0.2 mg kg(-1) Se. Apatite additions increased porewater Th and organic C concentrations under oxidized (Eh = 497 mV) but not reduced (Eh = 65 mV) conditions. In the oxidized system, the leachate from the apatite treatment had a brown coloration and contained 226 mg L(-1) organic C, as compared to 141 mg L(-1) in the unamended samples. The desorbed organic C likely contained significant quantities of Th. This conclusion was supported by (i) the observation that porewater Th partitioned to hydrophobic resins, (ii) thermodynamic calculations which predicted that essentially all porewater Th existed as organic matter complexes, and (iii) there were significant correlations (r = 0.91, n = 8, p < or = 0.01) between porewater organic C and Th concentrations. Sediment additions of zero-valent iron particles along with the apatite eliminated the enhanced desorption of As, Se, and Th observed when only apatite was added. This study underscores the importance of monitoring the influence of sediment amendments on nontarget contaminants and provides examples of how the sediment additions of apatite can effectively immobilize some contaminants while enhancing the mobility of others.

Apatites↗

PubMed2005

Field-scale evaluation of the passive flux meter for simultaneous measurement of groundwater and contaminant fluxes.

A new method, passive flux meter (PFM), has been developed and field-tested for simultaneously measuring contaminant and groundwater fluxes in the saturated zone at hazardous waste sites. The PFM approach uses a sorptive permeable medium placed in either a borehole or monitoring well to intercept contaminated groundwater and release "resident" tracers. The sorbent pack is placed in a groundwater flow field for a specified exposure time and then recovered for extraction and analysis. By quantifying the mass fraction of resident tracers lost and the mass of contaminant sorbed, groundwater and contaminant fluxes are calculated. Here, we assessed the performance of PFMs at the Canadian Forces Base Borden field site in Ontario, Canada. Two field tests were conducted under imposed groundwater flow fields: (1) radial flow to a well and (2) linear flow in a test channel confined by sheet pile walls on three sides. Both tests demonstrate that the local fluxes measured by PFM and averaged overthe screen interval were within 15% of imposed groundwaterflow and within 30% of measured contaminant mass flux. Patterns in depth variations in groundwater and contaminant fluxes, determined by the PFM approach, allow for site characterization at a higher spatial resolution. These results support the PMF method as a potential innovative alternative for measuring groundwater and contaminant fluxes in screened wells.

Alcohols↗

PubMed2006

Adjusting for temporal change in trophic position results in reduced rates of contaminant decline.

The development of ecological tracers to track the flow of energy and nutrients through food webs has provided new insights into the factors that are important in regulating diet composition in wildlife. The Great Lakes Herring Gull Monitoring Program has provided information regarding temporal trends in levels of bioaccumulative contaminants since the early 1970s. In recent years, data from this program have also been generated to examine ecological changes in the Great Lakes. Because the contaminants that are evaluated as part of this program biomagnify, food is the primary determinant of contaminant concentrations in the eggs that are analyzed annually. Fluctuations in diet composition could affect the interpretation of temporal trends by affecting exposure to contaminants. Retrospective analyses involving ecological tracers, i.e., stable nitrogen isotopes and fatty acids, have shown temporal change in the diets of Great Lakes herring gulls at some monitoring colonies. These dietary differences have led to temporal variation in the trophic position of herring gulls. Given that higher trophic level organisms incur greater exposure to biomagnifying contaminants, it is necessary to adjust for these temporal changes in trophic position to get an accurate indication of how contaminant burdens are changing within the Great Lakes ecosystem. Here, we outline a method to adjust for temporal changes in indicator species trophic position and discuss how these adjustments affect the interpretation of contaminant temporal trend monitoring data.

Animals↗