Richard F. Bopp

Methylmercury exposure in a subsistence fishing community in Lake Chapala, Mexico: an ecological approach

BackgroundElevated concentrations of mercury have been documented in fish in Lake Chapala in central Mexico, an area that is home to a large subsistence fishing community. However, neither the extent of human mercury exposure nor its sources and routes have been elucidated.MethodsTotal mercury concentrations were measured in samples of fish from Lake Chapala; in sections of sediment cores from the delta of Rio Lerma, the major tributary to the lake; and in a series of suspended-particle samples collected at sites from the mouth of the Lerma to mid-Lake. A cross-sectional survey of 92 women ranging in age from 18-45 years was conducted in three communities along the Lake to investigate the relationship between fish consumption and hair mercury concentrations among women of child-bearing age.ResultsHighest concentrations of mercury in fish samples were found in carp (mean 0.87 ppm). Sediment data suggest a pattern of moderate ongoing contamination. Analyses of particles filtered from the water column showed highest concentrations of mercury near the mouth of the Lerma. In the human study, 27.2% of women had >1 ppm hair mercury. On multivariable analysis, carp consumption and consumption of fish purchased or captured from Lake Chapala were both associated with significantly higher mean hair mercury concentrations.ConclusionsOur preliminary data indicate that, despite a moderate level of contamination in recent sediments and suspended particulate matter, carp in Lake Chapala contain mercury concentrations of concern for local fish consumers. Consumption of carp appears to contribute significantly to body burden in this population. Further studies of the consequences of prenatal exposure for child neurodevelopment are being initiated.

Mixing of particles and organic constituents in sediments from the continental shelf and slope off Cape Cod: SEEP—I results

Sediment cores were collected from the continental shelf and slope along the SEEP—I transect (71°W) south of New England. Profiles of 210Pb and of239,240Pu were measured in the cores. Measurable amounts of Pu and of unsupported 210Pb occurred to the same depth in every core where both were measured, indicating that the distributions of tracers added to the slope sediments during the past 100 years are controlled by sediment mixing processes. Mixing coefficients of 0.14–1.0 cm2 y−1 were obtained from the210Pb and Pu distributions in slope sediments. A sediment mixing model that incorporates these mixing rates and a sedimentation rate of about 0.01 g cm−2 y−1 determined from other information predicts the measured distributions of DDT and related compounds in one core from the slope. An upper limit for the deposition of organic carbon in the slope sediments of 2.5 g C m−2 y−1 is obtained, significantly lower than earlier estimates. The measured 14C age of surface sediments is greater than predicted from a model for steady-state accumulation of planktonic detritus, suggesting that some of the carbon deposited on the slope is older reworked material, possibly derived from the continent or eroded from other marine deposits.

Sediment-derived chronologies of persistent contaminants in Jamaica Bay, New York

Chronologies of particle-associated contaminant levels were developed for Jamaica Bay, an embayment of the Atlantic Ocean on southwestern Long Island. A major potential source of contaminants to the system is wastewater discharge, which comprises most of the freshwater input to the bay. Sediment core sections were analyzed for Cs-137, Pu-239, 240, and Be-7 activities which were then used to establish net particle accumulation rates. Samples deposited from the early 1950s through the late 1980s were analyzed for metals and chlorinated hydrocarbon contaminants. Trace metals, including copper, lead, chromium, zinc, and mercury, were elevated to levels several times those of pre-industrial concentrations. These metals decreased by about 50% between the mid 1960s and the late 1980s. Chlorinated hydrocarbon concentrations, including polychlorinated biphenyls, chlordane, and dichlorodiphenyltrichloroethane-derived compounds, decreased by a factor of five to ten between the late 1960s and the late 1980s. Local improvements in wastewater treatment and national efforts to regulate the uses and releases of specific chemicals are the most likely explanation of declines in contaminant levels in these sediments.

Childhood Lead Exposure After the Phaseout of Leaded Gasoline: An Ecological Study of School-Age Children in Kampala, Uganda

Background Tetraethyl lead was phased out of gasoline in Uganda in 2005. Recent mitigation of an important source of lead exposure suggests examination and re-evaluation of the prevalence of childhood lead poisoning in this country. Ongoing concerns persist about exposure from the Kiteezi landfill in Kampala, the country’s capital. Objectives We determined blood lead distributions among Kampala schoolchildren and identified risk factors for elevated blood lead levels (EBLLs; ≥ 10 μg/dL). Analytical approach Using a stratified, cross-sectional design, we obtained blood samples, questionnaire data, and soil and dust samples from the homes and schools of 163 4- to 8-year-old children representing communities with different risks of exposure. Results The mean blood lead level (BLL) was 7.15 μg/dL; 20.5% of the children were found to have EBLL. Multivariable analysis found participants whose families owned fewer household items, ate canned food, or used the community water supply as their primary water source to have higher BLLs and likelihood of EBLLs. Distance < 0.5 mi from the landfill was the factor most strongly associated with increments in BLL (5.51 μg/dL, p < 0.0001) and likelihood of EBLL (OR = 4.71, p = 0.0093). Dust/soil lead was not significantly predictive of BLL/EBLL. Conclusions Lead poisoning remains highly prevalent among school-age children in Kampala. Confirmatory studies are needed, but further efforts are indicated to limit lead exposure from the landfill, whether through water contamination or through another mechanism. Although African nations are to be lauded for the removal of lead from gasoline, this study serves as a reminder that other sources of exposure to this potent neurotoxicant merit ongoing attention.

Occurrence of Alkyltrimethylammonium Compounds in Urban Estuarine Sediments: Behentrimonium As a New Emerging Contaminant

The distribution of alkyltrimethylammonium compounds (ATMAC), cationic surfactants used in a wide variety of applications, has been determined in sediments from Jamaica Bay (NY). Total concentrations in surficial sediments collected between 1998 and 2008 ranged from 361 to 6750 ng/g. The highest values were found in samples from a deeper basin directly affected by treated wastewater discharges. Behentrimonium, a mixture dominated by a homologue having 22 carbon atoms in its alkyl chain (ATMAC 22), was identified for the first time using time-of-flight mass spectrometry and accounted for approximately 80% of the total ATMAC in recent sediment samples. Analyses of a dated sediment core and subsequent surface grab samples revealed an exponential increase in concentration over the last three decades with a doubling time of 3.9 years. Similar temporal trends were seen in surface samples from other sites in Jamaica Bay and Newton Creek (NY), another site greatly influenced by wastewater discharges. This dramatic increase in ATMAC 22 reflects greater use of behentrimonium and likely replacement of other products containing other ATMAC homologues in personal care products. Further monitoring is recommended to assess the environmental risk and fate of this persistent emerging contaminant.

Stable lead isotopes, contaminant metals and radionuclides in upper Hudson River sediment cores: implications for improved time stratigraphy and transport processes

Radionuclide, stable lead isotope and trace metal analyses on fine-grained sediment cores collected along a 24-mile reach of the upper Hudson River were used to establish temporal trends of contaminant loadings, to establish stable lead isotopes as an additional stratigraphic tool, and as tracers for resolving particle transport fluxes over periods of decades. Very large contaminant inputs of Cd, Sb, Pb and Cr were evident in the sediment record. One potential large source for these metals was from a pigment manufacturing facility in Glens Falls, NY. The total range in stable lead isotope ratios observed in well-dated cores from about 15 miles downstream of the potential metal inputs was large (e.g., maximum difference in 206 Pb/ 207 Pb is 10%) and characterized by four major shifts occurring in the 1950s, 1960s, 1970s and 1980s. The temporal trend in 206 Pb/ 207 Pb has been used to establish precise dating of a sediment core from 24 miles further downstream. The large magnitude and abrupt shifts in stable lead isotope ratios preserved in upper Hudson sediment cores provide a way to significantly improve dating models, based only on radionuclide analyses. Cadmium, lead and antimony were identified as quite sensitive tracers of upper Hudson sediments due to the magnitude of contamination and the lack of significant additional downstream sources of these contaminant metals. Metal measurements in a pair of sediment cores located 24 miles apart were used to constrain relative fluxes of sediment entering the river between the two coring locations, with sediment sections deposited between the early 1960s and the late 1970s in these two cores suggesting that 3–4 times more sediment entered the river between the two coring sites than was transported from upstream. These dilution factors agree very well with estimates based on suspended sediment measurements during a flood event in April 1994 and with estimates based on mechanistic model of suspended sediment transport between 1977 and 1992. D 2003 Elsevier Science B.V. All rights reserved.

Biodegradation and gas-exchange of gaseous alkanes in model estuarine ecosystems☆

Abstract Gas-exchange biodegradation experiments conducted in model estuarine ecosystems indicate that the ease of degradation of gaseious normal alkanes increases with chain length. The behaviour of gaseous perhalogenated alkanes can be explained by gas exchange alone with no degradation. The initial degradation of C 3 and C 4 alkanes proceeded with half times of a few days to a few weeks, however, after a period of 15–30 days, the rates of degradation increased by at least an order of magnitude.

Analysis of dated sediment samples from the Newark Bay area for selected PCDD/Fs

Abstract To assess the magnitude and extent of 2,3,7,8-TCDD contamination, sediment cores from the Newark Bay estuary and contiguous waters were collected and dated by radiochemical methods. The core sections from two time horizons were analyzed for selected PCDD/Fs. The highest 2,3,7,8-TCDD concentrations were found in sediments from the sampling site nearest a chemical manufacturing facility on the Passaic River where 2,4,5-T had been synthesized. At this site and in Newark Bay sediments, 2,3,7,8-TCDD was the dominant TCDD isomer found, consistent with 2,4,5-T synthesis being a major source of the 2,3,7,8-TCDD.

Study of Sediment Samples Using Instrumental Photon Activiation Multi-Elemental Analysis

Abstract Instrumental Photon Activation Analysis (IPAA) has been used in many fields including environmental geochemistry. In the analysis of soil and sediment samples, the sensitivity of IPAA is comparable to that of standard methods such as atomic absorption spectroscopy. A major advantage of IPAA is that minimal sample processing is required and multi-element analyses can be obtained. In this work, the method of Internal Standard Coupled with Standard Addition Method (ISM-SAM) was applied to IPAA analysis of sediment samples. The equation used in ISM-SAM was derived in detail and the relationship between the elemental mass and the gamma peak counts in the measured spectra was established. It was found that accurate results can be obtained even when the sample and the reference are irradiated at different photon fluxes and measured in different geometries. The ISM-SAM equation was refined to better quantify the relationship between the addition amount and the uncertainty. Applying refined ISM-SAM, a sediment sample from Hudson River was analyzed. The concentrations of Ni, Pb, Zr, Ca, Fe, Mg, Na, Ti, As, Cr, Ce, Co, Rb, and Zn were determined and compared with the results obtained from Atomic Absorption analysis of total acid digests. For elements analyzed by both methods, excellent agreement was found. Meanwhile, the detection limits of photon activation analysis for selected elements were obtained based on the present experimental conditions.

Source apportionment of polycyclic aromatic hydrocarbons (PAHs) into Central Park Lake, New York city, over a century of deposition

Relative contributions of polycyclic aromatic hydrocarbons (PAHs) from combustion sources of wood, petroleum, and coal were computed in sediments from Central Park Lake in New York City (NY, USA) by chemical mass balance based on several reliable source indicators. These indicators are the ratio of retene to the sum of retene and chrysene, the ratio of 1,7-dimethylphenanthrene (DMP) to 1,7-DMP and 2,6-DMP, and the ratio of fluroanthene to fluroanthene and pyrene. The authors found that petroleum combustion-derived PAH fluxes generally followed the historical consumption data of New York State. Coal combustion-derived PAH flux peaked approximately in the late 1910s, remained at a relatively high level over the next 3 decades, then rapidly declined from the 1950s to the 1960s; according to historical New York State coal consumption data, however, there was a 2-peak trend, with peaks around the early 1920s and the mid-1940s. The 1940s peak was not observed in Central Park Lake, most likely because of the well-documented shift from coal to oil as the major residential heating fuel in New York City during the late 1930s. It was widely believed that the decreased PAH concentrations and fluxes in global sediments during the last century resulted from a major energy shift from coal to petroleum. The data, however, show that this shift occurred from 1945 through the 1960s and did not result in an obvious decline. The sharpest decrease, which occurred in the 1970s was not predominantly related to coal usage but rather was the result of multiple factors, including a decline in petroleum usage largely, the introduction of low sulfur-content fuel in New York City, and the introduction of emission-control technologies.