PAH Concentrations In Sediments Research Articles

Comparison of Black Carbon, Total Organic Carbon, and PAH Concentrations in Surface Sediments from Two Main Rivers in Henan Province, China

Black carbon (BC) in surface sediments from Henan section of Yellow River and Huaihe River, China, was determined. Average content of BC in Huaihe River was 0.33%, higher than that in Yellow River (n = 23) with mean value of 0.15%. Distribution patterns of BC in Yellow River and Huaihe River were similar, namely that tributaries had higher BC content than main stream. In addition, BC content in the mainstream of Yellow River and Huaihe River decreased with altitude. The BC content presented a significant positive correlation with clay (r = 0.672; p < 0.01) content in Yellow River, while neither did in Huaihe River. The ratio of BC/TOC ranged from 1.8–57.4% (median 29.6%), evidencing pyrogenic fossil fuel source of BC in Yellow River. Relatively low values of BC/TOC in Huaihe River (5.3%–28.8%, median 7.5%,) reflected that the origin of BC is from burning of biomass. In addition, Pearson rank correlation analysis showed that BC was in strong correlation with lighter PAH in Yellow River, while BC was in significant correlation with heavier PAH in Huaihe River. The ratio of BC/TOC indicated that BC in Yellow River mainly came from fossil fuel combustion, while BC in Huaihe River was primarily from biomass burning.

Assessing PAHs pollution in Shandong coastal area (China) by combination of chemical analysis and responses of reproductive toxicity in crab Portunus trituberculatus.

The concentrations of PAHs in seawater and sediments were measured at three selected sites (S1, S2, and S3) along the coastal area of Shandong (China) in April, May, and June, 2015, which ranged from 29.72 to 123.88ng/L and 82.62 to 232.63ng/g, respectively. Meanwhile, the reproductive toxicity responses in crab Portunus trituberculatus were also evaluated to assess the pollution of PAHs during the sampling period. Chemical analysis showed that S3 was the most PAH-contaminated area while S1 was the least, and the biochemical parameters concerned with reproduction were efficiently responded to the three sites, especially in S3 (p<0.05). Moreover, the principal component analyses (PCA) showed that parameters for DNA alkaline unwinding, protein carbonyl content, and lipid peroxidation levels in two genders, 17β-estradiol in female, testosterone and TESK2 gene expression in male crabs, were closely correlated with the concentrations of PAHs (2+3 rings, 4 rings, and 5+6 rings), which were considered to be good candidate indicators to assess the environmental pollutions resulting from PAHs in the coastal area of Shandong, China.

Prediction of the bioaccumulation of PAHs in surface sediments of Bohai Sea, China and quantitative assessment of the related toxicity and health risk to humans

Assessing the health risk of PAHs in sediments was quite difficult because sediment occurred in sea floor, and it was very hard to contact with them directly for humans. This study was attempted to reveal the relationship between concentrations of PAHs in surface sediments and health risk of seafood consumers. The transfer (bioaccumulation) of PAHs from surface sediment into benthic organisms was predicted. Source contributions to PAHs and related toxicity and health risks (from intake of PAHs-contaminated benthic organisms) were studied based on PMF model and Monte Carlo simulation, respectively. Total concentrations of PAHs (TPAHs) ranged from 149.40 to 1211.97ngg−1 in sediments of Bohai Sea (BS), China. Petroleum and vehicular emission, coal combustion and coke oven constituted 40.0%, 32.2% and 27.8% of PAHs, respectively, but contributed 53.0%, 22.8% and 24.2% of toxicity posed by PAHs in sediment. For children, teens and adults, the 95th percentile carcinogenic and non-carcinogenic risks were below the threshold values of 10−6 and 1.0, respectively, suggesting no potential health risk. Sensitivity analysis suggested that exposure duration (ED) and PAH concentrations (CS) were the two most sensitive parameters in risk assessment. The results provided a method to evaluate the quality of sediments and the potential health risk related to PAHs in marine sediments.

Assessment of the bioavailability and phytotoxicity of sediment spiked with polycyclic aromatic hydrocarbons.

Large amounts of sediment are dredged globally every year. This sediment is often contaminated with low concentrations of metals, polycyclic aromatic hydrocarbons, pesticides and other organic pollutants. Some of this sediment is disposed of on land, creating a need for risk assessment of the sediment disposal method, to minimize the degradation of environmental quality and prevent risks to human health. Evaluating the available fractions of certain polycyclic aromatic hydrocarbons is very important, as in the presence of various organisms, they are believed to be easily subject to the processes of bioaccumulation, biosorption and transformation. In order to determine the applicability of applying these methods for the evaluation of pollutant bioavailability in sediments, the desorption kinetics from the sediment of various polycyclic aromatic hydrocarbons in the presence of Tenax and XAD4 were examined over the course of 216 h. Changes in the PAH concentrations in dredged sediments using five different seed plants during a short time of period (10 days) were also followed. Using chemical extraction techniques with Tenax and XAD4, a time of around 24 h is enough to achieve equilibrium for all four PAHs. Results showed good agreement between the seed accumulation and PAH extraction methods with both agents. If we compare the two extraction techniques, XAD4 gave better results for phenanthrene, pyrene and benzo(a)pyrene, and Tenax gave better results for chrysene.

Variability of present and past PAH (polyaromatic hydro carbons) concentrations in sediments of the SW Barents Sea

Variability of present and past PAH (polyaromatic hydro carbons) concentrations in sediments of the SW Barents Sea

Limnogeology, news in brief

We’ve invited Michael R. Rosen, water quality spe-cialist within the USGS Water Science Field Team inCarson City and Elizabeth Gierlowski-Kordesch, pro-fessor of geology at Ohio University, to take a look atthe intriguing new developments that are emerging inlimnogeologic studies. These studies are increasingour understanding of how climate and movements ofthe Earth’s surface influence terrestrial environments,as well as how contaminants are distributed andretained in the environment. They present a selectionof recent significant research on sediments, rock, andbiota that have been preserved in modern and ancientlake basins.Limnogeology is a relatively new field of study in a formalsense, in that the term limnogeology was coined in the early1990s, although research on how lakes have formed andevolved over time has been studied since at least the 1800s(for example Russell 1885; Gilbert 1890). Over the pastseveral years, new exciting techniques have been applied tolimnogeologic studies. These studies have expanded ourunderstanding of how climate and tectonics affect changein terrestrial environments. As these past changes havebeen shown to be important for predicting future climatechange, interest in limnogeology has increased. In addition,understanding how contaminants are distributed and pre-served in the environment is essential for protecting wild-life and human health.Lakes form in a diversity of geologic structures and rocktypes as well as all climate zones. The diversity of lacus-trine geology and biology that contribute to lake sedimentsrequires a multidisciplinary approach to solve importantissues. Issues such as differences between regional andglobal paleoclimate variations over time, tectonic effectsover time, changes in contaminant histories with varyingland use within watersheds, and the unraveling of hydro-logic changes caused by human or natural modificationswithin a watershed through interdisciplinary techniqueselucidate these problems. Because of the variety of subjectmatter in lacustrine basins, the studies presented here aredivided into studies of contaminants in lake basins, ofrecent lake basins (unconsolidated lake sediments) and ofancient lake basins (sediments that have lithified into rock).Contaminants in lake sedimentsOne of the most interesting studies of substantial regionalcontamination of lake sediments comes from studies ofpolycyclic aromatic hydrocarbons (PAHs) that are erodedand leached from coal-tar-based sealants used to protectand enhance the appearance of asphalt pavement (primarilyparking lots and driveways) in the United States andCanada. Van Metre and Mahler (2010) showed that thesealants were a major contributor to PAH concentrations insediments of 40 lakes throughout the United States. HighPAH concentrations were noted in central and eastern lakesin the USA where coal-tar is more frequently used than inthe west. Based on fingerprinting of the different PAHcompounds in the sediment, Van Metre and Mahler (2010)

Polycyclic aromatic hydrocarbons in sediments from the Old Yellow River Estuary, China: Occurrence, sources, characterization and correlation with the relocation history of the Yellow River

The levels of 16 USEPA priority PAHs were determined in surface sediments and one dated sediment core from the abandoned Old Yellow River Estuary, China. Total PAH concentrations in the surface sediments ranged from 100.4 to 197.3ngg−1 dry weight and the total toxic equivalent quantity (TEQcarc) values of the carcinogenic PAHs were very low. An evaluation of PAH sources based on diagnostic ratios and principal component analysis suggested that PAHs in the surface sediments mainly derived from combustion sources. The total PAH concentrations altered significantly with year of deposition and showed quite different patterns of change compared with other studies: it is hypothesized that the principal cause of these changes is the relocation of the course of the Yellow River to the sea in 1976 and 1996.

PAH effects on meio- and microbial benthic communities strongly depend on bioavailability

The effects of anthropogenic pollutants in dissimilar habitats can vary depending on differences in bioavailability. The factors determining bioavailability are not yet fully understood. This study was performed to evaluate whether analysis of total PAH concentrations in sediments is a satisfactory measurement to indicate environmental effects or if bioavailability is needed to be taken into account. We have here performed a 60-day experiment, where nominal PAH concentrations of 1300μg/kg sediment were added to three different marine sediments. Meiofaunal and microbial communities were analyzed for alterations in community response at 30 and 60 days.Results showed that bioavailability of PAHs varied between the three different sediments. Nonetheless, the petroleum addition gave rise to significant negative effects on all three sediments at both time points. The two direct measurements of toxicity on the microbial community, potential nitrification and denitrification, displayed a lower effect of the PAH addition in the muddy sediment at both time points, compared to the other two sediment types. No effects were seen in the analysis of meiofaunal community structure. Measurements of PAH bioavailability in the three sediment types concurred with the results from the microbial community, revealing a lower bioavailability in the muddy sediment compared to the other two sediment types, 34% compared to sandy and 18% compared to organic at day 0. At day 60 it was 61% lower compared to sandy and 20% lower compared to organic. The negative effects of the PAH addition on the microbial nitrogen cycle were in six out of eight cases best correlated to the amount of alkylated bioavailable PAH in the sediments, and thus microbial nitrogen cycle is a possible good indicator for assessing PAH-induced stress.The results presented here have implications for risk analysis studies of petroleum-contaminated marine sediments; consequently, sediment characteristics and its effects on bioavailability are important to include. In addition, these results add to the understanding that bioavailability measurements of PAHs are a more correct assessment compared to measurements of total PAH concentrations, and need to be included when estimating effects of PAHs in marine benthic communities.

Understanding the Chronic Impacts of Oil Refinery Wastewater Requires Consideration of Sediment Contributions to Toxicity

Previous studies at an oil refinery in Saint John, New Brunswick, Canada, found a diminished fish community downstream of the effluent outfall that appeared to be associated with periodic low dissolved oxygen concentrations due to episodic discharges of contaminated transport vessel ballast water. This study was initiated after the ballast water was removed from the effluent to further investigate the potential causes of residual effects in the study stream, Little River. We used field caging of fish, laboratory bioassays, and chemical analysis of effluents and sediments from the field site to determine if the effluent or contaminated sediments were affecting the recovery of the fish community in Little River. The field studies suggested that exposed, caged fish were affected, displaying>40% increases in liver sizes and increased liver detoxification enzyme activity (cytochrome P450 1A, CYP1A); however, similar responses were absent in laboratory exposures that used effluent only. Adding sediments collected from the vicinity of the refinery's outfall to the laboratory bioassays reproduced some of the field responses. Chemical analyses showed high concentrations of PAHs in sediments but low concentrations in the effluent, suggesting that the PAHs in the sediment were contributing more to the impacts than the effluent. Application of effects-based monitoring is suggested as beneficial to identify impacts to fisheries where refinery effluents of this type are involved.

Spatial distribution of polycyclic aromatic hydrocarbons in soil, sediment, and combusted residue at an e-waste processing site in southeast China

The environmental pollution and health impacts caused by the primitive and crude recycling of e-waste have become urgent global issues. Guiyu, China is a major hotspot of e-waste recycling. In this study, the levels and distribution of polycyclic aromatic hydrocarbons in soil in Guiyu were determined to investigate the effect of e-waste activities on the environment and to identify possible sources of these pollutants. Sediment samples from a local duck pond, water gullies, a river tributary, and combusted residue from e-waste burning sites were also investigated. The general trend found in soil (Σ16 PAHs) was acid leaching site > duck pond > rice field > printer roller dump site > reservoir (control site) and ranged from 95.2 ± 54.2 to 5,210 ± 89.6 ng/g (dry wt). The highest average total PAH concentrations were found in combusted residues of wires, cables, and other computer electrical components located at two e-waste open burning sites (18,600 and 10,800 ± 3,940 ng/g). These were 195- and 113-fold higher than the PAH concentrations of soil at the control site. Sediment PAH concentrations ranged from 37.2 ± 6 to 534 ± 271 ng/g. Results of this study provide further evidence of significant input of PAHs to the environment attributed to crude e-waste recycling.

DEPOSITION FLUXES OF POLYCYCLIC AROMATIC HYDROCARBONS IN THE BOTTOM SEDIMENTS OF LAKE PIHKVA

Traditionally the elevated concentrations of PAHs in the bottom sediments of Lake Peipsi are explained by the influence of oil shale industry. To estimate the role of Narva Power Plants (Narva PP) in the deposition of PAHs, we investigated the 210 Pb dated sediment core from Lake Pihkva, where the influence of oil shale industry should be minimal. The distribution of 15 individual PAHs was established, the observed levels of ΣPAHs ranged between 75 and 345 ng/g. PAHs with 4-5 rings implying petrogenic activity accounted for 74 to 87% of ΣPAHs, which is higher than in a similar investigated profile in Lake Peipsi sensu stricto. It means that the role of oil shale industry in PAHs accumulation is strongly overestimated and there should be many other sources whose role needs further investigation.

Ecological Risk Assessment of Poly Aromatic Hydrocarbons in the North Port, Malaysia

Sediment samples collected from the West Port, West Coastal water of Malaysia, were analyzed by GC-MS in order to determine the degree of hydrocarbon contamination, and identify the sources of poly aromatic hydrocarbon and PAHs. Concentrations of PAHs in the port sediments ranged from 98.28 to 3630.22 µg/kg dw. The highest concentration was observed in stations which is closed to the coastline, this locations affected by intensive shipping activities and industrial inputs and they were dominated by the high molecular weight PAHs (4-6- rings). Source identification showed that PAHs originated mostly from the pyrogenic source either from the combustion of fossil fuels, grass, wood and coal (majority of the samples) or from petroleum combustion (Port area). Regarding to risk index (HQ) estimation, only stations 13 (close to container terminal in West Port) is moderately polluted and the rest of stations were in rare or slight adverse biological effects with the PAHs exposure in surface sediment, suggesting PAHs are not considered as contaminants of concern in the West Port.

Integrative sediment assessment at Atlantic Spanish harbours by means of chemical and ecotoxicological tools

This study refers to the integrative assessment of sediment quality in three harbour areas at the Spanish Atlantic Coast: Vigo (Northwestern Spain), Bilbao and Pasajes (Northern Spain). At each site, two lines of evidence have been considered: chemical analyses (metal, PAH and PCB concentrations in sediments and ammonia concentration in bioassays) and toxicity tests (Microtox®, Corophium sp. marine amphipod and Paracentrotus lividus sea urchin larvae). Chemical and ecotoxicological results have been integrated by means of a tabular matrix and a multivariate factorial analysis (FA). Highly toxic samples have been characterised in Vigo and Pasajes harbours while Bilbao samples present toxicity levels ranging from non-toxic to moderately toxic. High toxicity is associated with high levels of contaminants whereas confounding factors (ammonia, organic matter and mud) have been identified to be the main cause of low to moderate toxicity. Based on the obtained results, it can be concluded that deriving potential toxicity of sediments based on comparison with Sediment Quality Guidelines (SQGs) is in agreement to toxicity results in areas presenting high levels of contaminants. However, at lower levels of toxicity (low to moderate), the mismatch between the potential toxicity (SQG approach) and the toxicity measured by bioassays is greater, as the former only accounts for chemical concentrations, without considering the interaction between contaminants and the effect of confounding factors. Contrarily, the multivariate analysis seems to be a robust tool for the integration and interpretation of different lines of evidence in areas affected by different sources of contamination.

High Levels of Sediment Contamination Have Little Influence on Estuarine Beach Fish Communities

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination.

Effect of physico-chemical characteristics on distribution of PAHs in different size sediments from the Wuhan Reach of the Yangtze River, China

The composition and environmental risks of PAHs in different size sediments collected from Yangtze River Catchment in Wuhan, China, were investigated. This study suggested that organic matter content in different size sediments was the main factor affecting the composition and distribution of PAH residues, but there was no significant relationship between the source of organic matter and PAH concentrations in sediments. Interestingly, total N, mostly contributed by organic nitrogen, also an indicator of the fertility of sediments, showed significant correlation with the distribution of PAHs. Black carbon exhibited importance in <25 μm size fraction sediment.

A source mixing model to apportion PAHs from coal tar and asphalt binders in street pavements and urban aquatic sediments

Present-day and more than 30 years old road and footpath pavements from Auckland, New Zealand were analysed for PAHs to test the hypothesis that coal tar based pavement binders contribute to unusually high PAH concentrations in adjacent stream and estuarine sediments. Total PAH (∑ 28PAH) concentrations in the dichloromethane-soluble fraction (“binder”), comprising 5–10% of pavement mass, were as high as 200 000 mg kg −1 (10 000 mg kg −1 in binder + aggregate). Older and deeper pavement layers were strongly pyrogenic, whereas pavement layers from recently sealed roads had a more petrogenic composition and more than 1000 times lower ∑ 28PAH concentrations. Source identification analysis using three PAH isomer ratio pairs (benz(a)anthracene/(benz(a)anthracene + chrysene); benzo(a)pyrene/(benzo(a)pyrene + benzo(e)pyrene); and indeno(1,2,3-cd)pyrene/(indeno(1,2,3-cd)pyrene + benzo(g,h,i)perylene) revealed low PAH (bitumen) pavements to have consistently lower isomer ratios than high PAH (coal tar) samples. Moreover, pavement data for one isomer ratio (e.g. benzo(a)pyrene/(benzo(a)pyrene + benzo(e)pyrene) were highly correlated with those of another isomer ratio (e.g. benz(a)anthracene/(benz(a)anthracene + chrysene) and were bounded at their lower and higher extremes by the characteristics of pure bitumen and coal tar, respectively, suggesting that PAH composition of a given pavement sample could be accounted for by conservative mixing between coal tar and bitumen as source materials. A concentration-weighted mixing model, with coal tar and bitumen as source materials, explained more than 80% of the variance in isomer ratios and enveloped the entire PAH compositional and concentration range encountered. PAH composition and concentrations in adjacent stream sediments (> 15 mg kg −1 dry weight) were consistent with diluted coal tar material as a principal PAH source. Due to the very high PAH concentrations of coal tar, a coal tar content of as little as 0.01% of total sediment mass can account for more than 90% of PAH concentrations in adjacent stream sediments.

Assessment of azaarenes and azaarones (oxidized azaarene derivatives) in the Dutch coastal zone of the North Sea

Azaarones (oxidized derivatives of azaarenes) is a group of newly emerging chemical compounds. Little is known about their occurrence in the aquatic environment. Azaarenes are polycyclic aromatic heterocyclic compounds containing one nitrogen atom in one of the aromatic rings. The (photo) oxidized metabolites of the azaarenes are often more toxic than the parent compound. For the first time the concentration of seven azaarenes and seven primary metabolites have been measured in the surface sediments (fraction < 63 μm) of the Dutch coastal zone of the North Sea. Samples collected in 2000 and 2001 were analyzed using a newly developed method to determine the contents of azaarenes and azaarones simultaneously in a single GC–MS run. The concentrations of acridine, benz[ a]acridine, benz[ c]acridine and 5,6-benzoquinoline varied between 10–63, 3.9–25, 3.3–11 and 3.98–10.84 ng g −1, respectively. Concentrations of 7,8-benzoquinoline and phenanthridine were below the limit of detection. 2-Hydroxyquinoline and 5-hydroxyquinoline, probably metabolites of quinoline, were present in relatively high concentrations: 7.4–949 and 11–188 ng g −1. A gradient was observed with highest concentrations of the sum of azaarenes and the sum of the concentration of their metabolites close to the coast and lower concentrations further offshore. The concentrations of azaarenes and their metabolites are in the same order of magnitude as those found to induce phototoxicity to algae. The concentrations of mineral oil and PAHs in the surface sediments of the Dutch coastal zone of the North Sea were, at most locations, above the Dutch chemical targets for environmental protection. Spatial distribution of PAHs and mineral oil were slightly different from those of azaarenes and transformation products. Simultaneous GC–MS for azaarenes and their degradation products is possible but extraction/clean up can be further improved. Azaarenes as well as their primary metabolic products are present in the marine environment. In sediments the cumulative concentrations of transformation products amount to about four times the cumulative concentrations of the azaarenes. In conclusion, azaarenes and their metabolites constitute a new group of emerging polycyclic aromatic compounds which need more attention in the future.

Polyaromatic hydrocarbons (PAHs) in the Barents Sea sediments: small changes over the recent 10 years

In order to reveal possible multi-year dynamics in sediment PAH concentrations and composition, data sets from the years 2001–2005 have been compared with data sets obtained during the years 1992–1998. K-means-clustering of the 2001–2005 data sets suggests dividing the sampling area into five geographical areas based upon levels and compositions of PAHs. The five areas are Svalbard offshore, Bear Island Trough, SW Barents Sea, NE Barents Sea and SE Barents Sea. Comparison of the two groups of data sets revealed no significant differences between geometric means of PAH concentrations and PAH ratios for sediments from Svalbard offshore, Bear Island Trough and NE Barents Sea. These results are supported by down core analyses of PAH distributions. In the SW Barents Sea area, mean total PAH concentrations found in the 2000s and 1990s did not differ significantly. However, the sum of two- to three-ring PAH compounds and Fossil Fuel Pollution Index in samples of 2000s were significantly higher than in data sets from the 1990s. In the SE Barents Sea area, both total concentrations of pyrogenic PAHs and PAH ratios in the data sets from the 2000s were significantly higher than the 1990s data sets, which suggest higher input of combustion and/or anthropogenic PAHs.

PAHs and PCBs deposited in surficial sediments along a rural to urban transect in a Mid-Atlantic coastal river basin (USA)

PAHs and PCBs were measured in river sediments along a 226 km longitudinal transect that spanned rural to urban land use settings through Valley and Ridge, Piedmont Plateau and Coastal Plain physiographic provinces in the Potomac River basin (mid-Atlantic USA). A gradient in PAH concentrations was found in river bed sediments along the upstream transect in the Potomac and Shenandoah Rivers that correlated with population densities in the nearby sub-basins. Sediment PAH concentrations halved per each ∼40 km of transect distance upstream (i.e., the half-concentration distance) from the urban center (Washington, DC) of the Potomac River basin in direct proportion to population density. The PAH molecular composition was consistent across all geologic provinces, revealing a dominant pyrogenic source. Fluoranthene to perylene ratios served as useful markers for urban inputs, with a ratio > 2.4 observed in sediments near urban structures such as roadways, bridges and sewer outfalls. PCBs in sediments were not well correlated with population densities along the river basin transect, but the highest concentrations were found in the urban Coastal Plain region near Washington, DC and in the Shenandoah River near a known industrial Superfund site. PAHs were moderately correlated with sediment total organic carbon (TOC) in the Shenandoah River and Coastal Plain Potomac River regions, but TOC was poorly correlated with PCB concentrations throughout the entire basin. Although both PAHs and PCBs are widely recognized as urban-derived contaminants, their concentration profiles and geochemistry in river sediments were uniquely different throughout the upper Potomac River basin.

Bayesian spatial modeling of Lavaca Bay pollutants

Locational risk of increased mercury and PAH concentrations in Lavaca Bay, Texas sediments and eastern oysters ( Crassostrea virginica) harvested from Lavaca Bay, Texas were analysed. Chemical analysis results were evaluated utilizing Bayesian geo-statistical methods for comparison of the model fit of a random effects model versus a convoluted model which included both random and spatial effects. For those results fit best with the convoluted model, continuous surface maps of predicted parameter values were created. Sediment and oyster concentrations of mercury and the majority of measured PAHs were fit best with the convoluted model. The locational risks of encountering elevated concentrations of these pollutants in Lavaca Bay sediments and oysters were highest in close proximity to industrial facilities.