PCB contamination in surface sediments in the coastal waters of Costa Rica

This paper describes the initial investigation of PCB concentrations in four geographical regions (three on the Pacific and one in the Caribbean) of coastal Costa Rica: Bahia Culebra, Golfo Dulce, Golfo de Nicoya, and Limón. Overall total concentrations of PCB were low in all areas except around the port of Golfito (Golfo Dulce). Overall average concentration is 2.80 ng/g dw, with a standard deviation of 2.75. The low concentration could be due to lack of contamination or the subsequent degradation in the warm climate, or the low sorptive capacity of the sediment. Further investigation is ongoing.     

PCBs in Passaic River Sediments: Some Analytical Considerations

Analytical results for Aroclor may contain a great deal of uncertainty if the relative ratios of certain PCB congeners are substantially altered following differential environmental degradation. Selective degradation of PCB congeners has been shown to occur in biological tissues, and recent studies have shown that Aroclor analyses may significantly underestimate PCB concentrations in fish. The purpose of this study is to assess whether a similar phenomenon can occur with PCB-impacted sediments. Five hundred and thirty-seven sediment samples from the Passaic River were analyzed for Aroclors and selected non-ortho (PCB #77, 126, and 169) and mono-ortho (PCB #105, 114, 118, 123, 156, 157, 167, and 189) coplanar PCB congeners. Aroclors 1248 and 1254 were detected in 67 and 53% of the samples, respectively; 54 samples (approximately 10%) did not contain detectable levels of any Aroclors. In these 54 samples, the sum of the detected PCB congener concentrations was significantly greater, on average, than the Aroclor limit of detection by approximately threefold. In individual samples the sum of the PCB congeners exceeded the Aroclor limit of detection by up to 36-fold. In those samples in which Aroclors were detected, the summed PCB congener concentrations exceeded the Aroclor 1248 and 1254 concentrations, on average, by 41 and 33%, respectively. Given the fact that only a fraction of the 209 PCB congeners were quan-titated, these findings indicate that Arocolor data may significantly underestimate total PCB concentrations in Passaic River sediments. Total PCB data obtained from total homologue analysis indicated that Aroclor results underestimated total PCB mass by up to 43-fold. These findings suggest that caution is required when comparing Aroclor sediment data from the Passaic River to total PCB sediment criteria.     

PCB concentrations in sediments from the Gulf of Nicoya estuary, Pacific coast of Costa Rica

Thirty-one sediment samples collected from 1996-2003 from the Gulf of Nicoya estuary on the northwestern coast of Costa Rica, have been obtained for PCB analyses. This is part of the first study to evaluate the PCB contamination in coastal Costa Rica. Overall, the concentrations are low, especially when compared to sediments from more temperate climates and/or sediments from more heavily industrialized areas. Values average less than 3 ng/g dw sediment, however, a few samples contained up to 7 ng/g dw sediment. Sediments with the highest concentrations were located in the Punta Morales area, where muds were sampled from among mangrove roots. The Puntarenas samples had surprisingly low PCB concentrations, likely due to their sandy lithology. The congener distribution within the majority of the samples showed signs of either recent sources or lack of degradation. However, a few sites, specifically some of the inter-gulf islands and more remote samples had congener distributions indicative of airborne contaminants and/or degradation. Considering the presence of airborne PCBs in the Gulf of Papagayo to the north, the lack of airborne PCBs and more varied congener distribution in the Gulf of Nicoya estuary was surprising.     

A phylogeny of Pacific fiddler crabs of the subgenus Minuca (Crustacea,Brachyura, Ocypodidae: Uca) with the description of a new species from a tropical gulf in Pacific Costa Rica

The phylogeny of all Pacific fiddler crab representatives of the subgenus Minuca Bott, 1954 (sensu Beinlich and von Hagen, 2006) is reconstructed. For the molecular analysis, Cox1 mitochondrial and 28S ribosomal nuclear DNA sequences were used. According to these data, same transisthmian sister species relationships are confirmed and a new species of the genus Uca Leach, 1814, Uca osa sp. n., is described from Golfo Dulce, a tropical gulf in Pacific Costa Rica. Morphological as well as molecular data confirm distinctness of this species compared with all other members of the subgenus Minuca, to which it belongs. Distinctive morphological traits are presented to distinguish Uca osa sp. n. from its congeners in the Eastern Pacific.     

Bioreductive deposition of palladium (0) nanoparticles on Shewanella oneidensis with catalytic activity towards reductive dechlorination of polychlorinated biphenyls

Microbial reduction of soluble Pd(II) by cells of Shewanella oneidensis MR-1 and of an autoaggregating mutant (COAG) resulted in precipitation of palladium Pd(0) nanoparticles on the cell wall and inside the periplasmic space (bioPd). As a result of biosorption and subsequent bioreduction of Pd(II) with H2, formate, lactate, pyruvate or ethanol as electron donors, recoveries higher than 90% of Pd associated with biomass could be obtained. The bioPd(0) nanoparticles thus obtained had the ability to reductively dehalogenate polychlorinated biphenyl (PCB) congeners in aqueous and sediment matrices. Bioreduction was observed in assays with concentrations up to 1000 mg Pd(II) l(-1) with depletion of soluble Pd(II) of 77.4% and higher. More than 90% decrease of PCB 21 (2,3,4-chloro biphenyl) coupled to formation of its dechlorination products PCB 5 (2,3-chloro biphenyl) and PCB 1 (2-chloro biphenyl) was obtained at a concentration of 1 mg l(-1) within 5 h at 28 degrees C. Bioreductive precipitation of bioPd by S. oneidensis cells mixed with sediment samples contaminated with a mixture of PCB congeners, resulted in dechlorination of both highly and lightly chlorinated PCB congeners adsorbed to the contaminated sediment matrix within 48 h at 28 degrees C. Fifty milligrams per litre of bioPd resulted in a catalytic activity that was comparable to 500 mg l(-1) commercial Pd(0) powder. The high reactivity of 50 mg l(-1) bioPd in the soil suspension was reflected in the reduction of the sum of seven most toxic PCBs to 27% of their initial concentration.     

An Integrated Case Study for Evaluating the Impacts of an Oil Refinery Effluent on Aquatic Biota in the Delaware River: Sediment Core Studies

The objectives of this study were to (1) determine if historical exceedences of oil and grease concentrations above the limits allowed in the National Pollution Elimination Discharge System permit for the wastewater treatment facility of Motiva Enterprises LLC Refinery, Delaware City, Delaware, could be determined from the sedimentary records of the Delaware River and, if so, (2) were the concentrations of contaminants high enough to be toxic to aquatic biota. Eighty-four surficial sediment samples, both within and outside the influence of the Refinery's discharge plume, were initially evaluated for their appropriateness for coring. Seven stations were ultimately selected for the historical core studies. Based on sediment type, radionuclide (Pb-210, Cs-137 and Be-7) geochronologies, and proximity of the cores to the Refinery, two cores were selected for more detailed polycyclic aromatic hydrocarbon (PAH) analyses. The rapid accumulation area of one core (located in the near-field of the discharge plume) had maximum total PAH (TPAH) concentration peaks at depths of 4 cm (1997; 3100 ng/g dw) and at 8.5–9 cm (1993; 3200 ng/g dw); the second core (located on the far-field periphery of the plume) had a maximum TPAH peak at 6.5 cm (1997; 3200 ng/g dw). In all cases, the maximum TPAH concentrations were below NOAA's Effects Range-Low concentration of 4022 ng/g dw for sediment biota toxicity. A chemical fingerprinting analysis of the PAHs in the two cores showed, however, that the PAHs present in the cores were predominantly pyrogenic PAHs consistent with Delaware River background PAHs. The core results are consistent with historic sediment PAH inputs in an industrial river system. PAH from the Refinery, if present, exist as a non-detectable increment to a high PAH baseline from many sources.     

Geographic variation of PCB congeners in polar bears (Ursus maritimus) from Svalbard east to the Chukchi Sea

We present data on geographic variation in polychlorinated biphenyl (PCB) congeners in adult female polar bears (Ursus maritimus) from Svalbard eastward to the Chukchi Sea. Blood samples from 90 free-living polar bears were collected in 1987-1995. Six PCB congeners, penta to octa chlorinated (PCB-99, -118, -153, -156, -180, -194), were selected for this study. Differences between areas were found in PCB levels and congener patterns. Bears from Franz Josef Land (11,194 ng/g lipid weight) and the Kara Sea (9,412 ng/g lw) had similar DPCB levels and were higher than all other populations (Svalbard 5,043 ng/g lw, East Siberian Sea 3,564 ng/g lw, Chukchi Sea 2,465 ng/g lw). Svalbard PCB levels were higher than those from the Chukchi Sea. Our results, combined with earlier findings, indicate that polar bears from Franz Josef Land and the Kara Sea have the highest PCB levels in the Arctic. Decreasing trends were seen eastwards and westwards from this region. Of the congeners investigated in the present study, the lower chlorinated PCBs are increasing and the high chlorinated PCBs are decreasing from Svalbard eastward to the Chukchi Sea. Different pollution sources, compound transport patterns and regional prey differences could explain the variation in PCB congener levels and patterns between regions.     

Seasonal-spatial distributions,congener profile,and risk assessment of polychlorinated biphenyls (PCBS) in the surficial sediments from the coastal area of Bangladesh

A comprehensive congener specific assessment of polychlorinated biphenyls (PCBs) was conducted for the first time in Bangladesh. All 209 PCB congeners in the surficial coastal sediments from the coastal areas of Bangladesh were analyzed by GC-MS/MS. The total concentrations of PCBs (∑PCBs) varied from 5.27 to 92.21 and 4.61 to 105.3 ng/g dw in winter and summer, respectively, and the ranges were comparable to or higher than those recorded in the sediments from the coastal areas of India, Korea, China, and Taiwan. The seasonal difference in the levels of PCBs was not statistically significant (p > 0.05). The spatial distribution revealed that the areas with recent urbanization and industrialization (Chittagong, Cox’s Bazar and Sundarbans) were more contaminated with PCBs than the unindustrialized area (Meghna Estuary). Moderately chlorinated (4–6 Cl) homologs dominated PCB profiles. A set of congeners based on their detection frequencies and abundance were identified and categorized as potential environmental marker PCBs, which can be used for the future selective monitoring studies where there would be limitations on whole congener assessment. Ecotoxicologically, the sedimentary PCB concentrations exceeded some of the existing environmental quality standards, suggesting a potential threat to the aquatic organisms in the Bangladeshi coastal areas.     

Oil pollution status expressed as the fraction of dissolved and dispersed petroleum hydrocarbons

Four coastal ecosystems with contrasting characteristics were sampled in Costa Rica (2000-2002). Oil pollution status, expressed as the fraction of dissolved/dispersed petroleum hydrocarbons related to chrysene equivalents, was determined by the molecular fluorescence analytical technique. A total of 130 water samples were taken, from the Caribbean (Moín Bay), and from the Pacific (Bahía Culebra, Gulf of Nicoya and Dulce Gulf). On one occasion, seven samples along the Puntarenas estuary were also analysed. In Moín the mean and standard deviation were 0.10 microg x L(-1) +/- 0.18 micro x L(-1), ranging from non detectable (nd) to 0.65 microg x L(-1). For the Pacific ecosystems the total range was from nd to 0.37 microg x L(-1). In Bahia Culebra no fluorescence signals were obtained. In the Gulf of Nicoya the mean and standard deviation were 0.04 microg x L(-1) +/- 0.09 microg x L(-1), from nd to 0.33 microg x L(-1). Values in Dulce Gulf were 0.05 microg x L(-1) +/- 0.11 microg x L(-1), from nd to 0.37 microg x L(-1). Along the Puntarenas estuary the range was 0.17 to 5.91 microg x L(-1), with a mean of 1.21 microg x L(-1) and a standard deviation of +/- 2.10 microg x L(-1). The four coastal ecosystems had concentrations below the 10 microg x L(-1) limit for polluted oceanic areas. The Puntarenas estuary reflects the influence of antropogenic activities from and around the City of Puntarenas. These levels are considered low for inshore waters.     

Congener Level PCB Desorption Kinetics of Field-Contaminated Sediments

The purpose of this research was to study congener level PCB desorption kinetics of field-contaminated sediments and develop a simple methodology to analyze the desorption behavior. Batch desorption kinetic studies were conducted using XAD-4 resin. Two-phase desorption kinetics were observed for most PCB congeners, consisting of an initial fast rate followed by an extended period of slow rate. A dual first-order rate model was fitted to the PCB desorption data to estimate PCB concentrations in the fast and slow desorbing pools. The fast and slow desorption rates were found to decrease with increasing chlorina-tion of PCB congeners, decreasing ortho chlorination, and decreasing temperature. Estimated first-order desorption rate constants for the fast pools were found to be two orders of magnitude higher than those for the corresponding slow pools. The log of first-order rate constants for the different PCB congeners were found to be linearly related to the log of octanol-water partition coefficients. Therefore, desorption rate constants of higher chlorinated PCB congeners, which typically require long-term desorption tests, could be extrapolated using measured rate constants of lower-chlorinated PCB congeners from short-term desorption tests. This finding may provide a process to significantly reduce the duration of experiments required for estimating desorption kinetics.     

Anaerobic methane oxidation in a coastal oxygen minimum zone: spatial and temporal dynamics

Coastal waters are a major source of marine methane to the atmosphere. Particularly high concentrations of this potent greenhouse gas are found in anoxic waters, but it remains unclear if and to what extent anaerobic methanotrophs mitigate the methane flux. Here we investigate the long-term dynamics in methanotrophic activity and the methanotroph community in the coastal oxygen minimum zone (OMZ) of Golfo Dulce, Costa Rica, combining biogeochemical analyses, experimental incubations and 16S rRNA gene sequencing over 3 consecutive years. Our results demonstrate a stable redox zonation across the years with high concentrations of methane (up to 1.7 μmol L⁻¹) in anoxic bottom waters. However, we also measured high activities of anaerobic methane oxidation in the OMZ core (rate constant, k, averaging 30 yr⁻¹ in 2018 and 8 yr⁻¹ in 2019–2020). The OPU3 and Deep Sea-1 clades of the Methylococcales were implicated as conveyors of the activity, peaking in relative abundance 5–25 m below the oxic–anoxic interface and in the deep anoxic water respectively. Although their genetic capacity for anaerobic methane oxidation remains unexplored, their sustained high relative abundance indicates an adaptation of these clades to the anoxic, methane-rich OMZ environment, allowing them to play major roles in mitigating methane fluxes.     

Anaerobic ammonium-oxidizing bacteria in marine environments: widespread occurrence but low diversity

Laboratory and field studies have indicated that anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. In this study 11 additional anoxic marine sediment and water column samples were studied to substantiate this claim. In a combined approach using the molecular methods, polymerase chain reaction (PCR), qualitative and quantitative fluorescence in situ hybridization (FISH), as well as (15)N stable isotope activity measurements, it was shown that anammox bacteria were present and active in all samples investigated. The anammox activity measured in the sediment samples ranged from 0.08 fmol cell(-1) day(-1) N(2) in the Golfo Dulce (Pacific Ocean, Costa Rica) sediment to 0.98 fmol cell(-1) day(-1) N(2) in the Gullmarsfjorden (North Sea, Sweden) sediment. The percentage of anammox cell of the total population (stained with DAPI) as assessed by quantitative FISH was highest in the Barents Sea (9% +/- 4%) and in most of the samples well over 2%. Fluorescence in situ hybridization and phylogenetic analysis of the PCR products derived from the marine samples indicated the exclusive presence of members of the Candidatus'Scalindua' genus. This study showed the ubiquitous presence of anammox bacteria in anoxic marine ecosystems, supporting previous observations on the importance of anammox for N cycling in marine environments.     

Relationship between Measures of Exposure to PCBs/Dioxins and Behavioral Effects in Recent Developmental Studies

This paper does not reflect official EPA policy. Epidemiological studies on the neurodevelopmental effects of exposure to PCBs initiated in the last decade have had the opportunity to take advantage of modern methodologies for the analysis of congeners of PCBs, dioxins, and related orga-nochlorine compounds. Each of these studies is a longitudinal prospective study, in which women were recruited during pregnancy and the children are being followed for at least several years after birth. The study from which the largest body of data has been published to date is being performed in the Netherlands, in which exposure to PCBs and related compounds is through the general food supply. Mother-infant pairs were recruited in two cities. Half of the infants were bottle-fed and half breast-fed in each city. Four PCB congeners (118, 138, 153, 180) were assessed in maternal and cord plasma, breast milk, and plasma of the child at 3.5 years. TEQ in breast milk was calculated based on PCDDs/PCDFs and dioxin-like PCBs. Various measures of in utero exposure were associated with suboptimal neurological status during infancy, whereas maternal plasma PCB concentration was associated with cognitive deficits (Kaufman scores) at 3.5 years of age. The child's concurrent plasma PCB levels and maternal PCB plasma levels independently predicted performance on various aspects of a vigilance task, and maternal and cord plasma levels predicted impairment of complex play behavior. Poor scores on behavioral ratings were associated with concurrent blood PCB concentrations in the child. A study in Oswego in Lake Ontario fish eaters includes mothers who never ate Great Lakes fish and mothers who consumed greater than 40 PCB-equivalent pounds of Lake Ontario fish over their lifetime. Sixty-eight PCB congeners were measured in cord blood. Suboptimal neurological status during infancy was associated with maternal fish consumption and highly chlorinated cord PCB levels, whereas deficits in short-term memory at 6 months and 1 year of age were associated with total chlorinated cord PCB levels. In a study in Germany of 171 mother-infant pairs, PCB congeners 138, 153, and 180 were measured in cord plasma and milk 2 weeks after birth; both measures are considered markers of in utero exposure. Suboptimal neurological status during infancy, decrements in Bayley scores at 30 months and Kaufman scores at 42 months were associated with PCBs in milk but not cord plasma. These studies, combined with data from previous studies, reveal a consistent relationship between PCB exposure and suboptimal neurological status during infancy, and cognitive deficits associated with in utero exposure. Data from the Dutch study revealed effects on other behavioral domains associated with concurrent (postnatal) exposure. Although it is not possible to identify specific congeners or groups of congeners that may be responsible for the neurotoxic effects observed in these studies, the TEQ approach was not particularly predictive for neurotoxic outcomes.     

Development and characterization of stable sediment-free anaerobic bacterial enrichment cultures that dechlorinate aroclor 1260

We have developed sediment-free anaerobic enrichment cultures that dechlorinate a broad spectrum of highly chlorinated polychlorinated biphenyls (PCBs). The cultures were developed from Aroclor 1260-contaminated sediment from the Housatonic River in Lenox, MA. Sediment slurries were primed with 2,6-dibromobiphenyl to stimulate Process N dechlorination (primarily meta dechlorination), and sediment was gradually removed by successive transfers (10%) to minimal medium. The cultures grow on pyruvate, butyrate, or acetate plus H(2). Gas chromatography-electron capture detector analysis demonstrated that the cultures extensively dechlorinate 50 to 500 mug/ml of Aroclor 1260 at 22 to 24 degrees C by Dechlorination Process N. Triplicate cultures of the eighth transfer without sediment dechlorinated 76% of the hexa- through nonachlorobiphenyls in Aroclor 1260 (250 mug/ml) to tri- through pentachlorobiphenyls in 110 days. At least 64 PCB congeners, all of which are chlorinated on both rings and 47 of which have six or more chlorines, were substrates for this dechlorination. To characterize the bacterial diversity in the enrichments, we used eubacterial primers to amplify and clone 16S rRNA genes from DNA extracted from cultures grown on acetate plus H(2). Restriction fragment length polymorphism analysis of 107 clones demonstrated the presence of Thauera-like Betaproteobacteria, Geobacter-like Deltaproteobacteria, Pseudomonas species, various Clostridiales, Bacteroidetes, Dehalococcoides of the Chloroflexi group, and unclassified Eubacteria. Our development of highly enriched, robust, stable, sediment-free cultures that extensively dechlorinate a highly chlorinated commercial PCB mixture is a major and unprecedented breakthrough in the field. It will enable intensive study of the organisms and genes responsible for a major PCB dechlorination process that occurs in the environment and could also lead to effective remediation applications.     

Reductive dechlorination of PCB-contaminated raisin river sediments by anaerobic microbial granules

A polychlorinated biphenyl (PCB)-dechlorinating anaerobic microbial consortium, developed in a granular form, demonstrated extensive dechlorination of PCBs present in Raisin River sediments at room (20 degrees to 22 degrees C) and at a relatively low (12 degrees C) temperature. Highly chlorinated PCB congeners were dechlorinated and less chlorinated compounds were produced. The homolog comparison showed that tri-, tetra-, penta-, hexa-, and heptachlorobiphenyl compounds decreased significantly, and mono- and dichlorobiphenyl compounds increased. After 32 weeks of incubation at 12 degrees C, the predominant less chlorinated products included 2-, 4-, 2-2/26-, 24-, 2-4-, 24-2-, 26-2-, and 26-4-CB. Among these, 24- and 24-2-CB did not accumulate at room temperature, suggesting a further dechlorination of these congeners. Predominantly meta dechlorination (i.e., pattern M) was catalyzed by the microbial consortium in the granules. Dechlorination in the control studies without granules was not extensive. This study is the first demonstration of enhanced reductive dechlorination of sediment PCBs by an exogenous anaerobic microbial consortium. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 182-190, 1997.     

Influence of Sediment Inflow on Phytoplankton Primary Productivity in Lake Tahoe (California-Nevada)

Light, nutrient concentrations and phytoplankton photosynthesis were studied in a Lake Tahoe sediment plume during maximum spring runoff. They were compared with conditions in clear lake waters not influenced by inlets. In the plume, nutrient concentrations increased in proportion to sediment density whereas light transmission of water was reduced with little effect on the spectral composition except for red light. Light inhibition of photosynthesis at the lake surface was less pronounced in the plume than in clear water and light limitation occurred more rapidly in deeper layers. Evidence from both lake experiments and laboratory bioassays suggests that iron had the greatest stimulatory effect on both photosynthetic activity and biomass growth at maximum sediment densities near the stream inlet. Because of less surface inhibition, photosynthetic light energy utilization efficiency was usually higher in the sediment plume which occurred in relatively shallow areas near the shore. In order to estimate overall effects of enhanced turbidity associated with nutrient loading on Lake Tahoe's primary productivity, profiles taken in shallow areas near the lakeshore were extrapolated to the maximum depth of photosynthesis. Light limitation would cause decreasing productivity, but nutrient stimulation would make this effect less pronounced. The overall effect would depend on the extent of sediment loading relative to nutrient loading.     

Potential for polychlorinated biphenyl biodegradation in sediments from Indiana Harbor and Ship Canal

Polychlorinated biphenyls (PCBs) are carcinogenic, persistent, and bioaccumulative contaminants that pose risks to human and environmental health. In this study, we evaluated the PCB biodegradation of sediments from Indiana Harbor and Ship Canal (IHSC), a PCB-contaminated site (average PCB concentration = 12,570 ng/g dw). PCB congener profiles and bacterial community structure in a core sediment sample (4.57 m long) were characterized. Analysis of vertical PCB congener profile patterns in sediment and pore water strongly suggests that in situ dechlorination occurred in sediments. However, 16S rRNA genes from putative PCB-dechlorinating Chloroflexi were relatively more abundant in upper 2 m sediments, as were genes indicative of aerobic biodegradation potential (i.e. biphenyl dioxygenase (bphA)). Characterization of the bacterial community by terminal restriction fragment length polymorphism and comparison of these with sediment and pore water PCB congener profiles with the Mantel test revealed a statistical correlation (p < 0.001). Sequences classified as Acinetobacter and Acidovorax were highly abundant in deep sediments. Overall, our results suggest that PCB dechlorination has already occurred, and that IHSC sediments have the potential for further aerobic and anaerobic PCB biodegradation.     

Distribution and Toxicity Risks of PCBs in the Tidal Flat Ecosystem Near the 37th PCBs Sealed Site on the Coast of Zhejiang Province,China

This study investigated the dioxin-like (DL) PCB concentration and congener distributions in water, sediment, and Boleophthalmus pectinirostris samples collected from a beach near the 37th PCBs sealed site (the hazardous waste storage site was sealed by Zhejiang Province Environmental Monitoring Center) of Zhejiang Province, China, so as to evaluate the harmful effects of PCBs waste sealed sites on the surrounding environment. The results showed that DL-PCBs were in all samples. For all samples, the detection ratio of the mono-ortho congener PCB118 and the non-ortho congener PCB81 reached 100%, and both of their contents correlated well with the total DL-PCBs contents. Levels of low-chloride congeners were higher in environmental samples, while the enrichment of the high-chloride congeners was higher in fish. The content of PCBs in B. pectinirostris was highly related to the sediment environment, thus B. pectinirostris could well indicate environmental PCBs pollution. Considering both of the PCBs content and toxic analysis, even after 4 years of being excavated and cleaned, water, sediment, and fish samples were still at a certain degree of toxicity risks. Some areas were revealed to have a high toxicity risk, suggesting this PCBs sealed site still posed toxicity risks to the surrounding tidal flat ecosystem and might potentially endanger animals and human health.     

Microbial reductive dechlorination of PCBs

Reductive dechlorination is an advantageous process to microorganisms under anaerobic conditions because it is an electron sink, thereby allowing reoxidation of metabolic intermediates. In some organisms this has been demonstrated to support growth. Many chlorinated compounds have now been shown to be reductively dechlorinated under anaerobic conditions, including many of the congeners in commercial PCB mixtures. Anaerobic microbial communities in sediments dechlorinate Aroclor at rates of 3 µg Cl/g sediment × week. PCB dechlorination occurs at 12° C, a temperature relevant for remediation at temperate sites, and at concentrations of 100 to 1000 ppm. The positions dechlorinated are usually meta > para > ortho. The biphenyl rings, and the mono-ortho- and diorthochlorobiphenyls were not degraded after a one year incubation. Hence subsequent aerobic treatment may be necessary to meet regulatory standards. Reductive dechlorination of Arochlors does reduce their dioxin-like toxicity as measured by bioassay and by analysis of the co-planar congeners. The most important limitation to using PCB dechlorination as a remediation technology is the slower than desired dechlorination rates and no means yet discovered to substantially enhance these rates. Long term enrichments using PCBs as the only electron acceptor resulted in an initial enhancement in dechlorination rate. This rate was sustained but did not increase in serial transfers. Bioremediation of soil contaminated with Aroclor 1254 from a transformer spill was dechlorinated by greater than 50% following mixing of the soil with dechlorinating organisms and river sediment. It is now reasonable to field test reductive dechlorination of PCBs in cases where the PCB concentration is in the range where regulatory standards may be directly achieved by dechlorination, where a subsequent aerobic treatment is feasible, where any co-contaminants do not pose an inhibitory problem, and where anaerobic conditions can be established.This paper was presented at the Pacific Basin Conference on Hazardous Waste, April, 1992, Bangkok, Thailand. Published by permission of the Pacific Basin Consortium for Hazardous Waste Research, East-West Center, Honolulu, HI     

Input of organochlorine compounds by snow to European high mountain lakes

1.  Persistent organic pollutants (POPs) can be trapped by and accumulate in cold regions. To understand POP accumulation in temperate high mountain lakes, we collected samples of snow from the catchments of several high mountain lakes in Europe.
2.  Organochlorine compounds (OCs) are regularly found in snow collected in European high mountain sites. Polychlorobiphenyls (PCBs) were found in all samples examined. Hexachlorocyclohexanes (HCHs) are also common whereas DDTs and hexachlorobenzene were found less frequently.
3.  Comparison of the concentrations of these pollutants in snow with OC levels in the waters of these lakes or atmospheric deposition during cold periods shows that the snowpack constitutes a significant seasonal PCB reservoir in all catchments and that snow trapping is a major mechanism for the incorporation of HCHs in the lakes situated in the coldest sites, e.g. Gossenköllesee in the Alps.
4.  Correlation of the concentrations of the PCB congeners in snow versus mean annual winter temperature shows higher accumulation at lower temperatures. The less volatile PCBs exhibit higher temperature dependences than the more volatile congeners. This trend differs from altitudinal dependences observed in other sites such as Canada and may be related to the specific range of winter temperature in each area of study.