Atmospheric deposition of persistent organic pollutants to the East Rongbuk Glacier in the Himalayas

To assess levels and seasonal trends of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in a high-altitude mountain region, a 2.1 m snowpack sample was collected from the East Rongbuk Glacier at 6572 ma.s.l. on Mt. Everest in September 2005. This snowpack covered a full year period from the fall of 2004 to the summer of 2005 and reflected the major meteorology of the monsoon and non-monsoon seasons. The most abundant compounds detected in the snow samples were γ-hexachlorocyclohexane (γ-HCH) and α-HCH with mean concentrations of 123 pg L^− 1 and 92 pg L^− 1, respectively. This is the first detection of these compounds in recent snow samples from the Himalayas. Backward air trajectory analysis indicated that the Himalayas could be influenced by the major HCH source regions in both India and China. Among the seven marker PCB congeners (PCB 28, 52, 101, 118, 138, 153, and 180) quantified, PCB 28 and PCB 52 were the only dominant PCB congeners detected, with mean concentrations of 17 pg L^− 1 and 6 pg L^− 1, respectively. In addition, DDT metabolites, p,p′-DDE and p,p′-DDD were detected in some snow samples and mean concentrations of DDTs were 24 pg L^− 1. Seasonal differences were observed for α- and γ-HCH concentrations increasing from the non-monsoon season to the monsoon season. Meanwhile, PCB 28 and HCB showed uniform variations with peak concentrations resulting from an effective scavenging by snowfalls between the monsoon and non-monsoon interval. Compared to other high mountain areas, the levels of POPs deposited into the East Rongbuk Glacier were relatively low, resulting from the highest altitude and remoteness from source regions.     

Trends of legacy and new persistent organic pollutants in the circumpolar arctic: Overview, conclusions, and recommendations

This article provides an overview of key findings in the reviews in this special issue on the assessment of persistent organic pollutants (POPs) under the Arctic Monitoring and Assessment Program (AMAP), identifies knowledge gaps, and presents conclusions and recommendations for future work. The articles in this special issue summarize the peer reviewed literature and selected technical reports on trends of concentrations and possible biological effects of POPs in the Arctic published up to early 2009.     

Gradient distribution of persistent organic contaminants along northern slope of central-Himalayas, China

High mountains may serve as condenser for persistent organic pollutants (POPs) and the vegetation in remote areas has been used as a means to characterized atmospheric concentrations of air pollutants. In this study, organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in Himalayan spruce needle samples from Zhangmu-Nyalam region (central-Himalayas) were analyzed and the altitudinal gradient of these pollutants was investigated. Total HCHs and DDTs concentration in needles were in the range of 1.3-2.9 ng g(-1) dry weight and 1.7-11 ng g(-1) dry weight, which were lower than concentrations reported in spruce needles from Alps, however higher than concentrations in conifer needles from mountain areas of Alberta. Total Himalayan spruce needle PAHs was below 600 ng g(-1) and fluorene, phenanthrene and acenaphthene were abundant individual compounds measured. The ratios of alpha-HCH/gamma-HCH in pine needles were similar with the usual values for technical HCH, implying technical HCHs might be used in this region. The high ratios of o-p'-DDT/p-p'-DDT and no p-p'-DDE measured in this study led to the suspicion that a new source of o-p'-DDT and/or p-p'-DDT existed in this region. In addition, higher ratios of low molecular weight-/high molecular weight-PAHs in this region indicated that petroleum combustion, vehicle emission and low-temperature combustion might be the major contributions of PAH source. To examine the POPs distillation, the analyte concentrations were correlated with altitude. The more volatile OCPs, alpha-HCH, gamma-HCH, aldrin and alpha-endosulfan positively correlated with altitude, however, less volatile OCPs (DDT and DDD) inversely related with elevation. Almost all PAHs detected in this area showed positive correlations with altitude. It is worthy to note that heavy PAHs (Benzo[k] fluoranthene and Benzo[a]anthracene) displayed positive correlation, which implied the sources of PAHs were near the sampling sites. The distillation of POPs was strongly affected by the proximity between sampling sites and contaminant sources. If the contaminant sources are close to the mountains, it may be the dominant factor that controls the concentration gradient.     

Levels, fluxes and time trends of persistent organic pollutants in Lake Thun, Switzerland: Combining trace analysis and multimedia modeling

Levels, mass fluxes, and time trends of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in Lake Thun, a peri-Alpine lake, are investigated. We present measurements of PBDEs and PCBs in air, lake water, lake sediment, and tributary water. These measurements are combined with a multimedia fate model, based on site-specific environmental parameters from the lake catchment. Measured loadings of PBDEs and PCBs in air and tributaries were used to drive the model. The model satisfactorily reproduces PBDE and PCB congener patterns in water and sediment, but it tends to yield concentrations in water below the measurements and concentrations in sediment exceeding the measurements. A sensitivity analysis reveals that partitioning of PBDEs and PCBs between the aqueous dissolved phase and suspended particulate matter in the water column strongly affects the model results, in particular the concentrations in water and sediment. For lower-brominated PBDEs, approximately 70% and 30% of input into the lake stems from atmospheric deposition and from tributaries, respectively. For heavier PBDEs and all PCBs, rivers appear to deliver the major load (64-92%). Waste water effluents are of minor importance. 50-90% of the total input is buried in the permanent sediment. Sediment burial makes PBDEs and PCBs less available for recycling in the environment, and reduces concentrations in the outflowing river. If use of deca-BDE increases in the future, levels in Lake Thun will follow the same trend. If the use and resulting environmental emissions decrease, concentrations in water will rapidly decline, according to our calculations, while sediment levels will decrease at a considerably slower rate.     

Soil burdens of persistent organic pollutants — Their levels, fate and risks: Part III. Quantification of the soil burdens and related health risks in the Czech Republic

A total number of 471 soil samples collected during the period of 1996-2006 from the agricultural and forest areas of the Czech Republic were analyzed for their content of persistent organic pollutants (POPs). Spatial variability of the POP concentrations was assessed using an IDW spatial GIS model analysis. For every grid of the network, resulting modeled levels of contamination allowed for estimation of the total burden of POPs in soils. Potential risks associated with contaminated soils were assessed as well. Database of the old ecological burdens counting 3061 sampling sites was used to adjust the model and incorporate the risks of heavily contaminated sites. The high levels of health risks were only found at less than 1% of the area of interest. The IDW modeling proved to be a useful tool for screening of the health risks in the large areas with scarce monitoring data. Presented approach can be applied in the risk management, to support an efficient targeting of the risk reduction measures, or to improve a design of the national monitoring.     

Relationship between persistent organic pollutants (POPs) and ranging patterns in common bottlenose dolphins (Tursiops truncatus) from coastal Georgia, USA

Bottlenose dolphins (Tursiops truncatus) are apex predators in coastal southeastern U.S. waters; as such they are indicators of persistent organic pollutants (POPs) in coastal ecosystems. POP concentrations measured in a dolphin's blubber are influenced by a number of factors, including the animal's sex and ranging pattern in relation to POP point sources. This study examined POP concentrations measured in bottlenose dolphin blubber samples (n = 102) from the Georgia, USA coast in relation to individual ranging patterns and specifically, distance of sightings from a polychlorinated biphenyl (PCB) point source near Brunswick, Georgia. Dolphin ranging patterns were determined based upon 5 years of photo-identification data from two field sites approximately 40 km apart: (1) the Brunswick field site, which included the Turtle/Brunswick River Estuary (TBRE), and (2) the Sapelo field site, which included the Sapelo Island National Estuarine Research Reserve (SINERR). Dolphins were categorized into one of three ranging patterns from photo-identification data. Individuals with sighting histories exclusively within one of the defined field sites were considered to have either Brunswick or Sapelo ranging patterns. Individuals sighted in both field sites were classified as having a Mixed ranging pattern. Brunswick males had the highest concentrations of PCBs reported for any marine mammal. The pattern of PCB congeners was consistent with Aroclor 1268, a highly chlorinated PCB mixture associated with a Superfund site in Brunswick. PCB levels in Sapelo males were lower than in Brunswick males, but comparable to the highest levels measured in other dolphin populations along the southeastern U.S. Female dolphins had higher Aroclor 1268 proportions than males, suggesting that the highly chlorinated congeners associated with Aroclor 1268 may not be offloaded through parturition and lactation, as easily as less halogenated POPs. Individuals sighted farther from the Superfund point source had lower Aroclor 1268 proportions.     

Evaluation of total lipids using enzymatic methods for the normalization of persistent organic pollutant levels in serum

The human exposure to persistent organic pollutants (POPs) is conveniently assessed through analysis of blood serum or plasma and the POPs concentrations are traditionally expressed on a lipid weight basis. Enzymatic determinations of total lipid (TL) content in serum, which imply the measurement of individual lipid classes, such as triglycerides (TG), cholesterol (CHOL) and phospholipid (PL), use small amounts of serum/plasma (<100 microl). These have also become a more precise and less laborious alternative for the gravimetric lipid determinations which were preferred in the past. However, PL are not routinely measured in most clinical laboratories and therefore, TL values are often predicted from formulas based on measurements of only TG and CHOL. In the present study, a large data set (n=483) from Belgian, Swedish and Norwegian populations was used to compute a new formula for TL [TL=1.33*TG+1.12*CHOL+1.48 (g/l)] by means of multiple linear regression. A very good correlation (r=0.949, p<0.001) was found between TL values calculated with the proposed formula and TL values obtained by summation of TG, CHOL and PL. Statistically different values of TL were computed when different previously published formulas were compared, which can have a strong influence on the calculation of lipid-normalized concentrations of POPs. Nevertheless, TL values derived using a mathematical formula which includes only TG and CHOL will be less accurate than TL values obtained by summation of TG, CHOL and PL, which should be the calculation method of choice if PL measurements are available.     

Concentration of selected persistent organic pollutants in blood from delivering women in South Africa

Environmental exposure to persistent organic pollutants (POPs) may cause detrimental health effects in the population with the developing foetus and infants being at highest risk. This paper reports on the findings of the pilot study that took place in seven geographical regions of South Africa, 96 pregnant women admitted for delivery participated in the study. The following selected POPs were analysed in maternal plasma: 15 polychlorinated biphenyls (PCBs) congeners (IUPAC No. 28, 52, 99, 101, 105, 118, 138, 149, 153, 156, 170, 180, 183, 187, 194); six DDT metabolites (dichlordiphenyltrichloroethane p,p'-DDT and o,p'-DDT; diphenyldichloroethylene p,p'-DDE and o,p'-DDE, dichlorophenylethane p,p'-DDD o,p'-DDD) and other pesticides such as hexachlorocyclohexanes (α-HCH, β-HCH, γ-HCH), hexachlorobenzene (HCB), heptachlor, chlordanes (t-CD and c-CD), nanochlors (t-NC and c-NC) and mirex.The overall results showed large regional differences with the rural site having the lowest levels for all measured contaminants. The levels of PCB congeners were found to be low in all samples and across all sites. DDT metabolites were detected in most participants of this study and large regional differences were evident. Two malaria endemic sites, where indoor residual spraying (IRS) with DDT takes place to control malaria vector, were included in the study. The highest levels of DDTs were measured in the coastal malaria site (Indian Ocean) with geometric means of 5177 ng/g lipid and 1797 ng/g lipid for p,p'-DDE and p,p'-DDT, and 1966 ng/g lipid and 726 ng/g lipid for p,p'-DDE and p,p'-DDT in inland malaria site. γ-HCH was found to be elevated overall, except for the urban community; the highest levels were measured in the inland and coastal malaria sites. p,p'-DDT and γ-HCH were however not correlated, indicating different sources. The high DDT levels in the malaria spraying regions as well as the elevated γ-HCH levels are of concern and call for extended monitoring of women and children in selected regions.     

Biodegradation of persistent polar pollutants in wastewater: comparison of an optimised lab-scale membrane bioreactor and activated sludge treatment

The biodegradation of selected non-adsorbing persistent polar pollutants (P(3)) during wastewater (WW) treatment was studied by comparing a lab-scale membrane bioreactor (MBR) running in parallel to activated sludge treatment (AST). The investigated P(3) are relevant representatives or metabolites from the compound classes: pesticides, pharmaceuticals, insect repellents, flame retardants and anionic surfactants. Analyses of all these P(3) at low ng L(-1) levels with sufficient standard deviations was performed in WW influents and effluents. Non-degradable micropollutants, such as EDTA and carbamazepine were not eliminated at all during WW treatment by any technique. However, the MBR showed significant better removals compared to AST for the investigated poorly biodegradable P(3), such as diclofenac, mecoprop and sulfophenylcarboxylates. An application of such an in terms of sludge retention time optimised MBR may lead to a reduction of these P(3) in the watercycle.     

Atmospheric monitoring of organic pollutants in the Arctic under the Arctic Monitoring and Assessment Programme (AMAP): 1993-2006

Continuous and comparable atmospheric monitoring programs to study the transport and occurrence of persistent organic pollutants (POPs) in the atmosphere of remote regions is essential to better understand the global movement of these chemicals and to evaluate the effectiveness of international control measures. Key results from four main Arctic research stations, Alert (Canada), Pallas (Finland), Storhofdi (Iceland) and Zeppelin (Svalbard/Norway), where long-term monitoring have been carried out since the early 1990s, are summarized. We have also included a discussion of main results from various Arctic satellite stations in Canada, Russia, US (Alaska) and Greenland which have been operational for shorter time periods. Using the Digital Filtration temporal trend development technique, it was found that while some POPs showed more or less consistent declines during the 1990s, this reduction is less apparent in recent years at some sites. In contrast, polybrominated diphenyl ethers (PBDEs) were still found to be increasing by 2005 at Alert with doubling times of 3.5 years in the case of deca-BDE. Levels and patterns of most POPs in Arctic air are also showing spatial variability, which is typically explained by differences in proximity to suspected key source regions and long-range atmospheric transport potentials. Furthermore, increase in worldwide usage of certain pesticides, e.g. chlorothalonil and quintozene, which are contaminated with hexachlorobenzene (HCB), may result in an increase in Arctic air concentration of HCB. The results combined also indicate that both temporal and spatial patterns of POPs in Arctic air may be affected by various processes driven by climate change, such as reduced ice cover, increasing seawater temperatures and an increase in biomass burning in boreal regions as exemplified by the data from the Zeppelin and Alert stations. Further research and continued air monitoring are needed to better understand these processes and its future impact on the Arctic environment.     

Trends in organic pollutants and lipids in juvenile Snake River spring Chinook salmon with different outmigrating histories through the Lower Snake and Middle Columbia Rivers

A three-year field study was conducted from 2006 to 2008 to monitor the spatial and temporal trends of organic pollutants in migrating juvenile Snake River spring Chinook salmon (Oncorhynchus tshawytscha) sampled from the Lower Snake and Middle Columbia River Basins. Specifically, hatchery-reared juvenile salmon were monitored as they navigated the Federal Columbia River Power System (FCRPS) by either transport barge (Barged) or remained in the river (In-River) from Lower Granite Dam to a terminal collection dam, either John Day Dam or Bonneville Dam. Levels of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine (OC) pesticides were detected in the bodies of both In-River and Barged salmon during the 2006, 2007 and 2008 outmigrating season. At the terminal dam, In-River fish had greater concentrations of persistent organic pollutants POPs than Barged salmon. Of the POPs detected, dichlorodiphenyltrichloroethanes (DDTs) were found at the greatest concentrations in the salmon bodies. These elevated lipid-normalized concentrations in the In-River fish were due to lipid depletion in all years as well as increased exposure to POPs in some years as indicated by an increase in wet weight contaminant concentrations. Salmon were also exposed to polycyclic aromatic hydrocarbons (PAHs) as indicated by the phenanthrene (PHN) signal for biliary fluorescent aromatic compounds (FACs) at the hatcheries or prior to Lower Granite Dam. There were detectable levels of biliary FACs as fish migrated downstream or were barged to the terminal dam. Therefore, the potential exists for these organic pollutants and lipid levels to cause adverse effects and should be included as one of the variables to consider when examining the effects of the FCRPS on threatened and endangered juvenile salmon.     

环境中金属离子与有机污染物复合污染研究进展

金属离子与有机污染物可通过多种方式同时存在于环境中,形成复合污染。由于金属离子与有机污染物的相互作用,二者的物理化学性质、迁移转化规律以及生态毒性效应都发生了变化,给污染物的水处理过程以及污染物的生态毒性评估带来极大的挑战。综述了环境中金属-有机物复合污染的来源、金属离子与有机污染物之间的相互作用、共存对二者去除效率的影响以及复合污染的生态毒性研究,以期为复合污染的防治与处理工艺研究提供参考。     

Persistent organic pollutants in fish tissue in the mid-continental great rivers of the United States

Great rivers of the central United States (Upper Mississippi, Missouri, and Ohio rivers) are valuable economic and cultural resources, yet until recently their ecological condition has not been well quantified. In 2004-2005, as part of the Environmental Monitoring and Assessment Program for Great River Ecosystems (EMAP-GRE), we measured legacy organochlorines (OCs) (pesticides and polychlorinated biphenyls, PCBs) and emerging compounds (polybrominated diphenyl ethers, PBDEs) in whole fish to estimate human and wildlife exposure risks from fish consumption. PCBs, PBDEs, chlordane, dieldrin and dichlorodiphenyltrichloroethane (DDT) were detected in most samples across all rivers, and hexachlorobenzene was detected in most Ohio River samples. Concentrations were highest in the Ohio River, followed by the Mississippi and Missouri Rivers, respectively. Dieldrin and PCBs posed the greatest risk to humans. Their concentrations exceeded human screening values for cancer risk in 27-54% and 16-98% of river km, respectively. Chlordane exceeded wildlife risk values for kingfisher in 11-96% of river km. PBDE concentrations were highest in large fish in the Missouri and Ohio Rivers (mean > 1000 ng g^− 1 lipid), with congener 47 most prevalent. OC and PBDE concentrations were positively related to fish size, lipid content, trophic guild, and proximity to urban areas. Contamination of fishes by OCs is widespread among great rivers, although exposure risks appear to be more localized and limited in scope. As an indicator of ecological condition, fish tissue contamination contributes to the overall assessment of great river ecosystems in the U.S.     

Tests of the fidelity of lake sediment core records of mercury deposition to known histories of mercury contamination

There has been recent controversy over the discrimination between natural and anthropogenic loadings of mercury to lakes. Sediment core profiles have been interpreted as evidence that inputs to lakes have increased. Some investigators have argued, however, that mercury may be sufficiently mobile in sediments to generate profiles that are misinterpreted as historical records. This argument can be tested where the histories of inputs of mercury are known independently from other kinds of information. We have such cases in Canadian lakes and we have been able to assemble sediment core records for comparison with known source histories. Three cases are represented by Clay Lake in Ontario where the source was a chlor-alkali plant with a known history of mercury discharges, Giauque Lake in the Northwest Territories where mercury was used at a gold mine to extract gold from ore, and Stuart Lake in British Columbia where a mercury mine operated for a known period at Pinchi Lake, the lake immediately upstream from Stuart Lake. In these cases lake sediment cores were dated using lead-210 and cesium-137 and then slices were analysed for mercury. The histories of mercury deposition derived from the cores agreed well with the known histories of inputs.     

Surfactant-coated aluminum hydroxide for the rapid removal and biodegradation of hydrophobic organic pollutants in water

The removal of hydrophobic organic pollutants in water to surfactant-coated aluminum hydroxide [surfactant-Al(OH)₃] was investigated. Anionic surfactants such as sodium dodecyl sulfate (SDS), sodium bis(2-ethylhexyl)sulfosuccinate (AOT), and sodium oleate were sorbed on positively charged aluminum hydroxide at pH 7 and formed hydrophobic aggregates that can incorporate hydrophobic organic pollutants in water. Because of the hydrophobic interaction and decrease in the positive charge, surfactant-Al(OH)₃ was coagulated into precipitates that can readily be separated from water. Hydrophobic organic pollutants such as alkylphenols, polycyclic aromatic hydrocarbons, estrogens, chlorinated antifungals, and pesticides were well collected to the precipitates and thus efficiently removed from water. The collection of hydrophobic organic pollutants was correlated to their aqueous-octanol distribution coefficient. The decomposition of hydrophobic organic pollutants was examined using a bacterial agent (Bacillus subtilis). Hydrophobic organic compounds collected to AOT-Al(OH)₃ or sodium oleate-Al(OH)₃ were insufficiently decomposed. On the other hand, nonylphenol, octylphenol, and pendimethalin collected to SDS-Al(OH)₃ were decomposed within 1 week. The decomposition was accelerated by the collection to SDS-Al(OH)₃.     

Sediment mercury dynamics and historical trends of mercury deposition in the St. Lawrence River area of concern near Cornwall, Ontario, Canada

The St. Lawrence River near Cornwall, Ontario was designated an Area of Concern by the International Joint Commission in 1985. Sediments from this area have historically been contaminated with mercury (Hg), and although concentrations have decreased since the 1970s, they still remain high. Nine sediment cores were collected from three sites within the Area of Concern in 2004/05 to determine the variability in historical profiles of Hg deposition to the river. Sediment and pore water phases were analyzed for total mercury (THg) and methyl mercury (MeHg) and cores were analyzed for ²¹⁰Pb to determine chronologies of sedimentation at these sites. Mercury diffusion rates in pore waters within the sediment column were determined to be very low (between 0 and 2.15 ng cm^− 2 year^− 1, n = 3) compared to the recent Hg sedimentation rates at these sites (183 ± 30 ng cm^− 2 year^− 1 SE, n = 9) determined by multiplying surface Hg concentrations with ²¹⁰Pb-derived sedimentation rates. These results indicate that Hg profiles in these cores accurately depict historical releases of Hg to the river bed. The influence of federal regulations in the early 1970s to restrict Hg emissions to the river was apparent in these dated sediment cores, as were the closures of several local industries in the mid 1990s. Mercury accumulation rates prior to 1970 were 60 times higher than those occurring after 1995. Methyl mercury showed surface enrichment in most of these sediment cores providing evidence that mercury methylation occurred most rapidly near the sediment surface.     

Life history as a source of variation for persistent organic pollutant (POP) patterns in a community of common bottlenose dolphins (Tursiops truncatus) resident to Sarasota Bay, FL

As apex predators within coastal ecosystems, bottlenose dolphins (Tursiops truncatus) are prone to accumulate complex mixtures of persistent organic pollutants (POPs). While substantial variations in POP patterns have been previously observed in dolphin populations separated across regional- and fine-scale geographic ranges, less is known regarding the factors influencing contaminant patterns within localized populations. To assess the variation of POP mixtures that occurs among individuals of a population, polychlorinated biphenyl (PCB), organochlorine pesticide (OCP) and polybrominated diphenyl ether (PBDE) concentrations were measured in blubber and milk of bottlenose dolphins resident to Sarasota Bay, FL, and principal components analysis (PCA) was used to explain mixture variations in relation to age, sex and reproductive maturity. PCA demonstrated significant variations in contaminant mixtures within the resident dolphin community. POP patterns in juvenile dolphins resembled patterns in milk, the primary diet source, and were dominated by lower-halogenated PCBs and PBDEs. A significant correlation between principal component 2 (PC2) and age in male dolphins indicated that juvenile contaminant patterns gradually shifted away from the milk-like pattern over time. Metabolically-refractory PCBs significantly increased with age in male dolphins, whereas PCBs subject to cytochrome p450 1A1 metabolism did not, suggesting that changes in male POP patterns likely resulted from the selective accumulation of persistent POP congeners. Changes to POP patterns were gradual for juvenile females, but changed dramatically at reproductive maturity and gradually shifted back towards pre-parturient profiles thereafter. Congener-specific blubber/milk partition coefficients indicated that lower-halogenated POPs were selectively offloaded into milk and changes in adult female contaminant profiles likely resulted from the offloading of these compounds during the first reproductive event and their gradual re-accumulation thereafter. Overall, these results indicate that significant variations in contaminant mixtures can exist within localized populations of bottlenose dolphins, with life history factors such as age and sex driving individual differences.     

Influences of iron, manganese, and dissolved organic carbon on the hypolimnetic cycling of amended mercury

The biogeochemical cycling of iron, manganese, sulfide, and dissolved organic carbon were investigated to provide information on the transport and removal processes that control the bioavailability of isotopic mercury amended to a lake. Lake profiles showed a similar trend of hypolimnetic enrichment of Fe, Mn, DOC, sulfide, and the lake spike ((202)Hg, purity 90.8%) and ambient of pools of total mercury (HgT) and methylmercury (MeHg). Hypolimnetic enrichment of Fe and Mn indicated that reductive mobilization occurred primarily at the sediment-water interface and that Fe and Mn oxides were abundant within the sediments prior to the onset of anoxia. A strong relationship (r(2)=0.986, n=15, p<0.001) between filterable Fe and Mn indicated that reduction of Fe and Mn hydrous oxides in the sediments is a common in-lake source of Fe(II) and Mn(II) to the hypolimnion and that a consistent Mn:Fe mass ratio of 0.05 exists in the lake. A strong linear relationship of both the filterable [Fe] (r(2)=0.966, n=15, p<0.001) and [Mn] (r(2)=0.964, n=15, p<0.001) to [DOC] indicated a close linkage of the cycles of Fe and Mn to DOC. Persistence of iron oxides in anoxic environments suggested that DOC was being co-precipitated with Fe oxide and released into solution by the reductive dissolution of the oxide. The relationship between ambient and lake spike HgT (r(2)=0.920, n=27, p<0.001) and MeHg (r(2)=0.967, n=23, p<0.001) indicated that similar biogeochemical processes control the temporal and spatial distribution in the water column. The larger fraction of MeHg in the lake spike compared to the ambient pool in the hypolimnion suggests that lake spike may be more available for methylation. A linear relationship of DOC to both filterable ambient HgT (r(2)=0.406, n=27, p<0.001) and lake spike HgT (r(2)=0.314, n=15, p=0.002) suggest a role of organic matter in Hg transport and cycling. However, a weak relationship between the ambient and lake spike pools of MeHg to DOC indicated that other processes have a major role in controlling the abundance and distribution of MeHg. Our results suggest that Fe and Mn play important roles in the transport and cycling of ambient and spike HgT and MeHg in the hypolimnion, in part through processes linked to the formation and dissolution of organic matter-containing Fe and Mn hydrous oxides particles.     

Geography and stage of development affect persistent organic pollutants in stranded and wild-caught harbor seal pups from central California

Persistent organic pollutants have been associated with disease susceptibility and decreased immunity in marine mammals. Concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), chlordanes (CHLDs), and hexachlorocyclohexane isomers (HCHs) were evaluated in terms of stage of development and likely exposure routes (in utero, suckling, fasting) in the blubber of 202 stranded and wild-caught, primarily young of the year (n = 177), harbor seals (Phoca vitulina) in the central California coast. This is the first report of HCH concentrations in the blubber of California seals. Lipid normalized concentrations ranged from 200 to 330,000 ng/g for sum PCBs, 320-1,500,000 ng/g for sum DDTs, 23-63,000 ng/g for sum PBDEs, 29-29,000 ng/g for sum CHLDs, and 2-780 ng/g for sum HCHs. The highest concentrations were observed in harbor seal pups that suckled in the wild and then lost mass during the post-weaning fast. Among the pups sampled in the wild and those released from rehabilitation, there were no differences in mass, blubber depth, or percent lipid although contaminant concentrations were significantly higher in the pups which nursed in the wild. When geographic differences were evaluated in a subset of newborn animals collected near their birth locations, the ratio of sum DDTs to sum PCBs was significantly greater in samples from an area with agricultural inputs (Monterey), than one with industrial inputs (San Francisco Bay). A principal components analysis distinguished between seals from San Francisco Bay and Monterey Bay based on specific PCB and PBDE congeners and DDT metabolites. These data illustrate the important influence of life stage, nutritional status, and location on blubber contaminant levels, and thus the need to consider these factors when interpreting single sample measurements in marine mammals.