Fluxes Of Persistent Organic Pollutants Research Articles

Capping fiberbank sediments to reduce persistent organic pollutants (POPs) fluxes: A large-scale laboratory column experiment

Deposits of contaminated wood fiber waste (fiberbanks), originating from sawmills and pulp and paper industries, have been found in the aquatic environment in boreal countries. In-situ isolation capping has been proposed as a remediation solution because it has the potential to prevent dispersal of persistent organic pollutants (POPs) from this type of sediment. However, knowledge about the performance of such caps when placed on very soft (unconsolidated), gaseous organic rich sediment is scarce. We investigated the effectiveness of conventional in-situ capping to limit POPs fluxes to the water column from contaminated fibrous sediments that produce gas. A controlled, large-scale laboratory column (40 cm diameter, 2 m height) experiment was performed over 8 months to study changes in sediment-to-water fluxes of POPs and particle resuspension before and after capping the sediment with crushed stones (≥4 mm grain size). Two different cap thicknesses were tested (20 and 45 cm) on two types of fiberbank sediment with different fiber type composition. Results showed that capping fiberbank sediment with a 45 cm gravel cap reduced the sediment-to-water flux by 91–95% for p,p’-DDD, o,p’-DDD, by 39–82% for CB-101, CB-118, CB-138, CB-153, CB-180 and by 12–18% for HCB, whereas for less hydrophobic PCBs, capping was largely ineffective (i.e. CB-28 and CB-52). Although cap application caused particle resuspension, the long-term effect of the cap was reduced particle resuspension. On the other hand, substantial sediment consolidation released large volumes of contaminated pore water into the overlying water body. Importantly, both sediment types produced large amount of gas, observed as gas voids forming inside the sediment and gas ebullition events, which increased pore water advection and affected the structural integrity of the cap. This may limit the practical applicability of this method on fiberbank sediments.

Diffusive fluxes of persistent organic pollutants between Arctic atmosphere, surface waters and sediments

Arctic communities are disproportionately exposed to pollutants from sources including global atmospheric transport and formerly used defense sites (FUDS). The effects of climate change and increasing development in the Arctic have the potential to exacerbate this problem. Yupik People of Sivuqaq, or St Lawrence Island, Alaska are one such community with documented exposures to pollutants from FUDS, and their traditional lipid-rich foods such as blubber and rendered oils of marine mammals. Troutman Lake, adjacent to the Yupik community of Gambell, Alaska, was used as a disposal site during the decommission of the adjacent FUDS, leading to community concern about exposure to military pollution and intrusion from historic local dump sites. In collaboration with a local community group, this study utilized passive sampling devices deployed in Troutman Lake. Air, water and sediment deployed samplers were analyzed for unsubstituted and alkylated polycyclic aromatic hydrocarbons (PAHs), brominated and organophosphate flame retardants and polychlorinated biphenyls (PCBs). PAH concentrations were low and comparable to other remote/rural locations. PAHs were generally in deposition from the overlying atmosphere into Troutman Lake. Of the flame retardants, brominated diphenyl ether-47 was detected in all surface water samplers while triphenyl phosphate was detected in all environmental compartments. Both were at concentrations equivalent or lower than other remote locations. Of particular interest, we measured higher atmospheric concentrations of tris(2-chloroethyl) phosphate (TCEP) (0.75–2.8 ng/m3) than previously reported in the literature for remote Arctic sites (<0.017–0.56 ng/m3). TCEP was found to be in deposition to Troutman Lake at magnitudes from 290 to 1300 ng/m2/day. No PCBs were detected in this study. Our findings demonstrate the relevance of both modern and legacy chemicals from local and global sources. These results help us to understand the fate of anthropogenic contaminants in dynamic Arctic systems providing valuable data for communities, policy makers and scientists.

Spatial distribution, deposition flux, and environmental impact of typical persistent organic pollutants in surficial sediments in the Eastern China Marginal Seas (ECMSs)

High emissions of synthetic compounds are damaging the marine environment and threatening human health. This study represents the first extensive and comprehensive analysis of three typical persistent organic pollutants (POPs), i.e., organochlorine pesticides (n = 228), perfluoroalkyl substances (n = 202), and short-chain chlorinated paraffins (n = 162), using a highly resolved spatial dataset. The results revealed the complex distribution of POPs in the Eastern China Marginal Seas (ECMSs). POPs in the surface sediments of the ECMSs showed spatial heterogeneity, with high levels observed mainly in areas with fine-grained sediments (e.g., the Yellow River and Changjiang River estuaries and the central south Yellow Sea). Strong positive correlations were identified between POP concentration and sediment grain size/components/longitude/latitude in the ECMSs, suggesting that POP distribution was significantly influenced by river input and regional hydrodynamics. The annual deposition fluxes of POPs in the ECMSs were also calculated and high values were recorded in the Yellow River Estuary and East China Sea. Human-induced changes in the catchments could affect the fate of POPs in the ECMSs and other river-dominated marginal seas worldwide. Our findings highlight concerns regarding local aquaculture and provide a basis for government decision-making. We also suggest the need for increased attention to be paid to the effects of marine organic pollution on aquaculture on a global scale.

Recent history of persistent organic pollutants (PAHs, PCBs, PBDEs) in sediments from a large tropical lake.

210Pb-dated sediment cores and surface sediments from Lake Chapala (LC), Mexico, were analyzed to assess the temporal trends in concentrations and fluxes of persistent organic pollutants (POPs: PAHs, PCBs and PBDEs). Total sediment concentrations of PAHs (95-1,482 ng g-1), PCBs (9-27 ng g-1) and PBDEs (0.2-2.5 ng g-1) were indicative of moderate to intense contamination. The POP concentrations have progressively increased since the 1990s. The light molecular weight PAHs, and the prevalence of PCB congeners with low-chlorination levels (e.g., di- to tri-CB) and low-to medium-brominated (tri- to penta-BDE) PBDEs in most sections of the sediment profiles, suggested that these POPs have most likely reached these sediments by long-range atmospheric transport from distant sources; although the significant presence of heavier PAH, PCB and PBDE congeners in the topmost sediments, indicate that other nearby and local sources (soil erosion from the catchment, urban and industrial wastewaters discharges, as well as navigation) might have also contributed to the recent input of POPs to LC. Taking into account the relevance of LC as regional freshwater supply and commercial fishing ground, the potential risk posed by the organic contaminated sediments to the biota and human population should not be underestimated.

Persistent organic pollutants in krill from the Bellingshausen, South Scotia, and Weddell Seas

Persistent organic pollutants (POPs) reach Antarctica through atmospheric transport, oceanic currents, and to minor extent, by migratory animals. The Southern Ocean is a net sink for many POPs, with a key contribution of the settling fluxes of POPs bound to organic matter (biological pump). However, little is known about POP transfer through the food web in the Southern Ocean and Antarctic waters, where krill is an important ecological node. In this study, we assessed the occurrence of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) in Antarctic krill (Euphausia superba) from the Bellingshausen, South Scotia and Weddell Seas around the Antarctic Peninsula. The concentrations of PCDD/Fs, PBDEs and PCBs in krill showed a large variability and the average were higher (generally within a factor 3) than those previously reported for eastern Antarctica. This result highlights regional differences related to atmospheric transport and deposition, and also probable regional sources due to human activities. Bioaccumulation and biomagnification factors for PCBs in krill were estimated using previously reported phytoplankton and seawater concentrations for this region. These suggested a near water-krill equilibrium for PCBs, which was not observed for water-phytoplankton partitioning. The estimated removal settling fluxes of PCBs due to the biological pump were several orders of magnitude higher than the estimated fluxes of PCBs transferred from phytoplankton to krill.

Comparison of eddy covariance and modified Bowen ratio methods for measuring gas fluxes and implications for measuring fluxes of persistent organic pollutants

Abstract. Semi-volatile persistent organic pollutants (POPs) cycle between the atmosphere and terrestrial surfaces; however measuring fluxes of POPs between the atmosphere and other media is challenging. Sampling times of hours to days are required to accurately measure trace concentrations of POPs in the atmosphere, which rules out the use of eddy covariance techniques that are used to measure gas fluxes of major air pollutants. An alternative, the modified Bowen ratio (MBR) method, has been used instead. In this study we used data from FLUXNET for CO2 and water vapor (H2O) to compare fluxes measured by eddy covariance to fluxes measured with the MBR method using vertical concentration gradients in air derived from averaged data that simulate the long sampling times typically required to measure POPs. When concentration gradients are strong and fluxes are unidirectional, the MBR method and the eddy covariance method agree within a factor of 3 for CO2, and within a factor of 10 for H2O. To remain within the range of applicability of the MBR method, field studies should be carried out under conditions such that the direction of net flux does not change during the sampling period. If that condition is met, then the performance of the MBR method is neither strongly affected by the length of sample duration nor the use of a fixed value for the transfer coefficient.

Assessing the influence of local sources on POPs in atmospheric depositions and sediments near Trento (Italy)

The content of five classes of Persistent Organic Pollutants (POPs) in the atmospheric depositions and sediments of an area interested by a steelmaking plant, a state highway and urban settlements were investigated. Samples were collected through a wet and dry sampler onto the roof of a primary school or core drilled from the sediments of a nearby pond and analyzed for PCDD/Fs, PCBs, PAHs, PBDEs and PCNs in order to assess the role of different sources on direct emissions in atmosphere and transfer to other environmental compartments. The method was tested with reference materials, laboratory and field blanks. The results show higher fluxes of POPs in winter depositions, with PAH levels up to 6500 ng m−2 d−1. Patterns and diagnostic ratios suggest that the main sources are fuel and wood combustion. PCDD/Fs are present at background level, with maximum total fluxes of 17 pg m−2 d−1 in depositions and concentrations of 7 pg g−1 in sediments. All concentrations peak at mid-level in the sediment core and then decrease towards surface, as an effect of regulatory limitations and update to modern industrial technologies.

Long-range atmospheric transport of persistent organic pollutants to remote lacustrine environments

Concentrations, temporal trends and fluxes of persistent organic pollutants (POPs: PAHs, PCBs and PBDEs) were determined in soil and 210Pb-dated sediment cores from remote lacustrine environments (El Tule and Santa Elena lakes) in rural areas of Central Mexico. In both areas, the concentrations of target analytes in soil and sediment samples were comparable and indicative of slightly contaminated environments. The prevalence of low-molecular-weight PAHs in soils suggested their mainly atmospheric origin, in contrast to the aquatic sediments where runoff contribution was also significant. Increasing contamination trends of PCBs and PBDEs were evident, showing maximum fluxes of 4.8±2.1 and 0.3±0.1ngcm−2a−1 for PCBs and PBDEs, respectively. The predominance of lower-brominated PBDEs and lower-chlorinated PCBs in soils and sediments indicated that their presence is mostly due to long-range atmospheric transport.

Calculating the Diffusive Flux of Persistent Organic Pollutants between Sediments and the Water Column on the Palos Verdes Shelf Superfund Site Using Polymeric Passive Samplers

Passive samplers were deployed to the seafloor at a marine Superfund site on the Palos Verdes Shelf, California, USA, and used to determine water concentrations of persistent organic pollutants (POPs) in the surface sediments and near-bottom water. A model of Fickian diffusion across a thin water boundary layer at the sediment-water interface was used to calculate flux of contaminants due to molecular diffusion. Concentrations at four stations were used to calculate the flux of DDE, DDD, DDMU, and selected PCB congeners from sediments to the water column. Three passive sampling materials were compared: PE strips, POM strips, and SPME fibers. Performance reference compounds (PRCs) were used with PE and POM to correct for incomplete equilibration, and the resulting POP concentrations, determined by each material, agreed within 1 order of magnitude. SPME fibers, without PRC corrections, produced values that were generally much lower (1 to 2 orders of magnitude) than those measured using PE and POM, indicating that SPME may not have been fully equilibrated with waters being sampled. In addition, diffusive fluxes measured using PE strips at stations outside of a pilot remedial sand cap area were similar to those measured at a station inside the capped area: 240 to 260 ng cm(-2) y(-1) for p,p'-DDE. The largest diffusive fluxes of POPs were calculated at station 8C, the site where the highest sediment concentrations have been measured in the past, 1100 ng cm(-2) y(-1) for p,p'-DDE.

Critical evaluation of a new passive exchange-meter for assessing multimedia fate of persistent organic pollutants at the air-soil interface

A new passive exchange meter (PEM) to measure inter-compartment fluxes of persistent organic pollutants (POPs) at the interface between soil and the atmosphere is described. The PEM uses labeled reference compounds (RC) added in-situ to vegetation litter deployed in open cylinders designed to trap the vertical downward export of the RCs while allowing free exchange of POPs between litter and air. Fluxes of native compounds (bulk deposition, volatilization and downward export) are quantitatively tracked. One scope of the PEM is to investigate the influence of biogeochemical controls on contaminant re-mobilization. The PEM performance was tested in a subtropical forest by comparing measurements under dense canopy and in a canopy gap; conditions in which deposition and turn-over of organic matter (OM) occur at different rates. Significant differences in fate processes were successfully detected. Surprisingly, mobilization by leaching of more hydrophobic compounds was higher under canopy, possibly as a result of canopy mediated enhancement of OM degradation.

Development of a Soil Fugacity Sampler for Determination of Air−Soil Partitioning of Persistent Organic Pollutants under Field Controlled Conditions

Soils are the main reservoir of persistent organic pollutants (POPs) and thus air-soil exchange and partitioning are key processes controlling the fate and transport of POPs at regional and global scales. To date, soil fugacity has been estimated from models of the soil-air partition coefficients, with the associated unavoidable uncertainties; or by experimental procedures in the laboratory with uncertain application in field conditions. The development of an operational soil fugacity sampler is presented here; one which ensures optimal field data of the POP fugacity in soil and environmentally relevant surface (soil+grass, etc.) and therefore ensuring accurate soil-air partition coefficients and surface-air fugacity gradients. The sampler flow rate is optimized, sampler reproducibility is assessed, and equilibrium between the gas and soil concentrations of polychlorinated biphenyls and polycyclic aromatic hydrocarbons is demonstrated. The development and comprehensive validation of a soil fugacity sampler opens the door for the first time to field studies that accurately determine the variables driving the soil-air partitioning and fluxes of POPs.

Experimental results on effects of capping on fluxes of persistent organic pollutants (POPs) from historically contaminated sediments

One option proposed for the remediation of Oslo harbour, Norway, has been dredging of up to 700 000 m 3 of contaminated sediments and deposition at 60 m depth in a nearby intermittently anoxic fjord basin. Contaminant retention in the deposit area will be favoured by metal sulphide precipitation and the current absence of sediment dwelling organisms. In addition capping will be performed to protect against future fjord recovery and recolonisation with benthic animals. In order to assess the risk of contaminant leakage from the deposit area a long-term mesocosm experiment was performed to simulate the three expected successive phases: (1) anoxic basin water, (2) oxic water and (3) oxic water and presence of bioturbators. Fluxes of dissolved, bioavailable contaminants (PAHs, PCBs and DDTs) were measured by uptake in passive membrane samplers (SPMDs) located in the source seawater and downstream 0.25 m 2 boxes with capped and non-capped harbour sediments. The experiment showed that pyrene and fluoranthene was released from no-cap treatments at high rates (2545 and 830 pmol m − 2 day − 1 , respectively) during the initial, anoxic phase. The majority of components showed, however, maximum fluxes during the final, bioturbation phase: 243 pmol m − 2 day − 1 sumKPAH (six of the most cancerogenous PAHs), 19.6 pmol m − 2 day − 1 of sumPCB 7 and 13.6 pmol m − 2 day − 1 DDT. Cap layers reduced fluxes and bioaccumulation of PAH in the gastropode Hinia reticulata by 89–100%. Fluxes and bioaccumulation of PCBs was not reduced to the same extent suggesting that external sources may be relatively more important for PCB than for PAH levels in this organism. A minor release of PAH-components from one of the cap treatments indicated slight contamination from fossil fuel or explosives applied during production of the machined sand used as cap material for this treatment. Differences due to cap thickness variations between 10 and 50 cm were not found throughout the experimental period of 34 months.

Atmospheric Dry Deposition of Persistent Organic Pollutants to the Atlantic and Inferences for the Global Oceans

Atmospheric deposition to the oceans is a key process affecting the global dynamics and sinks of persistent organic pollutants (POPs). A new methodology that combines aerosol remote sensing measurements with measured POP aerosol-phase concentrations is presented to derive dry particulate depositional fluxes of POPs to the oceans. These fluxes are compared with those due to diffusive air-water exchange. For all polychlorinated biphenyl (PCB) congeners and lower chlorinated dibenzo-p-dioxins and furans (PCDD/Fs), air-water exchange dominates the dry deposition mechanism. However, this tendency reverses in some areas, such as in marine aerosol influenced areas and dust outflow regions, consistent with the important variability encountered for the depositional fluxes. Seasonal variability is mainly found in mid-high latitudes, due to the important influence of wind speed enhancing dry deposition fluxes and temperature as a driver of the gas-particle partitioning of POPs. The average dry aerosol deposition flux of sigmaPCBs and sigmaPCDD/Fs to the Atlantic Ocean is calculated to be in the order of 66 ng m(-2) yr(-1) and 9 ng m(-2)yr(-1) respectively. The total dry aerosol deposition of sigmaPCBs and sigmaPCDD/Fs to the Atlantic Ocean is estimated to be 2200 kg yr(-1) and 500 kg yr(-1), respectively, while the net air-water exchange is higher, 22000 kg sigmaPCBs yr(-1) for PCBs and 1300 kg sigmaPCDD/Fs yr(-1). Furthermore, it is suggested that marine aerosol plays an important role in scavenging atmospheric contaminants.

Atmospheric fluxes of persistent semivolatile organic pollutants to a forest ecological system at the Swedish west coast and accumulation in spruce needles

Measurements of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) have been carried out in a forested area at Lake Gårdsjön. The overall aim of this study was to identify the importance of atmospheric fluxes for the occurrence of persistent semivolatile organic compounds in a forest at the Swedish west coast and to measure the major pathways of circulation and accumulation of these contaminants within a terrestrial ecosystem. The sampling was undertaken in campaigns chosen to represent different seasons. The measurements carried out in 1991–94 were concentrated on the uptake of persistent organic pollutants (POPs) in spruce needles in relation to concentrations in air and amounts in deposition, while the measurements undertaken in 1995 also included sampling of throughfall, litterfall and run-off. The concentrations of PCBs and PAHs in the different compartments have been used to identify important reservoirs and to estimate the annual fluxes of these compounds. The results of measurements showed that atmospheric fluxes are important for the occurrence of PCBs and PAHs in forest at the Swedish west coast. A seasonal variation was found in the atmospheric concentrations, and the ambient temperature was important for PCBs in air. The amounts of PAHs and PCBs deposited to the Gårdsjö area (open field) were similar to those obtained during measurements at coastal- and sea-based sites at the Swedish west coast. Soot episodes at the Swedish west coast affected the deposition fluxes of POPs in the forest. There seemed to be both an accumulation and release of POPs in different compartments in this forest ecosystem. A greater deposition of POPs was found in the forest soil via throughfall compared with the open field deposition. An estimate of the fluxes of PAHs and PCBs in the catchment area in a forest showed that the soil is the main reservoir for POPs in this area.