The "degradative" and "biological" pumps controls on the atmospheric deposition and sequestration of hexachlorocyclohexanes and hexachlorobenzene in the North Atlantic and Arctic Oceans.

The cycling of hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCHs) has been studied in the North Atlantic and Arctic Ocean. Concentrations of HCHs and HCB were measured simultaneously in the atmosphere (gas and aerosol phases), seawater (dissolved and particulate phases), and phytoplankton. The atmospheric concentrations of HCHs decrease during transport over the Greenland Current with estimated e-folding times of 1.6 days, a trend not observed for HCB. This strong decrease in atmospheric concentrations of HCH is consistent with the estimated atmospheric depositional fluxes driven by the air-water disequilibrium. The removal of HCHs from the surface ocean by the degradative pump due to hydrolysis and microbial degradation and by the biological pump due to settling of particle-associated HCHs are estimated; the removal fluxes are within a factor of 2 of the atmospheric inputs for most sampling events, suggesting an important role of the degradative pump in the overall oceanic sink of HCHs. Conversely, the lack of degradation of HCB in surface waters and its relatively low hydrophobicity imply a lack of effective removal processes, consistent with the observed air and water concentrations close to equilibrium. This work is the first that estimates the relative importance of the biological and degradative pumps on the atmospheric deposition of the less persistent organic pollutants and points out the need for further research for quantifying the magnitude of degradative processes in the environment.

Factors affecting the occurrence and transport of atmospheric organochlorines in the China Sea and the northern Indian and South East Atlantic Oceans.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are reported in 97 air samples collected on board the RV Polarstern in November 2007 from the equator to Cape Town, South Africa and the MV Oceanic II (The Scholar Ship) in January-March 2008 from Shanghai, China to Cape Verde in the Central Atlantic Ocean. The atmospheric concentrations were higher close to the coast and lower in remote regions of the Indian and South Atlantic Ocean. Groups of samples were selected in the South China Sea, Indian Ocean and South Atlantic Ocean where the relative wind direction matched the trajectory of the ship, thus all the samples had the same input of sources upwind. In these three regions the concentrations of OCPs and PCBs declined during atmospheric transport following first order kinetics. These sets of measurements provided estimates of field derived residence times (FDRTs) for individual compounds. These values were compared with predicted atmospheric residence times (PARTs) computed using a model of long-range atmospheric transport potential of POPs. The FDRTs are 5-10 times longer for the more volatile PCB congeners and TC, CC, p,p'-DDT and p,p'-DDE than the respective PARTs, while they are similar to PARTs for the less volatile compounds. Possible causes of discrepancies between PARTs and FDRTs are discussed, and revolatilization from the ocean surface seems to be the main cause for the higher values of FDRTs of the more volatile compounds in comparison with the respective PARTs.

Biological pump control of the fate and distribution of hydrophobic organic pollutants in water and plankton.

The goal of this study was to experimentally assess the coupling between primary producer biomass dynamics and the distribution and fate of persistent organic pollutants (POPs) in a lake pelagic ecosystem. This was done by following the short-term evolution of polychlorinated biphenyl (PCB) concentrations in water and biota (phytoplankton and zooplankton) and the variability of bioconcentration (BCF), biomagnification (BMF), and bioaccumulation (BAF) factors during the development of a typical spring ecological progression in which the phytoplankton bloom is followed by a peak in the zooplankton abundance. The bulk of compounds with log K(OW) > 6.5 in the lake epilimnion was mainly associated with primary producer biomass. The phytoplankton biological pump was a major driver of POP export from the epilimnion, causing the decline of dissolved-phase concentrations. The BCF of phytoplankton for the more hydrophobic PCBs showed minima during the period of biomass climax. The concentration in the zooplankton of all selected PCBs sharply declined from March to May, with BAFs having minima in the post algal bloom phase. Biomagnification occurred during the pre algal bloom and algal bloom phases but appeared to be absent during the post algal bloom. This study highlights the occurrence of a prompt and complex response in the fate and distribution of POPs to dynamic biogeochemical control. Within the frame of the ecological succession, phytoplankton and zooplankton biomass dynamics produced bioaccumulation metrics varying over 1-2 orders of magnitude in the time frame of a few weeks and resulted in reduced trophic web exposure.

Assessment of sorbent impregnated PUF disks (SIPs) for long-term sampling of legacy POPs.

Two field studies were conducted for one year using sorbent-impregnated polyurethane foam (SIP) disks for PCB and PBDE air sampling. SIP disks were introduced by Shoeib et al. (2008) as an alternative passive air sampling medium to the polyurethane foam (PUF) disk and have the advantage of a higher holding capacity for organic chemicals. The first study on SIP disks confirmed their application for measuring volatile perfluorinated compounds (PFCs) and their ability to maintain time-integrated (linear) air sampling. In this study, the suitability of the SIP disks for long-term sampling of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and hexachlorobenzene (HCB) was assessed. SIP disks were deployed at a rural site in the UK and harvested after periods ranging from 35-350 days. Atmospheric POP concentrations were monitored with a high-volume air sampler during the deployment period. Linear uptake was observed for all monitored PCBs and PBDEs over the full exposure time. Air-sampler equilibrium was observed for HCB after 6 months. In a second field study, SIP disks were deployed for one year at 10 sites on a latitudinal transect in the UK and Norway, at which air sampling has been undertaken previously with different passive air sampling media since 1994. The estimated concentrations and spatial distributions derived from the SIP disks were largely in agreement with previously reported data.

Are reductions in industrial organic contaminants emissions in rich countries achieved partly by export of toxic wastes?

Recent studies show that PCB (polychlorinated biphenyl) air concentrations remain surprisingly high in parts of Africa and Asia. These are regions where PCBs were never extensively used, but which are implicated as recipients of obsolete products and wastes containing PCBs and other industrial organic contaminants, such as halogenated flame retardants (HFRs). We hypothesize that there may be different trends in emissions across the globe, whereby emissions of some industrial organic contaminants may be decreasing faster in former use regions (due to emission reductions combined with uncontrolled export), at the expense of regions receiving these substances as obsolete products and wastes. We conclude that the potential for detrimental effects on the environment and human health due to long-range transport by air, water, or wastes should be of equal concern when managing and regulating industrial organic contaminants. This calls for a better integration of life-cycle approaches in the management and regulation of industrial organic contaminants in order to protect environmental and human health on a global scale. Yet, little remains known about the amounts of industrial organic contaminants exported outside former use regions as different types of wastes because of the often illicit nature of these operations.

Novel system for controlled investigation of environmental partitioning of hydrophobic compounds in water.

Partitioning behavior of hydrophobic and semivolatile chemicals (such as many POPs and PAHs) in water is key in controlling their environmental distribution and fate. A new equilibrium method is presented here which allows determination of the equilibrium partition coefficient of hexachlorobenzene with suspended particle (K(SPM)≈ 337 L gOC(-1)) in a complex bulk water sample by correcting for a number of sampling artifacts and for the presence of dissolved matter. The method provides simultaneous experimental determination of the fraction of chemical truly dissolved in water (representing in this case about 54% of the bulk water concentration) and that associated to DM (21%). The Henry's law constant was also experimentally determined during the K(SPM) measurements, providing information on the occurrence of partitioning equilibrium in the system for each single observation. Results showed that the high level of quality control and accuracy provided confidence intervals for the K(SPM) estimates within 1 order of magnitude.

Evidence for major emissions of PCBs in the west African region.

In previous studies unexpectedly high air concentrations of polychlorinated biphenyls (PCBs) were observed in ship-based measurements made ∼400 km off parts of the West African coast. To investigate further (i) samples were taken on board the RV Polarstern during a cruise from Germany to South Africa in October-November 2007; (ii) samples were obtained on Cape Verde Island during the same period to monitor airflows from Africa; and (iii) passive samplers were deployed in four West African countries to try to characterize potential sources on land. Results were as follows: on Cape Verde and on the ship air masses came predominantly (∼ 95%) from the African continent; the shipboard Σ29PCB concentrations off West Africa ranged from 10 to 360 pg m(-3) and from 6 to 99 pg m(-3) in Cape Verde; the highest land-based concentrations were observed in Ivory Coast and the Gambia (up to 300 pg m(-3)) and the lowest was observed in Ghana (9 pg m(-3)). Taken together, these and previous studies indicate there are more major emission(s) of PCBs and different source types in parts of West Africa than accounted for in current global atmospheric emissions estimates. Results from the FLEXPART model and PAH measurements show that emission inventories and biomass burning cannot fully explain the high PCB concentrations. Potential sources of the high PCB levels to the African regions are discussed, namely illegal dumping of PCB containing waste with release via volatilization and uncontrolled burning, and the storage and breakup of old ships.

Has the burden and distribution of PCBs and PBDEs changed in European background soils between 1998 and 2008? Implications for sources and processes.

Background soils were collected from 70 locations on a latitudinal transect in the United Kingdom and Norway in 2008, ten years after they had first been sampled in 1998. The soils were analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCs), to see whether there had been any change in the loadings or distributions of these persistent organic pollutants (POPs). The same transect has also been used to sample air between the mid-1990s and the present, so the air and soil spatial and temporal trends provide information on air-soil transfers, source-receptor relationships, long-range atmospheric transport (LRAT), and recycling phenomena. Comparisons of the 2008 and 1998 data sets show a general decline for PBDEs in surface soil, and a smaller averaged net decline of PCBs. Changes between the years were observed for total POP concentrations in soil and also for correlations with site and sample characteristics assumed to affect those concentrations. POP concentrations were correlated to distance and strength of possible sources, a relationship that became weaker in the 2008 data. Fractionation, a commonly discussed process for the global cycling of POPs was also lost in the 2008 data. As in 1998, soil organic matter content continues to have a strong influence on the loadings of POPs in surface soils, but changes in the PCB loads were noted. These factors indicate an approach to air-surface soil equilibrium and a lessening of the influence of primary sources on POP concentrations in soil between 1998 and 2008.

Continuous monitoring of PCDD/Fs in the UK atmosphere: 1991-2008.

This study summarizes the key findings of a long-term (1991-2008) monitoring program to measure polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in urban and rural ambient air in the UK. Air concentrations are reported for 6 sites-3 urban (London, Manchester, and Middlesbrough) and 3 rural/semirural (Hazelrigg, High Muffles, and Stoke Ferry). Nearly 310 samples have been analyzed, each for a 3-month period. Annually averaged urban concentrations in the early 1990s were typically a few 100s fg (TEQ) m(-3) and <50 fg m(-3) in the mid-2000s. Applying first-order kinetics to the whole urban time series gave T1/2 (atmospheric half-lives) in London and Manchester of 3.2-5.9 and 4.1-5.9 years, respectively. Estimated national annual atmospheric emissions trends broadly correlated with the trends in urban ambient concentrations, suggesting that the inventory has captured the broad mixture of sources. However, rural air concentrations (in the low 10s fg m(-3)) show no discernible change since 1996, while recent urban concentrations are close to those in rural areas. Other UK trend data infer the declines in the 1990s followed previous declines in the 1980s from peak levels in the 1950-1970s, all before routine monitoring began. Winter concentrations are generally a factor of 2-3 higher than summer concentrations, implicating diffuse combustion sources (e.g., domestic space heating). These observations taken together suggest that most major readily controllable primary/point sources were reduced by the early/mid-1990s in the UK and that current ambient levels in both rural and urban areas may remain at broadly similar levels in the foreseeable future, unless there are major changes in energy requirements and generation options, fuel usage, and policy drivers.

Atlantic ocean surface waters buffer declining atmospheric concentrations of persistent organic pollutants.

Decreasing environmental concentrations of some persistent organic pollutants (POPs) have been observed at local or regional scales in continental areas after the implementation of international measures to curb primary emissions. A decline in primary atmospheric emissions can result in re-emissions of pollutants from the environmental capacitors (or secondary sources) such as soils and oceans. This may be part of the reason why concentrations of some POPs such as polychlorinated biphenyls (PCBs) have not declined significantly in the open oceanic areas, although re-emission of POPs from open ocean water has barely been documented. In contrast, results from this study show that several polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) have undergone a marked decline (2-3 orders of magnitude for some homologues) over a major portion of the remote oligotrophic Atlantic Ocean. The decline appears to be faster than that observed over continental areas, implicating an important role of oceanic geochemical controls on levels and cycling of some POPs. For several lower chlorinated PCDD/Fs, we observed re-emission from surface water back to the atmosphere. An assessment of the effectiveness of the main sink processes highlights the role of degradation in surface waters as potentially key to explaining the different behavior between PCDD/Fs and PCBs and controlling their overall residence time in the ocean/atmosphere system. This study provides experimental evidence that the ocean has a buffering capacity - dependent on individual chemicals - which moderates the rate at which the system will respond to an underlying change in continental emissions.

Temporal trends and controlling factors for polychlorinated biphenyls in the UK atmosphere (1991-2008).

Long-term air monitoring data sets are needed for persistent organic pollutants (POPs), to assess the effectiveness of source abatement measures and the factors controlling ambient levels. The Toxic Organic Micro-Pollutants (TOMPS) program in the United Kingdom started in 1991, generating a data set for polychlorinated biphenyls (PCBs). The history and volumes of production, usage, and subsequent restrictions on PCBs in the UK are well-characterized relative to many countries, providing a valuable case study on the effectiveness of controls and the factors influencing ambient levels and trends of these "model POPs". PCB air concentrations (congeners PCB 28, 52, 90/101, 118, 138, 153, and 180) from six rural and urban monitoring sites are presented. Most show a statistically significant decrease in PCBs levels over time, consistent with estimates of emissions, helping to validate emissions inventories. Times for a 50% decline in concentrations (sometimes called clearance rates) averaged 4.7 ± 1.6 years for all congeners at all sites. The trends at different sites and for different congeners were not statistically different from each other. Concentration differences between sites are correlated with local population density (i.e., the degree of urbanization), which supports approaches to modeling of primary emissions on the national and regional scale. The data set indicates that ambient levels and underlying trends of PCBs continue to reflect the controlling influence of diffuse primary sources from the ongoing stock of PCBs in urban environments. Production and use restrictions came into force in the UK over 40 years ago; trends since monitoring began in the early 1990s should be seen as part of a continuing decline in ambient levels since that time.

Trends in European background air reflect reductions in primary emissions of PCBs and PBDEs.

Data are presented for polychlorinated biphenyls (PCBs) and polybrominated diphenyls ethers (PBDEs) in passive air samplers (PAS) collected along a rural/remote latitudinal transect from southern UK to northern Norway during 2004-2008. This study is part of an ongoing campaign, using semipermeable membrane devices (SPMDs) as PAS over two year intervals since 1994. Absolute sequestered amounts of selected PCB congeners have decreased in a first order fashion between 1994-2008, with the average time of 8.4+/-3.2 years for atmospheric concentrations to decline by 50%. PCBs have continued to fractionate with latitude during this period. PBDE concentrations declined by 50% between 2000 and 2008 every 2.2+/-0.4 years. Results are discussed in terms of sources, long-range atmospheric transport, global fractionation, and clearance processes. It is concluded that the spatial and temporal trends in background European air mainly reflect the strength of primary diffusive emissions of these compounds and subsequently their ongoing declines. The direct evidence for this is similar rates of decline at all the sites; similar rates of decline for all congeners; no systematic change in the fractionation pattern since 1994. The latest results indicate a reduction in the rate of decline for PCBs (and hence in primary emissions).

Degradation of sulfonamides as a microbial resistance mechanism.

Two of the main mechanisms of bacterial resistance to sulfonamides in aquatic systems, spread of antibiotic resistance genes (ARG) among the microbial community and in-situ bacterial sulfonamide degradation, were studied in mesocosms experiments using water and cobble biofilms from upstream (pristine waters) and downstream (polluted waters) from the Llobregat river, NE Iberian Peninsula. Mesocosms were prepared at two different concentrations (5000 ng/L and 1000 ng/L) of sulfonamides antibiotics (sulfamethazine and sulfamethoxazole). Concentrations of ARG, nutrients, sulfonamides and their degradation products were measured during the time course of the experiments. Sulfonamides were efficiently degraded by the biofilms during the first four weeks of the experiment. The abundance of ARG in biofilms sharply decreased after addition of high concentrations of sulfonamides, but this was not observed in the mesocosms treated with low concentrations of sulfonamides. Sulfonamide degradation was faster in polluted waters and at high concentrations of sulfonamide (and lower ARG abundances), suggesting that both degradation and ARG are two complementary resistance strategies employed by the microbial community. This study shows that microbial degradation of antibiotics is an efficient resistance mechanism coupled with the presence of ARG, and suggests that in situ degradation prevails at high concentrations of antibiotics whereas physiological adaptation by ARG spread would be more important under relatively lower concentrations of antibiotics.

Passive air sampling for persistent organic pollutants: introductory remarks to the special issue.

There have been a number of developments in the need, design and use of passive air samplers (PAS) for persistent organic pollutants (POPs). This article is the first in a Special Issue of the journal to review these developments and some of the data arising from them. We explain the need and benefit of developing PAS for POPs, the different approaches that can be used, and highlight future developments and needs.

The principles of effective post-spill environmental monitoring in marine environments and their application to preparedness assessment.

Understanding the fate and effects of marine spills is essential if the scientific and response communities are to develop best practices. The effective deployment of environmental monitoring activity can be complex and requires planning and coordination but the levels of preparedness to deliver the necessary expertise, coordination and funding are often low. This paper identifies and describes the importance of 8 principles of effective post-spill monitoring programmes. These principles are then used in the assessment of monitoring preparedness through the generation of a monitoring preparedness assessment score (MPAS). This approach can be used by local, regional or national authorities to establish the level of preparedness for environmental monitoring and prioritise areas for improvement. It also has value to responders, policy makers, environmental scientists and planners as a tool to assess preparedness and capability for specific scenarios. The approach is demonstrated through the assessment of previous incidents and potential future scenarios.

Polychlorinated biphenyls (PCBs) in Africa: a review of environmental levels.

Several studies have shown an increase in PCB sources in Africa due to leakage and wrongly disposed transformers, continuing import of e-waste from countries of the North, shipwreck, and biomass burning. Techniques used in the recycling of waste such as melting and open burning to recover precious metals make PCBs contained in waste and other semivolatile organic substances prone to volatilization, which has resulted in an increase of PCB levels in air, blood, breast milk, and fish in several regions of Africa. Consequences for workers performing these activities without adequate measures of protection could result in adverse human health effects. Recent biodegradation studies in Africa have revealed the existence of exotic bacterial strains exhibiting unique and unusual PCB metabolic capability in terms of array of congeners that can serve as carbon source and diversity of congeners attacked, marking considerable progress in the development of effective bioremediation strategies for PCB-contaminated matrices such as sediments and soils in tropical regions. Action must be taken to find and deal with the major African sources of these pollutants. The precise sources of the PCB plume should be pinned down and used to complete the pollutant inventories of African countries. These nations must then be helped to safely dispose of the potentially dangerous chemicals.

Atmospheric polybrominated diphenyl ethers (PBDEs) in the United Kingdom.

The occurrence of PBDEs has been studied in the atmosphere of four sites in the United Kingdom over a period of ten years. The concentrations have exhibited a sharp decrease after 2001-2003. This is evident in the urban sites of Manchester and London and at the semi-rural site of Hazelrigg. The average ΣPBDE half-lives for these three sites were 3.4, 2.0 and 3.5 years respectively. ΣPBDEs concentrations in the UK (in 2010 ΣPBDEs < 10 pg m(-3)) are among the lowest reported in literature. Comparison of concentrations to estimated emissions and employment of PBDE profiles suggest that PBDEs in the UK atmosphere originate from primary emissions from products that contain mainly the penta-BDE technical mixture. The detection of BDE-183 in the majority of samples hints that octa-bromodiphenylether has also been used extensively in the UK, however to a smaller extent than the penta- product.

Organochlorine pesticides and PAHs in the surface water and atmosphere of the North Atlantic and Arctic Ocean.

Surface seawater and boundary layer atmospheric samples were collected on the FS Polarstern during cruise ARKXX in the North Atlantic and Arctic Ocean in 2004. Samples were analyzed for persistent organic pollutants (POPs), with a focus on organochlorine pesticides, including hexachlorocyclohexanes (HCHs), chlordanes, DDTs, hexachlorobenzene (HCB), and polycyclic aromatic hydrocarbons. In addition, the enantiomer fractions (EFs) of pesticides, notably alpha-HCH and cis-chlordane (CC), were determined. Concentrations of dissolved HCB increased from near Europe (approximately 1-2 pg/L) toward the high Arctic (4-10 pg/L). For dissolved HCB, strongest correlations were obtained with the average air or water temperature during sampling, not latitude. In the western Arctic Ocean, surface waters with elevated concentrations of HCB (5-10 pg/ L) were flowing out of the Arctic Ocean as part of the East Greenland current In contrast to dissolved compounds, atmospheric POPs did not display trends with temperature. Air-water exchange gradients suggested net deposition for all compounds, though HCB was closest to air-water equilibrium. EFs for alpha-HCH in seawater ranged from 0.43 to 0.50, except for two samples from 75 degrees N in the East Greenland Sea, with EFs of 0.31 and 0.37. Lowest EF (0.47) for CC were also at 75 degrees N, other samples had EFs from 0.49 to 0.52. It is suggested that samples from around 75 degrees N in the Greenland Gyre represented a combination of surface and older/deeper Arctic water.

Polychlorinated biphenyls (PCBs) in air and seawater of the Atlantic Ocean: sources, trends and processes.

Air and seawater samples were collected on board the RV Polarstern during a cruise from Bremerhaven, Germany to Cape Town, South Africa from October-November 2005. Broad latitudinal trends were observed with the lowest sigma27PCB air concentration (approximately 10 pg m(-3)) in the South Atlantic and the highest (approximately 1000 pg m(-3)) off the west coast of Africa. Sigma(ICES)PCBs ranged from 3.7 to 220 pg m(-3) in air samples and from 0.071 to 1.7 pg L(-1) in the dissolved phase seawater samples. Comparison with other data from cruises in the Atlantic Ocean since 1990 indicate little change in air concentrations over the remote open ocean. The relationship of gas-phase partial pressure with temperature was examined using the Clausius-Clapeyron equation; significant temperature dependencies were found for all PCBs over the South Atlantic, indicative of close air-water coupling. There was no temperature dependence for atmospheric PCBs overthe North Atlantic, where concentrations were controlled by advection of contaminated air masses. Due to large uncertainties in the Henry's Law Constant (HLC), fugacity fractions and air-water exchange fluxes were estimated using different HLCs reported in the literature. These suggest that conditions are close to air-water equilibrium for most of the ocean, but net deposition is dominating over volatilization in parts of the transect. Generally, the tri- and tetrachlorinated homologues dominated the total flux (> 70%). Total PCB fluxes (28, 52, 118, 138, and 153) ranged from -7 to 0.02 ng m(-2) day(-1).

PAHs in air and seawater along a North-South Atlantic transect: trends, processes and possible sources.

Polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in air and surface seawater between 49 degrees N and 25 degrees S in the open Atlantic Ocean. Elevated concentrations of PAHs (sigma10 PAHs approximately 1.4-2.5 ng m(-3) air, and 0.7-1 ng L(-1) seawater) occurred in the Biscay Bay and off the northwest coast of Africa. The unexpectedly high concentrations off NW Africa were discussed assessing the possible contribution of the emerging oil industry along the African shore, the role of biomass burning and natural sources of PAHs. In the southern Atlantic, concentrations of PAHs were close to detection limits (sigma10 PAHs approximately 0.02-0.5 ng m(-3) air, and 0.06-0.5 ng L(-1) seawater) and showed decreasing trends with increasing latitudes. Correlations of PAHs' partial pressures versus inverse temperature were not significant in contrast to results for polychlorinated biphenyls from the same transect. This could have been due to the importance of ongoing primary sources and the shorter atmospheric life-times of PAHs. Air-water fugacity ratios (fa/fw) were calculated for selected compounds. They were close to 1 for fluoranthene and pyrene in remote open ocean areas suggesting air-water partitioning near equilibrium. Ratios for anthracene and phenanthrene were < 0.3 in the remote tropical Atlantic, suggesting net volatilization.