Insights into the release of triclosan from microplastics in aquatic environment assessed with diffusive gradient in thin-films.

Organic chemicals associated with microplastics (MPs) can be released and thus pose potential risks during weathering processes. However, the thermodynamics and kinetics of their release processes still need to be better understood. Herein, the adsorption and desorption kinetics of triclosan on polystyrene (PS) and polyvinyl chloride (PVC) were investigated by using both batch experiments and diffusive gradients in thin-films (DGT) technique. The pseudo-second-order model fitted the data best, implying that both intraparticle diffusion and external liquid film diffusion influence the adsorption and desorption processes. DGT continuously accumulated triclosan from MP suspensions but slower than theoretical values, indicating some restrictions to desorption. The DGT-induced fluxes in Soils/Sediment (DIFS) model, employed to interpret DGT data, gave distribution coefficients for labile species (Kdl) of 5000 mL g-1 (PS) and 1000 mL g-1 (PVC) and the corresponding response times (Tc) were 10 s and 1000 s, respectively. Higher Kdl but smaller Tc for PS than PVC showed that more triclosan adsorbed on PS could be rapidly released, while there were some kinetic limitations for triclosan on PVC. A novel finding was that pH and ionic strength individually and interactively affected the supply of triclosan to DGT. This is the first study to quantify interactions of organics with MPs by using DGT, aiding our understanding of MPs' adsorption/desorption behavior in the aquatic environment.

In situ measurement of an emerging persistent, mobile and toxic (PMT) substance - Melamine and related triazines in waters by diffusive gradient in thin-films.

Melamine has received increasing public attention as a persistent, mobile and toxic (PMT) substance. To better assess environmental exposure and risks of melamine and related triazines (cyromazine, ammeline, and atrazine), a new passive sampling method based on the diffusive gradients in thin films (DGT) technique has been developed and validated in this study. The studied triazines were adsorbed quickly and strongly by the selected mixed cation exchange (MCX) binding gels. This MCX-DGT can linearly accumulate these chemicals over at least 5 days, with neither significant individual influence from pH (6-8), ionic strength (0.01-0.5 M) or dissolved organic matter (0-10 M), or interaction effects. Field applications in Southern China showed that DGT performed well in both sewage treatment plant (STP) and river samples. Melamine was found to be the dominant triazine with the concentrations at µg·L-1 in the STP and receiving river. Surprisingly, much higher concentration of melanine was found in the STP effluent than influent, and appeared to be some of the highest concentrations reported in STPs worldwide to date. Comparable melamine and atrazine concentraions in the STP effluent and receiving river suggested other sources to the river. The MCX-DGT sampler developed here was demonstrated to be reliable and robust for measuring the triazines in waters, and is promising as an in situ tool in understanding the occurrence, sources, and fate of the emerging PMT substances in aquatic environment.

Spatial and seasonal variations of antibiotics in river waters in the Haihe River Catchment in China and ecotoxicological risk assessment.

Concentrations of widely used antibiotics were predicted to be the highest in the Haihe River Catchment across China previously, potentially resulting in high ecotoxicological risks in this region. As a result of growing usage and regulation of antibiotic use in animals, the pattern of use may have altered temporally for different antibiotics. It is important to monitor the occurrence of antibiotics within different categories for understanding their mass loading to the catchment and the potential ecotoxicological risks involved. This study investigated the seasonal occurrence and spatial variation of 15 antibiotics in the Haihe River Catchment during 2016-2017. The investigated compounds included veterinary antibiotics, human-use antibiotics, and those intended for both human and animal use. Measurements reported from previous studies were compared with the results of this study and indicated that the use of veterinary antibiotics is probably increasing around the catchment. The ∑antibiotics concentration (i.e. the summed concentration of the 15 target antibiotics) ranged from 414 to 1951 ng/L, with an average of 821 ng/L. Discharges from wastewater treatment plants were the main sources of these compounds. The mass loading of antibiotics to the river waters was higher during wet seasons than during dry seasons. The mass fluxes of the antibiotics continuously increased towards the lower reaches of the rivers. The total annual input of the antibiotics from the Haihe River and Yongdingxin River into the Bohai Bay was 5008 kg/yr. Ofloxacin, trimethoprim, leucomycin, anhydro erythromycin and florfenicol were the predominant antibiotics, whilst amoxicillin, anhydro erythromycin, ofloxacin, norfloxacin and enrofloxacin may pose high ecotoxicological risks to the investigated aquatic ecosystem. Several antibiotics selected in this study were reported for the first time in this catchment. This study provides important information for chemical management and indicates that further monitoring is needed on the more harmful and veterinary antibiotics in the catchment.

Persistent Organic Pollutants in sediment and fish in the River Thames Catchment (UK).

Some organic pollutants including polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and hexachlorobenzene (HCB) have been banned from production and use in the UK for >30years but due to their toxicity and persistence are still of concern. However, due to their hydrophobicity they are present at very low concentrations and are difficult to measure in water, and so other matrices need to be sampled in order to best assess contamination. This study measured concentrations of ΣICES 7 PCBs (PCB congeners 28, 52, 101, 118, 138, 153 and 180) and Σ6 PBDEs (PBDE congeners 28, 47, 99, 100, 153, 154) and HCB in both bed-sediments and wild roach (a common pelagic fish) in the Thames Basin. The highest sediment concentrations were detected in an urbanised tributary of the Thames, The Cut at Bracknell (HCB: 0.03-0.40µg/kg dw; ICES 7 PCBs: 4.83-7.42µg/kg dw; 6 BDEs: 5.82-23.10µg/kg dw). When concentrations were expressed on a dry weight basis, the fish were much more contaminated than the sediments, but when sediment concentrations were normalised to organic carbon concentration they were comparable to the fish lipid normalised concentrations. Thus, despite the variability in the system, both sediments and wild fish can be considered suitable for representing the level of POPs contamination of the river system given sufficient sample numbers.

The distribution of Polychlorinated Biphenyls (PCBs) in the River Thames Catchment under the scenarios of climate change.

Measurements have shown low levels of PCBs in water but relatively high concentrations in the resident fish of the River Thames (UK). To better understand the distribution and behaviour of PCBs in the Thames river basin and their potential risks, a level III fugacity model was applied to selected PCB congeners (PCB 52, PCB 118 and PCB 153). The modelling results indicated that fish and sediments represent environmental compartments with the highest PCB concentrations; but the greatest mass of PCBs (over 70%) is likely to remain in the soil. As emissions decline, soil could then act as a significant secondary source of PCBs with the river bed-sediment functioning as a long-term reservoir of PCBs. The predicted changes in temperature and rainfall forecast in the UK Climate Projections 2009 (UKCP09) over the next 80 years had only a modest influence on PCB fate in the model. The most significant result was a tendency for climate change to enhance the evaporation of PCBs from soil to air in the Thames catchment.

A first European scale multimedia fate modelling of BDE-209 from 1970 to 2020.

The European Variant Berkeley Trent (EVn-BETR) multimedia fugacity model is used to test the validity of previously derived emission estimates and predict environmental concentrations of the main decabromodiphenyl ether congener, BDE-209. The results are presented here and compared with measured environmental data from the literature. Future multimedia concentration trends are predicted using three emission scenarios (Low, Realistic and High) in the dynamic unsteady state mode covering the period 1970-2020. The spatial and temporal distributions of emissions are evaluated. It is predicted that BDE-209 atmospheric concentrations peaked in 2004 and will decline to negligible levels by 2025. Freshwater concentrations should have peaked in 2011, one year after the emissions peak with sediment concentrations peaking in 2013. Predicted atmospheric concentrations are in good agreement with measured data for the Realistic (best estimate of emissions) and High (worst case scenario) emission scenarios. The Low emission scenario consistently underestimates measured data. The German unilateral ban on the use of DecaBDE in the textile industry is simulated in an additional scenario, the effects of which are mainly observed within Germany with only a small effect on the surrounding areas. Overall, the EVn-BTER model predicts atmospheric concentrations reasonably well, within a factor of 5 and 1.2 for the Realistic and High emission scenarios respectively, providing partial validation for the original emission estimate. Total mean MEC:PEC shows the High emission scenario predicts the best fit between air, freshwater and sediment data. An alternative spatial distribution of emissions is tested, based on higher consumption in EBFRIP member states, resulting in improved agreement between MECs and PECs in comparison with the Uniform spatial distribution based on population density. Despite good agreement between modelled and measured point data, more long-term monitoring datasets are needed to compare predicted trends in concentration to determine the rate of change of POPs within the environment.

A new multimedia contaminant fate model for China: how important are environmental parameters in influencing chemical persistence and long-range transport potential?

We present a new multimedia chemical fate model (SESAMe) which was developed to assess chemical fate and behaviour across China. We apply the model to quantify the influence of environmental parameters on chemical overall persistence (POV) and long-range transport potential (LRTP) in China, which has extreme diversity in environmental conditions. Sobol sensitivity analysis was used to identify the relative importance of input parameters. Physicochemical properties were identified as more influential than environmental parameters on model output. Interactive effects of environmental parameters on POV and LRTP occur mainly in combination with chemical properties. Hypothetical chemicals and emission data were used to model POV and LRTP for neutral and acidic chemicals with different KOW/DOW, vapour pressure and pKa under different precipitation, wind speed, temperature and soil organic carbon contents (fOC). Generally for POV, precipitation was more influential than the other environmental parameters, whilst temperature and wind speed did not contribute significantly to POV variation; for LRTP, wind speed was more influential than the other environmental parameters, whilst the effects of other environmental parameters relied on specific chemical properties. fOC had a slight effect on POV and LRTP, and higher fOC always increased POV and decreased LRTP. Example case studies were performed on real test chemicals using SESAMe to explore the spatial variability of model output and how environmental properties affect POV and LRTP. Dibenzofuran released to multiple media had higher POV in northwest of Xinjiang, part of Gansu, northeast of Inner Mongolia, Heilongjiang and Jilin. Benzo[a]pyrene released to the air had higher LRTP in south Xinjiang and west Inner Mongolia, whilst acenaphthene had higher LRTP in Tibet and west Inner Mongolia. TCS released into water had higher LRTP in Yellow River and Yangtze River catchments. The initial case studies demonstrated that SESAMe performed well on comparing POV and LRTP of chemicals in different regions across China in order to potentially identify the most sensitive regions. This model should not only be used to estimate POV and LRTP for screening and risk assessments of chemicals, but could potentially be used to help design chemical monitoring programmes across China in the future.

Challenges in assessing release, exposure and fate of silver nanoparticles within the UK environment.

There are significant challenges in assessing the fate and exposure of nanoparticles (NPs) in the environment owing to the lack of information on their use, potential pathways and sinks in the environment. In order to better understand the environmental exposure of silver nanoparticles (AgNPs), we reviewed the uses and potential exposure sources of both Ag and AgNPs. The approach taken was to identify the range of products that utilise its properties, identify potential environmental release pathways and subsequent fate once released into the environment. We then compared measured environmental concentrations with modelled concentrations from our work and others. We estimate that within the United Kingdom (UK) a total quantity of 8.8 tonnes per year of AgNPs is released from products containing AgNPs and enters UK waste water systems. Sewage sludge was identified as an important receiving compartment. Agricultural land with sludge applied was estimated to have a yearly increase in AgNP concentration of 36 µg per kg per year. Available ecotoxicity data for soil and the predicted environmental concentrations are used to perform a risk characterisation. This work highlights the on-going challenges faced when undertaking a risk assessment of AgNPs in the environment.

Estimation of PFOS emission from domestic sources in the eastern coastal region of China.

Perfluorooctane sulfonate (PFOS) and related chemicals (collectively "PFOS equivalents") have been released to the environment through widespread consumer use and disposal of PFOS-containing products like carpet, leather, textiles, paper, food containers, household cleansers, etc. Accordingly, in addition to PFOS-related industries, domestic activities may also considerably contribute to the PFOS emissions in the eastern coastal region of China, which has been characterized by high industrial input. In the present study, domestic emissions of PFOS equivalents derived from municipal wastewater treatment plants were estimated at the county level, using a regression model of domestic emission density with population density and per capita disposable income as independent variables. The total emission load of PFOS equivalents from domestic sources in the eastern coastal region of China was 381kg in 2010, and large cities were prominent as the emission centers. The domestic emission density averaged 0.37g/km(2)·a for the entire study area. Generally, the Beijing-Tianjin area, Pearl River Delta and Yangtze River Delta, as the most populous and economically developed areas in China, showed significantly higher emission density. Geographical variations within individual provinces were noteworthy. The average per capita discharge load of PFOS equivalents arising from domestic activities was 1.91µg/day per capita in the eastern coastal region of China, which is consistent with previous estimates in Korea, but lower than those calculated for developed countries. In comparison, the spatial distributions of provincial PFOS emissions from domestic and industrial sources were similar to each other; however, the latter was much larger for all the provinces.

Estimating European historical production, consumption and atmospheric emissions of decabromodiphenyl ether.

A European scale production, consumption and environmental emissions inventory is produced for decabromodiphenyl ether (DecaBDE) for the period 1970-2020. A dynamic substance flow analysis model of DecaBDE is developed and emission of the main congener, BDE-209, to environmental compartments is estimated. From 1970 to 2010, it is estimated that a total of 185,000-250,000 tonnes of DecaBDE was consumed in Europe. Consumption peaked in the late 1990s at approximately 9,000 tonnes/year and has declined by ~30% in 2010. Predicted BDE-209 atmospheric emissions peak in 2004 at 10 tonnes/year. The waste management phase of the BDE-209 life cycle is responsible for the majority of atmospheric emissions via volatilisation and particle bound emissions from landfills, whilst leakage from Sewerage systems is the major source of emissions to the hydrosphere. Use of sewage sludge from wastewater treatment works as an agricultural fertiliser is the most important pathway of BDE-209 to soil. Although DecaBDE consumption has declined in recent years, the stock in use for 2010 remains considerable (60,000 tonnes) and is likely to act as a source of atmospheric emissions for several decades. Uncertainties exist in these estimations and more field or experimental data is needed to clarify the significance of certain emission pathways, in particular, emissions from landfill sites.

Using passive air samplers to assess local sources versus long range atmospheric transport of POPs.

Passive air samplers (PAS) are cost-efficient tools suitable for spatial mapping of atmospheric concentrations of persistent organic pollutants (POPs). The objective of this study was to use PAS to (i) determine atmospheric concentrations of selected POPs in Norwegian coastal zones with consumption advisories on seafood (N = 22), and (ii) evaluate a simple nested monitoring approach to assess the relative influence of local vs. long-range atmospheric transport (LRAT) at coastal sites. The latter was facilitated by comparison with data from a coordinated European-wide campaign in which an identical sampling and analytical approach was followed. Air concentrations were calculated based on the loss of performance reference compounds (PRCs), and results are presented for selected polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), dichlorodiphenyltrichloroethanes (DDTs) and chlordanes. Air concentrations of PCBs were generally highest at sites within larger cities and up to about an order of magnitude higher than anticipated on the basis of LRAT alone. The distribution of PAHs and HCB occasionally showed elevated concentrations at coastal sites with ongoing or former industrial activity, while an urban site was significantly influenced by banned insecticides (technical DDT and lindane). Coastal sites were also elevated in α-HCH beyond the anticipated LRAT contribution, which we attribute to volatilization from the sea. We conclude that a simple nested PAS monitoring approach provides useful information for screening efforts aiming to assess both atmospheric burdens as well as the relative significance of local sources in controlling these burdens at sites in contaminated areas.

Can car air filters be useful as a sampling medium for air pollution monitoring purposes?

Urban air quality and real human exposure to chemical environmental stressors is an issue of high scientific and political interest. In an effort to find innovative and inexpensive means for air quality monitoring, the ability of car engine air filters (CAFs) to act as efficient samplers collecting street level air, to which people are exposed to, was tested. In particular, in the case of taxis, air filters are replaced after regular distances, the itineraries are almost exclusively urban, cruising mode is similar and, thus, knowledge of the air flow can provide with an integrated city air sample. The present pilot study focused on polycyclic aromatic hydrocarbons (PAHs), the most important category of organic pollutants associated with traffic emissions. Concentrations of ΣPAHs in CAFs ranged between 650 and 2900 µg CAF(-1), with benzo[b]fluoranthene, benzo[k]fluoranthene and indeno[123-cd]pyrene being the most abundant PAHs. Benzo[a]pyrene (BaP) ranged between 110 and 250 µg CAF(-1), accounting regularly for 5-15% of the total carcinogenic PAHs. The CAF PAH loads were used to derive road-level atmospheric PAH concentrations from a standard formula relating to the CAF air flow. Important parameters/assumptions for these estimates are the cruising speed and the exposure duration of each CAF. Based on information obtained from the garage experts, an average 'sampled air volume' of 48,750 m(3) per CAF was estimated, with uncertainty in this calculation estimated to be about a factor of 4 between the two extreme scenarios. Based on this air volume, ΣPAHs ranged between 13 and 56 ng m(-3) and BaP between 2.1 and 5.0 ng m(-3), suggesting that in-traffic BaP concentrations can be many times higher than the limit values set by the UK (0.25 ng m(-3)) and the European Union (1.0 ng m(-3)), or from active sampling stations normally cited on building roof tops or far from city centres. Notwithstanding the limitations of this approach, the very low cost, the continuous availability of very high amounts of "sample", and the "retroactivity" render it very useful and complementary to existing passive sampling techniques. This approach yields estimated air concentrations that reflect the pollutant concentrations to which taxi drivers, pedestrians, cyclists and road-related professionals are exposed.

The contribution of waste water treatment plants to PBDEs in ambient air.

Air samples were collected at different sites in and around two wastewater treatment plants (WWTPs) located in central Italy to determine the concentrations, compositional profiles and contribution to ambient levels of eight polybrominated diphenyl ethers (PBDEs). The investigated WWTPs were selected as they treat industrial wastewater produced by local textile industries along with municipal wastewater. PBDE concentrations within the WWTPs were higher than those measured at reference sites located 4 and 5 km away with BDE-209 dominating the BDE congener composition in all air samples in 2008. Ambient PBDE concentrations measured in and around the WWTPs and estimates of emissions from aeration tanks suggest that WWTPs are sources of PBDEs to ambient air. Principal component analysis and Pearson correlations confirmed this result. The effect of distance from the plant and wind direction on atmospheric concentrations was also investigated. Although the primary fate of PBDEs in WWTPs will be partitioning to sewage sludge, this study suggests that plants can provide a measurable source of these compounds to local ambient air.

PBDEs in Italian sewage sludge and environmental risk of using sewage sludge for land application.

Polybrominated diphenyl ethers (PBDEs) were determined in sewage sludge samples collected from eight Italian wastewater treatment plants (WWTPs) between June 2009 and March 2010. Total PBDE concentrations ranged from 158.3 to 9427 ng g(-1) dw, while deca-BDE (BDE-209) (concentrations ranging from 130.6 to 9411 ng g(-1) dw) dominated the congener profile in all the samples, contributing between 77% and 99.8% of total PBDE. The suitability of using a magnetic particle enzyme-linked immunoassay (ELISA) to analyse PBDEs in sewage sludge was also tested. The ELISA results, expressed as BDE-47 equivalents, were well correlated with those obtained by GC-NCI-MS, with correlation coefficients (r(2)) of 0.899 and 0.959, depending on the extraction procedure adopted. The risk assessment of PBDEs in sewage sludge addressed to land application was calculated. PEC(soil) values compared to the relative PNEC(soil) for penta and deca-BDE suggests that there is a low risk to the soil environment.

The use of commercial and industrial waste in energy recovery systems - A UK preliminary study.

With 2020 energy targets set out by the EU fast approaching, the UK is trying to source a higher proportion of its energy from renewable resources. Coupled with this, a growing population and increasing trends in consumer demand have resulted in national waste loads increasing. A possible solution to both issues is energy-from-waste (EfW) technologies. Many studies have focused on municipal solid waste (MSW) as a potential feedstock, but appear to overlook the potential benefits of commercial and industrial waste (C&IW). In this study, samples of C&IW were collected from three North West waste management companies and Lancaster University campus. The samples were tested for their gross and net calorific value, moisture content, ash content, volatile matter, and also elemental composition to determine their suitability in EfW systems. Intra-sample analysis showed there to be little variation between samples with the exception two samples, from waste management site 3, which showed extensive variation with regards to net calorific value, ash content, and elemental analysis. Comparisons with known fuel types revealed similarities between the sampled C&IW, MSW, and refuse derived fuel (RDF) thereby justifying its potential for use in EfW systems. Mean net calorific value (NCV) was calculated as 9.47MJ/kg and concentrations of sulphur, nitrogen, and chlorine were found to be below 2%. Potential electrical output was calculated using the NCV of the sampled C&IW coupled with four differing energy generation technologies. Using a conventional incinerator with steam cycle, total electrical output was calculated as 24.9GWh, based on a plant operating at 100,000tpa. This value rose to 27.0GWh when using an integrated gasification combined cycle. A final aspect of this study was to deduce the potential total national electrical output if all suitable C&IW were to be used in EfW systems. Using incineration coupled with a steam turbine, this was determined to be 6TWh, 1.9% of the national demand thereby contributing 6.5% towards the UK's 2020 renewable electricity target.

Coupling passive air sampling with emission estimates and chemical fate modeling for persistent organic pollutants (POPs): a feasibility study for Northern Europe.

Passive air samplers (polyurethane foam disks) were deployed at 23 background locations along a broadly west-east transect in 8 northern European countries and analyzed for PCBs, PBDEs, PAHs, and a range of organochlorine pesticides (HCB, DDTs, and DDEs). PCBs and PAHs were highest at the center of the transect (Denmark) and lowest in northern Norway. HCB was relatively uniformly distributed, reflecting its persistence and high degree of mixing in air. Higher DDE and DDT levels occurred in Eastern Europe and at several sites in Central Europe. PBDE levels were generally similar at all sites, but lower for some locations in Eastern Europe and Ireland. Emissions information for PCBs, HCB, and PBDEs was used as input for a multi-media chemical fate model, to generate predicted air concentrations and compare with these measured values. Different scenarios were highlighted by this exercise: (i) country and compound combinations where the national inventory gave predicted air concentrations in close agreement with those measured (e.g., PCBs in the UK); (ii) country and compound combinations where predicted concentrations were well below those measured, but where advection of emissions from elsewhere is likely to be important (e.g., PCBs in Norway); (iii) consistent underestimation of compound concentrations by the emissions modeling (i.e., HCB); and (iv) general overestimation of ambient concentrations (i.e., PBDEs). Air mass trajectory analysis showed the likely role of long-range atmospheric transport (LRAT) on national levels. In general, advection from the south and west of Europe appeared to contribute to ambient POPs levels for countries in the center and northeast of the transect. Guidelines are presented as to how countries that want to assess their POPs source inventories can do so with this relatively cheap initial screening approach.

Towards a global historical emission inventory for selected PCB congeners--a mass balance approach 3. An update.

Previously published estimates of the global production, consumption and atmospheric emissions of 22 individual PCB congeners [Breivik K, Sweetman A, Pacyna JM, Jones KC. Towards a global historical emission inventory for selected PCB congeners - a mass balance approach. 1. Global production and consumption. Sci Total Environ 2002a; 290: 181-198.; Breivik K, Sweetman A, Pacyna JM, Jones KC. Towards a global historical emission inventory for selected PCB congeners--a mass balance approach. 2. Emissions. Sci Total Environ 2002b; 290: 181-198.] have provided useful information for later studies attempting to interpret contaminant levels in remote areas as well as in the global environment. As a result of the need for more contemporary emission data (following the year 2000), an update of this emission database is presented. This exercise takes into account new information on PCB production in Poland, as well as new data on the chemical composition of various technical mixtures for which less information had been available. The methodology to estimate temporal trends of PCB emissions associated with various types of PCB usage is improved. Projected emissions up to year 2100 are presented to facilitate predictions of future environmental exposure. The national emission data for each of the 114 countries considered is spatially resolved on a 1 degrees x1 degrees grid for each congener and year, using population density as a surrogate.

Passive sampler-derived air concentrations for polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons in Kuwait.

The present study presents, to our knowledge, the first ambient air data for a range of polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) in Kuwait. This was achieved by concurrently deploying polyurethane foam-disk passive samplers at 14 sites over a six-week period. Calculated mean sigma5PBDE concentrations (sum of brominated diphenyl ethers [BDEs] 47, 99, 100, 153, and 154) ranged from 2.5 to 32 pg/m3 of air, with BDE 47 contributing between 39 and 65% of the sigmaPBDEs detected. Differences in relative concentrations were observed between sites, with higher concentrations measured close to suspected sources. Calculated sigmaPAH concentrations ranged from 5 to 13 ng/m3 (mean, 8.3 ng/m3). The compound distribution was dominated by three- and four-ring compounds, which constituted approximately 90% of the sigmaPAHs, with phenanthrene contributing approximately 35%. However, the proportion of five- and six-ring PAHs increased around the "oil lakes," which were formed by the torching of oil wells during the 1991 Gulf War. The oil lakes are a reservoir of PAHs that will continue feeding the atmosphere as long as they remain untreated.

Spatial and temporal variability in air concentrations of short-chain (C10-C13) and medium-chain (C14-C17) chlorinated n-alkanes measured in the U.K. atmosphere.

Two studies were carried out on short-chain (C10-C13) and medium-chain (C14-C17) polychlorinated n-alkanes (sPCAs and mPCAs) in U.K. air samples. The first study entailed taking 20 24-h air samples with a pair of Hi-Vol air samplers at the Hazelrigg field station, near Lancaster University. These samples were carefully selected to coincide with times when air masses were predicted to have a fairly constant back trajectory for 24 h and to give a broad spectrum of different origins. The second study was a spatial survey of PCAs in the air at 20 outdoor sites in northern England and four indoor locations in Lancaster, using polyurethane foam (PUF) disk passive air samplers. Levels of the sPCAs in the Hi-Vol samples ranged from <185 to 3430 pg m(-3) (average 1130 pg m(-3)) and were higher than those previously measured at this site in 1997. Levels of the mPCAs ranged from <811 to 14500 pg m(-3) (average 3040 pg m(-3)); that is, they were higher than sPCAs. Both sPCA and mPCA air concentrations are of the same order of magnitude as PAH at this site. Back trajectory analysis showed that the history of the air mass in the 48 h prior to sampling had an important effect on the concentrations observed, with overland samples having higher levels than oceanic, implying that the U.K. is probably responsible for most of the PCAs measured in the U.K. atmosphere. Amounts of both sPCAs and mPCAs in the passive air samples followed a rural-urban gradient. PCAs appear to be released from multiple sources around the country, as a result of the diffusive, open industrial and construction use of the technical mixtures.