Spatial Distribution of Atmospheric PCBs in Zurich, Switzerland: Do Joint Sealants Still Matter?

A Decade of Global Atmospheric Monitoring Delivers Mixed Report Card on the Stockholm Convention

Time trends in atmospheric concentrations serve to evaluate how effective the Stockholm Convention is in reducing or eliminating environmental releases of persistent organic pollutants (POPs). Twelve years (2005-2016) of continuous monitoring with a global network of 20 sampling sites reveals that concentrations of the pesticide endosulfan began to drop coincident with its listing as POP in 2011. Concentrations of other POPs started to decrease prior to listing and during the sampling period declined very slowly or not at all. Concentrations of some unintentionally produced POPs (hexachlorobenzene, hexachlorobutadiene) increased to become the most abundant and most widely dispersed POPs in the global atmosphere. Their formation processes and release locations need to be identified to facilitate the Convention's goal of curbing releases from unintentional production.

Improved Gaussian plume model for atmospheric dispersion considering buoyancy and gravitational deposition: The case of multi-form tritium

Various types of radionuclides have different atmospheric dispersion characteristics, such as buoyancy and gravitational deposition phenomenon of light gas and heavy particles, respectively. Gaussian plume model was widely used to describe atmospheric dispersion behaviors of radioactive effluents, particularly for the purpose of engineering environmental impact assessment or nuclear emergency support. Nonetheless, buoyancy and gravitational deposition were rarely reported in previous work for tritium in particular, which might cause a deviation in evaluating near-surface concentration distribution and radiation dose to the public. Based on the multi-form tritium case, we made a quantitative description for the buoyancy and gravitational deposition phenomenon and discussed the feasibility of developing an improved Gaussian plume model to predict near-surface concentration distribution. Firstly, tritium concentration distribution near to the surface was predicted by using computational fluid dynamics method (CFD) and standard Gaussian plume model to reach consistency without consideration of buoyancy and gravitational deposition effects. Secondly, effects of buoyancy and gravitational deposition were identified by species transport model for gaseous tritium and discrete phase model for droplet tritium with integrating the buoyancy force caused by density variation of gaseous tritium and gravitational force of droplet tritium with enough size. Thirdly, buoyancy and gravitational deposition correction factors were obtained to modify the standard Gaussian plume model. Lastly, predictive results by improved Gaussian plume model were compared with CFD method. It was proved the improved correction method enables higher accuracy in predicting the atmospheric concentration distribution of gaseous pollutants with density variation or particles with gravitational deposition properties.

Accumulations and temporal trends of polychlorinated biphenyls (PCBs) in olive tree components

In this study, ambient air samples, olive tree branches (1- and 2-year-old) and their leaves (particulate and dissolved phase) were collected simultaneously between January and December months at a suburban site of Bursa-Turkey. Total polychlorinated biphenyl (PCB) concentrations, sampled by employing passive air samplers, ranged from 0.03 to 0.08 ng/m³ in the atmosphere. The average annual total PCB concentrations belonging to the tree components were 1.14 ± 0.32 ng/g DM in dissolved phase in leaves, 0.71 ± 0.32 ng/g DM in particle phase on leaves, 1.06 ± 0.25 ng/g DM in 1-year-old branches, and 0.93 ± 0.23 ng/g DM in 2-year-old branches. It was determined that the correlation between PCB concentrations in olive tree components and the air was low. This result indicated that besides the tree-air exchange, other possible factors (such as soil-to-tree transitions, wind effect, etc.) affect the levels of PCB concentrations in the tree components. Total PCB concentrations decreased from summer to winter in all samples. The percentage ratio of PCB in the dissolved phase in the leaves was generally higher than other tree components in seasons. PCB homologous distributions indicated 5-CBs were dominant in the tree components and 3-CBs were dominant in the air samples. Highly chlorinated PCB congeners (8-CBs and 9-CBs) were found at low concentrations in both air and tree components samples. The samples indicated that the ratio of PCBs in tree components to the total (tree component+ambient air) PCBs slightly increased with increasing the chlorine number.

Intracity occurrence and distribution of airborne PCB congeners in Chicago

To evaluate the magnitude and extent of airborne PCBs in an urban area, we measured and investigated the temporal and spatial behavior of atmospheric concentrations of individual polychlorinated biphenyl (PCB) congeners as well as the sum of all congeners (ΣPCB) in both gas and particle phases at 27 locations across the City of Chicago in a single year (2009). In total, 141 gas-phase air samples were collected, including 22 pairs (44 samples) deployed at the same time but at two different locations, and 46 particle-phase samples. ΣPCB in the gas-phase ranged from 80 to 3000 pg/m³, with a geometric mean (GM) of 530 pg/m³, whereas particle-phase ranged from 8 to 160 pg/m³, with a GM of 28 pg/m³. We found the temporal variability to be about three times larger than the variability over space for all gas-phase congeners and ΣPCB. Around 50% of the sample PCB profiles resembled a mixture of a 1:1 vapor Aroclor mixture of 1016 + 1254, with most of the rest (30%) showing enrichment of PCB 3 (>0.1), which did not match any Aroclor profiles. PCB 11 contributed to ~5% in all samples. The fractions of PCB congeners bound to particles ranged from 0.001 to 0.97. Our analysis shows that airborne PCBs are widely distributed across Chicago and confirms that most locations have a similar PCB distribution, but differ in the concentration levels. Volatilization continues to be the main release process of PCBs into the atmosphere, including both Aroclor and non-Aroclor congeners.

Passive air sampling for semi-volatile organic chemicals

During passive air sampling, the amount of a chemical taken up in a sorbent from the air without the help of a pump is quantified and converted into an air concentration. In an equilibrium sampler, this conversion requires a thermodynamic parameter, the equilibrium sorption coefficient between gas-phase and sorbent. In a kinetic sampler, a time-averaged air concentration is obtained using a sampling rate, which is a kinetic parameter. Design requirements for kinetic and equilibrium sampling conflict with each other. The volatility of semi-volatile organic compounds (SVOCs) varies over five orders of magnitude, which implies that passive air samplers are inevitably kinetic samplers for less volatile SVOCs and equilibrium samplers for more volatile SVOCs. Therefore, most currently used passive sampler designs for SVOCs are a compromise that requires the consideration of both a thermodynamic and a kinetic parameter. Their quantitative interpretation depends on assumptions that are rarely fulfilled, and on input parameters, that are often only known with high uncertainty. Kinetic passive air sampling for SVOCs is also challenging because their typically very low atmospheric concentrations necessitate relatively high sampling rates that can only be achieved without the use of diffusive barriers. This in turn renders sampling rates dependent on wind conditions and therefore highly variable. Despite the overall high uncertainty arising from these challenges, passive air samplers for SVOCs have valuable roles to play in recording (i) spatial concentration variability at scales ranging from a few centimeters to tens of thousands of kilometers, (ii) long-term trends, (iii) air contamination in remote and inaccessible locations and (iv) indoor inhalation exposure. Going forward, thermal desorption of sorbents may lower the detection limits for some SVOCs to an extent that the use of diffusive barriers in the kinetic sampling of SVOCs becomes feasible, which is a prerequisite to decreasing the uncertainty of sampling rates. If the thermally stable sorbent additionally has a high sorptive capacity, it may be possible to design true kinetic samplers for most SVOCs. In the meantime, the passive air sampling community would benefit from being more transparent by rigorously quantifying and explicitly reporting uncertainty.

Urban geochemistry and potential human health risks in the Metropolitan Area of Buenos Aires: PAHs and PCBs in soil, street dust, and bulk deposition

Soil, street dust, and bulk deposition (dry and wet deposition) were collected in the Metropolitan Area of Buenos Aires (MABA), Argentina, to assess the polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) pollution and the potential risks to human health. Compared with other countries, the mean concentration of PAHs and PCBs in surface soils, street dust and bulk deposition of MABA were at a low or moderate level. Average PAHs and PCBs concentrations in bulk deposition (5.7 ± 5.1 and 0.41 ± 0.25 µg g^-1, respectively) were five and ten times higher than those of soil (1.08 ± 0.98 and 0.02 ± 0.01 µg g^-1) and street dust (1.2 ± 0.95 and 0.04 ± 0.03 µg g^-1), respectively. Different compositional profiles, observed in the three matrices for both groups of contaminants, could be attributed to dissimilar source contribution, partition processes between gas and particulate phases, and transformation. The most contaminated bulk deposition presented higher values for cancer and non-cancer risks relative to soil and street dust. In all matrices, non-carcinogenic risks were below the safety threshold (HI < 1). Regarding carcinogenic risks, exposure to both bulk deposition and soil indicated a moderated potential for cancerous development (Incremental lifetime cancer risk ~ 3.0 × 10^-6).

The occurrence of OCPs, PCBs, and PAHs in the soil, air, and bulk deposition of the Naples metropolitan area, southern Italy: Implications for sources and environmental processes

I am often reminded of the famous saying of Goethe: "Vedi Napoli e poi muori! - See Naples and die!". Sadly, Naples is now confronted with a number of serious, ongoing problems with a need to alleviate pressure on the worsening environment. One serious problem facing the environment is the presence of the potentially hazardous persistent organic pollutants (POPs), although few systematic studies at regional scale have been conducted. In this study, samples of soil, air, and bulk deposition were collected in Naples metropolitan area (NMA) to characterize the status of POPs, including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The results obtained showed that most of these compounds are pervasive in all the studied environmental matrices, especially in some hotspot areas, such as the Bagnoli Brownfield Site and the infamous "Triangle of the Death", where unwanted ecological risk conditions for PAHs and Endosulfan were determined, respectively. The interactional complexity between urban and the surrounding rural areas was also confirmed, as is the role that urban areas play in the migration and transformation process of POPs. High urban-rural gradients for atmospheric PAHs and PCBs were observed in the NMA, and the urban areas were identified as the emission source of these contaminants. Similarly, the OCP residues, historically originated from the nearby agricultural regions, experience long-term soil re-emission and continuously influence the connected urban environment via atmospheric transport processes.

Organophosphorus esters (OPEs) in PM2.5 in urban and e-waste recycling regions in southern China: concentrations, sources, and emissions

Organophosphate esters (OPEs) are novel ubiquitous contaminants that are attracting growing concern, but their emissions into the environment are still poorly understood. In this study, 12 OPEs were measured in fine particulate matter (PM_2.5) at 20 industrial sites in an urban region and four e-waste recycling facilities in a rural region in southern China. There was no significant difference in the concentrations of ∑OPEs between the urban region (519-62,747 pg/m³, median = 2854 pg/m³) and the rural e-waste region (775-13,823 pg/m³, 3321 pg/m³). High OPE concentrations in urban PM_2.5 were generally associated with the electrical, electronic, plastic, and chemical industries. There were no significant correlations between most OPEs in these two regions, suggesting different emission mechanisms. The average emissions of ∑OPEs estimated using a simplified dispersion model were 73.0 kg/yr from the urban industrial point sources and 33.2 kg/yr from the e-waste recycling facilities. The estimated emission inventory from industrial activities in the whole city (3228-4452 kg/yr) was approximately 30-fold higher than that from the e-waste recycling (133 kg/yr) facilities because urban region has a much larger industrial scale. To the best of our knowledge, this is the first effort to model the emissions of OPEs from industrial and e-waste recycling activities to the atmosphere.

Distribution, seasonal variation and inhalation risks of polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls and polybrominated diphenyl ethers in the atmosphere of Beijing, China

Spatial distribution, seasonal variation and potential inhalation risks of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were investigated in the atmosphere of Beijing, using passive air samplers equipped with polyurethane foam disks. Concentrations of ΣPCDD/Fs, ΣPCBs and ΣPBDEs ranged from 8.4 to 179 fg WHO₂₀₀₅-TEQ/m³, 38.6-139 and 1.5-176 pg/m³, respectively. PCDFs showed higher air concentrations than those of PCDDs, indicating the influence of industrial activities and other combustion processes. The non-Aroclor congener, PCB-11, was detected in air (12.3-99.4 pg/m³) and dominated the PCB congener profiles (61.7-71.5% to ∑PCBs). The congener patterns of PBDEs showed signatures from both penta-BDE and octa-BDE products. Levels of PCDD/Fs, PCBs and PBDEs at the industrial and residential sites were higher than those at rural site, indicating human activities in urban area as potential sources. Higher air concentrations of PCDD/Fs, PCBs and PBDEs were observed in summer, which could be associated with atmospheric deposition process, re-volatilization from soil surface and volatilization from use of technical products, respectively. Results of inhalation exposure and cancer risk showed that atmospheric PCDD/Fs, dioxin-like PCBs and PBDEs did not cause high risks to the local residents of Beijing. This study provides further aid in evaluating emission sources, influencing factors and potential inhalation risks of the persistent organic pollutants to human health in mega-cities of China.

Life cycle of PCBs and contamination of the environment and of food products from animal origin

This report gives a summary of the historic use, former management and current release of polychlorinated biphenyls (PCBs) in Germany and assesses the impact of the life cycle of PCBs on the contamination of the environment and of food products of animal origin. In Germany 60,000 t of PCBs were used in transformers, capacitors or as hydraulic oils. The use of PCB oils in these "closed applications", has been banned in Germany in 2000. Thirty to 50% of these PCBs were not appropriately managed. In West Germany, 24,000 t of PCBs were used in open applications, mainly as additive (plasticiser, flame retardant) in sealants and paints in buildings and other construction. The continued use in open applications has not been banned, and in 2013, an estimated more than 12,000 t of PCBs were still present in buildings and other constructions. These open PCB applications continuously emit PCBs into the environment with an estimated release of 7-12 t per year. This amount is in agreement with deposition measurements (estimated to 18 t) and emission estimates for Switzerland. The atmospheric PCB releases still have an relevant impact on vegetation and livestock feed. In addition, PCBs in open applications on farms are still a sources of contamination for farmed animals. Furthermore, the historic production, use, recycling and disposal of PCBs have contaminated soils along the lifecycle. This legacy of contaminated soils and contaminated feed, individually or collectively, can lead to exceedance of maximum levels in food products from animals. In beef and chicken, soil levels of 5 ng PCB-TEQ/kg and for chicken with high soil exposure even 2 ng PCB-TEQ/kg can lead to exceedance of EU limits in meat and eggs. Areas at and around industries having produced or used or managed PCBs, or facilities and areas where PCBs were disposed need to be assessed in respect to potential contamination of food-producing animals. For a large share of impacted land, management measures applicable on farm level might be sufficient to continue with food production. Open PCB applications need to be inventoried and better managed. Other persistent and toxic chemicals used as alternatives to PCBs, e.g. short chain chlorinated paraffins (SCCPs), should be assessed in the life cycle for exposure of food-producing animals and humans.

Biomonitoring of polychlorinated biphenyls in Bavaria/Germany-long-term observations and standardization

In the 1980s, it was demonstrated that semi-volatile organic compounds (SVOCs) like polychlorinated biphenyls (PCBs) accumulate in plant leaves. Plants are at the base of the food chain, and therefore a starting point for transfer of PCBs to animals and related human exposure. For two decades, the Environment Agency of the German federal state of Bavaria (LfU) has been operating long-term monitoring stations to measure the impact of organic air pollutants. Standardized ryegrass, curly kale, and spruce needles are used as bioindicators for the atmospheric entries of PCBs into vegetation. From the end of 1990s to 2009, there was a marked decline in the concentrations of indicator PCBs (i-PCBs) and a minor decline in PCB-TEQ levels. After 2009, the concentrations leveled off. In rural areas, the median concentrations of Σ6 i-PCB in ryegrass and curly kale were about 3 and 4 μg/kg dm in 2000, and have been about 0.5 and 1 μg/kg dm since 2009, respectively. Concentrations in spruce needles fell from 0.9 to 0.4 μg/kg dm. Median PCB-TEQ concentrations in the bioindicator plants ranged from 0.05 to 0.23 ng/kg dm between 2002 and 2009 and from 0.15 to 0.05 ng/kg dm after 2009. Indicator PCB and PCB-TEQ concentrations were several times higher at the urban station in Munich than at the rural areas, reflecting the emissions from in-use PCB stocks in the building sector. The likely reason of the slower decrease of PCB-TEQ compared to i-PCBs is the formation of PCB-126 by dechlorination of industrial PCBs in open applications.

Effects of room airflow on accurate determination of PUF-PAS sampling rates in the indoor environment

Accurate and precise interpretation of concentrations from polyurethane passive samplers (PUF-PAS) is important as more studies show elevated concentrations of PCBs and other semivolatile air toxics in indoor air of schools and homes. If sufficiently reliable, these samplers may be used to identify local sources and human health risks. Here we report indoor air sampling rates (Rs) for polychlorinated biphenyl congeners (PCBs) predicted for a frequently used double-dome and a half-dome PUF-PAS design. Both our experimentally calibrated (1.10 ± 0.23 m3 d-1) and modeled (1.08 ± 0.04 m3 d-1) Rs for the double-dome samplers compare well with literature reports for similar rooms. We determined that variability of wind speeds throughout the room significantly (P < 0.001) effected uptake rates. We examined this effect using computational fluid dynamics modeling and 3-D sonic anemometer measurements and found the airflow dynamics to have a significant but small impact on the precision of calculated airborne concentrations. The PUF-PAS concentration measurements were within 27% and 10% of the active sampling concentration measurements for the double-dome and half-dome designs, respectively. While the half-dome samplers produced more consistent concentration measurements, we find both designs to perform well indoors.

Occurrence of Single- and Double-Peaked Emission Profiles of Synthetic Chemicals

This work aims to elucidate the circumstances that can lead to two peaks in the temporal emission profile of synthetic chemicals. Using a simplified substance flow model, we explore how emission factors, product lifespan, and degradation half-life in waste stock influence the (i) relative importance of emissions from three lifecycle stages (industrial processes, use phase, and waste disposal), and (ii) the resulting composite emission profile. A double-peaked emission profile occurs if the lifespan of products containing the chemical is longer than its production history, and the gross emission factor from waste disposal exceeds that from the use phase. Since most chemicals fail to meet these two conditions, it is reasonable to use single-peaked emission profile as the default in environmental studies. On the basis of their emission profiles and contributions from individual lifecycle stages, we can categorize chemicals into "simple single-peakers", "composite single-peakers", and "double-peakers". Our simplified model derived emission profiles for five real chemicals that agree well with earlier, more sophisticated calculations, indicating the model's ability to capture the essential features of actual emissions. It is hoped that the model and conclusions in this work will benefit both environmental modelers and decision makers.

Calibration and evaluation of PUF-PAS sampling rates across the Global Atmospheric Passive Sampling (GAPS) network

Passive air samplers equipped with polyurethane foam (PUF-PAS) are frequently used to measure persistent organic pollutants (POPs) in ambient air. Here we present and evaluate a method to determine sampling rates (R_S), and the effective sampling volume (V_eff), for gas-phase chemical compounds captured by a PUF-PAS sampler deployed anywhere in the world. The method uses a mathematical model that requires only publicly available hourly meteorological data, physical-chemical properties of the target compound, and the deployment dates. The predicted R_S is calibrated from sampling rates determined from 5 depuration compounds (¹³C PCB-9, ¹³C PCB-15, ¹³C PCB-32, PCB-30, and d₆-γ-HCH) injected in 82 samples from 24 sites deployed by the Global Atmospheric Passive Sampling (GAPS) network around the world. The dimensionless fitting parameter, gamma, was found to be constant at 0.267 when implementing the Integrated Surface Database (ISD) weather observations and 0.315 using the Modern Era Retrospective-Analysis for Research and Applications (MERRA) weather dataset. The model provided acceptable agreement between modelled and depuration determined sampling rates, with ¹³C PCB-9, ¹³C PCB-32, and d₆-γ-HCH having mean percent bias near zero (±6%) for both weather datasets (ISD and MERRA). The model provides inexpensive and reliable PUF-PAS gas-phase R_S and V_eff when depuration compounds produce unusual or suspect results and for sites where the use of depuration compounds is impractical, such as sites experiencing low average wind speeds, very cold temperatures, or remote locations.

Rhizoremediation half-lives of PCBs: Role of congener composition, organic carbon forms, bioavailability, microbial activity, plant species and soil conditions, on the prediction of fate and persistence in soil

Polychlorinated biphenyls (PCBs) are persistent organic pollutants widely produced and used in many countries until the increasing concern about their environmental risk lead to their ban in the 1980s. Although their emissions decreased, PCBs are nowadays still present in the environment and can be reemitted from reservoir compartments such as contaminated soils. In the last two decades, there has been a growing interest in bioremediation technologies that use plants and microorganisms (i.e. rhizoremediation) to degrade organic chemicals in contaminated sites. Different studies have been conducted to investigate the potential of plant-microbe interactions in the remediation of organic chemical contaminated soils. They range from short-term and laboratory/greenhouse experiments to long-term and field trials and, when correctly set up, they could provide useful data such as PCB rhizoremediation half-lives in soil. Such type of data are important input parameters for multimedia fate models that aim to estimate the time requested to achieve regulatory thresholds in a PCB contaminated site, allowing to draw up its remediation plan. This review focuses on the main factors influencing PCB fate, persistence and bioavailability in soil including PCB mixture congener composition, soil organic carbon forms, microorganism activity, plant species and soil conditions. Furthermore, it provides an estimate of rhizoremediation half-lives of the ten PCB families starting from the results of literature rhizoremediation experiments. Finally, guidance to perform appropriate experiments to obtain comparable, accurate and useful data for fate estimation is proposed.

Import, use, and emissions of PCBs in Switzerland from 1930 to 2100

Polychlorinated biphenyls (PCBs) are persistent organic compounds that are ubiquitously found in the environment. Their use and manufacture were restricted or banned in many countries in the 1970–1980s, however, they still persist in the antroposphere, the environment and in biota worldwide today. Conventions like the Convention on Long-range Transboundary Air Pollution encourage or bind the member parties to annually submit emission inventories of regulated air pollutants. Unfortunately, several member states have not yet reported PCB emissions. The identification and quantification of stocks and emissions sources is, however, an important precondition to handle and remove the remaining reservoirs of PCBs and, thus, to be able to reduce emissions and subsequently environmental exposure. Here, we estimate past, present, and future emissions of PCBs to air in Switzerland and provide emission factors for all relevant emission categories. Switzerland hereby represents a typical developed industrial country, and most of the assumptions and parameters presented here can be used to calculate PCB emission also for other countries. PCB emissions to air are calculated using a dynamic mass flow and emissions model for Switzerland, which is run for the years 1930–2100. The results point out the importance of the use of PCBs in open applications, which have largely been previously overlooked. Additionally, we show that PCBs will persist in applications during the coming decades with ongoing emissions. Especially the use of PCBs in open applications will cause Swiss emissions to remain above 100 kg PCB per year, even after the year 2030. Our developed model is available in Excel/VBA and can be downloaded with this article.

Differentiating current and past PCB and PCDD/F sources: The role of a large contaminated soil site in an industrialized city area

Cities and contaminated areas can be primary or secondary sources of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and other chemicals, into air and soil and can influence the regional level of some of these pollutants. In a contaminated site, the evaluation of such emissions can be crucial in the choice of the remediation technology to be adopted. In the city of Brescia (Northern Italy), more than 100 ha of agricultural areas were contaminated with PCBs, PCDD/Fs and heavy metals, originating from the activities of a former PCB factory. In order to evaluate the current emissions of PCBs and PCDD/Fs from the contaminated site, in a location where other current sources are present, we compared measured and predicted air concentrations, resulting from chemical volatilization from soils as well as fingerprints of Brescia soils and of soils contaminated by specific sources. The results confirm that the contaminated area is still a current and important secondary source of PCBs to the air, and to a lesser extent of PCDFs (especially the more volatile), but not for PCDDs. PCBs in soils have fingerprints similar to highly chlorinated mixtures, indicating contamination by these mixtures and/or a long weathering process. PCB 209 is also present at important levels. PCDD fingerprints in soil cannot be related to current emission sources, while PCDFs are compatible to industrial and municipal waste incineration, although weathering and/or natural attenuation may have played a role in modifying such soil fingerprints. Finally, we combined chemical and microbiological analyses to provide an integrated approach to evaluate soil fingerprints and their variation in a wider perspective, which accounts for the mutual effects between contamination and soil microbiota, a pivotal hint for addressing in situ bioremediation activities.

Assessment of seasonal variations in persistent organic pollutants across the region of Tuscany using passive air samplers

Concentrations of persistent organic pollutants (POPs) were measured for an entire year in the region of Tuscany, Italy. Passive air samplers consisting of polyurethane foam (PUF) disks were deployed over four sampling periods of 3-5 months from April 2008 to July 2009 in urban (n = 6) and rural (n = 4) sites. The aim of the study was to characterize the spatial and seasonal variations in selected POPs. The POP concentrations (pg m^-3) in the air were dominated by dichlorodiphenyltrichloroethane and metabolites (DDTs) and polychlorinated biphenyls (∑₇PCBs). DDTs, and ∑₇PCBs showed a clear decreasing urban > rural gradient. The concentrations of DDTs and PCBs were up to 10 and 6 times higher, respectively, in urban sites than in rural sites. ∑₇PCBs showed a significant correlation with the urbanized areas located <5 km around the sampling sites. For hexachlorocyclohexanes (HCHs), α-HCH concentrations were similar at both sampling sites and were found to be quite uniform during the four sampling periods. Seasonal fluctuations were observed for DDTs, and ∑₇PCBs, with the highest concentrations observed during period 4 (summer-spring); this is most likely due to a temperature-driven re-emission from local sources. These findings were also supported by an air back trajectory analysis in the study area. This study contributes new information about POP levels in the Italian atmosphere and demonstrates the feasibility of using PUF disks to simultaneously assess seasonal concentrations at different sampling sites.

Temporal trends of chlorinated paraffins and polychlorinated biphenyls in Swiss soils

Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), are ubiquitous environmental contaminants that have been targeted by national regulations since the 1970-1980s, followed in 2004 by the worldwide regulation under the Stockholm Convention on POPs. However, concerns are growing regarding the emergence of additional POP-like substances, such as chlorinated paraffins (CPs), which have particularly large production volumes. Whereas short-chain CPs (SCCPs) have recently been restricted in Europe and are currently under evaluation for inclusion into the Stockholm Convention, medium-chain CPs (MCCPs) have received little attention. On the one hand, temporal trends of CPs in the environment have hardly been investigated. On the other hand, the effectiveness of the Stockholm Convention on environmental levels of PCBs is still a matter of debate. Here, we reconstructed temporal trends of SCCPs, MCCPs, and PCBs in archived soil samples from six sampling sites in Switzerland, covering the period 1989-2014 (respectively 1988-2013 for one site). Concentrations of SCCPs have decreased in soil since 1994, which indicates positive effects of the reduction of production of SCCPs in Europe and the increasingly stringent regulation. However, the decline in soil is slow with a halving time of 18 years. Concentrations of MCCPs have continuously increased in soil over the entire period 1989-2014, with a doubling between 2009 and 2014. The concentrations of MCCPs have surpassed those of SCCPs, showing their relevance today, partly as replacements for SCCPs. Soil concentrations of PCBs peaked in 1999, i.e. three decades later than worldwide production and use of PCBs, but earlier than the entry into force of the Stockholm Convention. PCBs follow a decline in soil with a halving time of approx. 8 years. This study shows the usefulness of sample archives for the reconstruction and interpretation of time trends of persistent environmental contaminants.

Tracking chemicals in products around the world: introduction of a dynamic substance flow analysis model and application to PCBs

Dynamically tracking flows and stocks of problematic chemicals in products (CiPs) in the global anthroposphere is essential to understanding their environmental fates and risks. The complex behavior of CiPs during production, use and waste disposal makes this a challenging task. Here we introduce and describe a dynamic substance flow model, named Chemicals in Products - Comprehensive Anthropospheric Fate Estimation (CiP-CAFE), which facilitates the quantification of time-variant flows and stocks of CiPs within and between seven interconnected world regions and the generation of global scale emission estimates. We applied CiP-CAFE to polychlorinated biphenyls (PCBs), first to evaluate its ability to reproduce previously reported global-scale atmospheric emission inventories and second to illustrate its potential applications and merits. CiP-CAFE quantifies the pathways of PCBs during production, use and waste disposal stages, thereby deducing the temporal evolution of in-use and waste stocks and identifying their long-term final sinks. Time-variant estimates of PCB emissions into air, water and soil can be attributed to different processes and be fed directly into a global fate and transport model. By capturing the international movement of PCBs as technical chemicals, and in products and waste, CiP-CAFE reveals that the extent of global dispersal caused by humans is larger than that occurring in the natural environment. Sensitivity analysis indicates that the model output is most sensitive to the PCB production volume and the lifetime of PCB-containing products, suggesting that a shortening of that lifetime is key to reducing future PCB emissions.

What determines PCB concentrations in soils in rural and urban areas? Insights from a multi-media fate model for Switzerland as a case study

Polychlorinated biphenyls (PCBs) are banned worldwide under the Stockholm Convention on Persistent Organic Pollutants. However, PCBs are still emitted in appreciable amounts from remaining primary sources in urban areas or landfills and are ubiquitous environmental contaminants, inter alia in soil and air. Concentrations of PCBs have been measured in various media by numerous studies worldwide. However, monitoring data do not always provide quantitative information about transport processes between different media, deposition fluxes to ground, or distribution of PCBs between environmental compartments. Also future trends in environmental contamination by PCBs cannot be predicted from monitoring data, but such information is highly relevant for decision-makers. Here, we present a new regionally resolved dynamic multimedia mass balance model for Switzerland to investigate the origin of PCBs in air and to investigate their long-term fate and mass balance in the environment. The model was validated with existing field data for PCBs. We find that advective inflow of PCBs from outside Switzerland into the atmospheric boundary layer is responsible for 80% of PCBs present in air in Switzerland, whereas Swiss emissions cause the remaining 20%. Furthermore, we show that the atmospheric deposition of the higher-chlorinated PCBs is dominated by particle-bound deposition, whereas the deposition of the lower-chlorinated PCBs is a combination of particle-bound and gaseous deposition. The volume fraction of particles in air is in both cases an important factor driving the deposition of PCBs to ground and, thus, contributing to the higher concentrations of PCBs generally observed in populated and polluted areas. Regional emissions influence the deposition fluxes only to a limited extent. We also find that secondary emissions from environmental reservoirs do not exceed primary emissions for all PCB congeners until at least 2036. Finally, we use our model to evaluate the effect of chemical regulation on future environmental contamination by PCBs.