Current challenges in air sampling of semivolatile organic contaminants: sampling artifacts and their influence on data comparability

Occurrence and distribution of pesticides and transformation products in ambient air in two European agricultural areas

Pesticides present a significant risk for both humans and the environment. However, quantitative data for a broad range of airborne pesticides in agricultural areas are missing. During or after the application, pesticides can reach the atmosphere and partition between the particulate and gaseous phase. As part of the EU project SPRINT, weekly ambient air samples were collected from two agricultural areas in Portugal (vineyard) and the Netherlands (potatoes, onions, and sugarbeet) between April 2021 and June 2022 using high-volume air samplers. The samples were analysed for 329 pesticides, of which 99 were detected. The most frequently detected compounds included the fungicides folpet, fenpropidin and mandipropamid, the insecticide chlorpyrifos-methyl, the herbicide terbuthylazine, and the metabolite prothioconazole-desthio, which were found with detection frequencies between 40 and 57 %. Pesticide concentrations ranged between 0.003 ng/m3 and 10 ng/m3. Remarkably, 97 % of the samples contained at least one pesticide and in 95 % of the samples, pesticide mixtures were present. The calculated particle phase fractions correlated with the octanol-air partitioning coefficient for most of the investigated compounds. Furthermore, calculated daily inhalation rates for individual pesticides and pesticide mixtures were far below the Acceptable Daily Intake (ADI) with a margin of exposure (MOE) of >1000 for the highest calculated daily inhalation rate for a child. However, as this value only includes pesticide intake from food and drinking water and considering that 91 % of the detected pesticides are associated with potential adverse human health effects. These findings highlight the broad range of airborne pesticides in agricultural areas and the need for quantitative data to include the intake of mixtures of highly hazardous pesticides by inhalation in human risk assessment.

Air-plant interaction and air-soil exchange of polycyclic aromatic hydrocarbons in a large human-influenced reservoir in southwest China

The Three Gorges Reservoir (TGR) is totally manmade, strongly influenced by anthropogenic activity, and lies on the upper reaches of Yangtze River. The periodic storage and discharge of water from the Three Gorges Dam could have altered the original air-plant/soil interactions of contaminants in TGR. Herein, paired atmospheric gas-particle, air-plant, and air-soil samples were collected to investigate the air-plant interaction and air-soil exchange of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs). The air-plant interaction based on McLachlan's framework to our datasets suggests that PAHs were absorbed via gaseous deposition that was restricted by the plant-gas dynamic equilibrium. The equilibrium indicates a dynamic balance between the gaseous phase and plant surface in PAH absorption. The main limiting factor influencing the PAH uptake was the plant species rather than the atmospheric PAH concentration. The air-soil exchange of PAHs exhibited a net volatilization flux of 16.71 ng/m2/d from the soil to the air based on annual average. There was more volatilization and less deposition in summer and more deposition and less volatilization in autumn and winter. The soil serves as a secondary source of atmospheric PAHs. As the first attempt on probing the multi-interface geochemical process of PAHs, this study highlights the influence of manual water level manipulation from the TGD and environmental factors (such as temperature, humidity, and soil properties) on the regional fate of PAHs in the TGR.

A review of sample collection and analytical methods for detecting per- and polyfluoroalkyl substances in indoor and outdoor air

Per- and polyfluoroalkyl substances (PFAS) are a unique class of chemicals synthesized to aid in industrial processes, fire-fighting products, and to benefit consumer products such as clothing, cosmetics, textiles, carpets, and coatings. The widespread use of PFAS and their strong carbon-fluorine bonds has led to their ubiquitous presence throughout the world. Airborne transport of PFAS throughout the atmosphere has also contributed to environmental pollution. Due to the potential environmental and human exposure concerns of some PFAS, research has extensively focused on water, soil, and organismal detection, but the presence of PFAS in the air has become an area of growing concern. Methods to measure polar PFAS in various matrices have been established, while the investigation of polar and nonpolar PFAS in air is still in its early development. This literature review aims to present the last two decades of research characterizing PFAS in outdoor and indoor air, focusing on active and passive air sampling and analytical methods. The PFAS classes targeted and detected in air samples include fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamides (FASAs), perfluoroalkane sulfonamido ethanols (FASEs), perfluorinated carboxylic acids (PFCAs), and perfluorinated sulfonic acids (PFSAs). Although the manufacturing of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) has been largely phased out, these two PFAS are still often detected in air samples. Additionally, recent estimates indicate that there are thousands of PFAS that are likely present in the air that are not currently monitored in air methods. Advances in air sampling methods are needed to fully characterize the atmospheric transport of PFAS.

Characterization of persistent organic contaminants in the atmosphere of Gadani's ship breaking yards and its surrounding: Implications for sustainable ship recycling practices

Gadani is internationally renowned for its extensive ship-breaking operations, positioning it as one of the globe's primary ship-breaking hubs. A comprehensive study was conducted to evaluate the presence of organic contaminants in the air within Gadani, encompassing the areas surrounding ship-breaking facilities, proximate residential settlements, and adjacent roadways. Passive air samplers were employed to collect a total of 30 air samples. The analytical results unveiled a notably elevated concentration of specific organic compounds, with a pronounced prevalence of polycyclic aromatic hydrocarbons (PAHs), short-chain chlorinated paraffins (SCCPs), and polychlorinated biphenyls (PCBs) at the ship-breaking yard. Notably, dichlorodiphenyltrichloroethanes (DDTs) and DDE were detected at substantially lower levels. In particular, sites in close proximity to ship-breaking activities exhibited elevated concentrations of PCBs (Σ7PCB 0.065429 to 7.345714 ng/sample), PAHs (Σ8PAH 2.44 to 134.23 ng/sample), and SCCPs (0.18 to 25.6 ng/sample). Conversely, DDTs and DDE demonstrated higher concentrations near residential settlements. The evaluation of Molecular Diagnostic Ratios for PAHs revealed anthracene/anthracene + phenanthrene ratios of 0.88, 0.69, and 0.5 for ship-breaking areas, roadside locations, and community surroundings, respectively. Furthermore, the benz[a]anthracene/benz-[a]anthracene + chrysene molecular ratios were measured at 0.77 (ship-breaking sites), 0.82 (roadside), and 0.83 (community), respectively. The molecular ratio of fluoranthene/fluoranthene + pyrene at ship-breaking sites was 0.23, while roadside and community ratios were 0.36 and 0.89, respectively. These findings underscore the significant contribution of ship-recycling activities to the atmospheric release of SCCPs, PCBs, and PAHs, emphasizing the global imperative for responsible ship recycling practices.

Cross-regional scale studies of organochlorine pesticides in air in China: Pollution characteristic, seasonal variation, and gas/particle partitioning

Few simultaneous studies of organochlorine pesticides (OCPs) in the atmosphere have been conducted across Southeast and Northeast China, and no data on the gas/particle (G/P) partitioning behaviors of several current-use OCPs are available. In this study, a one-year synchronous monitoring program was conducted for OCPs in Chinese atmosphere spanning 30° latitude and 60 °C temperature. A total of 111 pairs of gas and particle samples were collected from Mohe and Harbin in Northeast China and from Shenzhen in Southeast China. The detection frequency for 66.7 % of the OCPs exceeded 80 %, indicating their prevalence in the atmosphere. The concentrations of individual OCPs spanned six orders of magnitude, indicating different pollution levels. Highest levels of hexachlorobenzene were observed at all sites. Banned OCPs were found predominantly in secondary distribution patterns, whereas current-use OCPs were dominated by primary distribution patterns. In Harbin and Mohe, the concentrations of OCPs were highest in summer, followed by autumn and winter. No obvious seasonal variation was observed in Shenzhen associated with different cultivation types. At all three sites, OCPs were predominantly found in the gas phase, and higher percentages of particle-phase OCPs were observed in Harbin and Mohe than in Shenzhen. In this study, G/P partitioning models were used to study the G/P partitioning mechanism of OCPs. The Li-Ma-Yang model provided the most accurate prediction of the G/P partitioning behavior of OCPs with high molecular weights and low vapor pressures, particularly at low temperatures. However, OCPs with lower molecular weights and higher vapor pressures were predominantly in the equilibrium state, for which the Junge-Pankow model was suitable. This systematic cross-scale study provides new insights into pollution, G/P partitioning, and the environmental behavior of OCPs in the atmosphere.

Airborne Pesticides-Deep Diving into Sampling and Analysis

The escalating utilization of pesticides has led to pronounced environmental contamination, posing a significant threat to agroecosystems. The extensive and persistent global application of these chemicals has been linked to a spectrum of acute and chronic human health concerns. This review paper focuses on the concentrations of airborne pesticides in both indoor and outdoor environments. The collection of diverse pesticide compounds from the atmosphere is examined, with a particular emphasis on active and passive air sampling techniques. Furthermore, a critical evaluation is conducted on the methodologies employed for the extraction and subsequent quantification of airborne pesticides. This analysis takes into consideration the complexities involved in ensuring accurate measurements, highlighting the advancements and limitations of current practices. By synthesizing these aspects, this review aims to foster a more comprehensive and informed comprehension of the intricate dynamics related to the presence and measurement of airborne pesticides. This, in turn, is poised to significantly contribute to the refinement of environmental monitoring strategies and the augmentation of precise risk assessments.

Assessment of physicochemical properties of sorbent materials in passive and active sampling systems towards gaseous nitrogen-containing compounds

The adsorption and desorption behavior of volatile nitrogen-containing compounds in vapor phase by solid-phase microextraction Arrow (SPME-Arrow) and in-tube extraction (ITEX) sampling systems, were investigated experimentally using gas chromatography-mass spectrometry. Three different SPME-Arrow coating materials, DVB/PDMS, MCM-41, and MCM-41-TP and two ITEX adsorbents, TENAX-GR and MCM-41-TP were compared to clarify the selectivity of the sorbents towards nitrogen-containing compounds. In addition, saturated vapor pressures for these compounds were estimated, both experimentally and theoretically. In this study, the adsorption of nitrogen-containing compounds on various adsorbents followed the Elovich model well, while a pseudo-first-order kinetics model best described the desorption kinetics. Pore volume and pore sizes of the coating sorbents were essential parameters for the determination of the adsorption performance for the SPME-Arrow sampling system. MCM-41-TP coating with the smallest pore size gave the slowest adsorption rate compared to that of DVB/PDMS and MCM-41 in the SPME-Arrow sampling system. Both adsorbent and adsorbate properties, such as hydrophobicity and basicity, affected the adsorption and desorption kinetics in SPME-Arrow system. The adsorption and desorption rates of studied C₆H₁₅N isomers in the MCM-41 and MCM-41-TP sorbent materials of SPME-Arrow system were higher for dipropylamine and triethylamine (branched amines) than for hexylamine (linear chain amines). DVB/PDMS-SPME-Arrow gave fast adsorption rates for the aromatic-ringed pyridine and o-toluidine. All studied nitrogen-containing compounds demonstrated high desorption rates with DVB/PDMS-SPME-Arrow. Chemisorption and physisorption were the sorption mechanisms in MCM-41- and MCM-41-TP- SPME-Arrow, but additional experiments are needed to confirm this. An active sampling technique ITEX gave comparable adsorption and desorption rates on the selective MCM-41-TP and universal TENAX-GR sorbent materials for all the compounds studied. Vapor pressures of nitrogen-containing compounds were experimentally estimated by using retention index approach and these values were compared with the theoretical ones, calculated using the COnductor-like Screening MOdel for Real Solvent (COSMO-RS) model. Both values agreed well with those found in the literature proving that these methods can be successfully used in predicting VOC's vapor pressures, e.g. for the formation of secondary organic aerosols.

Simple multi-residue analysis of persistent organic pollutants and molecular tracers in atmospheric samples

We present a simple, selective and sensitive analytical method to quantitatively determine a wide range of halogenated persistent organic pollutants and molecular tracers in atmospheric samples. Identification and quantification was carried out by high-resolution gas chromatography, hyphenated with low-resolution mass spectrometry operating in electron impact (EI) and electron capture negative ionization (ECNI) mode. Optimization on a number of instrumental parameters was conducted to obtain ultra-trace detection limits, in the range of few fg/m³ for organohalogen compounds. Repeatability and reproducibility of the method was thoroughly evaluated. The analysis was validated with standard reference materials and successfully applied to actual atmospheric samples. The proposed multi-residue method provides a precise, affordable and practical procedure of sample analysis for environmental research laboratories with conventional instrumentation on a routine basis.•A simple combination of alumina, florisil and silica gel adsorbents was applied to sufficiently isolate polychlorinated biphenyls, organochlorine pesticides, polycyclic aromatic hydrocarbons, long chain n-alkanes, hopanes and steranes.•Full elution was achieved in two successive fractions, using small volumes of n-hexane and n-hexane/dichloromethane to recover all target substances.•To maximize analytical response, optimization was applied for three operating parameters in ECNI mode: i) ion source temperature; ii) emission current; and iii) electron energy.

Per- and polyfluoroalkyl substances and volatile methyl siloxanes in global air: Spatial and temporal trends

The study reports on the atmospheric concentrations of per- and polyfluoroalkyl substances (PFAS) and volatile methyl siloxanes (VMS) measured using sorbent-impregnated polyurethane foam disks (SIPs) passive air samplers. New results are reported for samples collected in 2017, which extends temporal trend information to the period 2009-2017, for 21 sites where SIPs have been deployed since 2009. Among neutral PFAS, fluorotelomer alcohols (FTOHs) had higher concentrations than perfluoroalkane sulfonamides (FOSAs) and perfluoroalkane sulfonamido ethanols (FOSEs) with levels of ND‒228, ND‒15.8, ND‒10.4 pg/m³, respectively. Among ionizable PFAS, the sum of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) in air were 0.128-781 and 6.85-124 pg/m³, respectively. Longer-chain i.e. C₉-C₁₄ PFAS, which are relevant to the recent proposal by Canada for a listing of long-chain (C₉-C₂₁) PFCAs to the Stockholm Convention, were also detected in the environment at all site categories including Arctic sites. Cyclic and linear VMS ranged between 1.34‒452 and 0.01-12.1 ng/m³, respectively, showing dominance in urban areas. Despite the wide range of levels observed across different site categories, geometric means of the PFAS and VMS groups were fairly similar when grouped according to the five United Nations regions. Variable temporal trends in air (2009-2017) were observed for both PFAS and VMS. PFOS, which has been listed in the Stockholm Convention since 2009, is still showing increasing tendencies at several sites, indicating constant input from direct and/or indirect sources. These new data inform international chemicals management for PFAS and VMS.

Accessibility investigation of semi-volatile organic compounds in indoor dust estimated by multi-ratio equilibrium passive sampling

Many semi-volatile organic compounds (SVOCs) accumulate in indoor dust, which serves as a repository for those compounds. The presence of SVOCs in indoor environments is of concern because many of them are suspected to have toxic effects. Total SVOC concentrations in the dust are generally used for exposure assessment to indoor contaminants, assuming that 100% of the SVOCs is accessible for human uptake. However, such an assumption may potentially lead to an overestimated risk related to dust exposure. We applied a multi-ratio equilibrium passive sampling (MR-EPS) for estimation of SVOC accessibility in indoor settled dust using silicone passive samplers and three particle size dust fractions, <0.25 mm, 0.25-0.5 mm, and 1-2 mm in dry and wet conditions. Equilibrations were performed at various sampler-dust mass ratios to achieve different degrees of SVOC depletion, allowing the construction of a desorption isotherm. The desorption isotherms provided accessible fractions (F_AS), equivalent air concentrations (C_AIR), dust-air partition coefficients (K_DUST-AIR) and organic carbon-air partition coefficients (K_OC-AIR). The highest F_AS were observed in the <0.25 mm dust fraction in wet conditions which is relevant for exposure assessment via oral ingestion. The highest C_AIR were estimated for several organophosphorus flame retardants (OPFRs), polycyclic aromatic hydrocarbons (PAHs) and synthetic musks. The logK_OC-AIR did not differ between dust particle sizes in dry and wet conditions but within compound groups, different relationships with hydrophobicity were observed. Equivalent lipid-based concentrations (C_L⇌DUST) calculated using available lipid-silicone partition coefficients (K_LIP-SIL) were compared with lipid-based concentrations (C_L) measured in human-related samples collected from Europeans. For hexachlorobenzene (HCB), C_L⇌DUST, and C_L were similar, indicating equilibrium attainment between environment and human samples. Lipid-based concentrations for persistent legacy contaminants were also similar but lower for PBDEs in human samples. Overall, accessibility estimation using MR-EPS in dust further contributes to human risk assessment.

Source Diversity of Intermediate Volatility n-Alkanes Revealed by Compound-Specific δ13C-δD Isotopes

Intermediate volatility organic compounds (IVOCs) are important precursors of secondary organic aerosols, and their sources remain poorly defined. N-alkanes represent a considerable portion of IVOCs in atmosphere, which can be well identified and quantified out of the complex IVOC pool. To investigate the potential source diversity of intermediate volatility n-alkanes (IVnAs, nC₁₂-nC₂₀), we apportioned the sources of IVnAs in the atmosphere of four North China cities, based on their compound-specific δ¹³C-δD isotope compositions and Bayesian model analysis. The concentration level of IVnAs reached 1195 ± 594 ng/m³. The δ¹³C values of IVnAs ranged -32.3 to -27.6‰ and δD values -161 to -90‰. The δD values showed a general increasing trend toward higher carbon number alkanes, albeit a zigzag odd-even prevalence. Bayesian MixSIAR model using δ¹³C and δD compositions revealed that the source patterns of individual IVnAs were inconsistent; the relative contributions of liquid fossil combustion were higher for lighter IVnAs (e.g., nC₁₂-nC₁₃), while those of coal combustion were higher for heavier IVnAs (e.g., nC₁₇-nC₂₀). This result agrees with principal component analysis of the dual isotope data. Overall, coal combustion, liquid fossil fuel combustion, and biomass burning contributed about 47.8 ± 0.1, 35.7 ± 4.0, and 16.3 ± 4.2% to the total IVnAs, respectively, highlighting the importance of coal combustion as an IVnA source in North China. Our study demonstrates that the dual-isotope approach is a powerful tool for source apportionment of atmospheric IVOCs.

Evidence of stockpile contamination for legacy polychlorinated biphenyls and organochlorine pesticides in the urban environment of Cyprus (Eastern Mediterranean): Influence of meteorology on air level variability and gas/particle partitioning based on equilibrium and steady-state models

The present study investigated comprehensively the atmospheric occurrence and fate of an extensive range of polychlorinated biphenyls (PCBs; forty-two congeners), organochlorine pesticides (OCPs; twenty-seven emerging and legacy agrochemicals) and polycyclic aromatic hydrocarbons (PAHs; fifty parent and alkylated members, including the non USEPA-16 listed toxic ones), in both gas and particulate phase of the scarcely monitored atmosphere over Cyprus for the first time. Parent-metabolite concentration ratios suggested fresh application for dichlorodiphenyl-trichloroethanes (DDTs), dicofol, hexachlorocyclohexanes, endosulfan and chlorothalonil, particularly during spring (April-May). Regressions of logarithms of partial pressure against ambient temperature revealed that secondary recycling from contaminated terrestrial surfaces regulates the atmospheric level variability of PCBs, DDTs, aldrin, chlordane, dicofol, heptachlor and endosulfan. Enthalpies of surface-air exchange (∆H_SA) calculated from Clausius-Clapeyron equations were significantly correlated to vaporization enthalpies (∆H_V) determined by chromatographic techniques, corroborating presence of potential stockpile-contaminated sites around the study area. The Harner-Bidleman equilibrium model simulating urban areas, and the Li-Jia empirical model, predicted better the partitioning behavior of PAHs (<four-ring parent and alkylated members), PCBs (<hexa-chlorobiphenyls), and OCPs, respectively. For heavier PAHs and PCBs, partitioning coefficients (K_P) were inadequately predicted by the Li-Ma-Yang steady-state model, probably due to local human activities and regional transport in the study area.

Fluorine mass balance analysis and per- and polyfluoroalkyl substances in the atmosphere

Given that only a small number of per- and polyfluoroalkyl substances (PFAS) are routinely monitored, levels of PFAS in the atmosphere may be underestimated. A protocol including analyses of target PFAS (n = 50), water-soluble fluoride, and total fluorine has been proposed and applied to atmospheric samples. The whole method recovery (including extraction recovery and sampling efficiency) of 90-110% were obtained for the majority of compounds (48/50) with low deviations between replicates (< 20%). Fluorotelomer alcohols were the most prevalent PFAS in the indoor air, while the outdoor air was dominated by the ultrashort-chain ionic PFAS (e.g., trifluoroacetic acid and perfluoropropanoic acid). Concentrations of organofluorine (OF) compounds calculated from the fluorine mass balance ranged from 1.74 ng F/m³ to 14.3 ng F/m³ and from 52.0 ng F/m³ to 1100 ng F/m³ in the particulate and gaseous phases, respectively, whereas only a minor proportion (around 1%) could be explained by target PFAS. In indoor air, OF compounds were observed in relatively high levels and with a shift to the fine particles (PM_<1) . Our results reveal a large proportion of unidentified OF signatures in the atmosphere and suggest the need to use multiple approaches to improve our understanding of airborne fluorinated substances.

Comparability of semivolatile organic compound concentrations from co-located active and passive air monitoring networks in Europe

Passive air sampling (PAS) has been used to monitor semivolatile organic compounds (SVOCs) for the past 20 years, but limitations and uncertainties persist in the derivation of effective sampling volumes, sampling rates, and concentrations. As a result, the comparability of atmospheric levels measured by PAS and concentrations measured by active air sampling (AAS) remains unclear. Long-term PAS data, without conversion into concentrations, provide temporal trends that are similar to, and consistent with, trends from AAS data. However, for more comprehensive environmental and human health assessments of SVOCs, it is also essential to harmonize and pool air concentration data from the major AAS and PAS monitoring networks in Europe. To address this need, we calculated and compared concentration data for 28 SVOCs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs)) at the six monitoring sites in Europe with 10 years of co-located AAS (EMEP) and PAS (MONET) data: Birkenes, Košetice, Pallas, Råö, Stórhöfði, and Zeppelin. Atmospheric SVOC concentrations were derived from PAS data using the two most common computation models. Long-term agreement between the AAS and PAS data was strong for most SVOCs and sites, with 79% of the median PAS-derived concentrations falling within a factor of 3 of their corresponding AAS concentrations. However, in both models it is necessary to set a sampler-dependent correction factor to prevent underestimation of concentrations for primarily particle-associated SVOCs. In contrast, the models overestimate concentrations at sites with wind speeds that consistently exceed 4 m s^-1. We present two recommendations that, if followed, allow MONET PAS to provide sufficiently accurate estimates of SVOC concentrations in air so that they can be deployed together with AAS in regional and global monitoring networks.

Assessment of Alkylated and Unsubstituted Polycyclic Aromatic Hydrocarbons in Air in Urban and Semi-Urban Areas in Toronto, Canada

22 alkylated polycyclic aromatic hydrocarbons (alk-PAHs) were characterized in ambient air individually for the first time in urban and semi-urban locations in Toronto, Canada. Five unsubstituted PAHs were included for comparison. Results from the measurements were used to estimate benzo[a]pyrene equivalent toxicity (BaPeq) of individual compounds in order to investigate the significance of a single compound in contributing to the overall toxic equivalency (TEQ) of air mixtures. To determine which compounds merit further investigation, BaPeq values of individual compounds were compared to the measured BaP toxicity. Our results showed that both unsubstituted and alkylated PAHs were more abundant in the urban area (38 and 30%, respectively). Benzo[a]pyrene levels at the urban location exceeded Ontario's 24 h guideline (40% of the events), and on average, it was 5 times higher than that at the semi-urban area. Gas-phase two- and three-ring compounds contributed up to 39% (urban) and 76% (semi-urban) of the TEQ of all compounds analyzed. Some alk-PAHs such as 7,12-dimethylbenzo[a]anthracene had a huge impact on the toxicity of urban air, and its BaPeq was on average 8 times higher than that of BaP. We emphasize that the toxic impact of alkylated and gaseous PAHs, which is not routinely included in many air monitoring programs, is significant and should not be neglected.

Aerial drone furnished with miniaturized versatile air sampling systems for selective collection of nitrogen containing compounds in boreal forest

A wide variety of nitrogen-containing compounds are present in the environment, which contributes to air pollution and new particle formation, for example. These eventually affect human health and the climate. With all this consideration, there is a growing interest in the development of efficient and reliable methods to determine these compounds in the atmosphere. In this study, titanium hydrogen phosphate-modified Mobil Composition of Matter No. 41 was used as sorbent material for in-tube extraction (ITEX) sampling system, to selectively collect nitrogen-containing compounds from natural air samples. The effect of sampling accessories, based on adsorbent coatings (with Tenax-GR as an adsorbent material) and polytetrafluoroethylene filters, was studied to improve the selectivity of the sampling system and to remove particles. Aerial drone with miniaturized air sampling system was employed for the reliable collection of nitrogen-containing compounds in both gas phase and aerosol particles. A total of 170 air samples were collected in July 2020 at the SMEAR II station, Finland to evaluate nitrogen-containing compounds diurnal patterns and vertical profiles (0.25, 5, 50, and 150 m). More than twenty nitrogen-containing compounds, such as aliphatic amines, imines, imidazoles, and pyridines, were identified, quantified or semi-quantified. The average concentrations of detected aliphatic amines at the altitude of 50 m were up to 40.4 ng m^-3 (dimethylamine) in gas phase and 128 ng m^-3 (ethylamine) in aerosol particles. Among nitrogen-containing compounds detected, pyridine gave the highest average concentration of 746 ng m^-3 in gas phase and 644 ng m^-3 in particle phase.

Seasonal variations in air concentrations of 27 organochlorine pesticides (OCPs) and 25 current-use pesticides (CUPs) across three agricultural areas of South Africa

For decades pesticides have been used in agriculture, however, the occurrence of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) is poorly understood in Africa. This study investigates air concentrations of OCPs and CUPs in three South African agricultural areas, their spatial/seasonal variations and mixture profiles. Between 2017 and 2018, 54 polyurethane foam-disks passive air-samplers (PUF-PAS) were positioned in three agricultural areas of the Western Cape, producing mainly apples, table grapes and wheat. Within areas, 25 CUPs were measured at two sites (farm and village), and 27 OCPs at one site (farm). Kruskal-Wallis tests investigated area differences in OCPs concentrations, and linear mixed-effect models studied differences in CUPs concentrations between areas, sites and sampling rounds. In total, 20 OCPs and 16 CUPs were detected. A median of 16 OCPs and 10 CUPs were detected per sample, making a total of 11 OCPs and 24 CUPs combinations. Eight OCPs (trans-chlordane, o,p'-/p,p'-dichlorodiphenyldichloroethylene (DDE)/dichlorodiphenyltrichloroethane (DDT), endosulfan sulfate, γ-hexachlorocyclohexane and mirex) and two CUPs (carbaryl and chlorpyrifos) were quantified in all samples. p,p'-DDE (median 0.14 ng/m³) and chlorpyrifos (median 0.70 ng/m³) showed the highest concentrations throughout the study. Several OCPs and CUPs showed different concentrations between areas and seasons, although CUPs concentrations did not differ between sites. OCPs ratios suggest ongoing chlordane use in the region, while DDT and endosulfan contamination result from past-use. Our study revealed spatial and seasonal variations of different OCPs and CUPs combinations detected in air. Further studies are needed to investigate the potential cumulative or synergistic risks of the detected pesticides.

Polycyclic aromatic hydrocarbon (PAH) accumulation in Quercus palustris and Pinus nigra in the urban landscape of Gothenburg, Sweden

Trees have the potential to improve urban air quality as leaves and needles capture air pollutants from the air, but further empirical data has been requested to quantify these effects. We measured the concentration of 32 polycyclic aromatic hydrocarbons (PAHs) in leaves of pin oak (Quercus palustris) and needles of black pine (Pinus nigra) in the City of Gothenburg, Sweden, during the summer of 2018. Oak leaves were collected twice (June, September), while one-year-old (C + 1) and three-year-old (C + 3) pine needles were sampled in June to study the temporal development of leaf/needle PAH concentrations. Specific leaf area (SLA) was estimated, which permitted calculation of leaf/needle area-based PAH content that were compared with the mass-based concentration. In addition, the air concentration of PAHs and NO₂ was measured using passive samplers. There was a strong correlation between air concentrations of PAH and NO₂, indicating that the pollutants to a large degree originate from the same sources. In the oak leaves there was a significant decrease in low molecular mass PAHs (L-PAH, mainly gaseous) between June and September, but a significant increase in high molecular mass PAHs (H-PAH, mainly particle-bound). There was a strong correlation between L-PAH concentration in leaves and in air indicating an influence of equilibrium processes between ambient air and leaf. In the pine needles, there was a significant increase of both L-PAH and H-PAH in three-year-old needles compared to one-year-old needles. Pine was superior to oak in accumulating PAHs from the air, especially for L-PAHs when comparing area-based content. However, H-PAH concentrations were higher in oak leaves compared to pine needles on a leaf mass basis, emphasizing the importance of how concentrations are expressed. The results from this study can contribute to the development of urban planning strategies regarding the effect of vegetation on air quality.

Quantitative analysis and spatial and temporal distribution of volatile organic compounds in atmospheric air by utilizing drone with miniaturized samplers

Our second generation air sampling drone system, allowing the simultaneous use of four solid phase microextraction (SPME) Arrow and four in-tube extraction (ITEX) units, was employed for collection of atmospheric air samples at different spatial and temporal dimensions. SPME Arrow coated with two types of materials and ITEX with 10% polyacrylonitrile as sorbent were used to give a more comprehensive chemical characterization of the collected air samples. Before field sampling, miniaturized samplers went through quality control and assurance in terms of reproducibility (RSD ≤14.1%, N = 4), equilibrium time (≥10 min), breakthrough volume (1.8 L) and storage time (up to 48 h). 128 air samples were collected under optimal sampling conditions from July to September 2019 at the SMEAR II station and Qvidja farm, Finland. 347 VOCs were identified in the air samples either on-site or in the laboratory by thermal desorption gas chromatography - mass spectrometry, and they were quantified/semiquantified using Partial Least Squares Regression models. Individual models were developed for the different coatings and packing materials using gas phase standards obtained by an automatic permeation system. Average gas phase VOC concentrations ranged from 0.1 (toluene, the SMEAR II station) to 680 ng L^-1 (acetone, Qvidja farm). Average VOC concentrations in aerosols ranged from 0.1 (1,4-cyclohexadiene, the SMEAR II station) to 2287 ng L^-1 (megastigma-4,6,8-triene, Qvidja farm). Clear differences in results were seen for samples collected at the SMEAR II station and Qvidja farm, between VOC compositions in gas phase and aerosols, and between the sampling site and height.

Simultaneous analysis of neutral and ionizable per- and polyfluoroalkyl substances in air

A new method is preliminarily validated for the simultaneous analysis of ionic and neutral per- and polyfluoroalkyl substances (PFASs) in both particulate and gaseous phases in air using a nanosampler-20 air sampler (NS20) composed of quartz fiber filters (QFFs), polyurethane foam (PUF) and artificial activated charcoal (GAIAC™). Perfluoroalkane sulfonamido ethanols (FOSEs) mainly remained in PUF, whereas the other neutral analytes were mainly found in GAIAC. Satisfactory recoveries were obtained for FOSEs, fluorotelomer alcohols (FTOHs), fluorotelomer iodides (FTIs), ranging fron 70%-120%, moderate recoveries were achieved for perfluorinated iodine alkanes (FIAs) and diiodofluoroalkanes (FDIAs), ranging from 50%-70%, while poor recoveries were found for perfluoroalkane sulfonamides (FOSAs). Breakthrough experiments revealed that almost all the target analytes were well trapped in GAIAC™, including the very volatile 4:2 FTOH. Applying to real sampling, our results showed that 6:2 and 8:2 FTOH were the most abundant species, with levels detected at 190 pg/m³ and 160 pg/m³. To the best of our knowledge, FDIAs were detected in ambient air for the first time at an average level of 8.3 pg/m³. Overall, the profiles observed from the real air samples reflected current industrial transition from longer chain to shorter chain in PFAS production. Our results revealed that the current method is promising for a more comprehensive understanding on the fates of PFASs in air.

High spatial resolution measurements of passive-sampler derived air concentrations of persistent organic pollutants in the Campania region, Italy: Implications for source identification and risk analysis

Because most relevant studies have used small sample sizes, to date, representative atmospheric monitoring of persistent organic pollutants (POPs) on a regional scale has been very limited, which makes it difficult to precisely identify "hotspots" and possible pollution sources. In this study, an ultrahigh resolution monitoring technique was used to measure the atmospheric spatial variations in POP concentrations on a regional scale, throughout Campania, Italy. The occurrence of specific POPs-including polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs) and phthalate esters (PAEs)-were investigated using polyurethane foam-based passive air samplers (PUF-PAS), which were deployed at 129 sites across the Campania Territory between April and July 2016. The results show that the highest POP levels occurred in the Naples metropolitan area (NMA), although there were other problematic spots throughout the Territory. More specifically, hotspot areas in the NMA that depict serious POP pollution were found in the Bagnoli brownfield site, Sarno River Basin, and parts of the northeastern NMA sector. The atmospheric POP contamination in Campania is jointly controlled by the contributions of local emissions and long-range atmospheric transport. Diffusion model was employed to identify the potential sources of various POPs. The simulation showed that all the POP sources are located in the NMA and are closely related to industrial sites. This study demonstrates the advantage of using large sample sizes to identify POP source locations and achieve geospatial visualization of POP concentration and risk assessment levels.

Main sources controlling atmospheric burdens of persistent organic pollutants on a national scale

National long-term monitoring programs on persistent organic pollutants (POPs) in background air have traditionally relied on active air sampling techniques. Due to limited spatial coverage of active air samplers, questions remain (i) whether active air sampler monitoring sites are representative for atmospheric burdens within the larger geographical area targeted by the monitoring programs, and thus (ii) if the main sources affecting POPs in background air across a nation are understood. The main objective of this study was to explore the utility of spatial and temporal trends in concert with multiple modelling approaches to understand the main sources affecting polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in background air across a nation. For this purpose, a comprehensive campaign was carried out in summer 2016, measuring POPs in background air across Norway using passive air sampling. Results were compared to a similar campaign in 2006 to assess possible changes over one decade. We furthermore used the Global EMEP Multi-media Modeling System (GLEMOS) and the Flexible Particle dispersion model (FLEXPART) to predict and evaluate the relative importance of primary emissions, secondary emissions, long-range atmospheric transport (LRAT) and national emissions in controlling atmospheric burdens of PCB-153 on a national scale. The concentrations in air of both PCBs and most of the targeted OCPs were generally low, with the exception of hexachlorobenzene (HCB). A limited spatial variability for all POPs in this study, together with predictions by both models, suggest that LRAT dominates atmospheric burdens across Norway. Model predictions by the GLEMOS model, as well as measured isomeric ratios, further suggest that LRAT of some POPs are dictated by secondary emissions. Our results illustrate the utility of combining observations and mechanistic modelling approaches to help identify the main factors affecting atmospheric burdens of POPs across a nation, which, in turn, may be used to inform both national monitoring and control strategies.

Per- and polyfluoroalkyl substances in surface water, gas and particle in open ocean and coastal environment

A simultaneous sampling of atmospheric and seawater samples was performed in the Taiwan Western Strait, western Arctic Ocean, and the Antarctic Ocean. Analysis of both particle and gas phase PFAS in oceanic air was conducted using cascade impactor particle fractionator, cryogenic air sampler and activated charcoal fiber sorbent for the first time with application in the Taiwan Western Strait. Mean concentration of Σ₁₂PFAS in surface seawater and atmospheric samples were 1178 pg/L and 24 pg/m³ in the Taiwan Western Strait, 430 pg/L and 6 pg/m³ in the western Arctic Ocean, and 456 pg/L and 3 pg/m³ in the Antarctic Ocean. In oceanic air from the Taiwan Western Strait, fluorotelomer alcohol (FTOH) and the ionic PFAS [perfluoroalkyl sulfonic acid (PFSA) and perfluoroalkyl carboxylic acid (PFCA)] were found in 76% and 7% respectively. Regional comparison of air/water exchange (K_AW) and gas-particle (K_p) partition coefficients of PFAS in the oceanic environment indicated potential partitioning of ionic PFAS between surface seawater and oceanic air. These findings highlight the advancement in atmospheric PFAS measurements through combined novel technologies, namely size-fractionated particle sampling with cryogenic air trapping and/or activated charcoal sorption. Correlation between K_p and carbon chain length of PFAS was observed using both hyphenated techniques.

Partitioning between polyurethane foam and the gas phase: data compilation, uncertainty estimation and implications for air sampling

Polyurethane foam (PUF) is frequently applied for sampling semi-volatile organic compounds (SVOCs) in the gas phase. Equilibrium partition coefficients (KPUF/G) often are used to estimate the potential for breakthrough during active air sampling (AAS) and to correct for non-linear uptake during passive air sampling (PAS). KPUF/G is either determined experimentally or estimated, in both cases incurring uncertainties that can be carried over to other parameters. Here, a dataset of 547 measured KPUF/G values and chemical information for 281 distinct chemicals was compiled from the peer reviewed literature. Measured log KPUF/G were compared with predicted values to identify potential bias in data generated with a particular experimental approach. An analysis of the measured data suggests that the uncertainty of unbiased log KPUF/G values is at best 0.2 log units at 15 °C (e.g. for hexachlorobenzene and fluoranthene), but most likely much higher. This implies that inherent passive air sampling rates obtained from the loss of a depuration compound (SR) and breakthrough volumes during AAS can presently not be known with an uncertainty of less than ca. 50%. During short PAS deployment periods, the uncertainty in the effective sampling volume (Vair) derives mainly from the uncertainty in the SR, whereas the uncertainty in KPUF/G of the target compound will become important and even the main source of uncertainty for Vair if deployments are long or target chemicals are relatively volatile. This in turn implies that the uncertainty of Vair cannot be smaller than the uncertainty of SR and KPUF/G and therefore again is at least ca. 50%. We strongly recommend that the uncertainty of air concentrations obtained by non-linear PAS is quantified and reported and we outline a procedure on how to do that. Because the uncertainty in KPUF/G of target and depuration chemicals generally exceeds 30%, it may often be necessary to conduct Monte Carlo simulation.

Mobility and environmental monitoring of pesticides in the atmosphere - a review

Knowledge of the partition mechanisms in the agrochemical environment is fundamental for understanding their behavior within an ecosystem and mitigating possible adverse effects of these products. In this review, the objective was to present the main transport mechanisms, physical-chemical properties, and atmospheric monitoring methodologies of the most diverse types of agrochemicals used in agriculture that can reach the atmosphere and affect different compartments. It has been verified that volatilization is one of more considerable significance of the various forms of transport since a significant part of the applied pesticides can volatilize in a few days. As for monitoring these compounds in the atmosphere, both passive and active sampling have their advantages and disadvantages. Passive samplers allow sampling in large quantities and at remote locations, in addition to making continuous measurements, while active samplers have the advantage of being able to detect low concentrations and continuously. Since a significant portion of the applied pesticides is directed to the atmosphere, monitoring makes it possible to understand some properties of the pesticides present in the air. This monitoring can be done from different existing methodologies based on adopted criteria and existing technical standards. Graphical representation of mobility and environmental monitoring of atmospheric pollutants from pesticides.

ES&T in the 21st Century: A Data-Driven Analysis of Research Topics, Interconnections, And Trends in the Past 20 Years

Environmental Science & Technology (ES&T) has served a leadership role in reporting advanced and significant research findings for decades and accumulated tremendous amount of high-quality literature. In this study, we developed tailored text mining methods and analyzed 29 188 papers published in ES&T from 2000 to 2019, and we performed data-driven analyses to reveal some critical information and guidance on what has been published, what topical changes have evolved, and what are the areas that deserve additional attention. While top research keywords remained stable (water, sorption, soil, emiss, oxid, exposur), the trending up and emerging keywords showed clear shift over the years. Keywords related to nanobased materials (nanoparticl, nanomateri, carbon nanotub), climate and energy (climat, ch4, greenhouse gas emiss, mitig, energi), and health (exposur, health, ingest) demonstrated the strongest uptrend in the past 10 years, while plastics and PFAS were among clear emerging topics in the past 5 years. Co-occurrence analysis showed distinct associations between media (water, soil, air, sediment), chemicals (pcb, humic subst, particulate matt), processes (sorption, remov, degrad), and properties (kinet, mechan, speciat). Furthermore, a rule-based classification deciphered trends, distributions, and interconnections of articles based on either monodomains (air, soil, solid waste, water, and wastewater) or multidomains. It found water and wastewater cross-discipline articles tended to have higher citation values, while air domain tended to stand alone. Water and air monodomains consistently increased their shares in publications (together 56.3% in 2019), while shares of soil studies gradually declined. This study provides new data-driven methods on literature mining and offers unique insights on environmental research landscape and opportunities.

Application of polyoxymethylene passive air sampler to monitor hydrophobic organics in air around a confined disposal facility

Volatile losses of hydrophobic organic contaminants from a confined disposal facility (CDF) containing dredged contaminated sediments is of substantial concern to surrounding communities. A partitioning passive sampling approach using polyoxymethylene (POM) was applied to measure long-term average (weeks to months) air concentrations resulting from evaporation at a CDF. Measurements at 10 locations surrounding the CDF using the POM air samplers indicated that the highest concentrations of ΣPCBs∼13 ng/m³ and ΣPAHs ∼65 ng/m³ were measured during an active dredge material placement period when the average temperature was 23 °C. The measurements were dominated by the more volatile, lower molecular weight compounds of each type. Partitioning to the POM during the post dredge material placement period with average temperature of 5 °C was corrected for temperature and the measured ∑PCBs and ∑PAHs were ∼3 ng/m³ and 45 ng/m³ respectively. The partitioning passive sampling measurements agreed well with the available weekly 24-h high-volume air samples (HVAS) averaged over the POM equilibration time for lower congener number PCBs (15, 18, 20/28 and 31) and naphthalene but were as much as 10 times lower than HVAS for high molecular weight PAHs. The difference was likely the result of the greater association of these PAHs with particulates and sources other than evaporation from the CDF. The POM air sampler achieved the goal of providing a long-term average air concentration without having to collect, analyze and average multiple HVAS samples although the technique is largely limited to the lower molecular weight PAHs and PCBs and different equilibration times for different compounds complicate its use and analysis.

Atmospheric diffusion of perfluoroalkyl acids emitted from fluorochemical industry and its associated health risks

The fluorochemical industry is an important emission source of atmospheric perfluoroalkyl acids (PFAAs). In this study, air samples were collected through active high-volume air samplers coupled with Tissuquartz™ filters around a fluorochemical manufacturer, and analyzed for PFAAs levels. Perfluorooctanoic acid (PFOA) was dominant with concentrations as high as 9730 pg/m³, followed by short chain perfluoroalkyl carboxylic acids (PFCAs). The PFAAs in the air were compared to those measured in outdoor dust and rain collected in the same area. Short chain PFCAs had a greater distribution in air, while PFOA was more distributed in dust and rain. With increasing concentrations, a significant decreasing trend for PFOA was observed in rain (P < 0.05). The estimated daily intake (EDI) of PFOA via indoor air inhalation by five age groups were calculated in two scenarios, and compared to the strictest tolerable daily intake (TDI) of PFOA (≤0.63 ng/kg bw/day). Potential health risk occurred in the best-case scenario, while the EDI from the worst-case scenario was comparable to that via indoor dust ingestion, indicating a notable health risk. This suggests that in terms of PFOA exposure and health risks, air inhalation may be as important as dust ingestion. These results highlight the impacts of PFAAs emissions from the fluorochemical industry to the atmosphere and ultimately, human health.

Emerging investigator series: air conditioning filters as a sampler for semi-volatile organic compounds in indoor and near-building air

Organic compounds like flame retardants (FRs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) are consistently found in both indoor and outdoor environments. There are many possible matrices for measurement of these compounds (e.g. indoor dust, air - passive and active air samples), but all methods have limitations, like the heterogeneous distribution of indoor dust, or noisy active air samplers. We used filters from building-wide heating, ventilation and air conditioning (HVAC) units to evaluate levels of PAHs, PCBs, OCPs and NFRs in indoor and outdoor environments, and to evaluate whether this method is feasible for screening semivolatile organic compounds (SVOCs) in indoor and near-building outdoor environments. Detectable levels of FRs, PCBs, OCPs and PAHs were found, demonstrating that HVAC filters do collect SVOCs, with generally higher levels of PAHs in the incoming air filters and higher levels of PCBs, OCPs and FRs in the outgoing air filters. Levels of FRs, PCBs and OCPs in outgoing air were comparable to those measured using conventional active air sampling in the same building. The advantages of using HVAC filters are (1) integrated and homogeneous samples, as the whole building is sampled over typically a long timescale (months), and (2) samples are easy and cheap to collect and do not require prior deployment of samplers. The key disadvantage is that HVAC filters are not designed for analytical chemistry and thus the filter materials can have variable or unknown gas sorption and particle capture, and can have strong matrix effects during analysis.

Influence of Foam Characteristics on the Aviation Coolants' Pollution Degree

The particulate contamination degree of aviation coolants (ACs) is overestimated commonly because the bubbles in ACs are erroneously recognized as particulate contaminants during the measurement process. In this work, the factors that influence the foam behavior and contamination degree of ACs are investigated. It is evidenced that the foam behavior of ACs is basically unaffected by the ratio of glycol to water of the base solution, which, however, is highly influenced by the organic additive. Also, the more the organic additive arranged at the gas-liquid interface, the lower the surface tension of glycol aqueous (GA) solution and the higher the contamination degree. Furthermore, the foam characteristics and contamination degree of ACs are highly affected by the working conditions, such as airflow, operating temperature, and gas pressure. Besides, the defoaming rate can be accelerated by adding an antifoaming agent or ultrasonic processing; however, the defoaming effect of the natural static method and pressuring positively treatment is disappointing. To further improve the defoaming effect, several efficient synergetic methods of defoaming have been proposed.

Qualitative assessment of 27 current-use pesticides in air at 20 sampling sites across Africa

Increasing use of current-use pesticides (CUPs) in Africa raises environmental and public health concerns. But there is a large uncertainty about their occurrence and the composition of pesticide mixtures on this continent. This paper investigates the presence of 27 CUPs in air across 20 sampling sites in Africa. 166 passive air samples, consisting of polyurethane foam (PUF), were collected in 12 African countries between 2010 and 2018. Samples were extracted with methanol and analyzed via high-performance liquid chromatography coupled with tandem mass spectrometry. The detection frequencies of CUPs per site were compared to land use patterns and sampling years, while their similarities were assessed using hierarchical cluster analysis. Overall, 24 CUPs were detected at least once. In 93% of all samples, at least one CUP was detected, while 78% of the samples had mixtures of two or more CUPs (median 3, interquartile range 5). Atrazine and chlorpyrifos were detected in 19 out of 20 sampling sites. Carbaryl, metazachlor, simazine, tebuconazole and terbuthylazine had the highest detection frequencies at sampling sites dominated by croplands. Across all the sampling years, 16 CUPs were present. Seven CUPs were newly detected from 2016 onwards (azinfos-methyl, dimetachlor, chlorsulfuron, chlortoluron, isoproturon, prochloraz and pyrazon), while metamitron was only present before 2012. Sites within a radius of about 200 km showed similarities in detected CUP mixtures across all samples. Our results show the presence of CUP mixtures across multiple agricultural and urban locations in Africa which requires further investigation of related environmental and human health risks.

Multi-year atmospheric concentrations of per- and polyfluoroalkyl substances (PFASs) at a background site in central Europe

A total of 74 high volume air samples were collected at a background site in Czech Republic from 2012 to 2014 in which the concentrations of 20 per- and polyfluoroalkyl substances (PFASs) were investigated. The total concentrations (gas + particle phase) ranged from 0.03 to 2.08 pg m^-3 (average 0.52 pg m^-3) for the sum of perfluoroalkyl carboxylic acids (∑PFCAs), from 0.02 to 0.85 pg m^-3 (average 0.28 pg m^-3) for the sum of perfluoroalkyl sulfonates (ΣPFSAs) and from below detection to 0.18 pg m^-3 (average 0.05 pg m^-3) for the sum of perfluorooctane sulfonamides and sulfonamidoethanols (ΣFOSA/Es). The gas phase concentrations of most PFASs were not controlled by temperature dependent sources but rather by long-range atmospheric transport. Air mass backward trajectory analysis showed that the highest concentrations of PFASs were mainly originating from continental areas. The average particle fractions (θ) of ΣPFCAs (θ = 0.74 ± 0.26) and ΣPFSAs (θ = 0.78 ± 0.22) were higher compared to ΣFOSA/Es (θ = 0.31 ± 0.35). However, they may be subject to sampling artefacts. This is the first study ever reporting PFASs concentrations in air samples collected over consecutive years. Significant decreases in 2012-2014 for PFOA, MeFOSE, EtFOSE and ∑PFCAs were observed with apparent half-lives of 1.01, 0.86, 0.92 and 1.94 years, respectively.

Development of polyoxymethylene passive sampler for assessing air concentrations of PCBs at a confined disposal facility (CDF)

In this study, 76 μm polyoxymethylene (POM) strips were evaluated as a passive air sampler (PAS) for monitoring the volatile emissions from dredged material placed in confined disposal facilities (CDF). Laboratory evaluations were used to assess the uptake kinetics, average equilibrium time, and estimate the POM-air partition coefficients (K_POM-A) of 16 PCB congeners. The uptake kinetics defined the effective averaging time for air sampling and ranged from about a week for dichlorobiphenyls to 2 weeks or more for tetra- and pentachlorobiphenyls at ∼20 °C under internal mass transfer resistance control which was applicable for Log K_POM-A < 8. The measured Log K_POM-A for PCBs ranged from 5.65 to 9.34 and exhibited an average deviation of 0.19 log unit from the theoretical value of K_POM-W/K_AW. The PAS approach was then tested with a preliminary field application (n = 17) at a CDF allowing equilibration over 42 days. The field application focused on lower congener PCBs as a result of the estimated increase in K_POM-A and longer uptake times expected at the low ambient temperatures during the field study (average of 3.5 °C). Total PCB air concentrations around the CDF averaged 0.32 ng/m³ and varied according to proximity to placement of the dredged materials and predominant wind directions. Average PAS concentration of low congener number PCBs (15, 18, 20/28, 31) were compared to available high volume air sampler (HVAS) measurements. The PAS concentrations were within 20% of HVAS in the dominant north and south directions and showed similar trends as east and west HVAS samplers although PAS concentrations were as much as an order of magnitude below the west HVAS.

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.

Airborne phthalates in indoor environment: Partition state and influential built environmental conditions

Exposure to phthalates has recently become a major public health concern. The information of indoor airborne phthalates and their air-particle partition in real indoor environmental condition is still limited. In this study, the gas- and PM_2.5-concentrations of 7 phthalates in 40 residences were concurrently measured in summer and winter. The major phthalates (median concentration in the summer and winter, respectively) in indoor air were DMP (2442.3 and 2403.4 ng/m³), DiBP (801.0 and 640.0 ng/m³) and DnBP (5173.2 and 1379.6 ng/m³), whereas the major phthalates in PM_2.5 were DiBP (1055.1 and 585.9 ng/m³) and DnBP (1658.5 and 1517.0 ng/m³) and DEHP (215.1 and 344.9 ng/m³). Air-PM_2.5 partition coefficients (K_p) of DiBP, DnBP and DEHP were calculated: the summer and winter median values (m³/μg) were 0.053 and 0.011 for DiBP, 0.010 and 0.004 for DnBP, 0.021 and 0.025 for DEHP, respectively. Air-PM_2.5 partition of DiBP and DnBP approached equilibrium, while that of DEHP did not reach equilibrium in either season. The impacts of built environmental conditions on phthalate concentrations were characterized. Elevated temperature resulted in accumulation of airborne phthalates. Higher air humidity led to more water absorption of aerosols in summer, facilitated mass transfer of phthalates from air to PM_2.5, and resulted in greater K_p of DiBP and DnBP in the summer. Any factors such as proximity to local traffic highway and indoor smoking activities, which can increase indoor PM_2.5 concentrations, resulted in significantly higher airborne phthalate concentrations. Improving ventilation was not an effective measure to reduce indoor airborne phthalate concentrations.

Triple Isotopes (δ13C, δ2H, and Δ14C) Compositions and Source Apportionment of Atmospheric Naphthalene: A Key Surrogate of Intermediate-Volatility Organic Compounds (IVOCs)

Naphthalene (NAP), as a surrogate of intermediate-volatility organic compounds (IVOCs), has been proposed to be an important precursor of secondary organic aerosol (SOA). However, the relative contribution of its emission sources is still not explicit. This study firstly conducted the source apportionment of atmospheric NAP using a triple-isotope (δ¹³C, δ²H, and Δ¹⁴C) technique combined with a Bayesian model in the Beijing-Tianjin-Hebei (BTH) region of China. At the urban sites, stable carbon (-27.7 ± 0.7‰, δ¹³C) and radiocarbon (-944.0 ± 20.4‰, Δ¹⁴C) isotope compositions of NAP did not exhibit significant seasonal variation, but the deuterium system showed a relatively more ²H depleted signature in winter (-86.7 ± 8.9‰, δ²H) in comparison to that in summer (-56.4 ± 3.9‰, δ²H). Radiocarbon signatures indicated that 95.1 ± 1.8% of NAP was emitted from fossil sources in these cities. The Bayesian model results indicated that the emission source compositions in the BTH urban sites had a similar pattern. The contribution of liquid fossil combustion was highest (46.7 ± 2.6%), followed by coal high-temperature combustion (26.8 ± 7.1%), coal low-temperature combustion (18.9 ± 6.4%), and biomass burning (7.6 ± 3.1%). At the suburban site, the contribution of coal low-temperature combustion could reach 70.1 ± 6.4%. The triple-isotope based approach provides a top-down constraint on the sources of atmospheric NAP and could be further applied to other IVOCs in the ambient atmosphere.

Polyurethane foam-based passive air sampling for simultaneous determination of POP- and PAH-related compounds: A case study in informal waste processing and urban areas, northern Vietnam

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexabromobiphenyl (BB-153), novel brominated flame retardants (NBFRs), and unsubstituted/methylated polycyclic aromatic hydrocarbons (PAHs/Me-PAHs) were simultaneously monitored in the air samples collected from Vietnamese urban and vehicular waste processing areas by using polyurethane foam-based passive air sampling (PUF-PAS) method. Concentrations (pg m^-3) of organic pollutants decreased in the order: PAHs (median 29,000; range 5100-100,000) > Me-PAHs (6000; 1000-33,000) > PCBs (480; 170-1100) > PBDEs (11; 5.3-86) > NBFRs (0.20; n. d. - 51) > BB-153 (n.d.). The difference in total PCB and PBDE concentrations between the urban and waste processing air samples was not statistically significant. Meanwhile, levels of PAHs, Me-PAHs, benzo [a]pyrene equivalents (BaP-EQs), and toxic equivalents of dioxin-like PCBs (WHO-TEQs) were much higher in the waste processing sites. This is the first report on the abundance of mono- and di-CBs (notably CB-11) in the air from a developing country, suggesting their roles as emerging and ubiquitous air pollutants. Our results have indicated potential sources of specific organic pollutants such as dioxin-like PCBs, PAHs, and Me-PAHs from improper treatment of end-of-life vehicles and other vehicle related materials (e.g., waste oils and rubber tires), as well as current emission of PCBs and PBDEs in the urban area in Vietnam. Further atmospheric monitoring studies should be conducted in this developing country that cover both legacy and emerging contaminants with a focus on areas affected by rapid urbanization and informal waste processing activities.

Assessment of Occupational Exposure to Organic Flame Retardants: A Systematic Review

BACKGROUND

Flame retardants (FRs) are widespread in common goods, and workers in some industries can be exposed to high concentrations. Numerous studies describe occupational exposure to FRs, but the diversity of methods and of reported results renders their interpretation difficult for researchers, occupational hygienists, and decision makers.

OBJECTIVES

The objectives of this paper are to compile and summarize the scientific knowledge on occupational exposure to FRs as well as to identify research gaps and to formulate recommendations.

METHODS

Five databases were consulted for this systematic literature review (Embase, Medline [Pubmed], Global health, Web of Science, and Google Scholar), with terms related to occupational exposure and to FRs. Selected studies report quantitative measurements of exposure to organic FRs in a workplace, either in air, dust, or in workers' biological fluids. The Preferred Reporting Items for Systematic reviews and Meta-Analyses statement guidelines were followed.

RESULTS

The search yielded 1540 published articles, of which 58 were retained. The most frequently sampled FRs were polybrominated diphenyl ethers and novel brominated FRs. Offices and electronic waste recycling facilities were the most studied occupational settings, and the highest reported exposures were found in the latter, as well as in manufacturing of printed circuit boards, in aircrafts, and in firefighters. There were recurrent methodological issues, such as unstandardized and ill-described air and dust sampling, as well as deficient statistical analyses.

CONCLUSIONS

This review offers several recommendations. Workplaces such as electronic waste recycling or manufacturing of electronics as well as firefighters and aircraft personnel should be granted more attention from researchers and industrial hygienists. Methodical and standardized occupational exposure assessment approaches should be employed, and data analysis and reporting should be more systematic. Finally, more research is needed on newer chemical classes of FRs, on occupational exposure pathways, and on airborne FR particle distribution.

Theory and modelling approaches to passive sampling

Designs and applications of passive samplers for various environmental compartments have been broadened significantly since their introduction. Understanding the theory behind passive sampling is essential for proper development of sampling methods and for accurate interpretation of the results. Theoretical underpinnings of passive sampling have been explored using different approaches. The aim of this review is to describe passive sampling theory and modelling approaches presented in the literature in a manner that allows researchers to obtain comprehensive understanding of them and to recognize the assumptions behind each approach together with their applicability to a given passive sampling technique. A common approach originates from Whitman's two-film theory and produces an exponential model that describes the entire passive sampling process. This approach, however, is based on several assumptions including linear exchange kinetics between the sampled medium and the passive sampler. Two-phase air passive samplers with a well-defined barrier are commonly modeled based on the zero-sink assumption, which assumes efficient trapping of analytes in the receiving phase. This assumption may become invalid under various scenarios; consequently, other approaches to modelling have been introduced including simulation of the sampling process by approximate temporal-steady states in hypothetical segments in the adsorption phase. Another approach uses dynamic models to determine accumulation of analytes in passive samplers. Dynamic models are capable of describing mass accumulation in the passive sampler, its transient response, and its response to fluctuations in environmental concentrations. Finally, empirically calibrated models, attempting to simplify the process of passive sampling rate determination, are also presented. In general, dynamic models are used to establish a profound understanding of the sampling process and analyse the applicability of the simpler models and their assumptions, while the simplified models are desirable and practical for most users. Nonetheless, due to the advancement in the computational tools, application of the dynamic models could be made simple and user-friendly.

Comparability of long-term temporal trends of POPs from co-located active and passive air monitoring networks in Europe

The comparability of data from active (ACT) and passive sampling (PAS) of persistent organic pollutants (POPs) in air is hindered by uncertainties related to the derivation of sampling rates and concentrations, as well as differences in the duration, volume and frequency of sampling. Although data from ACT have been used extensively in short-term PAS calibration studies, no attempts have been made to evaluate the comparability of long-term trends calculated from PAS to established ACT trends. This is crucial, as continuous long-term ACT is unfeasible in most regions of the world. To address these challenges, we calculated and compared trends for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) at the six sites in Europe with at least 5 years of co-located ACT and PAS data (2012-2016): Birkenes, Košetice, Pallas, Råö, Stórhöfði and Zeppelin. Strong agreement of ACT and PAS trends was observed for most OCPs and PCBs. Apart from two PCBs at Stórhöfði, all pairs of ACT and PAS trends followed the same direction. However, differences in the magnitude, significance and confidence intervals of their slopes were observed for some compounds and were primarily attributed to the short duration of the PAS time series. Despite some limitations, our results suggest that the comparability of ACT and PAS POP trends will continue to improve with additional years of data. This study confirms the suitability of PAS for the calculation of long-term POP trends in air, and highlights the importance of continuous sampling at established monitoring sites with consistent analytical methods.

Sources and dynamics of semivolatile organic compounds in a single-family residence in northern California

Semivolatile organic compounds (SVOCs) emitted from building materials, consumer products, and occupant activities alter the composition of air in residences where people spend most of their time. Exposures to specific SVOCs potentially pose risks to human health. However, little is known about the chemical complexity, total burden, and dynamic behavior of SVOCs in residential environments. Furthermore, little is known about the influence of human occupancy on the emissions and fates of SVOCs in residential air. Here, we present the first-ever hourly measurements of airborne SVOCs in a residence during normal occupancy. We employ state-of-the-art semivolatile thermal-desorption aerosol gas chromatography (SV-TAG). Indoor air is shown consistently to contain much higher levels of SVOCs than outdoors, in terms of both abundance and chemical complexity. Time-series data are characterized by temperature-dependent elevated background levels for a broad suite of chemicals, underlining the importance of continuous emissions from static indoor sources. Substantial increases in SVOC concentrations were associated with episodic occupant activities, especially cooking and cleaning. The number of occupants within the residence showed little influence on the total airborne SVOC concentration. Enhanced ventilation was effective in reducing SVOCs in indoor air, but only temporarily; SVOCs recovered to previous levels within hours.

Fully Automated Online Dynamic In-Tube Extraction for Continuous Sampling of Volatile Organic Compounds in Air

Comprehensive and time-dependent information (e.g., chemical composition, concentration) of volatile organic compounds (VOCs) in atmospheric, indoor, and breath air is essential to understand the fundamental science of the atmosphere, air quality, and diseases diagnostic. Here, we introduced a fully automated online dynamic in-tube extraction (ITEX)-gas chromatography/mass spectrometry (GC/MS) method for continuous and quantitative monitoring of VOCs in air. In this approach, modified Cycle Composer software and a PAL autosampler controlled and operated the ITEX preconditioning, internal standard (ISTD) addition, air sampling, and ITEX desorption sequentially to enable full automation. Air flow passed through the ITEX with the help of an external pump, instead of plunger up-down strokes, to allow larger sampling volumes, exhaustive extraction, and consequently lower detection limits. Further, in order to evaluate the ITEX system stability and to develop the corresponding quantitative ITEX method, two laboratory-made permeation systems (for standard VOCs and ISTD) were constructed. The stability and suitability of the developed system was validated with a consecutive 19 day atmospheric air campaign under automation. By using an electrospun polyacrylonitrile nanofibers packed ITEX, selective extraction of some VOCs and durability of over 1500 extraction and desorption cycles were achieved. Especially, the latter step is critically important for on-site long-term application at remote regions. This ITEX method provided 2-3 magnitudes lower quantitation limits than the headspace dynamic ITEX method and other needle trap methods. Our results proved the excellence of the fully automated online dynamic ITEX-GC/MS system for tracking VOCs in the atmospheric air.

Molecular Characterization of Atmospheric Organic Aerosol by Mass Spectrometry

Atmospheric aerosol, particulate matter suspended in the air we breathe, exerts a strong impact on our health and the environment. Controlling the amount of particulate matter in air is difficult, as there are many ways particles can form by both natural and anthropogenic processes. We gain insight into the sources of particulate matter through chemical composition measurements. A substantial portion of atmospheric aerosol is organic, and this organic matter is exceedingly complex on a molecular scale, encompassing hundreds to thousands of individual compounds that distribute between the gas and particle phases. Because of this complexity, no single analytical technique is sufficient. However, mass spectrometry plays a crucial role owing to its combination of high sensitivity and molecular specificity. This review surveys the various ways mass spectrometry is used to characterize atmospheric organic aerosol at a molecular level, tracing these methods from inception to current practice, with emphasis on current and emerging areas of research. Both offline and online approaches are covered, and molecular measurements with them are discussed in the context of identifying sources and elucidating the underlying chemical mechanisms of particle formation. There is an ongoing need to improve existing techniques and develop new ones if we are to further advance our knowledge of how to mitigate the unwanted health and environmental impacts of particles.

Occurrence of persistent organic pollutants in air at different sites in the province of Córdoba, Argentina

The occurrence of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of six sites with different emission sources in the province of Córdoba, Argentina, was analyzed. The sites included urban, industrial, agricultural, and mountain areas. Samples were collected using passive air samplers (PAS) consisting of polyurethane foam disks (PUF). Samples were analyzed for 12 PAHs, 31 polychlorinated biphenyls (PCBs), 12 organochlorine pesticides (OCPs), and 11 polybrominated diphenyl ethers (PBDEs). The concentrations of PAHs in the atmosphere were elevated at urban sites and were even higher at the industrial site. With respect to OCPs, it was observed that the concentrations of endosulfan were greater at the agricultural site (AGR) (416 ± 4 pg m^-3). For hexachlorocyclohexanes (HCHs), only the alpha isomer was detected and there were minimal differences between the different sampling sites (5.9-13.3 pg m^-3). In the case of dieldrin, the highest concentrations (33.6 pg m^-3) were found at the mountain site, which may have been due to its use for insect control. Although heptachlor epoxide was not detected, the concentration of heptachlor was significantly higher at the agricultural and downtown sites (∼ 3.6 pg m^-3). Regarding DDTs, the isomers p,p'-DDT and p,p'-DDE showed the highest concentrations at the mountain site (ΣDDT 120 ± 12 pg m^-3) and downtown site (ΣDDT 157 ± 62 pg m^-3). The relationship between the isomers suggested that at the downtown site, the contribution of this pesticide to the environment was recent, probably for the control of diseases vectors. The congener pattern of PBDEs was dominated by BDE-47, and BDE-99 at all sites, with the downtown site having the highest concentrations of compound esters (ΣPBDEs 118 ± 38 pg m^-3). Finally, high concentrations of PCBs were found at the industrial site (ΣPCBs 1677 ± 134 pg m^-3), and the predominating homologs were 5-Cl and 6-Cl, in contrast to the other sites where PCBs were dominated by 3-Cl and 4-Cl. This is the first study of POPs carried out in the province of Córdoba.

Leaf-deposited semi-volatile organic compounds (SVOCs): An exploratory study using GCxGC-TOFMS on leaf washing solutions

Airborne particulate matter (PM) includes semi-volatile organic compounds (SVOCs), which can be deposited on vegetation matrices such as plant leaves. In alternative to air-point measurements or artificial passive substrates, leaf monitoring offers a cost-effective, time-integrating means of assessing local air quality. In this study, leaf washing solutions from ivy (Hedera hibernica) leaves exposed during one-month at different land use classes were explored via comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS). The composition of leaf-deposited SVOCs, corrected for those of unexposed leaves, was compared against routinely monitored pollutants concentrations (PM₁₀, PM_2.5, O₃, NO₂, SO₂) measured at co-located air monitoring stations. The first study on leaf-deposited SVOCs retrieved from washing solutions, herein reported, delivered a total of 911 detected compounds. While no significant land use (rural, urban, industrial, traffic, mixed) effects were observed, increasing exposure time (from one to 28 days) resulted in a higher number and diversity of SVOCs, suggesting cumulative time-integration to be more relevant than local source variations between sites. After one day, leaf-deposited SVOCs were mainly due to alcohols, N-containing compounds, carboxylic acids, esters and lactones, while ketones, diketones and hydrocarbons compounds gained relevance after one week, and phenol compounds after one month. As leaf-deposited SVOCs became overall more oxidized throughout exposure time, SVOCs transformation or degradation at the leaf surface is suggested to be an important phenomenon. This study confirmed the applicability of GCxGC-TOFMS to analyze SVOCs from leaf washing solutions, further research should include validation of the methodology and comparison with atmospheric organic pollutants.

Seasonal variation, air-water exchange, and multivariate source apportionment of polycyclic aromatic hydrocarbons in the coastal area of Dalian, China

The concentrations and seasonal variations of polycyclic aromatic hydrocarbons (PAHs) in air and seawater dissolved samples from the coastal area of Dalian were investigated, as well as their air-water exchanges. The average concentrations of PAHs were 27.5 ± 14.6 ng/m³ and 49.5 ± 20.5 ng/L in the air and water, respectively. Phenanthrene was the dominant congener in both air and water dissolved phase. Seasonality was discovered in the air with the concentrations higher in winter than in summer, but not in the water dissolved phase. Air-water exchange trends also displayed apparent seasonality with 3-4 ring PAHs generally being volatilization or equilibrium in summer but deposition in winter, which highlighted the important influence of temperature on the air-water exchange direction of PAHs. The air-water exchange fluxes of individual PAH congeners ranged from -24331 to 6541 ng/m²/d, and the highest deposition and volatilization fluxes both appeared at the industrial areas, which emphasized the influence of point source emission to the magnitude of air-water diffusion flux of PAHs. Multivariate source apportionment approaches, including principle component analysis, diagnostic ratios, and positive matrix factorization, were conducted, which suggested that PAHs in water originated from multiple sources. Frequent port transport correlated vehicle/ship emission rather than coal combustion may be the primary contributor of PAHs to the coastal air and water.

Passive indoor air sampling for consumer product chemicals: a field evaluation study

Innovative exposure measurement methods are needed for large environmental health studies, particularly for semivolatile organic compounds (SVOCs). Active air sampling methods are costly to implement, but passive air sampling presents a viable method. To expand and improve the use of passive air samplers (PAS) for indoor SVOC monitoring, we designed a unique, compact sampler using commercially available polyurethane foam (PUF) disks housed within durable, easy-to-setup, low-profile enclosures. We evaluated the new design using co-located active air samplers (AAS) and analyzed for SVOCs. Most of the targeted SVOCs found using active sampling (27 of 33) were also detected using passive sampling. We found good agreement (R² = 0.88) between active and passive sampling methods for characterizing the relative abundance of each chemical, and the measured active sampler concentrations and passive sampler masses were significantly positively correlated for 14 of 21 chemicals, for which correlations could be estimated. We found that measurements of many SVOCs originating from consumer products and typically found in the gas-phase (log K_OA < 10) can be reliably ranked-and thus appropriate for epidemiological studies-using this PAS design. These SVOCs include diethyl phthalate, AHTN, HHCB, tris(2-chloroethyl) phosphate, dibutyl phthalate, and tris(1-chloro-2-propyl) phosphate, as well as methyl paraben, benzophenone, and benzophenone-3, which have not previously been measured by passive sampling. This PAS can be used in epidemiological studies involving consumer product chemicals and complements other novel exposure tools.