Identification of PM sources by principal component analysis (PCA) coupled with wind direction data

The effectiveness of combining principal component analysis (PCA) with multi-linear regression (MLRA) and wind direction data was demonstrated in this study. PM data from three grain-size fractions from a highly industrialised area in Northern Spain were analysed. Seven independent PM sources were identified by PCA: steel (Pb, Zn, Cd, Mn) and pigment (Cr, Mo, Ni) manufacture, road dust (Fe, Ba, Cd), traffic exhaust (P, OC + EC), regional-scale transport (, , V), crustal contributions (Al2O3, Sr, K) and sea spray (Na, Cl). The spatial distribution of the sources was obtained by coupling PCA with wind direction data, which helped identify regional drainage flows as the main source of crustal material. The same analysis showed that the contribution of motorway traffic to PM10 levels is 4-5 microg m-3 higher than that of local traffic. The coupling of PCA-MLRA with wind direction data proved thus to be useful in extracting further information on source contributions and locations. Correct identification and characterisation of PM sources is essential for the design and application of effective abatement strategies.     

Enrichment of polycyclic aromatic hydrocarbons (PAHs) in mariculture sediments of Hong Kong

Surface and core sediments collected from six fish farms in Hong Kong and from reference sites were investigated for the enrichment and sources of polycyclic aromatic hydrocarbons (PAHs). Moderately high ∑PAH₁₆ levels (123-947 ng g⁻¹, mean: 450 ng g⁻¹) were found in the surface aquaculture sediments. In comparison with the sediments from the reference sites, the average enrichment percentage of total organic carbon (TOC) and PAHs in surface sediments were 21.4 and 43.8%, respectively, and in the core sediments, 24.6 and 73.7%, respectively. Mathematical source apportionment analyses (i.e. isomer ratios, hierarchical cluster analysis, principal components analysis with multiple linear regression analysis) suggested a higher percentage of petrogenic sources in aquaculture sediments. The fish feeds might be the main source of the enriched PAHs in the aquaculture sediments. To our knowledge, this is the first study showing that PAHs in aquaculture sediments could be attributed to human aquaculture activities.     

Source apportionment of the carcinogenic potential of polycyclic aromatic hydrocarbons (PAH) associated to airborne PM10 by a PMF model

In order to perform a study of the carcinogenic potential of polycyclic aromatic hydrocarbons (PAH), benzo(a)pyrene equivalent (BaP-eq) concentration was calculated and modelled by a receptor model based on positive matrix factorization (PMF). Nineteen PAH associated to airborne PM10 of Zaragoza, Spain, were quantified during the sampling period 2001–2009 and used as potential variables by the PMF model. Afterwards, multiple linear regression analysis was used to quantify the potential sources of BaP-eq. Five sources were obtained as the optimal solution and vehicular emission was identified as the main carcinogenic source (35 %) followed by heavy-duty vehicles (28 %), light-oil combustion (18 %), natural gas (10 %) and coal combustion (9 %). Two of the most prevailing directions contributing to this carcinogenic character were the NE and N directions associated with a highway, industrial parks and a paper factory. The lifetime lung cancer risk exceeded the unit risk of 8.7?×?10^?5 per ng/m³ BaP in both winter and autumn seasons and the most contributing source was the vehicular emission factor becoming an important issue in control strategies.     

Source apportionment of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Palm Beach County,Florida

Due to concerns about adverse health effects associated with inhalation of atmospheric polycyclic aromatic hydrocarbons (PAHs), 30 ambient air samples were obtained at an air quality monitoring station in Palm Beach County, Florida, from March 2013 to March 2014. The ambient PAH concentration measurements and fractional emission rates of known sources were incorporated into a chemical mass balance model, CMB8.2, developed by EPA, to apportion contributions of three major PAH sources including preharvest sugarcane burning, mobile vehicles, and wildland fires. Strong association between the number of benzene rings and source contribution was found, and mobile vehicles were identified to be the prevailing source (contribution ≥56%) for the observed PAHs concentration with lower molecular weights (four or fewer benzene rings) throughout the year. Preharvest sugarcane burning was the primary contributing source for PAHs with relatively higher molecular weights (five or more benzene rings) during the sugarcane burning season (from October to May of the next year). Source contribution of wildland fires varied among PAH compounds but was consistently lower than for sugarcane burning during the sugarcane harvest season. Determining the major sources responsible for ground-level PAHs serves as a tool to improving management strategies for PAH emitting sources and a step toward better protection of the health of residents in terms of exposure to PAHs. The results obtain insight into temporal dominance of PAH polluting sources for those residential areas located near sugarcane burning facilities and have implications beyond Palm Beach County, in areas with high concerns of PAHs and their linked sources.

Implications: Source apportionment of atmospheric polycyclic hydrocarbons (PAHs) in Palm Beach County, Florida, meant to estimate contributions of major sources in PAH concentrations measured at Belle Glade City of Palm Beach County. Number of benzene rings was found to be the key parameter in determining the source with the prevailing contribution. Mobile vehicle sources showed a higher contribution for species with four or fewer benzene rings, whereas sugarcane burning contributed more for species with five or more benzene rings. Results from this study encourage more control for sugarcane burns and help to better manage authorization of the sugarcane burning incidents and more restrictive transportation plans to limit PAH emissions from mobile vehicles.     

Polycyclic aromatic hydrocarbons (PAHs) and carbonyl compounds in urban atmosphere of Hong Kong

Polycyclic aromatic hydrocarbons (PAHs) and carbonyls compounds are becoming a major component of atmospheric toxic air pollutants (TAPs) in Hong Kong. Many studies in Hong Kong show that traffic emission is one of the most significant contributors in urban area of Hong Kong. A twelve months monitoring program for PAHs and carbonyl compounds started on 10 April 1999 including a two weeks intensive sampling in winter had been performed at a roadside urban station at Hong Kong Polytechnic University in order to determine the monthly and seasonal variations of PAHs and carbonyl concentrations. The objective of this study is to characterize the roadside concentrations of selected TAPs (PAHs and carbonyl compounds) and to compare with the long-term compliance monitoring data acquired by Hong Kong Environmental Protection Department (EPD). Monthly variations, seasonal variations and winter/summer ratios at the monitoring station are discussed.     

Use of high-resolution MM5/CALMET/CALPUFF system: SO2 apportionment to air quality in Hong Kong

Recent research has highlighted the substantial health-related costs of air pollution in the Hong Kong Special Administrative Region (HKSAR) and the potential threat from air pollution to HKSARs economic competitiveness. In order to address the air pollution problems, this paper seeks to analyse the individual contributions of major sulphur dioxide (SO₂) sources in the Pearl River Delta Region (PRDR) (Pearl River Delta + HKSAR) on the air quality in the HKSAR. This study employed the coupling of the MM5/CALMET system with the CALPUFF, the multi-layer, non-steady-state puff dispersion model, where major power plants, marine vessels and vehicles, all in the PRDR, are taken into account. The observation data and simulation results at 11 Hong Kong Environmental Protection Department (HKEPD) general (non-road-side) stations are analyzed. Urban (in-zone) and Rural (out-zone) stations are defined in order to examine the SO₂ contribution of different emission sources in different regions of the HKSAR. The model results show that the contribution of the HKSAR marine sources is significant both in summer and in winter, especially for the locations around the in-zone stations (in general 60%, and 55% in summer and winter respectively). In addition, the contribution of the HKSAR power plants is slightly higher than that of the PRD power plants in early summer, with a contribution difference of up to 20% when the prevailing wind is from the south. However, in late summer, this situation reverses. In winter, the contribution of the PRD power plants is two to three times greater than that of the HKSAR power plants. Moreover, Yantian port affects the northern part of the HKSAR when a northeasterly wind dominates the HKSAR. In order to solve these air pollution problems, the main implication of these results suggests that the HKSAR government, in close co-operation with the Guangdong government, needs to take immediate action.     

Exploratory studies of PM10 receptor and source profiling by GC/MS and principal component analysis of temporally and spatially resolved ambient samples

For a recent exploratory study of particulate matter (PM) compositions, origins, and impacts in the El Paso/Juarez (Paso del Norte) airshed, the authors relied on solvent extraction (SX)-gas chromatography/mass spectrometry (GC/MS) procedures to characterize 24-hr quartz fiber (QF) filter samples obtained from nine spatially distributed high-volume (Hi-Vol) PM10 samplers as well as on thermal desorption (TD)-GC/MS methods to characterize 45 time-resolved (2-hr) filter samples obtained with modified 1-m3/hr PM10 samplers. Principal component analysis and related chemometric techniques were used for data reduction and data fusion as well as for multiway data correlation. A high degree of correspondence (R2 = 0.821) was found between the rapid TD-GC/MS method (which can be carried out on 2-hr filter slices containing only microgram amounts of sample) and conventional SX-GC/MS procedures. The four main source patterns of organic PM components observed in GC/MS profiles of both temporally and spatially resolved receptor samples obtained in the El Paso/Juarez border airshed during the study period are interpreted to represent (1) vehicular emissions plus resuspended urban dust; (2) biomass combustion; (3) native vegetation detritus and resuspended agricultural dust; and (4) waste burning. Moreover, principal component analysis of combined, variance-weighted, temporally resolved TD-GC/MS data and spatially resolved SX-GC/MS data was used to determine approximate source locations for specific PM components identified in time-resolved receptor sample profiles. The same approach can be used to determine approximate circadian concentration profiles of specific PM components identified in spatially resolved receptor sample profiles.     

Source apportionment of PM2.5 and PM10 aerosols in Brisbane (Australia) by receptor modelling

Aerosol samples for PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameters less than 2.5 and 10 μm, respectively) were collected from 1993 to 1995 at five sites in Brisbane, a subtropical coastal city in Australia. This paper investigates the contributions of emission sources to PM_2.5 and PM₁₀ aerosol mass in Brisbane. Source apportionment results derived from the chemical mass balance (CMB), target transformation factor analysis (TTFA) and multiple linear regression (MLR) methods agree well with each other. The contributions from emission sources exhibit large variations in particle size with temporal and spatial differences. On average, the major contributors of PM₁₀ aerosol mass in Brisbane include: soil/road side dusts (25% by mass), motor vehicle exhausts (13%, not including the secondary products), sea salt (12%), Ca-rich and Ti-rich compounds (11%, from cement works and mineral processing industries), biomass burning (7%), and elemental carbon and secondary products contribute to around 15% of the aerosol mass on average. The major sources of PM_2.5 aerosols at the Griffith University (GU) site (a suburban site surrounded by forest area) are: elemental carbon (24% by mass), secondary organics (21%), biomass burning (15%) and secondary sulphate (14%). Most of the secondary products are related to motor vehicle exhausts, so, although motor vehicle exhausts contribute directly to only 6% of the PM_2.5 aerosol mass, their total contribution (including their secondary products) could be substantial. This pattern of source contribution is similar to the results for Rozelle (Sydney) among the major Australian studies, and is less in contributions from industrial and motor vehicular exhausts than the other cities. An attempt was made to estimate the contribution of rural dust and road side dust. The results show that road side dusts could contribute more than half of the crustal matter. More than 80% of the contribution of vehicle exhausts arises from diesel-fuelled trucks/buses. Biomass burning, large contributions of crustal matter, and/or local contributing sources under calm weather conditions, are often the cause of the high PM₁₀ episodes at the GU site in Brisbane.     

Use of principal components analysis (PCA) on estuarine sediment datasets: The effect of data pre-treatment

Principal components analysis (PCA) is a multivariate statistical technique capable of discerning patterns in large environmental datasets. Although widely used, there is disparity in the literature with respect to data pre-treatment prior to PCA. This research examines the influence of commonly reported data pre-treatment methods on PCA outputs, and hence data interpretation, using a typical environmental dataset comprising sediment geochemical data from an estuary in SE England. This study demonstrated that applying the routinely used log (x + 1) transformation skewed the data and masked important trends. Removing outlying samples and correcting for the influence of grain size had the most significant effect on PCA outputs and data interpretation. Reducing the influence of grain size using granulometric normalisation meant that other factors affecting metal variability, including mineralogy, anthropogenic sources and distance along the salinity transect could be identified and interpreted more clearly.     

Emissions of gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) in the Shing Mun Tunnel,Hong Kong

Real-world vehicle emission factors for seventeen gas and particulate polycyclic aromatic hydrocarbons (PAHs) were quantified in the Shing Mun Tunnel, Hong Kong during summer and winter 2003. Naphthalene, acenaphthylene, and acenaphthene were the most abundant gas PAHs while fluoranthene and pyrene were the most abundant in the particle phase. Most (98%) of the gas PAHs consisted of two- and three-aromatic rings whereas most of the particle-phase PAHs were in four- (～60%) and five-ring (～17%) for fresh exhaust emissions. Average emission factors for the gas- and particle PAHs were 950–2564 μg veh^?1 km^?1 and 22–354 μg veh^?1 km^?1, respectively. Good correlations were found between diesel markers (fluoranthene and pyrene; 0.85) and gasoline markers (benzo[ghi]perylene and indeno[1,2,3-cd]pyrene; 0.96). Higher PAH emission factors were associated with a higher fraction of diesel-fueled vehicles (DV) passing through the tunnel. Separate emission factors were determined from diesel and non-diesel exhaust by the regression intercept method. The average PAH emission factor (i.e., sum of gas and particle phases) from DV (3085 ± 1058 μg veh^?1 km^?1) was ～5 times higher than that from non-diesel-fueled vehicles (NDV, 566 ± 428 μg veh^?1 km^?1). Ratios of DV to NDV emission factors were high for diesel markers (>24); and low for gasoline markers (<0.4).     

Abundance and sources of ambient dioxins in Hong Kong: a review of dioxin measurements from 1997 to 2001

Ambient measurements of seventeen 2,3,7,8-polychlorinated dibenzo-p-dioxin/dibenzofuran congeners (2,3,7,8-PCDD/Fs) have been taken in a number of monitoring programs or ad-hoc studies in Hong Kong. The longest monitoring program started at two locations in the territory in July 1997. The other monitoring efforts are ad-hoc studies, varying from a few coordinated sampling events at multiple sites to a year-long monitoring project that targeted suspected local dioxin sources. In this paper, we examined these measurements to understand the ambient levels, temporal and spatial variation, and possible sources of the 2,3,7,8-PCDD/Fs in Hong Kong. The territory-wide annual average concentration of the dioxins was 0.052 pg I-TEQ/m3 measured at the regular monitoring stations in the most recent annual cycle of 2000/2001. This level fell at the lower end of the range of dioxin concentrations measured at other urban locations around the world. The dioxin levels showed a clear seasonality in that elevated concentrations were observed in the winter and lower concentrations in the summer at all monitoring sites with one year or more regular measurements. The measurements indicated that the few known local dioxin sources, including a major chemical waste incinerator facility, landfill sites, and vehicular traffic, are not important contributors to ambient dioxins in Hong Kong. On days of high dioxin concentrations, the 2,3,7,8-PCDD/F congeners were observed to have almost identical compositions with a north-northwest to south-southeast spatial gradient in concentrations at different sampling locations in Hong Kong. This observation, along with other collaborative evidence, established a strong link between high dioxin concentration days in Hong Kong and regional transport of the polluted air masses from the north.     

基于主成分分析法的辽河水体中溶解性金属来源分析

在测定辽河水体中几种主要的溶解性金属(包括7种重金属)的含量和分析其空间分布特征的基础上,运用主成分分析(PCA)法分析了金属的可能来源。结果表明,辽河水体中溶解性金属的平均浓度为Al>Cu>Zn>Cr>Hg>As>Pb>Cd,与欧美发达国家的主要水体相比,辽河水体的金属污染状况总体较重;辽河水体中溶解性金属的污染来源主要分两类:农业面源和工业废水污染源,工业综合污染源;根据主成分得分系数可知,采样点2(通江口)、3(三合屯)、7(朱尔山)的金属污染主要来源于农业面源和工业废水污染源;采样点6(药王庙)的金属污染主要来源于工业综合污染源;基于PCA法的金属来源分析对辽河流域水体金属污染治理对策的制定有着重要的指导意义。     

Source apportionment of particulate matter (PM2.5) in an urban area using dispersion,receptor and inverse modelling

Air pollution emission inventories are the basis for air quality assessment and management strategies. The quality of the inventories is of great importance since these data are essential for air pollution impact assessments using dispersion models. In this study, the quality of the emission inventory for fine particulates (PM_2.5) is assessed: first, using the calculated source contributions from a receptor model; second, using source apportionment from a dispersion model; and third, by applying a simple inverse modelling technique which utilises multiple linear regression of the dispersion model source contributions together with the observed PM_2.5 concentrations. For the receptor modelling the chemical composition of PM_2.5 filter samples from a measurement campaign performed between January 2004 and April 2005 are analysed. Positive matrix factorisation is applied as the receptor model to detect and quantify the various source contributions. For the same observational period and site, dispersion model calculations using the Air Quality Management system, AirQUIS, are performed. The results identify significant differences between the dispersion and receptor model source apportionment, particularly for wood burning and traffic induced suspension. For wood burning the receptor model calculations are lower, by a factor of 0.54, but for the traffic induced suspension they are higher, by a factor of 7.1. Inverse modelling, based on regression of the dispersion model source contributions and the PM_2.5 concentrations, indicates similar discrepancies in the emissions inventory. In order to assess if the differences found at the one site are generally applicable throughout Oslo, the individual source category emissions are rescaled according to the receptor modelling results. These adjusted PM_2.5 concentrations are compared with measurements at four independent stations to evaluate the updated inventory. Statistical analysis shows improvement in the estimated concentrations for PM_2.5 at all sites. Similarly, inverse modelling is applied at these independent sites and this confirms the validity of the receptor model results.     

Source apportionment of particulate matter in a large city of southeastern Po Valley (Bologna, Italy)

This study reports the results of an experimental research project carried out in Bologna, a midsize town in central Po valley, with the aim at characterizing local aerosol chemistry and tracking the main source emissions of airborne particulate matter. Chemical speciation based upon ions, trace elements, and carbonaceous matter is discussed on the basis of seasonal variation and enrichment factors. For the first time, source apportionment was achieved at this location using two widely used receptor models (principal component analysis/multi-linear regression analysis (PCA/MLRA) and positive matrix factorization (PMF)). Four main aerosol sources were identified by PCA/MLRA and interpreted as: resuspended particulate and a pseudo-marine factor (winter street management), both related to the coarse fraction, plus mixed combustions and secondary aerosol largely associated to traffic and long-lived species typical of the fine fraction. The PMF model resolved six main aerosol sources, interpreted as: mineral dust, road dust, traffic, secondary aerosol, biomass burning and again a pseudo-marine factor. Source apportionment results from both models are in good agreement providing a 30 and a 33 % by weight respectively for PCA-MLRA and PMF for the coarse fraction and 70 % (PCA-MLRA) and 67 % (PMF) for the fine fraction. The episodic influence of Saharan dust transport on PM₁₀ exceedances in Bologna was identified and discussed in term of meteorological framework, composition, and quantitative contribution.     

Measurements of non-methane hydrocarbons, DOC in surface ocean waters and aerosols over the Nordic seas during polarstern cruise ARK-XX/1 (2004)

To explore processes leading to the formation of volatile organic compounds at the sea surface and their transfer to the atmosphere, whole air, marine aerosols, and surface ocean water DOC were simultaneously sampled during June-July 2004 on the Nordic seas. 19 C(2)-C(6) non-methane hydrocarbons (NMHCs) in the air samples are reported from nine sites, spanning a range of latitudes. Site-to-site variability in NMHC concentrations was high, which suggests variable, local sources for these compounds studied. Total DOC in surface waters sampled ranged from 0.84 mg l(-1) (Fram Strait) to 1.06 mg l(-1) (East Greenland Current), and decreased 6-8% with 24h UV-A irradiation. Pentanes and hexanes, as well as acetone and dimethylsulfide, were identified in the seawater samples using solid-phase microextraction/GC-MS. All these compounds are volatile enough that exchange with the atmosphere can be expected, and the detection of the hydrocarbons in particular is consistent with a marine source for these in the air samples. Size-fractionated aerosols from the same sampling regions were analysed by SEM-EDX and contained sea salt, marine sulfates, and carbonates. A culturable bacterium was isolated from the large (9.9-18 microm) fraction at one site, and identified by 16S rRNA PCR analysis as Micrococcus luteus, raising the possibility that marine bioaerosols could transfer marine organic carbon to the aerosol phase and thus influence formation of VOCs above the remote oceans.     

Polychlorinated biphenyls (PCBs) in sediments in Hong Kong: a congener-specific approach to the study of coplanar PCBs in aquatic ecosystems

Patterns of contamination by polychlorinated biphenyls (PCBs) were investigated in fourteen samples of coastal sediments from Hong Kong. Congener-specific analyses revealed nine sediment samples from Junk Bay to contain PCBs at concentrations ranging from 31 to 2200 ng g(-1) dry weight, concentrations generally increasing with distance north in the Bay. By contrast, five sediments from the Tolo area to the north-east of Hong Kong exhibited total PCB levels of only 6.6 to 45 ng g(-) dry weight. The patterns of relative abundance of PCB congeners in the northern Junk Bay sediments suggested the existence of ongoing source(s) of PCBs in this area; biphenyls of lower chlorination were present at high concentration in these samples. Three coplanar PCBs (3', 4, 4'-tetrachlorobiphenyl; 3,3',4,4',5-pentachlorobiphenyl; and 3,3',4,4',5,5'-hexachlorobiphenyl) were found to be present in Junk Bay sediments; these are highly toxic and are cause for concern in aquatic environments. The abundance of the three coplanar PCBs in the sediments studied was similar to that in commercial PCB mixtures, suggesting that these congeners are not enriched over other PCBs by the sediments of coastal ecosystems. It is concluded that the preferential enrichment of coplanar PCBs occurs in the biosphere, rather than in sediments.     

A comparison of mussels (Perna viridis) and semi-permeable membrane devices (SPMDs) for monitoring chlorinated trace organic contaminants in Hong Kong coastal waters

A comparison of mussels (Perna viridis) and semi-permeable membrane devices (SPMDs) was carried out at five sites, representing a gradient of contaminant concentrations, in Hong Kong coastal waters. Mussels, originally collected from a “clean” location, were deployed along with SPMDs at each site for 30 days. Analyses for chlorinated pesticides and polychlorinated biphenyls (PCBs) indicated that SPMDs have potential as monitoring tools, and to some extent can overcome the problems associated with mussels, such as natural variability, differing age, sex, and physical condition. However, in most cases, SPMDs failed to rank the sites in the same order as mussels in terms of contaminant concentrations. Nonetheless, in localities where mussels cannot survive – as shown at Kwun Tong in the present experiment – SPMDs may be valuable in providing an indication of potentially bio-available lipophilic pollutants.     

Mussels as bioindicators of PCB pollution: a case study on uptake and release of PCB isomers and congeners in green-lipped mussels (Perna viridis) in Hong Kong waters

The uptake and release of PCB isomers and congeners were examined in green-lipped mussels (Perna viridis) through a transplantation experiment in two locations in Hong Kong waters. Rapid rates of uptake and release of relatively less lipophilic lower-chlorinated PCBs were observed in the mussels, indicating that the primary mechanism of bioaccumulation of lipophilic pollutants in P. viridis complies with the concept of equilibrium partitioning. Thus, data for contaminant concentrations are most appropriately based upon lipid weights of samples when using mussels as bioindicators of aquatic PCB pollution. Considering the kinetic parameters of PCBs based on lipid weight-related data, it is concluded that P. viridis has the ability to respond rapidly to changes in ambient levels of PCBs. This is significant in determining the usefulness and limitations of mussels as bioindicators for monitoring programmes investigating aquatic pollution by PCBs.     

Quantitative trace analysis of polyfluorinated alkyl substances (PFAS) in ambient air samples from Mace Head (Ireland): A method intercomparison

A method intercomparison study of analytical methods for the determination of neutral, volatile polyfluorinated alkyl substances (PFAS) was carried out in March, 2006. Environmental air samples were collected in triplicate at the European background site Mace Head on the west coast of Ireland, a site dominated by ‘clean’ westerly winds coming across the Atlantic. Extraction and analysis were performed at two laboratories active in PFAS research using their in-house methods. Airborne polyfluorinated telomer alcohols (FTOHs), fluorooctane sulfonamides and sulfonamidoethanols (FOSAs/FOSEs) as well as additional polyfluorinated compounds were investigated. Different native and isotope-labelled internal standards (IS) were applied at various steps in the analytical procedure to evaluate the different quantification strategies. Field blanks revealed no major blank problems. European background concentrations observed at Mace Head were found to be in a similar range to Arctic data reported in the literature. Due to trace-levels at the remote site, only FTOH data sets were complete and could therefore be compared between the laboratories. Additionally, FOSEs could partly be included. Data comparison revealed that despite the challenges inherent in analysis of airborne PFAS and the low concentrations, all methods applied in this study obtained similar results. However, application of isotope-labelled IS early in the analytical procedure leads to more precise results and is therefore recommended.