Identification of organic chemical indicators for tracking pollution sources in groundwater by machine learning from GC-HRMS-based suspect and non-target screening data.

In this study, the strong analytical power of gas chromatography coupled to a high resolution mass spectrometry (GC-HRMS) in suspect and non-target screening (SNTS) of organic micropollutants was combined with machine learning tools for proposing a novel and robust systematic environmental forensics workflow, focusing on groundwater contamination. Groundwater samples were collected from four different regions with diverse contamination histories (namely oil [OC], agricultural [AGR], industrial [IND], and landfill [LF]), and a total of 252 organic micropollutants were identified, including pharmaceuticals, personal care products, pesticides, polycyclic aromatic hydrocarbons, plasticizers, phenols, organophosphate flame retardants, transformation products, and others, with detection frequencies ranging from 3 % to 100 %. Amongst the SNTS identified compounds, a total of 51 chemical indicators (i.e., OC: 13, LF: 12, AGR: 19, IND: 7) which included level 1 and 2 SNTS identified chemicals were pinpointed across all sampling regions by integrating a bootstrapped feature selection method involving the bootfs algorithm and a partial least squares discriminant analysis (PLS-DA) model to determine potential prevalent contamination sources. The proposed workflow showed good predictive ability (Q2) of 0.897, and the suggested contamination sources were gasoline, diesel, and/or other light petroleum products for the OC region, anthropogenic activities for the LF region, agricultural and human activities for the AGR region, and industrial/human activities for the IND region. These results suggest that the proposed workflow can select a subset of the most diagnostic features in the chemical space that can best distinguish a specific contamination source class.

Human exposure to short-chain chlorinated paraffins and organophosphate flame retardants in relation to paired multiple sources.

In this study, the levels and distributions of short chain chlorinated paraffins (SCCPs) and organophosphate flame retardants (OPFRs) were determined in 10-88 aged human serum/hair and their paired multiple exposure sources, including one-day composite food, drinking water, and house dust. The average concentration of SCCPs and OPFRs were respectively 6313 and 176 ng/g lipid weight (lw) in serum, 1008 and 108 ng/g dry weight (dw) in hair, 1131 and 27.2 ng/g dw in food, not detected and 45.1 ng/L in drinking water, and 2405 and 864 ng/g in house dust. The levels of SCCPs in serum of adults were significantly higher than those of juvenile (Mann-Whitney U test, p < 0.05), whereas gender showed no statistically significant difference in SCCPs and OPFRs levels. In addition, there were significant relationships of OPFR concentrations between serum and drinking water as well as hair and food using the multiple linear regression analysis, whereas no correlation was observed for SCCPs. Based on the estimated daily intake, the major exposure pathway for SCCPs was food, while for OPFRs, it was food and drinking water with three order magnitude safety margin.

Exposure and Risk Assessment of Korean Firefighters to PBDEs and PAHs via Fire Vehicle Dust and Personal Protective Equipment.

In this study, the levels of polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs) were characterized in firefighters' personal protective equipment (PPE) (i.e., jackets, pants, hoods, and gloves) and vehicle dust wipe samples to assess the exposure and potential risk of firefighters to these combustion-related toxic pollutants. The mean levels of ∑PBDEs in the fire vehicle dust samples (778 and 449 pg/cm2 for pump trucks and command cars, respectively) were significantly higher than those in the private vehicles (31.2 pg/cm2) (Kruskal-Wallis test, p < 0.05), which was similar to the ∑PAH levels (521, 185, and 46.8 pg/cm2 for pump trucks, command cars, and private vehicles, respectively). In the case of firefighters' PPE, the levels of ∑PBDEs and ∑PAHs in used jackets and pants were found to be, respectively, 70- to 2242-folds and 11- to 265-folds higher than those in their unused counterparts. Biomass/petroleum combustion was found to be the main source of PAH contamination in fire vehicle dust and used PPE in the present study. Both carcinogenic and noncarcinogenic risks via vehicle dust ingestion and dermal absorption from wearing of PPE were within permissible limits, although the relative risk evaluation showed that PAH/PBDE absorption via wearing of PPE could pose a higher likelihood of carcinogenic and noncarcinogenic risks than the ingestion of pollutants via fire vehicle dust, warranting the need for appropriate management of firefighters' personal protective ensembles.

Long-term degradation of toluene and phenol in soil: Identification of transformation products and pathways via HRMS-based suspect and non-target screening.

In this study, the long-term fate of toluene and phenol in the soil was investigated, and the transformation products (TPs) and pathways of these compounds were studied by a high resolution mass spectrometry (HRMS)-based suspect and non-target screening approach for the first time, and 9 and 12 transformation products were identified for toluene and phenol, respectively in the lab-exposed soil samples. Salicylaldehyde, 4-hydroxybenzaldehyde, and benzaldehyde were identified in toluene-contaminated field soil samples for the first time, and the main mechanisms involved in the biodegradation and detoxification of toluene and phenol in soil were oxidation, carboxylation, dehydroxylation, and ring fission amongst others. 2-oxoglutarate, TP165-A, TP165-B, TP172, and TP195 were identified as novel phenol transformation products, while salicylaldehyde, 2-oxoglutarate, TP165-A, and TP165-B were identified as novel toluene transformation products, providing new possible evidence for additional degradation pathways, which could give new insights into the fate of toluene and phenol during the natural attenuation process in the environment. Finally, salicylaldehyde, 4-OH-benzaldehyde, and 4-OH-benzoic acid which were detected at Level 1 identification confidence were suggested as indicator chemicals of toluene and phenol exposure in the contaminated field.

Temporal and spatial trends of chlorinated paraffins and organophosphate flame retardants in black-tailed gull (Larus crassirostris) eggs.

In this study, eggs of black-tailed gull (Larus crassirostris), a top trophic level predator of marine ecosystem were, for the first time, monitored to assess the temporal and spatial trends of emerging pollutants in South Korea. Two Island regions, namely, Baekryeong-do (Site A) and Hong-do (Site B) were investigated from 2012 to 2018, and the total levels of short chain chlorinated paraffins (SCCPs), medium chain CPs (MCCPs), and organophosphate flame retardants (OPFRs) for both Site A and B were 1180-2931 and 694-2023 ng/g lipid weight (lw), 1287-4898 and 1034-3075 ng/g lw, and 203-499 and 233-409 ng/g lw, respectively. The time-trends of the concentration of pollutants showed an increasing tendency from 2012 to 2018, with the levels predicted to be doubled within three years, following the results of regression analysis. A shift in temporal-trends from shorter to longer chain CPs was noted, suggesting the effect of industrial-related contamination. Especially, significantly high levels of CPs and OPFRs were found in the site adjacent to China, which is reasonable as China is the largest producer and consumer of FRs and plasticizers worldwide. This study is valuable to understand the temporal increment of emerging pollutants as the alternatives of phased-out FRs and plasticizers, while raising the need for continuous environmental management.

Assessment of Exposure of Korean Firefighters to Polybrominated Diphenyl Ethers and Polycyclic Aromatic Hydrocarbons via Their Measurement in Serum and Polycyclic Aromatic Hydrocarbon Metabolites in Urine.

This study investigated the occupational exposure of Korean firefighters to a suite of combustion-related pollutants. Exposure to polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) was assessed by measurement of their levels in serum and metabolites in urine (i.e., monohydroxylated PAHs, OH-PAHs). The mean level of ∑PBDEs in the serum of firefighters (17.1 ng/g lipid weight (lw)) was significantly higher than that of the general population (1.39 ng/g lw) (Mann-Whitney U Test, p < 0.05), which is similar to the ∑PAH levels (1286 ng/g lw for firefighters and 1016 ng/g lw for the general population). Individual OH-PAH levels showed 2.1- to 4.2-fold increases in postfire urine samples compared to the control urine samples, with the mean ∑OH-PAHs being significantly higher in postfire urine samples (22,658 ng/g creatinine) than in the control urine samples (10,253 ng/g creatinine) (Mann-Whitney U test, p < 0.05). It was found that ∑PBDEs correlated with firefighters' length of service and years dedicated to on-site dispatch, while ∑OH-PAHs was strongly associated with firefighters' exposure duration, age, length of service, and years dedicated to on-site dispatch. Indeed, the results of the present study indicate that Korean firefighters are prone to elevated risk of exposure to toxic combustion-related pollutants compared with the general population.

Organophosphate Flame Retardants and Perfluoroalkyl Substances in Drinking Water Treatment Plants from Korea: Occurrence and Human Exposure.

In this study, the concentrations of organophosphate flame retardants (OPFR) and perfluoroalkyl substances (PFAS) were investigated in raw water and treated water samples obtained from 18 drinking water treatment plants (DWTPs). The ∑13OPFR concentrations in the treated water samples (29.5-122 ng/L; median 47.5 ng/L) were lower than those in the raw water (37.7-231 ng/L; median 98.1 ng/L), which indicated the positive removal rates (0-80%) of ∑13OPFR in the DWTPs. The removal efficiencies of ∑27PFAS in the DWTPs ranged from -200% to 50%, with the ∑27PFAS concentrations in the raw water (4.15-154 ng/L; median 32.0 ng/L) being similar to or lower than those in the treated water (4.74-116 ng/L; median 42.2 ng/L). Among OPFR, tris(chloroisopropyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP) were dominant in both raw water and treated water samples obtained from the DWTPs. The dominant PFAS (perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA)) in the raw water samples were slightly different from those in the treated water samples (PFOA, L-perfluorohexane sulfonate (L-PFHxS), and PFHxA). The 95-percentile daily intakes of ∑13OPFR and ∑27PFAS via drinking water consumption were estimated to be up to 4.9 ng/kg/d and 0.22 ng/kg/d, respectively. The hazard index values of OPFR and PFAS were lower than 1, suggesting the risks less than known hazardous levels.

Seasonal occurrence and removal of organophosphate esters in conventional and advanced drinking water treatment plants.

In this study, the fate of organophosphate esters (OPEs) in conventional and advanced drinking water treatment plants (DWTPs) was investigated in field scale. In addition, the risk of OPEs by drinking water was assessed. The average total OPE concentrations in raw and treated water were lower in the rainy season (94.3 and 57.1 ng/L, respectively) than dry season (163 and 84.2 ng/L, respectively). Advanced DWTPs showed better removal efficiencies of major OPEs rather than those in conventional DWTPs. The average removal rates for two chlorinated OPEs, including tris(2-chloroethyl)phosphate (TCEP) and tris(1-chloro-2-propyl)phosphate (TCIPP), were negative (TCEP: -87%, TCIPP: -41%) for a conventional DWTP but positive (TCEP: 46%, TCIPP: 49%) for advanced DWTPs using granular activated carbon filtration. The average removal rates for advanced DWTPs were statistically higher for the alkyl/aryl OPEs, tri-n-butyl phosphate (TNBP: 67%) and tris(2-butoxyethyl) phosphate (TBOEP: 63%), than those for the conventional DWTPs (TNBP: 21%, TBOEP: 25%). The hazardous quotient (HQ) of major OPEs were lower for advanced DWTPs and water irrigated from upstream sties/reservoir compared to that of conventional DWTPs and water irrigated from downstream sites. We believe that this is the first comparison of OPE removal efficiencies achieved in conventional and advanced DWTPs.

Short-chain chlorinated paraffins in various foods from Republic of Korea: Levels, congener patterns, and human dietary exposure.

Short-chain chlorinated paraffin (SCCP) concentrations in 419 food samples (from 59 species) from Republic of Korea were determined. The SCCP concentrations and lipid contents in whole foods positively correlated and the highest SCCP concentration (891 ng/g wet weight) was observed in fats and oils. The SCCP concentrations were higher in benthic fish/shellfish and demersal fish than other fish and shellfish. The SCCP concentrations were higher in duck meat and eggs than meat and eggs of other species. The chlorine-based congener group patterns were related to the lipid contents of the foods. SCCPs in eggs (high lipid content) were dominated by more-chlorinated SCCPs (particularly Cl8-SCCPs, which contributed 43% of the total) but SCCPs in seaweed (low lipid content) were dominated by less-chlorinated SCCPs (particularly Cl6-SCCPs, which contributed 46%). Dietary SCCP intakes were calculated using the median SCCP concentrations and estimated 888 and 781 ng/kg/d for male and female Korean adults, respectively. The predominant contributing foods to SCCP dietary exposure differed according to sex and age. Dairy products contributed most (about 50%) for infants/children (1-5 y old), but meat and dairy products contributed most for adult males and females, respectively. Grain contributed most for ≥65 y old.

Legacy and emerging persistent organic pollutants in the freshwater system: Relative distribution, contamination trends, and bioaccumulation.

In this study, a comprehensive investigation was performed to understand the overall occurrence, relative distribution, and bioaccumulation of seven different groups of POPs, comprising 27 polybrominated diphenyl ethers (PBDEs), 76 polychlorinated biphenyls (PCBs), 23 organochlorine pesticides (OCPs), three hexabromocyclododecanes (HBCDs), and 13 perfluoroalkyl substances (PFASs) as legacy POPs, and 41 polychlorinated naphthalenes (PCNs) and 24 short-chain chlorinated paraffins (SCCPs) as emerging POPs, by monitoring crucian carp, sediment, and river water in the freshwater system. Among the targeted POPs, SCCPs were predominant in sediment and crucian carp (more than 95%), while a dominance of PFASs was observed in river water (92%). Principal component analysis revealed four different groups/patterns of POPs in all media: one for PBDEs, PCBs, and OCPs, another for HBCDs and PFASs, and the two others for PCNs and SCCPs. Also, sexually dimorphic growth-dependent accumulation of legacy POPs was observed in crucian carp such that POPs concentration increased with increasing fish size and males recorded significantly higher levels of POPs compared to females.

Species and habitat-dependent accumulation and biomagnification of brominated flame retardants and PBDE metabolites.

The occurrence, species- and habitat-dependent distribution of brominated flame retardants (BFRs) and PBDE metabolites comprising 27 polybrominated diphenyl ethers (PBDEs), 3 hexabromocyclododecanes (HBCDs), tetrabromobisphenol A (TBBPA), 17 methoxylated (MeO-) BDEs, and 8 hydroxylated (OH-) BDEs were determined in marine environments (sediment and seawater) and 20 biota species in food web in the southern part of Korea. The concentration of HBCDs was statistically higher in both pelagic (5.73-60.1 ng/g lipid weight [lw]) and demersal fish (2.45-31.3 ng/g lw), whereas a higher level of OH-BDEs was observed in benthic invertebrates (2.48-40.7 ng/g lw), suggesting different composition of BFRs and PBDE metabolites between species. The concentrations of TBBPA and MeO-BDEs were significantly higher in pelagic fish (1.31-11.3, 6.15-61.5 ng/g lw) than in demersal fish (not detected [N.D.]-4.45, 0.956-8.52 ng/g lw) and benthic invertebrates (N.D.-8.11, 0.182-4.65 ng/g lw), reflecting a dependence on habitat. Additionally, analogue distribution of PBDEs in pelagic fish was similar to that in seawater, whereas the distribution in demersal fish and benthic invertebrates was similar to the distribution in sediment. The bioconcentration factor (BCF) and trophic magnification factor (TMF) of α-HBCD, some of PBDEs, and 6-MeO-BDE47 were up to 5000 and 1, respectively, suggesting strong bioaccumulation and biomagnification.

The occurrence and distribution of polychlorinated naphthalenes (PCNs), focusing on tissue-specific bioaccumulation in crucian carp in South Korea.

The occurrence and distribution of 41 congeners of polychlorinated naphthalenes (PCNs) were investigated in major tissues of crucian carp (muscle, gonad, liver, and blood) and in river sediment to assess the bioaccumulation potential of PCNs. The total PCN concentrations in sediment ranged from 4.37 to 19.5 pg/g dry weight (dw), mainly comprising CN-13, CN-33/34/37, and CN-38/40. Among fish tissues, higher PCN concentrations were observed in the gonads (29.6 ±â€¯10.3 pg/g wet weight, ww) and liver (25.7 ±â€¯4.35 pg/g ww) of crucian carp than in the muscle (2.17 ±â€¯0.68 pg/g ww). CN-28/43, CN-33/34/37, CN-42, CN-52/60, CN-53/55, and CN-66/67 congeners were detected most frequently and had the highest concentration among all crucian carp tissues. We investigated the association between the PCN concentration in each tissue (muscle, liver, and gonad) and the size of the fish (total length and weight) and found positive correlations between the PCN concentration in the gonads and the total length and weight (p < 0.05, Spearman correlation).

Evaluation of the current contamination status of PFASs and OPFRs in South Korean tap water associated with its origin.

We investigated the concentrations of perfluoroalkyl substances (PFASs) and organophosphate flame retardants (OPFRs) in 44 tap water samples, collected from eight major cities in South Korea served by four representative watersheds, to evaluate the water contamination status. The total concentrations of PFASs and OPFRs ranged from 1.44 to 224ng/L (median=11.9ng/L), and 74.0 to 342ng/L (median=151ng/L), respectively. The predominant compounds in tap water were perfluorohexane sulfonate (PFHxS), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), tris(2-chloroethyl) phosphate (TCEP), tris(chloroisopropyl) phosphate (TCIPP), and tris(2-butoxyethyl) phosphate (TBOEP). Tap water originating from the Nakdong River within an industrial complex showed a notably higher PFHxS proportion to total PFASs. In addition, significantly higher PFAS levels were found in river-originating tap water than in lake/reservoir-originating tap water (Mann-Whitney U test, p<0.05). Meanwhile, major OPFRs showed no clear difference in distribution by region, and no significant difference in major OPFR levels was observed according to tap water origin. Finally, the average human exposure via tap water consumption was estimated for PFASs (46.8ng/person/day) and OPFRs (254ng/person/day).

The occurrence and distribution of hexabromocyclododecanes in freshwater systems, focusing on tissue-specific bioaccumulation in crucian carp.

The occurrence and distribution of hexabromocyclododecanes (HBCDs) were investigated in freshwater, sediment, and selected crucian carp (Carassius carassius) tissues (muscle, liver, egg, and blood) to evaluate the potential for HBCDs bioaccumulation. The HBCDs concentration ranged from not detected to 0.35ng/L in freshwater, and from 0.037 to 35.4ng/g-dw in sediment. The highest HBCDs concentration was detected in crucian carp liver (5.14±8.15ng/g-ww), followed by egg (3.88±10.1ng/g-ww), blood (0.61±0.63ng/mL), and muscle (0.38±0.70ng/g-ww). In all crucian carp tissues, α-HBCD was the predominant stereoisomer, and the fraction of α-HBCD as a proportion of the total HBCDs in liver tissue (96%) was higher than that in egg tissue (79%). There was a positive correlation between the HBCDs concentration in crucian carp muscle and body size (p<0.01, Spearman). The biota-sediment accumulation factor (BSAF) (0.14) and bioconcentration factor (BCF) (137,000L/kg) values were estimated in crucian carp muscle using field-based data.

Tissue-specific distribution and bioaccumulation potential of organophosphate flame retardants in crucian carp.

The concentrations, distributions, and bioaccumulation of nine organophosphate flame retardants (OPFRs) were investigated in both abiotic and biotic media, comprising river water, sediment, and crucian carp. The highest concentrations were observed in liver (6.22-18.1 ng/g ww), and the levels in muscle (4.23-7.75 ng/g ww) and gonad (3.08-7.70 ng/g ww) were similar. In whole blood, tris(2-butoxyethyl) phosphate (TBOEP; 31.1-256 ng/mL) accounted for 90% of the total OPFR concentration. Distributions of OPFRs differed between biotic and abiotic media, as tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), and TBOEP were dominant in abiotic media, whereas triethyl phosphate (TEP), tri-n-butyl phosphate (TNBP), TCEP, and TBOEP dominated in crucian carp. The TNBP had remarkable accumulation potential among nine OPFRs, which the TNBP concentrations in muscle increased with increased total length and body weight. The higher perfusion rate of TNBP to female eggs were observed rather than to male gonads as the concentrations were higher in males than in females, while the opposite results were observed in gonad. Moreover, the concentration of TNBP in female muscle began to decrease near maximum growth as a sexually dimorphic difference in crucian carp. This is the first study to simultaneously investigate the fate of OPFRs in biotic and abiotic media and to show sex differences.

PBDEs and their structural analogues in marine environments: Fate and expected formation mechanisms compared with diverse environments.

The concentrations and relative distributions of 27 polybrominated diphenyl ethers (PBDEs) and 17 methoxylated (MeO-) and 8 hydroxylated (OH-) BDEs were determined in marine environments including sediments, bivalves, and seawater along the southern coast of South Korea to understand their fates and possible formation mechanisms. The relative and substituent distributions of the PBDEs and their structural analogues varied according to the characteristics of the media. PBDEs were dominant in marine sediments and seawater, whereas MeO-BDEs made the highest contributions in bivalves. Similar patterns were previously identified in inland environments in Korea, except in river water where OH-BDEs were dominant. The natural formation of structural analogues might be the main mechanism in marine, as ortho-substituted naturally occurring MeO- and OH-BDEs were dominant in all media and seemed to be more produced than in inland environments. In addition, the higher concentrations of meta-substituted MeO-BDEs nearshore than offshore was observed. This is the first study comparing marine (near- and offshore) and inland to understand the differences in their fate and possible formation mechanisms in each environmental conditions.

Brominated flame retardants in marine environment focused on aquaculture area: Occurrence, source and bioaccumulation.

Brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA), and hexabromocyclododecanes (HBCDs), were investigated in bivalve (i.e., oyster (Crassostrea gigas) and mussel (Mytilus coruscus)), sediment, and seawater samples collected from aquaculture areas in South Korea to identify their occurrence, sources, and bioaccumulation. Among the studied chemicals, HBCDs predominated in bivalves and sediment, with concentrations of ND-67.52ng/g lipid weight and 3.47-168ng/g dry weight, respectively, while TBBPA was the highest contributor in seawater (ND-2.79ng/L). Compared with a non-aquaculture area, HBCD and PBDE concentrations were significantly higher in all matrices in the aquaculture area (Mann-Whitney U test, p<0.05), suggesting that sources may be located near or associated with the aquaculture areas, such as industrial complexes and expanded polystyrene buoys. Finally, the bioconcentration factor (BCF) and biota-sediment accumulation factor (BSAF) were estimated. Among the studied BFRs, BDE-47 (BCF: 1.70×106L/kg; BSAF: 20.92) and α-HBCD (BCF: 1.05×106L/kg; BSAF: 0.13) showed the highest accumulation potentials in bivalves.