Quantitative source apportionment of PAHs in sediments of Little Menomonee River, Wisconsin: weathered creosote versus urban background

A framework for prioritizing contaminants in retrospective ecological assessments: Application in the Milwaukee Estuary (Milwaukee, WI)

Watersheds are subjected to diverse anthropogenic inputs, exposing aquatic biota to a wide range of chemicals. Detection of multiple, different chemicals can challenge natural resource managers who often have to determine where to allocate potentially limited resources. Here, we describe a weight-of-evidence framework for retrospectively prioritizing aquatic contaminants. To demonstrate framework utility, we used data from 96-h caged fish studies to prioritize chemicals detected in the Milwaukee Estuary (WI, USA; 2017-2018). Across study years, 77/178 targeted chemicals were detected. Chemicals were assigned prioritization scores based on spatial and temporal detection frequency, environmental distribution, environmental fate, ecotoxicological potential, and effect prediction. Chemicals were sorted into priority bins based on the intersection of prioritization score and data availability. Data-limited chemicals represented those that did not have sufficient data to adequately evaluate ecotoxicological potential or environmental fate. Seven compounds (fluoranthene, benzo[a]pyrene, pyrene, atrazine, metolachlor, phenanthrene, and DEET) were identified as high or medium priority and data sufficient and flagged as candidates for further effects-based monitoring studies. Twenty-one compounds were identified as high or medium priority and data limited and flagged as candidates for further ecotoxicological research. Fifteen chemicals were flagged as the lowest priority in the watershed. One of these chemicals (2-methylnaphthalene) displayed no data limitations and was flagged as a definitively low-priority chemical. The remaining chemicals displayed some data limitations and were considered lower-priority compounds (contingent on further ecotoxicological and environmental fate assessments). The remaining 34 compounds were flagged as low or medium priority. Altogether, this prioritization provided a screening-level (non-definitive) assessment that could be used to focus further resource management and risk assessment activities in the Milwaukee Estuary. Furthermore, by providing detailed methodology and a practical example with real experimental data, we demonstrated that the proposed framework represents a transparent and adaptable approach for prioritizing contaminants in freshwater environments. Integr Environ Assess Manag 2023;19:1276-1296. © 2022 SETAC.

Using positive matrix factorization to unmix PAH fingerprints in contaminated sediments

Some of the challenges to apportioning PAH-related remedy costs at contaminated sediment sites include the lack of source samples, different PAH signatures associated with the same source, historical PAH sources long removed, mixing of urban sediment by boat traffic, and, in turn, PAHs mixing and weathering. Unmixing of PAH fingerprints in sediment sites to PAH source classes (petrogenic, pyrogenic, and runoff) is typically a first step to tracking PAH upland sources and ultimately, responsible parties. This work demonstrates using positive matrix factorization (PMF) as a method to unmix PAH fingerprints to its source classes.A large PAH dataset (over 700 samples) assembled from contaminated urban sediment sites was used as an input to PMF. Using a 3-factor PMF analysis, a petrogenic, pyrogenic, and runoff/weathered PAH end-member fingerprints were identified. Different numerical mixing percentages of the PMF-identified end-member sources were able to replicate the sediment-measured PAH fingerprints, with the percent contribution of each of the end members to each sediment sample calculated. The demonstrated work provides a method to satisfy the unmixing of PAH fingerprints to its source classes, as a step towards apportioning of PAH contamination.

Dissolved polycyclic aromatic hydrocarbons from the Northwestern Pacific to the Southern Ocean: Surface seawater distribution, source apportionment, and air-seawater exchange

Polycyclic aromatic hydrocarbons (PAHs) as a group of toxic and carcinogenic compounds are large scale globally emitted anthropogenic pollutants mainly emitted into the atmosphere. However, atmospheric transport cannot fully explain the spatial variability of PAHs in the marine atmosphere and seawater. It is hypothesized that PAHs accumulated in seawater and ocean circulation can also influence PAHs observed in air above the ocean. In order to investigate PAHs in seawater as a potential secondary source to air, we collected paired air and seawater samples during a research cruise from China to the Antarctic in 2018-2019, covering the Pacific Ocean, the Indian Ocean, and the Southern Ocean. Summed concentrations of 28 analyzed PAHs in seawater were highest in the Pacific Ocean (4000 ± 1400 pg/L), followed by the Indian Ocean (2700 ± 1000 pg/L), and the Southern Ocean (2300 ± 520 pg/L). Three-ringed PAHs dominated the composition profile. We found that PAH levels in the Pacific and Indian Oceans were strong inversely correlated with salinity and distance to the coastline. This suggests that riverine inputs and continental discharges are important sources of PAHs to the marine environment. Derived air-seawater fugacity ratios suggest that net fluxes of PAHs were from seawater to the air in the Pacific and Indian Oceans at 9.0-8100 (median: 1600) ng/m²/d and 290-2000 (median: 1300) ng/m²/d, respectively. In the Southern Ocean, the net flow of PAHs was from air to seawater with a flux of -1000-450 (median: -82) ng/m²/d. Source apportionment from two different models suggested that the largest contribution to total PAHs was from petrogenic sources (44-57%), followed by coal/wood combustion (30-31%), fossil fuel combustion (15%), and engine combustion emissions (2.8-9.5%). Higher contributions from petrogenic sources were found at sites close to coastal regions. Both coal/wood combustion and petrogenic sources are responsible for the PAH concentrations detected in the Indian and Southern Oceans.

Characterization of polycyclic aromatic hydrocarbons in the Great Lakes Basin using dreissenid mussels

The National Oceanic and Atmospheric Administration (NOAA), National Centers for Coastal Ocean Science (NCCOS) Mussel Watch Program (MWP), conducts basin-wide monitoring and place-based assessments using dreissenid mussels as bioindicators of chemical contamination in the Laurentian Great Lakes. Polycyclic aromatic hydrocarbons (PAHs) body burden results for the period 2009-2018 were combined into one dataset from multiple MWP studies allowing for a robust characterization of PAH contamination. Patterns in PAH data were identified using descriptive statistics and machine learning techniques. Relationships between total PAH concentration in dreissenid mussel tissue, impervious surface percentages, and PAH relative concentration were identified and used to build a predictive model for the Great Lakes Basin. Significant positive correlation was identified by the Spearman's rank correlation test between total PAH concentration and percent impervious surface. The findings support the paradigm that PAHs are primarily derived from land-based sources. Offshore and riverine locations had the lowest and highest median total PAH concentrations, respectively. PAH assemblages and ratios indicated that pyrogenic sources were more predominant than petrogenic sources and that PAHs at offshore sites exhibited relatively more weathering compared to inshore sites.

An Integrated Approach for Source Apportionment and Health Risk Assessment of Heavy Metals in Subtropical Agricultural Soils, Eastern China

Unreasonable human activities may cause the accumulation of heavy metals (HMs) in the agricultural soil, which will ultimately threaten the quality of soil environment, the safety of agricultural products, and human health. Therefore, the accumulation characteristics, potential sources, and health risks of HMs in agricultural soils in China’s subtropical regions were investigated. The mean Hg, Cu, Zn, Pb, and Cd concentrations of agricultural soil in Jinhua City have exceeded the corresponding background values of Zhejiang Province, while the mean concentrations of determined 8 HMs were less than their corresponding risk-screening values for soil contamination of agricultural land in China. The spatial distribution of As, Cr, Ni, Cu, and Pb were generally distributed in large patches, and Hg, Zn, and Cd were generally sporadically distributed. A positive definite matrix factor analysis (PMF) model had better performance than an absolute principal component–multiple linear regression (APCS-MLR) model in the identification of major sources of soil HMs, as it revealed higher R2 value (0.81–0.99) and lower prediction error (−0.93–0.25%). The noncarcinogenic risks (HI) of the 8 HMs to adults and children were within the acceptable range, while the carcinogenic risk (RI) of children has exceeded the safety threshold, which needs to be addressed by relevant departments. The PMF based human health risk assessment model indicated that industrial sources contributed the highest risk to HI (32.92% and 30.47%) and RI (60.74% and 61.5%) for adults and children, followed by agricultural sources (21.34%, 29.31% and 32.94% 33.19%). Therefore, integrated environmental management should be implemented to control and reduce the accumulation of soil HMs from agricultural and industrial sources.

Accumulation of Pollutants in Proglacial Lake Sediments: Impacts of Glacial Meltwater and Anthropogenic Activities

With global warming, the melting of glaciers can result in the release of pollutants into the environment. For remote Alpine lakes, both atmosphere-deposited anthropogenic pollutants and glacier-released pollutants can eventually sink in the sediment. To date, there has, to the best of our knowledge, been no attempt at quantifying the contributions of these processes to the accumulation of pollutants in glacial lake sediment. To fill this gap, a semi-enclosed proglacial lake located in the southern Tibetan Plateau was chosen and a 28 cm sediment core, which can be dated back to 1836, was used to explore the temporal trends of trace elements, Hg, and black carbon (BC) during the past two centuries. Geochemical indicators (Rb/Sr, Ti-Zr-Hf, and sedimentary rate) in sediment showed an overall continuous warming of the lake, while the temporal trends of fluxes of toxic elements and BC were broadly associated with their emission patterns. By using a positive matrix factorization model, the contribution of the anthropogenic source rose from <10% in the 1850s to >40% after the 1980s. However, the signal of glacial meltwater release was also distinct, and the greatest contribution of ice-snow meltwater reached up to 61% in the 1950s. Regarding the most recent two decades, 90% of pollutant deposition in the Tibetan sediment can be attributed to the combined forces of primary emissions and glacial release.

Large-scale monitoring and ecological risk assessment of persistent toxic substances in riverine, estuarine, and coastal sediments of the Yellow and Bohai seas

The Yellow and Bohai seas comprise one of the most rapidly developing regions in the world, but efforts to assess coastal pollution by persistent toxic substances (PTSs) on wide spatial scale are lacking. The present study aimed to (1) measure the concentrations of PTSs, such as polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and styrene oligomers (SOs) via large-scale sediment monitoring (total of 125 locations), (2) assess potential ecological risk of PTSs in sediments to coastal ecosystems, (3) estimate various sources and fresh inputs of PTSs, (4) determine distribution patterns of PTSs by human activities and land-use type, and (5) address decadal (2008-2018) changes in distributions of PTSs. The high concentrations of PAHs [> 7000 ng g^-1 dry weight (dw)] in sediments were detected in Nantong in the Yellow Sea of China (YSC) and Huludao and Qinhuangdao in the Bohai Sea (BS), whereas lesser concentrations (< 200 ng g^-1 dw) were detected in the Yellow Sea of Korea (YSK). We found relatively high concentrations of sedimentary APs and SOs in Nantong, Huludao, and Qinhuangdao from the YSC and BS regions, but corresponding concentrations were generally below < 100 ng g^-1 dw in other locations. Concentrations of PAHs at 38 locations (30% of YSC and BS) posed a potential risk to aquatic ecosystems, whereas relatively low risk concentrations occurred in all locations of YSK. The main source of PAHs (concentrated in YSC and BS) were by-products of diesel and gasoline combustion (42% of total concentration), whereas biomass combustion (24%) dominated in YSK. Fresh inputs of PTSs indicated that the generation and use of PTSs continue across all regions and locations. Among PTSs, concentrations of PAHs were significantly associated with location (p < 0.05) relative to land-use within a given region, whereas concentrations of APs and SOs showed no significant relationships (p > 0.05) among or within regions. Over time, concentrations of PAHs have generally declined, but sediment contamination has increased at some locations in China, with sources shifting from a mixture of PAHs types to those linked to diesel and gasoline combustion. Additional studies are needed on the fate and potential ecological risk posed by certain PTSs in hotspots. This is one of the first efforts providing backgrounds on PTS pollution in the large marine ecosystem of the Yellow and Bohai seas.

Source apportionment of polycyclic aromatic hydrocarbons (PAHs) in small craft harbor (SCH) surficial sediments in Nova Scotia, Canada

Multiple source apportionment approaches were employed to investigate PAH sources which contribute to small craft harbor (SCH) sediments in Nova Scotia (NS), Canada. A total of 580 sediment samples were analyzed using PAH diagnostic ratios, Unmix Optimum receptor modeling, and by assessment of the composition of the PAH profile. PAH diagnostic ratios suggest PAHs are primarily of pyrogenic (thermal) origin, while UnmixO modeling identifies four individual sources which best describe surficial sediments and suggests contributions from both pyrogenic and petrogenic origins. These include coal combustion, automobile exhaust, and biomass incineration. PAH profile assessment determined an overwhelming contribution of high molecular weight PAHs, which exhibited a strong correlation with total PAH concentrations.

Pollution Assessment and Source Apportionment of Trace Metals in Urban Topsoil of Xi'an City in Northwest China

Sixty-two topsoil samples were collected within the third ring road of Xi'an City in Northwest China and analyzed by X-ray fluorescence spectrometry for the concentrations of As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn. The pollution levels of trace metals were assessed by pollution index (PI) and Nemerow pollution index (NPI). Meanwhile, the sources of trace metals were apportioned by receptor models, including positive matrix factorization (PMF), UNMIX, and principal component analysis-multiple linear regression (PCA-MLR). The average concentrations of the trace metals analyzed in the urban soil exceeded the corresponding soil element background values of Shaanxi Province, especially for Co, which was 2.38 times higher than the corresponding background value. The mean of PI was 2.38 for Co, reflecting a moderate pollution level, and ranged from 1.07 to 1.72 for other trace metals, presenting slight pollution levels. The NPI of trace metals varied between 1.20 and 3.50 with an average of 2.00, indicating that trace metals presented slight pollution in 62.90% of soil samples, moderate pollution in 30.65% of soil samples, and heavy pollution in 6.45% of soil samples, respectively. Three sources of trace metals apportioned by the three receptor models were mixed nature and anthropogenic source, traffic exhaust, and industrial emissions. The contributions of them were 38.58%, 32.72%, and 28.70% from the PMF, 65.36%, 17.76%, and 16.88% through the UNMIX and 49.16%, 38.90%, and 11.94% via the PCA-MLR, respectively. Meanwhile, the study results suggested that the combined usage of multiple receptor models is a good method to apportion the source compositions and contributions of trace metals in urban soil.

Contaminant Concentrations in Sediments, Aquatic Invertebrates, and Fish in Proximity to Rail Tracks Used for Coal Transport in the Pacific Northwest (USA): A Baseline Assessment

Railway transport of coal poses an environmental risk, because coal dust contains polycyclic aromatic hydrocarbons (PAHs), mercury, and other trace metals. In the Pacific Northwest of the United States, proposed infrastructure projects could result in an increase in coal transport by train through the Columbia River corridor. Baseline information is needed on current distributions, levels, and spatial patterns of coal dust-derived contaminants in habitats and organisms adjacent to existing coal transport lines. To that end, we collected aquatic surface sediments, aquatic insects, and juvenile fish in 2014 and 2015 from Horsethief Lake State Park and Steigerwald National Wildlife Refuge, both located in Washington state close to the rail line and within the Columbia River Gorge National Scenic Area. Two subsites in each area were selected: one close to the rail line and one far from the rail line. Detected PAH concentrations were relatively low compared with those measured at more urbanized areas. Some contaminants were measured at higher concentrations at the subsites close to the rail line, but it was not possible to link the contaminants to a definitive source. Trace metal concentrations were only slightly higher than background concentrations, but a few of the more sensitive benchmarks were exceeded, including those for arsenic, lead, and selenium in fish tissue and fluoranthene, cadmium, copper, manganese, nickel, zinc, iron, and arsenic in sediments. At Horsethief Lake, Chinook salmon and yellow perch showed lower total mercury body burdens than other species, but PAH body burdens did not differ significantly among species. Differences in the species caught among subsites and the low number of invertebrate samples rendered food web comparisons difficult, but these data show that the PAHs and trace metals, including mercury, are accumulating in these wetland sites and in some resident organisms.

Unmix Optimum analysis of PAH sediment sources

Unmix Optimum (UnmixO) was developed to analyze data, such as sediment PAH data, that were resistant to existing methods of multivariate analysis. Using a geometrical approach, UnmixO uses multiple advanced nonlinear optimization algorithms to find potential sources that obey non-negativity constraints while optimally fitting the data. UnmixO does not require specific knowledge of the uncertainties in the data and will work better for smaller data sets than other multivariate models. UnmixO was able to identify polycyclic aromatic hydrocarbon (PAH) contaminant sources contributing to sediment samples based on sample composition data with good diagnostic values. Results were compared to published EPA Chemical Mass Balance (CMB) sediment results from Lady Bird Lake (LBL) Austin, TX and 40 lakes (40LKS) across the U.S. A Chi-sum approach determined which UnmixO source profile best matched profiles used in CMB sediment studies; two coal tar (CT) sealcoat sources and a mixed combustion source contributed to the sediment PAHs. These results were consistent with CMB results for the LBL and 40LKS studies that estimated CT sealcoats contribute over 80% of PAHs to urban lakes. UnmixO results also showed that CT sealant's contribution to sediments decreased after the City of Austin ban in 2006.

State of the art and future challenges for polycyclic aromatic hydrocarbons is sediments: sources, fate, bioavailability and remediation techniques

Polycyclic aromatic hydrocarbons (PAHs) are amongst the most abundant contaminants found in the aquatic environment. Due to their toxicity and carcinogenicity, their sources, fate, behaviour, and cleanup techniques have been widely investigated in the last several decades. When entering the sediment-water system, PAH fate is determined by particular PAH and sediment physico-chemical properties. Most of the PAHs will be associated with fine-grained, organic-rich, sediment material. This makes sediment an ultimate sink for these pollutants. This association results in sediment contamination, and in this manner, sediments represent a permanent source of water pollution from which benthic organisms may accumulate toxic compounds, predominantly in lipid-rich tissues. A tendency for biomagnification can result in critical body burdens in higher trophic species. In recent years, researchers have developed numerous methods for measuring bioavailable fractions (chemical methods, non-exhaustive extraction, and biomimetic methods), as valuable tools in a risk-based approach for remediation or management of contaminated sites. Contaminated sediments pose challenging cleanup and management problems, as conventional environmental dredging techniques are invasive, expensive, and sometimes ineffective or hard to apply to large and diverse sediment sites. Recent studies have shown that a combination of strategies including in situ approaches is likely to provide the most effective long-term solution for dealing with contaminated sediments. Such in situ approaches include, but are not limited to: bioaugmentation, biostimulation, phytoremediation, electrokinetic remediation, surfactant addition and application of different sorbent amendments (carbon-rich such as activated carbon and biochar) that can reduce exposure and limit the redistribution of contaminants in the environment.

Multivariate receptor models and robust geostatistics to estimate source apportionment of heavy metals in soils

Absolute principal component score/multiple linear regression (APCS/MLR) and positive matrix factorization (PMF) were applied to a dataset consisting of 10 heavy metals in 300 surface soils samples. Robust geostatistics were used to delineate and compare the factors derived from these two receptor models. Both APCS/MLR and PMF afforded three similar source factors with comparable contributions, but APCS/MLR had some negative and unidentified contributions; thus, PMF, with its optimal non-negativity results, was adopted for source apportionment. Experimental variograms for each factor from two receptor models were built using classical Matheron's and three robust estimators. The best association of experimental variograms fitted to theoretical models differed between the corresponding APCS and PMF-factors. However, kriged interpolation indicated that the corresponding APCS and PMF-factor showed similar spatial variability. Based on PMF and robust geostatistics, three sources of 10 heavy metals in Guangrao were determined. As, Co, Cr, Cu, Mn, Ni, Zn, and partially Hg, Pb, Cd originated from natural source. The factor grouping these heavy metals showed consistent distribution with parent material map. 43.1% of Hg and 13.2% of Pb were related to atmosphere deposition of human inputs, with high values of their association patterns being located around urban areas. 29.6% concentration of Cd was associated with agricultural practice, and the hotspot coincided with the spatial distribution of vegetable-producing soils. Overall, natural source, atmosphere deposition of human emissions, and agricultural practices, explained 81.1%, 7.3%, and 11.6% of the total of 10 heavy metals concentrations, respectively. Receptor models coupled with robust geostatistics could successfully estimate the source apportionment of heavy metals in soils.

Characterization of polycyclic aromatic hydrocarbons (PAHs) in small craft harbour (SCH) sediments in Nova Scotia, Canada

Polycyclic aromatic hydrocarbons (PAHs) have been widely studied in sediments due to their ubiquity and persistence in aquatic environments and potential for impairment to biota. Small craft harbour (SCH) sediments in Nova Scotia (NS), Canada, have yet to be studied comprehensively. SCHs are essential to the fishing industry, which is important for the Canadian economy. This spatiotemporal characterization study evaluated thirty-one SCHs across NS between 2001 and 2017 by analyzing sediment reports (secondary data). Sediment PAH concentrations varied widely across all SCHs. Few SCHs exhibited sediment PAH concentrations likely to impair biota based on comparison to sediment quality guidelines. Sediments in the Gulf region of NS were least impacted by PAHs, while the Southwest region was most impacted. Distribution of individual PAHs in sediments follows global trends, with high molecular weight PAHs dominating samples.

Polycyclic aromatic hydrocarbons in surface sediments of the mid-Adriatic and along the Croatian coast: Levels, distributions and sources

This study provides contamination levels, distributions and source apportionment of PAHs in surface sediments in the mid-Adriatic and along the Croatian coast. Median summed concentrations of parent and alkyl-PAHs are circa 10 times lower in the off-shore transect stations of the mid-Adriatic (22.3 and 18.2 μg.kg^-1 d.w.) than the ranges determined at the coastal stations, including those of Kaštela bay (227-331 and 11.7-197 μg.kg^-1 d.w., respectively). The highest levels, circa 20 times higher, were found in Šibenik bay (median 6603 and 3051 μg.kg^-1). The overall range of PAH concentrations spans more than 2000 times between the lowest and the highest contamination level. The geographical distributions reflect the presence of strong gradients at local and regional scales. A major factor influencing sedimentary PAH distributions at local scale appears to be the distance from their known continental and coastal upstream emission sites (urban, industrial, harbour …), whereas at regional scale, this distribution depends more on the routes of entry of PAHs into the study area. Two combustion and one petroleum model source profiles of PAHs were determined by alternative least square analysis. Benzo[b+j]fluoranthenes and fluoranthene/pyrene are compounds characterizing two pyrogenic sources respectively, while signatures of alkyl-substituted homologues (phenanthrenes/anthracenes, fluranthenes/pyrenes, chrysenes and dibenzothiophenes) delineate a petrogenic source profile. The quantitative apportionment of source contributions shows significant geographical differences, with a dominant petrogenic source found along the mid-Adriatic transect (approximately 74%) and in Kaštela bay (61%). In the coastal sediments about a fifty-fifty contamination mix is assigned to a petrogenic/pyrogenic source of PAHs (47% and 53% respectively), whereas in Šibenik bay a strong predominance is apportioned to the combustion compounds (81%).

Polycyclic aromatic hydrocarbon contamination and source profiling in watersheds serving three small Wisconsin, USA cities

Polycyclic aromatic hydrocarbons (PAHs) continue to be common environmental contaminants. The anthropogenic sources of these compounds are broadly classed as petrogenic and pyrogenic, but more importantly specific sources including activities such as coal burning, oil spills, and application of coal tar sealants can be identified based on several types of data analysis. Several studies have focused on PAHs in sediments of lakes, streams, and stormwater ponds in larger urban areas, finding contamination arising from a number of different sources and correlating well to land use in the nearby watershed. We report here a study of PAH concentrations and source identification for river and lakebed sediments in and upstream of three smaller Wisconsin municipalities: Eau Claire (Eau Claire River), Stevens Point (Plover River), and Racine (Root River). PAH concentrations increased with increasing developed land cover and impervious surface. Concentrations within the cities and upstream agricultural or residential areas do not rise to the level found in larger urban areas or stormwater ponds servicing industrial or commercial land use, but can rise to a level that exceeds the Threshold Effects Concentration (TEC). Concentrations in areas with natural landcovers were very low, with the exception of one sample in a wetland with unusually high organic content. Multiple lines of evidence indicate that coal tar-based pavement sealants are a primary source of the contamination in all three cities. PAH concentrations reported here are likely conservative, and these results indicate that even smaller cities using detention ponds as a stormwater management practice should be prepared for costs of contaminated sediment disposal.

Analysis and toxicity of 59 PAH in petrogenic and pyrogenic environmental samples including dibenzopyrenes, 7H-benzo[c]fluorene, 5-methylchrysene and 1-methylpyrene

In this study 59 PAH were analyzed in samples of petrogenic and pyrogenic sources as well as mixed environmental matrices. Among the analytes, PAH of molecular weights from 128 Da to 302 Da in alkylated and in native form were included. Results show that non-EPA PAH make up 69.3–95.1% of the overall toxic equivalents (TEQ) as based on the toxic equivalent factors (TEF) of 24 PAH. Particularly 7H-benzo[c]fluorene, dibenzopyrene isomers and alkylated PAH (in particular 5-methylchrysene and 1-methylpyrene) turned out to have a huge impact on the toxicity and must not be neglected in future risk assessment. In detail, dibenzopyrenes have a high impact on toxicity predominantly in pyrogenic materials (21% to 84%; mean: 59%) whereas 7H-benzo[c]fluorene dominates toxicity of petrogenic materials (up to 80%; mean: 26%). However, in the studied mixed environmental samples the toxic impact of both groups together is as high as about 80%. Many non-EPA PAH are not considered in risk assessment and amongst them there are some very toxic ones. This needs to be carefully evaluated in future studies.

Systematic developmental neurotoxicity assessment of a representative PAH Superfund mixture using zebrafish

Superfund sites often consist of complex mixtures of polycyclic aromatic hydrocarbons (PAHs). It is widely recognized that PAHs pose risks to human and environmental health, but the risks posed by exposure to PAH mixtures are unclear. We constructed an environmentally relevant PAH mixture with the top 10 most prevalent PAHs (SM10) from a Superfund site derived from environmental passive sampling data. Using the zebrafish model, we measured body burden at 48 hours post fertilization (hpf) and evaluated the developmental and neurotoxicity of SM10 and the 10 individual constituents at 24 hours post fertilization (hpf) and 5 days post fertilization (dpf). Zebrafish embryos were exposed from 6 to 120 hpf to (1) the SM10 mixture, (2) a variety of individual PAHs: pyrene, fluoranthene, retene, benzo[a]anthracene, chrysene, naphthalene, acenaphthene, phenanthrene, fluorene, and 2-methylnaphthalene. We demonstrated that SM10 and only 3 of the individual PAHs were developmentally toxic. Subsequently, we constructed and exposed developing zebrafish to two sub-mixtures: SM3 (comprised of 3 of the developmentally toxicity PAHs) and SM7 (7 non-developmentally toxic PAHs). We found that the SM3 toxicity profile was similar to SM10, and SM7 unexpectedly elicited developmental toxicity unlike that seen with its individual components. The results demonstrated that the overall developmental toxicity in the mixtures could be explained using the general concentration addition model. To determine if exposures activated the AHR pathway, spatial expression of CYP1A was evaluated in the 10 individual PAHs and the 3 mixtures at 5 dpf. Results showed activation of AHR in the liver and vasculature for the mixtures and some individual PAHs. Embryos exposed to SM10 during development and raised in chemical-free water into adulthood exhibited decreased learning and responses to startle stimulus indicating that developmental SM10 exposures affect neurobehavior. Collectively, these results exemplify the utility of zebrafish to investigate the developmental and neurotoxicity of complex mixtures.

Improved source apportionment of PAHs and Pb by integrating Pb stable isotopes and positive matrix factorization application (PAHs): A historical record case study from the northern South China Sea

To obtain the historical changes of pyrogenic sources, integrated source apportionment methods, which include PAH compositions, diagnostic ratios (DRs), Pb isotopic ratios, and positive matrix factorization (PMF) model, were developed and applied in sediments of the northern South China Sea. These methods provided a gradually clear picture of energy structural change. Spatially, Σ₁₅PAH (11.3 to 95.5ng/g) and Pb (10.2 to 74.6μg/g) generally exhibited decreasing concentration gradient offshore; while the highest levels of PAHs and Pb were observed near the southern Taiwan Strait, which may be induced by accumulation of different fluvial input. Historical records of pollutants followed closely with the economic development of China, with fast growth of Σ₁₅PAH and Pb occurring since the 1980s and 1990s, respectively. The phasing-out of leaded gasoline in China was captured with a sharp decrease of Pb after the mid-1990s. PAHs and Pb correlated well with TOC and clay content for core sediments, which was not observed for surface sediments. There was an up-core increase of high molecular PAH proportions. Coal and biomass burning were then qualitatively identified as the major sources of PAHs with DRs. Furthermore, shift toward less radiogenic signatures of Pb isotopic ratios after 1900 revealed the start and growing importance of industrial sources. Finally, a greater separation and quantification of various input was achieved by a three-factor PMF model, which made it clear that biomass burning, coal combustion, and vehicle emissions accounted for 40±20%, 41±13%, and 19±12% of PAHs through the core. Biomass and coal combustion acted as major sources before 2000, while contributions from vehicle emission soared thereafter. The integrated multi-methodologies here improved the source apportionment by reducing biases with a step-down and cross-validation perspective, which could be similarly applied to other aquatic systems.

Source apportionment of polycyclic aromatic carbons (PAHs) in sediment core from Honghu Lake, central China: comparison study of three receptor models

The spatial distribution of polycyclic aromatic hydrocarbons (PAHs) and their source contributions employing receptor models has been widely reported. However, the temporal distribution of PAH source contributions is less studied. Thus, in this paper, three receptor models including principle component analysis-multiple linear regression (PCA-MLR), positive matrix factorization (PMF), and Unmix were used to PAH source apportionment study in a sediment core from Honghu Lake, China. Sixteen USEPA priority PAHs in 37 sliced sediment layers (1-cm interval) were measured, with the concentrations of ∑₁₆PAH (sum of 16 PAHs) ranging from 93.0 to 431 ng g^-1. The source apportionment results derived from three receptor models were similar, with three common sources: mixed sources of biomass burning and coal combustion (31.0-41.4% on average), petroleum combustion (31.8-45.5%), and oil leakage (13.1-21.3%). The PMF model segregated an additional source: domestic coal combustion (contributed 20.9% to the ∑₁₆PAHs). Four aspects including intra-comparison, inter-comparison, source numbers and compositions, and source contributions were considered in comparison study. The results indicated that the PMF model was most reasonable in PAH source apportionment research in this study.

Polycyclic aromatic hydrocarbons (PAHs) in Chinese forest soils: profile composition, spatial variations and source apportionment

Previous studies reported that forest ecosystems can play a vital role in scavenging anthropogenic polycyclic aromatic hydrocarbons (PAHs) and act as primary reservoirs of these environmental pollutants. The present study aimed to investigate the occurrence, spatial pattern and source apportionment of PAHs across Chinese background forest soils (O- & A-horizons). The 143 soils collected from 30 mountains showed significantly (p < 0.05) higher levels of ∑₁₅PAHs (ng g⁻¹ dw) in O-horizon (222 ± 182) than A-horizon (168 ± 161). A progressive increase in the levels of lighter PAHs was observed along altitudinal gradient, however heavier PAHs did not show any variations. Carbon contents (TOC & BC) of forest soils were found weakly correlated (p < 0.01) with low molecular weight (LMW)-PAHs but showed no relation with high molecular weight (HMW)-PAHs. Source apportionment results using PMF and PCA revealed that PAHs in forest soils mainly come from local biomass burning and/or coal combustion and attributed that forest soils may become a potential sink for PAHs in the region.

Primary sources and toxicity of PAHs in Milwaukee-area streambed sediment

High concentrations of polycyclic aromatic hydrocarbons (PAHs) in streams can be a significant stressor to aquatic organisms. To understand the likely sources and toxicity of PAHs in Milwaukee-area streams, streambed sediment samples from 40 sites and parking lot dust samples from 6 sites were analyzed for 38 parent PAHs and 25 alkylated PAHs. Diagnostic ratios, profile correlations, principal components analysis, source-receptor modeling, and mass fractions analysis were used to identify potential PAH sources to streambed sediment samples, and land-use analysis was used to relate streambed sediment PAH concentrations to different urban-related land uses. On the basis of this multiple lines-of-evidence approach, coal-tar pavement sealant was indicated as the primary source of PAHs in a majority of streambed sediment samples, contributing an estimated 77% of total PAHs to samples, on average. Comparison with the probable effect concentrations and (or) the equilibrium partitioning sediment benchmark indicates that 78% of stream sediment samples are likely to cause adverse effects to benthic organisms. Laboratory toxicity tests on a 16-sample subset of the streambed sites using the amphipod Hyalella azteca (28-d) and the midge Chironomus dilutus (10-d) measured significant reductions in 1 or more biological endpoints, including survival, in 75% of samples, with H. azteca more responsive than C. dilutus. Environ Toxicol Chem 2017;36:1622-1635. © 2016 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.

Sources and mass inventory of sedimentary polycyclic aromatic hydrocarbons in the Gulf of Thailand: Implications for pathways and energy structure in SE Asia

Surface sediments obtained from a matrix of 92 sample sites in the Gulf of Thailand (GOT) were analyzed for a comprehensive study of the distribution, sources, and mass inventory of polycyclic aromatic hydrocarbons (PAHs) to assess their input pathways and impacts of the regional land-based energy structure on the deposition of PAHs on the adjacent continental margins. The concentration of 16 PAHs in the GOT ranged from 2.6 to 78.1ng/g (dry weight), and the mean concentration was 19.4±15.1ng/g. The spatial distribution pattern of 16 PAH was generally consistent with that of sediment grain size, suggesting the influence of regional hydrodynamic conditions. Correlation and principal component analysis of the PAHs indicated that direct land-based inputs were dominantly responsible for the occurrence of PAHs in the upper GOT and the low molecular weight (LMW) PAHs in the coastal region could be from petrogenic sources. A positive matrix factorization (PMF) model apportioned five contributors: petroleum residues (~44%), biomass burning (~13%), vehicular emissions (~11%), coal combustion (~6%), and air-water exchange (~25%). Gas absorption may be a significant external input pathway for the volatile PAHs in the open GOT, which further implies that atmospheric loading could be important for the sink of PAHs in the open sea of the Southeast Asia (SE Asia). The different PAH source patterns obtained and a significant disparity of PAH mass inventory in the sediments along the East and Southeast Asia continental margins can be ascribed mainly to different land-based PAH emission features under the varied regional energy structure in addition to the depositional environment and climatic conditions.

Toxic effects in juvenile sea cucumber Apostichopus japonicas (Selenka) exposure to benzo[a]pyrene

To understand the physiological response of sea cucumber, Apostichopus japonicas, were exposed to different concentration of benzo[a]pyrene (B[a]P), and the growth, survival, antioxidant enzyme (SOD and T-AOC) activities were tested. Meanwhile, the quantitative real-time PCR technology was utilized to quantize the expression of immune related genes (i.e. innate immune genes, HSP genes and anti-oxidative genes). In our result, the SOD activity and T-AOC activity were induced at lower level of B[a]P (0.03 μg/L), however, a reduction of SOD activity and T-AOC activity were observed at relatively high B[a]P concentration (3 and 9 μg/L) for A. japonicas. Furthermore, the distinct expression patterns of selected immune-related genes were detected among different concentrations, and a general trend of down-regulation was observed at higher concentration. Especially, lysozyme almost showed the highest down-regulation at all concentrations, followed by NOS. Collectively, the growth, survival and expression signatures of immune related genes reflected an overall suppression of innate immunity in sea cucumber following exposure. Future functional studies should be carried out to characterize the detailed roles of immune genes and their related responses under B[a]P toxicity. Additionally, better understanding of the molecular indicators governing the healthy status under environmental toxicity would facilitate a healthy and sustainable culture program.

Soil concentrations, occurrence, sources and estimation of air-soil exchange of polychlorinated biphenyls in Indian cities

Past studies have shown potentially increasing levels of polychlorinated biphenyls (PCBs) in the Indian environment. This is the first attempt to investigate the occurrence of PCBs in surface soil and estimate diffusive air-soil exchange, both on a regional scale as well as at local level within the metropolitan environment of India. From the north, New Delhi and Agra, east, Kolkata, west, Mumbai and Goa and Chennai and Bangalore in the southern India were selected for this study. 33 PCB congeners were quantified in surface soil and possible sources were derived using positive matrix factorization model. Net flux directions of PCBs were estimated in seven major metropolitan cities of India along urban-suburban-rural transects. Mean Σ33PCBs concentration in soil (12ng/g dry weight) was nearly twice the concentration found in global background soil, but in line with findings from Pakistan and urban sites of China. Higher abundance of the heavier congeners (6CB-8CB) was prevalent mostly in the urban centers. Cities like Chennai, Mumbai and Kolkata with evidence of ongoing PCB sources did not show significant correlation with soil organic carbon (SOC). This study provides evidence that soil is acting as sink for heavy weight PCB congeners and source for lighter congeners. Atmospheric transport is presumably a controlling factor for occurrence of PCBs in less polluted sites of India.

Binary Mixtures of Polycyclic Aromatic Hydrocarbons Display Nonadditive Mixture Interactions in an In Vitro Liver Cell Model

Polycyclic aromatic hydrocarbons (PAHs) have been labeled contaminants of concern due to their carcinogenic potential, insufficient toxicological data, environmental ubiquity, and inconsistencies in the composition of environmental mixtures. The Environmental Protection Agency is reevaluating current methods for assessing the toxicity of PAHs, including the assumption of toxic additivity in mixtures. This study was aimed at testing mixture interactions through in vitro cell culture experimentation, and modeling the toxicity using quantitative structure-activity relationships (QSAR). Clone-9 rat liver cells were used to analyze cellular proliferation, viability, and genotoxicity of 15 PAHs in single doses and binary mixtures. Tests revealed that many mixtures have nonadditive toxicity, but display varying mixture effects depending on the mixture composition. Many mixtures displayed antagonism, similar to other published studies. QSARs were then developed using the genetic function approximation algorithm to predict toxic activity both in single PAH congeners and in binary mixtures. Effective concentrations inhibiting 50% of the cell populations were modeled, with R(2) = 0.90, 0.99, and 0.84, respectively. The QSAR mixture algorithms were then adjusted to account for the observed mixture interactions as well as the mixture composition (ratios) to assess the feasibility of QSARs for mixtures. Based on these results, toxic addition is improbable and therefore environmental PAH mixtures are likely to see nonadditive responses when complex interactions occur between components. Furthermore, QSAR may be a useful tool to help bridge these data gaps surrounding the assessment of human health risks that are associated with PAH exposures.

Bioavailability of Polycyclic Aromatic Hydrocarbons and their Potential Application in Eco-risk Assessment and Source Apportionment in Urban River Sediment

Traditional risk assessment and source apportionment of sediments based on bulk polycyclic aromatic hydrocarbons (PAHs) can introduce biases due to unknown aging effects in various sediments. We used a mild solvent (hydroxypropyl-β-cyclodextrin) to extract the bioavailable fraction of PAHs (a-PAHs) from sediment samples collected in Pearl River, southern China. We investigated the potential application of this technique for ecological risk assessments and source apportionment. We found that the distribution of PAHs was associated with human activities and that the a-PAHs accounted for a wide range (4.7%-21.2%) of total-PAHs (t-PAHs), and high risk sites were associated with lower t-PAHs but higher a-PAHs. The correlation between a-PAHs and the sediment toxicity assessed using tubificid worms (r = -0.654, P = 0.021) was greater than that from t-PAH-based risk assessment (r = -0.230, P = 0.472). Moreover, the insignificant correlation between a-PAH content and mPEC-Q of low molecular weight PAHs implied the potential bias of t-PAH-based risk assessment. The source apportionment from mild extracted fractions was consistent across different indicators and was in accordance with typical pollution sources. Our results suggested that mild extraction-based approaches reduce the potential error from aging effects because the mild extracted PAHs provide a more direct indicator of bioavailability and fresher fractions in sediments.

Identifications and seasonal variations of sources of polycyclic aromatic hydrocarbons (PAHs) in the Yangtze River Estuary, China

In this study, positive matrix factorization models (PMFx) were used to analyze the sources of sedimentary PAHs in Yangtze River Estuary (YRE) using 120 data samples from 30 sites collected over four seasons. Three sources were defined for the PAHs: coal and gasoline combustion was the dominant source, accounting for approximately 50%; coke plant emissions and wood or grass combustion each contributed approximately 25%. The coal tar origin was the major source in summer; wood or grass combustion dominated in autumn; coal combustion was the primary source of PAHs in spring and winter. More than 90% of the coke plant emissions were from summer, while pollutants from wood or grass combustion were discharged primarily in autumn. These three sources distributed in different primary regions, the spatial patterns of coal combustion presented an increasing trend in the seaward direction.

Distribution and source apportionment of polycyclic aromatic hydrocarbons in surface sediments from Zhoushan Archipelago and Xiangshan Harbor, East China Sea

Zhoushan Archipelago and the adjacent Xiangshan Harbor are important commercial, tourism, fishing, and mariculture areas. Considering the concern on the effects of anthropogenic activities on the environment, the level and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in surface sediments were investigated. The sum of 16 PAH (∑16 PAH) concentrations in the Zhoushan Archipelago ranged from 3.67 to 31.30 ng g(-1) d.w., with a mean of 15.01 ± 1.21 ng g(-1) d.w., and that in Xiangshan Harbor varied from 11.58 to 481.44 ng g(-1) d.w., with a mean of 62.52 ± 32.85 ng g(-1) d.w. Diagnostic ratios and factor analysis were performed to identify PAH sources. Results show that PAHs have mixed origins (i.e., traffic-related sources, coal combustion, petrogenic sources, and biomass burning), with pyrolytic-related pollution as the dominant source. This study provided a baseline to promote environmental protection and pollution episode monitoring in the East China Sea.

Source apportionment of PAHs in surface sediments using positive matrix factorization combined with GIS for the estuarine area of the Yangtze River, China

This study used PMF and geostatistics to quantify sources of PAHs based on 30 samples tested for 16 PAHs in surface sediment from the Yangtze River Estuary (YRE) in February 2011. The results demonstrated that the total PAH concentrations varied from 65.07 to 954.52 ng g(-1) with a mean value of 224.00 ng g(-1). In the inner estuary, the mean of the total PAH concentrations was 229.89 ng g(-1), and the high molecular weight of four-to-six-ring PAHs accounted for 51.83% of PAHs. In the adjacent East Sea, the mean value was 218.85 ng g(-1) and the high molecular weight PAHs accounted for approximately 54% of total PAHs. A three-factor modeling result from PMF provided the most satisfactory analysis of PAH sources. Coke plant emissions and biomass combustion, which contributed 45.64% of the pollution, were the most important sources, and pollutants from these sources were primarily concentrated in the southern branch of the estuary. Gasoline fuel combustion accounted for approximately 40% of the pollution, and the major contaminated area was in the northern region. Petrogenic sources (14.70%) also influenced the estuary, especially in the northeastern region. Water currents and source locations affected the impacted regions of PMF factors; the surrounding natural and artificial influences were also considered.

Characterization and risk assessment of PAH-contaminated river sediment by using advanced multivariate methods

This study applied advanced multivariate methods and risk assessment to evaluate the characteristics of polycyclic aromatic hydrocarbons (PAHs) in the sediment of the severely polluted Erjen River in Taiwan. High-molecular-weight PAHs (HPAHs) dominated in the rainy season. The ecological risk of PAHs in the sediment was low, whereas the total health risk through ingestion and dermal contact was considerably high. The SOM (self-organizing map) analysis clustered the datasets of PAH-contaminated sediment into five groups with similar concentration levels. Factor analysis identified major factors, namely coal combustion, traffic, petrogenic, and petrochemical industry factors, accounting for 88.67% of the variance in the original datasets. The major tributary and the downstream of the river were identified as PAH-contamination hotspots. The PMF (positive matrix factorization) was combined with toxicity assessment to estimate the possible apportionment of sources and the associated toxicity. Spills of petroleum-related products, vehicle exhaust, coal combustion, and exhaust from a petrochemical industry complex constituted respectively 12%, 6%, 74%, and 86% of PAHs in the sediment, but contributed respectively 7%, 15%, 22%, and 56% of toxicity posed by PAHs in the sediment. To improve the sediment quality, best management practices should be adopted to eliminate nonpoint sources of PAHs flushed by storm water into the major tributary and the downstream of the Erjen River. The proposed methodologies and results provide useful information on remediating river PAH-contaminated sediment and may be applicable to other basins with similar properties that are experiencing resembled river environmental issues.

Source apportionment and risk assessment of emerging contaminants: an approach of pharmaco-signature in water systems

This paper presents a methodology based on multivariate data analysis for characterizing potential source contributions of emerging contaminants (ECs) detected in 26 river water samples across multi-scape regions during dry and wet seasons. Based on this methodology, we unveil an approach toward potential source contributions of ECs, a concept we refer to as the "Pharmaco-signature." Exploratory analysis of data points has been carried out by unsupervised pattern recognition (hierarchical cluster analysis, HCA) and receptor model (principal component analysis-multiple linear regression, PCA-MLR) in an attempt to demonstrate significant source contributions of ECs in different land-use zone. Robust cluster solutions grouped the database according to different EC profiles. PCA-MLR identified that 58.9% of the mean summed ECs were contributed by domestic impact, 9.7% by antibiotics application, and 31.4% by drug abuse. Diclofenac, ibuprofen, codeine, ampicillin, tetracycline, and erythromycin-H2O have significant pollution risk quotients (RQ>1), indicating potentially high risk to aquatic organisms in Taiwan.

Application of positive matrix factorization to source apportionment of surface water quality of the Daliao River basin, northeast China

Surface water monitoring networks play an important role in the stream water quality management. Since a time series of data is obtained from the monitoring network, multivariate statistical techniques can be used to identify important factors or pollution sources of water system. Positive matrix factorization (PMF) is an improved factor analysis tool that has had limited application to water systems. The objective was to apply PMF to monitoring data to apportion water pollution sources in the Daliao River (DLR) basin. The DLR basin includes the Hun and Taizi River catchments in northeast China. This basin is densely populated and heavily industrialized. Fourteen monitoring stations located on the two rivers were used for monitoring 13 physical and chemical parameters from 1990 to 2002. Results show that five sources/processes in the Hun River and four in the Taizi River were identified by marker species and spatial-temporal variations of resolved factors, including point and nonpoint sources for both rivers. In addition, the industrial pollution source emission inventory data were used to compare with the resolved industrial sources. Results reveal that chemical transformations have influenced some chemical species. However, this influence is small compared with observed seasonal variations. Therefore, identification of pollution point and nonpoint sources by their seasonal variations is possible, which will also aid in water quality management. The spatial variation of the industrial pollutants typically corresponded with the urban industrial pollution source inventories.

Toxic effects upon exposure to benzo[a]pyrene in juvenile white shrimp Litopenaeus vannamei

The purpose of this study was to investigate the toxic effects induced by benzo[a]pyrene (BaP). In the present study, juvenile white shrimp Litopenaeus vannamei were exposed to BaP for 21 days at four different concentrations as 0, 0.03, 0.3 and 3μg/L. Detoxification system parameters, transcription of metabolism-related genes, and damage indexes were investigated for screening. It showed mRNA expression levels of superoxide dismutase (SOD), cytochrome P450 (CYP) 1A1 and glutathione-S-transferase (GST) in hepatopancreas were significantly induced at day 3 by 0.3 and 3μg/L BaP, and returned to the initial level afterwards. 7-Ethoxyresorufin O-deethylase (EROD), GST and SOD activities in gill and hepatopancreas were also induced by 0.3 and 3μg/L BaP, while T-AOC and GSH contents were reduced after BaP exposure. The study also showed that 0.3 and 3μg/L BaP caused damage effects, while 0.03μg/L BaP treatment did not exhibit any damage effects. Moreover, according to the correlation analysis results, we conclude that EROD activity, GST activity and GSH content in hepatopancreas can be used as defense biomarkers; DNA strand breaks, lipid peroxidation (LPO) level and protein carbonyl (PC) content in gill and hepatopancreas can be used as damage biomarkers; EROD activity, GST activity, GSH contents and damage effects of DNA strand breaks, LPO level and PC content in hepatopancreas can be used as combined biomarkers. These results will provide information not only on potential biomarkers that could be effectively applied to biomonitor aquatic environment to contamination, but also provide information on toxic effects of this specie.

Source characterization of polycyclic aromatic hydrocarbons by using their molecular indices: an overview of possibilities

In recent decades. an exponential increase in the concentration of anthropogenic Polycyclic Aromatic Hydrocarbons (PAHs; see Table I for a li st of PAH abbreviations) has been observed worldwide. Regulators need to know the sources if concentrations are to be reduced and appropriate remediation measures taken. "Source characterization of PAHs" involves linking these contaminants to their sources. Scientists place PAH sources into three classes: pyrogenic, petrogenic. and natural. In this review. we investigate the possibility of using PAH molecular ratios individually or in combination for the purpose of deducing the petrogenic or pyrogenic origin of the contamination in sediments. We do this by reviewing the characteristic PAH patterns of the sources and by taking into account the fate of PAHs in the aquatic environment. Many PAH indicators have been developed for the purpose of discriminating different PAH sources. In Table 4 we summarize the applicability of different PAH ratios and threshold values. The analysis of two- to four-ringed alkylated PAH soilers the possibility to distinguish two or more single sources or categories of pollution in greater detail. For example. the FLO/PYO. the PPI. and PO/AO ratios can be used to discriminate between pyrogenic and petrogcnic sources of contamination. When petrogenic contamination is suspected. chrysenes. PAHs lighter than CO. and in particular. alkylated PAHs can usually be of use. For unburned coal PAHs. The methylphenanthrenic ratios (MP!s). the 1-D I/4- DI. and BbF/BkF are promising, since they are sometimes correlated with vitrinite rellectance (coal ranks). Alkylphenanthrenes can be used to detect biomass combustion. Higher molecular weight parent and alkylated PAHs are appropriate for pyrogenic discriminations. When PAH indices are coupled with discriminant analysis techniques such as PMF (positive matrix factorization),the origin of multiple sources in even the most complex environments can be traced and measured. Even so. the most stable isomer pairs degrade differentially. depending on their thermodynamic stability, the environmental conditions, and the type of degradation. If PAH ratios are to be used, it is usually necessary to have pri or knowledge of the degradation state of the matrices examined (air, sediment, etc.) and of how the PAH ratio behaves under such conditions. PAH ind ices (e.g ., NO/CO or LPAH/HPAH ) can be app lied for distinguishing differential degradation gradients (photodegradation, biodegradation, etc.). Degradation does not significantly affect the ratio of parent to alkylated PAHs and the PI. The degradation arrow in Table 4 and Figs. 9. I 0. II . 12. 13, 14. 15. 17. 18. 19, 20, 2 1, 22. 23. and 24 shows how the ratio usually changes with degradation. Merely detecting the six PAHs of Borneff6 is not enough to establish petrogenic contamination, because Borneff6 includes main ly HMW PAHs. The LPAH 16 appears to be the most suitable for identify ing pyrogenic and petrogenic sources. For more specific information on sources and their discrimination it is recommended to further take into account important parent PAHs such as NO. BeP. PER. DO. and-most importantly- alkylatcd PAHs.

Polycyclic aromatic hydrocarbons in sediments from the Old Yellow River Estuary, China: occurrence, sources, characterization and correlation with the relocation history of the Yellow River

The levels of 16 USEPA priority PAHs were determined in surface sediments and one dated sediment core from the abandoned Old Yellow River Estuary, China. Total PAH concentrations in the surface sediments ranged from 100.4 to 197.3 ng g(-1) dry weight and the total toxic equivalent quantity (TEQ(carc)) values of the carcinogenic PAHs were very low. An evaluation of PAH sources based on diagnostic ratios and principal component analysis suggested that PAHs in the surface sediments mainly derived from combustion sources. The total PAH concentrations altered significantly with year of deposition and showed quite different patterns of change compared with other studies: it is hypothesized that the principal cause of these changes is the relocation of the course of the Yellow River to the sea in 1976 and 1996.

Source apportionment for sediment PAHs using hybrid genetic pattern search treatment of a chemical mass balance receptor model: application to the Pearl River Delta region, China

In order to solve the collinear problem and improve the estimation accuracy of the chemical mass balance (CMB) model which can be essentially regarded as a constrained optimization process, in this study, a hybrid genetic pattern search algorithm (HGPS) was proposed and applied to apportion the source contributions for sediment polycyclic aromatic hydrocarbons (PAHs) in the Pearl River Delta (PRD) region, China. Simulation results with developed synthetic datasets indicated that the estimated source contributions by HGPS were more close to the true values than CMB8.2. Utilizing the HGPS-CMB, residential coal and traffic tunnel were apportioned as the major sources of sediment PAHs in the PRD region. For freshwater surface sediments, the average contribution from residential coal ranged from 32 to 55%, and traffic tunnel ranged from 13 to 33%, while the major sources for marine sediments were traffic tunnel (10 ~ 56%). These results provide information for developing better PAH pollution control strategies for the PRD.

Source contributions and spatiotemporal characteristics of PAHs in sediments: Using three-way source apportionment approach

Polycyclic aromatic hydrocarbon (PAHs) were measured in sediments from 29 sites throughout Taihu Lake in China during 2 seasons to investigate spatiotemporal characteristics and source contributions using a 3-way source apportionment approach to positive matrix factorization (PMF3). Seasonal and spatial variations of levels and toxicity suggested higher individual carcinogenic PAH concentrations and toxic equivalent quantity (TEQ) in the flooding season. Three-way PAHs dataset (PAH species, spatial variability, and seasonal variability) was analyzed by PMF3, and its results were compared with a widely used 2-way model (PMF2). Consistent results were observed: vehicular emission was the most important contributor (67.08% by PMF2 and 61.83% by PMF3 for the flooding season; 54.21% by PMF2 and 52.94% by PMF3 for dry season), followed by coal combustion and wood combustion in both seasons. The PMF-cluster analysis was employed to investigate spatial variability of source contributions. Findings can introduce the 3-way approach to apportion sources of PAHs and other persistent organic pollutants (POPs) in sediments, offering the advantage of accounting for information on 3-way datasets.

Parsing pyrogenic polycyclic aromatic hydrocarbons: forensic chemistry, receptor models, and source control policy

A realistic understanding of contaminant sources is required to set appropriate control policy. Forensic chemical methods can be powerful tools in source characterization and identification, but they require a multiple-lines-of-evidence approach. Atmospheric receptor models, such as the US Environmental Protection Agency (USEPA)'s chemical mass balance (CMB), are increasingly being used to evaluate sources of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in sediments. This paper describes the assumptions underlying receptor models and discusses challenges in complying with these assumptions in practice. Given the variability within, and the similarity among, pyrogenic PAH source types, model outputs are sensitive to specific inputs, and parsing among some source types may not be possible. Although still useful for identifying potential sources, the technical specialist applying these methods must describe both the results and their inherent uncertainties in a way that is understandable to nontechnical policy makers. The authors present an example case study concerning an investigation of a class of parking-lot sealers as a significant source of PAHs in urban sediment. Principal component analysis is used to evaluate published CMB model inputs and outputs. Targeted analyses of 2 areas where bans have been implemented are included. The results do not support the claim that parking-lot sealers are a significant source of PAHs in urban sediments.

Accurate analysis of polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs homologs in crude oil for improving the gas chromatography/mass spectrometry performance

The common gas chromatography/mass spectrometry (GC/MS) approaches such as selective ion monitoring (SIM) or single ion extraction (SIE) from full scan data produce the error (over- or underestimation) estimates for the high level alkylated polycyclic aromatic hydrocarbons (PAHs). In order to rectify the error, the alkylated PAHs in the crude oil samples are quantified by deeply investigating the existing full scan data of 1D GC/MS, instead of resuming with the complex and inaccessible equipments (multidimensional gas chromatography or mass spectrometry). The aim of this study is to provide the detailed qualitative and quantitative basis data (confirming ions, relative abundance, retention indices, and area counts) of the high level alkylated PAHs by a comprehensive three-step method: (1) the potential confirming ions per isomer are selected by exploring the multiple fragment patterns formation mechanism; (2) the reasonable confirming ions are estimated by comparing extracted ion chromatography (EIC) of the potential confirming ions; (3) after deconvolution, composite chromatograms of the reasonable confirming ions illustrate the basis data by assigning peaks for target PAHs definitively. The validation data, resulting concentrations and diagnostic ratios for each homolog are compared with those obtained from SIM. The experimental data demonstrate that significant inaccurate identifications and concentration estimates are obtained when SIM mode is used for C4 Naphthalene (C4 N), C3 Phenanthrene (C3 P), C4 Phenanthrene (C4 P), C3 Dibenzothiophene (C3 D), C3 Fluorene (C3 F), C2-4 Chrysene (C2-4 C) and C1 Fluoranthene (C1 Flt). This study evaluates the usefulness of the previous fragmentation patterns, and confirms compound presence by GC/MS using the different spectral deconvolution software. This approach is developed as a broad screen for environmental samples (including petrol, diesel fuel and coal tar), with only the crude oil results being presented here.

Historical records of organic pollutants in sediment cores

Analyses of sediment core samples are primary sources of historical pollution trends in aquatic systems. Determining organic compounds, such as POPs, in the dated sediments enables the estimation of their temporal concentration changes and the identification of the contaminant origin in local regions. Wars, large-scale fires, economical transitions, and bans on certain chemicals are reflected in the sediment organic compound concentrations. The high POP concentrations in surficial sediments suggest that these chemicals, even after being banned, remain in the environment. Furthermore, vertical profiles can help in understanding the sedimentation process and in estimating effective countermeasures against pollution. Moreover, studies published during the period 1991-2013 on PAHs, PCBs, OCPs, dioxins and dioxin-like compound concentrations in sediment core samples are reviewed.

Source apportionment of polycyclic aromatic hydrocarbons in sediments from polluted rivers

Over the past few decades, in response to growing concerns about the impact of polycyclic aromatic hydrocarbons (PAHs) on human health, a variety of environmental forensics and geochemical techniques have emerged for studying organic pollutants. These techniques include chemical fingerprinting, receptor modeling, and compound-specific stable isotope analysis (CSIA). Chemical fingerprinting methodology involves the use of diagnostic ratios. Receptor modeling techniques include the chemical mass balance (CMB) model and multivariate statistics. Multivariate techniques include factor analysis with multiple linear regression (FA/MLR), positive matrix factorization (PMF), and UNMIX. This article reviews applications of chemical fingerprinting, receptor modeling, and CSIA; comments on their uses; and contrasts the strengths and weaknesses of each methodology.

Performance evaluation of polycyclic aromatic hydrocarbons analysis in sediment from proficiency testing with metrological reference values

This paper describes a metrological approach to evaluate the measurement capability of laboratories participating in two proficiency testing (PT) programmes involving the analysis of five polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Reference values of PAHs in the programmes for performance assessment were obtained from an accurate isotope dilution gas chromatography mass spectrometry (ID-GCMS) method which was thoroughly validated and verified. Isotope dilution mass spectrometry (IDMS) technique usually has a well-defined measurement uncertainty budget and a traceability link to an International System of Units. Provision of the metrological reference values in PT enables the establishment of a technical platform to assess the actual competence of the participating laboratories in sediment PAHs analysis. Results of the PT programmes showed that about 80 % of the laboratories employed gas chromatography in their analyses and the remaining used liquid chromatography. Irrespective of the techniques being used, however, the majority of the participating laboratories were observed to underestimate values in which the mean values of the five reported PAHs were less than those of the ID-GCMS-derived reference values by 13-20 %. Only 41-44 % of the participating laboratories were able to achieve satisfactory z-scores. The present study revealed that the reinforcement of the capability for accurate measurement of PAHs in sediment samples in laboratories worldwide should be addressed.

Application of fingerprint-based multivariate statistical analyses in source characterization and tracking of contaminated sediment migration in surface water

This study investigates the suitability of multivariate techniques, including principal component analysis and discriminant function analysis, for analysing polycyclic aromatic hydrocarbon and heavy metal-contaminated aquatic sediment data. We show that multivariate "fingerprint" analysis of relative abundances of contaminants can characterize a contamination source and distinguish contaminated sediments of interest from background contamination. Thereafter, analysis of the unstandardized concentrations among samples contaminated from the same source can identify migration pathways within a study area that is hydraulically complex and has a long contamination history, without reliance on complex hydrodynamic data and modelling techniques. Together, these methods provide an effective tool for drinking water source monitoring and protection.

Relationships between PAHs and PCBs, and quantitative source apportionment of PAHs toxicity in sediments from Fenhe reservoir and watershed

Sedimentary samples from 28 sites throughout the Fenhe reservoir and upstream watershed in China were measured, to study the relationships between PAHs and PCBs as well as perform quantitative source apportionment of toxicity. The distributions of ∑16PAHs and ∑123PCBs showed high correlation. The ∑7C-PAHs (total concentrations of seven carcinogenic PAHs) varied from 87.7 to 2005.0ngg(-1)dw, and the ∑6DL-PCBs (total concentrations of six dioxin-like PCB congeners) were n.d.-5.96ngg(-1)dw. Toxicity and biological risk were assessed using toxic equivalent quantity (TEQ) and sediment quality guideline quotient (SQGQ). The BaP played the dominant role for TEQPAH at most sites (37.17-89.40%), although the CHR showed the highest concentration level. PCB-81 contributed the highest TEQPCB. High correlations were observed between ∑16PAHs and ∑7C-PAHs, ∑123PCBs and ∑6DL-PCBs, ∑7C-PAHs and ∑6DL-PCBs as well as TEQPAH and TEQPCB. Furthermore, quantitative source apportionments for PAHs concentrations and TEQ were carried out, combining the positive matrix factorization (PMF) with the formula of TEQ. For most sites, the vehicular sources were the largest contributors to TEQPAH (46.58%), while coal combustion sources were the highest contributor for PAHs concentrations (43.31%). The relatively higher correlations between PCBs and contributions of coal combustion to PAHs might imply the similar distribution of industrial sources for PAHs and PCBs.

Source apportionment of trace element pollution in surface sediments using positive matrix factorization combined support vector machines: application to the Jinjiang River, China

In this study, a method of positive matrix factorization (PMF) combined support vector machines (SVMs) was adopted to identify possible sources and apportion contributions for trace element pollution in surface sediments from the Jinjiang River, Southeastern China. Utilizing diagnostics tools, four significant factors were extracted from sediment samplers, which were collected in December 2010 at 15 different sites. By treating source identification as a pattern recognition problem, the factor loadings derived from PMF were classified by SVM classifiers which have been trained and validated with fingerprints of eight potential source categories. Using SVM, industrial wastewater from lead ore mining and metal handcraft manufacture, atmospheric deposition, and natural background were identified as main sources of trace element pollution in surface sediments from the Jinjiang River, which were affirmed by visually comparing compound patterns and the differences between the predicted and actual fractional compositions. Apportionment results showed that source of lead ore mining made the largest contribution (33.62 %), followed by atmospheric deposition (30.99 %), metal handcraft manufacture (30.09 %), and natural background (5.29 %).

Source apportionment of polycyclic aromatic hydrocarbons in surface sediments of the Bohai Sea, China

A total of 112 surface sediment samples covering virtually the entire Bohai Sea were analyzed for polycyclic aromatic hydrocarbons (PAHs), in order to provide the extensive information of recent occurrence levels, distribution, possible sources, and potential biological risk of these compounds in this area. Surface sediment samples were collected from the Bohai Sea using a stainless steel grab sampler. Sixteen PAHs were determined by a Finnigan TRACE DSQ gas chromatography/mass spectrometry. Diagnostic ratios, cluster analysis, and principal component analysis (PCA) with multivariate linear regression (MLR) were performed to identify and quantitatively apportion the major sources of sedimentary PAHs in the Bohai Sea. Concentrations of total PAHs in the Bohai Sea ranged widely from 97.2 to 300.7 ng/g (mean, 175.7 ± 37.3 ng/g). High concentrations of PAHs were found in the vicinity of Luan River Estuary-Qinhuangdao Harbor, Cao River Estuary-Bohai Sea Center, and north of the Yellow River Estuary. The three-ring PAHs were most abundant, accounting for about 37 ± 5 % of total PAHs. The four-ring and five-ring PAHs were the next dominant ones comprising approximately 29 ± 7 and 23 ± 3 % of total PAHs, respectively. Concentrations of acenaphthylene, acenaphthene, and dibenz[a,h]anthracene are higher than Canadian interim marine sediment quality guideline values at most of the sites in the study area. Contamination levels of PAHs in the Bohai Sea were low in comparison with other coastal sediments in China and developed countries. The distribution pattern of PAHs and source identification implied that PAH contamination in the Bohai Sea mainly originates from petrogenic and pyrogenic sources. Further PCA/MLR analysis suggested that the contributions of spilled oil products (petrogenic), coal combustion, and traffic-related pollution were 39, 38, and 23 %, respectively. Pyrogenic sources (coal combustion and traffic-related pollution) contributed 61 % of anthropogenic PAHs to sediments, which indicates that energy consumption could be a dominant factor in PAH pollution in this area. Acenaphthylene, acenaphthene, and dibenz[a,h]anthracene are the three main species of PAHs with more ecotoxicological concern in the Bohai Sea.