High Polycyclic Aromatic Hydrocarbons Research Articles

The effect of ethanol and iso-butanol blends on polycyclic aromatic hydrocarbon (PAH) emissions from PFI and GDI vehicles

This study assessed particulate emissions characteristics from two flexible fuel vehicles (FFVs) equipped with port fuel injection (PFI) and gasoline direct injection (GDI) engines. Emissions testing was conducted over the Federal Test Procedure on E10, E51, and E83, and an iso-butanol blend (iBut55). The results showed significantly higher particulate matter (PM) emissions for the GDI-FFV compared to those of the PFI-FFV. The addition of alcohol blends resulted in PM reductions for the GDI-FFV, while PM emissions gradually increased with higher alcohol blending for the PFI-FFV. Elemental carbon (EC) emissions dominated the PM composition for the GDI-FFV, whereas the organic carbon (OC) fraction was higher for the PFI-FFV. The most prominent polycyclic aromatic hydrocarbons (PAHs) in the vapor-phase were the two- and three-ring aromatic compounds, followed by the middle molecular weight PAHs (four-ring compounds). For the particle-phase PAHs, the middle- and high molecular weight PAHs were the most abundant compounds, especially for the GDI-FFV. Overall, the GDI-FFV exhibited markedly higher PAH emissions compared to the PFI-FFV. Both vapor- and particle-phase PAH emissions showed reductions with higher ethanol and iso-butanol fueling for both vehicles, except for the PFI-FFV, where particle-phase PAHs increased and trended similarly with the PM mass and OC for this vehicle. Alcohol blending reduced the carcinogenic potential of the exhaust emissions for both vehicles. The GDI exhaust showed significantly higher metal emissions than the PFI-FFV. The use of higher alcohol blends led to reductions in metal emissions, including redox-active transition metals and other metals originating from the lubricant oil.

Pollution status and human health risk assessment of potentially toxic elements and polycyclic aromatic hydrocarbons in urban street dust of Tyumen city, Russia.

This study investigated levels and sources of pollution and potential health risks associated with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in urban street dust collected from Tyumen city, a large transport centre with one of the highest motorization rates in Russia. Twenty street dust samples were collected from four grades of roads in five different land use areas. Research methods included measurements of physical and chemical properties of street dust, concentrations of 18 PTEs using inductively coupled plasma mass spectrometry, 12 PAHs using high-performance liquid chromatography, and statistical analysis of the data. Concentrations of Ni, Cr, Sb, and Mo, as well as medium and high molecular weight PAHs in urban street dust, were notably higher than in soils within the city, which indicates that transport is the main source of these elements. Concentrations of Cu, Cd, Pb, Zn, Mn, and As in street dust of Tyumen were lower compared to many large cities, while Cr, Ni, and Co were higher. Concentrations of PAH were comparable to other large nonindustrial cities. Total contamination of street dust by both PTEs and PAHs showed more robust relationships with the number of roadway lanes rather than land use. The estimated carcinogenic risks were low in 70% of samples and medium in 30% of samples. Noncarcinogenic risks were attributed to exposure to Co, Ni, V, and As. The total noncarcinogenic risk for adults was found to be negligible, while the risk was found to be moderate for children.

Benzo[a]pyrene sourcing and abundance in a coal region in transition reveals historical pollution, rendering soil screening levels impractical

Benzo[a]pyrene (BaP) is a hazardous compound for human health and for environmental compartments. Its transfer and deposition through the atmosphere affects soil quality. In this context, we quantified the content of BaP and other Polycyclic Aromatic Hydrocarbons (PAHs) in the soils of a prominent Coal Region in Transition to test whether the soil screening levels in force are realistic and whether they reflect the complexity of regions closely linked to heavy industries and mining. In this regard, soil screening levels are thresholds often established without considering historical anthropogenic activities that affect soil (diffuse pollution). The 150 soil samples studied showed a notable content of high molecular weight PAHs, and BaP surpassed the threshold levels in practically the entire area. PAH-parent diagrams revealed a relatively homogenous fingerprint of four clusters obtained in a multivariate statistical study. In addition, molecular diagnostic ratios pointed to coal combustion as the main pollution source, whereas only some outliers appeared to be related to specific spills. A BaP threshold was calculated to be 0.24 mg kg−1, over 10 times the limit established in Spain. Finally, a factor analysis revealed a positive correlation of BaP with elements usually emitted in coal combustion processes, such as Tl and V. This observation fosters the hypothesis of a historical and indelible pollution fingerprint in soils whose sources, characteristics and potential environmental and health concerns deserve further attention. All things considered, caution should be taken when using soil screening levels in regions associated with coal exploitation and heavy industry.

Response of soil bacterial communities to polycyclic aromatic hydrocarbons during the phyto-microbial remediation of a contaminated soil

Rhizo-box experiments were conducted to analyze the phyto-microbial remediation potential of a grass (Lolium multiflorum L.) and a crop (Glycine max L.) combined with exogenous strain (Pseudomonas sp.) for polycyclic aromatic hydrocarbons (PAHs) contaminated soils. The dynamics of bacterial community composition, abundances of 16 S rDNA and ring hydroxylating dioxygenases (RHDα) genes, and removal of PAHs were evaluated and compared on four culture stages (days 0, 10, 20, and 30). The results showed that 8.65%–47.42% of Σ12 PAHs were removed after 30 days of cultivation. Quantitative polymerase chain reaction (qPCR) analysis indicated that treatments with soybean and ryegrass rhizosphere markedly increased the abundances of total bacteria and PAH-degraders, especially facilitated the growth of gram-negative degrading bacteria. Flavobacterium sp. and Pseudomonas sp. were the main and active strains in the control soil. However, the presence of plants and/or exogenous Pseudomonas sp. changed the soil bacterial community structure and modified the bacterial diversity of PAH-degraders. On the whole, this study showed that the high molecular weight PAHs removal efficiency of phyto-microbial remediation with ryegrass was better than those of remediation with soybean. Furthermore, the removals of PAHs strongly coincided with the abundance of PAH-degraders and bacterial community structure.

A Survey of Concentrations and Source Characterization of Polycyclic Aromatic Hydrocarbons in Surface Waters of the Imiringi River System

Ten water samples were collected along the Imiringi water channel, cutting across several sub-communities of the upstream to downstream sections of the river. All samples were collected in the month of August 2019, reflecting increased tidal movement of water and aggravated pollutants redistribution which is typical of the rainy season. Analysis was carried out using the HP 6890 Plus gas chromatograph – flame ionization detector (GC-FID). The rate of ionization of each PAH component was directly proportional to the obtained concentration. The total concentrations of 14 PAHs ranged from <0.01 to 300.1 µgL-1, with the high molecular mass PAHs (4-6 ring HPAHs) observed as the most important fractions showing 82.4% distribution. Also, the low molecular mass PAHs (2-3 ring LPAHs) were found in trace concentrations, accounting for 17.6% of total PAH mass. The application of PAH source diagnostic ratios revealed vegetation and coal combustion as primary sources, followed by petroleum combustion, and then, petroleum sources. Correlation cluster analysis (CCA) and principal component analysis (PCA) showed discrete localization for samples of stations OL1, OB2 and OS4. The pyrogenic inputs are most likely from runoffs of seasonally burnt vegetation at near-coastal farmlands as well as leachates from surrounding waste-dumpsites. Petroleum sources may have resulted from neighbouring oil installations and illegal oil bunkering sites. Overall, the study is aimed at identifying the most important contributing sources of polycyclic aromatic hydrocarbon (PAH) micro-pollutants in the aquatic environment.

Seasonal characteristic composition of inorganic elements and polycyclic aromatic hydrocarbons in atmospheric fine particulate matter and bronchoalveolar lavage fluid of COPD patients in Northeast China

ObjectiveTo explore the composition characteristics of atmospheric fine particulate matter (PM2.5) and bronchoalveolar lavage fluid (BALF), and their impact on the development of chronic obstructive pulmonary disease (COPD). MethodsThe atmospheric PM2.5 samples and BALF samples from COPD patients were collected from June 2, 2017 to October 30, 2018, and allocated into a high-risk of PM2.5 inhalation group and a low-risk PM2.5 inhalation group according to the heating season in Harbin. Inorganic elements were detected by ICP-MS, and polycyclic aromatic hydrocarbons (PAHs) were detected by GC/MS. ResultsTwenty-six inorganic elements were found in 54 BALF specimens. There was a high correspondence in inorganic elements between BALF and atmospheric PM2.5. Trace elements Cr, Mn, V, and Co, and toxic trace elements Al, Pb, Cd, As, and Ag were above the upper limit of normal blood. There were significant higher K, Ti, Fe, Co, Cu, Se, Rb, Ag, and Sb in BALF of the high-risk PM2.5 inhalation group (p < 0.05). Sixteen PAHs were detected in 32 BALF samples. The main components of BALF and atmospheric PM2.5 were the high molecular weight PAHs, and the species and concentration of PAHs in BALF and atmospheric PM2.5 are highly consistent. ConclusionThe types and concentrations of inorganic elements and PAHs in BALF of COPD patients are highly consistent with those of atmospheric PM2.5. The sustained high concentrations of Benzo(a)anthracene, Chrysene, Benzo(b)Fluoranthene, Benzo(k)Fluoranthene, Indeno(123-c,d)Pyrene, and Benzo(a)Pyrene in BALF of COPD patients may have long-term adverse effects on COPD patients.

Abundance and sources of benzo[a]pyrene and other PAHs in ambient air in Hong Kong: A review of 20-year measurements (1997–2016)

The polycyclic aromatic hydrocarbon (PAH) family is of environmental concern due to its toxicity, prompting the need of monitoring their long-term trends. Three monitoring programs in Hong Kong report concentrations of ambient PAHs, namely (1) respirable suspending particle (RSP) speciation program that monitored benzo[a]pyrene (BaP) (1997 to March 2000), (2) total suspended particle speciation program that monitored BaP (1997–1999), and (3) toxic air pollutant monitoring program that monitors BaP and 16 other PAHs in the combined gas and particulate phases at two general urban stations once or twice a month since January 1998. In this work, we review all the available PAH measurements in Hong Kong during 1997–2016, with emphasis on the temporal trends of BaP and the other 16 PAHs. PAHs of 5–6 rings exhibit an ambiguous decline trend since 1998, with a negative Sen’s slope that is statistically significant. Specifically, BaP was reduced by 78% from 1998 to 2016, with a Sen’s slope of −0.013 ng m-3 year−1. Correlations of BaP with RSP major species of high source specificity and PAH diagnostic ratios are employed to explore the source origins of PAHs. Our analysis reveals that PAHs mainly come from a combination of vehicular emissions and biomass/coal combustion. The decline trend of PAHs is further found in consistence with the declined particulate matter emissions from vehicular exhaust and biomass/coal combustion. This study fills the data vacancy in the long-term trends of ambient PAHs for the Pearl River Delta region, one of the economically more advanced regions in China.

Abstract A01: Environmentally prevalent polycyclic aromatic hydrocarbons elicit cocarcinogenic properties in human and mouse lung cells

Abstract Rationale: Polycyclic aromatic hydrocarbons (PAHs) are prevalent contaminants in our environment, workplace, and in first- and secondhand smoke from both cigarettes and marijuana. The toxicity of low molecular weight (LMW) PAHs compared to high molecular weight PAHs (e.g., benzo[a]pyrene, B[a]P) is not well studied in lung cells. Our overall hypothesis was that LMW PAHs act as cocarcinogens in the presence of a known carcinogen (B[a]P) in human and mouse lung epithelial cells. Gap junctions are commonly suppressed during tumor promotion, while DNA-adduct formation and micronuclei (MN) are observed during the initiation stage of cancer. We used these endpoints together as markers of carcinogenicity in Beas2B and C10 cells. Methods: Beas2B, a human bronchial epithelial cell line, and C10 cells, a nontumorigenic type II alveolar pneumocyte cell line, were used. LMW PAHs (1-methylanthracene, 1-MeA, and fluoranthene, Flthn) were applied in a 1:1 ratio mixture based on previous studies and B[a]P as a classic carcinogen. Cells were treated for 30 min.-24 h with the LMW PAH mixture, B[a]P, or both, and assessed for the following endpoints: cytotoxicity, genotoxicity (MN), apoptosis, proliferation, gap junctional intercellular communication (GJIC) by the lucifer yellow scalpel-loaded/dye-transfer assay, and DNA adducts of B[a]P by HPLC with fluorescence detection in C10 cells. Results: LMW PAHs are more cytotoxic in the human Beas2B cells than the mouse C10 cells. Significant toxicity is observed in Beas2B cells at 0.3 uM B[a]P combined with the LMW PAH mixture (0.1-1 uM), while no toxicity is observed in C10 cells at identical doses. No significant apoptosis was observed in Beas2B cells while significant increases in S-phase were observed in response to B[a]P combined with LMW PAH mixture compared to B[a]P alone. B[a]P in combination with the LMW PAH mixture significantly inhibited GJIC in C10 and Beas2B cells compared to B[a]P or the LMW PAH mixture alone, supporting a role for GJIC suppression in cancer development. B[a]P diol-epoxide (BPDE)-DNA adduct levels were also significantly induced in C10 cells at 1.0 uM B[a]P with the LMW PAH mixture at several doses (less than or equal to 1.0 uM) and significant increases in BPDE-DNA adduct formation compared to B[a]P alone were observed. Lastly, MN were also observed in both cell lines and significantly differed between B[a]P alone and in combination with the LMW PAH mixture. DNA adduct formation and genotoxicity coincided with GJIC inhibition. Conclusion: These studies provide evidence that LMW PAHs in combination with B[a]P can elicit increased carcinogenic potential in human and mouse cells. Support: Flight Attendant Medical Research Institute (CIA130022, AKB); the National Institute for Environmental Health Sciences (R15ES024893, AKB). Citation Format: Alison K. Bauer, Katelyn J. Siegrist, Sabine Plöttner, Thomas Brüning, Heiko U. Käfferlein. Environmentally prevalent polycyclic aromatic hydrocarbons elicit cocarcinogenic properties in human and mouse lung cells [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A01.

Analysis of Polycyclic Aromatic Hydrocarbons in Heregovački pršut-Traditionally Smoked Prosciutto.

Hercegovački pršut as a traditional dry-cured smoked ham (prosciutto) produced by using an open fire that can be potentially contaminated with polycyclic aromatic hydrocarbons (PAHs) and can pose a health risk for consumers. The aim of this research was to identify the types and concentrations of 16 PAHs in 34 samples of traditionally smoked prosciutto. Out of 16 investigated PAHs, identified in the EPA (Environmental Protection Agency) list of priority pollutants, 14 compounds were detected. Average levels of cancerogenic benzo[a]pyrene (BaP) and PAH4 (benzo[a]anthracene (BaA), benzo[b]fluoranthene (BbF), chrysene (Chry), and benzo[a]pyrene (BaP)) ranged from <LOQ (level of quantification) to 5.08 μg/kg and 0.45 μg/kg to 22.67 μg/kg. Two analyzed samples exceeded currently prescribed values according to the Bosnia and Herzegovina legislation for BaP concentrations and one sample for PAH4 content. PAH16 concentrations were on average between 2.92 μg/kg and 87.6 μg/kg. The highest PAH concentrations were found in samples from the Herzegovina-Neretva canton. The results of the research highlight the importance of standardizing smoking procedures and manufacturing practice, in the production of Hercegovački pršut, in order to reduce the PAH content.

The integration of fatty acid biomarkers of trophic ecology with pollutant body-burdens of PAHs and PCBs in four species of fish from Sabine Lake, Texas

This study investigated whether the composition of fatty acids in hepatic tissue of four fish species from Sabine Lake (TX), influenced hepatic body-burdens of pollutants. The multivariate correlations between hepatic body-burdens of sixteen polycyclic aromatic hydrocarbons (PAHs) and twenty-nine polychlorinated biphenyls (PCBs), with thirty-seven fatty acids was studied. The trophic ecology of fish was determined using stomach content analysis and by comparing characteristic fatty acid profiles. The fish species studied included: bull shark (Carcharhinus leucas), alligator gar (Atractosteus spatula), red drum (Sciaenops ocellatus), and gafftopsail catfish (Bagre marinus). Assessment of fish stomach contents demarcated catfish and red drum (mainly invertebrate diet) vs. alligator gars and bull sharks (mainly teleost diet). Elevated levels (45× higher) of nervonic acid (24:1n9) also placed the trophic ecology of catfish and red drum closer to the base of the marine/estuarine food web of Sabine Lake, as compared to alligator gars and bull sharks. PAH profiles showed a predominance of low molecular weight PAHs (≤3 aromatic rings) in catfish, red drum and alligator gars. Bull sharks exhibited the highest levels for select high molecular weight PAHs (≥ 4 aromatic rings). The overall predominance of low molecular weight PAHs indicated exposure to mainly petrogenic sources of PAHs. Bull sharks and alligator gars also exhibited the highest body-burdens of PCBs. The risk assessment of dioxin-like PCBs showed median toxic equivalent (TEQ) values in bull sharks to be the highest, and above the upper toxicity thresholds for adverse effects in fish and aquatic mammals. The multivariate correlational analysis of pollutant body-burdens and fatty acid levels showed no clear correlation of the pollutants with any particular type of fatty acid (unsaturated vs. saturated, short-chain vs. very-long chain). This result indicates that pollutant bioaccumulation was not associative with the specific fatty acid composition of lipids in the fish from Sabine Lake.

The occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in African environments-a systematic review.

In the African continent, several studies have been conducted to determine PAH pollution levels with their associated health risks in the environment. However, these studies are very much disconnected. The objective of this study is to conduct a systematic review that serves as a comprehensive report on the PAH-related studies conducted in the African continent. Data sources are from Google Scholar and PubMed. English language studies that reported on PAH levels in smoked fish and meat, soils and dust, aquatic environments, indoor and outdoor air, and ready-to-eat food items were selected. Specific PAHs included the following: 33 PAHs comprising ofthe 16 USEPA PAHs, non-alkylated PAHs, non-alkylated PAHs, oxygenated PAHs (OPAHs), and azaarenes (AZAs). Study appraisal and synthesis methods: The Newcastle-Ottawa Scale (NOS) was adapted to assess the quality of the selected studies basing on their sampling methods, analytical techniques, and results. A total of 121 studies were reviewed, with the majority (56) being from Nigeria. PAH levels in smoked fish and meat, soils and dust, aquatic environments, indoor and outdoor air, and ready-to-eat food items recorded total concentrations of PAHs ranging from 5 to 3585 μg/kg, BDL to 6,950,000 μg/kg, 0 to 10,469,000 μg/kg, 0 to 7.82 ± 0.85 μg/m3, and 2.5 to 7889 ± 730 μg/kg respectively. Carcinogenic risk assessment for children and adults ranged from very low to very high levels when compared to the ILCR range (10-6 to 10-4) defined by the USEPA. Out of 54 African countries, only 19 were represented. The majority of selected studies failed to apply any standard protocols for sample collection and analysis. The low to very high PAH levels reported in studies calls for effective actions on environmental health. Similar systematic reviews are expected to be performed in other continents for a global assessment of PAH pollution.

Occurrence of heavy metals and polycyclic aromatic hydrocarbons in typical used mineral oil from China: implications for risk management.

Heavy metals and polycyclic aromatic hydrocarbons (PAHs) are the important contaminants in used mineral oil (UMO) and likely pose environmental risks in the processes of disposal and regeneration. However, little information on the concentrations and associated with the risk of heavy metals and PAHs in various types of UMO from different industries is available. In this study, the occurrence of heavy metals and PAHs in the UMOs from typical industries in China was investigated. The median concentrations of 12 metals were 0.1-28mg/kg. PAHs were mainly composed of 2- and 3-ring compounds and the median concentrations of 16 PAHs were 0.03-7.6mg/kg in different UMO. The cluster analysis showed that samples with high heavy metal and PAH concentrations mainly originated from machine manufacturing and vehicle industries. The random forest model suggested that the species and phase of UMO were the main influencing factors associated with heavy metal concentrations, and the relative importance was 71.1-19.9%, 100-30.7%, 42.3-20.7%, 38.0-11.8%, and 100-24.1% for Cu, Zn, Ni, Cr, and Pb models, respectively, while industry was the main influencing factor associated with PAHs in UMO, and the relative importance was 81.5-51.5%, 27.7-16.5%, 83.4-25.3%, 94.8-21.4%, and 53.3-16.1% for 2- to 6-ring models, respectively.

Emerging concerns of VOCs and SVOCs in coking wastewater treatment processes: Distribution profile, emission characteristics, and health risk assessment

In this study, the distribution profiles, emission characteristics, and health risks associated with 43 volatile and semi-volatile organic compounds, including 15 phenols, 18 polycyclic aromatic hydrocarbons (PAHs), 6 BTEX, and 4 other compounds, were determined in the wastewater treatment plant (WWTP) of a coking factory (plant C) and the succeeding final WWTP (central WWTP). Total phenols with a concentration of 361,000 μg L−1 were the predominant compounds in the influent wastewater of plant C, whereas PAHs were the major compounds in the final effluents of both coking WWTPs (84.4 μg L−1 and 30.7 μg L−1, respectively). The biological treatment process in plant C removed the majority of volatile organic pollutants (94.1%–99.9%). A mass balance analysis for plant C showed that biodegradation was the main removal pathway for all the target compounds (56.6%–99.9%) except BTEX, chlorinated phenols, and high molecular weight (MW) PAHs. Chlorinated phenols and high MW PAHs were mainly removed via sorption to activated sludge (51.8%–73.2% and 60.2%–75.9%, respectively). Air stripping and volatilization were the dominant mechanisms for removing the BTEX compounds (59.8%–73.8%). The total emission rates of the detected volatile pollutants from plant C and the central WWTP were 1,640 g d−1 and 784 g d−1, respectively. Benzene from the equalization basins of plant C and the central WWTP corresponded to the highest inhalation carcinogenic risks (1.4 × 10−3 and 3.2 × 10−4, respectively), which exceeded the acceptable level for human health (1 × 10−6) recommended by the United States Environmental Protection Agency. The results showed that BaP exhibited the highest inhalation non-cancer risk, with a hazard index ratio of 70 and 30 for plant C and the central WWTP, respectively. Moreover, the excess sludge generated during wastewater treatment should also be carefully handled because it adsorbed abundant PAHs and chlorinated phenols at coking plant C (58,000 μg g−1 and 3,500 μg g−1) and the central WWTP (622 μg g−1 and 54 μg g−1).

The impact of low molecular weight organic acids from plants with C3 and C4 photosystems on the rhizoremediation of polycyclic aromatic hydrocarbons contaminated soil

Abstract This study evaluated the role of the low molecular weight organic acids (LMWOAs) from the root exudates of C3 (sunflower and wallaby grass) and C4 (maize, Sudan grass, and vetiver) plants on the degradation of Polycyclic aromatic hydrocarbons (PAHs). The LMWOAs that were detected from the rhizospheres of C3 and C4 plants were aconitic, citric, lactic, malic, malonic, succinic and oxalic acids. A greater difference in the quantity of LMWOAs was observed between selected C3 and C4 plants. Among the LMWOAs detected in C3 and C4 plants, the concentration of citric acid was correlated significantly with high PAHs degradation percentage, followed by succinic and aconitic acid in both C3 and C4 plants. The results of this study indicated that the LMWOAs from the selected C4 plants have a greater influence on the PAHs degradation than the C3 plants.

Remediation criteria for gasworks-impacted sediments: Assessing the effects of legacy hydrocarbons and more recent metal contamination

Historical contamination of sediments from industries that commenced before environmental regulations were commonplace is prevalent in many large cities. This contamination is frequently overlain and mixed with more recent urban contamination. The remediation of contaminated sites is often a very expensive exercise and the final remediation criteria often reflect a trade-off between protecting human and ecological health and the finances of those deemed responsible for the site clean-up. In this study, we describe an assessment of estuarine sediments impacted historically by contamination from a gasworks site. The major historical sediment contaminants included polycyclic aromatic hydrocarbons (PAHs) and other petroleum-related hydrocarbons (TRHs). Elevated concentrations of metals exist throughout the city region due to historical pollution and ongoing urban stormwater discharges. Equilibrium partitioning models were used to consider the influence on the bioavailability of PAHs of both natural sedimentary organic carbon and forms of black carbon (pyrogenic carbon - coal tars, charcoal). The strongest predictor of the observed sublethal toxicity to amphipod and copepod reproduction was a combination of total PAHs and metals (primarily Cu, Pb and Zn). Total PAHs was the strongest predicting variable for toxicity to organism survival. While high total PAH concentrations were attributed to the former gas works, high background concentrations of metals existed throughout much of this region of the estuary. Thus, without remediation at the estuary-scale, resuspension of the surrounding sediments by tidal currents and boat movements is predicted to re-contaminate remediated areas with sediments that may continue to cause chronic toxicity due to metals. The assessment indicated that remedial actions that remove or isolate sediments that caused toxicity to benthic organism survival would lead to significant improvements in ecosystem health, but toxicity to organism reproduction may remain at similar levels that exist throughout much of this region of the estuary due to high metal concentrations.

Melting scenario affects the dynamics of polycyclic aromatic hydrocarbons released from snowpack

Melting snowpack can release semi-volatile organic contaminants (SVOCs) to both terrestrial and aquatic ecosystems, resulting in high ecological risk. The dynamics of polycyclic aromatic hydrocarbon (PAH) released from snowpack under controlled laboratory (intense melting) and field (melt/freeze melyting) snowmelt experiments was investigated in this study. In the laboratory: dissolved organic carbon (DOC) controlled the first flush of dissolved PAHs released from snowpack, except for napthelene, which is also affected by its solubility. The particles released early from snowpack usually contained high PAH concentrations (more than 100 μg g−1) and those released at the end contained low PAH concentrations (<20 μg g−1). The total PAH release pattern was determined by composition of all PAHs, including type 2 enrichment with a final peak and type 4 enrichment with double-peak. In field melting: all dissolved PAHs were released constantly, except naphthalene, which also showed a first flush but to a lesser extent. DOC controlled the release pattern of all detected dissolved PAHs from snowpack. High PAH concentrations were observed in particles released from snowpack at both the beginning and the end of the melting event. Concentrations of both total PAHs and PAH compositions in meltwater showed an increasing trend with melting time (from 1.3 to 4.0 μg l−1 and from 1.7 to 5.3 μg l−1 in meltwater from each of the two snowpacks), which coincided with Type 3 enrichment. Overall, our results suggest intense melting of snowpack results in the shift of some hydrophobic PAH compositions from Type 2 to Type 4 enrichment, depending on their partition coefficients. In contrast, melting with melt/freeze cycles may cause the shift of PAHs from Type 2 to Type 3 enrichment. Our study indicates changes of the melting scenarios due to global warming could affect dynamics of SVOCs released from snowpack, which is useful for risk management for water and soil quality.

Natural archives of long-range transported contamination at the remote lake Letšeng-la Letsie, Maloti Mountains, Lesotho

Naturally accumulating archives, such as lake sediments and wetland peats, in remote areas may be used to identify the scale and rates of atmospherically deposited pollutant inputs to natural ecosystems. Co-located lake sediment and wetland cores were collected from Letšeng-la Letsie, a remote lake in the Maloti Mountains of southern Lesotho. The cores were radiometrically dated and analysed for a suite of contaminants including trace metals and metalloids (Hg, Pb, Cu, Ni, Zn, As), fly-ash particles, stable nitrogen isotopes, polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants such as polychlorinated biphenyls (PCBs), polybrominated flame retardants (PBDEs) and hexachlorobenzene (HCB). While most trace metals showed no recent enrichment, mercury, fly-ash particles, high molecular weight PAHs and total PCBs showed low but increasing levels of contamination since c.1970, likely the result of long-range transport from coal combustion and other industrial sources in the Highveld region of South Africa. However, back-trajectory analysis revealed that atmospheric transport from this region to southern Lesotho is infrequent and the scale of contamination is low. To our knowledge, these data represent the first palaeolimnological records and the first trace contaminant data for Lesotho, and one of the first multi-pollutant historical records for southern Africa. They therefore provide a baseline for future regional assessments in the context of continued coal combustion in South Africa through to the mid-21st century.

Dermal bioaccessibility and absorption of polycyclic aromatic hydrocarbons (PAHs) in indoor dust and its implication in risk assessment

Numerous studies have focused on assessing the risk of human exposure to polycyclic aromatic hydrocarbons (PAHs) in indoor dust via dermal contact. However, the dermal bioaccessibility and dermal absorption of PAHs in indoor dust have seldom been reported. In the present study, the effects of temperature, sweat ratio, solid-liquid ratio and incubation time on the dermal bioaccessibility of PAHs were examined. Naphthalene, phenanthrene, pyrene and benzo[a]pyrenewere selected for examination in an absorption assay with keratinocyte cells. The results showed the release of PAHs from indoor dust fitted a first-order one-compartment model. Naphthalene had the highest rate of release, which was consistent with the bioaccessibility assay results. In addition, the absorption rate of naphthalene and phenanthrene by keratinocytes was higher than that of pyrene and benzo[a]pyrene, with the latter being of higher molecular weight. These results indicated that low molecular weight PAHs were much more easily absorbed via dermal contact than were high molecular weight PAHs. The dermal bioavailability of PAHs in indoor dust was estimated by multiplying the bioaccessibility of PAHs in indoor dust by the ratio of dermal absorption by skin cells, and ranged from 0.12 to 51.0%. These data will be useful in risk assessments.

Long-term willows phytoremediation treatment of soil contaminated by fly ash polycyclic aromatic hydrocarbons from straw combustion

A three-year experiment was conducted to investigate willows of Salix × smithiana Willd. (S. smithiana) phytoremediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs) derived by fly ash from biomass combustion. The total removal of ash PAHs in phytoremediation treatment was 50.9% after three consecutive years while the ash PAHs were decreased in natural attenuated soil by 9.9% in the end of the experiment. The ash and spiked PAHs with low and medium molecular weight were susceptible to be removed in higher rates than high molecular weight PAHs. Lower bioconcentration factors of individual PAHs were observed in willow shoots than in roots. The estimated relative direct removal of PAHs by S. smithiana in phytoremediation was significantly lower than 1% suggesting that the contribution of S. smithiana to take up PAHs from soil was negligible and the degradation of PAHs occurred mainly in soil. Phytoremediation using S. smithiana could be seen as a feasible and environmentally friendly approach of arable soils impacted by a PAH contaminated biomass fly ash.

Nonionic and anionic surfactant-washing of polycyclic aromatic hydrocarbons in estuarine sediments around an industrial harbor in southern Taiwan

Various surfactants, such as nonionic Triton X-100 and Simple Green™ (SG), and anionic sodium dodecylsulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) were utilized to remove polycyclic aromatic hydrocarbons (PAHs) from heavily contaminated harbor sediments dredged from Kaohsiung Harbor in Taiwan. Desorption/re-sorption equilibrium, kinetics, and washability of PAHs using the selected surfactant were evaluated under different critical micelle concentrations (CMC). Experimental results revealed that the desorption rate of high molecular weight PAHs was greater than those of low molecular weight PAHs, and the anionic SDS was relatively effective in the removal of total PAHs (>50%) compared to the other surfactants. The correlation between the effectiveness of the surfactant washing processes and the physicochemical properties of individual PAH was statistically analyzed. The resulting data suggested that hydrophobic factors (Kow, Koc and Sw) affected PAH treatability more than the reactivity of PAH (electron affinity and ionization potential). Since the adsorption of anionic surfactant altered the hydrophobicity of organic matter in the sediment, PAHs preferred transferring from the sediment to the hydrophobic core of micelles in aqueous solution. Nevertheless, the nonionic surfactant enhanced the PAH partition in the aqueous phase, thus increasing the micellar solubilization of PAH.