Exposure radius of a local coal mine in an Arctic coastal system; correlation between PAHs and mercury as a marker for a local mercury source.

Mercury in the Arctic originates from emissions and releases at lower latitudes and, to a lesser extent, from local and regional sources. The relationship between mercury (Hg) and polycyclic aromatic hydrocarbons (PAHs) in sediment can be applied as an indicator of the mercury source. This research examines the Hg contamination gradient from a land-based coal mine to the surrounding coastal environment to quantify the impact of local sources. Total mercury and PAH (Σ14PAH) were measured in terrestrial and marine sediments as well as in marine biota. Samples were collected at the mine and two reference sites. Mercury and Σ14PAH concentrations in samples collected at the mine site were significantly higher than those at the reference sites. This was also found in the biota samples, although less pronounced. This work addresses the complexities of interpreting data concerning very low contaminant levels in a relatively pristine environment. A clear correlation between PAH and Hg concentration in sediment was found, although a large number of samples had levels below detection limits. PAH profiles, hierarchical clustering, and molecular diagnostic ratios provided further insight into the origin of PAHs and Hg, showing that signatures in sediments from the nearest reference site were more similar to the mine, which was not the case for the other reference site. The observed exposure radius from the mine was small and diluted from land to water to marine biota. Due to low contamination levels and variable PAH profiles, marine biota was less suitable for tracing the exposure radius for this local land-based Hg source. With an expected increase in mobility and availability of contaminants in the warming Arctic, changes in input of PAHs and Hg from land-based sources to the marine system need close monitoring.

Pollution investigation and risk assessment of polycyclic aromatic hydrocarbons in soil and water from selected dumpsite locations in rivers and Bayelsa State, Nigeria.

The transfer ratio of polycyclic aromatic hydrocarbons (PAHs) from soil dumpsite to borehole water is dependent of polluting source and exposure matrices that causes immerse health risk to man and environment over a period of time. PAHs were assessed in selected soil dumpsite and borehole water located at Rivers state (Eleme, Eliozu, Eneka, Oyigbo, and Woji) and Bayelsa state (Yenagoa), Nigeria. Soil samples were collected at four different points 30 m (North, South, East and West) locations at a depth of 15 cm for each dumpsite using soil auger while control samples were collected 200 m away (farmland), where there were little anthropogenic activities and no presence of active dumpsites. Borehole water samples were collected from 300 m distance, which were packaged in an amber container, labeled, and transported to the laboratory for analysis. Standard analytical methods were employed. PAHs concentrations were analyzed using gas chromatography- mass spectrometry (GC-MS) after extraction of water and soil using liquid-liquid and soxhlet extraction methods respectively and clean-up of the extracts, thereafter the laboratory data generated were subjected to statistical analysis. Total PAHs (ΣPAHS) concentrations in soil samples from the study sites ranged from 2.4294 mg/kg in Yenagoa to 5.1662 mg/kg in Eleme while in water samples the total PAHs ranged from 1.3935 mg/L in Woji to 3.009 mg/L in Eleme. The total PAH concentrations in the soil were above the Agency for Toxic Substances and Disease Registry levels of 1.0 mg/kg for a considerably contaminated site except for the control sites. The total concentration of carcinogenic PAHs ranged from 0.0038 to 1.1301mg/kg in soil samples and 0.0014 to 0.9429 mg/L in borehole water samples, therefore raising concern of human exposure via food chain. The results indicate that low molecular weight PAHs were more dominant than high molecular weight PAHs in both soil and water samples, however molecular diagnostic ratio shows that pyrogenic activities are major sources of PAHs as compared to petrogenic origin. Multivariate analysis (principal component analysis and Pearson correlation) showed strong negative correlation implying that they were from dissimilar sources and different migratory route. Cancer and non-cancer risk showed that children were more at risk compared to adults, where inhalation exposure were major contribution as compared to ingestion and dermal exposure, as such there is a need to implement regulatory laws on indiscriminate release of PAHs contaminants to maintain sustainability.

Emerging and legacy PAHs in urban soils of four small cities: Concentrations, distribution, and sources.

Polycyclic aromatic hydrocarbons (PAHs) are widespread organic contaminants in the environment, much being accumulated in soils. Although their concentrations in large cities have been studied, their levels in small cities were less studied. This study determined the concentrations, distributions, and sources of 16 USEPA priority PAHs (legacy PAHs) and 6 emerging PAHs in urban soils of four small cities. A total of 100 soil samples were collected in Florida, USA. The average ∑16-PAHs in urban soils of Clay county, Ocala, Pensacola, and West Palm Beach were 1821, 2748, 3115 and 4055 µg kg-1, respectively. Based on benzo[a]pyrene-equivalent (BaP-EQ), the 7 USEPA carcinogenic PAHs (7cPAHs) and 3 emerging carcinogenic PAHs (3cPAHs) in urban soils in Clay County averaged 223 and 3703, Ocala 319 and 4521, Pensacola 302 and 5423, and West Palm Beach 449 and 5916 µg kg-1, respectively. Although ∑7cPAHs in 87-89% of samples were lower than the Florida Soil Cleanup Target Levels (FSCTLs) for industrial sites at 700 µg kg-1, ∑3cPAHs were 13-18 times greater than ∑7cPAHs. Based on the PMF model and molecular diagnostic ratios, soil PAHs were dominated by similar sources in small cities, mainly from pyrogenic sources including biomass, coal and coke combustion and vehicle emissions. It is important to evaluate both legacy and emerging PAHs concentrations in urban soils when considering soil remediation and human health risk assessment.

PAHs in urban soils of two Florida cities: Background concentrations, distribution, and sources.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic contaminants, which are found in soils throughout the U.S. The objective of this study was to determine the background concentrations, distributions, and sources of 16 USEPA priority PAHs in two urban soils. A total of 114 soil samples were collected from two large cities in Florida: Orlando and Tampa. The results showed that soils were dominated by high molecular weight PAHs in both cities. The average ∑16-PAHs in Orlando and Tampa soils were 3227 and 4562 µg kg-1, respectively. The averages of 7 carcinogenic PAHs based on the benzo[a]pyrene-equivalent (BaP-EQ) concentrations in the two cities were 452 and 802 µg kg-1. BaP-EQ concentrations in 60-62% of samples were higher than the Florida Soil Cleanup Target Level (FSCTL) for residential soils at 100 µg kg-1 and 20-25% of samples were higher than FSCTL for industrial soils at 700 µg kg-1. Based on molecular diagnostic ratios and PMF modeling, major sources of soil PAHs in both cities were similar, mainly from pyrogenic sources including vehicle emissions, and biomass and coal combustion. Based on ArcGIS mapping, PAH concentrations in soils near business districts and high traffic roads were higher. Thus, it is important to consider background PAH concentrations in urban soils when considering soil remediation.

Characterization of polycyclic aromatic hydrocarbons in fugitive PM10 emissions from an integrated iron and steel plant.

Fugitive emissions of PM10 (particles <10µm in diameter) and associated polycyclic aromatic hydrocarbons (PAHs) were monitored in the vicinity of coking unit, sintering unit, blast furnace and steel manufacturing unit in an integrated iron and steel plant situated in India. Concentrations of PM10, PM10-bound total PAHs, benzo (a) pyrene, carcinogenic PAHs and combustion PAHs were found to be highest around the sintering unit. Concentrations of 3-ring and 4-ring PAHs were recorded to be highest in the coking unit whereas 5-and 6-ring PAHs were found to be highest in other units. The following indicatory PAHs were identified: indeno (1,2,3-cd) pyrene, dibenzo (a,h) anthracene, benzo (k) fluoranthene in blast furnace unit; indeno (1,2,3-cd) pyrene, dibenzo (a,h) anthracene, chrysene in sintering unit; Anthracene, fluoranthene, chrysene in coking unit and acenaphthene, fluoranthene, fluorene in steel making unit. Total-BaP-TEQ (Total BaP toxic equivalent quotient) and BaP-MEQ (Total BaP mutagenic equivalent quotient) concentration levels ranged from 2.4 to 231.7ng/m(3) and 1.9 to 175.8ng/m(3), respectively. BaP and DbA (dibenzo (a,h) anthracene) contribution to total-BaP-TEQ was found to be the highest.

Concentration profiles, source apportionment and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in dumpsite soils from Agbogbloshie e-waste dismantling site, Accra, Ghana.

The concentrations of eighteen (18) polycyclic aromatic hydrocarbons (PAHs), including the 16 USEPA's priority PAHs as well as two alkyl-substituted naphthalenes were determined in dumpsite soils collected from different sampling sites within the Agbogbloshie e-waste dismantling site in Accra, Ghana. Following their isolation with ultrasonic-assisted extraction technique, the concentrations of the PAHs were determined by gas chromatography mass spectrometry (GC-MS). Loss-on-ignition (LOI) method was employed for the determination of total organic carbon (TOC) of the soil samples. The mean Σ18PAHs obtained were 3006, 5627, 3046, 5555, and 7199 ng g(-1) dry weight (dw) for sampling sites A (mosque), B (dismantling site), C (residential house/police station), D (personal computer repairers' shop) and E (e-waste open burning area), respectively. In all cases, the prevalence of phenanthrene, fluoranthene and pyrene was generally observed across the sampling sites. In this study, PAHs with two to three rings and four to six rings exhibited strong positive correlations, whereas BbF and BkF showed weak positive and negative correlations with other PAHs investigated. With the exception of BbF and BkF, all the PAHs had moderate to strong positive correlations with the TOC. Benzo[a]pyrene equivalent (BaPeq) concentration is a useful indicator of the carcinogenic potency of environmental matrices and these ranged between 111 and 454 ng g(-1), which are generally below the 'safe' level of 600 ng g(-1) established for the protection of the environment and human health. Interestingly, the seven carcinogenic PAHs were the major contributors to the BaPeq concentrations accounting between 97.7 and 98.3 %. Despite the minimal risk to cancer via exposure to the investigated dumpsite soil as indicated in the present study, the prolonged exposure to these pollutants via various exposure pathways may result in increased risk to cancer over time. The application of several methodological approaches for PAH source apportionment, including the use of molecular diagnostic ratios, mostly implicated pyrogenic processes as the main sources of PAHs into the investigated dumpsite soils. Furthermore, their compositional profiles across the sampling sites also suggest similar sources of PAHs into the dumpsite soil.

The qualitative and quantitative source apportionments of polycyclic aromatic hydrocarbons in size dependent road deposited sediment.

This study showcases the qualitative and quantitative source apportionments of size-dependent polycyclic aromatic hydrocarbons (PAHs) in road deposited sediment by means of molecular diagnostic ratio (MDR) and positive matrix factorisation (PMF) approaches. The MDR was initially used to narrow the PAH source candidates. PMF modelling was subsequently used to provide more precise source apportionment with the assistance of a multiple linear regression analysis. Through a combined qualitative and quantitative source apportionment, different potential source contributors were identified at different size fractions. Explicitly, three major contributors to sorption at the size fraction of 1000-400 µm were tentatively identified as incineration (26%), coal combustion (53%) and gasoline-powered vehicle (20%). Four major contributors to the size fraction of 400-100 µm were identified as gasoline-powered vehicle (25%), surface pavement (15%), diesel-powered vehicle (37%) and industrial boiler (24%). Four major contributors to the size fraction of 100-63 µm were identified as cogeneration emission (13%), diesel-powered vehicle (28%), tire debris (45%) and wood combustion (14%). The potential contributors in the size fraction 63-0.45 µm were identified as diesel-powered vehicle (21%), heterogeneous sources (41%) and biomass burning (38%). In addition, the highest ∑16PAH concentration was found in the smallest size fraction of 63-0.45 µm, which is also where the highest BaPE and TEF values for potential risk assessment occurred.

Model-based evaluation of the use of polycyclic aromatic hydrocarbons molecular diagnostic ratios as a source identification tool.

Polycyclic Aromatic Hydrocarbons (PAHs) molecular diagnostic ratios (MDRs) are unitless concentration ratios of pair-PAHs with the same molecular weight (MW); MDRs have long been used as a tool for PAHs source identification purposes. In the present paper, the efficiency of the MDR methodology is evaluated through the use of a multimedia fate model, the calculation of characteristic travel distances (CTD) and the estimation of air concentrations for individual PAHs as a function of distance from an initial point source. The results show that PAHs with the same MW are sometimes characterized by substantially different CTDs and therefore their air concentrations and hence MDRs are predicted to change as the distance from the original source increases. From the assessed pair-PAHs, the biggest CTD difference is seen for Fluoranthene (107 km) vs. Pyrene (26 km). This study provides a strong indication that MDRs are of limited use as a source identification tool.

Multimedia fate and source apportionment of polycyclic aromatic hydrocarbons in a coking industry city in Northern China.

A steady state Level III fate model was established and applied to quantify source-receptor relationship in a coking industry city in Northern China. The local emission inventory of PAHs, as the model input, was acquired based on energy consumption and emission factors. The model estimations were validated by measured data and indicated remarkable variations in the paired isomeric ratios. When a rectification factor, based on the receptor-to-source ratio, was calculated by the fate model, the quantitatively verified molecular diagnostic ratios provided reasonable results of local PAH emission sources. Due to the local ban and measures on small scale coking activities implemented from the beginning of 2004, the model calculations indicated that the local emission amount of PAHs in 2009 decreased considerably compared to that in 2003.