Distribution Of Polycyclic Aromatic Hydrocarbons Concentrations Research Articles

Exploring the influence of water exchange on the distribution of polycyclic aromatic hydrocarbons in marine sediments by numerical calculation model

Polycyclic aromatic hydrocarbons (PAHs) are one of the most important pollution factors in the marine environment. It is significant to expound their distribution in the complex marine environment for pollution prevention and control. In our previous research, we found that water exchange of PAHs has an important influence on their concentration distribution in sediments. With the help of Delft3D technology, a multi-process coupled dynamic model of PAHs was constructed, being based on the survey data of Liaodong Bay from May to June 2015. The water exchange rate of PAHs was calculated and studied by using mathematical statistics and numerical simulation. The results showed that the half water exchange time of PAHs in Liaodong Bay is about 57–580 days. The water exchange rate of PAHs has a significant influence on their concentration distribution of PAHs in sediments. Where there is a high water exchange rate, there the concentration of PAHs in sediment was relatively low. The closer areas are to bay-head, the lower the water exchange rate, and the easier leading to the formation of high concentration areas of PAHs in the sediments.

Concentration assessment and source evaluation of 16 priority polycyclic aromatic hydrocarbons in soils from selected vehicle-parks in southern Nigeria

The objectives of this study are to determine the concentrations and evaluate the sources of 16-priority polycyclic aromatic hydrocarbons (PAHs) in soils from selected vehicle-parks in southern Nigeria. The collection of soil samples was by soil auger from three sites at top (0–15 cm) and sub (15–30 cm) soil levels. Some soil physicochemical parameters were determined. Gas chromatography equipped with flame ionization detector (GC-FID was used to determine the concentrations of PAHs. The wet season concentrations of ∑16 PAHs range from 365.8 to 1065.8 µg/kg and 142.9 to 5321.9 µg/kg for top and sub soils, respectively, while the dry season concentrations of the ∑16 PAHs range from 66.4 to 269.3 µg/kg and 212.1 to 1342.5 µg/kg for top and sub soils, respectively. There was significant seasonal variation (p < 0.05) in the concentrations of PAHs in this study. Analyses of variance also show significant variation (p < 0.05) in the PAHs concentrations among the sites in wet and dry seasons. The concentration distribution of PAHs in this study also varied significantly (p < 0.05) with reference to season and soil depth. Isomer pair ratio shows that the principal source of PAHs is pyrogenic mostly from emission from vehicular traffic, and combustion from diesel, wood, coal and fossil fuels.

Revealing the factors affecting occurrence and distribution of polycyclic aromatic hydrocarbons in water and sediments of Lake Baikal and its tributaries

ABSTRACTThe concentrations of polycyclic aromatic hydrocarbons (PAH), total carbon (TC), total organic carbon (TOC), total nitrogen (TN) and dissolved inorganic nitrogen (DIN) in water and sediments of Lake Baikal and its tributaries were measured. It was found that according to existing water and sediment quality standards limiting permissible PAH concentrations, both surface waters and sediments in Lake Baikal watershed can be considered as unpolluted with PAHs compounds. Nevertheless, the spatial distribution of PAH concentrations in lake water indicates the existence of some point PAH sources in and around the lake. These sources were natural oil seeps and communal facilities such as residential coal-fired and oil-fired boilers. It was observed that concentrations of PAHs in both water and sediments are controlled by organic matter content and organic matter mineralisation degree, as indicated by PAH-to-carbon and nitrogen-to-carbon ratios respectively. It was found that PAH/TOC and PAH/TC ratios characterise PAH loading on water and sediments respectively, whereas DIN/TOC and TN/TC ratios characterise self-purification of water and sediments respectively. It was proved that PAH/TOC and DIN/TOC ratios can be used as tracers to evaluate the PAH contributions from tributaries to Lake Baikal.

Personal Exposure of Children to Particle-Associated Polycyclic Aromatic Hydrocarbons in Tianjin, China

Polycyclic aromatic hydrocarbons (PAHs) associated with fine particles are harmful to human health, particularly to children, who are most vulnerable. To evaluate the respiratory exposure of children to particle-associated PAHs properly, personal air sampling near breathing zone of 36 schoolchildren were conducted in Tianjin, China. Sixteen priority PAHs designated by the United States Environmental Protection Agency were measured using GC-MS. The average concentrations of personal exposure to ∑16PAH were 27.31 ± 3.91 ng/m3 in summer and 58.18 ± 24.68 ng/m3 in winter. Moreover, PAH profiles were studied and the results showed NAP, BbF, and IPY were the most abundant PAHs. Five rings PAH species made up the largest proportion, accounting for 25.7% in summer and 32.6% in winter. Diagnostic ratios and principal component analysis indicated combustion activities were the major source for children exposure to particle-associated PAHs in this study. According to the risk assessment results, the inhalation exposure risk for children were higher than the acceptable risk level of 10–6, indicating the health issues of children should be paid more attention. On the basis of sensitivity analysis results, further research should be done to improve the inhalation cancer slope factor of BaP and the concentration distribution of PAHs in order to improve the accuracy of the health risk assessment.

3-D simulation of soot formation in a direct-injection diesel engine based on a comprehensive chemical mechanism and method of moments

Here, we propose both a comprehensive chemical mechanism and a reduced mechanism for a three-dimensional combustion simulation, describing the formation of polycyclic aromatic hydrocarbons (PAHs), in a direct-injection diesel engine. A soot model based on the reduced mechanism and a method of moments is also presented. The turbulent diffusion flame and PAH formation in the diesel engine were modelled using the reduced mechanism based on the detailed mechanism using a fixed wall temperature as a boundary condition. The spatial distribution of PAH concentrations and the characteristic parameters for soot formation in the engine cylinder were obtained by coupling a detailed chemical kinetic model with the three-dimensional computational fluid dynamic (CFD) model. Comparison of the simulated results with limited experimental data shows that the chemical mechanisms and soot model are realistic and correctly describe the basic physics of diesel combustion but require further development to improve their accuracy.

Health risk assessment for traffic policemen exposed to polycyclic aromatic hydrocarbons (PAHs) in Tianjin, China

In China, traffic policemen have to stand for several hours a day at the road intersections with high vehicle flows. To assess their exposure to airborne carcinogenic polycyclic aromatic hydrocarbons (PAHs) during their working time, a preliminary study was conducted to measure the personal exposure level to PAHs. And a probabilistic incremental lifetime cancer risk (ILCR) model together with the benzo[a]pyrene (BaP) toxic equivalents (BaP(eq)) method was used to conduct health risk assessment. Personal exposure monitors (PEM) were carried by traffic policemen to collect PM10 samples during their daily work in Tianjin, China. Meanwhile, PM100 samples were collected at the roadsides and on campus of Nankai University as comparison. PAHs species were quantitatively analyzed by GC/MS. Experimental results showed that the concentrations of total PAHs, BaP and BaP(eq) were much higher at the road intersections (867.5, 26.2, 82.4 ng m(-3)), where the traffic policemen stand during their work time, than those at the roadsides (46.6, 1.5, 5.7 ng m(-3)), and on campus (19.5, 0.7, 2.4 ng m(-3)). According to the risk assessment results, the occupational risk falls within the range from 10(-6) to 10(-3). On the basis of sensitivity analysis results, further research should be directed to give better characterization of the yearly concentration distribution of PAHs and the cancer slope factor (CSF) of BaP in order to improve the accuracy of the health risk assessment.

DISTRIBUTION AND TRANSPORTATION OF POLYCYCLIC AROMATIC HYDROCARBONS IN SUSPENDED PARTICULATE MATTER AND SURFACE SEDIMENT FROM THE PEARL RIVER ESTUARY

ABSTRACT Based on the quantitative and qualitative analysis of sixteen Polycyclic Aromatic Hydrocarbons (PAHs) with GC and GC-MSD, the concentrate distribution and transportation characteristics of PAHs in suspended particulate matter (SPM) and surface sediments (SS) from the Pearl River Estuary were studied. Whether in SPM or in SS, the concentration distribution of PAHs were characterized by acenaphthene (mean 55.5 µg/g in SPM, 226 ng/g in SS) with subordinate amounts of the tri- and tetra-cycle PAHs such as fluorene, fluoranthene, phenaphene and pyrene. However, PAHs had different composition and concentration in SPM and SS. Pentacyclic PAHs appeared in SS and seldom in SPM because of their low solubility and high molecular weight. The concentrations of the tri-, tetracyclic PAHs in SPM were 100–300 times higher than those in SS. The total PAHs varied from 12–281 µg/g (mean 77 µg/g) in SPM and 208–1849 ng/g (mean 537 ng/g) in SS respectively. There were similar correlations between the concentrations of PAHs in SPM and salinity, and between the distance of the stations from the river outlet moving seawards and the concentrations of PAHs. These indicated that PAHs were degraded or transported along with the salinity gradient in SPM and the distance from the river outlet in SS. It was also suggested that the sources of these PAHs are from sewage and shipping discharge-pollutants. Pearl River Estuary had been lightly contaminated by PAHs.

Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Pore Water and Sediment of a Small Aquatic Ecosystem

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured both in pore water and solid sediment isolated from the Teufelsweiher pond, a small aquatic ecosystem in Upper Bavaria (Germany) from 1992 to 1994. All 16 EPA priority compounds were present with mean total concentrations from 501 to 663 ng/1 in the pore water and 976–1600 μg/kg (dry weight) in the solid sediment. Fluoranthene and pyrene were the dominant compounds and accounted for 21–28% of the total PAHs, the ratios of fluoranthene/pyrene and phenanthrene/anthracene ranging from 1.61–2.86 and 0.86–1.57, respectively. These results suggest that the main sources of PAHs are incomplete combustion processes of fossil fuel; the compounds are then transported into the Teufelsweiher by deposition and runoff. The distribution of PAH concentrations exhibit a pronounced dependence on both particle size and organic matter content of the sediment: two fractions (< 6.3 μm and 63–200 μm), containing higher contents of organic matter, trapped more PAHs compared with other fractions. The dissolved organic carbon (DOC) in the pore water is mostly responsible for lower KOC' in situ measured compared with the estimated KOC. The spatial and temporal variations of PAH concentrations are also discussed.