Low Molecular Weight Priority Polycyclic Aromatic Hydrocarbons Research Articles

Sources and distribution of polycyclic aromatic hydrocarbons of different glaciers over the Tibetan Plateau

Twenty snow samples were collected from the Qiyi glacier in Qilian Mountains, the Yuzhufeng glacier in eastern Kunlun Mountains, the Xiaodongkemadi glacier in Tanggula Mountains, and the Gurenhekou glacier in Nyainqentanglha Range over the Tibetan Plateau. The concentration and distribution features of sixteen priority Polycyclic Aromatic Hydrocarbons (PAHs) were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). The sources of these PAHs were explored as well. Our results indicated that the average concentrations of PAHs in snow were in the range of 20.45–60.57 ng/L. Maximum PAHs levels were found in the YZF glacier and minimum in the XDKMD glacier. However, no apparent regional distribution pattern of PAHs was found in the glaciers over the Tibetan Plateau. Moreover, the 2–4 ring low molecular weight PAHs predominated in snow samples and the concentrations of phenanthrene was the highest. Integrated factor analysis and isomer pair ratios suggested that PAHs of glaciers over the Tibetan Plateau were derived from low temperature combustion of coal and biomass, and partially from the exhaust gas of locomotives. Air mass back trajectory indicated that organic compounds detected in snowpit of these four glaciers, in the period of time they represented, mainly came from Central Asia and the arid area of Northwest China by westerly wind circulation.

Spatial distribution and source diagnosis of polycyclic aromatic hydrocarbons in soils from Chengdu Economic Region, Sichuan Province, western China

Surface soils from the Chengdu Economic Region (CER) were analyzed for sixteen United States Environment Protection Agency priority polycyclic aromatic hydrocarbons (PAHs) to study the spatial distribution and to identify the sources of PAHs. Relatively high concentrations (more than 1500 ngg − 1 ) of high molecular weight PAHs were found in Chengdu Plain, in the middle of CER, while high concentrations (more than 500 ng g − 1 ) of low molecular weight PAHs were detected in the surrounding mountains. The concentrations of ∑ 16-PAHs in topsoil samples from CER (12.52–75,431.47 ngg − 1 , average value was 3233.92 ngg − 1 ) were higher than that from the southern China (21.91–3077 ngg − 1 , average value was less than 500 ngg − 1 ), and they were comparable to concentrations in soils from the northern China (366–254,080 ngg − 1 , mean value was more than 3000 ngg − 1 ). The concentrations from CER were also much higher than the concentrations of some world clean regions such as Antarctic (34.9–171 ngg − 1 ), European high mountains (9–11,000 ngg − 1 , mean value was 158 ngg − 1 ) and some Europe residential (736 ngg − 1 ) and arable soils (60–145 ngg − 1 , mean value was 66 ngg − 1 ). The ratio of tracer compounds (BaA/(BaA + Chr), Flo/(Flo + Pyr), and IcdP/(IcdP + BghiP)) indicated that the high concentrations of PAHs in soils were mainly derived from fossil fuels combustion in mountain region and from the incomplete combustion of petroleum in developed plain area (such as Chengdu and Deyang). From the above distribution characteristics and ratios of tracer compounds, we inferred the reasons for the distribution pattern of PAHs in CER were the domestic heating, emissions, and the physicochemical properties of PAHs.

Pattern, sources and toxic potential of PAHs in the agricultural soils of Delhi, India

Surface soil (0–5 cm) from various agricultural sites in Delhi was analyzed to discern the contents of 16 priority polycyclic aromatic hydrocarbons (PAHs). Reference and deuterated standards were used for identification and quantification of PAHs by high performance liquid chromatography (HPLC) with UV detection. ∑ 16PAHs ranged from 830 to 3880 μg kg −1 (dry wt.) with an arithmetic mean of 1910 ± 1020 μg kg −1 ∑ 16PAHs values at the urban sites were 2–5 times higher as compared to the rural sites. In general, low molecular weight PAHs were predominant. Total organic carbon (TOC) was found to be significantly correlated with ∑ 16PAHs. Isomer pair ratios and Principal component analysis (PCA) suggested biomass and fossil fuel combustion as the main sources of PAHs. The toxic equivalency factors (TEFs) were used to estimate benzo[ a]pyrene-equivalent concentration (B[ a]P eq). Therewith, PAH content of urban agricultural soil was found to have more carcinogenic potential.

Factors That Influence the Extraction of Polycyclic Aromatic Hydrocarbons from Coal

Coal samples and carbonaceous mudstone were collected from the Huaibei coalfield, China, and experiments investigating the factors influencing the extraction of the sixteen US EPA (Environmental Protection Agency) priority polycyclic aromatic hydrocarbons (PAHs) were carried out. Different extraction times, solvents, and methods were used. Major interest was focused on finding optimum conditions for extracting the PAHs from coal. We conclude that (1) coal composition, including the H/C and O/C ratios, is an important factor for the distribution of PAHs in coals; (2) the total amount of EPA priority PAHs increases with increasing extraction time, 30 min being suitable for ultrasonic-assisted extraction and 24 h for Soxhlet extraction; (3) CS2 is effective in extracting low molecular weight PAHs, while CH2Cl2 is better for extracting high molecular weight PAHs (both are excellent extraction solvents vs hexane); (4) both Soxhlet and ultrasonic extraction showed a similar PAH concentration profile, but the ultrasonic method is less efficient.

Contamination of rivers in Tianjin, China by polycyclic aromatic hydrocarbons

Tianjin urban/industrial complex is highly polluted by some persistent organic pollutants. In this study, the levels of 16 priority polycyclic aromatic hydrocarbons (PAHs) were tested in sediment, water, and suspended particulate matter (SPM) samples in 10 rivers in Tianjin. The total concentration of 16 PAHs varied from 0.787 to 1943 μg/g dry weight in sediment, from 45.81 to 1272 ng/L in water, and from 0.938 to 64.2 μg/g dry weight in SPM. The levels of PAHs in these media are high in comparison with values reported from other river and marine systems. Variability of total concentrations of PAHs in sediment, water, and SPM from nine different rivers is consistent with each other. No obvious trends of total PAHs concentration variations were found between upstream and downstream sediment, water, and SPM samples for most rivers, which indicate local inputs and disturbances along these rivers. The spatial distributions of three-phase PAHs are very similar to each other, and they are also similar to those found in topsoil. However, their chemical profiles are significantly different from that of topsoil. The change of profiles is consistent with the different aqueous transport capability of 16 PAHs. Low molecular weight PAHs predomination suggests a relatively recent local source and coal combustion source of PAHs in the study area.