Distribution Of Polycyclic Aromatic Hydrocarbons In Soils Research Articles

Inventory, source and health risk assessment of nitrated and parent PAHs in agricultural soils over a rural river in Southeast China

Nitrated polycyclic aromatic hydrocarbons (NPAHs) have become a concerning topic because of their widespread occurrence and carcinogenicity. However, studies on NPAHs in soils, especially in agricultural soils, are still limited. In this study, a systematic monitoring campaign of 15 NPAHs and 16 polycyclic aromatic hydrocarbons (PAHs) was performed in agricultural soils from the Taige Canal basin in 2018, which is a typical agricultural activity area of the Yangtze River Delta. The total concentration of NPAHs and PAHs ranged from 14.4 to 85.5 ng g−1 and 118–1108 ng g−1, respectively. Among the target analytes, 1,8-dinitropyrene and fluoranthene were the most predominant congeners accounting for 35.0% of ∑15NPAHs and 17.2% of ∑16PAHs, respectively. Four-ring NPAHs and PAHs were predominant, followed by three-ring NPAHs and PAHs. NPAHs and PAHs had a similar spatial distribution pattern with high concentrations in the northeastern Taige Canal basin. The soil mass inventory of ∑16PAHs and ∑15NPAHs was evaluated to be 31.7 and 2.55 metric tons, respectively. Total organic carbon had a significant impact on the distribution of PAHs in soils. The correlation between PAH congeners in agricultural soils was higher than that between NPAH congeners. Based on diagnostic ratios and principal component analysis-multiple linear regression model, vehicle exhaust emission, coal combustion, and biomass combustion were the predominant sources of these NPAHs and PAHs. According to the lifetime incremental carcinogenic risk model, the health risk posed by NPAHs and PAHs in agricultural soils of the Taige Canal basin was virtually negligible. The total health risk in soils of the Taige Canal basin to adults was slightly higher than that to children.

Nationwide distribution of polycyclic aromatic hydrocarbons in soil of China and the association with bacterial community

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has raised great environmental concerns. However, the information on national wide distribution of PAHs in soil as well as their effect on soil bacterial community are limited. In this study, 16 PAHs were measured in 94 soil samples collected across China. The total concentration of 16 PAHs (∑PAHs) in soil ranged from 74.0 to 17,657 ng/g (dry weight basis), with a median value of 200 ng/g. Pyrene was the major soil PAH, with a median concentration of 71.3 ng/g. Soil samples from Northeast China had a higher median concentration of ∑PAHs (1,961 ng/g) than those from other regions. Petroleum emission and wood/grass/coal combustion were potential sources for soil PAHs based on diagnostic ratios and positive matrix factors analysis. A nonnegligible ecological risk (hazard quotients > 1) was found in over 20% of soil samples analyzed and the highest median total HQs value (8.53) was found in soils from Northeast China. The effect of PAHs on bacterial abundance, α-diversity, and β-diversity was limited in the soils surveyed. Nevertheless, the relative abundance of some members in genera Gaiella, Nocardioides, and Clostridium was significantly correlated with the concentrations of some PAHs. Especially, the bacterium Gaiella Occulta showed potential in indicating soil contamination by PAH, which is worth further exploration.

Distribution and sources of polycyclic aromatic hydrocarbons in soils along the Shatt Al-Arab River Delta in southern Iraq

The soil samples from 0–10 cm depth were collected from three areas (Center of Basrah – CB, Garmat Ali – GA, and Abu Al-Khasib – AK) located along the Shatt Al-Arab River (SR) delta in southern Iraq to estimate the distribution and sources of polycyclic aromatic hydrocarbons (PAHs). The PAH total concentrations in the soils decreased significantly from CB (72.16 ng/g dry weight (DW)), GA (36.48 ng/g DW), to AK (17.30 ng/g DW) gradually indicating the impact of pollution emissions on the distribution of PAHs in soils. The low (2 and 3 ring) and high (4, 5, and 6 ring) molecular weight PAHs accounted for 14%, 16%, 37%, 21%, and 12% respectively in CB soil, 24%, 31%, 29%, 7%, and 10% in GA soil and 40%, 29%, 17%, 8%, and 8% in AK soil. The high molecular weight PAHs predominated in CB soils and the low molecular weight PAHs dominated in GA and AK soils suggesting a difference in emission sources between the studied areas. The PAH diagnostic ratios and principal component analysis (PCA) indicated that PAHs in soils of the SR delta essentially originated from traffic and industrial emissions and biomass and grass/wood/coal combustion. The PAH atmospheric transport from CB area might impact the PAH distribution in the soils of AK area. The risk assessment of the soils has been performed. The total toxic equivalent concentrations (Bap<sub>teq</sub>) of PAHs in the examined areas did not exceed the Dutch target values suggesting that no carcinogenic risk for the SR delta soils was found.

Uptake and translocation of polycyclic aromatic hydrocarbons (PAHs) and heavy metals by maize from soil irrigated with wastewater

By investigating the uptake of 16 priority polycyclic aromatic hydrocarbons (PAHs) and five heavy metals from soils to maize at the farmlands with industrial wastewater irrigation, this study revealed the effects of heavy metals on PAHs uptake in terms of co-contamination. The results of 15 investigated soils showed medium contamination level and the vertical PAHs distribution in soils indicated that 2–3 rings PAHs with low octanol-water partition coefficient (log Kow < 4.5) were easier to transport in soils, causing a great potential risk immigrating to the groundwater. The 3-ring PAHs were most likely to be taken up by maize roots whereas 2- and 4–6 ring PAHs had the lower likelihood. The translocation of PAHs in maize tissues has positive relationship with log Kow less than 4.5, while negatively correlated otherwise. Redundancy analysis indicated the unexpected results that, except for soil PAHs concentration, the PAHs translocation by maize was reduced by Pb uptake, but not significantly affected by soil organic matters, pH or the other four heavy metals (Cr, Cu, Ni and Zn). This study for the first time provides the restricted factors of PAHs and heavy metal acropetal translocation by maize when they co-exist at wastewater irrigation sites.

Accumulation, allocation, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soil-Brassica chinensis system.

Farmland soil and leafy vegetables accumulate more polycyclic aromatic hydrocarbons (PAHs) in suburban sites. In this study, 13 sampling areas were selected from vegetable fields in the outskirts of Xi’an, the largest city in northwestern China. The similarity of PAH composition in soil and vegetation was investigated through principal components analysis and redundancy analysis (RDA), rather than discrimination of PAH congeners from various sources. The toxic equivalent quantity of PAHs in soil ranged from 7 to 202 μg/kg d.w., with an average of 41 μg/kg d.w., which exceeded the agricultural/horticultural soil acceptance criteria for New Zealand. However, the cancer risk level posed by combined direct ingestion, dermal contact, inhalation of soil particles, and inhalation of surface soil vapor met the rigorous international criteria (1×10−6). The concentration of total PAHs was (1052±73) μg/kg d.w. in vegetation (mean±standard error). The cancer risks posed by ingestion of vegetation ranged from 2×10−5 to 2×10−4 with an average of 1.66×10−4, which was higher than international excess lifetime risk limits for carcinogens (1×10−4). The geochemical indices indicated that the PAHs in soil and vegetables were mainly from vehicle and crude oil combustion. Both the total PAHs in vegetation and bioconcentration factor for total PAHs (the ratio of total PAHs in vegetation to total PAHs in soil) increased with increasing pH as well as decreasing sand in soil. The total variation in distribution of PAHs in vegetation explained by those in soil reached 98% in RDA, which was statistically significant based on Monte Carlo permutation. Common pollution source and notable effects of soil contamination on vegetation would result in highly similar distribution of PAHs in soil and vegetation.

Spatial Distribution of Polycyclic Aromatic Hydrocarbons in Soils around the Coal Waste Rock Dumps

We select a large coal waste rock dumps in Guangxi Heshan , study the characteristics of the distribution of polycyclic aromatic hydrocarbons (PAHs) in its surrounding soil and carry on a soil quality evaluation. Soil samples were collected in different distance and different depth from the dumps. After drying and filtrating the samples, we use the gas chromatography - mass spectrometry (GC - MS) technology for quantitative analysis of 16 kinds of priority pollutions of PAHs. The results show that in the plane, from the near to the distant, the content of PAHs in soil is from much to little. In vertical, from shallow to deep, the content of PAHs degressive changes. And the trend of change is from fast to slow in vertical and level. The plane distribution of PAHs in soil is mainly controlled by wind direction and slope, vertical distribution is controlled by its solubility in water and soil properties.Many kinds of PAHs in soils out of limit, which is poor soil.The 6 kinds of heavy ring PAHs which is carcinogenic is distributed in 5~15 cm of the topsoil.

Multi-factors influencing the spatial distribution of polycyclic aromatic hydrocarbons in soils surrounding drinking water protection zone

We selected the Guanting Reservoir in Beijing, China as a case where an industrial area locates on the upwind corner to study the influence of human activities and natural processes on the distribution of polycyclic aromatic hydrocarbons (PAHs) in soils. Soil PAH concentrations in the study area follow a log-normal probability distribution function, suggesting that distribution of PAH in soils was affected by human activities. Distribution of PAHs in soils was significantly affected by the point source that high PAH concentrations were observed in near industrial area with an obvious declining trend from the northwest to the southeast which was the prevailing wind direction in this area. Away from the influence of point source, distribution of PAHs in soils was found to significantly correlate with total organic carbon content, while the influences of agricultural land uses and type of soil texture on the total soil PAHs contents and ring compositions were quite limited. The results can provide some evidences and data on the pollutant accumulation in drink water protection area influenced by natural processes and human activities.

Polycyclic aromatic hydrocarbons in soils: Sources, behavior, and indication significance (a review)

The current ideas of polycyclic aromatic hydrocarbons (PAHs) in soils are reviewed. Their natural and anthropogenic sources are discussed, and the mechanisms of their arrival from other environmental components to soils are considered. The main processes typical for PAHs in soils are defined; the sorption, degradation, and translocation features of polyarenes in the soil profile are shown. Attention is paid to the geographical features of the PAH distribution in soils. The use of data on the PAHs in soils for the indication of different natural and technogenic processes is also discussed.

Polycyclic aromatic hydrocarbons in soils from the Tibetan Plateau, China: distribution and influence of environmental factors

Thirty four sampling sites along an elevation transect in the Tibetan Plateau region were chosen. Soil cores were divided into several layers and a total of 175 horizon soil samples were collected from July to September 2011, for determination of polycyclic aromatic hydrocarbons (PAHs). The measured PAHs concentration in surface soils was 56.26 ± 45.84 ng g(-1), and the low molecular weight PAHs (2-3 rings) predominated, accounting for 48% and 35%. We analyzed the spatial (altitudinal and vertical) distribution of PAHs in soil, and explored the influence of related environmental factors. Total organic carbon (TOC) showed a controlling influence on the distribution of PAHs. PAH concentrations declined with soil depth, and the composition patterns of PAHs along soil depth indicated that the heavy PAHs tended to remain in the upper layers (0-10 cm), while the light fractions were transported downward more easily. PAHs inventories (8.77-57.92 mg m(-2)) for soil cores increased with mean annual precipitation, while the topsoil concentrations decreased with it. This implies that an increase in precipitation could transfer more PAHs from the atmosphere to the soil and further transport PAHs from the topsoil to deeper layers.

Impact of soil organic matter on the distribution of polycyclic aromatic hydrocarbons (PAHs) in soils

The knowledge on the distribution of hydrophobic organic contaminants in soils can provide better understanding for their fate in the environment. In the present study, the n-butanol extraction and humic fractionation were applied to investigate the impact of SOM on the distribution of polycyclic aromatic hydrocarbons (PAHs). The results indicated that 80.5%–94.8% of the target PAHs could be extracted by n-butanol and 63.1%–94.6% of PAHs were associated with fulvic acid (FA). Concentrations of un-extracted PAHs increased significantly with the increasing soil organic matter (SOM), however, such an association was absent for the extractable fractions. The results suggested that the sequestration played a critical role in the accumulation of PAHs in soils. SOM also retarded the diffusion of PAHs into the humin fractions. It implied that sequestration in SOM was critical for PAH distribution in soils, while the properties of PAH compounds also had great influences.

Correlations between physicochemical properties of PAHs and their distribution in soil, moss and reindeer dung at Ny-Ålesund of the Arctic

Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in soil, moss and reindeer dung collected at Ny-Ålesund of the Arctic were measured to investigate their accumulation trends and distribution in the three compartments. Compared with the other regions, the proportions of 2 + 3 ring PAHs to the total PAHs were higher, whereas the proportions of 5 + 6 ring PAHs were lower in the three compartments at Ny-Ålesund. Significant log/log-linear relationship was observed between the sub-cooled liquid vapor pressure ( p L ° ) and the soil/moss quotient ( Q SM). The relation was similar to the relationship between the gas/particle partition coefficient ( K P) and p L ° of PAHs, implying Q SM would be a “mirror image” of K P. Excellent log/log-linear relationships were observed between Q SM and K OA as well as between the moss/dung quotient ( Q MD) and K OW. The results presented here indicate the physicochemical properties are suitable for characterizing the distribution of PAHs in soil, moss and reindeer dung.

Distribution of PAHs in pine (Pinus thunbergii) needles and soils correlates with their gas-particle partitioning

Pine (Pinus thunbergii) needles and surface soils were simultaneously sampled at 35 sites across Liaoning province, China, to investigate the distribution of polycyclic aromatic hydrocarbons (PAHs) in the two media. We hypothesized that the distribution of PAHs in soils and pine needles was related to the subcooled liquid vapor pressure (p(o)L) and the gas-particle partition coefficient (Kp), since soils accumulate PAHs mainly through dry/wet deposition of particles and pine needles sequester PAHs mainly from the gas phase, and the same physicochemical properties (e.g., p(o)L) determine the characteristics of PAHs deposition to soils and to needles. To verify the hypothesis, a soil-pine needle quotient (Q(SP)) was defined, which is a dimensionless ratio of PAH concentrations in soils and pine needles. A significant relationship between logQ(SP) and log p(o)L was observed (r = 0.94), and the variation of the regression parameters of log Q(SP)-log p(o)L and log Kp-log p(o)L relationships was similar. An adjusted soil-pine needle quotient (Q'(SP)) was defined by deducting the contributions of particle PAHs to pine needles and the vapor PAHs to soils. Log Q'(SP) correlated with log p(o)L and logarithm of the particle to gas ratio (log Cp/C(A)) more evidently than log Q(SP). In addition, Q(SP) (and Q'(SP)) could be used to characterize the removal factors of PAHs during atmospheric transport. All the observations proved that Q(SP) (and Q'(SP)) carry the information of gas-particlepartitioning and correlate with p(o)L.