Polycyclic Aromatic Hydrocarbons In Agricultural Soils Research Articles

Persistent polycyclic aromatic hydrocarbons removal from sewage sludge-amended soil through phytoremediation combined with solid-state ligninolytic fungal cultures

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment, causing increasing concern because of their impact on soil health, food safety and potential health risks. Four bioremediation strategies were examined to assess the dissipation of PAHs in agricultural soil amended with sewage sludge over a period of 120 days: soil-sludge natural attenuation (SS); phytoremediation using maize (Zea mays L.) (PSS); mycoremediation (MR) separately using three white-rot fungi (Pleurotus ostreatus, Phanerochaete chrysosporium and Irpex lacteus); and plant-assisted mycoremediation (PMR) using a combination of maize and fungi. In the time frame of the experiment, mycoremediation using P. chrysosporium (MR-PH) exhibited a significantly higher (P < 0.05) degradation of total PAHs compared to the SS and PSS treatments, achieving a degradation rate of 52 %. Both the SS and PSS treatments demonstrated a lower degradation rate of total PAHs, with removal rates of 18 % and 32 %, respectively. The PMR treatments showed the highest removal rates of total PAHs at the end of the study, with degradation rates of 48–60 %. In the shoots of maize, only low- and medium-molecular-weight PAHs were found in both the PSS and PMR treatments. The calculated translocation and bioconversion factors always showed values < 1. The analysed enzymatic activities were higher in the PMR treatments compared to other treatments, which can be positively related to the higher degradation of PAHs in the soil.

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.

Effects of spent mushroom substrate on the dissipation of polycyclic aromatic hydrocarbons in agricultural soil

Spent mushroom substrate (SMS) is an agricultural waste with a high potential for polycyclic aromatic hydrocarbons (PAH) removal in aged contaminated soils. In this study, fresh and air-dried Pleurotus ostreatus, Pleurotus eryngii, and Auricularia auricular SMSs were used to remove PAHs in agricultural soil under 60-day incubation. The potential of SMS in PAH dissipation was studied by detecting the dissipation rate and the soil physicochemical index, enzyme activity, PAH-degradation bacterial biomass, and microbial diversity. Results showed that SMS significantly enhanced the dissipation of PAHs and fresh SMS had a better effect than air-dried SMS. The highest dissipation rate of 16 PAHs was 34.5%, which was observed in soil amended with fresh P. eryngii SMS, and the PAH dissipation rates with low and high molecular weights were 41.3% and 19.4%, respectively. By comparison, fresh P. eryngii SMS presented high nutrient contents, which promoted the development of PAH-degrading bacteria and changed the soil bacterial community involved in degradation, thereby promoting the PAH dissipation. The lignin-degrading enzymes in fresh SMS were abundant, and the laccase and manganese peroxidase activities in the treatment of fresh P. eryngii SMS was higher than those in other treatments. Fresh P. eryngii SMS improved the relative abundance of Microbacterium, Rhizobium, and Pseudomonas in soil, which were all related to PAH degradation. Consequently, adding fresh P. eryngii SMS was an effective method for remediating aged PAH-contaminated agricultural soils.

Assessment of Polycyclic Aromatic Hydrocarbons in Agricultural Soils of Teskelewu Community and Environs Impacted By Gas Flaring in Delta State, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are emerging ubiquitous environmental pollutants with reported carcinogenic, mutagenic and teratogenic potentials on living organisms and humans. The objective of this study was to assess the concentrations of PAHs in agricultural soils of Tsekelewu Community and environs (Egbema Kingdom) in Warri North Local Government Area of Delta State, Nigeria impacted by gas flaring using gas chromatograph system Agilent 5890 Series 11 gas chromatograph equipped with Flame ionization detector (GC-FID). The results revealed that station 1 and 2 were fairly contaminated; with mean total PAH concentration of 236.40 μg/kg and 279.75 μg/kg respectively. Stations 3, 4, 6, 7 and 9 having mean total PAH concentration of 692.45μg/kg, 726.22 μg/kg, 739.82 μg/kg, 609.38 μg/kg, and 772.99 μg/kg were moderately contaminated. Heavy contamination was recorded in station 5 and station 8 with mean PAH concentrations of 1231.08μg/kg and 1224.33 μg/kg. The dominant PAHs in soil samples were benzo(a)anthracene, phananthrene and chrysene with benzo(a)anthracene having the highest concentration across all sample stations. The PAH concentration observed in this study is thus a serious cause for concern since soil contamination from gas flaring will likely continue. Measures that will attenuate PAHs concentrations in soil should be adopted as farmers are likely exposed by largely inhalation.Keywords: Hydrocarbons; Contamination; Agricultural soils; Gas flaring

Polycyclic Aromatic Hydrocarbons in Sediments/Soils of the Rapidly Urbanized Lower Reaches of the River Chaohu, China.

Polycyclic aromatic hydrocarbons (PAHs) are highly teratogenic, persistent carcinogens, and ubiquitous environmental pollutants. To determine the impact of rapid urbanization on sediment/soil PAHs, we collected 30 cm soil cores in ditch wetlands, riverine wetlands, and agricultural lands along the lower reaches of the Shiwuli River feeding Chaohu Lake, China. Ecological risk effects were evaluated by two models based upon Benzo[a]pyrene toxic equivalency (TEQ-BaP) and total toxic units (TUs). The presence of PAHs, such as BbF, BkF, InP, and BgP, that are known pollutants of concern, suggests certain ecological risks. The concentration of PAHs in the surface layer followed in the order of: ditch wetlands (617.2 ng/g average), riverine wetlands (282.1 ng/g average), agricultural lands (103.7 ng/g average). PAHs in ditch sediments were vertically distributed evenly, and PAHs in agricultural soils were concentrated in the surface soil. In riverine wetland sediments, the 2-, 3-, and 4-ring PAHs had a uniform distribution, whereas the 5- and 6-ring PAHs were concentrated in the surface soil. Redundancy analysis (RDA) explored the correlation between the environmental properties and the occurrence of PAHs. Total organic carbon (p = 0.010), percent clay (p = 0.020), and distance (p = 0.020) were the primary factors in ditch wetlands. Depth (p = 0.010) and distance (p = 0.006) were the main factors in agricultural lands. There were no significant correlations in riverine wetlands. The correlation between the distance from the built-up urban areas and pollutant concentration showed that the closer the distance, the greater the concentration of PAHs.

A PAH-degrading bacterial community enriched with contaminated agricultural soil and its utility for microbial bioremediation

A bacterial community was enriched with polycyclic aromatic hydrocarbons (PAHs) polluted soil to better study PAH degradation by indigenous soil bacteria. The consortium degraded more than 52% of low molecular weight and 35% of high molecular weight (HMW) PAHs during 16 days in a soil leachate medium. 16S rRNA gene high-throughput sequencing and quantitative polymerase chain reaction analyses for alpha subunit genes of ring-hydroxylating-dioxygenase (RHDα) suggested that Proteobacteria and Actinobacteria at the phylum level, Pseudomonas, Methylobacillus, Nocardioides, Methylophilaceae, Achromobacter, Pseudoxanthomonas, and Caulobacter at the generic level were involved in PAH degradation and might have the ability to carry RHDα genes (nidA and nahAc). The community was selected and collected according to biomass and RHDα gene contents, and added back to the PAH-polluted soil. The 16 EPA priority PAHs decreased from 95.23 to 23.41 mg kg−1 over 35 days. Compared with soil without the introduction of this bacterial community, adding the community with RHDα genes significantly decreased soil PAH contents, particularly HMW PAHs. The metabolic rate of PAHs in soil was positively correlated with nidA and nahAc gene contents. These results indicate that adding an indigenous bacterial consortium containing RHDα genes to contaminated soil may be a feasible and environmentally friendly method to clean up PAHs in agricultural soil.

Polycyclic aromatic hydrocarbons (PAHs) in agricultural soils from Ningde, China: levels, sources, and human health risk assessment.

Soil-bound polycyclic aromatic hydrocarbons (PAHs) in farmland are critical to human health. The level, composition, source, and cancer risk of sixteen PAHs in agricultural soil from Ningde, China, were investigated. The results indicated that the total concentrations of 16 PAHs ranged from 77.3 to 1188ngg-1, with a mean value of 406ngg-1. Five-ring PAHs were found to have the highest concentrations (148 ± 133ngg-1), followed by four-ring (120 ± 101ngg-1), three-ring (61.9 ± 54.2ngg-1), six-ring (44.6 ± 61.0ngg-1), and two-ring (31.3 ± 31.0ngg-1). Employing positive matrix factorization (PMF), four PAH sources including biomass burning (36.3%), coal combustion (35.5%), traffic emissions (16.4%), and coke source (11.8%) were identified. Incremental lifetime cancer risk (ILCR) results showed that ILCR values ranged from 7.1 × 10-4 to 1.1 × 10-3, which will cause moderate-to-high cancer risk to human health mainly via the soil ingestion and dermal contact exposure pathways. The source-oriented results indicated that coal combustion (32.7%), traffic emission (34.3%), and biomass burning (32.4%) had similar contributions to the total cancer risk. Therefore, more attention should be paid to these pyrolysis-originated sources to protect humanity from the health risk of PAHs.

Contamination, source identification, and risk assessment of polycyclic aromatic hydrocarbons in agricultural soils around a typical coking plant in Shandong, China

ABSTRACTCoking is one of the most important emission sources of polycyclic aromatic hydrocarbons (PAHs) in China. Investigation of the contamination, distribution, and sources of PAHs in agricultural soils around Rong Xin coking plant, China, was conducted, and the potential human health risks were addressed. The total concentration of the 16 PAHs (∑16PAHs) on the United States Environmental Protection Agency priority list had a range from 1774 to 4621 µg/kg (mean 3016 µg/kg). Meanwhile, seven carcinogenic PAHs (∑PAH7c) owned the total concentrations of 684–2105 µg/kg, and they had the benzo[a]pyrene equivalent (BaPeq) concentrations at 139.616–1672.850 µg/kg. All soil samples were dominated by PAHs with two to four rings. Data analyses for the potential sources of PAHs showed that the PAHs in soils were principally from pyrogenic sources. Ecological risk assessment of soil PAHs showed that the BaPeq concentrations of ∑PAH7c accounted for 99% of the total ∑16PAHs, being a major carcinogenic contributors of ∑16PAHs. Higher levels of PAHs and higher total BaPeq concentrations in this study indicate a potential carcinogenic risk for humans. Therefore, long-term exposure to coking plants may increase the PAH concentrations in the environment and further raise a potential risk to human health.

Occurrence of nitro- and oxy-PAHs in agricultural soils in eastern China and excess lifetime cancer risks from human exposure through soil ingestion

The quality of agricultural soil is vital to human health, however soil contamination is a severe problem in China. Polycyclic aromatic hydrocarbons (PAHs) have been found to be among the major soil contaminants in China. PAH derivatives could be more toxic but their measurements in soils are extremely limited. This study reports levels, spatial distributions and compositions of 11 nitrated (nPAHs) and 4 oxygenated PAHs (oPAHs) in agricultural soils covering 26 provinces in eastern China to fill the data gap. The excess lifetime cancer risk (ELCR) from the exposure to them in addition to 21 parent PAHs (pPAHs) via soil ingestion has been estimated. The mean concentration of ∑nPAHs and ∑oPAHs in agricultural soils is 50±45μg/kg and 9±8μg/kg respectively. Both ∑nPAHs and ∑oPAHs follow a similar spatial distribution pattern with elevated concentrations found in Liaoning, Shanxi, Henan and Guizhou. However if taking account of pPAHs, the high ELCR by soil ingestion is estimated for Shanxi, Zhejiang, Liaoning, Jiangsu and Hubei. The maximum ELCR is estimated at ca.10−5 by both deterministic and probabilistic studies with moderate toxic equivalent factors (TEFs). If maximum TEFs available are applied, there is a 0.2% probability that the ELCR will exceed 10−4 in the areas covered. There is a great chance to underestimate the ELCR via soil ingestion for some regions if only the 16 priority PAHs in agricultural soils are considered. The early life exposure and burden are considered extremely important to ELCR. Emission sources are qualitatively predicted and for areas with higher ELCR such as Shanxi and Liaoning, new loadings of PAHs and derivatives are identified. This is the first large scale study on nPAHs and oPAHs contamination levels in agricultural soils in China. The risk assessment based on this underpins the policy making and is valuable for both scientists and policy makers.

Distribution, transfer, and health risks of polycyclic aromatic hydrocarbons (PAHs) in soil-wheat systems of Henan Province, a typical agriculture province of China

In order to investigate the distribution, transfer, and human health risks of polycyclic aromatic hydrocarbons (PAHs) in the soil-wheat systems, soil samples from 20 farmlands and corresponding wheat tissues were collected from selected regions of Henan Province in June 2013 and were analyzed to estimate the concentration of PAHs. The total concentrations of 15 PAHs (∑15 PAHs) in soils from Henan Province varied from 6.91 to 72.4ng/g. Moreover, two-ring to three-ring PAHs (1.59-29.1ng/g) were the major species in soils, occupying 56.2% of total PAHs. Principal component analysis (PCA)-multiple linear regression (MLR) revealed that fossil fuel burning dominated the input of PAHs in agricultural soils of Henan Province. The range of ∑15 PAHs concentrations in wheat tissues was 13.9-50.9ng/g, which decreased along the root-straw-grain. Positive correlation among PAHs of soil and wheat tissues showed that PAHs in wheat mainly came from soil and then migrated along root-straw-grain. Moreover, PAHs were accumulated highest in root and lowest in grain. Two-ring to three-ring PAHs were easier to transfer from soil to wheat than five-ring to six-ring PAHs. Consumption of wheat grain created potential risk of cancer in Henan Province.

Occurrence and geographic distribution of polycyclic aromatic hydrocarbons in agricultural soils in eastern China.

Polycyclic aromatic hydrocarbons (PAHs) in agricultural soils, eastern China, were studied through a collection of surface samples at 109 sites. The study covered US EPA priority pollutants but also several non-priority isomers including some dibenzopyrenes which are expected to have higher toxic potentials. The total PAH concentrations varied extensively from 8.8 to 3880μg/kg, with a geometric mean of 158μg/kg. There were significant differences in both the concentrations and composition profiles between the south and the north regions. The overall geographical distribution pattern was strongly influenced by both the per capita gross domestic product and soil organic carbon (SOC) content. The former is an indicator of anthropogenic emissions while soil SOC content is associated with the accumulative capacities of the soils. The sequestration mechanism is an important process controlling fates of PAHs in agricultural soil.

Bioremediation of PAH-contaminated farmland: field experiment.

The agricultural soil contaminated by polycyclic aromatic hydrocarbons (PAHs) is gradually emerging and becoming serious in China with the rapid development of economy. To reduce the risk of PAHs in agricultural soil and guarantee the food safety, the biological agent that Mycobacterium gilvum immobilized on modified peanut shell powder enhanced remediation of polycyclic aromatic hydrocarbon-contaminated vegetable farmland was investigated under the conditions of the field experiment. The results indicated that adding biological agent could promote PAH degradation in the soil, especially high-ring PAHs. The degradation rates of PAHs in the soil could be further improved to 16.5-43.5%, respectively, compared with the soil without the biological agent. Adding the biological agent could significantly improve soil dehydrogenase activity and microbial diversity. It also could reduce the enrichment of PAHs in mustard planted in the polluted field, which indicated that the biological treatments might be less ecological risk. The work suggested that adding the biological agent might be a promising in situ bioremediation strategy for PAH-contaminated farmland field.

Ecological and health risk-based characterization of agricultural soils contaminated with polycyclic aromatic hydrocarbons in the vicinity of a chemical plant in China

Polycyclic aromatic hydrocarbons (PAHs) from chemical plants can cause serious pollution of surrounding agricultural soils. A comprehensive study of agricultural soils was conducted in the vicinity of a chemical plant in China to characterize the soil PAH concentration, as well as their composition and sources. Human health and a screening–level ecological risk assessment were conducted for PAH contamination in agricultural soils. The results showed that the total concentrations of 16 priority PAHs ranged from 250.49 to 9387.26 ng g−1, with an average of 2780.42 ng g−1. High molecular weight PAHs (four to six rings) were the dominant component, accounting for more than 60% of all PAHs. Principal component analysis (PCA) and positive matrix factorization model (PMF) suggested that diesel emissions, coal combustion, coke ovens, and fuel combustion and gasoline emissions were the main sources of PAHs in agricultural soils. The ecological risk assessment results based on the effects range–low (ERL), the effects range–median (ERM), and the ecological screening levels (ESL) indicated that the exposure to ∑PAH16 was >ERL, >ERM, and ≥ERL and <ERM at 21.9, 0, and 21.9% of the soil sampling stations, the exposure to ∑PAH16 was >ESL at 78.1% of the soil sampling stations, and could induce biological effects in mammals. The Bapeq concentrations posed a potential carcinogenic risk to humans. Further risk management and control of soil PAHs in these agricultural soils is required to ensure the safety of the biocoenosis and human health.

GammaProteobacteria as a potential bioindicator of a multiple contamination by polycyclic aromatic hydrocarbons (PAHs) in agricultural soils

The impact of a multiple contamination by polycyclic aromatic hydrocarbons (PAHs) was studied on permanent grassland soil, historically presenting low contamination (i.e. less than 1 mg kg−1). Soil microcosms were spiked at 300 mg kg−1 with either single or a mixture of seven PAHs. While total dissipation of the phenanthrene was reached in under 90 days, only 60% of the PAH mixture were dissipated after 90 days. Interestingly, after 30 days, the abundance of the GammaProteobacteria class (assessed by qPCR) become significantly higher in microcosms spiked with the PAH mixture. In addition, the specific abundance of the cultivable Pseudomonas spp., which belong to the GammaProteobacteria class, increased earlier and transiently (after 8 days) in the microcosms spiked with the PAH mixture. Consequently, we propose to use the GammaProteobacteria as a bioindicator to detect the impact on the bacterial community of a multiple contamination by PAHs in agricultural soils.

An approach to uncertainty estimation in determining polycyclic aromatic hydrocarbons in fuel-contaminated soils

An estimation of uncertainty contribution in the entire set of the analytical data of polycyclic aromatic hydrocarbons (PAHs) in soil during a full year is presented. The analyses were performed as part of a project devoted to the assessment of the natural attenuation of selected PAHs in agricultural soil contaminated by a fuel spill. In particular, we investigated the effect of natural attenuation on the PAH dissipation rate in plots of two types of scenarios in agricultural soils. One of them was previously affected by an accidental fuel spill 10 years ago, and the other one was non-affected. The major components for estimating uncertainty contributions have been evaluated based on intermediate precision from different levels of PAH mass fraction, sample locations, and long term data set. An analysis of variance (ANOVA) test was applied to the mass fractions of clean or blank soil sub-samples versus contaminated soil sub-samples for grouping comparable data. Variables of influence in this study were site, month, and lysimeter of sampling (referring to a stainless steel box, with side lengths of 50 cm). Study sites or the spatial arrangement of lysimeter showed a clear effect in sub-sample results with the lowest mass fraction levels for heavier PAH, while monthly sampling was the variable of most significant influence for the more strongly contaminated sub-sample results. Finally, the results of the PAH mass fractions in contaminated soil sub-samples indicated a monthly variation for which lighter, volatile PAHs rapidly decreased while the less volatile did not change.

The health risk of the agricultural production in potentially contaminated sites: an environmental-health risk analysis

Rural areas are often interested by pollution phenomena generated by agricultural activities with a high use of pesticides and/or by anthropic activities, such as industrial plants or illegal waste disposal sites, which may cause even long-range contamination. The risk for human health from the pollutants present in the environment can be quantitatively evaluated by the environmental health risk analysis set out in the Italian Legislative Decree no. 152/2006 (Italian Regulation, 2006). This analysis is the best technical-normative tool to estimate the health risks linked to the pollutants present in the environment but it does not consider the specificity of agricultural soils or the contamination of agricultural products. This study aims to provide this missing technical-normative data by identifying and applying a suitable methodology to evaluate the health risk caused by the ingestion of agricultural products grown in contaminated soils. The risk analysis was applied to two contaminated areas in southern Italy using an innovative methodology based on widely accepted parameters for the determination of polycyclic aromatic hydrocarbons (PAHs) soil-plant bio-transfer factor in the case of horticultural crops. In addition, some concentration limits of PAHs in agricultural soils are proposed that may be of help to the competent authorities (health agencies, local authorities) in delineating the areas requiring strict health surveillance of the food products cultivated.

The health risk of the agricultural production in potentially contaminated sites: an environmental-health risk analysis

Rural areas are often interested by pollution phenomena generated by agricultural activities with a high use of pesticides and/or by anthropic activities, such as industrial plants or illegal waste disposal sites, which may cause even long-range contamination. The risk for human health from the pollutants present in the environment can be quantitatively evaluated by the environmental health risk analysis set out in the Italian Legislative Decree no. 152/2006 (Italian Regulation, 2006). This analysis is the best technical-normative tool to estimate the health risks linked to the pollutants present in the environment but it does not consider the specificity of agricultural soils or the contamination of agricultural products. This study aims to provide this missing technical-normative data by identifying and applying a suitable methodology to evaluate the health risk caused by the ingestion of agricultural products grown in contaminated soils. The risk analysis was applied to two contaminated areas in southern Italy using an innovative methodology based on widely accepted parameters for the determination of polycyclic aromatic hydrocarbons (PAHs) soil-plant bio-transfer factor in the case of horticultural crops. In addition, some concentration limits of PAHs in agricultural soils are proposed that may be of help to the competent authorities (health agencies, local authorities) in delineating the areas requiring strict health surveillance of the food products cultivated.

Occurrence and Fate of Organochlorinated Pesticides and PAH in Agricultural Soils from the Ebro River Basin

This study was aimed to assess the presence and fate of 22 organochlorinated pesticides (OCHs) and their degradation products and 16 Environmental Protection Agency-priority polycyclic aromatic hydrocarbons (PAHs) in soils of the Ebro River basin (NE Spain) during a 3-year period. The study site is characterized by a long and active agricultural history where pesticides have largely been used. Soils were extracted using pressurized liquid extraction followed by gas chromatography-mass spectrometry. This procedure was optimized in terms of multiresidue analysis and effective cleanup and proved to have excellent analytical performance (recoveries ranging between 71% and 133%, standard deviation <14%, and a method detection limit from 0.19 to 7.38 microg/kg). Soils form the Ebro basin showed a prevalence of 4,4'-DDT and 4,4'-DDE, found in 53% and 88% of the soil samples between 0.13 and 58.17 microg/kg-dw (dry weight), respectively, indicating a slight decreasing trend of DDT within time. PAHs were detected in all soil samples at concentrations up to 465 microg/kg-dw, and the phenanthrene/anthracene (<10) and fluoranthene/pyrene (>1) ratios indicated combustion processes as the main source attributing to the burning of weeds and vegetable wastes after harvesting. No traces of any of the OCHs and PAHs were detected in groundwater, indicating that leaching for agricultural fields is not an important process of transport for these compounds. Overall, we propose the need to perform a monitoring program to evaluate the temporal tendencies and potential impact of pesticides and PAH in soils.

Pollution assessment, distribution and sources of PAHs in agricultural soils of Pearl River Delta—The biggest manufacturing Base in China

A large scale of soil survey was performed to determine the contents, distributions and sources of 16 polycyclic aromatic hydrocarbons (PAHs) in 231 agricultural soils under 3 land-use types from 5 regions of the subtropical Pearl River Delta (PRD). The average sum of 16 PAHs in all soil samples is 316.5 μ g.kg−1, with range from ND to 4079 μg.kg−1. Three- and 4-ring PAHs are the most abundant PAHs that contribute to 73.0% of total contents. The most abundant components are phenanthrene, benzo(b)fluoranthene and fluoranthene. ANOVA and principal component analyses (PCA) indicate that soil samples from Dongguan and Zhongshan contain greater PAHs than other regions. More abundant carcinogenic and higher molecular weight PAHs accumulated in soils from Dongguan and Zhongshan, while higher low molecular weight PAHs were in soils from Guanghzou, Huizhou and Shunde. Soil PAHs from 3 land uses are not statistically different. Additionally, 5 PAH compound ratios suggest that soil PAHs in PRD derived from mixture of pyrogenic and petrogenic sources, but the majorities are pyrogenic sources. PAHs were further identified as mixture of petroleum combustion and grass, wood, and coal combustion. Some soil PAHs were revealed vehicle emission, coal soot and petroleum sources. The 5 regions showed different PAHs sources according to some compound ratios, but no marked distinction between regions from 2 banks of the Pearl River because of major wind direction, distribution of riverway and industry.

The concentrations, distribution and sources of PAHs in agricultural soils and vegetables from Shunde, Guangdong, China

The concentrations, distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in 30 agricultural soil and 16 vegetable samples collected from subtropical Shunde area, an important manufacturing center in China. The total PAHs ranged from 33.7 to 350 microg/kg in soils, and 82 to 1,258 microg/kg in vegetables. The most abundant individual PAHs are phenanthrene, fluoranthene, chrysene, pyrene and benzo(b)fluoranthene for soil samples, and anthracene, naphthalene, phenanthrene, pyrene and chrysene for vegetable samples. Average vegetable-soil ratios of total PAHs were 2.20 for leafy vegetables and 1.27 for fruity vegetables. Total PAHs in vegetable samples are not significantly correlated to those in corresponding soil samples. Principal component analyses were conducted to distinguish samples on basis of their distribution in each town, soil type and vegetable specie. Relatively abundant soil PAHs were found in town Jun'an, Beijiao, Chencun, Lecong and Ronggui, while abundant vegetable PAHs were observed in town Jun'an, Lecong, Xingtan, Daliang and Chenchun. The highest level of total PAHs were found in vegetable soil, followed by pond sediment and "stacked soil" on pond banks. The PAHs contents in leafy vegetables are higher than those in fruity vegetables. Some PAH compound ratios suggest the PAHs derived from incomplete combustion of petroleum, coal and refuse from power generation and ceramic manufacturing, and paint spraying on furniture, as well as sewage irrigation from textile industries. Soil PAHs contents have significant logarithmic correlation with total organic carbon, which demonstrates the importance of soil organic matter as sorbent to prevent losses of PAHs.