Distribution, sources, and risk assessment of polycyclic aromatic hydrocarbons in surface soils and plants from industrial and agricultural areas, Junggar Basin, Xinjiang.

The contamination characteristics of Polycyclic Aromatic Hydrocarbons (PAHs) in different environmental functional areas are different. In this study, the contamination of PAHs in soils and common plants in typical mining and farmland areas in Xinjiang, China, was analyzed. The results showed that the contamination levels of PAHs in mining soils were significantly higher than those in farmland soils, and the mining soils were dominated by 4-5-ring PAHs and farmland soils by 3-4-ring PAHs. Analysis of their sources using a positive definite factor matrix model showed that PAHs in mining soils mainly originated from coal and natural gas combustion, and transportation processes; while farmland soils mainly came from biomass and coal combustion, and fossil fuel volatile spills. The cancer risk of PAHs in soils was evaluated using a combination of the Monte Carlo and the lifetime carcinogenic risk models, and the results showed that the overall level of cancer risk for mining soils was higher than that for farmland soils, and can put some people in high risk of cancer. For plant samples, except for individual crop samples, the contamination levels of mining plants and crops were similar, with 4-5-ring PAHs dominating in desert plants in mining areas and the highest proportion of 3-ring PAHs in crops in agricultural fields, and PAHs in both plants were mainly from biomass and coal combustion. The results of correlation analysis showed that 2-ring PAHs in crop roots were significantly positively correlated with it in corresponding soils, and some high-ring PAHs in crop leaves were significantly negatively correlated with it in corresponding soils. Therefore, there were significant differences in the pollution characteristics of PAHs in soils and common plants in mining and agricultural areas. Human health risks and ecological risks are mainly concentrated in mining areas, and appropriate intervention measures should be taken for pollution remediation.

[Pollution Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons in Farmland Soil and Crops in the Suburbs of Urumqi].

In order to understand the occurrence of PAHs in soil and crops, the enrichment capacity of different crops for PAHs, and the distribution characteristics of PAHs in different parts of crops, the crops and soil planted in the farmland around Urumqi were studied as examples. Samples were collected in the farmland gathering area in the suburb of Urumqi in July 2021. A total of 100 crop samples were collected, including 21 crop species and 45 surface soil samples. The results showed that 16 types of PAHs were detected in the soil and crops. The total concentration of PAHs in farmland soil ranged from 19.06 to 1870.86 µg·kg-1, and the average concentration was 127.40 µg·kg-1. Seven carcinogenic PAHs accounted for 42.85%-79.20% of the 16 types of PAHs, among which BaP was the main pollutant in the soil. Through the characteristic ratio method, it was found that the main sources of PAHs in the soil were biomass and coal combustion. Total PAHs in crops ranged from 1.86 µg·kg-1 to 974.05 µg·kg-1, with an average of 303.30 µg·kg-1. Different crops had different enrichment capacities for PAHs. Among the 21 crops sampled, the accumulative content of PAHs in pumpkin was the highest (431.75 µg·kg-1). In leaf vegetable crops, the content of PAHs in leaves was higher than that in roots and fruits. In fruit and vegetable crops, the PAH content in fruit was higher than that in the root or leaf. There was a significant correlation between high cyclic PAHs in soil and PAHs in plant leaves. The health risk assessment of PAHs in crops showed that dietary intake had potential carcinogenic risk and even had high carcinogenic risk in adult male and female groups, which requires further attention.

Removal of chloramphenicol and resistance gene changes in electric-integrated vertical flow constructed wetlands.

The performance of an electric-integrated vertical flow constructed wetland (E-VFCW) for chloramphenicol (CAP) removal, changes in microbial community structure, and the fate of antibiotic resistance genes (ARGs) were evaluated. CAP removal in the E-VFCW system was 92.73% ± 0.78% (planted) and 90.80% ± 0.61% (unplanted), both were higher than the control system which was 68.17% ± 1.27%. The contribution of anaerobic cathodic chambers in CAP removal was higher than the aerobic anodic chambers. Plant physiochemical indicators in the reactor revealed electrical stimulation increased oxidase activity. Electrical stimulation enhanced the enrichment of ARGs in the electrode layer of the E-VFCW system (except floR). Plant ARGs and intI1 levels were higher in the E-VFCW than in the control system, suggesting electrical stimulation induces plants to absorb ARGs, reducing ARGs in the wetland. The distribution of intI1 and sul1 genes in plants suggests that horizontal transfer may be the main mechanism dispersing ARGs in plants. High throughput sequencing analysis revealed electrical stimulation selectively enriched CAP degrading functional bacteria (Geobacter and Trichlorobacter). Quantitative correlation analysis between bacterial communities and ARGs confirmed the abundance of ARGs relates to the distribution of potential hosts and mobile genetic elements (intI1). E-VFCW is effective in treating antibiotic wastewater, however ARGs potentially accumulate.

[Typical Pesticide Residues and Their Risk Assessment in Farmland Environment of Different Plant Types in Shaya County, Xinjiang].

In order to investigate the characteristics of typical pesticide residues in farmland soil of different plant types in Shaya County and to evaluate the level of human health risk and ecological risk caused by pesticide residues, a total of 55 samples of plants, soil, and water from nine areas of Shaya county were collected on September 29, 2020. The occurrence levels of 47 typical pesticides in the samples were analyzed using gas chromatography-mass spectrometry (GC-MS). The results showed that a total of 23 pesticides were detected in three environmental media, and the maximum concentrations of pesticides in soil, plants, and water were 70.58 µg·kg-1, 1832.18 µg·kg-1, and 188.53 µg·L-1, respectively. The levels of pesticide residues in the three environmental media in Shaya county were characterized as plants>water>soil. From the detection of pesticides in different plant types, P1, P2, P6, and P8 in the center of the county were the most seriously polluted. The plants with a high pesticide load level in the corresponding areas were cotton, walnut, red jujube, and poplar, and the pesticides with a high concentration contribution were hexachlorocyclohexanes, chlorpyrifos, cyhalothrin, fluvalinate, metalaxyl, difenoconazole, and procymidone. The human health risks of adults and children caused by oral intake, skin contact, and respiratory inhalation were evaluated. The results showed that oral intake was the main exposure route, and the risk level of children was significantly higher than that of adults but was within the acceptable range. The ecological risk level of earthworms in soil was subsequently evaluated. The results showed that the potential ecological risk level of a single pesticide was low, and the potential ecological risk level of bifenthrin was the largest. The calculation of the total ecological risk of mixed pesticides showed that areas P1, P4, P7, and P9 were at moderate risk, whereas other areas were at low risk. Therefore, the use of some pesticides in Shaya County should be restricted.