Biochars were studied for their impacts on the dissipation and vegetable uptake of polycyclic aromatic hydrocarbons (PAHs) in an agricultural soil. The health risks of PAHs taken up by vegetables were assessed by growing Chinese cabbage in both unamended soil and biochar-amended soils. In the unamended soil, the total 16 PAHs (Σ16PAHs) content decreased by 77.38% after planting the vegetable. The dissipation percentages of low-molecular-weight PAHs (LMW-PAHs), medium-molecular-weight PAHs (MMW-PAHs), and high-molecular-weight PAHs (HMW-PAHs) were 82.37%, 72.65%, and 68.63%, respectively. A significant negative correlation was determined between the dissipation percentages of PAHs in soil and the logKow of PAHs (p < 0.01), indicating that the affinity of PAHs for soil particles was one of an important limiting factors on the dissipation of PAHs. The uptake of PAHs by plant was significantly reduced with the increase in the molecular weight of the PAHs (76.55% for LWM-PAHs, 17.13% for MMW-PAHs, and 6.05% for HMW-PAHs). Addition of biochars to the soil decreased the dissipation of Σ16PAHs (73.59-77.01%), mostly due to a decrease in the dissipation of LMW-PAHs and MMW-PAHs. This finding was due to the immobilization of LMW-PAHs and MMW-PAHs within the biochar micropores. A marked reduction of Proteobacteria in biochar-amended soils also resulted in the decreased biodegradation of PAHs. Four of six biochars significantly increased the concentrations of Σ16PAHs in plant by 30.10-74.22%. Generally, biochars significantly increased the uptake of LMW-PAHs by plant but had little influence on the plant uptake of MMW-PAHs and HMW-PAHs. Three of six biochars notably increased the incremental lifetime cancer risk values based on the exposure of PAHs by vegetable consumption.

The occurrence of perfluorinated compounds (PFCs) in different environmental media in the QingHai-Tibet Plateau has been limitedly investigated. In this study, the water, sediments, soils and agricultural product samples were collected in the Huangshui River basin, and contents of the PFCs and values of water parameters were determined. This study investigated dominantly regulating factors of the distribution of PFCs in the water emphatically, explored the sources and assessed potential risks of the PFCs integrally. The results showed that perfluorohexanesulfonic acid, perfluorooctanesulfonic acid, perfluorobutanoic acid (PFBA) and perfluorooctanoic acid presented high maximum concentrations of 3207.42, 3015.96, 1941.89 and 826.4 ng L^-1 in the water, respectively. There were 12 PFCs detected in crops, with the maximum concentration of 5206.86 ng g^-1 for PFBA. The significantly positive correlation (p < 0.05) was observed between the concentrations of PFBA in crops and that in adjacent rivers, indicating that the irrigation most likely contributed to the accumulation of PFBA in the studied crops. The occurrence of the PFCs in the water during the dry season was dominantly regulated by fluorescent dissolved organic matters via the hydrophobic interaction, while it was primarily regulated by the total nitrogen and electrical conductivity via electrostatic interaction during the wet season. The PFCs in the water were mainly from the wastewater discharged from wastewater treatment plants and carpet factories, while the resuspension of the PFCs in sediments was also an important contribution especially in wet season. The PFCs in the river has posed sustained risk to the public health, especially children.

Lakes are a crucial component of the global carbon and nitrogen cycle. As a trend of enhanced human activities and climate change, the mechanisms of burial remain poorly understood. In this study, diverse biogeochemical techniques were applied to analyze the temporal variation of organic carbon and nitrogen burial rates in Chaohu Lake. The results showed that burial rates have ranged from 9.39 to 35.87 g C m⁻² yr⁻¹ for carbon and from 1.66 to 5.67 g N m⁻² yr⁻¹ for nitrogen since the 1860s. The average rates were 19.6 g C m⁻² yr⁻¹ and 3.14 g N m⁻² yr⁻¹ after the 1970s, which were significantly higher than the rate before the 1970s, showing an increasing trend. The decrease of C/N ratios as well as organic matter δ¹³C values indicates that the major organic matter source in sediment has been algal production since the 1970s. The increase of δ¹⁵N values indicated that the promotion in productivity was stimulated by nutrient input from sewage and agricultural runoff. The burial rates of organic carbon and nitrogen were significantly positively related to socio-economics and temperature, indicating that Chaohu Lake will become an increasing carbon and nitrogen pool under conditions of enhanced human activities and intensive precipitation.