Spatio-vertical characterization of the BTEXS group of VOCs in Chinese agricultural soils

Ubiquitous contamination of the BTEXS (benzene, toluene, ethylbenzene, xylene, and styrene) group in soils is a significant concern for ecological safety. However, comprehensive spatio-vertical survey of the BTEXS group on a national scale is rare to date. Using a static headspace gas chromatography-mass spectrometry method (HS-GCMS), this study performed a quantitative analysis of BTEXS levels in soils from Chinese rural areas in 2013 and 2016. The median Sigma BTEXS concentrations in surface soils in 2013 and 2016 were 37.5 and 34.4 ng g(-1) dry weight, respectively. Toluene was the dominant pollutant, accounting for approximately 41.6% and 32.1% of the total levels. BTEXS contamination was higher in Shanxi province, Northeast China, and Yunnan-Guizhou Plateau compared to the other regions. Vertically, toluene, m,p'-xylene and o'-xylene concentrations were significantly higher in the top soil layer (0-15 cm) and decreased significantly with increasing soil depth (p < 0.05). Higher soil organic matter was significantly associated with higher BTEXS concentrations of sampling site. BTEXS was also enhanced at sites with higher elevations and lower temperature due to global distillation effects. The findings of this study could help decision-makers to protect against BTEXS contamination in rural areas. These findings provide a basis for further study of the mechanism of BTEXS migration and transport in large-scale environment. Capsule: Spatio-vertical distribution, influence factors, exposure risks of BTEXS in soils from Chinese agricultural region was studied. (C) 2019 Elsevier B.V. All rights reserved.