Factors affecting distribution and ecological risk assessment of volatile organic compounds (VOCs) in groundwater of the Huazhou district in northwestern China

Volatile organic compounds (VOCs) pollution in groundwater is a significant global concern. In this study, 26 groundwater samples were collected from the unconfined aquifers in Huazhou District, northwestern China, to assess their distribution characteristics, influencing factors, and ecological risks across various geomorphological settings. The findings revealed 35 VOCs in collected groundwater samples, with aromatic hydrocarbons having the highest detection rate (100%), and the VOCs distribution exhibited significant spatial variations, with the highest VOCs concentration near a chemical plant on the inclined pluvial plain. The lithology and groundwater flow influenced the vertical and lateral transport of VOCs, with concentrations decreasing as the aquifer permeability decreases along the groundwater flow from the inclined pluvial plain to the river. The Mantel test was used to analyze the correlation between VOCs and environmental factors, geochemical analyses indicated that nitrate (NO3−) and sulfate (SO42−) served as electron acceptors in the anaerobic biodegradation of organic pollutants, with bicarbonate (HCO3−) levels increasing as a result of this biodegradation. Additionally, the curved streamline searchlight shaped model (CS-SLM) was applied to identify the primary land use types affecting VOCs content, construction land and cropland were primary land use types affecting VOCs distribution. Finally, the ecological risk assessment indicated the highest risk quotient (RQ) for styrene (0.21), suggesting a manageable risk level. The study emphasizes the complexity of VOCs contamination in groundwater, providing a foundation for targeted mitigation strategies. [Display omitted] •35 VOCs mainly include aromatic/chlorinated, impacted by industry in the pluvial plain.•Topography, permeability, vadose thickness, and flow directed VOCs migration.•Biodegradation indicators (NO3− and SO42−) indicated the natural attenuation of VOCs.•Styrene and TCE had moderate ecological risk and the total risk was manageable.