Distribution and Health Risk Assessment of Cr⁶⁺ in Soil and Groundwater of a Chemical Plant

In order to clarify the Cr⁶⁺ pollution status and risk level of a chemical plant, 19 soil and groundwater sampling points were laid in the study area, and the content of Cr⁶⁺ was measured, to analyze the pollution characteristics and causes, and to carry out health risk assessment. The results showed that the excess rate of Cr⁶⁺ in topsoil (0~0.5 m) was 42.11%. In general, the Cr⁶⁺ concentration in soil decreased with the increase of depth, but it rose up near the groundwater level (15~20 m), which was mainly due to the long-term leaching effect that the pollutants migrated down to the aquifer and enriched. The excess rate of Cr⁶⁺ in shallow and deep groundwater was 73.68% and 37.50%, respectively. Overall, the Cr⁶⁺ pollution is not optimistic, and comprehensive water-soil treatment should be carried out. At the spatial scale the distribution of Cr⁶⁺ in topsoil was affected by human activities, and had a low correlation with the division of functional zones. And under the influence of hydrodynamic field, Cr⁶⁺ in groundwater is higher in the northwest than the southeast, and the center of the pollution plume has migrated downstream. In addition, the mean value of soil carcinogenic risk is 1.85×10⁻⁶, which is between 10⁻⁶ and 10⁻⁴, and the risk is moderate, which should be paid more attention to. Soil non-carcinogenic risk is less than 1 and doesn’t produce chronic toxic effects. Oral ingestion of soil was the main exposure route. The carcinogenic risk of groundwater is up to the order of 10⁻², much more than 10⁻⁴, which is unacceptable. The average non-carcinogenic risk is 51.62, much higher than 1, which may cause chronic toxic effects. In addition, the health hazards caused by Cr⁶⁺ entering the human body through the beef and mutton food chain should be further studied.