Study on Retardation Factors of Cr(VI) Transport in Typical Soils of China

Chromium (VI) mobility in soils critically influenced groundwater contamination risks, but accurate predictions were hindered by the lack of systematic retardation factor (R) data across China's diverse soils. This study combined Bromide anion (Br^-)-tracer and Cr(VI) column leaching experiments with CXTFIT code to determine dispersion coefficients (D) and R values in seven representative Chinese soils (e.g., brown soil, black soil), with model validation against Br^- tracer data. By comparing deterministic equilibrium and two-region non-equilibrium models, the research demonstrated that the non-equilibrium approach better characterized Cr(VI) transport, revealing significant soil-dependent R variations (1.09-16.13). Particularly noteworthy was the exceptional Cr(VI) retention observed in Heilongjiang black soil (R > 10), which indicated strong immobilization capacity. As China's first systematic Cr(VI) retardation database, these findings provided essential parameters for predicting Cr(VI) mobility at contaminated sites, refining risk assessment models, and designing soil-specific remediation strategies-particularly crucial for high-retention regions. Methodologically, this work established an integrated experimental-modeling framework that addressed soil heterogeneity, while its outcomes directly supported regulatory frameworks through updated soil screening values. These findings provided scientific support for formulating region-specific soil management policies, with particular implications for environmental protection and agricultural safety in Cr(VI)-contaminated black soil regions.