Chromium (Cr), particularly its hexavalent form Cr(VI), poses significant risks to agricultural productivity and ecosystem health. Highly responsive biomarkers are essential for improving Cr(VI) ecotoxicological assessments because they enable early detection of low-concentration exposure and sublethal effects often missed by traditional methods. This study demonstrates the critical role of intracellular β -glucosidase (I-BG) activity as a highly sensitive biomarker for Cr(VI) ecotoxicological assessment, outperforming conventional extracellular β -glucosidase ( E -BG) and total β -glucosidase (T-BG) measures. In a 90-day soil microcosm experiment with Cr(VI) spiking (0–50 mg kg 1 ), I-BG exhibited exceptional sensitivity, with EC 10 values as low as 0.068–0.136 mg kg 1 in Shandong (SD) soil and 0.346–0.609 mg kg 1 in Xinjiang (XJ) soil, 1–2 orders of magnitude lower than those for E -BG or T-BG. Incorporating I-BG data into species sensitivity distribution (SSD) models significantly refined risk thresholds, reducing hazardous concentration (HC 5 ) confidence intervals (XJ: 0.757–1.67 mg kg 1 ; SD: 0.507–0.956 mg kg 1 ) and improving sensitivity by 40–162% compared to models without I-BG. These findings establish I-BG activity as an indispensable parameter for advancing soil quality benchmarks and enabling high-resolution ecological risk assessments of Cr(VI) contamination in soil ecosystems. • Intracellular BG is more sensitive than extracellular BG to Cr(VI) pollution. • Cr(VI) inhibition kinetics are driven by soil type, rather than BG fraction. • Intracellular BG improves the sensitivity of SSD-derived Cr(VI) safety thresholds. • Short-term HC 5 : 0.507 0.757; Long-term HC 5 : 0.956 1.67 mg kg 1 for Cr(VI).
Yang et al. (Sun,) studied this question.