A risk-based approach for the safety analysis of eight trace elements in Chinese flowering cabbage (Brassica parachinensis L.) in China

BACKGROUND Most countries set regulatory values for the total trace element (TE) concentrations in soil, although there is growing interest in using a risk-based approach to evaluate the bioavailable TE using dilute salt extractants or other soil parameters, including pH and organic carbon(.) The present study compares the current regulatory system (based on total TEs and pH) and a risk-based approach using 0.01 mol L-1 CaCl2 to estimate the bioavailable fraction. RESULTS In total, 150 paired samples of Chinese flowering cabbages (Brassica parachinensis) and their growth soils were collected, and the total and extractable concentrations of chromium (Cr), cadmium (Cd), lead (Pb), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As) and mercury (Hg), as well as soil pH and organic matter content, were measured. No more than 3.33% of the edible parts exceeded Chinese food safety standards, even when growing in soils exceeding the current regulatory thresholds by over 50%. The total soil Cd (1.5 mg kg(-1)), as well as the extractable concentrations of Cd (0.1 mg kg(-1)), Ni (0.03 mg kg(-1)) and Zn (0.1 mg kg(-1)), are the key factors affecting the TE concentrations in B. parachinensis. CONCLUSION Our findings suggest that the current soil regulatory guidelines for safe production of B. parachinensis are overly strict and conservative. A risk-based approach based on the extractable TE concentrations would provide a better indication for plant uptake of soil TEs and avoid the waste of farmlands that can still produce safe vegetables. Future research should focus on providing crop-specific available TE concentration guidelines to promote effective utilization of farmlands. (c) 2021 Society of Chemical Industry

Automated summary

The study compared the current regulatory system based on total trace element concentrations and pH with a risk-based approach using 0.01 mol L-1 CaCl2 to estimate the bioavailable fraction. The findings suggest that the current soil regulatory guidelines for safe production of Chinese flowering cabbages are overly strict and conservative, and a risk-based approach based on extractable TE concentrations would provide a better indication for plant uptake of soil TEs.