The toxicity assessment of chromium in Beijing Kaleyard Alluvial Soil-Pakchoi System

Abstract

In this study,pot experiments using the Beijing alluvial soils were conducted to examine the effects of hexavalent chromium(Cr),concentrations ranging from 0 to 50 mg·kg-1,on the biomass and Cr concentrations of pakchoi(Brassica chinensis L.),soil microbial biomass carbon,soil microbial biomass nitrogen and soil microbial respiration.The results showed that in the high Cr concentration treatments(with addition ≥25 mg·kg-1),the Cr concentrations in pakchoi leaves increased significantly compared with the control treatment(P0.01).The total Cr concentrations in pakchoi roots were much greater than those in leaves.Compared with the control treatment,the biomass of pakchoi leaf increased significantly in the 1 mg·kg-1 Cr treatment,while its biomass decreased significantly in the high Cr concentration treatments(≥10 mg·kg-1)(P0.01) and the highest decreasing extent was up to 78.2%.In the 50 mg·kg-1 Cr treatment,the soil microbial biomass carbon,microbial biomass nitrogen and respiration rate were significantly lower than these indicators of control treatments.The biomass and total Cr concentration of pakchoi leaves,soil microbial biomass carbon,soil microbial biomass nitrogen and soil microbial respiration rate could all be sensitively served as biological indicators to reflect the pollution extent of soil Cr.By using these indicators and the corresponding total Cr concentrations of soil,we could obtain the fitting equations.Based on the conceptions of crop yield reduction,food safety and ecological dose,we could calculate the Cr mild pollution critical concentration of Beijing alluvial soil ED10(70.8 mg·kg-1) and the Cr moderate pollution critical concentration of Beijing alluvial soil ED50(111.6 mg·kg-1).The results would be helpful to the revision and rebuilding of soil environmental criteria.