Evaluation the Influence of Soil Solution Chemistry on Soluble Nickel Toxicity to Bok Choy

Abstract

Nickel (Ni) is an essential element for plants but it is toxic at large concentrations. In the present study, bioassays of bok choy were taken in 17 Chinese soils with different properties and climate characteristics to evaluate the toxicity of soil soluble nickel (Ni) toxicity in soil pore water to bok choy. The tested soils were spiked with 8 levels of soluble Ni chloride with or without leaching treatments. The effective soluble Ni concentrations that caused 10% root growth inhibition (EC10) and 50% inhibition (EC50) varied widely from 0.05 to 2.1 mg/L and from 0.13 to 7.6 mg/L in 17 unleached soils, represented 41.8 to 58.5 folds differences, and from 0.08 to 2.2 mg/L and from 0.47 to 4.5 mg/L in leached soils, represented 27 to 9.6 folds differences. It indicated that the soil soluble properties greatly influenced Ni toxicity to bok choy. However, soluble Ni toxicity thresholds were not significantly decreased in 15 soils. Regression models between soil solution properties and phytotoxicity threshold values were developed. The model showed that soil solution Mg2+K+and electrical conductivity (EC) were the important factors affecting Ni toxicity on bok choy, and meanwhile they were positively related to the toxicity thresholds. These quantitative relationships could be used for the risk assessment of Ni in terrestrial environment in China.