A field experiment on stabilization of Cd in contaminated soils by surface-modified nano-silica (SMNS) and its phyto-availability to corn and wheat

Abstract

Cd-contaminated soil is a common environmental problem. Stabilization is an effective way of in situ remediation for Cd contamination in soils, but there is a lack of information about the influences of the amendments on soil ecosystems and Cd uptake by crops, especially under field conditions. In this study, surface-modified nano-silica (SMNS) was used to stabilize a Cd-contaminated soil under field condition within one year. SMNS was mixed with Cd-contaminated soil at the dosage of 0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1%, respectively. After that, corn and wheat were sown within one year. DTPA extraction and sequential extraction were used to evaluate stabilization efficiency of SMNS to Cd. The influences of SMNS on crop yield, soil enzyme activities, and Cd accumulation in crops were also analyzed. The DTPA-extractable Cd in soil was reduced by 61.14% when the dosage of SMNS was 1%. SMNS transferred Cd to more stable fractions, with the organic-bound and residual Cd increased 148.11% and 90.52%, respectively. The addition of SMNS decreased soil dehydrogenase slightly, but its influences on soil urease, catalase, and yields of corn and wheat were negligible. More importantly, at the dosage of 1%, SMNS reduced 42.87% and 47.95% of Cd contents in corn and wheat grains, respectively. SMNS was effective in reducing the mobility of Cd in contaminated soils. These results suggest that SMNS has a great potential in the remediation of Cd-contaminated agricultural soils.