Assessing the influence of immobilization remediation of heavy metal contaminated farmland on the physical properties of soil

Abstract

The potential for negative effects of heavy metal remediation on the ecological environment of soil is an issue of widespread concern. As a basic index of soil moisture and fertility retention capacity, the response of the physical properties of soil to immobilization remediation is therefore extremely important and is the main focus of this study on remediated farmland in the mining area of Tangshi village, Henan province, China. Accordingly, topsoil samples and ring knife samples were collected from five separate farmland plots, four of which had been remediated with the respective soil amendments of 1) nano silica; 2) silicate, phosphate and clay minerals; 3) biochar and organic fertilizer; and 4) biochar and phosphate; whilst for experimental control purposes the 5th plot had no remediation measures. The physical properties of particle composition, bulk density, porosity and aggregate were subsequently determined. The results show that nano silica tends to refine the soil, mainly by significantly reducing the content of sand and increasing the content of silt and clay, but did not change the soil texture type. Furthermore, nano silica can promote the formation of soil macro-aggregates and reduce the content of micro-aggregates. However, the other three amendment compositions show no significant effect on soil particle composition and aggregate content. On the whole, the amendments of the four remediation plots can significantly reduce soil bulk density and increase porosity, thus facilitating soil changes that are more beneficial for crop growth. The results, therefore, go some way into alleviating the concerns surrounding heavy metal remediation and damage to the ecological environment of soil.