Chromium Fraction Transformation In Loess Soil Field And Effects On Maize Production

With the rapid development of social economy, the chromium pollution had become animportant form of heavy metal pollution in some suburban. Heavy metals in the environmentnot only can not be degraded, but also form much more toxic substances combined with theorganic matter. Materials chemical forms determine its bioavailability, toxicity, and theirmigration and enrichment in the environment.The soil is an important area of heavymetals’bioaccumulation so its quality directly affects the quality of agricultural products.Corn is one of the main food crops，raw and the important industry material in our country, ofwhich the yield and quality have direct impact on national health and sustainabledevelopment of society.Therefore it is necessary to study the fractions of chromium afteraging in loess soil and study if the chromium contamination would have a negative impact onthe growth of maize,so that to provide theoretical basis for regional farmland evaluation andsafety production of agricultural products.In this study, field experiments combined with indoor chemical analysis were performedto investigate the chromium fractions after Cr(Ⅲ)(0,187.5,250,375mg/kg) spiking andincubation100days. We planted maize for two years to study its growth in the contaminatedsoil. The results were as follows:1、The soil pH was not significantly affected after spiking and incubation of differentchromium(Ⅲ)concentrations. We can not detect the available chromium after Cr(Ⅲ) spikingand incubation100days. The main fraction of chromium in loess soil was bound to Fe Mnoxides,which accounted for about60%of the total chromium and followed by the residualchromium.The lowest content at about1%was the exchangable chromium which wasbioavailable.The potential biological availability of chromium (carbonate bounded、bound toFe Mn oxides with organic bounded) decreased gradually,which conversed to no bioavailable(the residual)chromium.2、The above ground biomass and thousand grain weight of maize were not affected byexogenous chromium(Ⅲ) contamination but the maize grain number had a decreasingtendency. The maize yield was not significantly affected by exogenous chromiumcontamination but had an increasing tendency.The chromium content in maize grain were not increased with the aggravation of soil chromium contamination. Chromium enrichmentindex of maize grain decreased with the aggravation of soil chromium contamination. When375mg/kg chromium was spiked to the soil, the chromium concentration（below0.1mg/kg）of Zhen Dan958maize grain was far below the pollutants limited value1mg/kg listed in thenational food safety standard（GB2762-2012）.