| Chromium is widespread and its’adsorption and speciation in soil determine its biological effectiveness. Organic matter, especially the most active dissolved organic matter, can increase the content of soil organic matter and nutrients, not only can improve soil structure and fertility, but also have an impact on the migration of heavy metals in soil conversions. Therefore, the study of water-soluble organic matter on chromium morphological changes can guide us about rational use of water-soluble organic matter in the soil of chromium pollution control and repair.Through the use of adsorption kinetics and thermodynamics and adsorption isotherm equation fitting assay results analysis, preliminary study of the adsorption properties of exogenous Cr(Ⅵ) in powder clay, studied the solid-liquid ratio, temperature, different concentrations of chromium and various factors affecting adsorption oscillation time to it, and forecast Cr(Ⅵ) migration trends in pink clay. The results show that changes in environmental conditions have a great influence on the adsorption capacity of change, exogenous Cr(VI) assay results in powder clay pseudo-second order kinetic equation, changes in soil environment solid-liquid ratio and temperature irrelevant; silty clay adsorption Cr(Ⅵ) is weaker physical adsorption and non-spontaneous exothermic process.On this basis, a preliminary study on organic matter silty clay adsorption Cr(Ⅵ) adsorption equilibrium and the reasons for changes in water-soluble form of chromium; orthogonal design was further investigated with incubation time change and different concentrations of exogenous Cr water-soluble organic matter on a comprehensive process of clay powder chromium in influence, and do the analysis of its possible impact reasons. That the organic matter of the soil adsorption test of exogenous Cr(Ⅵ) has a certain extent, and most of the organic fraction is converted to carbonate and Fe-Mn oxide bound. Exogenous adding water-soluble organic matter will make the soil tested for Cr(Ⅵ) adsorption capacity increases and exchangeable content and proportion will be reduced, but the presence of water-soluble organic matter will make the proportional decrease of residue so that the residual potential AVAILABLE form transformation, a significant increase in the proportion of the content and especially the Fe-Mn oxide.After orthogonal test of exogenous Cr(Ⅵ) into the soil tested, and the proportion of its residual content significantly reduced, a significant increase in contrast ratio and exchangeable content, and other forms content and increased the proportion of less, there is a residue state to the other forms of mutual transformation, making available contents increased. And with the prolonged incubation time, and in different incubation time, the maximum time for each form of chromium appear different, exchangeable content decreases, the content of Fe-Mn oxide, carbonate and organic matter bound with unstable, residual content of an increasing trend, but it is still less than the original soil residual content.At different concentrations of exogenous Cr(Ⅵ), the added different concentrations of water-soluble organic matter, along with the extended incubation time of the test soil chemical properties change, leading to various forms of chromium powder, clay content and ratio of change different trends mainly reflect changes in pH, the carbonate and CEC content. Using SPSS analysis shows, pH, CEC and exchangeable and carbonate content was negatively correlated. Chromium is embodied in various morphological changes:changes in the content of volatile exchangeable and residual fraction, by the combined effect of many factors. With time, reduce the proportion of exchangeable for test soil soluble organic matter content and exchangeable positive correlation, the water-soluble organic chromium has a fixed effect, so that it can reduce the use of content, migration diminished capacity; carbonate and Fe-Mn oxide bound state with increasing content of water-soluble organic matter concentration increases combined with the extension of time to cultivate a certain volatility oxide bound to increase some more, for water-soluble soils organic matter content and Fe-Mn oxide is positively correlated with the increase of incubation time and increase rather regular; and the combination of the change in state of instability, which by exogenous Cr(Ⅵ)oncentration variation greater impact; residue the proportion of the state in the early culture period (first and second week) reduced post-culture (fourth week and eighth week) increase in the proportion of the presence of potentially available to states transformation, there are some environmental risks. |
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