Effect Of Straw On The Transformation And Migration Of Heavy Metals Cu In Polluted Soil

With the rapid development of China's agriculture,city and traffic,the phenomenon of soil heavy metal pollution is increasingly serious.Adding straw to reduce soil pollution and increasing soil fertility become gradually general.In order to take reasonable measures to return straw,then achieve a good result.In this paper,we discuss the dynamic morphological transformation process of heavy metals in farmland soil under the condition of alternating wet and dry water management,adsorption and desorption characteristics of Cu in the farmland soil and leaching characteristics and release kinetics of heavy metals in contaminated soil.Experimental study of morphological changes of Cu on soil caused by straw addition in soil incubation.It was found that under water alternating wet and dry training mode,the increase of concentration of heavy metal Cu increased the content of exchangeable and carbonate fractions of heavy metals in soils,and the proportion of heavy metals in the residual fraction was decreased.The pH value of soil water system was decreased by the increase of straw and concentration,carbonates,Fe and Mn oxide ratio decreased with the increase of straw application,organic state and residual state were increased correspondingly;The relative content of exchangeable was decreased at high Cu concentration with straw addition,low concentration is increased.Adsorption desorption characteristics of heavy metals in soil solution of Cu were studied by adsorption desorption method.The experimental results show that,under the experimental conditions,The adsorption of heavy metals Cu by soils were increased with the increase of the time and the concentration of heavy metals,reduced with the increase of the temperature and straws,tend to be stable eventually;Elovich kinetic model fitted the highest coefficient,and the isothermal adsorption to Langmuir adsorption equation was the best.Leaching of heavy metal Cu in copper contaminated soil was studied through the experiment of leaching experiment of soil column.The study showed that the concentration of heavy metals in leaching solution was high before 160 mL leaching accumulation in the simulated precipitation,the release rate decreased gradually,which belongs to the quick release period;after 160 mL,the release amount becomes gradually smooth and stable.The increase of heavy metal content and the addition of straw will lead to the increase of release capacity of heavy metal Cu in soil,and the high concentration of exogenous Cu could reduce the relative release rate of heavy metals.