Research On The Remediation Technology Of CD Contaminated Agricultural Soil By Composite Regulating Agent

In recent years, due to the problem that the heavy metal content of ourcountry’s food was excessive occurs frequently, causing the country and peopleattach great importance to the problem heavy metals contaminated agricultura soil.Heavy metal pollution in a wide range and long duration, once into the human body,it will cause serious hazard for human health. Therefore, the prevention and controlof heavy metal pollution is one of the key in the field of environmental protection inthe current and future development.This subject evaluated the content scope, cumulative effect and pollution levelof six heavy metals in soil of a certain region by collecting and analyzing the ruralagricultura soil of a certain city. On the basis of clearing the toxicity characteristicleaching procedure impact of the five regulating agents: Calcium-based minerals A,Calcium-based mineral B, Biomass charcoals D, Turf H and Limestone E to Cd insoil by the orthogonal experiment, studied the effects of the three different types ofregulating agents: A, D and E on the content of soil available Cd, selected the bestcomposite regulating agent ADE and its proportion. Meanwhile, studied the Cdcumulative effect in crops’ body, laws for morphological variation of Cd in soil andthe mechanism of composite regulating agent ADE by growing two different localcommon crops: Bok-Choy and Savoy cabbage on two different types of Cdcontaminated soil: SG and JH. The main conclusions as following:(1) The ordering of the pollution level of six heavy metals in soil of a certainregion is Cd> Cu> As> Zn> Pb> Cr. The Cd pollution is severe with the highestcomposite pollution index is3.884; The Cu and As pollution are moderate with thehighest composite pollution index are2.585and2.249; The Zn pollution is mildwith the highest composite pollution index is1.129; The Pb and Cr pollution areclean with the highest composite pollution index are0.664and0.329.(2) The result of Cd toxicity characteristic leaching procedure orthogonalexperiment showed that the ordering of different regulating agents reduce the impacton soil Cd toxicity states is A×D> A> D> B> B×H> E> H> A×H> B×D, whichA×D, A or D are highly significant, B is significant impact, H and E is ineffective.The results show that regulating agents A, B or D all can play an effective role in the repair of JH Cd contaminated soil, especially The repair effect by mixed A and D isbest.(3) With increasing dosage of A, D or E, the content of Cd effective state insoil is trend to decrease, the passivation rate are48.16~65.69%,35.86~52.42%and11.36~46.85%, the best applying concentration of A is10g regulating agent per1kg soil. Meanwhile with increasing time, the content of Cd effective state in soil istrend to decrease; the repair effect was stabilization by using A or D after two weeksand E need one week.(4) In the separately or mixedly applying A, D, E all can reduce the content ofCd effective state in soil when the applying concentration is10g regulating agent per1kg soil, The order of the best treatment to reduce the Cd effective state is A+D+E>A+D> A≈A+E> D> E, the highest passivation rate is86.53%by using compositeregulating agent ADE of the ratio10:5:1.(5) With increasing dosage of composite regulating agent ADE, the content ofCd in crops’ body is trend to decrease in the both of JH and SG soil. The best effectof reducing for content of Cd in Bok-Choy or Savoy cabbage body is applying20g/kg concentration ADE, decreased63.59%and70.71%.The results show thatcomposite regulating agent ADE can effectively repair two different types of soil:JH and SG in the concentration range of5~20g/kg, can make the content of heavymetals Cd in Bok-Choy or Savoy cabbage body decreased, lower than the nationalfood safety requirements limits0.2mg/kg.