Enrichment Characteristics And Poison Research To Crops Of Heavy Metals In Fe-Mn Nodules Soil In Karst Area Of Guangxi Central

Addressd to soil,a key element in the field ecosystem,to find out the relationship of elements contents in Fe-Mn nodules,soil and crops,and solved the problems like characters of Fe-Mn nodules,nutrient status of soil,contents of heavy metal and analysis of speciation,quality of crops.The surface of Fe-Mn nodules were mostly yellow brown and smooth,the shape were sphere,spherical or globular ellipsoid.the diameter were 1.0-30.0mm,contents of oxides showed that high iron and low manganese were the main feature,compared with soil, the Fe-Mn nodules had enrichment effect on Fe2O3,MnO and heavy metals,enrichment of heavy metals was closely related to Fe2O3.In Fe-Mn nodules,residual fraction was the highest proportion in elements of Cd,Cr,Cu,Pb,Zn,Mn,indicated that these elements were relatively stable in normal conditions;potentially available of Mn was the highest proportion,second to Cr and Pb,so should strengthened its detection. The single Cu2+,Cr6+ was easily adsorpted by Fe-Mn nodules,Cr6+ was easily desorpted by deionized water and simulated acid rain,while Cu2+ was relatively stable.Compound Cu2+-Cr6+ were adsorpted completely,because of Cu2+,the adsorption of Cr6+ was promoted significant.The adsorption-desorption to Cu,Cr had relation with iron oxide content,alumina content,CEC contend\organic content,pH etc.Fetility level of soil were very rich in devonian paddy field,while medium in carboniferous and cretaceous,effective phosphorus was lack or very lack and became the major limiting factor for growth;Contents of heavy metal were closely related to pedogenic parent material,the difference of pedogenic parent material resulted distinctive of heavy metal contents.Heavy metal of soil in Fe-Mn nudules distribution were evaluated,the resultes showed that the soil had to a certain extent pollution,the soil of carboniferous was serious pollution,second to soil of Devonian,while soil of cretaceous was very good; the highest proportion was found in Cd, Cr, Cu, Pb and Zn of residual form,Cd in bioavilable form possessed the highest proportion, while others had very low. Cd was the main pollution in this area. Mn in potential available form had the highest proportion, second to Pb, so attention should be given to its impact.In Fe-Mn nodules distribution,the contents of heavy metals,single factor index,composite index,quality level were difference in types of crops and different organs of the same crop,the order of composite index in difference organs was roots leaves stem fruit seeds;while the order in types of crops was vegetables fruit potato food;Corn had a certain degree tolenrance and resistance to heavy metals,so can be used planted as the prefer option.Ca(OH)2 and organic fertilizer were effective conditioner to inhibit the activity of heavy metals,so can be widely used.This paper had been explain the characteristics of Fe-Mn nodules and impact to soil and crops,it can be technical reference to quality of crops in the Fe-Mn nodules distribution.