The Relationships Between Soil Heavy Metal Contents And Soil Microbial Quantity And Enzyme Activities

Soil is an unrecyclable resource and soil pollution with heavy metals is becoming moreand more serious, as solid waste and sewage, agricultural fertilizers bring about continuousheavy metals into it during rapid development of industry, agriculture, traffic, and so on.Because of the heavy metal pollution in soil is not easy to be decomposed, it constitutepotential hazards to the plants and animals as well as human health via food chain andresearches on prevention and control of soil heavy metal pollution has been more and moreactive. Microbes are accounted for the proportion of soil per unit volume is very small, butcan be employed in heavy metal polluted soil restoration via their oxidation, reduction, andmethylation role to change the configuration of metals, and to convert toxic substance intonon-toxic or low toxic ones, thus changing the soil structure and improving soil quality. It isof great theoretical significance to understand relationships between heavy metals and soilbiological community structure and functions, and is practically important to explorepossible strains capable of restoring polluted soil.The study was conducted at two sewage irrigation ditches with paddy soil in Gansuprovince. The contents of ten commonly reported heavy metal elements in soil, and colonynumbers of soil bacteria, fungi and actinomycetes, as well as soil pH, activities of urease,catalase and sucrosease were determined. The findings, after statistical and correlationanalysis of the data, are as following.1. Heavy metal contents and the correlation among them in the East and West ditchesdiffered from each other. In East Ditch, which contained high average heavy metals, thecontent of Zn significantly positively correlated with those of Cd and Cu, and Cu positivelycorrelated with As and Pb, while Pb positively correlated with As. positive correlation, zincand the As, is significantly related to the content of Pb and Pb and Mn content is verysignificant negative correlation. In West Ditch, As content very significant positivecorrelated with Cd, Cu contents, Zn and Cd contents very significantly positively correlated,Zn and the As, Cu content is significantly related to the Mn and Cr, V and Ni content issignificant negative correlation. 2,10kinds of common heavy metal soil in the studied area main microbial quantityresearch shows that the influence of bacteria, actinomyces and fungi under differentpollution degree of heavy metal content of the sensitivity and tolerance are differences, theincrease of the content of Pb, Cr, the number of bacteria, actinomyces and fungi haveinhibition; Cd, Hg, As, the increase of the content of V on the number of bacteria and fungihas obvious inhibition effect on actinomycetes relatively is not obvious; Zinc, Cu, Ni, Mncontent in the synergy and inhibitory effect on soil microorganisms are not obvious, but inthe68-160mg/kg range near the increase in Cu content has inhibitory effect on bacteria,actinomyces and fungi has a certain synergy. Gully and the west through the neusoftcorrelation analysis found that: under the background of slightly alkaline soil, heavy metalsand soil microorganisms, such as bacteria, actinomyces, fungi number correlation is notobvious.3, heavy metal content in the different soil samples and the soil enzyme activityresearch found urine enzyme activity and the content of heavy metal cadmium wassignificantly positive correlation; Enzymatic activity of oxidase and V content relatedcoefficient reached0.541, and mercury content is0.439, has a certain relevance. With theincrease of pollution degree, the soil urease and catalase activity decrease trends. And theincrease of Cd content of hydrogen peroxide enzyme activity has a promoting effect, hasinhibitory effect on sucrase.Hg and Mn content on the influence of hydrogen peroxideenzyme activity is not obvious, has obvious inhibitory effect on soil urease, when Hgcontent is greater than0.3influence on soil invertase activity is not obvious. When the Ascontent is more than40m/kg, activity of catalase and urease activity of performance forsynergies.Cr, Cu, zinc and Ni content increase the activity of catalase, urease activity ofsynergies; And the soil invertase is opposite. V, there is no significant impact on three kindsof soil enzyme activity.