Effects Of The Combined Pollution Of Heavy Metals Microbial Community Structure And Functionbn In Paddy Soil

With the development of economy, heavy metals go into the naturalenvironment where human beings live in through different ways. Heavy metals arecharacterized by hidden and accumulation and the contamination of heavy metals areclosely related to man's living and work. In this case, this problem has been thekey-point in the research of environmenal science for now. In the environment, fewcontamination of heavy metal is solitary, which are combined in most cases. Theresearch of combined contamination of heavy metals has the important theoretial andrealistic meaning to ecological effect of heavy metals in soil contamination,evaluation of soil environmental quality and safety of the quality of agriculturalproducts. The soil microbes are sensitive to heavy metals stress. The decreases ofamount of microbe, the change of community structure of soil are all respondingbehaviors from microbe community to overdose heavy metals duress. The soilcommunity structure has been considered as the effective biological index to soilheavy metals duress. This research collected paddy rice soil contaminated by heavy metals, studiedthe influence of combined heavy metals contamination to biomass, structure, andfunction of soil microbe. This research was focused on principle of soil microbeeffecting by combined heavy metals contamination, which was supposed to supportthe ecological remediation of farm contaminated by heavy metals. The conclusionsare as follows:1. The soil for study was paddy rice soil which was from fuyang county of Zhejiangprovince which was contaminated by combined heavy metals. The study wasconcerned about the influence of heavy metals on soil microbial biomass. Theresults are as follows: Cu, Zn, Cd, Pb combined contamination permanentlydecreased the amount of soil microbe. The available Cu, Zn, Cd, Pb had negativecorrelation (P＜0.05) to the amount of soil microbe characterized by biomass C, Nand total phospholipids. The amount of soil microbe increased significantly whileheavy metals contamination decreased. The soil microbial metabolic quotient alsodecreased with increased heavy metals. Microbial biomass C and N measured bychlorform fumigation extraction or PLFA contents were basically cnsistent.2. This research studied the influence of long-term combined contamination ofheavy metals which were imposed to soil microbial community structure. And theresults indicated that the amount of bacteria, fungi and antinomies and PLFA hadthe trend of decrease. The method of colony flat counting and PLFA were used toreflect the coherence of content of bacteria, fungi and antinomies. In the nature,the long-term combined contamination changed the soil microbial communitystructure, weighting coefficient at about 41.82%. In terms of single PLFA in thehigh level contaminated soil, the content of fatty acid of 12:0, i15:0, i17:0, 18:0,i16:0 and 19:0 was comparatively high, and in the low level soil, the content offatty acid of 20:2w6,9c, 20:0, 16:1w9c, a15:0, a16:0, 18:1w7, 10Mel6:0 and10Me19:0 was comparatively high. With increase of contamination, the relativecontent of microbe fungi increased, but antinomies and gram-negative bacteriadecreased. 3. The research indicated that heavy metal activated the release of CO₂, soil basicrespiration and metabolic quotient increased. The results indicated that under thestress of heavy metals, microbes needed more energy to survive. In this case, thecompetence of metabolism changed a lot, and the efficiency of energy use werecorrespondingly lower. After 1% of astragalus sinicus was added, soil respiration,N of microbial biomass, C of microbial biomass and the capacity ofmineralization of N were correspondingly increased. The release of CO₂ and soilrespiration were enhanced, the capacity of N also increased greatly. The responseof microbial biomass C and microbial biomass N was similar.