| Heavy metals are one of the main causes of soil pollution.There are three main effects on soil,at first,the diversity of microbial in the soil is relatively little,secondly,the fertility of soil is decline,the last but not the least,soil hardening is serious.These problems can cause serious damage to grain production and safety,how to deal with soil heavy metal pollution becomes an urgent problem confronted with modern agriculture.According to the problems,the study of microbial technology was applied to improve heavy metal contaminated soil.The thesis focused on the high-efficiency phosphate-solubilizing bacteria(PSB)was to screen from rhizosphere soil.Cheap carbon source and nitrogen source was determined to make the microbial colony live stably in soil,it will improve the microbial structure of soil.Phosphorus solubilizing ability of PSB was determined in NBRIP fluid medium,it can improve soil fertility and promote plant growth.The heavy metals are passivated and cut down damage to the soil.These provide theoretical foundation and reference basis for large-scale improvement of soil heavy metal pollution.In this paper,six strains of PSB were isolate,screen and identify from crop rhizosphere of Henan Province.By the analysis of 16S rDNA sequencing,the strains were identified as Bacillus megaterium,Brevibacterium sp.,Bacillus cereus,Acinetobacter sp.,Paenibacillus cineris,and Paenibacillus sp..The results showed that inorganic P-solubilizing abilities ranging between 103.45 and 154.79 mg·L-1.The resulted showed that in 50 days the P-solubilizing abilities by PSB was 76.02 mg/L,109.36 mg/L and 44.22 mg/L when using the glucose,plant starch and bagasse as the carbon source respectively.And in 50 days the P-solubilizing abilities by PSB was 34.11 mg/L,211.98 mg/L and 299.44 mg/L when using the Soybean meal,urea and ammonium sulfate as the carbon source respectively.The changes of microbial flora structure were analyzed by molecular biological method in 50 days.Based on P-solubilizing abilities in with different carbon source and nitrogen source,plant starch as carbon source and ammonium sulfate as nitrogen source was determined to improvement the structure of microbial flora in soil.The pot experiments were used to proof that the soil fertility was improved and stimulate plants growth by PSB.In pot experiments,the total height,height of aerial parts,dry weight,wet weight and total P of the plants had significant difference between CK and the treatments with the addition of PSB after the growth of 60 days.The result showed that growth rate of aerial parts of plant was improved of 30.53%and the dry weight of plant was improved of 43.28%compared with the control group.The PSB effectively promoted the absorption of phosphorus by plants compared with CK.The result showed that the content of P in root was improved 34.06%and the content of P in aerial parts was improved of 8.04%.Removal of heavy metals by PSB in liquid environment of simulated heavy metal pollution was studied.The resulted that the removal rates of Cu,Pb,Zn and Cd were increased by 30.62%,48.90%,6.41%and 19.72%under action of PSB compared with the aseptic conditions.The passivation products were redissolved under action of PSB or organic acids,the resulted was showed that the product of lead can hardly be redissolved,and the product of copper,zinc and cadmium have a small amount of resolution,but the amount of dissolution is little compared to the passivation products.It is found that the reason of the redissolution is action of organic acids. |
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