Effects Of Different Amendments On Cadmium Bioavailability And Microbial Community In Soil

This study used in situ medium and slight Cd contaminated soil and wheat as the research material,pot experiments were conducted in situ soil by adding amendments(biochar,nano hydroxyapatite,calcium hydroxide and actinomycetes)to evaluate the effect of different amendments on Cd bioavailability in contaminated soil-wheat systems,and high-throughput sequencing technology was used to elucidate the bacterial community structure of wheat rhizosphere soil and assess the effect of adding different amendments on soil physical and chemical properties and soil microbial community structure,it provides a scientific basis for in-situ remediation of Cd polluted soil and reducing the risk of Cd to the production of agricultural products.The main conclusions are as follows:Effects of different amendments on growth characteristics of wheat.The addition of amendments could reduce the content of hydrogen peroxide and malondialdehyde in wheat and increase the activity of antioxidant enzymes to enhance wheat's stress resistance.And single application of alcium hydroxide and the combined application of alcium hydroxide and actinomycetes could promote the growth of wheat,increase the chlorophyll content of wheat,and maybe increase the photosynthesis of wheat.Effects of different amendments on Cd transfer in wheat-soil system.The addition of amendments could reduce the exchangeable form and carbonate form content of soil Cd,increase the Fe-Mn oxide form,organic form and residual form content of soil Cd,therefore the addition of amendments could reduce the bioavailability of Cd.Single application of actinomycete A74,the combined application of A74 with alcium hydroxide and nano hydroxyapatite,and the combined application of A12 and biochar could inhibit the transfer of Cd to aboveground parts,and the combined application of A74 with alcium hydroxide and nano hydroxyapatite,and the combined application of A12 and biochar could also reduce the enrichment of Cd on the aboveground parts of wheat.Effects of different amendments on soil physicochemical properties,soil enzyme activities and microbial communities.The application of alcium hydroxide mainly caused the increase of pH,available Fe,calcium ion concentration and cation exchange capacity;the application of biochar increases the content of organic matter,available potassium,total nitrogen,ammonium nitrogen and exchangeable Mg;and the application of nano-hydroxyapatite increased the content of total phosphorus,available phosphorus,and nitrate nitrogen.In addition,the application of alcium hydroxide also caused a significant increase in soil alkaline phosphatase activity,however,the application of actinomycetes,biochar,and nano-hydroxyapatite significantly reduced soil alkaline phosphatase activity,however,the effect of amendments on urease,dehydrogenase and sucrase is basically contrary to the above phenomenon,which was mainly related to pH and the content of exchangeable.The application of the amendments had a certain effect on the microbial community composition,in which the addition of alcium hydroxide promoted the abundance of the Proteobacteria and Actinobacteria,while the addition of biochar,nano hydroxyapatite and actinomycetes was not conducive to the increase of the abundances of the Proteobacteria and Actinobacteria,and the addition of alcium hydroxide is the biggest factor of microbial community variation.Factors of influencing Cd transport and microbial communities in soil-plant systems.The Spearman correlation analysis between Cd and soil physicochemical properties in soil-plant systems showed that the Cd content in wheat roots was positively correlated with the content of ammonium nitrogen and cation exchange capacity negatively correlated with the concentration of calcium and magnesium ions;the above-ground Cd content of wheat was positively correlated with the content of ammonium nitrogen and organic matter,and negatively correlated with available phosphorus content.The Cd transfer coefficient was positively correlated with organic matter content and negatively correlated with available phosphorus content,cation exchange capacity and available iron content.The Spearman correlation analysis between phylum species and soil physicochemical properties showed that Proteobacteria was significantly negatively correlated with soil available K,whereas it was significantly positively correlated with calcium ion concentration.Calcium ion also had some influence on other dominant species,such as Actinobacteria and calcium ion concentration showed a significant positive correlation,Thaumarchaeota and calcium ion concentration showed a significant negative correlation.Acidobacteria had a significant negative correlation with pH,while pH had no significant effect on other dominant species.Chloroflexi is mainly affected by total phosphorus.Redundancy analysis of bacterial community composition in different treatments indicated that pH,soil dehydrogenase,urease and nitrate nitrogen were the main driving factors for the change of bacterial communities in wheat rhizosphere.