| Heavy metal pollution of agricultural soils in China is becoming increasingly serious,and the farmland area is large and the land type is complex,which poses a serious threat to the natural ecological environment,food security and human health.Phytoremediation technology has become an important means of heavy metal remediation in farmland soil because of its green,pollution-free and low-cost characteristics.Sphagnum is an important poverty-alleviation industry in alpine and high-altitude areas of Guizhou Province.Its yield per mu is3-4 times that of rice in Guizhou Province,and it generally grows in relatively humid alpine areas.At present,the research on Sphagnum is mainly focused on the monitoring of air quality and carbon sequestration capacity,there is still a lack of research on the absorption and enrichment ability of heavy metals and the pseudorrhizosphere microorganisms of Sphagnum.The key to improving Sphagnum to repair heavy metal polluted farmland in different regions of our country is to explore the controlling effects of key Sphagnum bacteria and microorganisms on soil physicochemical properties and heavy metal accumulation.For this reason,the Sphagnum is the main test material,and rice and cultivated grass are the contrasting material.Seven research areas are selected in Dading village,Duyun City,Guizhou Province of our country.Four of the research areas are the Sphagnum cultivated under different heavy metal pollution,and the other three areas are the rice,cultivated grass,bare crops and soil under the same growth background.By using 16 S r RNA microbial amplification sequencing,inductively coupled plasma mass spectrometer and high-throughput omics analysis,the distribution characteristics of soil microbial communities in the pseudorrhizosphere of Sphagnum were revealed,the degree of heavy metal pollution in the study area was defined,and the soil quality was evaluated.The shaping and regulating effects of pseudorrhizosphere bacteria and microbial groups of Sphagnum on soil environment in different growing environments were analyzed.Meanwhile,the interaction between bacteria and environmental factors in different land use types of Sphagnum soil,artificial grassland soil,rice soil and bare soil under the same growing environment was analyzed.The adsorption capacity of Sphagnum,artificial grass and rice to heavy metals was compared,aiming to provide theoretical and scientific basis for comprehensive management of farmland environmental quality,and to find suitable bacteria and microorganisms to repair contaminated farmland soil,which has important practical significance for future soil development management and ecological restoration of Sphagnum.The main results obtained are as follows:1.Soil quality pollution was evaluated by means of soil accumulation index method,pollution index method,enrichment coefficient method,correlation analysis,etc.,and it was found that the study area was mainly polluted by heavy metals Hg and Cd.According to the results of previous research and laboratory analysis,it was found that the pollution sources of the two heavy metals were inconsistent.The pollution of Cd is considered to be caused by man-made pesticide spraying and sewage irrigation,and the heavy metal Cd in AN of the study area may mainly come from road traffic pollution.Sphagnum has higher enrichment capacity for heavy metals Pb,Cd,As,Ni and Zn,while rice has higher enrichment capacity for heavy metals Hg and Cu,and cultivated grasses have better enrichment capacity for Cr.As a whole,Sphagnum has higher enrichment capacity for heavy metals than rice and cultivated grasses.The average RI of the study area is 103.75.According to the data analysis results,the pollution is not serious and belongs to slight ecological risk.2.The data of bacterial microbial diversity of all samples in the study area were analyzed by amplified 16 S r RNA gene sequencing.The results showed that 857773,356239931 bases.Domain: 1,Kingdom: 1,Phylum: 51,Class: 165,Order: Domain: 1,Kingdom: 1,Phylum: 51,Class: 165,Order: 390,Family: 625,Genus: 1160,Species: 2479,OTU:8192.The TOP5 species in phylum level include Proteobacteria,Acidobacteriota,Actinobacteriota,Chloroflexi and Firmicutes Among them,Acidobacteriota has the highest abundance in Sphagnum soil.Because it is acidophilus,Sphagnum soil is more acidic,so it is more abundant in Sphagnum soil.Proteobacteria is more abundant in Sphagnum soil bacteria than that in artificial grassland and bare soil,and Actinobacteriota is more abundant than that in rice soil bacteria community.In summary,the most abundant bacteria and microorganisms in the pseudorrhizosphere soil of Sphagnum were the most abundant groups in the whole study area,and the soil bacteria and microorganisms of Sphagnum were more able to adapt to the changing environmental factors.3.By using correlation analysis and RDA analysis,we found the regulation effect of the core rhizosphere microbial community of Sphagnum on farmland soil under different pollution conditions,the interaction and influence between different heavy metal contaminated farmland soil and physical and chemical properties,bacteria and microorganisms.The heavy metals Hg and As in Sphagnum soil are related to the dominant bacteria.The physicochemical properties of soil p H,TP,AN,AP,AK,SOM and TN all have an effect on Acidobacteriota,Chloroflexi and Bacteroidota.However,TK and p H were significant environmental factors.Chloroflexi had strong tolerance to heavy metals Hg and As,and Methyloirabilota had good tolerance to heavy metals Ni,Cd,Cr,Zn,Pb and Cu.The bacterial community abundance and diversity were different in the four Sphagnum growing areas.Different growing environments affected the microbial community changes in the pseudorrhizosphere of Sphagnum.Soil heavy metal content and soil physicochemical properties had significant effects on the bacterial community abundance and bacterial diversity in soil.The bacterial community abundance and diversity were different in the four Sphagnum growing areas.Different growing environments affected the microbial community changes in the pseudorrhizosphere of Sphagnum.4.The three crops under the same growth background show great differences in their ability to enrich heavy metals.Sphagnum has the same effect on soil indexes as other crops even without the use of any pesticides or pollutants.Sphagnum as a new type of crop,has a significant impact on the overall quality of soil after 30 years of planting.Sphagnum obviously increases the acidity of soil,but also significantly increases the content of AP and TP.The overall analysis results showed that soil microorganisms responded more positively to the variability of p H,SOM and AK contents,although the variability was not high.With the increase of p H value,the abundance of the dominant species Proteobacteria also increased.When soil physicochemical properties are covariant with heavy metal pollution,microbes,soil physicochemical properties and heavy metals interact with each other.Verrucomicrobiota and Gemmatimonadaceae had a good tolerance to Hg,while Firmicutes and Myxococcota had a good tolerance to Cd.The heavy metals and soil physical and chemical properties of different land use types under the same growth conditions also have significant regulatory effects on bacteria and microorganisms.Bacteria and microorganisms have different adaptation mechanisms to different heavy metal pollution and soil physical and chemical properties. |
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