Study On Phytoremediation Of Heavy Metal Contaminated Soil By Bamboo Stand

Considering of the characteristics of fast growth and large biomass of bamboo,the method of direct planting in the field was conducted to explore the mechanism of heavy metal stress resistance of bamboo plants using different species and cultivation systems,and to investigate the phytoremediation technology of bamboo plants for heavy metal-contaminated soil.The study area Fuyang is located in Zhejiang Province.Heavy metal-contaminated water from a galvanization factory was used for irrigation at the paddy field.Thus,the soil at the site was contaminated with multiple heavy metals(Cu,Zn,and Cd).The treatment plots?Monoculture of moso bamboo,monoculture of Phyllostachys praecox,and corresponding bamboo intercropped with Sedum plumbizincicola?were established at the study site in a random manner.The distribution of heavy metals in contaminated soil-plants system,the bioconcentration ability and translocation characteristics of heavy metals in different planting systems,the effects of plants on microbes in contaminated soil,characteristics of plants rhizosphere soil and their secretions were studied,which provide scientific basis for phytoremediation by bamboo plants in heavy metal contaminated soil.The main results are as follows.1.Heavy metal distribution in plant and soil system is greatly affected by the planting patterns.In the soil,the contents of available and total Cu,Zn,and Cd of intercropping of bamboo(moso bamboo and P.praecox)and S.plumbizincicola was relatively low.Available Cu,Zn,and Cd contents were 65.0%,28.7%,and 48.4% lower in the IMS,and 52.8%,24.8%,and 45.5% lower in the monoculture of moso bamboo than those in the control(uncultivated;CK),respectively.In the plant,the Cu and Zn contents in mature bamboo tissues were significantly lower,but the Cd contents in bamboo tissues(except for leaves)higher,in the intercropping of P.praecox and S.plumbizincicola than in the monoculture of P.praecox.In moso bamboo,Cu contents in bamboo rhizomes,branches,and leaves and those of Zn and Cd in all bamboo tissues were significantly higher in the intercropping of moso bamboo and S.plumbizincicola than in the monoculture of moso bamboo.The bioconcentration and translocation factors of bamboo tissues showed an obviously increasing tendency from monoculture to intercropping.The tested intercropping system of two plant species showed higher biomass productivity,implying more heavy metals can be removed from the soil through the harvesting of plants.2.Correlation analysis among soil physicochemical properties and heavy metal content showed that soil available heavy metal content was positively correlated with soil organic carbon,total nitrogen,available nitrogen,available phosphorus and available potassium,but negatively correlated with soil pH.Bamboo phytoremediation of heavy metal contaminated soil can increase soil porosity and soil water holding capacity in the field.The values of soil water content,maximum moisture content,capillary moisture content,minimum moisture content,capillary porosity,non-capillary porosity,and total porosity were higher in 0-20 cm soil layer than those in 20-40 cm soil layer of pure bamboo stand.The bamboo upper soil bulk density is less than that of the underlying soil of P.praecox.Compared with uncultivated control soil,the soil bulk density values of pure moso bamboo and intercropping systems were both low,and the water holding capacity and porosity indexes were all at a relatively high level.According to FT-IR spectroscopy analysis,the locations of multiple soil absorption peaks in P.praecox,moso bamboo and S.plumbizincicola were similar,indicating that different types of phytoremediation soils contain many identical functional groups.And the phytoremediation of bamboo stands increases the vibration of characteristic functional groups in the soil,especially in the 0-20 cm soil.3.Relative abundence of the microorganism at phylum level,Proteobacteria was the most dominant bacteria,accounting for more than 30% in each sample.There was a significant difference(P < 0.05)in the relative abundance of Acidobacteria,Nitrospira,Bacteroidetes and Chloroflexi among the two planting patterns(monoculture of moso bamboo,intercropping of moso bamboo and S.plumbizincicola)and the control soil.From the analysis of the correlation among microorganisms and soil heavy metals,it showed that the total and the available values of heavy metals were significantly negatively correlated with Nitrospira and Acidobacteria(except for available Zn)(P <0.01),and significantly positively correlated with Bacteroidetes(P < 0.01).Although there were no significant differences in ?-diversity analysis(reflect the diversity in the sample),it can be found that there were significant differences of microorganisms among three types of soils(ANOSIM,P < 0.05)according to the ?-diversity analysis(reflect the diversity Between the samples).The different planting patterns have a significant effect on the composition of the soil microbe.And soil microbial community structure and the community diversity have undergone significant changes.The monoculture and intercropping of moso bamboo planting patterns are both beneficial to the increase of soil bacterial diversity,and the monoculture of moso bamboo is relatively more abundant.Soil microbiota plays an important role in the ecological restoration of heavy metal contaminated soil,and it also indicates the tolerance and sensitivity of heavy metals.4.In the intercropping system,the contents of total nitrogen,organic matter,available nitrogen,available phosphorus,and available potassium were highest in the rhizospheric soil of S.plumbizincicola.And the available content and total contents of heavy metals were higher than those in the rhizosphere soil of moso bamboo.The contents of heavy metals in the rhizosphere soil were generally lower than those in non-rhizosphere soils,especially in the P.praecox soil.The rhizosphere soil components of the phytoremediation were similar,and belong to hydrocarbons,alcohols,ketones,acids,esters,phenols,benzenes,ethers,amides,aldehydes,and alkenes.The main chemical components of the detected rhizosphere soil extracts were(E)-caryophyllene,octadecanoic acid,n-Hexadecanoic acid,Methyl isobutyl ketone and so on.In moso bamboo phytoremediation,the relative content of(E)-caryophyllene in the rhizosphere of monoculture and intercropping systems of moso bamboo were highest,which were 12.65% and 13.32%,respectively.In the P.praecox phytoremediation,the relative content of octadecanoic acid in the rhizosphere soil of bamboo in monoculture and S.plumbizincicola in monoculture were the highest,which were 12.97% and 13.81%,respectively.And the relative content of(E)-caryophyllene in the rhizosphere soil of P.praecox and S.plumbizincicola in intercropping system were both highest,followed by n-Hexadecanoic acid.