| Abandoned open-pit tailings ponds can continuously release metal(loid)s into surrounding environment.Studied in the mining area,Pb and Zn isotopes were used to trace the source of heavy metal contamination and to quantify the contribution of each source to the contaminated soil-plant system in a typical gold/iron mining area.Meanwhile,the transport and transformation processes of heavy metals in the soil-plant system were traced using Zn isotopes and factors that control the isotopic fractionation were discussed.The survival strategies of dominant plants under long-term heavy metal stress in oligotrophic abandoned iron tailings ponds were investigated from a biogeochemical perspective.By combining high-throughput sequencing,metagenomics and metabolomics technologies,we attempted to elucidate the characteristics and evolutionary mechanisms of soil-plant microbial community and to investigate the interaction in the soil-microbial-plant system,which provides a scientific basis for the environmental remediation of barren heavy metal contaminated tailings ponds.The main results are as follows:(1)The heavy metal pollution of soil and plants is characterized with a spatial distribution,for instance,the overall shows light pollution,but it displays moderate to heavy pollution in the mining activity-intensive areas.The heavy metals in the soil-Salsola system are mainly distributed in the rhizosphere soil and the leaves and conclude that migration ability to heavy metals is greater than the accumulation ability in Salsola collina Pall.The bioconcentration factor(BCF)and transfer factor(TF)of Salsola collina Pall for heavy metals were:Cr>Zn>Pb>Cu>Fe>Cd and Fe>Cd>Zn>Cu>Pb>Cr.(2)The variation ranges of 206Pb/207Pb and 208Pb/206Pb in the mining area are:1.10-1.18 and 2.10-2.19 in soil,1.04-1.09 and 2.24-2.32 in tailing,1.11-1.16 and 2.11-2.20 in plants,respectively.The lead isotopes of soil-plants in moderately and heavily polluted area are close to those in ore/tailings(206Pb/207Pb<1.2).Combined with Bayesian model,it is concluded that tailings are the main pollution source of lead in soil and plant roots,in details,soil lead contributes 43%-75%of overall pollution source,plant lead contributes 32%-50%of overall pollution source and the plant leaves are mainly affected by atmospheric deposition result from mining activities and coal combustion.(3)The plants enrich in light isotopes of zinc(?66/64Zn?-0.25%o)in aboveground parts,but the underground parts are enriched in heavy isotopes of zinc(?66/64Zn?0.17%o).The different degrees of isotope fractionation occurred in process of zinc in the soil rhizosphere(?66/64Znroot-soil?0.26),root absorption process(?66/64Znleaf-soil?-0.16),and root-ground transport process(?66/64Znleaf-root?0.16).(4)Heavy metals(Cu,Fe,Zn,Pb)significantly affect the community structure and diversity of microorganisms.The keystone taxa of the tailings soil-plant system is mainly phosphorus solubilizing bacteria such as Pantoea,organic matter-degrading bacteria such as Methylobacterium,nitrogen-fixing bacteria such as Rhizobium,and heavy metal-tolerant bacteria such as Sphingomonas.(5)Salsola collina Pall reciprocal symbiont grows and colonizes in a barren iron tailing environment because of a series of special survival strategies,such as obtaining nutrients(C,P,N),producing plant growth hormones(flavonoids,etc.),inhibiting the growth of plant pathogens through secondary metabolites,and resisting high levels of heavy metals. |
PDF Full Text Request