Accumulation And Migration Of Heavy Metals In The Soil-plant System In The Water-level-fluctuating Zone Of The Poyang Lake Wetland

The river-lake intersecting region is the main place where heavy metals are enriched,and the dry-wet alternation caused by periodic water level change is the key factor affecting the geochemical cycle.Under such special environmental conditions,the characteristics of heavy metals migration and transformation at the multi-media interface and the influencing factors are not very clear.At present,there are few studies on the enrichment,migration and transformation of heavy metals in soil-plant system in the typical water-fluctuation zone of Poyang Lake wetland.In this study,samples of rhizosphere soil and seven dominant plants were collected in different waterlogged zones of typical water-fluctuation zone of Poyang Lake,including perennial non-waterlogged zone(Arcanea arunculata zone),seasonal waterlogged zone(Phragmites australis zone,South Aramica zone,Carcix podzonifera zone and mudflat zone),and perennial waterlogged zone(sediment).Through the analysis of different time and space of heavy metals in soil/sediment and dominant plant(Cr,Ni,Cu and zinc,As,Cd,Sb,Pb,Fe and Mn)content differences and enrichment characteristics of typical down with the heavy metal pollution of the environment evaluation of poyang lake ecological risk,further analyzing the characteristic of the migration of heavy metals in soil-plant system transformation.To reveal the main influencing factors of heavy metal migration and transformation in soil-plant system in the typical water-fluctuation zone of Poyang Lake.The results of this study can provide scientific basis and theoretical support for the biodiversity of soil/sediment-plant system and the prevention and control of heavy metal pollution in the typical wetland of Poyang Lake.(1)The contents of heavy metals in the soils and sediments of the typical Poyang Lake wetland in the perennial unflooded zone,seasonal flooded zone and perennial flooded zone were Fe > Mn > Zn > Cr> Pb > Cu > Ni > As > Sb > Cd.The heavy metal content in the soil/sediment of the reed-australia zone was the highest in the seasonal flooded zone.The results of enrichment factor evaluation showed that Cu,Pb and Sb were significantly enriched in wetland soil/sediment(EF>5).(2)In the typical water-fluctuation zone of Poyang Lake,the soil/sediment heavy metal pollution degree is as follows: Cu > Pb > Sb > Zn > Mn > Cr > Fe > Ni >As > Cd.The soil of four vegetation communities in the perennial non-flooded zone,seasonal flooded zone and perennial flooded zone is moderately polluted by Pb.The ten heavy metals in the soil/sediment of the perennial unflooded zone,the seasonal flooded zone,the perennial flooded zone and the vegetation zone were at the level of slight ecological hazards,but the potential ecological risk value of the seasonal flooded zone was significantly higher than that of the perennial unflooded zone and the perennial flooded zone.In addition,there were significant differences in the heavy metal contents in soil/sediment between seasonally flooded zone and non-flooded zone and perennial flooded zone(p<0.05),which indicated that seasonal flooded zone was the main site of heavy metal enrichment.(3)Cu content of the dominant plant in the perennial non-flooded zone was significantly higher than that in other vegetation zones,and the enrichment level of Zn was higher.The content of most heavy metals in roots was higher than that in the aboveground parts(stems and leaves).In general,the high content of heavy metals in wetland plants in April may be related to the growing season.The enrichment of heavy metals in different tissues of the seven dominant plants in the three waterlogging zones showed an overall pattern of uniform distribution(Artemisia argyi),enrichment in roots(Phragmites australis,Lepidoptera argyi,Carex officinalis),and uniform distribution(Artemisia sinensis,Radix japonicus,Polygonum chinensis)with the increase of water surface distance.(4)There was no correlation between the heavy metal contents of 7 dominant plants in the four vegetation belts and t silt and sand.Most of the heavy metal contents in different plant tissues were negatively correlated with the p H value in the soil.The difference of the heavy metal contents in the underground part of plants was less than that in the aboveground part of plants.BAF values of the seven dominant plants for Cd and Sb were all greater than 1,and the TF values for Cr,Ni,Cu,Zn and As were generally between 1 and 2.RDA comprehensive sequence showed that the migration of heavy metals by these seven dominant plants in Poyang Lake was mainly affected by p H,organic matter,water content and Mn.