Analysis Of DOM Sources Of Typical Wetland In Poyang Lake And Their Effects On Morphological Changes Of Heavy Metals

Dissolved organic matter(DOM)can affect the interaction of heavy metals in soil,affect the migration and transformation of heavy metals,and have a certain impact on the toxicity and bioavailability of heavy metals.Wetland is a land-and-water zone with alternating wet and dry water.The material,information and energy transfer are very active.The change of water level will release DOM into the water,which will affect the environmental chemical behavior of pollutants in this area.In order to further explore the source of wetland DOM and its interaction with heavy metals,this paper selects the typical large-scale freshwater lake wetland in China,the typical falling zone of Poyang Lake,as the research area,based on the visible visible organic matter(CDOM)UV-visible spectrum,using three-dimensional fluorescence spectrum.Technology combined with Fluorescence regional integration(FRI),mainly to explore the influencing factors of DOM extraction conditions,DOM source,and use single factor index method,Nemero index evaluation method,ground accumulation index,heavy metal potential ecological risk coefficient evaluation method The effects of heavy metal pollution assessment and DOM on the morphological changes of heavy metals in the sediment of Poyang Lake wetland were carried out.The results of this study are as follows:(1)Optimal oscillation extraction conditions for extracting dissolved organic matter(DOM)in soil: Soil CDOM has a good linear positive correlation with dissolved organic carbon(DOC),and the absorption coefficient ag(355)can be used to express CDOM concentration.The extraction time was 16 h,and the extraction effect was the best when water was the extract.Direct analysis by orthogonal test showed that the soil-water mass ratio was 1:10,centrifuged at 4 000 rpm for 30 min,and the 0.45 ?m glass fiber filter was used to obtain the best DOM extraction effect.The size of each influencing factor: the effect of soil-water ratio> filter type> oscillation time> centrifugation time.(2)The composition of dissolved organic matter(DOM)in water,soil and plants in the typical water-falling zone of Poyang Lake,the degree of humification,and the source of pollution: There are four types of three-dimensional fluorescence peaks in the water body of Poyang Lake.The DOM of lake water is mainly land source.Input is dominant and is less affected by human activities.There are six types of threedimensional fluorescence peaks in the soil,ACBTDE,and the intensity of A and C peaks is stronger than that in water bodies.The protein-like peaks are weaker than water bodies;the DOM is highly humified in soil and has a large molecular weight;There are more types of fluorescent peaks and plant proteins,and the content of DOM in plants is higher than that of water and soil.The rA/E and rC/E of Longkou Nanxun and Longkou Reed are less than 1,and the content of fulvic acid is less than that of tryptophan.In the remaining plant samples,rA/E and rC/E were greater than 1,and the content of fulvic acid in DOM was greater than that of tryptophan.(3)The effect of exogenous DOM on the morphological changes of heavy metals in sediments: The planting of bryophytes has a certain passivation effect on heavy metals Cr,Pb and Zn,and has a certain activation effect on Cd and Cu.The addition of DOM has an activation effect on Cd,Cu and Zn,and the activation is enhanced with the increase of DOM content;it has a passivation effect on Cr and Pb,and the passivation is strengthened with the increase of DOM content.After the addition of exogenous DOM,plants and DOM act together to inactivate Cr,Pb and Zn.Plants and DOM work together to activate Cd and Cu.