| Sanjiang plain in northeast China is the most important terrestrial wetland distribution area in China,which once had large area and multiple types of wetlands.But the wetlands in Sanjiang plain have been reclaimed and degenerated to agricultural production,intensive and extensive agricultural regions have been to the primary landscape.The existent wetlands are surrounded by agricultural landscape.Therefore,the wetlands are under the seriously interference.Wetland are keep receiving surface runoff which is determined by its geomorphology and hydrology characteristics,but more and more contaminations are getting into the wetland through the runoff particularly in Sanjiang plain.Phthalic acid esters(PAEs),which is known as a kind of semi-volatile organic compounds(SVOC).PAEs are extensively used in industrial and agricultural production and daily life,which is one of the global distributed pollutions,some individual PAEs have been proof as endocrine disrupting effects,therefore the distribution and transformation of PAEs in the environment are receiving extensive attentions.In this study,PAEs concentrations of surface water,surface sediments and the inflow river of wetland were measured.The occurrence and distribution in natural wetland were investigated,the effects of surrounded agricultural regions to the distribution and composition of PAEs in wetland were discussed.In terms of the distribution pattern and beased on the fugacity approach to simulate the transportation and transformation a multimedia model was developed,which can be used for simulating the transportation and transformation of PAEs in natural wetland system.The occurrence of 10 individual PAEs in the wetland sediments was investigated,including DMP and DEHP,the concentration of individual PAEs rang from no detected to 294.9 ?g·kg-1,DEHP and DnBP were the most abundant PAEs.Total PAEs concentrations in 3 typical wetland surface sediment were as follow:Qixinghe wetland(419.87 ± 75.53 ?g·kg-1)>Naolihe wetland(295.32 ? 67.54 ?g·kg-1)>Honghe wetland(229.73 ± 66.47 ?g·kg-1).The total concentration of PAEs in sediment of Qixinghe wetland ranged from 128.41 to 502.79?g·kg-1,with the mean value of 284.61 ?g·kg-1.PAEs significantly differed among wetland types;the average PAEs concentration of surface sediments were as follows:Phragmites australis wetland>Carex lasiocarpa wetland>Deyeucia angustifolia wetland.In addition,the distribution 6 priority control PAEs in soil of constructed wetland was investigated,the mean value of ?6PAEs was 532.11 ± 198.12 ?g·kg-1,and DMP,DEP,DnBP and DEHP were detected in all constructed wetland soils,the concentration was in descending order:DEHP>DnBP>DnOP>DEP>DMP>BBP.DEHP and DnBP were also the most abundant PAEs in constructed wetland soils.The results indicated that the wetland ecosystem was under threat of heavy PAEs contaminations,even the pollution level of PAEs in wetland sediments was low compared with the sediment or soil in other studies.PAEs concentration level in the Qixing river were measured,which is the main water inflow source of natural wetlang.The total concentration of PAEs in water of Qixinghe river were ranged from 1310.2 to 3528.6 ng·L-1 with the mean value of 2365.5 ± 574.9 ng·L-1.The concentration of individual PAEs ranged from not detected to 897.6 ng·L-1,and DMP,DEP,DiBP,DnBP,BBP,DEHP and DnOP were detected in all Qixinghe river samples.Concentration of PAEs in Qixinghe river were seasonal varied,spring has the highest concentration,followed by autumn and summer.The distribution and composition of PAEs in wetland surface water were investigated,concentration of individual PAEs ranged from not detected to 1090.5 ng·L-1,DMP?DEP?DiBP?DnBP and DEHP were detected in all surface water of Qixinghe wetland,DEHP exhibited the highest concentration is 424.7 ng·L-1.The seasonal variance of PAEs in wetland surface water was quite different with the Qixinghe river,summer shown a highest PAEs concentration,followed is spring and autumn.Comparing with other studies all over the word,the pollution level of PAEs in sanjiang plain was still low.Health risk assessment were conducted on 5 individual PAEs,the HI values of Qixinghe river were higher than surface water in wetland,it indicated that no non-carcinogenic risk of PAEs in both water in Qixinghe wetland and water in Qixinghe river.On account of the distribution pattern of PAEs in wetland sediment and wetland water,a multimedia model was developed to simulate the chemical fate of PAEs in wetland system which based on the fugacity approach and the mass balance approach.Water,sediment,submerged and emergent vegetation were compartmentalized as the main environment phases in this multimedia model.The physicochemical characteristics of PAEs and wetland ecosystem characteristics were used for parameters calculation,which could use for calculating the mass concentration and mass flux in and between different environment phases.The measured PAEs distribution results,related parameters were used as the input parameters for calculation.This mass balance model was verified by using the data concentration which obtained in summer of the model study aera,the model validation result showed the simulation result of this model are in acceptable agreement with monitoring data in natural wetland system.Monte Carlo analysis and Sensitivity analysis were conducted to analysis the feasibility of multimedia model,contaminant concentration of inflow water is highly sentisive to PAEs concentration in system whose sensitivity coefficients are 57.09%and 47.01%for DEHP and DnBP,respectively.The multimedia model was applied to simulate the chemical fate of DEHP in different environment phases.This multimedia model could offer the opportunity to access the concentration in different phases and evaluate the environmental transformation and transportation processes.The flux of DEHP between different phases were calculated,including water,sediment,submerged and emergent vegetation which is necessary to analyze the transportation and transformation processes of DEHP in wetland ecosystem. |
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