| Dianshan Lake is the largest natural freshwater lake of Shanghai and the important water conservation district of Huangpu River upstream.The surrounding area of Dianshan lake is one of the more vigorous place of social development and investment growth in Taihu basin.But along with regional economic development,the number of cars and the demand for fossil fuel increased year by year,the total amount and species of pollutants also increased,causing the deterioration of environment.Persistent organic pollutants(POPs)could experience long distance migration,atmospheric dry/wet deposition and finally accumulate in the terrestrial and aquatic ecosystems,probably causing serious damage to environment and humam health.Considering the hazard as well as the lack of research for environmental behavior of anthropogenic POPs in Dianshan lake area,the typical POPs in multimedia environment of Dianshan Lake were researched in this study.Water,suspended particles,surface sediments and aquatic organisms were collected in four seasons from winter 2015 to autumn 2016,concentration,emission sources and ecological risks of PAHs,PCBs and OCPs were analyzed.In addition,based on the environmental parameters of Dianshan lake area,a QWASI(Quantitative Water Air Sediment Interaction)fugacity model was constructed and applied to simulate the occurrence,fate and transfer features of 16 priority-controlled PAHs set by US EPA in Dianshan lake ecosystem.The aims of this study were to realize the real-time monitoring of pollutants and to provide important reference and scientific basis for regional environmental governance.The results of this research included the followings:1)Seasonal variation of PAHs concentrations were consistent in water soluble phase,particle phase and sediment phase from Dianshan Lake,PAHs concentrations in winter and spring were higher than that in summer and autumn.2-3 rings PAHs was major component with the low proportion of 5 and 6 rings in water,the same feature was also showed in suspended particles,especially in winter,but proportion of 4,5 and 6 rings PAHs increased in particles.The partition coefficient(Kp,5.13×102?1.81×106 L/kg)of PAHs in soluble and suspended particle phase had obviously seasonal change.Partition coefficients in winter and spring were much higher than those in summer and autumn,indicating that PAHs tended to adsorb on the suspended particles at low temperature at winter and spring.In sediment,4 ring PAHs showed the highest proportion and the percentages of 5 and 6 ring PAHs significantly raised,showing no evident seasonal variation.The spatial distribution characteristics of PAHs in water soluble phase show the order:inflow river>lake>outflow water.PAHs concentration in lake suspended particles was higher than that in surrounding rivers with higher than that in lake sediment.There were no significant relationships between PAHs concentrations in suspended particles and sediment with total organic carbon(TOC).Compared with other researches at home and abroad,PAHs pollution in water of Dianshan Lake was in a low level,which was lower than most of lakes in China and much lower than lakes and rivers in major countries of Western Europe and North America.PAHs pollution in sedimentwas lower than most of studied areas,but higher than some nature reserves and sparsely populated areas.PAHs content in submerged plants was higher than that in emergent aquatic plants and floating plants,with the main component(2 and 3 rings).The average content of PAHs in fishes(367.1 ng/g)was in medium pollution level compared with other researches in home and abroad,which should be paid more attention.2)The seasonal variations of PCBs in water and sediment were winter>spring>summer>autumn.The primary composition was Penta-PCB with an average value in water(30.47 ng/g)higher than the upper Yangze river tributary.Average content in sediment(5.50 ng/g)was lower than that in most of researched areas.PCBs content in lake water was higher than rivers near the lake,but sediment was on the contrary.PCBs concentration changes in different aquatic plants was tape grass>bamboo pondweed>water caltrop>reed>water hyacinth.PCBs in submerged plant was higher than those in emergent aquatic plant and floating plant with an average content(40.7 ng/g)and main component(Hexa-PCB and Hepta-PCB).Concentration variation of PCBs in fishes was predatory carp>topmouth culter>crucian>yellow catfish>grass carp>carp with an average content(32.16 ng/g)and main component(Penta-PCB).PCB pollution of fish was in a lower level contrast with other researches.3)Variation of OCPs content in water was spring>autumn>summer>winter,HCHs and DDTs were main component.OCPs concentration in spring and autumn were significantly higher than summer and winter,which was related to agricultural activity.Content in lake water was higher than surrounding rivers but in a low level contrast to other researches.Average content of OCPs in sediment was 25.44 ng/g,higher than surrounding rivers but in a lower level,and seasonal variation was the same as PCBs,showing high level in winter and summer and the lowest content in summer.The average OCPs content in aquatic plants(60.39 ng/g)showed an order:bamboo pondweed>water caltrop>tape grass>reed>water hyacinth.Submerged plant also showed high content,and floating plant content was the lowest.?-HCH content was largest of HCHs in all studied aquatic plants.The average OCPs content(64.88 ng/g)was yellow catfish>grass carp>crucian>carp>predatory carp>topmouth culter,OCPs contents in fishes were generally in a lower level.HCHs and DDTs were main component for water,sediment,aquatic plant and fish.4)Source analysis based on characteristic ratio method showed that PAHs in water dissolved phase,suspended matters and sediment were mainly from coal and biomass combustion,especially obvious in winter and spring and the source of PAHs was more complicated in summer,especially in sediment.PAHs in fishes and aquatic were also mainly from coal and biomass combustion,source of PAHs in aquatic plants was more complex,oil source was also significant.Principal component analysis revealed that besides coal and biomass combustion,oil leakage and volatilization,coke combustion and traffic fuel also had significant contribution to water and sediment.Traffic source(gasoline and diesel combustion)had a great contribution to suspended matters in spring.Contribution of traffic source(gasoline and diesel combustion)and coke combustion,oil leakage and volatilization for sediment were higher than suspended matters and dissolved phase.PAHs in aquatic plants were mainly from coke,coal and biomass combustion,primary source of PAHs in fishes were gasoline and diesel combustion(traffic source).5)Source analysis of PCBs and OCPs in multimedia environment was based on homologue ratio.The results indicated that PCBs in water and sediment of Dianshan lake were mainly from the use of paint or coating containing PCBs,especially for water in summer.Source of PCBs in sediment could also be influenced by the leakage and migration of PCBs in import condenser as well as the saturant in power capactior.PCBs in fishes was maily from the use of dope and oil paint containing PCBs.PCBs in aquatic plant was also from the leakage and migration of PCBs in import condenser besides the same source as fishes.By analyzing the ismoer composition characteristics of HCHs and DDTs,HCHs in water and sediment was mainly from industrial production in winter,the other seasons from agricultural activity.HCHs in fishes and aquatic plants were mainly from agricultural activity.DDTs in water and fishes was primarily due to recent input,sediment was the mixed source of rencent input and historical input,which had evident difference in seasons.DDTs in aquatic plants was mostly from historical residue and long-term weathering.6)The ecological risk assessment results of PAHs indicated that the risk value of PAHs with risk of cancer in water is low.Ecotoxicity of Acy?Flo?Ant?Phe?BaA?BbF and BkF in suspended matters had significant seasonal variability with the maxmium in winter and the minimum in summer.For sediment,the most part of PAHs were in medium risk level(RQ(NCs)?1 and RQ(MPCs)<1),and some PAH(Acy?Chr?BkF?InP?DahA ? BghiP)were in low risk level.PCBs in water existed certain ecological risk,and DDTs,HCHs,heptachlor and heptachlor epoxide were below the national standard.PCBs in sediment was far below ISQG value and the exposure to organisms was in acceptable range,and its ecological risk was at a lower level.All the risk values of DDTs and endrin were above ERL but below ERM,showing potential ecological risk but belonging to low level.The health risk assessment results of POPs for fishes showed that the maximum allowable daily intake of PAHs cancer risk was generally under the daily rate of human consumption,indicating a risk of cancer.The maximum allowable daily intake of PCBs carcinogenic and non-carcinogenic risk were above the daily rate of human consumption,indicating less risk to human health.HCHs and DDTs had certain cancer risk and the health risk of HCHs was higher than DDTs.For fishes,cancer risk of yellow catfish,grass carp and carop were relatively larger,and the maximum allowable daily intake of non-carcinogenic risk was larger than the daily rate of human consumption,non-carcinogenic risk was in a low level.7)Based on the assumed seasonal and annual steady-state conditions,as well as improved environmental parameters,combined with temperature-related solubility and vapor pressure,a QWASI(Quantitative Water Air Sediment Interaction)fugacity model was implemented to simulate the occurrence,fate and transfer features of 16 PAHs in Dianshan lake ecosystem.Generally,there was a good agreement between calculated and measured concentration.The sensitive parameters were decided by sensitivity equation.The model stability was verified after 3000 times' calculation of Monte Carlo simulation.The results indicated that sediment maintained the highest concentration of 16 PAHs and was the fate of PAHs in Dianshan lake ecosystem.There was a significantly adsorption on suspended particle in water and solid in sediment,which revealed high level concentration of PAHs.The bioaccumulation of organism was obvious due to higher concentration of PAHs in aquatic organism than water.The transfer direction of 16 PAHs in three phases was from air to water and then to sediment,but there was a significantly migration process for Nap from water to air.For air,advective input was the principle source for the other 15 PAHs except for Nap,and advective output was the main removal pathway.For sediment,suspended particles deposition was the main source,the approach for removal of PAHs was diffusion and degradation.For water,the major origin were aquatic advective input,atmospheric deposition and diffusion from air to water,the primary removal way was the adsorption and sedimentation of suspended particles.For quarterly changes,the diffusion process and fluxes reached high value in summer,the others showed a relatively high value in spring. |
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