Mercury Enrichment In Aquatic Food Chain And Its Relationship With Water Eutrophication In Guizhou Plateau Reservoirs

As a global pollutant,mercury has high toxicity,which transmission in the food chain has been one of the hot topics in the field of environmental science.Yunnan-Guizhou Plateau is rich in karst landforms.Compared with other reservoirs,Hongfeng Reservoir,Baihua reservoir and Aha reservoir located around Guiyang city have many environmental factors,such as temperature,nitrogen,phosphorus content,eutrophication and trophic structure of aquatic food chain,which are very unique.Studies have shown that the degree of reservoir nutrition not only affects the methylation rate of mercury in water environment,but also affects the accumulation of mercury in aquatic food chain.To explore the methylmercury in plateau reservoir in the aquatic food chain and the relationship between the eutrophication,in July 2020(wet period),September 2020(normal period),October 2020(dry period),the aquatic food chain species,mercury and methylmercury contents,as well as water mercury and methylmercury contents and eutrophication degree of Hongfeng reservoir,Baihua reservoir and Aha reservoir were studied,the results show that:1.Guizhou plateau reservoir of mercury in the aquatic food chain has obvious spatial and temporal variation characteristics and the distribution of phytoplankton and methylmercury in time change is characterized by high level period and water content,the plentiful trend is relatively low,the distribution of zooplankton and methyl mercury time performance for the plentiful content is higher,level period and low water content,the benthic animal and fish are characterized by level period and water content is higher,the plentiful content lower distribution characteristics.Regional urbanization degree is higher,this may be due to research reservoir surrounding has a large number of factories and mines,human disturbance factors,further influence the distribution of mercury and methyl mercury in the aquatic food chain,and climate conditions,biological habits and the change of environmental factors are also important factors affecting the distribution of mercury and methylmercury.2.According to the eutrophication status evaluation of Guizhou plateau reservoirs in different hydrological periods,the comprehensive nutrient index of Hongfeng Reservoir is in normal period > high water period > low water period,Baihua reservoir is in normal water period >high water period > low water period,and Aha reservoir is in in high water period > low water period > normal water period.On the whole,Hongfeng and Baihua reservoirs belong to medium eutrophic reservoirs,Aha reservoirs belongs to eutrophication reservoirs.3.According to the accumulation amplification of mercury and methylmercury in aquatic food chain of different reservoirs,the accumulation amplification is different among different reservoirs.The concentrations of mercury and methylmercury in phytoplankton in Baihua reservoir were the highest,and those in Aha reservoir were the lowest.The bioaccumulation factor of mercury content in zooplankton in Baihua reservoir is the highest,followed by Aha Reservoir.The bioaccumulation factor of mercury content in zooplankton in Hongfeng reservoir is the lowest,and the bioaccumulation factor of methyl mercury content in zooplankton in Baihua reservoir is the highest,which is consistent with the distribution of bioaccumulation factor of mercury content in zooplankton.The maximum bioaccumulation factors of mercury and methylmercury in benthos of Baihua reservoir are the highest among the three reservoirs,while the minimum bioaccumulation factors of mercury and methylmercury in benthos of Hongfeng reservoir.The bioaccumulation factor of mercury in fish is obviously different from that of methyl mercury.The bioaccumulation factor of mercury in Baihua reservoir is the highest,that of methyl mercury in Hongfeng reservoir is the highest,and that of mercury and methyl mercury in Aha reservoir is the lowest.4.The nutrient formation of the reservoir may cause certain primary producers such as phytoplankton advantages or abundance to change,and thus,through the transmission effect of the food chain,the nutritional level of the high nutrient level,the nutritional level of the same species between the different plateau reservoirs may be caused by different levels of nutrient localization.Clustering analysis shows that both mercury and methylmercury in the water body of the three reservoirs are in the same class,indicating that the mercury and methylmercury pollution sources may have a certain correlation,and the amount of mercury in the plankton and phytoplankton in a class,which shows that the mercury content changes are certain,and the reason for the diversity analysis may be the environmental factor of different reservoirs.The correlation analysis showed that the amount of mercury in phytoplankton is significantly correlated(n= 162,p< 0.05),and the water eutrophication caused by human activity had a certain effect on the concentration of mercury in phytoplankton.The amount of mercury in fish and benthic organisms was significantly relevant to the chlorophyll(n= 162,p< 0.05),and the change in the variation of fish and benthic mercury content may be caused by phytoplankton.The RDA analysis showed that the changes in total phosphorus,total nitrogen and chlorophyll and phytoplankton mercury were closely related to the Pearson correlation analysis.There was no correlation between TLI and the contents of mercury and methylmercury in all species in the aquatic food chain of Hongfeng reservoir,Baihua reservoir and Aha reservoir,which indicated that the factors affecting the contents of mercury and methylmercury in the aquatic food chain were complex and needed further study.5.The simulation experiments showed that the enrichment of Hg and Mehg by Pseudanabaena Limnetica increased with time,and the enrichment rate was the fastest on the first day,and then decreased.With the addition of different concentrations of Hg and Mehg,the metal content in phytoplankton increased with the increase of the added metal concentration,but the enrichment rate decreased with the increase of the added metal concentration.Different nutrient levels had a certain effect on the enrichment of phytoplankton,which indicated that the enrichment of phytoplankton on metals might be affected by nutrient salts.Correlation analysis showed that there was a negative correlation between the enrichment of Hg and eutrophication.There was no significant correlation between the enrichment of MEHG and eutrophication.