Enrichment Features Of Mercury And Methylmercury In Phytoplankton

Phytoplankton as an important producer of aquatic ecosystems at the bottom of the food chain, mercury and methylmercury as a kind of highly toxic heavy metal,the hamfullness of which would be magnified by the enrichment of phytoplankton and food chain. In order to understand the accumulation characteristics of phytoplankton to mercury and methylmercury, we collected the surface water and phytoplankton sample of the Baihua Reservior and Hongfeng Reservior in different seasons, and we also selected Xiaoguan Reservior a small eutrophia reservior to sample water and phytoplankton with a weekly frequency in July to September 2014,and analysis the THg and Me Hg variation characteristics of phytonplankton and the influencing fact. An indoor simulation experiment was been done to increase the understanding of mercury and Me Hg adsorption and uptake by phytoplankton,and the influnce of water environment to algae.The results showed that the Hongfeng Reservoir seasonal phytoplankton Me Hg content ranged for 5.57-15.19 ng/g, the THg ranged for 5.25-15.14 ng/g.Baihua Reservoir seasonal phytoplankton Me Hg ranged for 5.25-15.14 ng/g, the THg ranged for 69.45-147.63 ng/g. A big fluctuation was observed with season change in Hongfeng Reservoir,and in autumn and spring, the highest THg content of phytoplankton appeared at Yaodong, and in summer the highest THg content appeared at the Daba,winter was the Houwu.The mean values of THg and Me Hg content in all seasons from high to low were summer, autumn, winter and spring, but the variation of seasonal Me Hg content of phytoplankton was relatively low, which showed strong stability. THg content of phytoplankton in Baihua Reservoir was significantly higher than that in Hongfeng Reservoir, the Me Hg content of phytoplankton in this two reservior showed little difference, Baihua reservoir seasonal THg content of phytoplankton from high to low in order for the spring, autumn, summer and winter, Me Hg performance for the summer, autumn, winter and spring.The difference of phytoplankton community had great influence on the THg and Me Hg of phytoplankton, Dinoflagellates and Chlorophyta were the main algae which affected the Me Hg and THg of phytoplankton in Hongfeng Reservior, Canonical correspondence analysis showed that the correlation between Melosira granulata var.angustissima, Scenedesmus bijuba and the Me Hg,THg of the algae was sighnificant.The Diatoms, Chlorophyta and Dinoflagellates had a sighnificant influence on the Me Hg accumulated by algae in Baihua Reservior, COD was the most effective factor on Me Hg enrichment of phytoplankton.The variation range of different mercury species in the water of Xiaoguan Reservior was 1.02-6.78ng/L(THg),0.63-4.99ng/L(DHg),0.027-0.853ng/L(TMe Hg) and 0.027-0.532ng/L(DMe Hg).THg and Me Hg in phytoplankton were 146.559-241.779ng/g and 4.856-15.521ng/g, respectively.The BCF of phytoplankton to THg and Me Hg were 5.46 * 104-2.15 * 105 and 3.48 * 104-4.15 * 105.The peak of THg and Me Hg BCF appeared at 4th-7th weeks,and the Me Hg and THg content of phytoplankton in up reaches were higher than the Dam.The content of THg and Me Hg in water decreased from the upper reaches to the dam.We found that the phytoplankton abundance would inhibit the THg enrichment of itself,and the DOM,WTHg and WTHg could promote the mercury accumulation by algae.Indoor simulation experiment showed that acidic conditions was beneficial to the adsorption of Me Hg by Aphanizomenon flosaquae in the medium from Hongfeng Reservior,but Microcystis aeruginosa and Anabaena cylindrical showed the opposite character.When the medium replaced with Xiaoguan water,all algae showed acidic conditions for better adsorption.We also found low concentration DOM promoted the uptake of Hg2+ and Me Hg.MA showed a more stable ability for the adsorption of Me Hg in different acid-base condition,the adsorption of Me Hg changes greatly. By AF and AC with the change of acid and alkali condition. MA and AC had more affinity than Hg2+,the main enrichment mode of Hg2+ by the three algae was assimilation, and the Me Hg was adrsorption.