Effects Of Several Typical Algae On Adsorption-desorption And Photoreduction Of Mercury In The Karst Reservoir In Guizhou

Guizhou karst region is located in the mercury-mineralized belt of the Pacific Rim,so rich in mercury ore content,due to long-term poor mining,the pollution of mercury in Guizhou karst waters is more serious.Algae,as an important producer of aquatic ecosystem,is at the bottom of the food chain.It can enrich mercury and concentrate it step by step through the food chain,which magnifies the toxicity of mercury and causes great harm to the health of high nutritious organisms such as people in the region.Therefore,it is of great significance to study the adsorption-desorption law and photoreduction characteristics of mercury by typical algae in karst reservoir of Guizhou Province.Elliptic dinoflagellates,hydrocystis,and copper-green microcystis are commonly found in the Karst reservoir in Guizhou Province.The growth period of ellipsocytes is about 16 day,and the growth cycle of hydrocystis is about 21day.The growth cycle of copper-green microcystis is about 14day;Infrared analysis found that the three types of algae mainly contain unsaturated functional groups such as hydroxyl groups（-OH）,carboxyl groups（-COOH）,amino groups（-NH₂）,phenolic hydroxyl groups（Ph-OH）,ether bonds（-O-）,and hydrocystis.,In addition to possessing these groups,there is also an unsaturated carbon dioxide peak（C=O）;According to the specific surface area calculation formula,the specific surface area of the three types of algae is in order,and the copper-green microcystis>Elliptic Chlorella>Aquilaria,It was found that Chlorella ellipticum,Shui Hua and Microcystis aeruginosa were commonly found in Guizhou karst reservoir,and their mercury adsorption was affected by pH,algal abundance and adsorption time.Under other conditions,the adsorption capacity of mercury was the strongest in algae with pH=4⁸,and the adsorption capacity increased gradually with the increase of algal abundance,and decreased with the increase of algal abundance,and the adsorption capacity of algae increased with the increase of algal abundance.The adsorption of mercury by algae showed that the adsorption of mercury was faster than that of slow,in which the adsorption equilibrium of living algae was reached after 720 min,and that of dead algae reached adsorption equilibrium after 240 min.When the adsorption equilibrium was reached,the maximum adsorption rate of Chlorella ellipticus was 71.18%,the maximum of dead algae was 62.92%,the number of dead algae was 52.56%,the number of dead algae was 49.93%,the percentage of microcystis aeruginosa was72.59%and the percentage of dead algae was 64.86%.It was found that the adsorption kinetics of mercury for the three kinds of algae was in accordance with the quasi-second-order kinetic equation,and the adsorption process of dead alga cells was more suitable for Langmuir isotherm adsorption model,while that of living alga cells was more suitable for Freundlich isothermal adsorption model.In the desorption process,the active algae increased first and then slowed down,while the dead algae continued to increase,and the desorption law of the three species of algae showed some differences with time,such as Chlorella ellipticus.The concentration of mercury desorbed by living algae before 60 min of Shui Hua was higher than that of dead algae for 60 min,but that of microcystis aeruginosa was always higher than that of dead algae.The desorption rate of living algae was 69.46and that of dead algae was 80.39%;the desorption rate of Shui Hua was 45.290 and the desorption rate of dead algae was 52.304%;that of microcystis aeruginosa was34.71%and that of dead algae was 37.77%.The desorption rate of Chlorella ellipticum was 69.46%and the desorption rate of dead algae was 80.39%;the desorption rate of Shui Hua was 45.290%;the desorption rate of dead algae was52.304%;that of Microcystis aeruginosa was 34.71%;It can be seen that the living algae of the same species are less than the resolving rate of the dead algae.Among different algae,the desorption rate of Chlorella ellipticus was higher than that of Shui Hua filamentous algae>Microcystis aeruginosa.Light has an important effect on the reduction of Hg2,and the effect of different wavelengths of light on the reduction process of Hg2 is quite different.Under the irradiation of UVA and UVB,the reduction ability of the three types of algae was Shui Hua>Chlorella ellipticus>Microcystis aeruginosa,and under visible and dark conditions,Chlorella ellipticus>Shui Hua>Microcystis aeruginosa.The reduction ability of dead algae was stronger than that of living algae under all kinds of light conditions,which was mainly due to the difference of adsorption ability between living algae and dead algae.The kinetic study showed that under the condition of UVA and UVB,the reduction ability of dead algae was higher than that of living algae.The photoreduction reaction of three kinds of algae to Hg2 showed a second order kinetic reaction.This study identified pH,algal abundance,adsorption time is a key factor affecting three kinds of algae adsorption effect on mercury,quantitative analysis and variation of the three types of algae adsorption desorption test;mercury adsorption reaction process in the conjecture of the algal cell surface and light reduction process,and determine three kinds of algae in different light according to the conditions of mercury light The original law and light reduction.The research results provide important data on the basis of understanding the influence on the migration and transformation of mercury in Guizhou Karst water algae.