Changes Of Arsenic Species Valence And Arsenic Form Under Different Seasonal Conditions In Yangzonghai And Their Effects On Algae Photosynthesis

With the development of industrialization and the strenthening of human activities intervention,arsenic is not only polluting lakes,rivers,soils and groundwater but also threatening human's health and economic system as well as property loss.Algae is sensitive to arsentic as a primary producer of the food chain,the monitoring of algae can well reflect the arsenic situation:changes of arsenic contamination before and after deciding a situation that whether the algae with strong ability to tolerate arsenic in water will become algae with advantage.In addition,changes of arsenic are also significantly affected by environmental factors:for example,when Eh is oxidized at a higher value,trivalent arsenic can be oxidized to pentavalent arsenic,and adsorbed by iron oxide,to a certain extent,the toxicity to aquatic organisms will be reduced.For the reasons of serious arsenic damage,environmental factors affect arsenic morphology,valence and algae are affected much by arsenic.So,this paper will study valence state,morphology and effect on photosynthesis of microalgae of Yang Zonghai from the perspective of arsenic,and discuss water surfaces,sediment interface water,and the chang rule of arsenic in sediment under the influence of environmental factors,as well as the dominant algae formed under arsenic stress and the effect of arsenic on algae photosynthesis.It also provides some theoretical basis for arsenic control and monitoring in water body in the future.The main results of this paper are as follows:1.Exploring the distribution and the source of pollution of high arsenic region in the surface water body.The results show that the high arsenic area is mainly distribute in the south and the northern part of the Yang Zonghai,and the pollution mainly comes from Tangeying,Tangchi Town,sanshi mu of phosphate fertilizer plant,thermal power plant,hot spring and fly ash accumulation field.2.Discussing water surfaces,and the changs of arsenic in sediment under the influence of environmental factors,the results show that:?1?the surface water is mainly as As???,and the sediment interface water is mainly as As???,and in surface water,Eh is positively oxidized,Oxidation of As???to As???.?2?As???was reduced to As???in the lower reduction state of Eh in sediment interface water.The average annual pH value>8?7.5-8.9?was weak alkaline,which was beneficial to the transformation of As???to As???.At T<25?,As???is reduced to As???with the increase of temperature.Under the condition of high oxidation of Eh,As???was oxidized to As???,Meanwhile,As???was adsorbed and precipitated by iron oxide.Conversely,in the reduced state of Eh<0mv,As???was reduced to As???,which was resolved from the iron-manganese oxide binding state.When pH is weak alkaline,As???is oxidized to As???.When oxygen is sufficient,iron passivates to form iron oxides with active sites to precipitate As???.?3?The arsenic speciation of sediment with environmental factors?T?Eh?pH?is weakly correlated.3.It was found that the changes of different arsenic concentrations and different seasonal environmental factors have different influences on different algae,which caused different bioavailability,chlorophyll a concentration and photosynthesis of natural mixed algae.The results showed that under the condition of temperature of?14-25??and low concentration of arsenic promoted the growth of most algae in cyanobacteria,green algae and brown algae,the increase of chlorophylla and ETR_max;high concentration of arsenic and Eh inhibited the growth of most algae in cyanobacteria,green algae and brown algae,also the increase of chlorophylla and ETR_max;The growth and photosynthesis of Chlorophyta and brown algae were inhibited.