The Enrichment And Migration Features Of Mercury In Ecosystem Of Caohai, Guizhou, China

Wetland is a peculiar ecosystem,meanwhile,it is a labile pool and the sink of Hg.The wetland of Caohai was once contaminated obviously by Hg,which posed a potential threat to the safety of ecosystem.This article studies the distribution and content of Hg and methymercury(MeHg)of aquatic plants,plankton,zoobenthos,fish and birds in the wetland of Caohai.The biogeochemical characteristics of Hg,the distribution of Hg in ecosystem and the enrichment and transformation of Hg in the biological chain are analyzed upon the study of biological mercury and food chain of Caohai.The results of Aquatic of plants indicate:(1)The total content of Hg in Caohai is 5.18 ~ 40.06ng/g(average 12.78ng/g)and the Me Hg content is 0.04~2.47ng/n(average 0.34ng/g).(2)The Alternanthera philoxeroides and Water lily have a strong enrichment of Hg and Me Hg.(3)MeHg of plant on the lakeshore is significant higher than it's of inside the lake.(4)The aquatic plant enrichment coefficient of total mercury of sediment is 0.06~0.20(average is 0.12),while the coefficient of MeHg is 0.40~2.78(average is 1.40).Obviously,the latter is significant higher than the former.The results of benthonic animal indicate:(1)Summer and spring have more plentiful benthonic animal,while the content of summer is higher than that of the spring and winter.(2)The total mercury of all the benthonic animal is in the range of 0.51~46.55ng/g and the MeHg is in 0.04~27.71ng/g.Total mercury of samples equence in summer is Cipanggo paludina cahayensis > Bean screw> dragonfly larvae> Exopalaemon modestus heller.However,the sequence in winter is late tadpole> dragonfly larvae> Exopalaemon modestus heller,in spring the sequence is Chironomus larva> Cipanggopaludina cahayensis >leech>Bean screw> Exopalaemon modestus heller.(3)The Cipanggopaludina cahayensis has a significant correlation with the sediment MeHg content(R=0.931,P<1).(4)The Hg and Me Hg contents on the lakeshore are higher than inside the lake.(5)Benthonic animal are not contaminated at present,which concentrates total Hg in the range of 0.11*103~10.32*103 and concentrates MeHg in the range of0.25 *103 ~173.19*103.The results of fishes indicate:(1)The total Hg in fishes are low contents,which in the range of 1.10~68.22ng/g.The MeHg contents in fishes are within the range of0.10~36.53ng/g.(2)The mercury contents fishes are obviously higher than large fishes.(3)Mercury contents in fishes are caused lowly by these reasons,and the enrichment factors of total Hg to water in fishes within the range fo 0.24*103~15.13*103,the factors of Me Hg to water in the range of 0.63*103~ 228.31 *103.The results of zooplankton indicate:(1)Total Hg contents in zooplankton of Caohai are in the range of 27.03~624.50ng/g by dry weight,and total Hg in phytoplankton in are the range of 40.23~325.97ng/g by dry weight.The MeHg contents in zooplankton are in the range of 0.02~173.55ng/g,and MeHg in phytoplankton are in the range of0.02~1.01ng/g.(2)The mercury contents in zooplankton large than 212?m are higher than which are in the length of 100 ~212?m.(3)The mercury contents of zooplankton in spring is higher than that in winter.The enrichment factors of Hg and MeHg of zooplankton are in therange of 0.60*104~13.85*104(average is 4.03*104)and 0.013*104~108.47*104(average is5.59*104)respectively.The factors in phytoplankton are in the range of 0.89 *104 ~ 7.23 * 10 4(average is 2.99*104)and 0.013*104~0.63*104(average is 0.13*104)respectively.The results of feathers indicate:(1)Total mercury contents of feathers are in the range40.41~5057.76ng/g(average is 923.35ng/g),the MeHg contents are 0.75~112.63ng/g(average is15.23ng/g).(2)Feather Me Hg contents of birds in Caohai is significant with the total Hg(R=0.684,P<0.01).(3)The enrichment factors of Hg and MeHg of feathers in Caohai wetland is in the range of 0.9*104~112.13*104 and 0.47 *104 ~ 70.39 *104 respectively.The results of Isotope indicate:(1)The ?13C of wetland aquatic food chain of Caohai is in the range of-30.44‰~-11.66‰.The distribution of ?15N is-1.88‰~20.68‰.(2)The enrichment of Hg and MeHg in the food chian of Caohai aquatic ecosystem according to the order of producers to consumers.(3)The enrichment ability is higher along with the higher nourish grade.The Me Hg contents of highest nourish grade biology is tens of thousands times than the producers.