Distribution Of Heavy Metals In The Oncmelania Hupensis And It As A Biomonitor Of Heavy Metals

Poyang Lake gaining the laureate of the largest freshwater lake of China is one of the mostimportant ecological regions recognized by the Global Natural Fund. Nowadays, with the rapidincrease of population and the quick development of industry and agriculture, the environment andecosystem for the Poyang Lake wetland have been suffered potential menace from heavy metalpollution.In this study, Oncomlania hupensis from Poyang lake wetland were used as the researchobject, and the concentration of heavy metals (As, Hg, Pb, Cd, Ni, Cu, Zn and Cr) in the soil andOncomelania hupensis samples were analyzed to investigate the spatial and seasonal variationduring dry and flood season. The main environmental factors influencing the enrichment of heavymetal in Oncomelania hupensis were discussed. Meanwhile, the feasibility for the OncomelaniaHupensis as a biomonitor of soil heavy metal pollution in the Poyang Lake wetland was evaluated.The main contents of the study as follows:Chapter1, the progress of the heavy metal and heavy metal bio-indicators were summarized.The superiorities of Oncomelania hupensis as heavy metal contamination bioindicator wereintroduced in detail. Meanwhile, the necessity of monitoring the heavy metal contamination inPoyang Lake wetland was also proposed.Chapter2, the concentration of heavy metal in Oncomelania hupensis were analyzed byinductively coupled plasma atomic emission spectrometry (ICP-AES) and sequential injectionhydride generation atomic fluorescence spectrometry (SI-HG-AFS). Results indicated that Cu andZn show the highest concentrations in Oncomelania hupensis samples whereas Hg shows thelowest concentration. And the soft tissue had higher affinities for heavy metals than the shell. Theconcentrations of heavy metals in different size classes of the Oncomelania hupensis were alsoevaluated. In general, the order of heavy metal concentration in different size classes were largerOncomelaia hupensis contains higher level of heavy metals than the smaller one. Theconcentration of Cu, Zn, Cr, Hg, As and Cd in Oncomelania hupensis showed significant spatialvariation. The concentration of heavy metal in the Oncomelania hupensis showed a slight but notsignificant difference during the two seasons, except for Cu, Cd and Cr, which were significantlyhigher during the dry season.Chapter3, the feasibility for the Oncomlania hupensis as a bio-monitor of soil heavy metalpollution in Poyang Lake wetland was evaluated under the condition of cultivating environment.Oncomelania hupensis and soil samples were collected once every two weeks, and the content ofheavy metals in the shell, soft tissues and soil samples were determined. The results showed thatthe soil in blank group was clean and suitable for laboratory cultivated purposes. The ratio of different heavy metals between soft tissue and shell in the same cultivating environment werecompared, Cu, Zn and Cd showed higher values than the other elements. In different cultivatingenvironments, a significant positive correlation was found in Hg, Ni and Zn concentrationbetween the shell and soil, same correlation was also found in Ni, Cu and Zn concentrationbetween the soft tissue and soil. According to the correlation analysis and the BCF values, thesequence of heavy metals bioaccumulation in the shell was Cd>As>Ni>Zn>Hg≈Cu≈Pb>Cr andin the soft tissue was Cu>Cd>Zn>As>Ni>Hg>Cr>Pb, respectively. The study revealed that theshell can indicated Hg, Ni, Zn pollution, while the soft tissue can monitor Ni, Cu, Zn and Cdcontamination. Therefore, Oncomelania hupensis can effectively be used as heavy metalbio-indicator of Poyang lake wetland.