Studies On Characteristic Selection Of Heavy Metal Pollutants For Cultured Molluscs And Their Risk Assessment

Based on current documents, this dissertation does approximately ensure the selecting range of theenvironmental pollution caused by mollusks cultured. In this range, combined with the characteristics ofmolluscs on research, we found out a selecting method for the characteristic pollutants, which uses bacteriatoxicity detector to test the relative toxicity coefficient of characteristic heavy metal pollutants, and sets theRT/BCF as the index of comparison for the ultimately absolute toxicity in order to select the characteristicpollutants. Based on the detective results, we can detect and analyse the characteristic pollutants in the twokinds of molluscs in Xiangshan Bay, by which we can undergo risk assessment and the results are asfollows:1. Distinguishing the heavy metal pollutantsAccording to the frequency of the advent of heavy metal and the proportion which exceeds thenational standard, we can ensure the range of the heavy metal pollutants in mollusc cultured environment.The7heavy metals as follows are the heavy metal pollutants: Pb, Cu, Cd, Zn, Hg, As, Cr.2. Selecting the characteristic heavy metal pollutantsWe try to select the distinguished heavy metal pollutants above by using the MicroTox Model500blinking bacteria toxicity detector to experiment on Photobacterium phosphoreum (Vibrio fischeri)cultured in Cu, Pb, Cd, Hg, As, Cr, Zn. Through the regression analysis of the density of the knownpollutants and the corresponding luminous intensity, we can get the relative toxicity coefficient.Furthermore, combined with the BCF, the value of RT/BCF is regarded as a index of comparison forabsolute toxicity. The smaller it is, the more harmful it is, thus the pollutants with low values of RT/BCFratio ought to have the priority to be detected as characteristic pollutants.3.Selecting the characteristic heavy metal pollutants for farming environment of Sinonovaculaconstricta and Tegillarca granosa in Xiangshan BayUsing the selecting method above to select the characteristic heavy metal pollutants in Xiangshan Bay,we can find the orders of prior detection of the three characteristic pollutants (Cu, Cd, Pb) in Sinonovaculaconstricta and Tegillarca granosa are as follows: Sinonovacula constricta: Cu>Cd>Pb, Tegillarca granosa:Cd>Cu>Pb.4. Assessments on their contents and health risks of Cu, Cd, Pb in Sinonovacula constricta andTegillarca granosa in Xiangshan BayThe contents of Cu, Cd and Pb in the two important cultured molluscs (Sinonovacula constrictaand Tegillarca granosa) from5sites in Xiangshan Bay, Ningbo over the4seasons in2010were analyzed.Using the assessment method from USEPA and PMTDI recommended by JECFA, we conclude that wheneating the Sinonovacula constricta and Tegillarca granosa cultured in Xiangshan Bay, Cu and Pb have nohealthy risk, while the Cd in Tegillarca granosa is risky. In addition, assessment on ecological risk ofSinonovacula constricta and Tegillarca granosa in different region of Xiangshan Bay illustrates: Exceptthe Pb in Tegillarca granosa culture d in Dajiahe, the others are at the level of no risk or low risk. The Cd in Tegillarca granosa are more probably to be highly risky, while Cu and Pb are risk-free.