The Study Of Detection And Accumulation Of The Heavy Metal Cadmium In Marine Intertidal Shellfish

As popular aquatic products, Meretrix meretrix, Tegillarca granosa, Sinonovaculla constricta are nutritious and delicious, and have certain health care function on the body. The artificial breeding and culture technology of these marine intertidal shellfish, which are important aquaculture species, have been improved for a long time in China. These filter-feeding bivalves have weak activity, so that they have high accumulation ability. Therefore, people pay more and more attention to heavy metal accumulation of bivalve mollusc.Cadmium(Cd) is a kind of poison in multi-organs, which has long half-life. It has been listed the 6th poison which has health risk by ATSDR. The invasion into the human body is breath and diet. Trace Cd could accumulate in body, usually the highest content in kidney, followed by liver, heart, muscle and bone tissue. The accumulation of Cd would injury lung, kidney, liver, immune system and reproductive organs.In the study, three newly established detection methods are as follows: determination of Cd, Cr, Pb and Cu in bivalve molluscs by microwave digestion with inductively coupled plasma-mass spectrometry, determination of Cd, Cr, Pb and Cu in bivalve molluscs by high-continuum source atomic absorption spectrometry and Determination of Cd in sediment by wet digestion with inductively coupled plasma-mass spectrometry. The results show that the recovery of standard addition are 94.74%-106%, 90%-107%, 95%-96%, respectively, and the relative standard deviation are all less than 6%. Reliability of these detection results are confirmed by great precision and accuracy. Based on these high sensitive methods, enrichment experiments could be carried out smoothly.Four current national standards and industry standards of China are compared to some foreign standards which are related to shellfish. Meanwhile, actualities of shellfish sanitation at home and abroad were listed to discuss the rationality of limits of Chinese standards. Conclusion it is suggested that appropriate heavy metal limits of shellfish for China should be Hg 0.5mg/kg, inorganic As 1.0mg/kg, Pb 1.5mg/kg, Cd 2.0mg/kg(excluding oysters, scallops and mud clam), Cu 50mg/kg and Cr 2.0mg/kg. In order to support the suggestion, a seawater-sediment-shellfish biological model is established, and CdCl₂ is added in the seawater. The experiment which analyzes distribution of cadmium in different tissue of Meretrix meretrix, Tegillarca granosa, Sinonovaculla Constricta at different time point, is carried out under constant water temperature, obtaining accumulation rule of cadmium in these bivalve mollusc in seawater with different content of Cd. The distribution of Cd in different tissue is that Cd in seawater always enriches in visceral mass first and then translate to other muscle tissue. The results shows that there are no significant differences of content of Cd in sediment and shellfish meat between control group (natural seawater) and test group(seawater with 0.2μg/l, 1μg/l)(P>0.05). According to the limit of GB18406.4-2001(0.1mg/kg), most of Sinonovaculla Constricta in seawater with 0.2μg/l Cd are eligible, but others all exceed standard limits. There are significant differences of content of Cd in sediment and shellfish meat between control group(natural seawater) and test group(seawater with 5μg/l)(P<0.05).Concentration of Cd in Tegillarca granosa in seawater with 5μg/l Cd raised from 1.10mg/kg to 1.77mg/kg, and the enrichment hasn't reached equilibrium. Meanwhile, concentration of Cd in Meretrix meretrix keeps at 0.80mg/kg after 10 day. Content of Cd in Sinonovaculla Constricta which is lower than that in the others, stabilizes at 0.18mg/kg in the end. Content of Cd in Tegillarca granosa in the test group all exceed 1.0mg/kg, which confirms that the suggestion about Cd limits is reasonable. The enrichment experiment could offer data support for revision of related standard limits.