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Assessment of Security and Quality of Heavy Metals Residue on Main Tidal Cultured Shellfish of Ningbo Bay

Author: KangFeiJin
Tutor: YouZhongJie
School: Ningbo University
Course: Marine biology
Keywords: Ningbo ridal shellfish seiment sea water heavy metal relativity assessment category
CLC: X174
Type: Master's thesis
Year: 2011
Downloads: 193
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Abstract

The research based on the date of environmental survey and cultured shellfish which are obtained from Ningbo in 2009 while accompanied by monitoring data in 2008. The data of superficial sediments,sea water and the heavy metal contents(Cu, Pb, Cd, Hg, As) of 3 types of the cultured shellfishes(Saccostreae cucullata,Sinonovacula constricta,Tegillarca granosa ) from 18 representative areas of Ningbo are analysed and assessed by SPSS 13.0. Analysing the relativity between the pollution level of heavy metal in cultured environment and the pollution level in the cultured shellfishes, furthermore, classifying and assessing the environmental quality of the tidal shellfish culture area.The main conclusions are as follows:There are significant differences among different types of shellfishes through analysed the data of the heavy metal survey of 3 types of cultured shellfishes. The contents of Cu and Cd in Saccostreae cucullata are over proof, so were the content of Cd in Tegillarca granosa. The content of heavy metals of Sinonovacula constricta are all below the standard limits,its food safety is good. There is significantly difference among the contents of heavy metals of 3 types of shellfishes in different areas. The contents of different shellfishes show obvious change within different seasons, the enrichment of heavy metals of Tegillarca granosa reveals mainly in Summer>Spring>Autumn. The enrichment of heavy metals of Saccostreae cucullata and Sinonovacula constricta in spring are generally more than in summer and autumn.The average content of Cu, what is one of the superficial sediments in Ningbo Bay, has exceed the value of the first degree of Oceanic Sediments Quality. The contents of other heavy metals are all lower than the value of the first degree of Oceanic Sediments Quality, while higher than the background value mostly. The date of heavy metal contents of sediment are analyzed for two-factor analysis of variance by the factors of station and element. The results show significant difference among different stations as well as in different heavy metals. Utilizing the potential eco-risk index and the Geo accumulation index to assess the pollution level of the superficial sediments of the culture environment. The pollution level of whole area belongs to the light level; the environment of sediment in culture area reaches the standard, all these conform to the basic condition of tidal shellfish culture. The PRIMER5.0 is used to analyse the Bray-Curtis similarity matrix of stations and indicators which from the environment of sediment in culture area of Ningbo. The results show that 18 stations can be divided into 3 groups, and there is a higher degree of similarity between sampling stations. These 6 heavy metals can be divided into 2 categories.The contents of heavy metals in sea water of Ningbo are all under the Fisheries Water quality standard except the content of Pb, which exceed value of the first degree of Oceanic Sediments Quality. It can be concluded that the phenomenon of surpass is very seriously. The average contents of 5 types of heavy metals in July and August are higher than those in March and April, the content of Pb is even more than twice as high in low water period. Differences between different stations and elements of sea water were tested using a two-way ANOVA for no repeated measures. The results show no significant difference among different stations, and significantly differ from different elements. The quality of sea water in shellfish culture areas of Ningbo stand in an advance level, according to the Nemerrow comprehensive pollution index, suitable to breed of shellfish.Researching the relativity between the heavy metal content of cultured shellfish and environment of culture, the results show that the the heavy metal contents of cultured shellfish related with cultural environment. The relativity between shellfish and sea water is more obvious than sediment. The relativity between the heavy metal contents of Saccostreae cucullata and Tegillarca granosa and sea water are more significant than the relativity between sinonovacula constricta and seawater. The relativity between the heavy metal contents of Saccostreae cucullata and the superficial sedmients is more significant than Sinonovacula constricta and Tegillarca granosa.The eco-environmental quality of shellfish culture areas of Ningbo Bay is assessed.It ranged between grade 3 and 5,at a mean of grade 4, which is at a general level. The eco-environmental quality of shellfish culture areas is categoried, the results show that all of 18 stations belong to the second class. In addition, there are 8 stations belonged to 2a class,which are relatively clean, occupying 44% of all areas. 5 stations belong to 2b class which are lightly polluted and occupied 28 % of all areas.The rest belong to 2c class which are medially polluted.

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