Analysis Of Heavy Metal Pollution And Affecting Factors Of The Typical Economic Shellfish In Beibu Gulf Of Guangxi

The Guangxi Beibu Gulf economic zone is experiencing fast development,and heavy metals contamination for aquaculture has become a serious problem in the region.Bivalves always contain high level of heavy metals and exceed the food standard and cause food safety problems.In this study,bivalves smaples were collected from the coast areas of Beibu Gulf in Guangxi,including Dongxing,Fangchenggang,Qinzhou,Beihai and Weizhou Island,from September 2014 through November 2015.Contents of Zn?C u?Pb?Cd?Cr?Hg and As were thus determined.According to Maximum Levels of Pollutants in Foods about National Food Safety Standard(GB 2762-2012)and The Pollution-free Food Containing Poisonous and Harmful Materials Set Limits to the Aquatic Products(NY 5073-2006 and Australian Food Standards Code),heavy metals contamination for shellfish were evaluated using the single factor index method and provisional tolerated weekly intake method.The objective of this study is to demonstrate heavy metals contents in bivalves along the coastal of Beibu Gulf in Guangxi,and understand their interspecific,temperal and spatial distribution in the region.The present shellfish pollution by heavy metal level poses a threat to Guangxi Beibu Gulf.The percent of passing is only 40.15%;elements of Zn,C u,Cd,As exceed the standards with 0.75%,7.58%,7.30%,49.24% respectively beyond the criterion.Element of As pollution is the most serious,thus needs to be strengthened for monitoring in the future.The single factor evaluation on shellfish shows all the pollution index of C u and Cr for crassostrea rivularis' digestive gland,Zn,Cd and As for Scapharca subcrenata's digestive gland,and Zn for Atrina vexillum's digestive gland are higher than one.Therefore,we strongly recommend to avoid consuming these shellfish's digestive gland.According to the exposure assessment of Beibu Gulf Economic Shellfish diet,dietary intake of heavy metals is generally safe,but Cd and As pose more serious potential threat on diet than others.The accumulation of heavy metals exhibits an interspecific difference among shellfish samples.Crassostrea rivularis and Atrina vexillum have high enrichment of Zn;Crassostrea rivularis have high enrichment of Cu.Atrina vexillum,Chlamys nobilis,Mytilus galloprovincialis easily accumulate Cd.In addition,Solen grandis,Solen dunkeriana,Perna viridi,Nucula donaciformi,Atrina vexillum,Lutraria siebaldi,Glycymeris vestita,Mytilus galloprovincialis accumulate As seriously.The accumulation of heavy metals aslo shows a temperal and spatial distribution among shellfish samples.Contents of Zn and C u for Crassostrea rivularis,and Zn for Atrina vexillum are higher in spring and summer than in autumn and winter.On the contrary,Pb doesn't show an obvious seasonal distributions.Shellfish of Paphia undulata?Crassostrea rivularis?Atrina vexillum?Chlamys nobilis?Meretrix lyrata contain bigger Cr,Hg,Hg in winter than in other seasons.In general,shellfish from Q inzhou and Beihai have worse heavy metal pollution than Weizhou,Fangchenggang and Dongxing.The seawater environment where shellfish is cultured can affect the extent to which heavy metal is accumulated by shellfish.Cerrelation analysis between contents of heavy mental for crassostrea rivularis and seawater environment index illustrates Zn,Cu in seawater are positively correlated with these elements for crassostrea rivularis;seawater salinity has a negative correlation with heavy metal for this organism,but no rerrelation for water temperature,pH,and dissolved oxygen are observed in this study.