The Accumulation And Transformation Of Inorganic Arsenic In The Muscle Of Oreochromis Niloticus

Arsenic is a toxic metal-like element,widely found in waters such as oceans,rivers and lakes.Since fish live in aquatic environment,they are extremely susceptible to arsenic pollution.Fish generally absorb and accumulate arsenic from water through gills,skin and other organs,or by ingesting food containing arsenic.Fish continue to bioaccumulate and biotransform arsenic in their bodies through digestion and metabolism.In this study,the freshwater tropical fish Nile tilapia（Oreochromis niloticus）was selected as the research object.We exposed Oreochromis niloticus to an aqueous solution of 1 mg/Larsenate（As（V））to investigate how the change of water temperature,dissolved oxygen（DO）,and p H influenced the accumulation and transformation of arsenic in the fish.At the same time,we fed Oreochromis niloticus with Lemna minor L.,Hydrilla verticillata,and Macrobrachium nipponense which exposed to 1 mg/L As（V）before feeding.In both cases,total arsenic content and arsenic speciation in the muscle of Oreochromis niloticus were detected.The purpose of the study was to reveal the mechanism of arsenic accumulation and transformation in Oreochromis niloticus when exposed to waterborne arsenic and food borne arsenic.This study found that:（1）Oreochromis niloticus had no significant changes in body length,wet weight and fullness before and after exposure（P<0.05）which lasted 45days;The arsenic content in the body increased with the increase of exposure time and reached balance content about 5.20 μg/g after 15-20 days.（2）Higher temperature（34℃）and dissolved oxygen（7.86±0.18 mg/L）could promote the accumulation of arsenic in water by Oreochromis niloticus;at the same time,the high temperature and high oxygen environment could promote the metabolism of the fish,and promote the conversion and detoxification of arsenic by the fish.（3）The weakly acidic water environment of p H around 6 would weaken the activity of the fish and reduce the metabolic intensity,which would reduce the accumulation and transformation of arsenic in the fish.（4）The accumulation of arsenic in the three kinds of foods from large to small was as follows: Lemna minor L.> Hydrilla verticillata> Macrobrachium nipponense.In their bodies,the content and proportion of arsenate,arsenite [As（III）],dimethyl arsenic（DMA）,and arsenic betaine（As B）,were different;among them,aquatic animals are more likely to methylate or convert inorganic arsenic into less toxic As B.When Oreochromis niloticus exposed to food containing arsenic,the accumulated arsenic content in its muscle tissue showed same trend as the the arsenic concentration in the food.（5）Different food types,different living environments or different exposure time may cause different species of arsenic to produce in fish muscle tissue;Oreochromis niloticus accumulated and transformed arsenic at a higher rate when exposed to food than that when exposed to water.