Study On Transfer Characteristics Along Food Chain And Removal Methods Of Different Arsenic Species In Water

Arsenic（As）is a common toxic substance that poses health and ecological risks to humans and the environment.The toxicity of inorganic Asis higher than organic As,and the toxicity As（Ⅲ）is higher than As（Ⅴ）.Monomethyl arsenic（MMA）,dimethyl arsenic（DMA）are less toxic,and arsenic betaine（AsB）are generally considered nontoxic.Fresh water and oceans in chinese are seriously polluted by As,and freshwater fish are enriched with high concentrations of inorganic Asand AsB.Meanwhile,fish are important sources of Asfor human beings,and thus consuming fish contained Asconcentration may cause potential risks to human health.The purpose of this study is to:（1）investigate the uptake,biotransportation and biotransformation of As（Ⅴ）into zebrafish in freshwater environment and the accumulation mechanism of Asin zebrafish.（2）simulate the transportation of different species of Asalong the food chain（fish to mice）,compare the characteristics of AsB and inorganic Asin different mouse tissues and analyze whether the consumption of fish with high Asconcentration poses a potential health risk to human body.（3）synthesize a convenient and efficient modified biochar to adsorption inorganic Asfrom water,protect human health,and make contributions to water environment purification.In view of the above research objectives,this paper carries out research from the following three aspects:1.In order to explore the bioaccumulation of As（Ⅴ）in freshwater fish.Zebrafish were exposed to As（Ⅴ）in waterborne for 16 days and depurated for 16 days.Gills,intestines,liver,head and carcass were collected to measure total arsenic and species;the PBPK model was constructed to simulate the absorption,transportation and transformation of As（Ⅴ）in waterborne of zebrafish.These results showed that instead of the gills,the intestines were indicated as the main uptake tissues.However,the intestines showed a weak capacity to biosynthesize AsB.The liver can detoxify and exchange Asto maintain a balance.The head and carcass serve as the main storage tissues,with AsB as the predominant form and inorganic Asalso present in relatively high proportions.This study provides new insights into the differences between freshwater fish and marine fish relevant to the bioaccumulation of inorganic As.Therefore,high As（Ⅴ）uptake in the intestines and lack of biotransformation contribute to high bioaccumulation of inorganic Asin freshwater fish.Our results provide a theoretical basis for assessing the risk of inorganic Asaccumulation in freshwater fish ingested by humans.2.Marine fish have higher rates of AsB than freshwater fish.In order to explore the transmission characteristics of different species of Asalong the food chain,goby collected from Yangjiang and Zhanjiang were selected as the AsB sources of mammals.In this study,C57BL/6J mice fed five different diets containing marine fish muscle and food spiked with different proportions of inorganic Asand organic Ascompounds.The bioaccumulation and bioavailability of different Asspecies were significantly affected by different diets.Inorganic Asingested from diets was effectively absorbed by the GI tract because it might bind to keratin in the gastrointestinal mucosa and then accumulate in major tissues,followed by a series of oxidation,reduction and methylation processes.AsB exhibited higher bioavailability in the kidney and liver,as it was efficiently assimilated and less efficiently eliminated in the kidney and liver.Meanwhile,As（Ⅴ）was also detected at relatively higher concentrations and percentages in these two tissues.Thus,differences in the bioavailability and target organs of inorganic Asand AsB were observed in mice,leading to potential tissue-specific health risks.Therefore,the health hazards to target organs must be considered when coastal populations consume large amounts of marine fish.3.In this study,modified biochar ZrFe-BC2 supported by zirconium oxide（ZrO₂）and iron oxide[Fe O（OH）,Fe₂O₃,Fe O]was synthesized by co-precipitation method,which improved the removal performance of As（Ⅲ）and As（Ⅴ）in water.SEM,FTIR,XRD and XPS analysis showed that Fe and Zrwere successfully loaded onto the surface of biochar and formed a large number of positively charged Fe-O and Zr-O groups.The maximum adsorption capacity of ZrFe-BC2 on As（Ⅲ）and As（Ⅴ）is 46.7 and 47.8 mg g^-1,respectively.Different pH（3-11）has little influence on the adsorption effect.Except PO₄^3-and HCO₃^-,other coexisting anions Cl^-,SO₄^2-and NO₃^-have weak adsorption competition effect.These results show that ZrFe-BC2 is a promising adsorbent for removing As（Ⅲ）and As（Ⅴ）from water.In conclusion,freshwater fish can absorb As（Ⅴ）in water and convert it into non-toxic AsB.However,a high proportion of toxic inorganic Asstill contained.After mammals uptake fish rich in various forms of arsenic,inorganic arsenic mainly accumulates in the gastrointestinal tract,and AsB mainly accumulates in the liver and kidney,resulting in the transmission of Asfrom fish to humans along the food chain may cause tissues-specific health risks to humans.Therefore,in order to reduce the high concentration of Asin the water environment,modified biochar（ZrFe-BC2）was synthesized,which has a good adsorption effect on the high concentration of As（Ⅲ）and As（Ⅴ）in water,and can be used to reduce the Aspollution in water,so as to reduce the potential threat of arsenic transmission along the food chain to human beings.