| Arsenic?As?is widely distributed in the nature of a metalloid element,as the content of 25 mg/kg in the Earth crust.At present,the arsenic pollution in soil does harm to the ecological environment and crops has aroused extensive attention.In order to investigate the toxicity mechanism of arsenic to the environment,we selected sodium arsenite?NaAsO2?as an exogenous pollutant to study its ecotoxicological effects on earthworms and leeks and its migration and transformation in soil.The acute toxicity of sodium arsenite to earthworms was determined by filter paper contact method and artificial soil method.The LC50 values were 2.01×10-4 mg/cm2 and 121.99 mg/kg,respectively.Which provides evidence for arsenic poisoning in pot experiment.The results showed that the plant height,biomass and chlorophyll content of leeks decreased from high to low in the order of 10>CK>40>80 mg/kg at 28dth,and the biomass of earthworm decreased gradually.The order of biomass was 10>CK>40>80 mg/kg,and the response of physiological indexes and earthworm biomass to arsenic concentration were low stimulation and high inhibition.Earthworms had inhibition to the growth of leek.As for the enrichment effect,the enrichment coefficient of arsenic to earthworm was more than 3;the content of arsenic in leek leaf was more than 0.05 mg/kg,and the content of arsenic in leek root was more than 0.2 mg/kg.The SOD activity and MDA content were positively correlated with the arsenic concentration,POD activity was negatively correlated,and the CAT activity had a low stimulation and high inhibition to the arsenic concentration in response to oxidative stress.There was a positive correlation between the activity of SOD and the content of MDA and the concentration of arsenic,the negative correlation between CAT activity,and POD CAT activity had a low stimulation and high inhibition to the arsenic concentration in response to oxidative stress.The factors of earthworm have adverse effect on the enzyme system of leek.The content of arsenic in the soil was positively correlated with the concentration of arsenic in the arsenic content and form index.The addition of exogenous arsenic decreased the fraction of residue arsenic in the soil,while increased and the fraction of Fe-As and Ca-As.Earthworms can promote the transformation of residual arsenic into other forms,and increase the soil arsenic bioavailability.In this paper,we study the enrichment and toxic effects of NaAsO2 in soil,earthworms and leeks,the migration and transformation of arsenic in the soil and the ecotoxicological study of earthworms and leeks.We preliminary recognize of arsenic in soil and to explore the arsenic toxicity to the biology,which can provide references for arsenic pollution prevention and control in agricultural production. |
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