Study On The Speciation And Accumulation Of Arsenic In Soil-Crop System

Arsenic was a toxic metal element,ore mining smelting and the use of pesticide and fertilizer containing arsenic can increase the risk of arsenic pollution.The high concentrations of arsenic can inhibit plant growth.At the same time,arsenic can be absorbed by the plant into the food chain,and damage human health.In view of this,the subject carries out arsenic in soil-crop system morphology and accumulation of law.Firstly,in order to better extract and separate the arsenic from soil and plant,the extractant is optimized.The result is that when 0.7%phosphoric acid+0.1 mol/L ascorbic acid is used as the extractant under the constant temperature rotation conditions at 20℃,the extraction effect is best.For the cabbage,under the condition of grinding and shaking,2mmol/L diammonium phosphate+0.2 mmol/L ethylenediaminetetra acetic acid disodium is used as the extractant,the effect is best.At the same time,the determination conditions of the speciation arsenic are optimized.Finally,When the mobile phase is 3%methanol+7mmol/L diammonium phosphate+0.5 mmol/L tetrabutylammonium bromide,the pH is 5.6,the Agela Venusil MP C18 column is selected,the carrier is 7%HCl,the reducing agent is0.5%KOH and 2%K BH4 and the negative pressure is 290 V,the effect of the arsenic analysis and determination is best.Secondly,in the pot experiment,only As(III)and As(V)are detected in the soil added with sodium arsenate,and no organic arsenic is detected.There is no inorganic arsenic converting into organic arsenic in soil,but it exists that As(V)can be converted to As(III).The concentration of As(III)and As(V)in soils increase with the increase of total arsenic concentration in soil.The plant arsenic availability in soil increases with the increase of total arsenic in soil.The ratio of As(III)to arsenic in soil showes a decreasing trend with the increase of soil arsenic concentration.The proportion of As(V)to arsenic in soil increases with the increase of total arsenic concentration in soil.Organic arsenic is not detected in the cabbage,only inorganic arsenic is detected.Inorganic arsenic in Chinese cabbage mainly exists in the form of As(III),the As(III)of Chinese cabbage in the proportion of the total arsenic forms is between 80.92%and 100%,while the As(V)of Chinese cabbage in the proportion of the total arsenic forms is between 0%and 19.08%.No As(III)and As(V)are detected in Chinese cabbage growing in CK soil.O nly As(III)is detected in Chinese cabbage grown in CK+10 soil,As(V)is not detected.As(III)and As(V)are detected in the Chinese cabbage grown in CK+40、CK+60 and CK+80 soil.The concentration of As(III)+As(V)in cabbages is between 0.038±0.003 mg/kg and 2.159±0.03 mg/kg,and the total concentration of As(III)+As(V)increases with the increase of total soil arsenic concentration.The highest concentration of As(V)in Chinese cabbage is 0.283±0.024mg/kg,which is found in the Chinese cabbage grown in CK+80 soil on 55th.The highest concentration of As(III)in cabbages is 2.01±0.026 mg/kg,which occurs Chinese cabbage grown in CK+80 soil on 25th.There is no uniform pattern of arsenic in Chinese cabbage.The concentration of As(III)+As(V)in cabbages(Y)and As(III)+As(V)in soil are linear regression Y=0.038X-0.129 R~2=0.825(n=12).