Effects Of Soil Properties On Arsenic And Soil Enzymes Relationship

Arsenic(As) is a kind of metalloid element widely existing in soil, which has been identified as carcinogenic substances by WHO.With the rapidly development of social economy, industrial wastes discharge disorderly, the extensive use of arsenical pesticide and fertilizer,and the lack of awareness of environmental protection has lead to soil degradation, plant growth and put threats to human and animal health through the food chain lastly.Therefore, soil arsenic pollution has caused wide attention of governments and scholars.Soil enzymes are involved in many important biochemical processes in soil,closely related with the material circulation,and are often used for soil pollution assessment.Soil phosphatase and dehydrogenase can characterize soil phosphorus nutrition and microbial activity to a certain extent because of involving in the transformation of phosphorus and hydrogen transfer.Due to a variety of soil factors, the effect of arsenic on the two enzymes are greatly different after arsenic into soil.In recent years,researchers have paid more attention on the relationship between heavy metal and soil enzyme. But they are mainly focused on the effect of arsenic on one or several soil types, and lack study of different valence arsenic.Therefore, by laboratory simulation experiment,we investigated the correlation and tried to find the main factors affecting the relationship between soil enzymes and different valence arsenic using 14 representive soil types from China.The main conclusions are as follows:(1)Soli enzyme activity were related with soil organic matter, available phosphorus, CaCO3, cationic(CEC) and clay contentin different soil types.The correlation analysis showed that the acid phosphatase activity was significantly correlated with soil organic matter, and the correlation coefficient was-0.914**;Alkaline phosphatase and dehydrogenase activity were significantly correlated with pH, the correlation coefficients were 0.908**,-0.665**, respectively.(2)As(III) inhibited the activity of dehydrogenase, while had no effect on soil phosphatase activity.Low concentration of As(V) and As(III) activated soil phosphatase and dehydrogenase activityin part of soil,but the soil phosphatase and dehydrogenase activity decreased with the concentration of As(V) and As(III) increased.(3)Model v=a/(1+exp(b(i-c)))can better describe the relationship between As(V) concentration(i)and phosphatase activity(v); Model v=c(1+ai)/(1+bi) and Model v=a/(1+bi) dehydrogenase activity(i), respectively.Ecological dose 10%(ED10) of phosphatase is higher than dehydrogenase on average, indicating that dehydrogenase is more sensitive to the pollution of As(V) and As(III), and could be the index of arsenic pollution monitoring.The pollution of arsenic(V) of soil phosphatase ED10 is higher than the dehydrogenase on average, dehydrogenase is more sensitive to the pollution of As(V) and As(III), could be the index of arsenic pollution monitoring.(4)The acidic soil dehydrogenase ED10 was higher than alkaline soil under As(V) pollution,while As(III) was on the contrary,showing that the buffer capacity of alkaline soil was stronger than acidic soil under As(V)pollution.(5)Soil organic matter was the main factor affecting the relationship between As(V) and phosphatase activity,and increasing the content of organic matter could decrease As(V)toxicity on phosphatase.CEC and pH was negatively related to dehydrogenase ED10 value under As(V) pollution.