Toxicity of As on soil neutral phosphatase was studied through a series indoor incubation experiments. Results showed that the activity of soil neutral phosphatase was significantly inhibited by As pollution, and the peak inhibiting ratio was appeared at the sixth incubation day. While the activity of soil neutral phosphatase was also decreased with concentration of As increasing in the same incubation day. The relationship between the concentration of as and soil neutral phosphatase was fit by model ①y=c/(1+bx)and ②y=c(1+ax)(1+bx).The model② was more suitable to describe the relationship between the concentration of As and soil enzyme. This means the effect mechanism of As on the soil neutral phosphatase was part of inhibition. The Km of neutral phosphatase was increase by As concentration adding, while the Vmax was lowered. This kind of inhibition belongs to mix competition inhibition. Phosphatase widely exists in the biological world, from lower organism Escherichia coli, yeast to higher animals and plant tissues, body fluid and human liver, prostate gland are found to have phosphatase exist. It can catalyze the phosphate hydrolysis of elemental and inorganic phosphate release, important enzymes of biological phosphorus metabolism [1-2]. Soil phosphatase is an enzyme that has a major impact on agricultural production, producing an important role in the cycle of soil phosphorus. Research show that phosphatase in soil and aquatic systems of phosphorus, organic phosphorus pesticide contaminated soil bioremediation is very important, so it can be used as material for ecosystem beneficial or deleterious effects of indicator. Therefore, some can be as the instructions of the beneficial or harmful effects of ecosystem biology. Arsenic is widespread nature of toxic heavy metals often pollute the environment with the waste material, pesticides, fertilizers and other. According to the statistics in early 1990s, each year around the world due to human activities the importation of soil arsenic content of 0.52-1.2 million tons, its impact on soil ecosystem is one of the important topics. This experiment which proposed indoor simulation method analysis different concentrations of arsenic contaminated soils of neutral phosphatase activity, to explore the effects of different concentrations of arsenic on soil phosphatase activity of short-term toxicity effect. Analysis of the influence degree and duration, further analysis between the two possible mechanism, provides the basis for environmental protection and monitoring.
Land use dynamics in the Brazilian Cerrado in the period from 2002 to 2013