Effect Of Biochars On Adsorption, Leaching And Degradation Of Atrazine In Soils

The adsorption of pesticide by soil has a non-ignorable effect on some actions of pesticide in soil, such as degradation and leaching. Biochar has some characteristics of large specific surface area and developed pore structure, which increases sharply the adsorption to organic pollutant. For that reason, this study selected atrazine as the targeted pollutant, to investigate the effect of biochar which was prepared with two materials (sugarcane top and silkworm excrement) at 500 degrees Celsius on the adsorption, leaching and degradation of atrazine in soil, then exploring the potential and mechanism of this biochar in remedying soil polluted by atrazine.(1)The result of adsorption experiment indicates that these two kinds of biochars have strong adsorption capacity to atrazine. The adsorption capacity of sugarcane top biochar is higher than that of silkworm excrement biochar, which is up to 2177.97 mg·kg-1. Three kinds of non-bichar soil also have certain adsorption capacity to atrazine, and their adsorption capacities are arranged in order of size as follows:paddy soil、alluvial soil and moisture soil. Adding biochars to soil can greatly improve the adsorption capacity of these three kinds of soil to atrazine. The adsorption capacity of soil to atrazine which was added sugarcane top biochar is higher than that of adding silkworm excrement biochar, and the adsorption capacity to atrazine of soil when addition amount is 0.5% is more than that when addition amount is 0.2%.(2) The in lab simulation experiment studied the effect of biochar on degradation of atrazine in soil. Results indicate that different biochars have inconsistent influence on different kinds of soil. When adding sugarcane top biochar to different soil, the degradation of atrazine in any soil is delayed, and the half-time period is lengthened. In this experiment,0.5% sugarcane top biochar was respectively added to paddy soil, alluvial soil and moisture soil. The half-time period of atrazine in paddy soil, alluvial soil and moisture soil is respectively lengthened by 14.74 d,16.83 d and 17.52 d compared to control experiment, and the degradation of atrazine is also delayed when silkworm excrement biochar was added to alluvial soil and moisture soil, but it was promoted when in paddy soil. However, when the addition amount was 0.5%, the half-time period of atrazine in alluvial soil and moisture soil is respectively lengthened by 12.12 d and 12.74 d compared to control experiment.(3) The effect of two kinds of biochars on leaching and transport of atrazine in soil was studied using the method of simulated soil column leaching experiment. The results show that the essential physiochemical properties of soil are changed after adding biochars into the soil. Soil organic carbon (SOC) and cation exchange capacity (CEC) significantly increased. BCst has a great effect on inhibiting the transport of atrazine in the same soil. The higher content of biochars added in the soil, the stronger adsorption of atrazine by the soil and the less transport of atrazine, especially for 0.5% BCst. It is found that the addition of biochars has certain effect on inhibiting the main degradation products-DEA when determining the atrazine in leaching experiment. Comparing two types of soil, the leaching rate of atrazine in alluvial soil added with biochar is higher than that in moisture soil. The correlation analysis suggests that SOC and CEC in top soil (0-5 cm) have significant relationship with the content of atrazine in subsoil (15-20 cm) and the leaching of atrazine into groundwater. Biochars can be used as artificially added adsorbent to efficiently control the atrazine in the soil from leaching and migration.