Enhanced Sorption Of Atrazine To Soils Amended With Biochars

Atrazine, as one of most widely used herbicides in the word, caused significant concern due to its pollution and harm. Therefore, controlling and removing atrazine in soils has attracted extensive studies. Biochars, as a new environmental materils, used to control and eliminate pollutants in environment becaused of its high sorption capacity. In this dissertation, research advance on the sorption of organic pollutants onto soils and biochars was reviewed, and then the enhanced sorption of atrazine to soils amended with biochars for mitigation and restoration of soil atrazine contamination was studied. Sorption characteristics and contributions of organic matter fraction for atrazine in soils were studied, and sorption capabilities, sorptive mechanism of biochars for atrazine were elucidated. Furthermore, enhanced the sorption of atrazine to soil amended biochars were revealed. These results provide a theoretical basis for assessing atrazine’s environmental risk and using biochar to remedate contaminated soil. The main original conclusions of this work are drawn as follow:(1) Atrazine sorption isotherms by organic matter fractions were well-fitted to the Freundlich equation and sorption capacity followed the order HA1>HA2>DM>HM. The organic carbon normalized distribution coefficients (LogXoc) were significantly related to (N+O)/C ratios and H/C ration of the extracted SOM fractions, especially the (N+O)/C ratios, demonstrating that the polarity of SOM fractions dominates atrazine sorption by polar interaction (e.g., H bonding). The combined contribution of HA fractions in their respective soils was higher than that of HM although their lower content in SOM.(2) Atrazine sorption isotherms by biochars were well-fitted to the Freundlich equation and sorption capacity, nonlinear of sorption isotherm were increase with the pyrolysis temperature (300-700 ℃). The distribution coefficients (LogKF) were significantly related to (N+O)/C ratios, H/C ration and SSA of the biochars. Atrazine sorption by biochars prepared under low temperature inceaseing as the pH value increased, then decreasing, while sorption capacity of the biochar preparaed under high temperation decreasing with the pH increased. The salinity and envrimental temperation of solution promted the sorption capacity of biochars, and heavy metal ions inhibited the adsorption of atrazine.(3) Biochars can significantly enhance the adsorption of atrazine by soils, with a 79-fold and 34-fold increase in distribution coefficients (KF) when adding 2% RC700 to PS and BS. KF increased exponentially with the inceased sorption capacity and amount of biochars. Furthermore dissolve organic matters (DOM) can significantly suppress adsorption of atrazine on biochars. KF value decreased about 2/3 when the concentration of DOM was 100 mg/L. Atrazine was preferentially adsorbed to biochars and the combined contribution of biochar is greater than that of soil when soil was mixed with biochars.