Modeling Typical Antibiotics Sorption To Soils

Antibiotics have been widely used throughout the world,which,however,would make them carried into farmland soils through multiple exposure pathways.Then they would be adsorbed through a variety of mechanisms and remained in the soil.This process could be influenced by all the basic physicochemical properties of soil,such as pH,organic matter,cation exchange capacity(CEC)and other factors.Among them,CEC is one of the most important one.Hence,it is of great theoretical and practical significance for environmental risk assessment and pollution control of antibiotics,to explore the influence of different basic soil properties on the antibiotics adsorption behavior in soils and to establish a predictive model.Basic physical and chemical properties of the soil samples,including pH,cation exchange capacity(CEC),organic matter(OM),particle size composition(the composition percentage of clay,silt,and sand)and dissolved organic matter(DOM),were determined in this study,to investigate the distribution of these properties and prediction of soil CEC.Meanwhile,three major classes of antibiotics,enrofloxacin(ENR),macrolide tylosin(TYL)and sulfonamides(sulfamonomethoxine(SMM),sulfaguanidine(SGD),and sulfathiazole(STZ))were selected,using batch equilibrium adsorption test methods,to study the adsorption distribution of five antibiotics under the original soil pH,and the effect of different soil properties on the adsorption distribution process.The measurement results indicated that the tested basic physical and chemical properties of the soil samples showed some differences.The pH ranges 4.69 to 8.45,and the OM ranges9.75~150 g/kg.The CEC ranges from 6.63 to 41.65 cmol/kg.A multivariate linear regression method was used to establish the soil CEC prediction model.The prediction results demonstrate that the model linear R~2 is 0.374 and the forecast R~2 is 0.520,which is significant(P<0.05)and may provide some reference for CEC prediction research.The adsorption distribution coefficient of enrofloxacin is between 649.87 L/kg and14637.15 L/kg,much greater than tylosin and sulfonamides.The results of adsorption model established by stepwise multiple linear regression indicate that pH and CEC are the main factors of enrofloxacin adsorption.The linear R~2 of this model is 0.703 and Q~2 is 0.635,showing good stability and accuracy.The K_d value of Tylosin adsorption distribution is between 1.00 L/kg to 216 L/kg,The model established by stepwise multiple linear regression indicates that CEC and DOM are the most important factors affecting tylosin adsorption.The linear R~2 of this model is 0.418 and Q~2 is 0.374.The K_d value of the sulfanilamide antibiotics is0.20 L/kg to 12.65 L/kg.