Effects Of Dissolved Organic Matter Form Pig Manure On Sorption And Migration Of Antibiotics In Purple Soil

Since the advent of penicillin in 1929,antibiotics have been widely used in many fields such as the treatment and prevention of human and animal diseases,and the addition of livestock feed.With the rapid development of intensive aquaculture in China,the application of a large amount of livestock manure will bring a large emission of antibiotics and dissolved organic matter(DOM)into the soil.For the migration of trace organic contaminants in the soil environment,DOM can act as a “carrier” or “cosolvent”,it will directly affect the environmental behaviors such as adsorption and migration of antibiotics in the soil.So this article selects purple soil on the cultivated land and orchard in Sichuan hilly area as the research objects,and use batch and column experiments to study the effects of pig manure(PM)DOM on the adsorption-desorption and migratory behaviour of four antibiotics(sulfadiazine,florfenicol,tylosin,norfloxacin),which has different physical and chemical properties.The main results are as follows:(1)In terms of the adsorption characteristics of antibiotics in purple soil: the adsorption capacity of four antibiotics followed the order of SD < FFC < TYL < NOR,and the maximum adsorption capacity(Qm)of SD,FFC and NOR in the orchard are higher than that in cultivated land,but for TYL the difference of Qm is not obvious in the two types of soils.(2)In terms of the add order of PM-DOM: when the antibiotics and PM-DOM are added to the soil at the same time,the adsorption of four antibiotics both increased significantly in cultivated land and orchard soil(except NOR in orchard soil)compared with the control group,this is a result of the combined action of cumulative adsorption,co-adsorption,solubilization and competitive adsorption,the net effects of the various effects of adding different concentrations of PM-DOM are different;when the soil pre-adsorb DOM before antibiotics introduction,the adsorption of SD and FFC is inhibited we hypothesized that excessive exogenous organic matter may block the adsorption sites on the surface of clay minerals,but the effect of pre-adsorption on TYL and NOR is not obvious,this is because its adsorption coefficient in the soil is much higher than that of PM-DOM,so the competitive effect between DOM and antibiotics may not be the main mechanism affecting its adsorption.(3)In terms of the desorption characteristics of antibiotics on purple soil: the antibiotics in the purple soil have nearly no desorption hysteresis except NOR in control sloping land and SD in cultivated land pre-adsorbed with DOM,it was observed that the hysteresis coefficient of NOR increased after adding PM-DOM.(4)For the results of the breakthrough curves(BTCs)in the soil column: the peak penetration of SD and FFC in sloping farmland is lower than that of orchard soil;when the antibiotics and PM-DOM are added to the soil at the same time,the highest concentration of SD or FFC in the outflow decrease and the first-order kinetic rate constant(f)reduce compared with the control;while in the cultivated land and orchard soil pre-adsorbed with DOM,the peak value of antibiotics decreases and increases,respectively(5)For the results of soil column leaching results: after leaching,the total residual amounts of the four antibiotics in the purple soil column were NOR > TYL > FFC > SD successively;NOR and TYL have strong adsorption properties,the residual amount in the surface soil of 0-3cm accounts for more than 92% and 77% of the total adsorption amount,however,the adsorption capacity of FFC and SD is low,and there is no obvious difference in the residual amount at each depth;The residual amount of antibiotics when the antibiotics and PM-DOM are added to the soil at the same time in most treatments,and the effect result of soil column pre-adsorbed with DOM is opposite.