Effects Of Dissolved Organic Matter Form Chicke Manure On Sorption-desorption And Migration Of Antibiotics In Purple Soil

With the development of intensive farming,the amount of antibiotics used in chickens has increased year by year,and antibiotic pollution has become increasingly serious.At the same time,a large amount of chicken manure was used as organic fertilizer and applied to farmland soil,which greatly increased the water-soluble organic matter(DOM)in the soil.The increase of DOM which is the carrier of pollutants migration in soil,will affect the environmental behaviors such as adsorption and migration of antibiotics in soil.In this study,the effects of chicken manure DOM on the adsorption and migration of sulfadiazine(SD),flufenicol(FFC),and tylosin(TYL)in purple soil were studied to provide a reference for the scientific application of chicken manure.And the effects of different ways of adding DOM to chicken manure(DOM pre-adsorption,DOM co-adsorption)on the adsorption and migration of three antibiotics in orchard soil and vegetable soil were studied by batch adsorption tests and soil column leaching tests.The main conclusions are as follows:(1)As for the physical and chemical properties of the soil,the static adsorption test shows that the adsorption of SD and FFC by orchard soil is higher than that of vegetable soil,and the adsorption of TYL by orchard soil is lower than that of vegetable soil.This is because the content of clay particles and organic matter in orchard soil is higher than that in vegetable soil,and organic matter interacts with SD and FFC active functional groups to promote adsorption,while blocking TYL adsorption sites to inhibit adsorption.(2)As for the effect of chicken manure DOM on antibiotic adsorption,the static adsorption test shows that the application of chicken manure DOM promotes SD and FFC adsorption and inhibits TYL adsorption.This may be due to the rich hydroxy,lipid,and amino groups which in chicken manure DOM forming hydrogen bonds with the carbonyl group of FFC and the amino group in SD to promote adsorption.While the rich proteinaceous material and short-wave humus in chicken manure DOM occupy more TYL adsorption sites or compete with TYL for adsorption,leading to a decrease in TYL adsorption.(3)As for the influence of chicken manure DOM addition order on antibiotic adsorption,soil column test showed that the leaching performance order of SD and FFC was DOM pre-adsorbed soil column<DOM co-adsorbed soil column(orchard soil/vegetable soil).Compared with DOM co-adsorbed soil column,the adsorption capacity of antibiotics in DOM pre-adsorbed soil column was larger.This is because the pre-adsorbed soil column contains more chicken manure DOM,which can be adsorbed with iron oxides on the soil surface to expand the effective soil adsorption area.(4)As for the types of antibiotics,the K_f value of TYL in the static adsorption test is much higher than SD and FFC.In the soil column test,the peak of SD and FFC penetration is between 84%and 98%,and the concentration of TYL penetration is lower than the detection limit.This is because there are electrostatic repulsions,hydrogen bonds,and van der Waals forces between the two antibiotics(SD and FFC)and the soil surface in this test,which results in a lower adsorption of SD and FFC.TYL is adsorbed in the soil by distribution,and the larger octanol/water partition coefficient leads to high TYL adsorption.(5)The two-point chemical CDE model can better simulate the dynamic leaching process of SD and FFC in purple soil.The simulation results show that the pore water velocity is one of the factors affecting the shape of the SD and FFC penetration curves in the filled soil column.After adding chicken manure DOM,the adsorption equilibrium time,the proportion of slow adsorption,and the kinetic adsorption sites of SD and FFC all increased.And the three values increased most significantly in the chicken manure DOM pre-adsorption test.