Effects Of Biochar On Sorption And Transportation Of Florfenicol In A Purple Soil

Currently,antibiotic contamination is increasing in drinking water,surface water,groundwater and soil in China.The antibiotic concentration detected in water and soil is at a high level,exceeding the recommended limits in the US and the EU,which has potential environmental risks.Biochar as a new kind of environmental functional material is considered to control antibiotic pollution.However,the binary system(soil-antibiotic or biocharantibiotic)has been a hotspot of current research,the ternary system of soil-biochar-antibiotic was ignored in stead.Therefore,the weak hydrophobic and highly migratory antibiotic Florfenicol(FF)and the mixed straw biochar as soil amendment ware selected in the study.A series of experiments had been conducted,such as spectroscopic characterization,batch,undisturbed soil column experiments and field plot experiment under real rainfall.There were used to understand the mechanism of biochar amendment on the control of transport of FF in soil by two-region physical-chemical nonequilibrium models by Hydrus-1D/2D.The effect mechanism of biochar on the sorption and transportation of FF in a purple soil was studied.The effects of biochar surface application and biochar permeable reaction wall on the transportation of FF was evaluated by observing under rainfall in plots.Therefore,application of biochar as an amending material should be further developed as a novel technology for soil pollution recovery and control,in the light of decreasing the risk of non-point source pollution by these emerging contaminants.The main results are as follows:Effects of biochar on physicochemical properties of purple soil.The application of biochar causes permanent and irreversible changes in the physical and chemical properties of purple soils.An increase of the p H,the TC,the OC,DOMs and soil porosity,saturated water conductivity of soil tillage layer,surface area of large pore unit volume,but a decrease of soil bulk density were obseraved by biochar soils.Effects of ageing on the properties of biochar.After one year of ageing in the field,there was a decrease of biochar surface elements,including C,Na,Mg,S,Cl and K,while an increase of O,Al and Fe.The elements Si.P remained relatively stable.Ageing increased surface area,average pore size,but decreased amorphous carbon content.And functional groups on the surface of biochar were hydroxyl,carboxyl,aliphatic and polysaccharide before and after ageing.The relative proportion of-C=O bond,and-C-O bond increased after ageing.Effect mechanism of biochar on sorption characteristics of FF in a purple soil.The sorption of FF on experimental soils are physical sorption(SFBC > SABC > S).The effect of solution/soil ratios and initial concentration on the sorption is greater,while the influence of temperature is not significant.The average sorption capacity of the fresh biochar and the aged biochar to FF is 1105.32 L/kg and 247.17 L/kg,respectively.The mechanism is partition and multi-molecular layer adsorption.The sorption mechanism of biochar on FF mainly includes assistant hydrogen bond and hydrogen bond,EDA,EAA and electrostatic interaction.Ageing caused the loss of hydrogen bond sites to reduce the sorption capacity.Effects of biochar on the transportation of FF in a purple soil.The transport of FF in the purple soil is affected by water flow.The water flow in undisturbed soil column can be simulated by two-region physical nonequilibrium model.The transport of FF can be simulated by two-region physical-chemical nonequilibrium model.Soil and water distribution coefficient and pore water velocity are the most sensitive parameters.The transfer of FF is based on physical nonequilibrium model,while the effect of the chemical nonequilibrium was enhanced after biochar application.The inhibition efficiency was 12.48%,and biochar should be used when the partition coefficient of polltions was less than 1.54 L/kg.but biochar application should be more than 0.77% wt.Inhibitory effect of biochar on transportation of FF in plots.The transport of FF in plots is mainly infiltration with less slope movement.The hydrodynamic dispersion effected by macropore and scaler in the highy complexity and heterogeneity soil with biochar application resulted in that the model can only be used for qualitative prediction at nearsaturation stage with high uncertainty.Biochar surface application and biochar permeable reaction wall effectively prevented the transportation of FF.The main mechanism was to improve the physical structure of soil,regulate the state of water flow and enhance the sorption capacity.