Effect Of Soil Acidification On The Environmental Behavior Of Sulfonamides

Driven by the rapid economic development of China,the rapid development of industry and agriculture led to acidification accelerated.The black soil region in Northeast China was one of the world's high-quality soil areas and the most important marketable base.In recent years,black soil acidification had been reported.The pH of the black soil was gradually declining,soil fertility was decreasing,soil surface was hardening,quality and yield of crops was declining.The Northeast black soil was facing the problem of"soil overdraft".With agricultural production,antibiotics could enter the soil through organic or farmyard fertilizers,threatening the soil,crops,groundwater,and even the health of humans.Therefore,in this paper,sulfadiazine and sulfachloropyridazine were selected as the research pollutants to study the effects of soil acidification on their adsorption-desorption and vertical migration.The main results are as follows:In this paper,OECD Guideline batch method was used to study the effects of soil acidification on the adsorption-desorption of sulfonamides.?1?The adsorption equilibrium of sulfadiazine and sulfachloropyridazine in control black soil and acidified black soil went through three stages:rapid adsorption,slow adsorption and equilibrium adsorption;the adsorption rate of sulfadiazine in acidified black soil in quasi-second-order kinetics was 26.9276 mg·g^-1·h^-1>control black soil 3.0083mg·g^-1·h^-1,the adsorption rate of sulfachloropyridazine in acidified black soil was216.2755 mg·g^-1·h^-1 and the control black soil was 15.7222 mg·g^-1·h^-1,soil acid-protective effect of the adsorption rate,the adsorption equilibrium time had little effect;?2?in the Freundlich equation and the Langmuir equation fitting effect had reached a significant correlation,sulfadiazine adsorption capacity in acidified black soil?K_f?was 1.16 times that of control black soil and sulfachloropyridazine was 2.34times of that of the control black soil,indicating that the acidified black soil enhanced the adsorption capacity and adsorbed the sulfadiazine significantly better,which was also in agreement with the maximum adsorption in the Langmuir equation?Q_m?;?3?The adsorption process was a spontaneous reaction mainly based on physical adsorption through the free energy of adsorption??G?,but the acidification made the|?G|increased system more stable and easier to carry out Spontaneously;?4?The addition of organic matter could increase the adsorption of sulfonamides,but the effect was not as good as that of the control black soil in acidified black soil;?5?The adsorption capacity of sulfanilamide in black soil decreased with the increase of the concentration of Ca²⁺.Under the action of Ca²⁺,it competed with Ca²⁺.The greater the ion concentration was,the stronger its competitive ability was,and the less it adsorbed to sulfa antibiotics.The soil column leaching method was used to study the downward migration of sulfonamide antibiotics in acidified black soil and the control black soil.?1?sulfonamide antibioticsl increased and then decreased with the increase of leaching amount.?2?with the increase of dosage,the amount of leaching increased.?3?the amount of the 2 sulfonamides in acidified black soil was lower than that in the control black soil,indicating that acidified black soil resulted in the increase of the amount of adsorption and the decrease of the amount of drenching.?4?Ca²⁺in the leaching solution played a role in fixing the sulfonamide antibiotics in 2 soils and decreasing their downward migration ability.