The Photodegradation Of DOM And It’s Effect On The Environmental Behavior Of Typical Contaminants

With the rapid development of the livestock industry, the amount of manureincreased annually. Dissolved organic matter (DOM) and unabsorbed antibioticscontaining in untreated manure will enter the environment through leaching and otherprocesses. As a mixture with active nature, DOM will change it’s propertitise throughphotodegradation, and has an effect on the photochemical behavior of other pollutantsin environment. At the same time, antibiotics and it’s metabolites are highlyhydrophilic and biological stability. They can migrate and accumulate in theenvironment, then have negative influence on human health. Therefore the researchabout photodegradation behavior of manure DOM and antibiotics, and the influenceof DOM on the photodegradation of antibiotics in the environment has greatsignificance.In this paper, DOM was produced by a chicken farm manure and DOM’sphotodegradation behavior and nature in aqueous and ice was studied. Studied theeffect of DOM’s photodegradation on the binding property of DOM with Cu2+/Zn2+And studied the photodegradation of tetracycline (Tetracycline, TC) in aqueous andice, which is a typical representative to the most widely used tetracycline antibiotics.The influence of DOM’s photodegradation on the photodegradation of TC was studiedalso in this paper. Then we get the following conclusions:(1) In the water phase+UV system, the photodegradation rate of DOM in5-40mg/L increased first and then decreased when increased it’s concentration,and20mg/L DOM has the highest photodegradation rate; the photodegradation rate of DOMwas inhibited in acidic and alkaline conditions, but was promoted in highertemperature.(2) Under exposure in UV, the photodegradation rate of20mg/L DOM after beinglighted48h was85%in the water phase. However, under simulated sunlight, in thewater phase and ice phase, the photodegradation rate of DOM was only7.2%and4.5%, respectively.(3) Under the simulated sunlight and UV in water phase, the aromaticity, thecontent of humic substances and fulvic substances of DOM decreased over irradiation time; in the ice phase+simulated sunlight system, freezing and thawing andphotodegradation made the aromaticity of DOM reduce.(4) In three systems, the pH of DOM decreased over irradiation time, but in thewater phase+UV systems, pH reduced more significantly than the other two systems.(5) The percentage of molecular weight>35000Da of DOM decreased, and thepercentage of medium molecular weight increased under UV light and simulatedsunlight in aqueous phase, especially in the ultraviolet conditions, the percentage ofmolecular weights>35000Da decreased more significantly. However no significantchange of molecular weight distribution was observed in ice phase+simulatedsunlight system.(6) The binding coefficients of DOM with Cu2+and Zn2+declined over irradiationtime in the aqueous phase+simulated solar light/ultraviolet conditiongs, while itdidn’t changed significantly under ice phase+simulated sunlight condition.(7) The degradation of TC in5-40mg/L followed first-order kinetics in both waterand ice phase, and degradation rate was higher in former system.(8) Adding DOM promoted the photodegradation of20mg/L TC under both twosystems, but the promotion in water+simulated sunlight condition was more obvious,and the DOM, which was exposed in light under different time, played different rolesin promoting the degradation of TC.