Study On The Effect Of Dissolved Organic Matter On The Photodegradation Of Phenanthrene In Water And Ice

In this paper,125 W high pressure mercury lamp was as light source,the photodegradation of phenanthrene in both water and ice at low temperature conditions was investigated.The photodegradation rate of phenanthrene in water and ice under UV irradiation,as well as the effect of initial concentration of phenanthrene,pH value and inorganic ions on photodegradation of phenanthrene,were investigated.The results showed that phenanthrene could be photodegradated in water and ice,with the photodegradation rate being faster in water than in ice.The photodegradations in both water and ice could be described by the first-order kinetics model and the initial concentration of phenanthrene,pH value and inorganic ions all had significant influence on the photodegradation of phenanthrene in water and ice.The photodegradation rate of phenanthrene in water and ice decreased with the increase of initial concentration of phenanthrene.The photodegradation of phenanthrene in ice was inhibited under strong acid and alkali conditions.Nitrite ions(NO2-)promoted the photodegradation of phenanthrene,while nitrate ions(NO3-)inhibited the photodegradation of phenanthrene,in both water and ice.The promotion and inhibition effects increased with the increase of NO2-and NO3-concentrations.Bicarbonate ions(HCO3-)inhibited the photodegradation of phenanthrene in both water and ice,and the inhibition effect increased with the increase of HCO3-concentration.Ferrous ions(Fe2+)inhibited the photodegradation of phenanthrene in water,and the inhibition effect decreased with the increase of Fe2+ concentration.On the other hand,Fe2+ had little effect on the photodegradation of phenanthrene in ice.In addition,125 W high pressure mercury lamp was as simulated daylight,the effect of four DOM(Elliott Soil Humic Acid(ESHA),Suwannee River Fulvic Acid(SRFA),Sewage DOM and Xinkai River DOM)on the photodegradation of phenanthrene and the changes of the properties of the four DOM were studied.The results showed that under the action of ultraviolet light,the five components of DOM and four DOM had inhibitory effect on the photodegradation of phenanthrene,and the inhibitory effect of Sewage DOM on phenanthrene was more than that of its five components.Singlet oxygen and hydroxyl radicals promote the photodegradation of phenanthrene.The size of the binding constant of DOM and components and phenanthrene reflects the size of the inhibition of phenanthrene.The greater the binding constant,the greater the inhibitory effect is.Under UV irradiation,the photodegradation of four DOM and five DOM components in the ice phase was high,and the photodegradation degree of Xinkai River DOM and HPO-N was the highest.Under the action of ultraviolet light,the contents of aromatic hydrocarbons in four kinds of DOM and five kinds of DOM components in ice decreased significantly.The UV-254 degradation rates of ESHA,SRFA,Sewage DOM and Xinkai River DOM were 66.31%,59.11%,48.29% and 54.87% after 3h irradiation,respectively.UV-254 degradation rates of HPO-A,HPO-N,TPI-A,TPI-N and HPI were 51.97%,55.63%,55.83%,44.96% and 46%,respectively.The degradation efficiencies of HPI and TPI-A were higher than that of the other three DOM components in the five components of Sewage DOM,and the degradation efficiency of all kinds of fluorescent substances of four DOM was not obvious in the process of photodegradation.Before and after freezing and thawing,the peaks of ESHA were consistent with that of SRFA,but the intensity was different.The presence of ESHA and SRFA was not disturbed by the presence of phenanthrene,but as for the intensity of the functional groups,phenanthrene had a certain impact.