Photochemical Degradation Of Petroleum Pollutants In Soil

In order to study photochemical transformation of petroleum pollutants in soil, photochemical reactions of crude oil on soil surface in simulated conditions were studied, which made it available to investigate its migration and transformation regulations in soil.(1) Oil was added into the soil to simulate ground crude oil, the crude oil volatile situation was measured, oil components variation was analyzed with GC-MS. The experiment results showed that the crude oil move downward infiltration along vertical direction as well as volatile to the atmosphere after enters the soil. About80%of the crude oil ultimately remained in the soil to form a long-term petroleum contamination.(2) Photochemical experiments with soil layer was conducted, the results showed that oil content in soil obviously affected the photo-degradation rate of petroleum pollutants in the soil. Soil oil degradation was rapid in the condition of low oil concentration. But at higher oil-soil concentrations, the photo-degradation was significantly slower. Soil particle size had also an impact on the photo-degradation rate. Larger soil particles were in favor of photochemical reaction. Kinetics result illustrated that photochemical degradation of petroleum on oil surface follows pseudo-first-order kinetics in different experimental conditions.(3) Various kinds of catalyst were added into the soil, then analyzed the photo-degradation results. The experimental results showed that catalysts could significantly improve the degradation rate of oil pollutants in soil, the efficiency sequence was TiO2>Fe2O3.But after adding humic acid to the soil sample, the photo-degradation of soil surface oil pollutant decreased, while humic acid was usually considered a photo-sensitizer substance which could accelerate photochemical reactions. It was because that the adsorption of humic acid to oil restrains oil’s degradation, humic acid probably has strong absorption to the photon and decreases the photon absorption of oil. (4) The petroleum fractions of photo-degradation were investigated by various quantitative methods including UV specrophotometer, FT-IR, GC-MS, three-dimensional fluorescence specrophotometer. The result showed that aromatic substances were decomposed most easily, the cycloalkane next, then the straight chain hydrocarbons, and photo-degradation products were mainly ketones, carboxylic acids and esters.