Petroleum Pollution Characteristics Of Water-Sediments System In Source Water Reservoir And Bioremediation Research Of Oil Contaminated Soil In Northwest Loess Area

Petroleum pollution is widespread, complex, and disdegradational. Special climate and soilcharacteristics result in the differences of petroleum pollution style to environment andpetroleum pollution treatment means in Northwest Loess Area. The study was under thebackground of petroleum pollution in Northwest Loess Area. By simulating the static releaseof the petroleum pollutants in sediments, which meaned that petroleum transferred fromsediments to superior water body, the transference rule of petroleum in water body andsediments and static dynamic models was obtained under the different season. Thedistribution characteristics of petroleum pollutants in sediments and yearly oil contaminatedstates of branch catchment basin and main waterway were studied at Wangyao reservoir,which was the main water supply source of Yan’an. And the bioremendiation technology ofoil contaminated soil was systematically studied. The main research contents and results wereas follows:（1） The static release process of petroleum pollutants in sediments was described bystagnant film model. The release dynamic equation was as follows:K_rand C_W*, which were obtained by static experiments, were release rate constant ofpetroleum pollutants and petroleum concentration in aqueous phase under release balancerespectively. Temperature was a main factor which influenced the release rate of petroleumpollutants in sediments. When the oil contaminated concentration were between320mg/kg and4792mg/kg, the summer dynamic parameters equations were as fllows:K_r=5.51ln (C_S0)-0.25C_W*=0.0003C_S0+6.86The winter dynamic parameters equations were as fllows:K_r=3.28ln (C_S0)+12.20C_W*=0.0005C_S0+4.68According to these equations the summer and winter dynamic models were establishedrespectively. And the feasibility of models was verified.（2） The results of the static release experiments in the summer, when the temperature wasabout30℃and the oil contaminated concentration was between320mg/kg and810mg/kgrespectively in sediments, showed that the sediments effective depth, in which thepetroleum pollutants affected the water quality of superior water body, was about10cm bythree layer analysises of sediments after release balance, and showed that the secondpollution of sediments lasted for about60days, when oil contaminated concentration wasbelow1000mg/kg in sediments.（3） The results of petroleum component analysis in sediments showed that there were23kinds compounds. Besides of octacosane, cholesterin and squalane, the rest20kinds couldenter the superior water body. The substances whose carbon number was below12easilyentered the water body, and the substances whose carbon number was over17difficultlyentered the water body. The substances whose carbon number was between12and17weremain components of petroleum pollutants in water body. Among the7kinds polycyclicaromatic hydrocarbon, besides of dibenzo [a, h] anthracene, the rest6kinds, which hadgreat dangers to environment and human health, could enter water body.（4） The Wangyao reservoir, the main water supply source of Yan’an, was studied. All ofthe results were gained by400samples at40positions on10cross-sections. The petroleumconcentration of surface layer sediments was about203mg/kg at ante-dam in Wangyaoreservoir. There were5branches. The branch two whose water quality was the best andwater quantity was most great, improved the main waterway pollution. The rest branchcatchment basins were severely polluted. The branch one and five, whose water quantitywere little and pollution station had more and more serious tendency, had the little influenceon the main waterway water quality. But the branch three and four, whose water quality was worst and water quantity was greater, had the serious influence on the main waterway waterquality. There were three kinds diolefine and9kinds polycyclic aromatic hydrocarbon insurface sediments, which meaned that the Wangyao reservoir might be polluted by thepolycyclic aromatic hydrocarbon, at the entrance position of the branch three and four.（5） In laboratory the5highly efficient petroleum-degrading strains were screened underaerobic condition from oil contaminated soil obtained from the abandoned well site at Ansaioilfield in Yan’an. The5strains were GX1（Pseudomonas sp.）、GX2（Plesionmonas sp.）、GX3（Xanthomonas sp.）、GX4（Pseudomonas sp.）and GX5（Zoogloea sp.）., The highdegradation rates of the5strains were obtained, when the pH value was about7, the N/Pratio was about4and the petroleum concentration was below1000mg/L. The optimalnitrogen source was NH₄NO₃. But the eligible ranges of the initial pH value, N/P ratio andthe petroleum concentration were different.（6） The results in the field experimentation that lasted for80days in Northwest LoessArea showed that the petroleum concentration had great influence on the activity ofmicroorganism. The higher oil removal efficency rate was obtained at the lower petroleumconcentration, but the growth of microorganism was limited because of the absence ofcarbon source. At the higher petroleum concentration, the decreasing extent to the pH valuein the soil was too large and the growth of microorganism in the soil was inhibited bytoxicum.（7） In the field experimentation, adding nutrient was good to the growth ofmicroorganism and the oil removal efficency rate. By seeding highly efficientpetroleum-degrading strains, the higher oil removal efficency rate was obtained in the shortterm. The growth of microorganism was inhibited and the oil degradation rate decreasedbecause the simple plowing induced decreasing of water content in the soil.