Effect On Biodegradation And Solubilization Of Ploycyclic Aromatic Hydrocarbon In Sediments With Non-ionic Surfactant

PAHs(Polycyclic Aromatic Hydrocarbons), as a class of typical and stable organicpollutants(POPs) which may cause eratogenic, carcinogenic and mutagenic effects, arewidely distributed in the environment. PAHs are harmful for human health andenvironment, because they are easy to migrate to the soil and sediments since their lowwater solubility and high lipid solubility, and lipid accumulate in the organism throughthe food chain. Micro-biological degradation is, as one of the removal pathways toPAHs, has many advantages expect sustainable, environmentally friendly andeconomical practicality. PAHs,as the sole carbon source for microorganisms, isdegradedby co-metabolism. And this process is influenced by the bioavailability, temperature, pH,oxygen conditions, nutrition and other environmental factors.The bioavailability ofPAHs means the ability of microorganisms to the accessibility of PAHs, we usually useadding a surfactant to improve the solubility of PAHs and other ways to promote thebioavailability of PAHs.This paper focused on three surface sediments in the Yangtze River and JialingRiver of Chongqing section. Tween80and Triton X-100(2common Non-ionicsurfactants) were used to study adsorption of sediments. And phenanthrene(Phe) andfluoranthene(Fluo) were used as the model substance of PAHs to study learnsolubilization of surfactants of PAHs in sediments. We also discussed the effect ofTween80on the process of biodegradation of PAHs in sediments through theexperiment how Tween80affects proliferation of bacteria(Flavobacterium) which coulddegrade PAHs in sediments.The main conclusions are as follows：①how Tween80and Triton X-100affect adsorption behavior of sedimentsMake a figure that showing tension changes of three sediment samples withdifferent concentrations of Tween80and Triton X-100in different sediment/waterratio to get CMCeff（Effective critical micelle concentration）of Tween80and TritonX-100and their maximum adsorption amount in each sediment when the liquidconcentration of surfactant belows CMC(Critical micelle concentration). The resultsshow adsorption characteristics of Tween80and Triton X-100in3samples can be fittedwell with Freundlich isotherm model, the maximum adsorption capacity of eachsurfactant in each sample are basically equaled and Tween80’s are bigger than Triton X-100’s.②Solubilization of Tween80and Triton X-100on Phe and FluoAccording to the experiment, Tween80and Triton X-100can help Phe and Fluo todissolve in liquid phase and sediment/water system. The solubilization curve obtainedfrom sediment/water system should be divided into2stages, and the surfactantconcentration values are close to the CMCeffvalue at cut-off point in each stage. Whenthe concentration of Tween80and Triton X100below the critical point, they will inhibitPhe and Fluo to disslove; on the contrary, Phe and Fluo should dissolve.③Biodegradable characteristics of Phe and Fluo under the condition of differentconcentration of surfactantsComparing the growth and proliferation of degrading bacteria in differentsurfactants, we selected Tween80which affects proliferation of Flavobacteriumobviously to do a further study. We discussed biodegradable characteristics of Phe andFluo under the condition of different concentration of Tween80. The results show thatwith concentration range from450mg/L to1800mg/L, Tween80promotesbiodegradation of Phe and Fluo in sediments. However，at concentration of4500mg/L,Tween80reduces biodegradable rate of Phe and Fluo, which is due to the highconcentration of Tween80be a toxic for degrading bacteria and inhibits thebiodegradable rate through reducing the biomass.As a way to improve bioavailability of PAHs in sediments, solubilization ofsurfactants has been extensively studied abroad. Adsorption of sediments make loss ofsurfactants, this will directly affect the the expected amount of surfactants inbiodegradable and later process. Until now, the research on the relationship betweenadsorption of sediments, solubilization of surfactants and biodegradable process isrelatively scattered as well as its obiviously regional characteristic. The research work,funded by the National Natural Science Foundation, provide datas and support onbiological remediation of PAHs contaminated sediments.