Distribution Of PAHs In Sewage Sludge From Jiangsu Province And Influence Of Sludge Compost On Fluoranthene Environmental Behavior

With the development of wastewater treatment,the total amount of municipal sludges, byproduct during wastewater treatment in municipal wastewater treatment plants,increase greatly.Among the disposal methods of sludges,land application after composting is the most suitable way according to the situation of our country.But sludges after their land application will influence the environmental behaviors of soil elements such as metals and organic contaminants.Polycyclic Aromatic Hydrocarbons(PAHs) are compounds polymerized by more than two rings(including two) with linear,homed,or fascicled arrangement.They are widely distributed in the environment,hard to be degraded.Most of them are mutagens and carcinogens,and can induce malformation of embryo.Therefore, special attention has been focused on the environmental chemical behaviors of PAHs. Studies on soil-sludge composting-organic contaminants will contribute to the reasonable utilization of sludges.In our studies,sludges composting was used as object, fluoranthene(FLT) was on behalf of PAHs,and methods included dynamic sampling,room analysis,sludges' composting,leaching of soil column,and room culture were employed. The main contents include:the concentration and the distribution of PAHs in municipal sludges in Jiangsu Province,effects of composting on the concentration of PAHs in municipal sludges,the physicochemical properties of water dissolved organic matters (DOM) in sludges before and after composting,effects of sludges composting and DOM on the desorption-leaching and eco-toxicity of FLT in polluted soil,and primary investigation of mechanism on same phenomena.Results from HPLC analysis showed that PAHs were widely distributed in municipal sludges in Jiangsu Province.Total amount of PAHs(∑PAHs,16 PAHs in the priority contaminants of US EPA) was 11.68-169.91mg/kg,and there was significant difference in∑PAHs among slidges.The total concentration ranges of carcinogenic PAHs was 1.17 to 41.03mg/kg,and the average was 6.59mg/kg.Total amount of PAHs in the priority contaminants of EPA P.R.China was 4.07-59.06mg/kg.The distribution pattern of PAHs in sludges was nonnormal.Compounds contained two(or three) benzene ring was dominant among the 7-16 PAHs found in the sludges,and the percentage of compounds contained four to six benzene ring was low.Naphthalin was the main PAHs' compounds in municipal sludges in Jiangsu Province.The contents of BaP,a strong carcinogenic PAH,was relative low,and its total concentration was 0-2.198 mg/kg,with the average of 0.152mg/kg,which was much less than 3.0 mg/kg(the control standard of sludge land application).Factors such as wastewater source,treatment technicology,and sludge treatment had great effects on PAHs contents in sludges.The digestion and composting could obviously reduce PAHs contents,and change the distribution pattern of PAHs in sludges.With the sludges composting,content of DOM decreased.But components with molecule weight over 8000Da and hydrophobic components increased.The ratio of hydrophobic components to hydrophilic components increased from 0.87 to 1.34.Infrared spectrum,ultraviolet spectrum and E₄/E₆ showed that with the sludges composting,the polymerization and aromatization of DOM increased.Results of sequential batch experiments and leaching of soil column showed that the application of sludges to polluted soil would promote the desorption and leaching of FLT beecause DOM produced after the application of composting sludges in a short time.But the effect would be more obvious for the primordial composting with more organic matters. Through the experiments of DOM extraction before and after composting,we found DOM from the carrion composting was more active in the enhancing of the desorption and leaching of FLT than the primordial composting,which may cause by more hydrophobic components and high-molecule-weight components in the carrion composting.Results of pot experiments showed that there was obvious inhibiting effect of FLT on the growth of plants,and the application of composting sludges and DOM from sludges composting could mitigate this inhibiting effect.FLT in soil would be easier to be accumulated in the roots of maize.The effects of composting sludges and DOM on the accumulation of FLT in the shoots and the roots of maize showed the growth difference. With the time going on,FLT in soil decreased,and both plants and spiked organic matters could accelerate the reduction of FLT in soil.In the water culture experiments,we found that FLT could inhibit the growth of maize. Roots of maize could absorb and accumulate more FLT than shoots from solution.DOM from sludges composting could enhance absorption and accumulation of FLT and the transfer of FLT from roots to shoots.