title: Effect of organic wastes on the plant-microbe remediation for removal of aged PAHs in soils.
abstract: The effectiveness of in-situ bioremediation of polycyclic aromatic hydrocarbons (PAHs) may be inhibited by low nutrients and organic carbon. To evaluate the effect of organic wastes on the PAHs removal efficiency of a plant-microbe remediation system, contaminated agricultural soils were amended with different dosages of sewage sludge (SS) and cattle manure (CM) in the presence of alfalfa (Medicago sativa L.) and PAHs-degraders (Bacillus sp. and Flavobacterium sp.). The results indicated that the alfalfa mean biomasses varied from 0.56 to 2.23 g/pot in root dry weight and from 1.80 to 4.88 g/pot in shoot dry weight. Low dose amendments, with rates of SS at 0.1% and CM at 1%, had prominent effects on plant growth and soil PAHs degradation. After 60-day incubation, compared with about 5.6% in the control, 25.8% PAHs removal was observed for treatments in the presence of alfalfa and PAHs-degraders; furthermore, when amended with different dosages of SS and CM, the removed PAHs from soils increased by 35.5%-44.9% and 25.5%-42.3%, respectively. In particular, the degradation of high-molecular-weight PAHs was up to 42.4%. Dehydrogenase activities (DH) ranged between 0.41 and 1.83 microg triphenylformazan/(g dry soil x hr) and the numbers of PAHs-degrading microbes (PDM) ranged from 1.14 x 10(6) to 16.6 x 10(6) most-probable-number/g dry soil. Further investigation of the underlying microbial mechanism revealed that both DH and PDM were stimulated by the addition of organic wastes and significantly correlated with the removal ratio of PAHs. In conclusion, the effect of organic waste application on soil PAHs removal to a great extent is dependent on the interactional effect of nutrients and dissolved organic matter in organic waste and soil microorganisms.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. zhangj79@issas.ac.cn
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Xiangui
authors.initials: X
authors.lastname: Lin
authors.forename: Weiwei
authors.initials: W
authors.lastname: Liu
authors.forename: Yiming
authors.initials: Y
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Zeng
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D018533:Biomass; D002417:Cattle; D008372:Manure; D010088:Oxidoreductases / Q000378:metabolism; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism*; D012722:Sewage; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D008372:Manure; D011084:Polycyclic Aromatic Hydrocarbons; D012722:Sewage; D012989:Soil Pollutants; D010088:Oxidoreductases