Xia X H, Yu H, Yang Z F, Huang G H
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Chemosphere. 2006 Oct;65(3):457-66. doi: 10.1016/j.chemosphere.2006.01.075. Epub 2006 Mar 15.
The contamination of polycyclic aromatic hydrocarbons (PAHs) has become one of the major problems in the Yellow River of China. As the Yellow River is the most turbid large river in the world, it remains unknown to which extent the high suspended sediment content in the river may affect the fate and effect of PAHs. Here we report the effect of sediment on biodegradation of chrysene, benzo(a)pyrene and benzo(g,h,i)perylene with phenanthrene as a co-metabolism substrate in natural waters from the Yellow River. Biodegradation kinetics of the PAHs in the river water with various levels of sediment contents were studied in the laboratory by fitting with a biodegradation kinetics model for organic compounds not supporting growth. The results indicated that the biodegradation rates of PAHs increased with the sediment content in the water. When the sediment contents were 0, 4 and 10 g/l, the biodegradation rate constants of chrysene with the initial concentration of 3.80 microg/l were 0.053, 0.084 and 0.111 d(-1), respectively. Further studies suggested the enhanced biodegradation rate in the presence of sediment was caused by the following mechanisms: (1) the population of PAH-degrading bacteria in the water system was found to increase with the sediment content; the bacteria population on sediment phase was far greater than that on water phase during the cultivation process; (2) the sorption of PAHs on the sediment phase was well described by the dual adsorption-partition model. Although the sorption capacity of PAH per unit weight of sediment decreased with the increase of the sediment content, the amount of sorbed PAH increased with the sediment content; and, (3) the desorption of PAHs from the solid phase led to a higher concentration near the water-sediment interface. Since the bacteria were also attached to the interface, this resulted in an increased contact chance between the bacteria and PAHs.
多环芳烃（PAHs）污染已成为中国黄河面临的主要问题之一。由于黄河是世界上含沙量最大的大河，目前尚不清楚河流中高悬浮泥沙含量会在多大程度上影响PAHs的归宿和效应。在此，我们报告了黄河天然水体中，以菲作为共代谢底物时，沉积物对芘、苯并(a)芘和苯并(g,h,i)苝生物降解的影响。通过采用不支持生长的有机化合物生物降解动力学模型进行拟合，在实验室研究了不同泥沙含量的河水中PAHs的生物降解动力学。结果表明，PAHs的生物降解速率随水体中泥沙含量的增加而提高。当泥沙含量分别为0、4和10 g/L时，初始浓度为3.80 μg/L的芘的生物降解速率常数分别为0.053、0.084和0.111 d⁻¹。进一步研究表明，沉积物存在时生物降解速率提高的原因如下：（1）发现水系统中PAH降解菌的数量随泥沙含量增加而增加；培养过程中，沉积物相上的细菌数量远多于水相上的细菌数量；（2）PAHs在沉积物相上的吸附可用双吸附-分配模型很好地描述。虽然单位重量沉积物对PAH的吸附容量随泥沙含量增加而降低，但吸附的PAH量随泥沙含量增加而增加；（3）PAHs从固相的解吸导致水-沉积物界面附近浓度升高。由于细菌也附着在界面上，这导致细菌与PAHs之间的接触机会增加。
