p-Cresol mineralization and bacterial population dynamics in a nitrifying sequential batch reactor

The ability of a nitrifying sludge to oxidize p-cresol was evaluated in a sequential batch reactor （SBR）. p-Cresol was first transformed to p-hydroxybenzaldehyde and p-hydroxybenzoate, which were later mineralized. The specific rates of p-cresol consumption increased throughout the cycles. The bacterial population dynamics were monitored by using denaturing gradient gel electrophoresis 0DGGE） and sequencing of DGGE fragments. The ability of the sludge to consume p-cresol and intermediates might be related to the presence of species such as Variouorax paradoxus and Thauera mechernichensis, p-Cresol （25 to 200 mg C/L） did not affect the nitrifying SBR performance （ammonium consumption efficiency and nitrate production yield were close to 100% and 1, respectively）. This may be related to the high stability observed in the nitrifying communities. It was shown that a nitrifying SBR may be a good alternative to eliminate simultaneously ammonium and p-cresol, maintaining stable the respiratory process as the bacterial community.     

Is urban development an urban river killer? A case study of Yongding Diversion Channel in Beijing, China

The high population and concrete environment alter urban areas by changing temperature, rainfall runoff, and water resource utilization activities. This study was conducted to investigate the water quality features of the Yongding Diversion Channel in Beijing, China, and its relationship with rainfall and urban development. Monthly water quality data were obtained from April to October of 2004 at monitoring sites of Sanjiadian, Gaojing, Luodaozhuang, and Yuyuangtan. The monthly water quality grades from 2007 to 2011 were also investigated and compared with those of other rivers. Dissolved oxygen and pH showed greater decreases after one or two moderate rainfall events than several light rainfall events. The potassium permanganate index （CODMn）, ammonia nitrogen （NH3-N） and total phosphorus （TP） increased more after several light rainfall events than after one or two moderate or heavy rainfall events. Pollutant concentrations （CODMn, NH3-N, TP） in downstream regions showed greater changes than those in upstream areas after heavy rainfall events. Intense human activities around the channel greatly influenced the water quality of the channel in rainy season because of runoff pollution; however, heavy rainfall had a strong dilution effect on the pollutant concentrations in rivers. Overall, urban development has obviously deteriorated the water quality of the Yongding Diversion Channel as indicated by an increase in the water quality index from 3.22 in 2008 to 4.55 in 2010. The Pearson correlation between monthly rainfall and water quality indices from 2007 to 2011 ranged from 0.1286 to 0.6968, generally becoming weaker as rainfall and rainfall runoff became more random and extreme.     

基于P-S-R模型的焦作市生态安全评价

文章基于焦作市社会、经济及生态环境现状分析,借鉴压力-状态-响应(P-S-R)模型,运用层次分析法构建一个涵盖指标层、因素层、准则层及目标层等4层次的城市生态安全评价指标体系。在用熵权法确定各指标权重的基础上,结合时间趋势法评价焦作市2001～2007年的生态安全状况。结果表明:2001～2003年间生态安全综合指数值分别为0.277 7、0.384 5、0.505 3,表示生态安全水平较低;2004～2007年间生态安全综合指数值在0.573 5～0.683 1之间,生态安全有所提高。整体来看,近些年来,焦作市的生态安全水平呈现不断好转态势。该研究可为了解焦作市生态安全现状,及其未来生态环境质量改善和生态安全规划管理提供依据。