采集城市排污水渠中的沉积物样品和底栖生物样品,应用微电极原位pH测量技术测量沉积物-水界面溶液的pH值,电感耦合等离子体发射光谱法测定沉积物提取液中上覆水和空隙水中生物可利用磷的含量,研究了沉积物表面的生物膜对城市河流沉积物-水界面微环境中pH值和磷含量的影响.研究表明沉积物表面的生物膜由藻类(蓝藻门颤藻属Oscillatoria和硅藻门的菱形藻Nitzschia)和微生物组成,由于藻类的光合作用和微生物作用,沉积物空隙水中的溶解氧和CO2发生变化,因而改变了界面附近的pH值、氧化还原电位等物理化学条件,同时改变了界面附近溶液中磷的浓度和浓度梯度.在生物膜作用下,剖面中空隙水的pH和pH变化梯度、磷的浓度和浓度梯度高于非生物作用条件下.磷在生物藻垫的空隙水中高度富集.在生物膜存在情况下,在空隙水中形成了与非生物作用下相反的pH值和磷浓度的耦合关系.无生物作用的沉积物空隙水中pH越偏离中性,沉积物中磷的释放量增加,空隙水中磷含量增加;在生物膜作用下,pH由弱酸性向中性变化时,沉积物中磷的释放量增加,空隙水中磷含量增加.依据界面附近pH值和磷的变化规律,可以将沉积物-水界面附近的生物作用分为生物膜的固定作用区和攫取作用区.%The effect of biofilms on pH and phosphorous in the water-sediment interface were studied for sediments and benthic biological samples from the city sewerage system. The pH values were measured in situ on the interface by the pH microprofile method with an Ir/IrO2 microelectrode. The biological utilized P content from upper and middle extracting solutions of sediments was determined by Inductively Coupled Plasma-Atomic Emission Spectrometry ( ICP-AES ). In the experiment, the biofilms primarily consisted of genera Oscillatoria Nitzschia and bacteria Biofilms,which caused an increase of the pH and concentration of phosphorous and the variation of pH and phosphorous concentration in the water across the sediment-water interface. Phosphorous was concentrated in the pore water of the biofilm. Compared to the conditions without biofilms, biofilms provided an opposite coupling relation between the pH and phosphorous concentration in pore water. Without the biofilms, the release of phosphorous from sediments and phosphorous content in the pore water increased with the pH changing from neutral to acidic. Conversely, the biofilm process enhanced the release of phosphorous from sediments and phosphorous content in the pore water with the pH changing from acidic to neutral. Based on the relationship between the pH and phosphorous concentrations, the role of biofilms can be divided into two distinct areas: biological fixation area and biological scavenging area in surface sediments.
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