Department of Marine Sciences, Texas A&M University at Galveston, Galveston, TX 77553, USA.
Department of Marine Sciences, Texas A&M University at Galveston, Galveston, TX 77553, USA.
Sci Total Environ. 2014 Jul 1;485-486:252-262. doi: 10.1016/j.scitotenv.2014.03.066. Epub 2014 Apr 12.
Urbanization and stream-channel modifications affect organic matter concentrations and quality in streams, by altering allochthonous organic matter input and in-stream transformation. This study uses multiple tracers (δ(13)C, δ(15)N, C/N ratio, and chlorophyll-a) to track sources of organic matter in two highly urbanized bayous in Houston (Texas, USA). Wastewater treatment plants (WWTPs) are located in headwaters of both bayous and contribute more than 75% to water flow. Low isotopic relatedness to natural end-members and enriched δ(15)N values suggest the influence of WWTPs on the composition of all organic matter fractions. The two bayous differ in degree of channel improvement resulting in different responses to hydrological conditions. During high flow conditions, the influence of terrestrial organic matter and sediment resuspension was much more pronounced in the Buffalo Bayou than in the concrete-lined White Oak Bayou. Particulate organic matter (POM) in White Oak Bayou had similar values of enriched δ(15)N in all subsegments, whereas in Buffalo Bayou, the degree of δ(15)N enrichment was less in the subsegments of the lower watershed. The difference in riparian zone contributions and interactions with sediments/soils was likely responsible for the compositional differences between the two bayous. Phytoplankton inputs were significantly higher in the bayous, especially in slow-flowing sections, relative to the reference sites, and elevated phytoplankton inputs accounted for the observed stable C isotope differences between FPOM and high molecular weight dissolved organic matter (HMW DOM). Relative to POM, HMW DOM in the bayous was similar to WWTP effluents and showed minor longitudinal variability in both streams suggesting that WWTPs contribute much of the DOM in the systems. Urbanization has a major influence on organic matter sources and quality in these urban water bodies and these changes seem further enhanced by stream channel modifications.
城市化和河道改造通过改变外源有机物质输入和河流内转化，影响河流中有机物质的浓度和质量。本研究使用多种示踪剂（δ(13)C、δ(15)N、C/N 比和叶绿素-a）来追踪休斯顿（美国德克萨斯州）两个高度城市化的河口有机物的来源。污水处理厂（WWTP）位于两条河流的源头，对水流的贡献超过 75%。与天然端元的同位素相关性低和 δ(15)N 值富集表明 WWTP 对所有有机物质组分组成的影响。这两条河流在河道改善程度上存在差异，导致对水文条件的响应不同。在高流量条件下，陆地有机物质和沉积物再悬浮的影响在布法罗河比在混凝土衬砌的白橡树河更为明显。白橡树河的颗粒有机物质（POM）在所有亚段中具有相似的 δ(15)N 富集值，而在布法罗河，下流域亚段的 δ(15)N 富集程度较低。河岸带贡献的差异以及与沉积物/土壤的相互作用可能是两条河流之间组成差异的原因。浮游植物的输入在两条河流中都明显高于参考点，尤其是在流速较慢的河段，这也解释了 FPOM 和高分子量溶解有机物质（HMW DOM）之间观察到的稳定 C 同位素差异。与 POM 相比，河流中的 HMW DOM 与 WWTP 废水相似，在两条河流中均表现出较小的纵向变化，这表明 WWTP 对系统中的大部分 DOM 有贡献。城市化对这些城市水体中的有机物来源和质量有重大影响，这些变化似乎因河道改造而进一步增强。
