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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Abiotic and biotic controls of organic matter cycling in a managed stream
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Abiotic and biotic controls of organic matter cycling in a managed stream

机译：受控流中有机物循环的非生物和生物控制

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Urbanization often alters the physical, chemical, and biological structure of aquatic ecosystems embedded within them, creating managed ecosystems with different structure and functioning as compared to their unmanaged counterparts. Our work focused on patterns in dissolved organic carbon (DOC) along a managed stream in Phoenix, Arizona. We documented longitudinal changes in DOC concentrations and quality (defined as chemical complexity and measured as specific ultraviolet absorbance at 254 nm, SUVA) along a 66 km stream dominated by treated wastewater effluent. DOC concentrations along the stream declined by an average of 64%, and chemical complexity increased substantially. We posed four hypotheses to explain changes in downstream water chemistry; including hydrologic dilution, microbial mineralization, abiotic sorption to suspended sediments, and photodegradation by ultraviolet (UV) radiation. Only the second and fourth hypotheses represent permanent removal mechanisms. Our data most strongly supported predictions from the dilution hypothesis and microbial mineralization as an explanation for the changes in DOC chemistry. Surface-subsurface water linkages were important but altered from unmanaged streams, as deep groundwater was used to augment surface flows. Variation in the use of groundwater was linked to human decision making and engineering related to water management. Reduction in geomorphic complexity increased the importance of dilution in explaining patterns but also increased the importance of UV oxidation as a mechanism influencing DOC chemistry. Our findings suggest urban stream management has shifted dependence on microbially mediated C removal mechanisms to hydrologic dilution to reduce output concentrations. This shift lowers contaminant removal potential and increases dependence on limited groundwater resources.
机译：城镇化通常会改变其中所嵌入的水生生态系统的物理，化学和生物结构，从而形成与非管理生态系统相比具有不同结构和功能的管理生态系统。我们的工作重点是在亚利桑那州凤凰城沿一条受控流中溶解有机碳（DOC）的模式。我们记录了沿处理过的废水为主的66公里水流中DOC浓度和质量的纵向变化（定义为化学复杂性，并在254 nm下测量为特定紫外线吸收，SUVA）。沿流的DOC浓度平均下降了64％，化学复杂性大大提高。我们提出了四个假设来解释下游水化学的变化。包括水文稀释，微生物矿化，悬浮物的非生物吸附以及紫外线（UV）的光降解。只有第二个和第四个假设代表永久删除机制。我们的数据最有力地支持了稀释假说和微生物矿化的预测，以此来解释DOC化学的变化。地表-地下水联系很重要，但由于未经控制的溪流已被深水用来增加地表流量，因此已被改变。地下水使用的变化与与水管理有关的人类决策和工程有关。降低地貌复杂性增加了稀释解释模式的重要性，但也增加了紫外线氧化作为影响DOC化学的机制的重要性。我们的发现表明，城市河流管理已将对微生物介导的C去除机制的依赖转移到水文稀释以降低输出浓度。这种转变降低了污染物去除的可能性，并增加了对有限地下水资源的依赖。

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