Effects of Urbanization on Sources and Transport of Dissolved Inorganic Carbon in Watersheds

人类活动增加了溪流和河流中的溶解无机碳（DIC），这影响了美国大部分地区的饮用水供应。DIC向地表沃茨的运输增加使饮用水处理复杂化，促进藻类生长，增加水硬度，并腐蚀供水基础设施，如水管和管道。DIC还在河流和沿海海洋中提供缓冲能力（它可以作为“抗酸剂”）。农业和城市地区有可能增加DIC的来源和运输，因为农业石灰，混凝土结构的破坏和污水泄漏。 然而，以前的研究并没有集中在城市地区。 该项目将调查农业和城市土地利用如何影响溪流中DIC的来源、数量和运输，以及这些来源如何随着风暴和不同土地利用而变化。它将比较运输到河流中的DIC的数量和来源与森林参考条件。 这项研究将首先对DIC来源（混凝土、土壤、废水、岩石等）进行“指纹”。使用最先进的地球化学示踪剂 然后，它将估计城市河流在DIC被输送到敏感的接收沃茨（如切萨皮克湾）之前保留DIC的能力。 该项目将是第一个提供同步信息的DIC的来源和运输有助于增加河流碱化在美国的结果和成果将是重要的预测增加土地开发对饮用水质量的影响，估计沿海海洋酸化的影响，通知城市流域管理，恢复城市溪流。 溶解无机碳（DIC）的浓度增加，在美国东部的溪流和河流DIC从流域到溪流的运输有助于河流碱化，影响饮用水硬度，改变沿海碳循环，并增加初级生产的碳酸氢盐的可用性。 一些研究表明，DIC和碳酸盐碱度的运输显着升高的溪流和河流排水城市化流域。 DIC的命运和运输的大部分工作集中在森林和农业流域，所以我们知道的DIC在城市化流域的来源和运输的变化很少。 本研究探讨3个问题：1）土地利用如何影响DIC出口的数量和水文时间; 2）DIC的来源如何随着城市化的增加和整个风暴的变化; 3）城市化如何改变流域DIC出口的流中命运和运输？ 该研究将：a）每周分析巴尔的摩长期生态研究（LTER）站点的森林、农业、郊区和城市流域中DIC和其他风化产物的浓度和通量;和B）估计累积DIC分布曲线和DIC输出时间在土地利用梯度上的变化。 然后，研究将：a）在岩性相似的流域中，通过地球化学方法确定溪流DIC源的潜在端元（两个森林和两个郊区）使用DIC三角洲13 C、主要元素地球化学和DIC形态; B）评估在这些相同流域中风暴演变期间DIC浓度和潜在来源的变化;和c）在选定的流段中使用13 C-标记的NaHCO 3的流注射测量DIC吸收速率和瞬时储存。 预期成果将把流域城市化与DIC动态变化联系起来，DIC动态变化是土地利用、径流和渠道化的函数，并将阐明河流碱化增加的机制。 这将是第一个项目，生产的来源，运输，并使用综合水文和地球化学方法在城市河流DIC的命运同步信息之一。

Human activities have increased dissolved inorganic carbon (DIC) in streams and rivers, which impacts drinking water supplies across large regions of the U.S. Increased transport of DIC to surface waters complicates drinking water treatment, encourages algal growth, increases water hardness, and corrodes of water infrastructure, such as water mains and pipes. DIC also provides buffering capacity (it can act as an "antacid") in rivers and the coastal ocean. Agricultural and urban areas have the potential to increase DIC sources and transport because of agricultural liming, breakdown of concrete structures, and sewage leaks. However, previous research has not focused on urban areas. This project will investigate how agricultural and urban land uses impact sources, amounts, and transport of DIC in streams and how the sources change with storms and different land uses. It will compare the amount and sources of DIC transported to streams with forest reference conditions. The research will first "fingerprint" DIC sources (concrete, soils, wastewater, rocks, etc.) using state-of-the-art geochemical tracers. Then, it will estimate the ability of urban streams to retain DIC before it is transported to sensitive receiving waters, like Chesapeake Bay. This project will be one of the first to provide simultaneous information on sources and transport of DIC contributing to increased river alkalinization in the U.S. Results and outcomes will be important for predicting impacts of increasing land development on drinking water quality, estimating the effects on acidification of coastal oceans, informing urban watershed management, and restoring urban streams. Concentrations of dissolved inorganic carbon (DIC) have increased in streams and rivers in the eastern U.S. The transport of DIC from watersheds to streams contributes to river alkalinization, which impacts on drinking water hardness, shifts the coastal carbon cycle, and increases bicarbonate availability for primary production. Some studies suggest that transport of DIC and carbonate alkalinity are significantly elevated in streams and rivers draining urbanized watersheds. Most work on DIC fate and transport has focused on forest and agricultural watersheds; so we know little about changes in sources and transport of DIC in urbanized watersheds. This research investigates 3 questions: 1) How does land use influence the amounts and hydrologic timing of DIC exports; 2) How do sources of DIC change with increasing urbanization and throughout storms; and 3) How does urbanization alter in-stream fate and transport of watershed DIC export? The research will: a) analyze concentrations and fluxes of DIC and other weathering products weekly in forest, agricultural, suburban, and urban watersheds at the Baltimore Long-Term Ecological Research (LTER) site; and b) estimate cumulative DIC distribution curves and changes in DIC export timings across the land-use gradient. Then, the research will: a) geochemically identify potential end members of stream DIC sources in watersheds of similar lithology (two forested and two suburban) using DIC delta 13C, major element geochemistry, and DIC speciation; b) evaluate shifts in DIC concentrations and potential sources during the evolution of storms in these same watersheds; and c) measure DIC uptake rates and transient storage using stream injections of 13C-labelled NaHCO3 in selected stream reaches. Expected outcomes will link watershed urbanization to changes in DIC dynamics as a function of land use, streamflow, and channelization and will elucidate mechanisms for increased river alkalinization. This will be one of the first projects to produce simultaneous information on the sources, transport, and fate of DIC in urban streams using integrated hydrologic and geochemical approaches.