Institute for Water Resources Science and Technology, Texas A&M University-San Antonio, One University Way, San Antonio, TX, 78224, USA.
Department of Mathematical, Physical and Engineering Sciences, Texas A&M University-San Antonio, One University Way, San Antonio, TX, 78224, USA.
Arch Environ Contam Toxicol. 2022 Apr;82(3):439-454. doi: 10.1007/s00244-022-00921-y. Epub 2022 Mar 26.
Urbanization and agriculture are two key factors that place demands on water resources and serve as sources of anthropogenic pollution into inland waterways. The San Antonio River, which is sourced from a karst aquifer, plays an important recreational and scenic role, yet effective management is often hampered by the lack of understanding of the chemical characterization of the water system. The karst-dominated Edwards Aquifer watershed in south-central Texas is an ideal watershed to understand water-rock interaction (carbonate dissolution) and anthropogenic impact on our water resources. In order to understand groundwater-surface water interactions, we made chemical and isotopic measurements over a 17-km stretch of the San Antonio River beginning at the headwater sanctuary and moving downstream. The chemistry of the headwaters and at along the longitudinal profile of the river showed that the Edwards Aquifer is dominated by Ca, Mg and HCO ions resulting from carbonate dissolution. The carbon isotopic signature of dissolved inorganic carbon (δC) showed that the Edwards Aquifer is in chemical and isotopic equilibrium with soil CO. The relationships between δC and solutes (Cl, Na, F, NO) showed that anthropogenic sources of these solutes are associated with low δC values, indicating that carbon isotopic composition of dissolved inorganic carbon can be a useful tracer for contaminants in the environment. The anthropogenic inputs into the San Antonio River were sourced mainly from effluents of the San Antonio Zoo, waste discharge from the River Walk in downtown San Antonio and from fertilizers and animal waste in the less urbanized section of the sampled area (Mission Concepcion to Mission Espada). To protect and sustain the water quality of urban waterways and karst aquifers, urban sewage and effluents must be treated and controlled.
城市化和农业是对水资源提出需求的两个关键因素，也是内陆水道人为污染的源头。圣安东尼奥河源自喀斯特含水层，具有重要的娱乐和景观作用，但由于缺乏对水系化学特征的了解，其有效管理常常受阻。德克萨斯州中南部以喀斯特为主的爱德华兹含水层流域是了解水-岩相互作用（碳酸盐溶解）和人为对水资源影响的理想流域。为了了解地下水-地表水相互作用，我们对圣安东尼奥河的 17 公里河段进行了化学和同位素测量，起点是源头保护区，一直延伸到下游。源头和河流纵剖面的化学分析表明，爱德华兹含水层主要由源自碳酸盐溶解的 Ca、Mg 和 HCO 离子组成。溶解无机碳的碳同位素特征（δC）表明，爱德华兹含水层与土壤 CO 处于化学和同位素平衡状态。δC 与溶质（Cl、Na、F、NO）之间的关系表明，这些溶质的人为来源与低δC 值有关，这表明溶解无机碳的碳同位素组成可以作为环境中污染物的有用示踪剂。圣安东尼奥河的人为输入主要来自圣安东尼奥动物园的废水、圣安东尼奥市中心河滨步道的废物排放以及采样区域城市化程度较低部分（使命 concepcion 到使命 espada）的肥料和动物废物。为了保护和维持城市水道和喀斯特含水层的水质，必须对城市污水和废水进行处理和控制。
