Groundwater contribution to the nutrient budget of Tomales Bay, California
Groundwater contribution to the nutrient budget of Tomales Bay, California
复制标题
地下水对加利福尼亚州托马莱斯湾养分预算的贡献
DOI：
10.1007/bf00003144
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发表时间：
1990
期刊：
影响因子：
4
通讯作者：
Stephen V. Smith
中科院分区：
文献类型：
--
作者：
J. Oberdorfer;M. Valentino;Stephen V. Smith
Tomales Bay是一个沿圣安德烈亚斯断层的地堑结构，由于其线性、一维的形态和相对原始的状态，被选择用于模拟生态系统营养动力学。地下水在养分收支中是一个潜在的重要术语。然而，圣安利亚斯断层造成的地质复杂性使水文地质复杂化，并要求将该地区细分为三个区域：西部的花岗岩，东部的弗朗西斯组和冲积物填海槽。地下水中的营养物质浓度是通过广泛的井取样来确定的；地下水流量是用达西定律计算和土壤水分预算来估计的。结果表明：地下水流量与夏季流入海湾的河流流量在同一数量级，而冬季则明显小于其他淡水输入。地下水中的溶解营养物（磷酸盐、硝酸盐+亚硝酸盐、铵、二氧化硅和DIC）浓度始终高于地表水排放（高达一个数量级）。在夏季的几个月里，地下水对海湾的营养负荷贡献与河流一样多。在冬季，地下水对养分负荷的贡献约为径流贡献的20%。我们的研究结果表明，地下水是陆地养分和淡水负荷的重要组成部分，特别是在夏季。然而，与海湾口的混合通量或空气-水界面的N2气体通量相比，地下水和河流的养分通量都不大。
Tomales Bay, a graben structure along the San Andreas Fault, was selected for modeling ecosystem nutrient dynamics because of its linear, one-dimensional morphology and relatively pristine state. Groundwater is a potentially important term in the nutrient budget. The geologic complexities created by the San Anreas Fault, however, complicate the hydrogeology and require the area to be subdivided into three regions: granite to the west, Franciscan Formation to the east, and alluvial fill in the trough. Nutrient concentrations in the groundwater were determined through extensive well sampling; groundwater discharge was estimated using both Darcy's Law calculations and a soil moisture budget. Results indicate that groundwater discharge is of the same order of magnitude as summer streamflow into the Bay, while being significantly less than other freshwater inputs in winter. Dissolved nutrient (phosphate, nitrate + nitrite, ammonium, silica and DIC) concentrations in groundwater were consistently higher (by as much as an order of magnitude) than in surface water discharges. During the summer months, groundwater flow contributes about as much nutrient load to the bay as does streamflow. During the winter, the groundwater contribution to nutrient loading is about 20% of the streamflow contribution. Our findings indicate that groundwater is a significant component of terrestrial nutrient and freshwater loading to Tomales Bay, particularly so during the summer months. However, neither groundwater nor streamflow nutrient fluxes are large in comparison to the mixing flux at the bay mouth or the flux of N2 gas across the air-water interface.