Cape Shores Porewater Data Compilation 2014-2015

Biogeochemical reactions within intertidal zones of coastal aquifers, induced by the mixing between fresh groundwater and saline seawater, have been shown to alter the concentrations of terrestrial solutes prior to their coastal discharge. In organic-poor sandy aquifers, the input of marine organic matter from infiltrating seawater has been attributed to active biogeochemical reactions within the sediments. However, while the seasonality of surface water organic carbon concentrations (primary production) and groundwater mixing patterns have been well-documented, there has been limited speculation on the contributions of particulate organic carbon pools within the sediments that arise from transient hydrologic conditions. To understand the relationship between physical movements of the circulation cell and the seasonal migration of geochemical patterns, beach porewater and sediment samples from six field sampling events spanning two years were analyzed. While oxygen saturation, oxygen consumption rates, and silica distributions closely followed the seasonally-dynamic salinity, other chemically-reactive parameters (pH, ORP) and nutrient characteristics (N distributions, denitrification rates, reactive organic carbon distributions) were unrelated to contemporaneous salinity patterns. Particulate organic matter was distributed in pools within the aquifer due to the filtration effect of sediments, contributing to the divergence of chemical patterns from salinity patterns via nutrient release and leaching. Together, the results present the asynchronous movement of chemical conditions to salinity patterns due to the divergent transport pathways between solutes and particles arising from transient hydrologic forcing.

海岸含水层潮间带内，由淡水地下水与咸海水混合引起的生物地球化学反应，已被证实能够在海岸排放前改变陆地溶质的浓度。在有机质匮乏的沙质含水层中，渗入的海水所携带的海洋有机质的输入，被归因于沉积物内活跃的生物地球化学反应。然而，尽管地表水有机碳浓度（初级生产）的季节性变化以及地下水混合模式已有详尽记录，但对于由瞬时水文条件产生的沉积物中颗粒有机碳库的贡献，却鲜有深入探讨。为了理解环流细胞物理运动与地球化学模式季节性迁移之间的关系，对六次野外采样事件中获取的海滩孔隙水和沉积物样本进行了分析。虽然氧饱和度、氧消耗速率和二氧化硅分布紧密跟随季节性动态的盐度，但其他化学活性参数（pH值、氧化还原电位）和营养特性（氮分布、反硝化速率、活性有机碳分布）与同时期的盐度模式无关。颗粒有机物质由于沉积物的过滤作用分布在含水层内的池中，通过营养释放和淋溶作用，导致化学模式与盐度模式发生偏离。综合来看，结果展示了化学条件与盐度模式之间的异步运动，这是由于由瞬时水文强迫产生的溶质与颗粒之间的运输路径存在差异所致。