Abstract Coastal lagoons and marshes are among the most fluctuating and productive ecosystems in the world, which provide a wide range of ecosystem. The objective of this work was to evaluate the factors and processes that condition the hydrogeochemical dynamics in salt marshes associated with the development of small coastal lagoons located at the southern end of the outer estuary of the Rio de la Plata, where it confluences with the Atlantic Ocean. Four samplings were carried out where major ions composition was determined in seawater, surface water of the lagoon and tidal channel, and in groundwater of the marsh, measuring in situ water pH and the electrical conductivity (EC). The chemical data were analyzed considering the conditions and processes associated with both water balance and tidal regime. The coastal lagoon develops within a sandy spit with dunes which is connected to the sea by a narrow tidal channel where the entry of the tidal flow is limited. The tide that enters has strong chemical variability, reflected in EC ranging from 19.1 to 37.5 mS/cm, depending on the dominant source (ocean or estuary). In periods with evapotranspiration domain, tidal water in the lagoon evaporates resulting in soluble salts precipitation such as gypsum and halite. The subsequent tidal flood dissolves these salts causing that in these periods both surface water of the lagoon and groundwater in the marsh present EC values between 8.4 and 57.1 mS/cm. Conversely, when evapotranspiration is low, surface water of the lagoon and tidal channel and groundwater of the marsh have EC between 3.5 and 18.1 mS/cm, and freshwater discharge from the dune sector where the rain preferentially infiltrate becomes relevant. The results obtained show the strong chemical variability that this type of coastal wetlands presents, providing the basis for its conservation and management of natural reserve areas.

中文翻译：

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与拉普拉塔河口外部界限相关的湿地和沿海泻湖的水化学动力学

摘要 沿海泻湖和沼泽是世界上变化最大、生产力最高的生态系统之一，提供了广泛的生态系统。这项工作的目的是评估影响盐沼中水文地球化学动力学的因素和过程，这些因素和过程与位于拉普拉塔河外河口南端的小型沿海泻湖的发展有关，在那里它与大西洋汇合。海洋。进行了四次采样，其中测定了海水、泻湖和潮汐通道的地表水以及沼泽地下水中的主要离子组成，测量了原位水的 pH 值和电导率 (EC)。考虑到与水平衡和潮汐状况相关的条件和过程，对化学数据进行了分析。沿海泻湖在沙丘内发育，沙丘通过狭窄的潮汐通道与大海相连，潮汐流的进入受到限制。进入的潮汐具有很强的化学变异性，反映在 EC 范围从 19.1 到 37.5 mS/cm，这取决于主要来源（海洋或河口）。在蒸发蒸腾区域，泻湖中的潮汐水蒸发，导致可溶性盐类沉淀，如石膏和岩盐。随后的潮汐洪水溶解了这些盐分，导致在这些时期，泻湖的地表水和沼泽中的地下水的 EC 值都在 8.4 到 57.1 mS/cm 之间。相反，当蒸散量较低时，泻湖和潮汐通道的地表水和沼泽地下水的 EC 在 3.5 至 18.1 mS/cm 之间，与雨水优先渗透的沙丘区的淡水排放有关。获得的结果表明，这种类型的沿海湿地呈现出强烈的化学变异性，为其自然保护区的保护和管理提供了基础。