Formation and Characteristics of Brine-rich Water in the Dry Valleys, Antarctica

本研究旨在更好地了解寒冷沙漠中的盐分积累，并建立地下水盐分运移模型。寒冷的沙漠，如南极的麦克默多干谷（MDV），与炎热的沙漠相似，因为没有足够的水将盐从土壤中冲洗到海洋中，所以它们积累了高浓度的盐。 盐的积累允许创造富含盐水的地下水，在低得多的温度下冻结。实地工作将集中在MDV的几个地下水特征上，包括唐璜池塘，这是一个浅水湖，积累了极高的盐分，直到温度达到-51摄氏度（-60华氏度）才结冰。 该设置提供了更好地了解这一独特的水环境，包括生命在其极端的潜力。它也是火星的模拟环境，火星是一个完全由永久冻土覆盖的星球，类似于MDV。该项目将支助华盛顿大学地球和空间科学系的一名博士生，对他进行化学分析、化学和物理建模以及极地沙漠环境远距离实地工作方面的培训。然而，在南极环境中控制离子再分布的过程受到的约束很小。该项目旨在更好地了解普遍富含氯化钙的富盐水地下水的形成，盐的再分布和水活性。 一个主要目标是开发一个盐水热;反应; MDV区域的传输模型，使用从现场收集的数据来约束模型输入和地面实况模型输出。该模型将开发一个Pitzer型热力学、反应传输模型，并将其与地面温度模型耦合。 该模型将测试MDV中地下水形成的机制以及广泛分布的浅层富盐水沃茨的性质（例如成分、温度和水活性）。 水是生命的重要组成部分，定义控制水的可用性的过程对于理解包括火星在内的极端环境的可居住性至关重要。

This study aims to better understand salt accumulation in cold deserts and develop a model of salt transport by groundwater. Cold deserts, like the Antarctic McMurdo Dry Valleys (MDV), are similar to hot deserts in that they accumulate high concentrations of salts because there is not enough water to flush the salts out of the soils into the ocean. The accumulation of salt allows for the creation of brine-rich groundwater that freezes at much lower temperatures. Field work will focus on several groundwater features in the MDV including Don Juan Pond, a shallow lake that accumulates extremely high levels of salts and does not freeze until the temperature reaches -51 degrees C (-60 degrees F). The setting offers the potential to better understand this unique water environment including life at its extremes. It also serves as an analog environment for Mars, a planet that is entirely underlain by permafrost, similar to the MDV. This project will support a doctoral student at the University of Washington Department of Earth and Space Sciences, who will be trained in chemical analysis, chemical and physical modeling, and remote field work in a polar desert environment.Past research suggests that the movement of soluble ions in sediment and soil is controlled by the water activity, permeability, and the thermal regime; however, processes controlling the ionic redistribution in Antarctic environments are poorly constrained. This project aims to better understand the formation, salt redistribution, and water activity of pervasive brine-rich groundwater that is enriched in calcium chloride. A primary goal is to develop a brine thermal;reactive;transport model for the MDV region using data collected from the field to constrain model inputs and ground-truth model outputs. The model will develop a Pitzer-type thermodynamic, reactive transport model and couple it to a ground temperature model. The model will test mechanisms of groundwater formation in the MDV and the properties (e.g. composition, temperature, and water activity) of widespread shallow brine-rich waters. Water is an essential ingredient for life and defining processes that control the availability of water is critical for understanding the habitability of extreme environments, including Mars.