Geographic Distribution of Chlorine-36 in Post-Pleistocene Ground Water

9526881 Davis提出的这项研究的目的是确定在50年至1万年前进入地下的水中36Cl的空间变异的性质和原因。有关地理变化的资料对于解释下列水文研究是必要的：干旱地区地下水补给、冰川冰积累速率、地下水“年龄”、盐湖中氯化物的来源、结晶岩中深层地下盐水的来源以及与水文学领域直接和间接有关的其他研究。除了为其他项目提供关键的基线信息外，拟议中的研究还将包括在几个精心挑选的含水层中取样超过1万年的水，以研究过去自然大气中36Cl产生率的变化。拟议研究的主要数据将从对美国各地以及加拿大和墨西哥邻近地区地下水的分析中获得。样品将使用色谱法分析主要离子，使用加速器质谱法分析36/Cl/Cl。此外，还将对氚和14C进行分析，以帮助确定地下水的隔离时间。在干旱的北美西部，可能无法获得合适的水样，可以从土壤剖面中武器沉降物穿透深度以下提取36Cl来获得补充信息。此外，将从北美西部山区的冰川冰中获得一个或多个样本。

9526881 Davis The purpose of the proposed research is to determine the nature and cause of spatial variability of 36Cl in water which has entered the subsurface between 50 and 10,000 years ago. Information concerning geographic variations is necessary for interpretation of hydrologic studies of ground-water recharge in arid regions, of accumulation rates of glacial ice, of ground-water "age", of the origin of chloride in saline lakes, of the origin of deep subsurface brines in crystalline rocks, and of other studies related directly and indirectly to the field of hydrology. In addition to providing critical baseline information for other projects, the proposed research will include sampling of water older than 10,000 years in a few carefully selected aquifers to study changes in past rates of natural atmospheric production of 36Cl. Primary data for the proposed research will be obtained from analyses of ground water from various parts of the United States and from adjacent areas in Canada and Mexico. Samples will be analyzed for major ions using chromatography and for 36/Cl/Cl using accelerator mass spectrometry. In addition, analyses for tritium and 14C will be made to help determine isolation time of ground waters. In arid western North America, where suitable water samples may not be available, supplemental information may be obtained from 36Cl extracted from below the depth of penetration of the weapons fallout in the soil profile. Additionally, one or more samples will be obtained from glacial ice from mountains in western North America.