Comparison of 14C Collected by Precipitation and Gas-Strip Methods for Dating Groundwater
Comparison of 14C Collected by Precipitation and Gas-Strip Methods for Dating Groundwater
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降水法和气带法收集的 14C 地下水测年方法的比较
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Toshihiro Kato
中科院分区：
文献类型：
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作者：
Kotaro Nakata;T. Hasegawa;T. Iwatsuki;Toshihiro Kato
摘要利用地下水中溶解无机碳（DIC）的含量，根据放射性碳的浓度估算地下水的停留时间。DIC通常通过气提或沉淀（SrCO 3或BaCO 3）法提取。在这项研究中，气体剥离和沉淀法DIC适用于人工制备的NaHCO 3溶液和天然地下水，以估计14 C定年的两种方法的确定性。14 C值通过气提方法获得的NaHCO 3溶液具有不同的盐度，DIC，和14 C浓度接近理论预测的14 C值的基础上的NaHCO 3粉末的14 C值。相反，通过降水法获得的14 C值总是显示出高于预测值的值。气提法和沉淀法之间的14 C值差异被认为是由沉淀法中使用的NaOH溶液中的现代碳的污染引起的。发现在沉淀过程中源自NaOH溶液的现代碳的污染范围为小于1 mg/L至约1 mg/L。应根据DIC、地下水14 C浓度和研究目的仔细考虑降水法对地下水的适用性。
Abstract Dissolved inorganic carbon (DIC) in groundwater is used to estimate the residence time based on radiocarbon concentration. DIC is usually extracted by a gas-strip or precipitation (SrCO3 or BaCO3) method. In this study, the gas-strip and precipitation methods of DIC were applied to both artificially prepared NaHCO3 solutions and natural groundwater to estimate the certainty of the two methods for 14C dating. 14C values obtained by the gas-strip method for NaHCO3 solutions with distinct salinity, DIC, and 14C concentrations were close to the theoretically predicted 14C value based on the 14C value of NaHCO3 powder. Conversely, the 14C value obtained by the precipitation method always showed higher values than the predicted values. The difference in 14C value between the gas-strip and precipitation methods was assumed to be caused by the contamination of modern carbon in the NaOH solution used in the precipitation method. The contamination of modern carbon derived from the NaOH solution during precipitation was found to range from less than 1 mg/L to about 1 mg/L. The applicability of the precipitation method for groundwater should be considered carefully according to the DIC, 14C concentration of groundwater, and purpose of the study being conducted.