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首页> 外文期刊>Marine Chemistry >Extended time series measurements of submarine groundwater discharge tracers (~(222)Rn and CH_4) at a coastal site in Florida
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Extended time series measurements of submarine groundwater discharge tracers (~(222)Rn and CH_4) at a coastal site in Florida

机译：佛罗里达沿海沿岸海底地下水排放示踪物（〜（222）Rn和CH_4）的扩展时间序列测量

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We report the results of an experiment in which we measured ~(222)Rn (15,000 observations). CH_4 (40,000 observations), and associated variables in seawater nearly continuously at a coastal site in the Gulf of Mexico for almost two years. Significant correlations between ~(222)Rn and CH_4 imply that they are derived from a common source, most likely groundwater. However, we were unable to explain the overall tracer variability as a single function of groundwater table height, temperature, tidal range, and wind speed, indicating multiple, overlapping controls on SGD dynamics at this site. Methane and radon concentrations may vary 2-fold in a given well in the subterranean estuary over tidal time scales, demonstrating the complexity of determining SGD endmember concentrations and suggesting that unaccounted for temporal changes in groundwater may explain some of the patterns observed in seawater. Surprisingly, the variability of ~(222)Rn and CH_4 in seawater over short (e.g., hourly) time scales was generally comparable to or even more pronounced than fluctuations over much longer (e.g., monthly) scales. While high tracer concentrations usually occurred during low tide and low tracer concentrations during high tide, this pattern was occasionally inverted or absent indicating that no single model can be used to describe the entire data set. We also describe a sequence of events in which SGD tracers were depleted in coastal waters during storms and regenerated afterwards. We found no increase in radon activities immediately after the largest storm (75 mm rainfall) perhaps because of the short residence times of groundwater in contrast to the ingrowth time of radon. Marine controls appeared to be the most important SGD drivers with only minor influence relating to the shallow and deep aquifers. This implies that seasonal investigations of SGD tracers in the coastal ocean may be masked by short-term variability.
机译：我们报告了测量〜（222）Rn（15,000个观察值）的实验结果。 CH_4（40,000个观测值）及其相关变量在墨西哥湾的一个沿海地点几乎持续了近两年。 〜（222）Rn和CH_4之间的显着相关性暗示它们是从共同的来源（最有可能是地下水）中提取的。但是，我们无法将示踪剂的总体变异性解释为地下水位高度，温度，潮汐范围和风速的单一函数，这表明该站点对SGD动态的多重重叠控制。在潮汐时间尺度内，地下河口中给定井中甲烷和concentrations的浓度可能会发生2倍变化，这表明确定SGD端基浓度的复杂性，并表明无法解释地下水的时间变化可能解释了海水中观察到的某些模式。令人惊讶地，在短（例如，每小时）尺度上海水中〜（222）Rn和CH_4的变化通常与更长（例如，每月）尺度上的波动相当或什至比其显着。尽管高示踪剂浓度通常发生在退潮时，而低示踪剂浓度发生在涨潮时，但这种模式偶尔会倒置或不存在，这表明无法使用单个模型来描述整个数据集。我们还描述了一系列事件，其中SGD示踪剂在暴风雨期间耗尽了沿海水域，之后又重新生成。我们发现在最大的暴风雨（75毫米的降雨）之后，ra的活动没有增加，这可能是因为与residence的生长时间相比，地下水的停留时间短。海洋控制似乎是最重要的SGD驱动程序，对浅层和深层含水层的影响很小。这意味着在沿海海洋中，SGD示踪剂的季节性调查可能会被短期变化掩盖。

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