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Time‐series of δ26Mg values in a headwater catchment reveal decreasing magnesium isotope variability from precipitation to runoff
Hydrological Processes ( IF 3.2 ) Pub Date : 2021-03-08 , DOI: 10.1002/hyp.14116
Martin Novak 1 , Alexandre Andronikov 1 , Pavel Kram 1 , Jan Curik 1 , Frantisek Veselovsky 1 , Marketa Stepanova 1 , Eva Prechova 1 , Ondrej Sebek 1 , Leona Bohdalkova 1
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Data on temporal variability in Mg isotope ratios of atmospheric deposition and runoff are critical for decreasing the uncertainty associated with construction of isotope mass balances in headwater catchments, and statistical evaluation of isotope differences among Mg pools and fluxes. Such evaluations, in turn, are needed to distinguish between biotic and abiotic contributions to Mg2+ in catchment runoff. We report the first annual time‐series of δ26Mg values simultaneously determined for rainfall, canopy throughfall, soil water and runoff. The studied 55‐ha catchment, situated in western Czech Republic, is underlain by Mg‐rich amphibolite and covered by mature spruce stands. Between 1970 and 1996, the site received extremely high amounts of acid deposition and fly ash form nearby coal‐burning power plants. The δ26Mg values of open‐area precipitation (median of −0.79‰) at our study site were statistically indistinguishable from the δ26Mg values of throughfall (−0.73‰), but significantly different from the δ26Mg values of soil water (−0.55‰) and runoff (−0.55‰). The range of δ26Mg values during the observation period decreased in the order: open‐area precipitation (0.57‰) > throughfall (0.27‰) > runoff (0.21‰) > soil water (0.16‰). The decreasing variability in δ26Mg values of Mg2+ from precipitation to soil water and runoff reflected an increasing homogenization of atmospheric Mg in the catchment and its mixing with geogenic Mg. In addition to atmospheric Mg, runoff also contained Mg mobilized from the three major solid Mg pools, bedrock (δ26Mg of −0.32‰), soil (−0.28‰), and vegetation (−0.31‰). The drought of summer 2019 did not affect the nearly constant δ26Mg value of runoff. Collectively, our data show that within‐catchment processes buffer the Mg isotope variability of the atmospheric input.

中文翻译:

上游水源流中δ26Mg值的时间序列显示,镁同位素从降水到径流的变异性正在降低

大气沉积和径流的镁同位素比率随时间变化的数据对于减少与上游水源流域同位素质量平衡的构建相关的不确定性以及镁池和通量之间同位素差异的统计评估至关重要。反过来,需要这种评估来区分流域径流中Mg 2+对Mg 2+的生物贡献和非生物贡献。我们报告第一次年度时间序列的δ 26同时确定降雨,冠层穿透,土壤水分和径流的Mg值。位于捷克共和国西部的经过研究的55公顷流域位于富含镁的角闪石之下,并被成熟的云杉林所覆盖。在1970年至1996年之间,该厂附近的燃煤发电厂沉积了极大量的酸和飞灰。该δ 26在我们研究的网站开放区域降水量(-0.79的平均‰)的镁值分别来自δ统计区分26的穿透镁值(-0.73‰),但是从δ显著不同的26土壤水分的镁值(-0.55‰)和径流(-0.55‰)。δ的范围26观测期的Mg值依次降低:开阔地带降水(0.57‰)>穿透水(0.27‰)>径流(0.21‰)>土壤水(0.16‰)。在δ减小可变性26个的Mg的Mg值2+从沉淀到土壤水分和径流反射大气的Mg在集水越来越均质化和其与镁环境地球化学混合。除了大气镁,径流还含镁从三大固体镁池动员,基岩(δ 26镁-0.32‰),土(-0.28‰),和植被(-0.31‰)。2019夏季的干旱并没有影响到几乎恒定δ 26径流的镁值。总体而言,我们的数据表明,集流过程可缓冲大气输入的Mg同位素变异性。
更新日期:2021-04-29
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