The role of supergene sulphuric acid during weathering in small river catchments in low mountain ranges of Central Europe: Implications for calculating the atmospheric CO2 budget
The role of supergene sulphuric acid during weathering in small river catchments in low mountain ranges of Central Europe: Implications for calculating the atmospheric CO2 budget
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DOI：
10.1016/j.chemgeo.2009.07.007
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发表时间：
2009-10
期刊：
影响因子：
3.9
通讯作者：
H. Meyer;H. Strauss;R. Hetzel
中科院分区：
文献类型：
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作者：
H. Meyer;H. Strauss;R. Hetzel
在中欧的两个低山脉河流流域的溶解和悬浮负荷的地球化学允许相关的化学风化率进行比较。岩性的明显差异，即黑森林中的花岗岩与莱茵地块中的古生代沉积物相比，为研究岩性对风化的影响提供了可能性。在这里，我们确定河水的来源，使用稳定同位素比δ 18 OH 2 O和我们量化的地质比例的硫酸盐稳定同位素比δ 34 SSO 4和δ 18 OSO 4。特别是在含有丰富黄铁矿的集水区，确定硫酸盐的地质量很重要，因为黄铁矿的氧化会导致酸性，从而增加风化。我们的研究结果表明，空间平均硅酸盐风化率较高的河流流域Acher和Gutach在黑森林（10- 12吨/平方公里/年）相比，河流流域的Möhne大坝和Aabach大坝在莱茵地块（2- 6吨/平方公里/年）。相应地，黑森林硅酸盐风化的CO2消耗量（334-395× 103 mol/km 2/yr）是莱茵高地（28-151× 103 mol/km 2/yr）的两倍多。黑森林流域的这些较高的速率可能是由于陡峭的斜坡导致较高的机械侵蚀，相应的新鲜未风化岩石颗粒量较高，并且由于莱茵高地的沉积物已经经历了至少一个侵蚀周期。碳酸盐风化速率在莱茵地块集水区的12和38吨/平方公里/年之间变化。硫酸对硅酸盐风化的贡献在莱茵地块集水区（9-16%）高于黑森林集水区（5-7%），因为莱茵地块沉积物中含有丰富的黄铁矿。在过去的103至104年中，来自宇宙成因核素的长期侵蚀率比来自中欧河流负荷的短期侵蚀率高出三倍，这表明二氧化碳的消耗量高出三倍。
The geochemistry of dissolved and suspended loads in river catchments of two low mountain ranges in Central Europe allows comparison of pertinent chemical weathering rates. Distinct differences in lithology, i.e. granites prevailing in the Black Forest compared to Palaeozoic sediments in the Rhenish Massif, provide the possibility to examine the influence of lithology on weathering. Here we determine the origin of river water using the stable isotope ratio δ18OH2Oand we quantify the geogenic proportions of sulphate from stable isotope ratios δ34SSO4and δ18OSO4. Particularly in catchments with abundant pyrite, determination of the geogenic amount of sulphate is important, since oxidation of pyrite leads to acidity, which increases weathering. Our results show that spatially averaged silicate weathering rates are higher for the river catchments Acher and Gutach in the Black Forest (10–12t/km2/yr) compared to the river catchments of the Möhne dam and the Aabach dam in the Rhenish Massif (2–6t/km2/yr). Correspondingly, the CO2consumption by silicate weathering in the Black Forest (334–395×103mol/km2/yr) is more than twice as high as in the Rhenish Massif (28–151×103mol/km2/yr). These higher rates for watersheds of the Black Forest are likely due to steeper slopes leading to higher mechanical erosion with respective higher amounts of fresh unweathered rock particulates and due to the fact that the sediments in the Rhenish Massif have already passed through at least one erosion cycle. Carbonate weathering rates vary between 12 and 38t/km2/yr in the catchments of the Rhenish Massif. The contribution of sulphuric acid to the silicate weathering is higher in the catchments of the Rhenish Massif (9–16%) than in the catchments of the Black Forest (5–7%) due to abundant pyrite in the sediments of the Rhenish Massif. Three times higher long-term erosion rates derived from cosmogenic nuclides compared to short-term erosion rates derived from river loads in Central Europe point to three times higher CO2consumption during the past 103to 104years.