Loess sediments are windblown silt deposits with, in general, a carbonate grain content of up to 30%. While regionally, loess was reported to increase weathering fluxes substantially, the influence on global weathering fluxes remains unknown. Especially on glacial‐interglacial time scales, loess weathering fluxes might have contributed to land‐ocean alkalinity flux variability since the loess areal extent during glacial epochs was larger. To quantify loess weathering fluxes, global maps representing the loess distribution were compiled. Water chemistry of rivers draining recent loess deposits suggests that loess contributes over‐proportionally to alkalinity concentrations if compared to the mean of alkalinity concentrations of global rivers (~4,110 µeq L⁻¹ for rivers draining loess deposits and ~1,850 µeq L⁻¹ for the total of global rivers), showing comparable alkalinity concentration patterns in rivers as found for carbonate sedimentary rocks. Loess deposits, covering ~4% of the ice‐ and water‐free land area, increase calculated global alkalinity fluxes to the coastal zone by 16%. The new calculations lead to estimating a 4% higher global alkalinity flux during the Last Glacial Maximum (LGM) compared to present fluxes. The effect of loess on that comparison is high. Alkalinity fluxes from silicate‐dominated lithological classes were ~28% and ~30% lower during the LGM than recent (with loess and without loess, respectively), and elevated alkalinity fluxes from loess deposits compensated for this. Enhanced loess weathering dampens due to a legacy effect changes in silicate‐dominated lithologies over the glacial‐interglacial time scale.

中文翻译：

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黄土的化学风化及其在最后一次冰期最大值，中全新世和目前的沿海地区对全球碱度通量的贡献

黄土沉积物是风吹淤积物，碳酸盐颗粒含量通常高达30％。虽然在区域上，据报道黄土大大增加了风化通量，但对全球风化通量的影响仍然未知。尤其是在冰川间时间尺度上，黄土的风化通量可能会导致陆海碱度通量的变化，因为在冰川时期黄土的面积范围更大。为了量化黄土的风化通量，编制了代表黄土分布的全球图。排泄新近黄土沉积物的河流的水化学表明，与全球河流的碱度浓度平均值相比，黄土对碱度的贡献超过了比例（排泄黄土沉积物的河流为〜4,110 µeq L ^-1和〜1,850μeqL^-1（全球河流总数），显示出与碳酸盐沉积岩中河流可比的碱度浓度模式。黄土沉积物覆盖了约4％的无冰无水土地面积，使计算得出的流入海岸带的全球碱度通量增加了16％。新的计算导致与当前通量相比，最后一次冰期最大值（LGM）期间全球碱度通量高出4％。黄土对该比较的影响很高。在LGM时期，来自硅酸盐为主的岩性类的碱度通量比近期（分别为黄土和无黄土）低约28％和〜30％，而来自黄土沉积物的高碱度通量对此进行了补偿。黄土风化作用减弱，这是由于在冰期至冰期之间，硅酸盐为主的岩性的遗留效应发生了变化。