The Effect of Quaternary Climate Change on the Balance of Silicate Mineral Weathering and Eolian Input in Desert Soils

Capo大气过程与陆地风化的相互作用对于理解全球地球化学循环及其与气候变化的关系至关重要。土壤-大气系统中阳离子通量的量化是这一问题的重要组成部分。了解气候变化、时间、母质和其他成土因素对沙漠土壤发育和元素储存和流动的影响也至关重要。本研究的目的是量化大气输入和硅酸盐矿物风化对第四纪沙漠土壤成土作用的影响。我们将结合实地、质量平衡和同位素示踪研究来研究过去200万年来沙漠土壤中土壤形成的因素。来自美国农业部土壤保持局沙漠土壤地貌项目的土壤剖面，位于内华达州拉斯克鲁塞斯附近，以及夏威夷科哈拉半岛，将对第四纪以风成风和硅酸盐风化为主的干旱至半干旱环境中大气阳离子添加和原位硅酸盐风化作用的限制进行研究。锶同位素测量将与微形态研究、主要元素和微量元素分析以及阳离子质量平衡计算相结合，以便：(1)确定沙漠土壤系统中阳离子的来源并量化其相对贡献；(2)研究土壤剖面中硅酸盐矿物风化的位置、速率和机制；(3)确定硅酸盐矿物风化和风成物输入对土壤阳离子收支的相对贡献随气候变化的变化。这两个地点的土壤年代序列都有良好的记录和保存，可以对已知年龄和气候历史的现代、遗存和埋藏土壤剖面进行详细采样。测定土壤母质、当地大气粉尘和雨水输入以及土壤碳酸盐的锶同位素和主微量元素组成。土壤中钙的来源将通过锶同位素分析来确定。质量平衡分析将量化土壤系统中阳离子的增益、损失和再分配。这些数据将与现有的放射性碳、地层、稳定同位素、花粉和古水文记录进行对比。这些数据将有助于重建第四纪沙漠土壤形成的历史，作为环境变化的函数。

9614875 Capo The interaction of atmospheric processes and terrestrial weathering is crucial to understanding global geochemical cycling and its relationship to climate change. The quantification of cation fluxes in the soil-atmosphere system is an essential part of this problem. Knowledge of the effect of climate change, time, parent material and other soil-forming factors on the development of desert soil and the storage and mobility of elements is also critical. The objective of this research is to quantify the effect of atmospheric input and silicate mineral weathering on Quaternary desert soil pedogenesis as a function of climatic regime. We will use a combination of field, mass balance and isotope tracer studies to examine the factors involved in soil formation in desert soils over the last 2 million years. Soil profiles from the Desert Soil-Geomorphology Project of the U.S.D.A. Soil Conservation Service, near Las Cruces, NM, and from Kohala Peninsula, Hawaii, will be studied to place constraints on the role of atmospheric addition of cations and in situ silicate weathering in arid to semiarid environments in an eolian-dominated and a silicate weathering-dominated system over Quaternary time. Strontium isotope measurements will be combined with micromorphologic studies, major and trace element analyses, and cation mass balance calculations in order to (1) determine the sources and quantify the relative contributions of cations into desert soil systems; (2) examine the locations, rates and mechanisms of silicate mineral weathering within the soil profile; and (3) identify shifts in the relative contributions of silicate mineral weathering and eolian input to the soil cation budget as a function of climate change. Well documented and preserved soil chronosequences at both locales permit detailed sampling of modern, relict, and buried soil profiles of known age and climatic history. The strontium isotopic and major and trace element composition of soil parent material, local atmo spheric inputs from dust and rain, and soil carbonate will be determined. Calcium provencance in the soil will be determined by Sr isotopic analysis. Mass balance analysis will quantify the gain, loss, and redistribution of cations in the soil system. These data will b correlated with existing radiocarbon, stratigraphic, stable isotope, pollen and paleohydrology records. The data will aid in reconstructing the history of desert soil formation over the Quaternary as a function of environmental change.