Collaborative Research: Factors Controlling Chemical Weathering in Regions of Very High Physical Weathering Rates

0309564 Dib在过去的十年里，关于地球表面化学风化的最终控制发生了争论。有些人认为，物理风化的速度，而不是气候，是化学风化的主要控制因素。在构造快速隆起的地区，物理风化程度最高。在西南太平洋/澳大拉西亚地区，许多高海拔海洋岛屿的主要特征是快速上升的构造体制和高频率的降雨事件。那里的高海拔岛屿每年产生至少33%的进入海洋环境的沉积物。正因为如此，HSIs具有地球上已知的最高物理风化率。在我们以前的资助研究（10096285）确定在一些新西兰流域的化学风化率。新测定的化学风化速率与先前测定的物理风化速率的比较表明，虽然化学风化与物理风化的比率很低，但化学风化的绝对速率是有史以来最高的。台湾的初步观察显示，那里的化学风化率也很高。本项目是一个返回新西兰和台湾收集水，悬浮泥沙和土壤和沉积物样品，以进行以下工作：1。使用一套放射性核素（7 Be，137 Cs，210 Pb），以确定在土壤和洪泛区的两个先前调查的流域在新西兰的沉积物的停留时间; 2。利用一套完整的主、次、微量元素分析，评估新西兰与台湾地区以火山岩为主要岩性的集水区的物理与化学风化速率;利用活动1和活动2的数据以及我们以前研究的结果，制定一个定量框架，以评估物理和化学风化率之间的关系，特别是在这些物理风化程度很高的地区。在我们收集土壤和河床沉积物7 Be、137 Cs和210 Pb剖面的地点，我们将收集更多的样品，供今后分析铀和钍系列核素之用。这些样品将被存档，直到时间和资金允许，我们将在OSU的MARC分析中心使用ICP-MS分析这些样品。这些数据将用于计算流域停留时间。我们计划这些额外的活动，以回应审查员的意见，即最初选择的核素半衰期太短，无法用于计算可能的分水岭停留时间。利用铀和钍的数据，我们可以使用Plater等人（1994）、Vigier等人（2001）、Moreira-Nordemann（1980）和Marques等人（2003）的方法来计算侵蚀速率和时间尺度，这项工作的更广泛影响将包括向研究生提供培训，以及与新西兰和台湾科学家PI计划建立一个网站，将来自拟议研究的所有数据和来自ISO 90096285的数据放在网站上，以便广大科学界可以访问。这项研究在促进对大气中二氧化碳浓度的全面了解方面具有重要的社会意义。由于地球表面硅酸盐矿物的化学风化被认为是大气CO2浓度的主要控制因素，因此这项研究对理解温室气体调节机制具有重要意义。

0309564DibbOver the past decade, a debate has taken place concerning the ultimate controls on chemical weathering at Earth's surface. Some have argued that the rate of physical weathering, not climate, is the major control on chemical weathering. Physical weathering is highest in areas of rapid tectonic uplift. Rapidly uplifting tectonic regimes with high frequency rainfall events are the dominant feature of many high-standing oceanic islands in the SW Pacific/Australasian region. High-standing islands (HSIs) there produce at least 33% of the sediment entering the marine environment annually. Because of this, HSIs have some of the highest physical weathering rates known on Earth. Research in our previous grant (EAR 0096285) determined chemical weathering rates in some New Zealand watersheds. Comparison of newly determined chemical weathering rates to the previously determined physical weathering rates showed that, although the ratio of chemical to physical weathering is low, the absolute rates of chemical weathering are some of the highest ever observed. Preliminary observations from Taiwan indicate that chemical weathering rates there are also very high. The current project is a return to New Zealand and Taiwan to collect water, suspended sediment and soil and sediment samples in order to conduct the following work: 1. Use a suite of radionuclides (7Be, 137Cs, 210Pb) to determine residence times of sediments in the soils and floodplains of two previously investigated watersheds in New Zealand; 2. Use a full suite of major, minor and trace element analyses to evaluate the physical and chemical weathering rates in New Zealand and Taiwan watersheds whose primary lithology is volcanic rocks; 3. Use data from activities 1 and 2 and the results of our previous research to develop a quantitative framework to evaluate the relationship between physical and chemical weathering rates, especially in these regions of very high physical weathering. At the locations where we collect soil and streambed sediment profiles for 7Be, 137Cs and 210Pb, we shall collect additional samples for future analysis of uranium and thorium series nuclides. These samples will be archived until time and funds permit, we shall analyze these samples using the ICP-MS at OSU's MARC analytical center. The data will be used for calculation of watershed residence times. We plan these additional activities in response to the reviewer comment that the original choice of nuclides had half-lives too short to be useful in calculating the likely watershed residence times. Using the uranium and thorium data, we can use the approaches of Plater et al. (1994), Vigier et al. (2001), Moreira-Nordemann (1980) and Marques et al. (2003) to calculate erosion rates and timescales, and watershed residence times.Broader impacts of the work will include training provided to graduate students and the building of international partnerships with New Zealand and Taiwanese scientists. The PIs plan to establish a website where all the data from the proposed research and from EAR 0096285 will be placed so that it will be accessible by the broad scientific community. This research has important societal relevance in contributing to the overall understanding of CO2 concentration in the atmosphere. Because the chemical weathering of silicate minerals on the surface of Earth is thought to be the major control on the atmospheric CO2 concentration, this research has important implications for understanding the mechanisms of greenhouse gas regulation.