Doctoral Dissertation Research: Geochemical Weathering Controls on Soil Nitrogen and Phosphorus: Possible Implications of Global Change

目前对北极气候变化的预测估计，平均每年气温上升2至4.5摄氏度。 虽然二氧化碳和其他“温室”气体的排放和大气滞留的增加被认为是这些增加的主要原因，但北极是世界上被认为存在净碳汇的地区之一，植物和陆地表面吸收的碳多于排放的碳。 虽然这种汇在某种程度上减轻了大气碳积累的影响，但水分供应或温度的变化可能会改变该区域化学交换的动态。 本博士论文研究项目将研究北极化学交换的一个方面，特别是地球化学风化在控制土壤氮和磷的可用性在瑞典北极Karkevagge的全球变化情景下的作用。 该项目将利用实地数据收集和实验室模拟，开发一个模型，预测在不断变化的环境参数下氮和磷向环境中的释放速率。 这项工作将建立在Karkevagge初步实地调查化学风化的空间变异性。 以往的工作表明，化学风化是在这个山谷的地貌系统的重要组成部分，化学风化的模式在空间上是不同的。 风化率和地表水溶质蚀变将通过结合原位风化测量与电子显微镜和溪流水化学测量进行研究。 地球化学模型将用于确定电子探针风化计算和测量的水化学之间的化学途径。 有关土壤温度、矿物学、粒度和水通量的数据将用于生成实验室模拟实验，以研究人类引起的环境变化对氮和磷向环境释放的潜在影响。 这些模拟将用于了解这些参数对风化的控制。 这些模拟可用作预测自然系统中风化速率的模型的一阶检验。 然后将用现场数据验证模型。 还将进行进一步的模拟，研究温度升高和pCO2对风化速率的影响。 然后，将把数据合并成一个综合模型，预测氮和磷通过地球化学风化作用释放到北极环境中。 该模型将预测人类引起的环境变化对该系统的可能改变。 通过该项目调查的变化可能在改变北极生态系统的碳固存能力方面发挥作用。 北极生态系统是全球气候模型中的主要未知因素之一，因为碳固存的速度在很大程度上是未知的。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。

Current predictions of climate change in the Arctic estimate mean annual air temperature increases of between 2 and 4.5 degrees C. Although increases in the emission and atmospheric retention of carbon dioxide and other "greenhouse" gases are seen as the primary causes of these increases, the Arctic is one of the world's regions where a net carbon sink is thought to exist, with more carbon is absorbed by plants and the land surface than is emitted. While this sink somewhat ameliorates the impacts of atmospheric carbon accumulation, changes in moisture availability or temperature could alter the dynamics of chemical exchange in the region. This doctoral dissertation research project will examine one facet of chemical exchange in the Arctic, specifically the role of geochemical weathering in controlling the availability of soil nitrogen and phosphorus under a global change scenario in Karkevagge in the Swedish Arctic. This project will utilize both field data collection as well as laboratory simulations to develop a model that predicts the rates of nitrogen and phosphorus release into the environment under changing environmental parameters. This work will build on preliminary fieldwork in Karkevagge investigating the spatial variability of chemical weathering. Previous work has suggested that chemical weathering is an important component of the geomorphic system in this valley and that the patterns of chemical weathering vary spatially. Weathering rates and surface water solute alteration will be investigated by combining in situ weathering measurements made with electron microscopy and stream water chemical measurements. Geochemical models will be used to determine the chemical pathways between the weathering calculations from the electron microprobe and the measured water chemistry. Data on soil temperature, mineralogy, grain size, and water fluxes will be used to generate a laboratory simulation experiment for investigating the potential effects of human-induced environmental change on the release of nitrogen and phosphorus into the environment. These simulations will be used to understand the controls these parameters have on weathering. These simulations can be used as a first-order test of a model predicting weathering rates in natural systems. The models then will be validated with field data. Further simulations investigating the effects of increasing temperature and pC02 on weathering rates will also be undertaken. Data will then be combined into a synthetic model predicting the release of nitrogen and phosphorus into Arctic environments by geochemical weathering. This model will make predictions about the possible alterations to this system by human-induced environmental change. The changes investigated through this project may play a role in altering the carbon sequestration ability of Arctic ecosystems. Arctic ecosystems are one of the major unknowns in global climate models, because the rates of carbon sequestration are largely unknown. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.