Effects of temperature on silicate weathering: Solute fluxes and chemical weathering in a temperate rain forest watershed, Jamieson Creek, British Columbia
Effects of temperature on silicate weathering: Solute fluxes and chemical weathering in a temperate rain forest watershed, Jamieson Creek, British Columbia
复制标题
温度对硅酸盐风化的影响：不列颠哥伦比亚省贾米森溪温带雨林流域的溶质通量和化学风化
DOI：
10.1016/j.chemgeo.2009.09.005
复制
发表时间：
2010
期刊：
影响因子：
3.9
通讯作者：
S. Brantley
中科院分区：
文献类型：
--
作者：
Benjamin F. Turner;A. White;S. Brantley
长期以来，硅酸盐矿物的化学风化作用一直被认为是大气二氧化碳的汇，风化作用与气候之间的反馈被认为会影响全球气候。虽然人们认为较高的温度会增加风化的速度，但在凉爽气候下，由于冰的机械风化导致矿物暴露增加，会加速风化。在这项研究中，研究了一个温带小流域的硅酸盐矿物的化学风化作用。 Jamieson Creek 流域被成熟的针叶林覆盖，年降水量很高（4000 毫米），大部分以降雨形式存在，其下方是石英闪长岩基岩和冰碛物。孔隙水浓度梯度分析表明，水力不饱和烧蚀碴中的风化作用主要是斜长石和角闪石的溶解。然而，分水岭规模溶质质量平衡表明钾和钙的相对通量较高，表明这些溶质可能从相对未风化的沉降池中优先浸出。根据分水岭尺度溶质质量平衡计算出的斜长石和角闪石的风化速率与使用孔隙水浓度梯度确定的速率相似。波多黎各的 Rio Icacos 盆地是一个原始热带流域，年降水量和基岩相似，但风化层特性不同，与波多黎各的 Rio Icacos 盆地相比，温暖地区流出的溪流中的风化产物通量分别高出 1.8 至 16.2 倍，风化层剖面平均斜长石风化率高出 3.8 至 9.0 倍。这表明，阿伦尼乌斯效应预测，当温度从 3.4°C 升至 22°C 时，斜长石的溶解速率将增加 3.5 至 9 倍，这可能解释了 Rio Icacos 遗址更大的风化通量和速率。然而，两个地点之间钾和钙通量的较小差异归因于这些溶质从杰米森溪的冰川沉积物中加速浸出。我们的研究结果表明，在高降雨量和有利地形的条件下，温暖热带系统中硅酸盐矿物的风化速率往往高于冷温带系统，即使温带系统受到冰川作用的干扰，在新鲜矿物表面区域沉积风化层较高的区域。
Chemical weathering of silicate minerals has long been known as a sink for atmospheric CO2, and feedbacks between weathering and climate are believed to affect global climate. While warmer temperatures are believed to increase rates of weathering, weathering in cool climates can be accelerated by increased mineral exposure due to mechanical weathering by ice. In this study, chemical weathering of silicate minerals is investigated in a small temperate watershed. The Jamieson Creek watershed is covered by mature coniferous forest and receives high annual precipitation (4000mm), mostly in the form of rainfall, and is underlain by quartz diorite bedrock and glacial till. Analysis of pore water concentration gradients indicates that weathering in hydraulically unsaturated ablation till is dominated by dissolution of plagioclase and hornblende. However, a watershed scale solute mass balance indicates high relative fluxes of K and Ca, indicating preferential leaching of these solutes possibly from the relatively unweathered lodgement till. Weathering rates for plagioclase and hornblende calculated from a watershed scale solute mass balance are similar in magnitude to rates determined using pore water concentration gradients. When compared to the Rio Icacos basin in Puerto Rico, a pristine tropical watershed with similar annual precipitation and bedrock, but with dissimilar regolith properties, fluxes of weathering products in stream discharge from the warmer site are 1.8 to 16.2-fold higher, respectively, and regolith profile-averaged plagioclase weathering rates are 3.8 to 9.0-fold higher. This suggests that the Arrhenius effect, which predicts a 3.5- to 9-fold increase in the dissolution rate of plagioclase as temperature is increased from 3.4° to 22°C, may explain the greater weathering fluxes and rates at the Rio Icacos site. However, more modest differences in K and Ca fluxes between the two sites are attributed to accelerated leaching of those solutes from glacial till at Jamieson Creek. Our findings suggest that under conditions of high rainfall and favorable topography, weathering rates of silicate minerals in warm tropical systems will tend to be higher than in cool temperate systems, even if the temperate system is has been perturbed by an episode of glaciation that deposits regolith high in fresh mineral surface area.