Chemical weathering rates of silicate-dominated lithological classes and associated liberation rates of phosphorus on the Japanese Archipelago-Implications for global scale analysis
Chemical weathering rates of silicate-dominated lithological classes and associated liberation rates of phosphorus on the Japanese Archipelago-Implications for global scale analysis
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DOI：
10.1016/j.chemgeo.2010.12.004
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发表时间：
2011-08-21
期刊：
影响因子：
3.9
通讯作者：
Moosdorf, Nils
中科院分区：
文献类型：
--
作者：
Hartmann, Jens;Moosdorf, Nils
岩性是地球表面的一个重要特征，其性质影响着化学风化速率。特别是非硅酸盐矿物可能对硅酸盐为主的岩性类的风化衍生通量有重要贡献。日本群岛主要由硅酸盐为主的岩性和高比例的火山组成。然而，在如此大的区域内，化学风化速率的空间明确表示仍然是困难的，因为许多控制化学风化速率的因素是相互关联的。由于岩性的空间异质性，本文采用多岩性模型方法估算未监测区域的空间显式化学风化速率。为了实现这一目标，使用381个集水区的水化学数据来训练一组模型，以识别各种提出的影响化学硅酸盐岩石风化速率的因素（CSRWR：阳离子加溶解二氧化硅通量）的贡献。受监测的集水区覆盖了日本群岛的44%。阳离子化学风化速率（不包括硅）与CSRWR呈线性相关，如果由于硅释放速率增加而存在基性火山或火山碎屑流，则显示出异常值。岩性和径流被认为是化学风化速率的最强预测因子。温度和坡度对区域尺度预测的相关性较低，而进一步提出的土壤性质或土地覆盖等因子未被确定为主要预测因子。后一项发现部分归因于地理数据质量、参数值的低变异性以及所提出的控制因素与岩性或径流的空间相关性。计算出的群岛平均CSRWR与25吨公里（-2）a（-1）相似，在监测的集水区范围为5.9至107吨公里（-2）a（-1）。按岩性分类的风化速率随径流的变化可分为三类：a)火山碎屑流的化学风化速率最高；B)冲积矿床、混合沉积物和中等速率的基性至中级火山；c)变质岩、硅屑沉积岩、酸性火山岩、酸性深部岩和松散沉积岩（冲积沉积岩除外），速率最低。岩源硫的识别将使所考虑的流域的CSRWR增加9.7%。结果表明，岩石类酸性火山岩和松散沉积物对硫通量的贡献高于平均水平。讨论了这一观察结果可能存在的偏差。非硅酸盐钙矿物的钙通量（除硅酸盐钙通量外，还称为过量钙通量）的贡献平均约为CSRWR的10%，其值范围很广。化学风化计算的钙过量与总钙通量比值在酸性深部、变质岩、硅屑沉积岩、混合沉积岩和酸性火山岩岩性中分别约为62%、75%、56%、83%和84%。这表明非硅酸盐钙矿物对这些岩性类别的钙贡献很大。由于化学风化作用，从岩石中释放的磷估计在1 kg P km(-2)a（-1）到390 kg P km(-2)a（-1）之间。由于岩石中施磷量的不同，不同岩性径流对磷释放模式的依赖性与CSRWRs不同。确定的空间磷释放模式表明，考虑化学风化的动态和空间分解的磷释放速率可能会改善生态系统的研究。以后的发现对于分析岩石p释放在地质时间尺度上通过生态系统功能对气候系统的影响可能具有重要意义。磷释放模型在全球尺度上的首次应用表明，硅酸盐占主导的岩性（不包括碳酸盐沉积岩）的化学风化作用每年释放160万吨磷(13.8 kg P km（-1) A(-1)）。(C) 2010 Elsevier B.V.版权所有
Lithology is an important characteristic of the terrestrial surface, whose properties influence chemical weathering rates. Specifically non-silicate minerals may contribute significantly to the weathering derived fluxes from silicate-dominated lithological classes. The Japanese Archipelago consists of predominantly silicate-dominated lithologies with a high proportion of volcanics. However, the spatially explicit representation of chemical weathering rates remains difficult for such a large region, because many controlling factors on chemical weathering rates are correlated with each other. Due to the spatial heterogeneity of lithology, a multi-lithological model approach to estimate spatially explicit chemical weathering rates for unmonitored areas is applied here. To achieve this, hydrochemical data of 381 catchments are used to train a set of models, recognizing the contribution of a variety of proposed factors influencing chemical silicate rock weathering rates (CSRWR: cations plus dissolved silica flux). The monitored catchments cover similar to 44% of the Japanese Archipelago. Cation chemical weathering rates (excluding Si) are linearly correlated with CSRWR and show outliers if basic volcanics or pyroclastic flows are present due to increased silica release rates. Lithology and runoff are identified as the strongest predictors for chemical weathering rates. Temperature and gradient of slope are of less relevance for the regional scale prediction while further proposed factors like soil properties or land cover are not identified as major predictors. Latter findings are partly attributed to geodata quality, low variability of parameter values as well as spatial correlations of proposed controlling factors with lithology or runoff.The calculated average CSRWR of the Archipelago is similar to 25 t km(-2)a(-1) and ranges from 5.9 to 107 t km(-2)a(-1) in monitored catchments. Weathering rates per lithological class as a function of runoff can be grouped into three classes: a) pyroclastic flows showing the highest chemical weathering rates; b) alluvial deposits, mixed sediments and basic to intermediate volcanics with medium rates; and c) metamorphics, siliciclastic sediments, acid volcanics, acid plutonics and unconsolidated sediments (other than alluvial deposits), showing the lowest rates. The recognition of lithogenic sulfur would add 9.7% to CSRWR of considered catchments. Results suggest that the lithological classes acid volcanics and unconsolidated sediments contribute above average to the sulfur fluxes. Possible biases of this observation are discussed.The contribution of Ca-fluxes from non-silicate calcic minerals (named Ca-excess, Ca-fluxes in addition to silicate Ca-fluxes) is about 10% of the CSRWR on average and is attributed by a wide value range. The calculated ratio "Ca-excess to total Ca-fluxes" from chemical weathering averages around 62%, 75%, 56%, 83% and 84% for the lithological classes acid plutonics, metamorphics, siliciclastic sediments, mixed sediments and acid volcanics, respectively. This suggests a major Ca-contribution from non-silicate calcic minerals for these lithological classes. Phosphorus release from rocks due to chemical weathering is estimated to be between 1 kg P km(-2)a(-1) and 390 kg P km(-2)a(-1). The P-release patterns in dependence of runoff per lithological class are different from CSRWRs due to differences of applied P-content in rocks. The identified spatial P-release patterns suggest that the consideration of dynamic and spatially resolved P-release rates by chemical weathering might improve ecosystem studies. Later findings may be of importance for analysing the influence of P-release from rocks on the climate system via ecosystem functioning on geological time scales. A first application of the P-release model to the global scale suggests an annual release of 1.6 Mt P (13.8 kg P km(-1)a(-1)) by chemical weathering of silicate dominated lithological classes (excluding carbonate sedimentary rocks). (C) 2010 Elsevier B.V. All rights reserved.