岩性对化学风化的影响:来自亚热带气候条件下花岗岩和安山岩的对比

硅酸盐风化被称为“地质空调”，影响着地球的长期气候变化。控制硅酸盐风化速率的影响因素有很多，包括岩性、植被、气候和构造等。为了探讨岩性单一变量对于硅酸盐风化速率的影响，选取云南省腾冲市北海湿地的数十平方千米区域作为研究对象。该区域仅有花岗岩和安山岩两种岩性出露，花岗岩流域和安山岩流域的构造活动一致，温度、降雨量、径流量等气候条件相同，植被的发育情况也完全相似。基于上述情况，对区域内采集的4个河水样品和1个雨水样品开展水化学质量平衡计算。结果表明:大气输入、硅酸盐风化和碳酸盐风化对于采样流域主量阳离子的贡献比例平均值分别为8.1%、76.5%、16.0%；采样区域内硅酸盐和碳酸盐风化速率平均值分别为5.68、9.96 t·km^-2·年^-1，大气CO₂消耗速率分别为2.68×10⁵、0.29×10⁵ mol·km^-2·年^-1；花岗岩和安山岩的风化速率分别为3.22、8.14 t·km^-2·年^-1。安山岩的风化速率是花岗岩的2.5倍，表明在植被、气候、构造等条件一致的情况下，岩性对化学风化的影响占主导地位。

Effects of Lithology on Chemical Weathering: Comparison of Granite and Andesite in Subtropical Climate

Silicate weathering, which is known as earth’s thermostat, affects earth’s long-term climate change. There are many factors to control the silicate weathering rate, including lithology, vegetation, climate and tectonics. A small area of tens of square kilometers near Beihai wetland of Tengchong city, Yunnan province, was selected to discuss the effects of lithology on the silicate weathering rate. The area develops two kinds of lithology, including granite and andesite; the granite and andesite watersheds have the same tectonics, climate and vegetation conditions. Based on the above situations, 4 river water and 1 rain water samples in Beihai wetland were collected to carry out the calculation of water chemical mass balance. The results show that the average values of the contribution of atmospheric inputs, silicate weathering and carbonate weathering to major cations in sampling watershed are 8.1%, 76.5% and 16.0%, respectively; the average values of silicate and carbonate weathering rates are 5.68, 9.96 t·km^-2·a^-1, the atmospheric CO₂ consuming rates are 2.68×10⁵, 0.29×10⁵ mol·km^-2·a^-1; the weathering rates of granite and andesite are 3.22, 8.14 t·km^-2·a^-1, respectively. The weathering rate of andesite is 2.5 times than that of granite, indicating that the effects of lithology on silicate weathering are dominant under the same conditions of vegetation, climate and tectonics.