中国岩石风化作用所致的碳汇能力估算

Estimation of Carbon Sink Capacity Caused by Rock Weathering in China

岩石的风化作用同时参与了短时间尺度和长时间尺度的全球碳循环 ,对碳酸盐岩而言 ,它的风化作用在短时间尺度上对大气二氧化碳循环具有重要影响 ,但在长时间尺度上不产生净碳汇 ;而硅酸盐岩等其他类型岩石的风化过程由于反应速率较慢 ,在短时间尺度上对全球碳循环及其变化反应不灵敏 ,但它所产生的净碳汇是遗漏汇的组成之一 .为了准确估计我国岩石风化所致的碳汇能力 ,简要评价了现有的各种模型和方法 ,并基于GEM -CO2 模型进行了计算 .计算结果表明 ,我国岩石每年因溶蚀、风化作用共消耗的CO2 约为 4 .72× 10 7t,折合成C为 1.4 1× 10 7t,其中由碳酸盐类岩石风化消耗的碳量最多 ,约为 0 .74× 10 7t/a ,占总量的 5 2 .6 5 % .硅酸盐岩及其他类型岩石风化消耗的碳量约为 0 .6 7× 10 7t/a ,占总量的 4 7.35 % .岩石风化所致碳汇能力的空间分布首先取决于岩石类型 ,其次受地区的气候条件控制 .

Rock weathering caused by the carbonic acid reaction with minerals to produce dissolved bicarbonates carried by rivers to the oceans is an important part in carbon cycle. The process causes significant carbon dioxide consumption, the accurate calculation of which may partly explain the missing sink of carbon. The CO_2 uptaken by carbonate dissolution on the continents is counterbalanced by the CO_2 release carbonate precipitation in the ocean. The same is not true for silicate weathering. Silicate weathering is more important than carbonate weathering as a long-term control on atmospheric CO_2. A global erosion model (GEM-CO_2) developed by Amiotte Suchet allows us to calculate the flux of atmospheric/soil CO_2 consumed by chemical erosion of continental rocks. In this paper, the CO_2 consumption by rock weathering in China is estimated based on GEM-CO_2 and the Chinese Resources and Environment Database, whose distribution is shown in a GRID map with a spatial resolution of 1 000 m×1 000 m. The total carbon consumption is about 4.72×10~7 t/a, about 52.65% of which are caused by carbonate. The model results are close to previous estimation of other researches. The flux of CO_2 consumed by rock weathering increases where carbonate rock outcrops are more abundant and when drainage intensity increases. The results show that the main consumption of CO_2 is localized in Guangxi, Guizhou and Chongqing provinces, and west Hubei Province and southwest Hunan Province, because of a high proportion of carbonate rocks and high humidity in a large area.