硫酸型酸雨参与碳酸盐岩溶蚀的研究进展

碳酸盐岩的H2CO3溶蚀产生岩溶碳汇,占整个岩石风化碳汇的 94%。西南岩溶区硫酸型酸雨严重,硫酸型酸雨广泛参与碳酸盐岩的溶蚀。H2SO4参与的碳酸盐岩风化是一个大气CO2净释放过程,具有减汇作用巨大。另一方面,岩溶区石灰土壤和地下水具有较高的pH值及盐基饱和度,对H+有巨大的缓冲作用,大气酸沉降在碳酸盐岩地区可能并不会造成地下水的HCO3-和pH降低;相反,较高浓度的SO42-所产生的盐效应和SO2-4与各种阳离子形成的离子对会增大方解石、白云石溶解度,可增强H2CO3对碳酸盐的溶蚀,这可能会使岩溶作用产生更大的碳汇效应。因此,硫酸型酸雨参与碳酸盐岩风化的减汇效应不仅可能被高估,硫酸型酸雨还可能增强碳酸盐岩的H2CO3溶蚀,具有增加岩溶碳汇效应的作用。应结合石灰土壤对大气酸沉降的缓冲容量和阈值及大气酸沉降的H+与土壤中盐基离子的交换量,并综合考虑盐效应、离子对作用、同离子效应,客观评价硫酸型酸雨流经石灰土壤层后对碳酸盐岩溶蚀吸收大气/土壤CO2的影响 

Research progress of sulfuric acid rain participating in the dissolution of carbonate rocks

Carbonate rocks dissolved by carbonic acid plays an important role in contributing to the atmospheric and pedospheric CO2 uptake, which accounts for 94% of the globe carbon sinks of rock weathering. Nowadays, the sulfuric acid rain in karst area of southwest China is serious, and acid rain is widely involved in the dissolution of carbonate rocks. On one hand, the weathering of carbonate rocks with sulfuric acid participation is a net release process of atmospheric CO2, which has a great effect on reducing the sink; on the other hand, the soil formed by the weathering of carbonate rocks and the karst groundwater have higher pH and salt base saturation, which would have a great buffer effect on H+. Thus, atmospheric acid deposition in carbonate rock area will not cause the decrease of HCO3- and pH of groundwater. On the contrary, the salt load produced by relatively high concentrations of SO42- and the ion pairs formed by SO42- with various cations will increase the solubility of calcite and dolomite, which could enhance the carbonate dissolution by H2CO3 and produce more CO2 uptake in karst processes. Therefore, the deficit of CO2 uptake involved in carbonate weathering by sulfuric acid rain may be overvalued, the acid rain can also enhance the dissolution of carbonate rocks, and increase the CO2 consumption by carbonate weathering. We Should combine with the soil buffer capacity and the threshold value to the atmospheric acid deposition and exchange capacity of the soil base ion with the H+ from atmospheric acid deposition, and consider the salt effect, ion pairs and common ion, to objectively evaluate the effect of sulfuric acid rain, after flowing through the limestone soil layer, on the absorption of atmospheric/soil CO2 by carbonate rocks dissolution.