Abstract:Release of base cations follow a stoichiometric relationship during soil mineral weathering, and the stoichiometric relationship can only be obtained through simulated experiments. EDTA-ammonium acetate solution at pH 7.0 was used to remove soil base cations (here called treated soil), and then the batch method was used to simulate leaching at different pH values in treated and untreated soils. The release characteristics of base cations from the soils were then investigated during soil mineral weathering. Results showed that leaching solution pH of the untreated soil raised from 3.73±0.14 to 4.23±0.06, attributed to high concentration of NH4+ in the leaching solution. Decrease of the easily weathering minerals reduced the leaching solution pH from 7.39±0.02 to 5.39±0.17 of treated soil during leaching experiment. Exchangeable base cations of the untreated soil could change the release characteristics and release amount of base cations. Base cations in leaching solution declined firstly, and then remained stable. However, K+ and total base cations increased with time in the leaching solution for the treated soil. The total release amount of base cations was lower for the treated soil than that for untreated soil. Soil exchangeable base cations could change the stoichiometric relationship of base cations in leaching solution. The ratio of K+︰Ca2+︰Mg2+︰Na+ was 11︰13︰4︰1 (equivalent charge) in the leaching solution for the untreated soil, while it was 7︰2︰2︰1 for the treated soil. The release amount of K+ was greater than other base cations and most of K+ released came from weathering of mica. Therefore, the soil with base cations removed can be used to estimate mineral weathering rate more accurately and to obtain the accurate base cations stoichiometric relationship. The more acids in the leaching solutions led to more release of base cations, and stronger mineral weathering in the soil. At pH 3.5, 4.5 and 5.5, the difference of the release of base cations among different leaching treatments was not significant during one-year leaching experiment. The effect of solution pH needs to be studied further by long-term leaching experiment. This study suggested that the leaching treatments with simulating acid rain to the soil with base cations removed could be used to study the mineral weathering characteristics and stoichiometric characteristics of base cations released from soils.