| 桂林岩溶区石灰土壤对酸雨缓冲作用的观测及其对岩溶碳汇的指示意义 |
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| 关键词:acid rain pH acid buffering capacity of soil soil water cation exchange capacity karst carbon sink effect |
| 基金项目:广西重点基金项目“酸雨条件下岩溶动力系统内碳酸盐岩溶蚀过程及对岩溶碳汇效应的影响机制”(编号: 2018GXNSFDA281036);中国地质调查局地质调查项目“桂江—柳江流域水文地质调查”(编号: 20190343) |
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| Buffering Effect of Lime Soil on Acid Rain and Its Influence on the Evaluation of the Karst Carbon Sink Effect |
| Recent study results have shown that exogenous acids (e.g., sulfuric and nitric acid) are increasingly involved in carbonate dissolution. However, the relationship between the role of acid rain in carbonate dissolution and carbon cycle is not clear, which seriously restricts the accurate evaluation of karst carbon sink effect in China. In this study, the soil water of different geomorphic parts and that after rainfall in wet season (April) and normal season (September) were sampled and tested in the Yaji Karst Spring field research and experimental site with high acid rain intensity, high frequency, and typical karst development. The results showed that the pH range of the soil was 5.55–7.81, with an average of 6.76±61. The coefficient of variation was 9.11% and the pH range of the soil water was 6.69–7.89. The average value was 7.21±31, and the coefficient of variation was 4.43%, with both of them close to neutral and above neutral; this showed a trend of increase with an increase in depth. Soil pH is mainly controlled by the decomposition of soil organic matter to produce acid. Soil water pH is mainly affected by the geochemical background of calcareous soil rich in calcium and alkaline; therefore, acid rain has little effect on both. The range of soil cation exchange capacity was 302–423 mmol (+) / kg, which was in the range for soil insensitive to acid deposition, indicating that the soil had a good buffer capacity for H+ from acid rain. The proportion of alkaline ions (Ca2+ + Mg2+) in soil water ranged from 23.66% to 25.0%, with an average of 24.25% ±0.33%, and the coefficient of variation was 1.36%, which indicated that the content was stable. The proportion of acid ions (SO2– 4+NO– 3) ranged from 2.47% to 18.94%, with an average of 7.69%±5.09%, and the coefficient of variation was 66.28%, which indicated that the content changed greatly. The proportion of acid ions decreased with an increase in soil water circulation depth and path, indicating that acid ions are buffered in the soil layer and indicates that H+ from acid rain will not have a sink reducing effect on carbonate rock dissolution in the lower karst aquifer after being buffered by the lime soil layer. In a previous study, because the buffering effect of lime soil layer on acid rain was not considered, Ca2+ and Mg2+ in groundwater in equilibrium with SO2– 4 and NO– 3 were attributed to carbonate rock dissolved by sulfuric acid and nitric acid in acid rain; therefore, the calculation results obviously overestimated the sink reduction effect of acid rain. |
| HUANG Qi-bo,WU Hua-ying,CHENG Rui-rui,LI Teng-fang,LUO Fei,ZHAO Guang-shuai,LI Xiao-pan.2022.Buffering Effect of Lime Soil on Acid Rain and Its Influence on the Evaluation of the Karst Carbon Sink Effect[J].Acta Geoscientica Sinica,43(4):461-471. |
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