引用本文:刘 莉,谢德体,李忠意,刘 芳.酸性紫色土的阳离子交换特征及其对酸缓冲容量的影响[J].土壤学报,2020,57(4):887-897. DOI:10.11766/trxb201905050146
LIU Li,XIE Deti,LI Zhongyi,LIU Fang.Cations Exchange and Its Effect on Acid Buffering Capacity of Acid Purple Soil[J].Acta Pedologica Sinica,2020,57(4):887-897. DOI:10.11766/trxb201905050146
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酸性紫色土的阳离子交换特征及其对酸缓冲容量的影响
刘 莉1, 谢德体1, 李忠意1, 刘 芳2
1.西南大学资源环境学院;2.重庆市涪陵区农业委员会
摘要:
明确酸性紫色土的交换性阳离子组成特征及其对土壤后续酸化进程的影响有助于评估紫色土的潜在酸化风险。为此,在重庆市合川区采集了38个酸性紫色土,进行了理化性质分析与酸缓冲容量测定,探讨了阳离子交换特征对土壤酸缓冲容量的影响。结果表明:部分紫色土的酸化程度较为严重,但酸性紫色土仍具有较高的交换性盐基阳离子含量和阳离子交换量(CEC)。紫色土的交换性Ca2+和交换性Mg2+含量分别为红壤的5.9倍和3.9倍。紫色土CEC也显著高于红壤和砖红壤。丰富的黏土矿物组成,尤其是较高的蒙脱石含量,是紫色土具有较高盐基阳离子含量和高CEC的主要原因。酸性紫色土的酸缓冲容量大小为3.18~25.6 mmol·kg-1·pH-1。酸缓冲容量与交换性盐基总量和CEC间均呈极显著的正相关性。较高的盐基阳离子含量和CEC有助于增加紫色土的酸缓冲容量,减缓土壤的酸化速度。因此,尽管部分紫色土酸化较为严重,但受成土母质和发育程度的影响,丰富的盐基阳离子含量能对进入土壤中的酸进行缓冲,减缓紫色土酸化速度。这是紫色土相对于其他地带性酸性土壤所具有的独特酸化特征。
关键词:  酸性紫色土  酸缓冲容量  交换性盐基离子  表面负电荷  黏土矿物
基金项目:国家自然科学基金项目(41701256)、重庆市博士后项目(Xm2016076)和中央高校基本业务费专项(XDJK2019B036)资助
Cations Exchange and Its Effect on Acid Buffering Capacity of Acid Purple Soil
LIU Li1, XIE Deti1, LI Zhongyi1, LIU Fang2
1.College of Resources and Environments, Southwest University;2.Chongqing Fuling Agricultural Committee
Abstract:
【Objective】Purple soil is a key soil resource for development of the agriculture Southwest China. A proportion of the purple soil has been somewhat acidified. A better understanding of the composition of exchangeable cations in acid purple soil and its influence on subsequent acidification processes of the soil is conducive to potential acidification risk assessment of the soil. 【Method】In this study, a total of 38 acid purple soil samples were collected from Hechuan District, Chongqing Municipality for analysis of physico-chemical properties and determination of acid buffering capacity. Acidification degree of the purple soil samples was evaluated based on their respective pH values and content of exchangeable acidity. Comparison between the samples of purple soils and some zonal soils (Alfisol, Ultisol, and Oxisol) was performed in content of exchangeable bases and cation exchangeable capacity (CEC). And then, contributions of minerals to base cations and CEC were discussed in detail. In the end, effects of exchangeable cations on acid buffering capacity of the purple soils were analyzed.【Result】Some of the soil samples, about 65%, show that the purple soil was acidified seriously with soil pH being < 5.5. Fortunately, the portion of acidified purple soil was still quite high in content of exchangeable base cations and cation exchange capacity (CEC), with Ca2+ being the highest in content ((13.3±5.27) cmol·kg-1), and K+, Na2+ and Mg2+ being (0.267±0.190), (0.196±0.116), and (3.91±1.15) cmol·kg-1, respectively. The average content of exchangeable base cations was 11.8 times as high as the content of exchangeable acidity, even though the highest content of soil exchangeable acidity in the purple soil reached up to 6.40 cmol·kg-1. Compared to the acid soils developed in the subtropical and tropical regions of China, the acid purple soil was significantly higher in CEC than Untisol and Oxisol. The content of exchangeable Ca2+ and Mg2+ in the purple soil was 5.9 and 3.9 times as high as that in Ultisol. In terms of soil minerals, the purple soil was dominated with quartz, mica, K-feldspar, albite, montmorillonite, illite, kaolinite and hematite. The abundant clay minerals, especially montmorillonite, increased the amount of surface negative charge of the purple soil and, correspondingly, enhanced adsorptive ability of the purple soil for base cations. And intensified weathering of the soil replenished the soil with base cations, thus stabilizing soil pH. Further analyze of content of organic matter in the purple soil shows that the purple soil was much lower than Alfisol, Ultisol, and Oxisol in content of organic matter. As a consequence, the minerals in the soil were the main contributors of surface charges in the purple soil. Acid buffering capacity of the purple soil varied in the range of 3.18- 25.6 mmol·kg-1·pH-1, and was significantly and positively related to exchangeable bases and CEC in the soil, which means a high content of base cations and CEC helps enhance soil acid buffering capacity, thus retarding acidification of the purple soil.【Conclusion】Though the purple soil in some areas is quite serious in acidification, as affected by its soil forming parent materials and weathering degree of the soil, the soil has an abundance of base cations, which help retard the process of soil acidification. These are the characteristics of soil acidification of the purple soil relative to the acid soils in other areas.
Key words:  Acid purple soil  Acid buffering capacity  Exchangeable base cations  Negative surface charge  Clay mineral