引用本文:赵 越,杨金玲,董 岳,吴华勇,张甘霖.模拟酸雨淋溶下强风化土壤矿物风化计量关系研究[J].土壤学报,2019,56(2):310-319.
ZHAO Yue,YANG JinLing,DONG Yue,WU HuaYong,ZHANG GanLin.Stoichiometry of Soil Mineral Weathering in Intensely Weathered Soil as Leached by Simulated Acid Rain[J].Acta Pedologica Sinica,2019,56(2):310-319
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模拟酸雨淋溶下强风化土壤矿物风化计量关系研究
赵 越,杨金玲,董 岳,吴华勇,张甘霖
土壤与农业可持续发展国家重点实验室(中国科学院南京土壤研究所)
摘要:
矿物风化计量关系对于定量土壤酸化速率至关重要。我国亚热带地区矿物风化强烈,土壤的酸敏感性高。为获取强风化土壤在矿物风化过程中元素释放特征及其化学计量关系,选取花岗岩发育的富铁土,先用EDTA-乙酸铵溶液洗脱土壤胶体上吸附的盐基离子,然后采用改进的Batch法,将洗脱盐基土壤与未洗脱盐基土壤同时进行模拟酸雨淋溶。结果表明:(1)洗脱盐基土壤与未洗脱盐基土壤的盐基离子(K+、Na+、Ca2+和Mg2+ )释放情况存在显著差异,洗脱盐基后土壤在淋溶中释放的盐基来源为矿物风化,释放缓慢而平稳;(2)未洗脱盐基土壤在淋溶初期,盐基的释放量较大,随着淋溶的进行,释放量迅速下降,淋溶后期的释放速率与洗脱盐基土壤接近,这说明未洗脱盐基土壤在淋溶初期释放的盐基主要来源于阳离子交换过程,后期则主要来源于风化过程;(3)洗脱盐基土壤和未洗脱盐基土壤经酸雨淋溶释放的各盐基化学计量关系(K+:Na+:Ca2+:Mg2+)以及盐基离子与硅的化学计量关系(BC:Si)差异较大,由于未洗脱盐基土壤受到阳离子交换的影响,因此只有洗脱盐基土壤的矿物风化计量关系可以作为定量估算土壤酸化速率的依据。
关键词:  计量关系  矿物风化  土壤酸化  土壤发生  土壤演变  土壤地球化学
DOI:10.11766/trxb201806080217
分类号:
基金项目:国家自然科学基金项目(41877010、41471176、41571130051)和公安部物证鉴定中心协同创新工作项目(2016XTCX03)
Stoichiometry of Soil Mineral Weathering in Intensely Weathered Soil as Leached by Simulated Acid Rain
ZHAO Yue1, YANG JinLing2, DONG Yue2, WU HuaYong2, ZHANG GanLin2
1.State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences;2.Institute of Soil Science, Chinese Academy of Sciences
Abstract:
【Objective】As the problem of soil acidification is becoming increasingly serious, the research of soil acidification rate appears to be of critical importance, especially on stoichiometry of mineral weathering, which plays an important role in quantifying soil acidification rate. The soils undergone intensive weathering in the subtropical region of China are highly acid-sensitive. In recent years, acid deposition has become very serious, making the problem of soil acidification prominent. Therefore, in this research, a leaching experiment with simulated acid rain was conducted to explore stoichiometric relationship between released elements during the weathering process of minerals in intensively weathered soil derived from granite in the subtropical region, in an attempt to provide a certain basis for quantitative estimation of soil acidification rate.【Method】First of all, soil samples were collected. The soil derived from granite in the subtropical region. Some of the samples were treated with EDTA-ammonium acetate solution to elute base cations adsorbed on soil colloids, which can avoid the effect of cation exchange reaction in subsequent processes of the experiment. Then the two groups of soil samples, eluted and uneluted, were leached with simulated acid rain at the same time by modified Batch. The leachates were collected for analysis of K+, Na+, Ca2+, Mg2+ and Si.【Result】(1) During the eluting process, the amount of K+, Na+, Ca2+ and Mg2+ eluted from the samples was related to the contents of exchangeable base in the soil. For highly weathered ferrisol, eight rounds of elution processes were performed to elute all the exchangeable base cations from soil colloids; (2) In the leaching process with simulated acid rain, the amount of released base cations from the eluted samples were low and stable while that from the uneluted samples varied sharply from the initial stage. A quite large amount of base cations were released at the initial stage of the leaching and did at a rapidly reducing rate with the leaching till they got quite close to the eluted samples in base leaching rate. This result indicates that the base cations released at the initial stage of leaching for uneluted-base soil came mainly from cation exchange reaction, while those released at the later stage originated from mineral weathering; and (3) During the leaching process by simulated acid rain, weathering of polyminerals in the soil mainly were feldspar, hydromica and vermiculite with releasing base cations. Based on the released amounts of base cations and Si, the stoichiometric relationships of K+:Na+:Ca2+:Mg2+ and base cation and Si (BC:Si) in horizons A, B1 and B2 of the eluted and uneluted soils were obtained. The BC:Si of the eluted soil was 0.8~1.4:1 and of the uneluted soil was 3.4~4.0:1. The sharply difference between them indicates the importance of eluted soil exchangeable base cations for accurate stoichiometric relationships of mineral weathering.【Conclusion】(1) During the base eluting process, the base cations eluted from the soil come mainly from the exchangeable base cations. Eight rounds of elution can elute this portion of base cations completely for the highly weathered soil; (2) During the process of leaching with simulated acid rain, the eluted and uneluted soils differ sharply in released amount and pattern of base cations because the base cations released come mainly from weathering of minerals for the eluted soil, while they include exchangeable base cations for uneluted soil; and (3) The main weathering polyminerals in the soils are hydrolysis of feldspar, hydromica and vermiculite as triggered by acid rain. The stoichiometric relationship of BC:Si of the eluted soil is 0.8~1.4:1 while that of the uneluted soil is 3.4~4.0:1. The sharply difference means that to achieve accurate stoichiometry of mineral weathering, it is essential to elute exchangeable base cations adsorbed on soil colloids.
Key words:  Stoichiometry  Minerals weathering  Soil acidification  Soil genesis  Soil evolution  Soil geochemistry