Effect of land developmental process on soil solution chemistry in acid sulfate soils distributed in the Mekong Delta, Vietnam
Effect of land developmental process on soil solution chemistry in acid sulfate soils distributed in the Mekong Delta, Vietnam
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DOI：
10.1111/j.1747-0765.2008.00256.x
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发表时间：
2008-06-01
影响因子：
2
通讯作者：
Sumida, Hiroaki
中科院分区：
文献类型：
--
作者：
Kawahigashi, Masayuki;Do, Nhut Minh;Sumida, Hiroaki
酸性硫酸盐土壤中的水溶性离子物质可能是作物生产的强有力控制因素，并对水生生态系统产生影响。特别是在干旱季节，土壤表面的氧化和酸化可能会产生大量的酸和可溶性金属。为了估计酸性硫酸盐土壤对水环境的酸和金属负荷，我们测定了越南湄公河三角洲土壤中水溶性离子的组成。在旱季结束时，土壤从每个土壤层在两个土壤剖面上的三角洲不同的土地开发过程。水溶性离子提取使用蒸馏水和人工合成的灌溉水（pH 6.3）调整到相同的离子强度和pH值的字段运河水。两种萃取剂中萃取的碱性阳离子之间的关系显示出高度的线性相关性，表明两种萃取剂之间具有相似的萃取机理。人工灌溉水中较高的离子强度可能对离子交换提取没有任何优势，因此，提取物的性质可能取决于土壤性质。年龄越大的土壤母质，可溶性铝和铁的比率和较低的pH值。渐进风化的土壤上的老三角洲已经排出了更大量的碱，可能是为了补偿酸，土壤已经开始释放交换铝吸附到负电荷的胶体和铁从分解的氧化物。老三角洲的土壤剖面释放相对较高浓度的铝与较低含量的盐基阳离子，其中年平均水稻产量的一半，另一个网站。可溶性金属和酸在这两个网站上出现的低渗透层，这可能是广泛分布在湄公河三角洲的上层积累。
Water-soluble ionic substances in acid sulfate soils are likely to be strong controls for crop production and to have impacts on aquatic ecosystems. In dry seasons, in particular, oxidation of the soil surface followed by acidification probably produces lots of acids and soluble metals. To estimate acid and metal loads from acid sulfate soils to aquatic environments, we determined the composition of water-soluble ions from soils distributed in the Mekong Delta, Vietnam. At the end of the dry season, soils were taken from each soil horizon in two soil profiles on the delta under different land developmental processes. Water-soluble ions were extracted using both distilled water and artificially synthesized irrigation water (pH 6.3) adjusted to the same ionic strength and pH as the field canal water. The relationship between extracted basic cations in both extracts showed high linear correlation, indicating a similar extraction mechanism between both extractants. Higher ionic strength in the artificial irrigation water may not have any advantages for extraction by ion exchange and, thus, properties of extracts are likely to depend on the soil properties. The older the soil parent material, the larger the rates of soluble Al and Fe and the lower the pH. Progressive weathering of the soil on the older delta has already discharged greater amounts of bases, probably for compensation of acids, and the soil has started to release exchangeable Al sorbed onto negative-charge colloids and Fe from decomposed oxides. The soil profile of the older delta released relatively greater concentrations of Al with a lower content of base cations, where the annual averaged rice yield was half that of another site. Soluble metals and acids at both sites appear to accumulate in the upper horizons above the low permeable layer, which is probably widely distributed in the Mekong Delta.