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将水稻土中的亚铁区分为水溶态、代换态、络合态和沉淀态,研究了各种形态亚铁之间的平衡关系及其影响因素。在不加易分解的有机质的一般水稻土中,水溶态亚铁和代换态亚铁的数量都很小,分别占亚铁总量的1%以下和0.5—1.5%;在加入易分解的有机质后,两者的数量急剧增加,均可达到亚铁总量的20%以上。络合态亚铁的变化幅度较小,约占亚铁总量的16—36%。代换态亚铁量受到土壤的阳离子代换量、硫化物量和pH的影响。一般pH愈低,代换态亚铁量愈多;但在低于pH4时,数量又降低。在某些条件下,代换态亚铁可达每百克土中2—3毫当量。土壤对亚铁的吸附可以引起等当量的钙离子的释出。水溶态亚铁量与pH密切相关。在pH5—5.5以上时,每改变一个pH单位使pFe~(++)改变0.7—0.9个单位;在pH较低时,pH-pFe~(++)相关线的斜率较小。实测pH-pFe~(++)线的位置介于FeS和Fe(OH)_2的理论线之间。各种形态亚铁之间的转化速度相当快,一般在四小时内即达平衡。
Ferrous iron in paddy soil is divided into water-soluble, substitutional, complexation and sedimentation states, the equilibrium relationship between various forms of ferrous and its influencing factors were studied. The amount of water-soluble ferrous and substituting ferrous is very small, accounting for less than 1% and 0.5-1.5% respectively of the total amount of ferrous iron in the non-decomposed organic matter-rich general paddy soil. After the organic matter, the sharp increase in the number of both can reach more than 20% of the total ferrous. Ferrous complex ferrous changes in the smaller, accounting for about 16-36% of the total ferrous. Substituted ferrous amounts are affected by soil cation exchange capacity, sulfide content and pH. The lower the general pH, the more substitutional ferrous; but below pH4, the number is reduced. Under some conditions, substitution ferrous can reach 2-3 milliequivalents per 100 grams of soil. Soil adsorption of ferrous iron can cause the equivalent release of calcium ions. The amount of water-soluble ferrous is closely related to pH. At pH5-5.5 and above, pH = pFe ~ (++) changes by 0.7-0.9 units for each pH unit change; at lower pH, the slope of pH-pFe ~ (++) correlation line is smaller. The measured pH-pFe ~ (++) line is located between the theoretical lines of FeS and Fe (OH) _2. The rate of conversion between various forms of ferrous is quite fast, usually within four hours to reach a balance.