| 硫素对氧化还原条件下水稻土氧化铁和砷形态影响 |
| 摘要点击 3000 全文点击 1314 投稿时间：2014-03-04 修订日期：2014-04-15 |
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| 中文关键词 硫素 氧化还原 水稻土 土壤氧化铁形态 土壤砷形态 |
| 英文关键词 sulfur fertilizer redox condition paddy soil species of soil Fe/Mn species of soil arsenic |
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| 中文摘要 |
| 通过充N2和充O2的氧化还原反应装置，在添加外源砷污染的水稻土中，施用不同形态的无机硫（不施硫S0，单质硫S1和硫酸盐S2），模拟水稻田的氧化还原状况.结果表明，通N2时，土壤溶液氧化还原电位（Eh）在-100~-200 mV之间，溶液pH在7.0~8.0之间，pe+pH为4~7之间；通O2时，溶液Eh在200mV左右，溶液pH在6.5~7.5之间，pe+pH为9~12之间.无论通N2还是通O2，土壤溶出铁的浓度在1.2~1.6 mg ·L-1，均有处理S0>S1>S2和AsS0>AsS1>AsS2.在通N2时，各处理HCl提取土壤氧化铁的含量比原土[（21.4±0.3）g ·kg-1]低5 g ·kg-1，有利于结晶态氧化铁向无定形氧化铁转化和形成Fe2+，无定形氧化铁活化度比原土活化度46.8%有所增加，且处理AsS2（49.4%）1（60.0%）.在通O2时，溶液中的Fe2+和FeS被氧化成 Fe3+，Fe3+水解变成Fe（OH）3沉淀，提高了土壤酸溶性氧化铁和结晶态氧化铁的含量，各处理氧化铁活化度为AsS1（41.2%）>AsS2（36.1%）.通N2时，土壤溶液中砷浓度变化为AsS0[（1.13±0.04）mg ·L-1]>AsS1[（0.89±0.01）mg ·L-1]>AsS2[（0.77±0.04）mg ·L-1]；通O2时，土壤溶液中砷浓度变化AsS1[（0.77±0.01）mg ·L-1]>AsS0[（0.20±0.09）mg ·L-1]>AsS2[（0.09±0.01）mg ·L-1].通N2时，不同处理各形态砷占总砷比例变化为残渣态（34.9%~41.4%）≈ 专性吸附态（37.4%~39.5%）>晶态铁锰结合态（23.3%~25.6%）>非专性吸附态（2.4%~3.3%）>无定形铁锰结合态（0.5%~0.8%）.通O2时，各处理形态砷占总砷比例变化为残渣态（30.8%~39.3%）≈ 专性吸附态（30.3%~34.7%）>晶态铁锰结合态（26.0%~28.7%）>无定形铁锰结合态（9.3%~10.7%）>非专性吸附态（0.5%~1.6%），其中，无定形铁锰氧化物结合态砷比通N2时提高了约9%，也就是无定形铁锰的老化作用对砷形态转化的影响.这表明还原条件能够使氧化铁的活化度升高，砷的移动性增强，但硫酸盐体系降低氧化铁的活化度，单质硫体系的砷移动性要大于硫酸盐体系的砷移动性. |
| 英文摘要 |
| Redox conditions of the polluted paddy soil with exogenous As were simulated by redox reaction apparatus after flowing N2 and O2 applied with different forms of inorganic sulfur(CK-S0, elemental sulfur-S1 and sulfate-S2). Results showed that redox potential(Eh)was about -100--200 mV and the pH 7.0-8.0 and the pe+pH 4-7 in soil solution when flowed N2, and Eh about 200 mV and the pH 6.5-7.5 and pe+pH 9-12 when continuously flowed O2. Concentrations of the dissolved Fe in soil solution were in 1.2-1.6 mg ·L-1 either flowed N2 or O2, and the order of Fe concentrations was AsS0treatment>AsS1 treatment>AsS2 treatment. Amounts of soil Fe oxide by HCl extraction from different treatments were 5 g ·kg-1 lower than the original soil [(21.4±0.3)g ·kg-1] when flowed N2, and it was in favor of the transformation of crystal Fe into amorphous iron and Fe2+. Activity of Fe oxides from different treatments increased comparing to that of the original soil(46.8%), and the order of activity of Fe oxides was AsS2 treatment(49.4%)1 treatment(60%). Fe2+ in solution and FeS were oxidized into Fe3+, and hydrolysis of Fe3+ was produced into Fe(OH)3 precipitation when flowed O2. It increased the contents of acid-soluble and crystal Fe oxide, and the order of activity of Fe oxides was AsS1(41.2%)treatment>AsS2(36.1%)treatment. Concentrations of As in soil solution were in the order of AsS0[(1.13±0.04 )mg ·L-1]>AsS1[(0.89±0.01) mg ·L-1]>AsS2[(0.77±0.04 )mg ·L-1]when flowed N2 and was AsS1[(0.77±0.01 )mg ·L-1]>AsS0[(0.20±0.09 )mg ·L-1]>AsS2[(0.09±0.01) mg ·L-1]when flowedO2. The proportions of arsenic fractions followed the order of the residual phases(34.9%-41.4%)≈specifically-sorbed(37.4%-39.5%)>well-crystallized hydrous oxides of Fe/Mn(23.3%-25.6%)>non-specifically sorbed(2.4%-3.3%)>amorphous hydrous oxides of Fe/Mn(0.5%-0.8%)when flowed N2, and was the residual phases(30.8%-39.3%)≈specifically-sorbed(30.3%-34.7%)>well-crystallized hydrous oxides of Fe/Mn(26.0%-28.7%)>amorphous hydrous oxides of Fe/Mn(9.3%-10.7%)>non-specifically sorbed(0.5%-1.6%)when flowed O2.Arsenic from amorphous hydrous oxides of Fe/Mn raised about 9% by flowing O2 than by flowing N2. This could be the effect of the aging amorphous Fe/Mn on the transformation of As, and the increased activity of iron oxide under reducing conditions and enhanced mobility of Arsenic. Elemental surfer system could increase mobility of arsenic more than sulfate system which may decrease degree of activity of iron oxide. |
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