黄棕壤土柱中铁和锰的淋溶淀积特征

Leaching and deposition characteristics of iron and manganese in yellow brown soil column

为了研究干湿交替下土壤中铁和锰的淋溶淀积特征,以亚热带的黄棕壤为土柱材料,用pH 3.5的0~0.08 mol/L的FeSO_(4)和MnCl_(2)单一或混合溶液(浓度比分别为4︰1、2︰1和1︰1)淋溶土柱40次(每次间隔7 d),分析淋出液的pH和铁锰含量、土壤中铁锰含量和钙镁含量的变化。结果显示,随着淋溶次数增加,铁锰淋溶处理的土柱淋出液的pH总体降低1.10~2.68,甚至低于淋溶液的pH值;淋出液中的铁含量要低于淋溶液中的,而淋溶7次之后淋出液中的锰含量则相反;淋溶第一阶段(20次)和第二阶段(40次)土壤中铁和锰的全量、铁的游离态和非晶质态的含量有所增加,铁锰浓度高的淋溶液淋溶后土壤中铁锰氧化物含量升高,游离铁含量最高为89.14 mg/g,游离锰含量最高为13.35 mg/g;干湿交替淋溶下铁氧化物比锰氧化物更易形成,铁氧化物含量在上层(5 cm)土壤中较高,锰氧化物含量在下层(25 cm)土壤中较高;淋溶后土壤中钙、镁含量分别降低0.45~4.89、8.68~14.45 g/kg。

The subtropical yellow brown soil column was leached with 0-0.08 mol/L of pH 3.5(molar concentration ratio of 4︰1,2︰1 and 1︰1)FeSO_(4) and MnCl_(2) single or mixed solution for 40 times(7 days inter⁃val each time)to study the leaching and deposition characteristics of iron and manganese in soil under alternat⁃ing dry and wet conditions.The content changes of pH,Fe and Mn of the leached solution,the content of Fe,Mn,Ca and Mg in the soil were analyzed.The results showed that the pH of leachate from soil column treated with Fe and Mn decreased by 1.10-2.68 with the increase of leaching times,even lower than that of leaching solution.The content of iron in the leachate was lower than that in the leaching solution,while the content of manganese in the leachate was opposite after 7 times of leaching.The total amount of Fe and Mn,the content of free and amorphous iron oxides in the soil increased at the first stage(20 times)and the second stage(40 times)of leaching.The content of iron and manganese oxides in the soil increased after leaching with high concentration of iron and manganese solution.The highest content of free iron and manganese oxide was 89.14 mg/g and 13.35 mg/g,respectively.Iron oxides were easier to form than manganese oxides under the alternate wetting and drying leaching conditions.The contents of iron oxides and manganese oxides were higher in the upper layer(5 cm)and the lower layer(25 cm),respectively.The content of Ca and Mg in soil after being leached decreased by 0.45-4.89 g/kg and 8.68-14.45 g/kg,respectively.