施用牛粪对As污染稻田水稻As吸收的影响

Effect of Application of Cattle Manure on Arsenic Uptake by Rice in Arsenic-contaminated Paddy Fields

为探究牛粪施肥对污染稻田水稻As吸收的影响,采用盆栽培养试验研究了施加牛粪对土壤Fe和As的活性、水稻根表铁膜形成及籽粒As含量的影响。实验所用受高As矿山废水污染土壤(As:92.3 mg/kg)施加10%~30%的牛粪,土壤溶解性有机碳含量增加8.41~24.5 mg/kg,土壤孔隙水pH提高0.14~0.59,土壤氧化还原电位降低93.5~174 m V,与背景土(As:18.1 mg/kg)变化趋势相同;施用牛粪还会活化土壤中的Fe和As,污染土壤Fe(II)、AO-Fe和HCl-As含量分别增加13.5%~149%、35.9%~90.9%和70.1%~181%,分别为背景土壤的0.86~1.66倍、1.17~2.15倍、4.29~8.91倍;施加牛粪能促进根表铁膜的形成,拔节期污染土壤和背景土壤水稻根表Fe分别是其对照的1.56~1.96倍和2.09~3.07倍,根表吸附As含量是其对照的3.04~5.18、3.82~4.08倍,根表附着Fe随牛粪的增加先增加后降低,至成熟期污染土壤水稻根表吸附Fe和As分别是背景土壤的1.35~2.91和8.45~16.6倍,根表As和Fe的物质量比为污染区(3.49×10^-3~3.55×10^-3)>背景区(4.41×10-4~6.17×10-4);背景土壤施加牛粪后水稻籽粒As含量降低,最大降低36.4%,而污染土壤水稻籽粒As含量增加,最大增加127%。牛粪对土壤As、Fe的活性及根表铁膜的形成都具有重要影响,会提高污染稻田籽粒中As的含量,含As矿山废水污染稻田应当谨慎施用牛粪。

The study was designed to explore the influences of cattle manure on arsenic uptake by rice grain.The pot experiments were conducted to investigate effects of cattle manure on activities of arsenic and iron in soils,formation of iron plaque on the rice root surface and arsenic contents in rice grains.When the amount of cattle manure added to polluted soils and background soils increased,the DOC contents and pore water p H of soils increased,while Eh of soils decreased.The addition of cattle manure could activate iron and arsenic in soils.The contents of Fe(II),AO-Fe and HCl-As in polluted soils increased by 13.5%-149%、35.9%-90.9%and 70.1%-181%,respectively,which were 0.86-1.66,1.17-2.15 and 4.29-8.91 times higher than those of background soils.The application of cattle manure could also promote the formation of iron plaque on the root surface.The iron contents on the root surface were 1.56-1.96 times higher for polluted soils and 2.09-3.07 times higher for background soil compared to their control experiments during the jointing stage.The contents of adsorbed As in polluted soils and background soils were 3.04-5.18 times and 3.82-4.08 times,respectively,higher than their controls.The iron contents on the root surface increased first and then decreased when the amount of cow manure adding kept increasing.Iron and arsenic adsorbed on the root surface in polluted soils were 1.35-2.91 times and 8.45-16.6 times,respectively,higher than those in background soils at the maturity stage.The molar ratio of arsenic and iron on the rice root surface in polluted soils ranged from 3.49×10^-3 to 3.55×10^-3,while ranged from 4.41×10-4 to 6.17×10-4 in background soils.The arsenic contents in rice grains from background soil experiments decreased about 36.4%,but the arsenic contents in rice grains from polluted soil experiments increased about 127%after adding cattle manure.The results suggested that adding cattle manure has significant effects on activities of arsenic and iron in soils,formation of iron plaque on the rice root surface,and arsenic contents in rice grains.The cattle manure should be cautiously used as fertilization in paddy fields polluted by the mining drainage with the high content of arsenic.