pH和磷的交互作用对稳定化土壤砷释放的影响

以3种含Fe材料稳定化土壤(FeSO_4、FeS和Fe~0稳定化土壤)为研究对象,研究了不同pH和P的交互作用对As释放量的影响及其作用机理。结果表明,在pH=3条件下,随着时间的延长能够促进释放的As重新趋于稳定化,而pH=11时3种稳定化土壤中As的释放量显著增加,144 h后分别约为pH=3时的10.5、16和10倍。添加P时,在3种pH条件下都促进了稳定化土壤中As的释放,尤其在酸性条件下,相对于无P体系As的释放量增加最为明显。FeSO_4稳定化土壤中As的释放特征能用Elovich方程较好地描述,而双常数方程拟合FeS和Fe~0稳定化土壤效果更优。在pH=3条件下,3种稳定化土壤中As的释放量与Ca、Mg、Mn的溶出量呈(极)显著相关,而pH=11时FeSO_4和FeS稳定化土壤中As的释放量与SO_4~(2–)的溶出量呈(极)显著相关,表明在酸性条件下,稳定化土壤As的释放主要受Ca、Mg、Mn氧化物结合态As溶解的影响,而碱性条件下,FeSO_4和FeS稳定化土壤中As的释放可能与硫化物的溶解有关。

Interaction Effect of pH and Phosphorus on Arsenic Release from Stabilized Soil

Soils stablished by FeSO₄, FeS and Fe⁰ were chosen to study the interaction effect of pH and phosphorus on arsenic release and the mechanisms involved. The results showed that the released arsenic tended to stabilize again over time at pH 3.0, whereas increased dramatically at pH 11.0, reached 10.5, 10 and 16 times of those at pH 3.0 in 144 h, respectively. Phosphorus addition promoted arsenic release from stabilized soils, especially under acidic condition. Elovich equation could describe better arsenic release from FeSO₄ stabilized soil, while power function equation fitted better from FeS and Fe⁰ stabilized soils. Arsenic release was significantly correlated with dissolved Ca, Mg and Mn from soils at pH 3.0 and with SO₄^2- released from FeSO₄ and FeS stabilized soils at pH 11.0, which imply that arsenic release from stabilized soil is influenced mainly by dissolution of arsenic binded in Ca, Mg and Mn oxides under acidic conditions, while might relate with dissolution of sulfides in FeSO₄ and FeS stabilized soils under alkaline conditions.