Yamamura Shigeki, Watanabe Mirai, Yamamoto Norio, Sei Kazunari, Ike Michihiko
National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
Chemosphere. 2009 Sep;77(2):169-74. doi: 10.1016/j.chemosphere.2009.07.071. Epub 2009 Aug 28.
Surface soil samples, which had no significant As contamination, were examined for As(V) reduction, As(III) oxidation and As mobilization capability. All five soil samples tested exhibited microbial As(V)-reducing activities both in aerobic and anaerobic conditions. Under aerobic conditions when As(V) reduction had almost ceased, oxidation of As(III) to As(V) occurred, whereas only As(V) reduction was observed under anaerobic conditions. In cultures incubated with As(III), As(III) was oxidized by indigenous soil microbes only under aerobic conditions. These results indicate that microbial redox transformations of As are ubiquitous in the natural environment regardless of background As levels. Mobilization through microbially mediated As(V) and Fe(III) reduction occurred both in the presence and absence of oxygen. Significant variation in dissolved As occurred depending on the Fe contents of soils, and re-immobilization of As arose in the presence of oxygen, presumably as a consequence of dissolved As(III) and Fe(II) oxidation. There was no apparent correlation between dissolved Fe(II) and As, suggesting that reductive dissolution of Fe(III) minerals does not necessarily determine the extent of As release from soils.
对没有明显砷污染的表层土壤样本进行了五价砷还原、三价砷氧化和砷迁移能力的检测。所测试的全部五个土壤样本在有氧和无氧条件下均表现出微生物五价砷还原活性。在有氧条件下，当五价砷还原几乎停止时，三价砷会氧化为五价砷，而在无氧条件下仅观察到五价砷还原。在用三价砷培养的培养物中，只有在有氧条件下，三价砷才会被土壤中的原生微生物氧化。这些结果表明，无论背景砷含量如何，砷的微生物氧化还原转化在自然环境中普遍存在。通过微生物介导的五价砷和三价铁还原实现的迁移在有氧和无氧条件下均会发生。溶解态砷的显著变化取决于土壤中的铁含量，并且在有氧条件下会出现砷的再固定，这可能是溶解态三价砷和二价铁氧化的结果。溶解态二价铁和砷之间没有明显的相关性, 这表明三价铁矿物的还原溶解不一定决定土壤中砷的释放程度。
