Potential for microbially mediated redox transformations and mobilization of arsenic in uncontaminated soils.
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.
Yamamura
Shigeki
S
National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan. yshige@nies.go.jp
Watanabe
Mirai
M
Yamamoto
Norio
N
Sei
Kazunari
K
Ike
Michihiko
M
D001151:Arsenic / Q000737:chemistry / Q000378:metabolism*; D001673:Biodegradation, Environmental; D007501:Iron / Q000737:chemistry; D010084:Oxidation-Reduction; D012987:Soil; D012988:Soil Microbiology
D012987:Soil; D007501:Iron; D001151:Arsenic