Arsenic biomineralization by iron oxidizing strain (Ochrobactrum sp.) isolated from a paddy soil in Hunan, China

The biogeochemistry of iron (Fe) could affect arsenic (As) fate and change its availability. Fe(II) oxidation mediated by Fe oxidizing bacteria (FeOB) has the potential for As contamination remediation due to the formation of biogenic minerals. However, microbial Fe(II) oxidation coupled with the immobilization of As and the effect of FeOB on As remediation in soils has not been thoroughly investigated. In this study, a FeOB was isolated from a paddy soil and identified as Ochrobactrum sp. EEELCW01. The kinetics reactions were used to investigate how biological and chemical reactions were involved in the Fe(II)-NO3--FeOB system. Microbial Fe(II) oxidation coupled As mineralization, as well as its application in As contaminated paddy soils was studied. The results suggested that biological pathway contributed to the Fe(II) oxidation and NO3- reduction in the whole process, in which the chemical Fe(II) oxidation by biogenic NO2- was involved. Meanwhile, Fe(II) facilitated the reduction of NO2- while inhibited the reduction of NO3-. Adding 2% or more bacteria led to a significant removal effect for aqueous As, resulting in the formation of lepidocrocite and two As-containing minerals (angelellite, loellingite). With the simultaneous application of FeOB and NO3-, the available As content in soils decreased by 37.6% and stabilized at 0.80 mg kg(-1) finally. In addition, the immobilization showed long-term effect compared to the treatment with Fe(II) or NO3- alone. The study proved that the isolated FeOB had a significant ability for As mineralization and immobilization, which provided theoretical and application basis for the remediation of As contaminated soils.

Automated summary

The study demonstrated that Fe oxidizing bacteria (FeOB) have the ability to enhance arsenic (As) immobilization and mineralization in soil, leading to a decrease in available As content. Additionally, Fe(II) facilitated the reduction of NO3- while inhibiting the reduction of NO2-. The addition of 2% or more bacteria significantly reduced aqueous As content and resulted in the formation of As-containing minerals (angelellite, loellingite).