Jiang J, Bauer I, Paul A, Kappler A. Arsenic redox changes by microbially and chemically formed semiquinone radicals and hydroquinones in a humic substance model quinone. Environ Sci Technol. 2009 May 15;43(10):3639–45. doi: 10.1021/es803112a. PMID: 19544866.