4. In alkaline (pH>7 ), suboxic (pe 2-7) soils, the important aqueous species of selenium are SeO42 and SeO32. Determine if SeO32 can be oxidized to SeO42 through reduction of MnO2 (s) for at pH7.6 (assuming that both SeO32 and MnO2 are present). Write both half reactions, give pe values at pH 7.6 and draw a pe-pH diagram for this system for pH014. Assume [SeO42]=[SeO32] and (Mn2+1=105M (20 pts)