Unlike the other metals studied, considerable Mn was found in all of the four fractions; this trend has been noted by other researchers (Usero et al., 1998; Ngaim and Lim, 2001). Mn was primarily found in the acid soluble fraction (32.8% for October 2009 and 25.6% for June 2010), with lower amounts in the reducible (28.8%) and oxidizable (10.8%) fractions. Fractionation results suggest that an appreciable proportion of Mn may be remobilized and made readily available following a slight lowering of pH (Tessier et al., 1979; Thomas et al., 1994).