Fig. 4 shows Hg and LOI values in the non-burnt soils (E-NBE) and burnt soils and ashes of Ermida after the rainfall event (ARF). Burnt eucalypt soils contained significantly lower Hg concentrations (62–67 ng g− 1) than the corresponding non-burnt soils (86 ng g− 1). In opposition, burnt soils showed significantly higher LOI (23–26 %) than the non-burnt soils (16 %), with the exception of E-BE3. A lack of correlation (r = − 0.206, p = 0.378) was observed between Hg and LOI levels. The CD 3254 did not reduce the differences of Hg concentrations between eucalypt and pine areas that were observed immediately after fire ( Fig. 2 and Fig. 4). In fact, eucalypt soils exhibited significantly (p < 0.05) higher levels of Hg than those in pine plantations. In general, cristae differences were also noticeable in ashes. Levels of LOI in soils differed among the slopes, either between the distinct eucalypt slopes or between the pine slopes. For example, LOI values in the eucalypt slopes (E-BE1, E-BE2 and E-BE3) were significantly (p < 0.05) different between the three, while the pine slope E-BP2 was significantly (p < 0.05) lower than from E-BP1 and E-BP3. Poor correlation was observed between Hg and LOI values in soils and ashes (r = 0.434, p = 0.02) and a moderate correlation in ashes (r = 0.709, p = 0.01).