The finer fractions are prevented from deposition in areas with
greater water circulation. This distribution is linked to the selection
that is generated by tidal currents near the bottom
(Quaresma et al., 2000).
The rivers of the Canal do Cunha basin are categorized as class 3
(CONAMA, 2005), and the surface of the water is polluted by oil
and garbage. The tidal movements in this area demonstrate minimal
influence due to the intense sedimentation that reduced the
width and depth of the channels. Guanabara Bay is classified as saline
water class 3 (COMANA, 2005), which is intended solely for
navigation.
The distribution of heavy metal concentrations in the water and
sediments during the rainy and dry seasons was separately evaluated
for each metal.
The collection points CN100 and GN% contained the highest
concentrations of Pb and Zn, respectively, in the water. The concentrations
of other metals are lower than the concentrations of Zn
and Pb. Fig. 6 displays the concentration of Pb in the water and
sediment.