3.2. Concentration of heavy metals in the core sediment
The concentrations of heavy metals along the depth gradient
are shown in Fig. 4 . Linear regression analysis showed that the
concentrations of all heavy metals, except Mn, were signifi cantly
negatively correlated with depth (i.e. the deeper the sediment, the
lower the concentration of heavy metals). This indicated that
heavy metal pollution has been deteriorating at a relatively
constant rate from 1979 onwards.