3. Results and discussion
The effects of metal concentrations on biota in P. australisassociated
sediments were compared to guidelines of MacDonald
et al. [21] and Persaud et al. [22] (Table 2). According
to their classifications, metal concentrations over the probable
effect concentration (PEC) on the biota are labeled as toxic.
The concentration of arsenic was over the PEC in all sites
within the industrial area (Table 2). Cadmium and lead were
similarly high in the three industrial sites (ZY23, ZY24 and
ZY25). The results of ZY23 showed high levels of mercury,
copper and zinc. In ZY25, zinc was found to be over the PEC
threshold, while in ZY24, nickel was over the PEC. These
concentrations of metals are mainly caused by discharge into
canals of industrial byproducts via coal combustion for energy
production as well as residuals from metallurgical industries
and chemical plants. The urban area was characterized by a
concentration of mercury (except for ZY36 and ZY38), nickel
in ZY36 and ZY38 and chromium in ZY36 due to vehicle
exhaust particles and combustion of civil wastes [23,24].
Nutrients were present in both urban and industrial areas; in
particular, the nitrogen concentration turned out to be high in
and around the urban area, due to civil wastewater being