Environmental Engineering Reference
In-Depth Information
originate mainly from the geological context of Nantes area. As conductivity and
concentrations of Ca, Na, Mg and K were well correlated, the elements could be
present mostly as dissolved species in runoff waters.
Distribution of Metals Among Particulate, Colloidal
and Dissolved Fractions
The partitioning of major chemical elements between particulate and dissolved
fractions, according to conventional 0.45-mm pore size filtration, indicated that Fe
and Al were predominantly associated (>80%) with particles greater than 0.45 mm
(Fig.
1
). Mn was equally distributed in both the dissolved and particulate fractions.
Si and organic carbon were mostly in the <0.45 µm size fraction (80%). The trends
were observed whatever the seasons as indicated by the low standard deviation of
the partitioning for these major elements (35-20%). Ca, Na, Mg and K were pre-
dominantly dissolved in runoff waters. All the trace metals were mostly in the
>0.45 mm fraction: from 50% (Ni) to 90% (Pb). The variability of the distribution
for trace metals was high (SD 20-30%), except for lead (SD 9%). Correlation coef-
ficients between particulate concentrations of heavy metals and Fe, Al, Mn-particle
associated showed the affinity of all the trace metals, except Pb, for Fe, Al,
Mn-bearing phases. Coefficients varied between 0.78 and 0.97 for Cd, Cr, Cu and
Ni in increasing order of correlation whereas lower correlation for Zn was noticed
(r
2
= 0.74 ± 0.04). Moreover, high correlations between particulate Cu and Ni and
particulate Si (r
2
= 0.8) were found. With the exception of a moderate correlation
Fig. 1
Partitioning of chemical elements between particulate and dissolved fractions (cut-off 0.45
mm) - Mean values of 17 rain events
