This powerpoint presentation begins by providing a brief overview of two sampling campaigns to evaluate lead
concentrations in Montreal's tap water. Study objectives included the following:
characterize the occurrence and source of
particulate lead in Montreal tap water;
stimulate lead particle detachment;
investigate the bioavailability of lead
particles;
analyze the composition of lead particles
and scales;
determine parameters affecting dissolved
and particulate lead concentrations; and,
compare random daytime (RDT) sampling vs
sampling with 30 minutes of stagnation. Materials and methods for the
sampling protocol included the following: 2007, 45 LSL houses, 3 samples each (plus 3 sub-samples
for determination of dissolved Pb); and, PSS, 9 LSL houses, 3 extra samples after 5
min (plus 3 sub-samples for determination of dissolved Pb). Materials and methods for
scale deposit analysis included the following: Tof-Sims and
Laser Raman Microscopy methods;
six Montreal lead pipes were
analyzed;
particle analysis - Tof-Sims (no
need for standards); and,
ten typical particles analyzed. Presentation conclusions: the impact of sampling approach on the detection of Pb particulates indicated that
sampling after stagnation is useful to identify the source;
however, if flushing is conducted prior to stagnation, it may
eliminate particles accumulated in LSL and premise plumbing;
random daytime sampling has been shown to estimate
exposure; however, it does not systematically eliminate the
occurrence of particles in the LSL and premise plumbing; it
may produce a better estimate of Pb particulate exposure;
creating hydraulic disturbances by varying flow rates
at the tap increases considerably the detachment of
particulate metals (as observed by van Den Hoven, 2006); creating hydraulic disturbances by varying flow rates
at the tap increases considerably the detachment of
particulate metals (as observed by van Den Hoven, 2006); two dominant sources of particulate lead were
premise plumbing corrosion in 1st liter (brass, solder), and
adsorption of lead from LSL on iron oxide particles
from the distribution system and other "foreign"
particles (Schock, 1989, Hulsmann, 1990), and more
corrosive conditions (Cl2, dissolved iron), mainly in
the 2nd liter and the liter after 5 min;
this hypothesis is confirmed by scale deposit and
particle analysis; and,
data analysis showed that lead spikes occurred
simultaneously with tin, copper or zinc spikes. Conclusion for Montreal:
presence of background particulate lead could be
associated with more corrosive conditions and the
presence of iron;
dissolved iron/higher Cl2 residuals;
adsorption of lead from LSL on iron or "foreign" particles
exists, and occurrence of low particulate Pb
concentrations (2L, 5min); and,
high particulate lead concentration occurs sporadically
due to corrosion and detachment of brass and solder. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.4 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 32 |
| Published : | 11/01/2008 |
