Analytical Results, Findings, and Recommendations
of the 1995 OMAFRA Sewage Biosolids Field Survey
Analytical Results
The pH, phosphorus and metal levels quoted in the following sections
are given in Tables 5, 6,
7, 8, and 9.
Soil analyses for pH and phosphorus levels were carried out on 252
transect samples, and analyses for 11 metal levels were also carried
out on a similar number of samples taken along the same transects.
pH Levels
Twenty-two of the 252 transect samples tested had a pH level lower
than the minimum permissible level of 6.0 as specified in the current
guidelines. Eight of those transect samples were taken in the treated
plots, 3 were taken in the non-treated plots, and 11 were taken in
the woodlots. Minimum pH level in the treated, non-treated, and woodlot
transect samples was 5.1, 5.4 and 5.3, respectively.
The mean pH levels over all 36 sites for the treated, non-treated,
and woodlot soils were 7.1, 7.2 and 6.4, respectively. The mean pH
level for the treated soils was not significantly different from the
mean pH value for the non-treated soils. Three of the treated plots
had an average soil pH value lower than 6.0. When compared to the
non-treated plots for those sites, one of the non-treated plots (BL08)
also had an average pH value lower than 6.0.
At 25 of the 36 paired sites, the average pH value of the treated
plot was lower than the average pH value in the non-treated plot.
However, only two of those sites had a difference in pH which was
greater than 0.5.
For the sites where woodlot soils were also sampled, the mean pH
values for the treated, non-treated and woodlot soils were 6.8, 6.9,
and 6.4, respectively. None of the mean values were significantly
different.
Phosphorus Levels
Twelve of the 252 transect samples taken in all plots had available
phosphorus levels higher than the maximum of 60 ppm as specified in
the current guidelines. The maximum level in all transect samples
taken in the treated plots was 111 ppm, and 7 of the 108 transect
samples had phosphorus levels greater than 60 ppm. For the non-treated
transects samples, the highest phosphorus level was 318 ppm and 5
transect samples had phosphorus levels greater than 60 ppm. The highest
measured level in the woodlot transect samples was 24 ppm.
The mean phosphorus levels over all 36 sites for the treated, non-treated,
and woodlot soils were 29.4, 17.3 and 9.3 ppm, respectively. The mean
phosphorus level of the treated soils was not significantly different
from the mean level for the non-treated soils. However, further study
of the site record data determined that the non-treated soils at sites
BL05, BL07, BL08 and LS02 were permanent pasture fields which also
had received applications of manure. Elevated phosphorus levels due
to the applications of manure would be expected, and were confirmed
by the abnormally high average levels in the non-treated soils at
those sites.
Those sites were therefore excluded from the data base, and statistical
analysis was re-run on the analytical results for the remaining 32
sites. The resulting mean phosphorus levels for the treated and non-treated
soils were 29.2 and 9.4 PPM, respectively. The mean phosphorus level
for the treated soils was then significantly different from the mean
level in the non-treated soils. At 29 of the 36 sites, the treated
soil had a higher average available phosphorus level than the non-treated
soil.
Metal Levels
Arsenic
The arsenic level in all of the 252 transect samples was lower than
the maximum permissible level of 14 PPM for treated (sludged) soils
as specified in the current guidelines. For the treated, non-treated,
and woodlot transect samples, the maximum levels measured were 7,
7, and 9 PPM, respectively. There were no samples testing lower than
the method detection limit (MDL) of 0.5 PPM At 10 of the 36 sites,
the average arsenic level was higher in the treated soils than in
the non-treated soils. The mean arsenic levels for the treated, non-treated
and woodlot soils were 2.21, 2.24, and 2.06 PPM, respectively. The
means for the treated and non-treated soils were not significantly
different.
Cadmium
There were no transect samples with cadmium levels higher than the
maximum permissible level of 1.6 PPM as specified in the current guidelines.
Maximum levels measured in the treated, non-treated, and woodlot transect
samples were 0.9, 0.9 and 1.0 PPM, respectively. A total of 210 of
the 252 transect samples had cadmium levels which were lower than
the MDL of 0.5 PPM These were identified as Not Detected (ND) on the
laboratory analysis records. Eighty-nine of those samples were taken
in the treated plots, 92 were taken in the non-treated plots, and
29 were taken in the woodlots. Cadmium was only detected in 8 treated
plots, 5 non-treated plots, and 4 woodlots. After the ND levels were
replaced with the MDL of 0.5 PPM, the mean cadmium levels for the
treated, non-treated and woodlot soils were 0.54, 0.52, and 0.52 PPM,
respectively. The mean cadmium level for the treated soils was not
significantly different from the mean level for the non-treated soils.
However, interpretation of these means is limited because of the high
number of MDL values used rather than actual measured levels.
Cobalt
The maximum cobalt levels found in the treated, non-treated, and
woodlot transect samples were 10, 13 and 13 PPM, respectively. There
were no samples over the maximum permissible level of 20 PPM as specified
in the guidelines. The MDL was 2.5 PPM, and there were 8, 9 and 5
samples below that limit in the treated, non-treated, and woodlot
transect samples, respectively. After the ND levels were replaced
with the MDL of 2.5 PPM, the mean cobalt levels for the treated, non-treated,
and woodlot soils were 6.96, 6.95 and 6.46 PPM, respectively. The
mean levels for the treated and non-treated soils were not significantly
different.
Chromium
The maximum levels of chromium in the transect samples was 90 PPM
in the treated samples, 24 PPM in the non-treated samples, and 15
PPM in the woodlot samples. The maximum permissible level is 120 PPM
Chromium levels in 44 transect samples were below the MDL of 10 PPM,
with 10 of those samples being taken in the treated plots, 27 being
taken in the non-treated plots, and 7 being taken in the woodlots.
After the ND levels were replaced with the MDL of 10 PPM, the mean
chromium levels for the treated, non-treated and woodlot soils were
18.5, 13.9, and 14.1 PPM, respectively. The mean chromium level in
the treated soils was significantly different from the mean level
in the non-treated soils. At 24 of the 36 sites, the average chromium
level was higher in the treated soil than in the non-treated soil.
Copper
The maximum levels of copper measured in the transect samples were
37 PPM in the samples taken in the treated plots, 38 PPM in the samples
taken in the non-treated plots, and 65 PPM in the samples taken in
the woodlots. The maximum permissible level as per the guidelines
is 100 PPM Copper levels were below the MDL of 10 PPM in 47 of the
transect samples (11 treated samples, 21 non-treated samples, and
15 woodlot samples). After the ND levels were replaced with the MDL
of 10 PPM, the mean copper levels for the treated, non-treated, and
woodlot soils were 21.6, 17.7, and 17.6 PPM, respectively. The mean
copper level for the treated soils was significantly different from
the mean level for the non-treated soils.
At 26 of the 36 sites, the average copper level in the treated soil
was higher than the average level in the non-treated soil.
Mercury
The maximum levels of mercury in the transect samples were 0.2 PPM
in the treated samples, 0.06 PPM in the non-treated samples, and 0.09
PPM in the woodlot samples. The levels in all samples were below the
maximum permissible level of 0.5 PPM Mercury was detected in all samples,
and the MDL was 0.01 PPM The mean mercury levels for the treated,
non-treated and woodlot soils were 0.08, 0.05, and 0.08 PPM, respectively.
The mean mercury level in the treated soils was significantly different
from the mean level in the non-treated soils. At 28 of the 36 sites,
the average mercury level in the treated soil was higher than in the
average level in the non-treated soil.
Molybdenum
Molybdenum was not detected in any of the transect samples at the
MDL of 2.5 PPM The actual levels of molybdenum in the treated, non-treated,
and woodlot soils were not determined, but would be less than 2.5
PPM
Nickel
The maximum permissible level for nickel as per the guidelines is
32 PPM At site BL01, one transect sample taken in the treated plot
had a nickel level of 85 PPM, which was the maximum level in all samples
taken in the treated plots. The other two transect samples taken in
that plot had nickel levels of 12 PPM The maximum nickel levels in
the transect samples taken in the non-treated and woodlots plots were
31 and 16 PPM, respectively. Of the 252 transect samples, 107 samples
had nickel levels below the MDL of 10 PPM (39 in the treated plots,
51 in the non-treated plots, and 17 in the woodlots). After the ND
levels were replaced with the MDL of 10 PPM, the mean nickel levels
for the treated, non-treated and woodlot soils were 13.1, 12.6, and
12.1 PPM, respectively. The mean levels for the treated and non-treated
soils were not significantly different.
Lead
The maximum levels of lead in the transect samples were 45 PPM in
the samples taken in the treated plots, 39 PPM in the samples taken
in the non-treated plots, and 28 PPM in the samples taken in the woodlots.
None of the samples had levels greater than the maximum permissible
level of 60 PPM Lead was not detected in 26 treated samples, 38 non-treated
samples, and 6 woodlot samples at the MDL of 10 PPM After the ND levels
were replaced with the MDL of 10 PPM, the mean lead levels for the
treated, non-treated and woodlots soils were 14.3, 13.9, and 14.8
PPM, respectively. The mean levels for the treated and non-treated
soils were not significantly different.
Selenium
The maximum permissible level of selenium is 1.6 PPM At site BL06,
transect samples taken in the treated plot and in the non-treated
plot had selenium levels of 2.0 and 1.7 PPM, respectively. At site
BL02, all 3 woodlot transect samples had levels above the maximum
permissible level (1.8, 2.0, and 2.0 PPM). There were no transect
samples which had levels below the MDL of 0.25 PPM The mean selenium
levels for the treated, non-treated, and woodlot soils were 0.89,
0.85, and 1.09 PPM, respectively. The mean levels for the treated
and non-treated soils were not significantly different.
Zinc
The maximum permissible level of zinc is 220 PPM At site BL05, one
transect sample taken in the treated plot had a zinc level of 227
PPM At site BL09, two of the transect samples taken in the non-treated
plot had levels of 246 and 223 PPM, respectively. The maximum level
in the woodlot samples was 130 PPM The mean zinc levels in the treated,
non-treated and woodlot soils were 57.1, 57.5, and 56.0 PPM, respectively.
There were 7 transect samples with levels lower than the MDL of 25
PPM (1 treated, 6 non-treated).
Table
5. Average pH, Phosphorus and Metal Levels by Site Number - Treated
Plots
Table
6. Average pH, Phosphorus and Metal Levels by Site Number - Non-Treated
Plots
Table
7. Average pH, Phosphorus and Metal Levels by Site Number - Woodlot
Plots
Table
8. Mean, Maximum, and Minimum Levels for All Parameters by Treatment
Table
9. Summary of Number of Transect Samples and Analysis by Individual
Parameter
