Environmental Engineering Reference
In-Depth Information
Hydrocarbons were predominately medium-weight (C10-C14; C15-C28), with
occasional spikes in light (C6-C9) and heavy (C29-C36) fractions.
Hydrocarbon fractions were co-correlated, so TPH (the sum of all four fractions)
was generally a good summary of individual size fractions. TPH distribution was
skewed towards high values; with the mean TPH concentration (810 mg/kg) four
times the median (212 mg/kg). Cu concentrations correlated negatively with catch-
ment age (Spearmans r = −0.12, p = 0.009, before E&E program only).
The effect of the education and enforcement (E&E) program was obscured by
large variations between sub-catchment groups. Mean Cu, Zn and TPH concentra-
tions grouped by catchment are summarized in Fig.
2
. A downward trend in Zn and
TPH concentrations was observed in treatment sub-catchments in three groups
(Fig.
2
). Cu concentrations were significantly lower in Dunlops A treatment sub-
catchments (t
9
= 5.4, p < 0.001).
Zn concentrations were significantly lower in Dunlops A (t
9
= 3.4, p = 0.008), and
marginally significantly lower in Heatherton (t
8
= 2.3, p = 0.055) treatment sub-catch-
ments. TPH was significantly lower in Heatherton (t
8
= 2.9, p = 0.021), Dunlops A
(t
9
= 2.3, p = 0.046) and Dunlops B (t
17
= 2.5, p = 0.025) treatment sub-catchments.
In contrast, an increase in media pollutant concentrations in the Settlement
group of treatment sub-catchments was identified (Fig.
2
). Zn and TPH concentrations
Heatherton
Settlement
Dunlops A
Dunlops B
**
50
*
30
20
10
6
300
200
150
100
**
*
6,000
2,000
500
200
50
*
*
*
Before
After
Before
After
Before
After
Before
After
Fig. 2
Mean Cu, Zn and petroleum hydrocarbon (TPH) concentrations (mg/kg) accumulated by
GAC media grouped by sub-catchment.
Bars
represent mean ± 1 standard error. Control sub-
catchments in
white
, treatment sub-catchments shaded. Difference between groups significant at
p = 0.05*, p = 0.01**