Environmental Engineering Reference
In-Depth Information
In case of the location J, the Cd content was distributed from 0 to 0.018 mg/L in
the runoff samples with a mean value 0.007. The values showed decreasing diurnal
trend for fi ve events namely I, II, III, IV (except sample J7) and V while no Cd could
be detected in the rest events, VI and VII. Here the concentration of cadmium
showed positive correlation with pH i.e. cadmium is leached to the runoff more with
increasing pH.
For location N, the range of Cd content was 0-0.024 mg/L with a mean value
0.006. Event I had an increasing trend, event II had no distinct trends and no Cd
could be detected in event III. The cadmium concentration increased with increas-
ing pH values i.e. more cadmium mobility from soil to rainfall runoff was observed
with higher pH values.
Location K showed Cd content from 0 to 0.021 mg/L with a mean value 0.009.
There was a decreasing trend in event I and no distinct trend was seen in case of
events II and III. The Cd values showed an inverse correlation with the correspond-
ing pH values.
For the location M, Cd content was found from 0 to 0.015 mg/L with mean value
0.006. In such cases, an increasing trend was followed by a decreasing one for two
of the events, I and II. The cadmium content showed inverse correlation with the pH
of the location.
In case of location R, the range of Cd was 0-0.021 mg/L with a mean value
0.009. The diurnal variation for each event was different. Event I showed no specifi c
trend whereas event II showed increasing trend and in the last event no cadmium
could be detected. The location showed cadmium mobility to the runoff at lower pH
conditions.
In case of location U, Cd content distributed from 0.001 to 0.017 mg/L with a
mean value 0.013. The three events showed different diurnal variation where no
distinct trend could be seen in any of the three events.
The location Z had a Cd content in the range of 0-0.003 mg/L with a mean
0.0005 where there is no Cd detected in the event I and no specifi c trend could be
observed in the event II.
The cadmium content showed an inverse correlation with pH which was found
by Manning et al. ( 2011 ) in his work on spring runoff water at Colorado. This could
be attributed by the fi ndings by McDowell ( 2010 ) that since cadmium sorbs to and
accumulates to the top layer i.e. 0-2 cm depth of soil (Jalali and Arfania 2011 ), there
is possibilities for the cadmium loss via surface runoff in particulate associated and
dissolved phase, hence erosion becomes signifi cant form of Cd loss (Edwards and
Withers 2008 ).
Cadmium may be contributed to the runoff via leaching of soil which occurs
through soil-plant systems (McDowell 2010 ). Cadmium may enter into water from
industrial processes such as the smelting and refi ning of ore minerals, electroplating
and paint manufacturing, combustion of fossil fuels, and also from the application of
phosphate fertilizers (Selles et al. 2003 ), leaching from contaminated landfi ll or from
soil having sewage sludge dumping. The concentration in unpolluted water is <1
g/L.
Cadmium is considered as a very toxic metal due to its high mobility and at a low
concentration, it can affect the living organism (Benavides et al. 2005 ). A set of
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