Road salt: pollution or improvement?
Boonzaaijer, E., Vromen, E.M.
Kandinsky College Nijmegen, The Netherlands
22-04-2011
Summary
Salt is used often to melt the ice on the roads. This is to prevent accidents from happening.
But when the ice melts, where does the salt go? The soil absorbs this water, and the salt goes
with it. Does it stay in the soil or does it go to the groundwater as a result of washout. And
this raises further questions: if the salt washes out, will it pollute the groundwater? What are
the consequences for the environment when the salt level increases in the groundwater?
Introduction
In groundwater, there are certain minerals
and salts dissolved. A certain amount of
salts is allowed to be in the groundwater,
but this amount cannot get too high. This
would affect the environment in an
negative way.
This raises the question: What is the effect
of the use of road salt on the concentration
of salt in groundwater?
Our hypothesis is: Using road salt will
increase the concentration of salt in
groundwater.
Experimentally it was found that a road
covered with a 10% salt (NaCl (s)) will
have the fastest effect on the melting of
ice, and thus, this is the amount we will
use.
Experimental procedure
We took four identical measuring cylinders
and four identical funnels. In each funnel
we placed a filter-paper. The funnels were
situated on top of the measuring cylinders.
In two of the funnels we put 10g of coarse
sand. On both we put 20 ml of frozen
water, one with 2g of NaCl (s), one
without. In the other two funnels, we
put10g of fine sand. On both we put 20ml
of ice, one with 2g of NaCl (s), one
without.
When all the ice was melted, we took 2ml
of the melted substance from the
measuring cylinders. We placed that on an
aluminium plate. We evaporated the
solutions, and we weighed them. Two were
representative for real groundwater, two
for groundwater when road salt has been
used.
Results
Discussion and conclusion
In figure 1, the amount of salt that we
measured after we evaporated 2 ml of
melted substance is shown. In figure 2 the
concentration per Liter is shown.
From the experiments without salt is the
concentration of salts in normal
groundwater shown. To see how much of
the road salt actually ends up in the
groundwater, you have to subtract the
concentration of salt in sand without road
salt from the concentration of salt in sand
with road salt.
The results of these equations are shown in
figure 3.
For all figures, see enclosure.
As you can see, the concentration of road
salt that the groundwater absorbs, is in
both coarse as fine sand, 65 times higher
than the normal concentration of salts in
ground water.
We conclude that our hypothesis was right:
the effect of the use of road salt on the
concentration of salt in groundwater is that
it increases it.
The soil always contains some salt, but an
increase this large could have serious
consequences for animals and plants.
People should look for better solutions.
There are various alternatives. Take for
example biological salts, that is something
that we could look into.
Looking critically at our experiment, we
could have used more set-ups, to check our
previous experiments. We also could have
been more accurate. More precise
measuring cylinders could have been used.
The filter paper might also still contain
some salt. We didn’t look at the amount of
salt in the sand alone, and in the water
alone: this is another possible improvement
point.
Bibliography
1. ICY – road salt booklet
2.http://www.trosradar.nl/nieuws_detail/be
richt/strooizout-wat-is-het-en-hoe-werkthet//0ef47d526a479a30e726c1511320f433
/27/?tx_comments_pi1%5Bpage%5D=5
Enclosure
Coarse sand (g)
Fine sand (g)
With salt
0,260
0,130
Without salt
0,004
0,001
Figure 1: amount of salt after evaporation of 2 ml of each product
Coarse sand (g/L)
With salt
130
Without salt
2
Figure 2: the concentration of each set-up
Fine sand (g/L)
65
1
Coarse sand (g/L)
Fine sand (g/L)
128
64
Figure 3: the concentration of road salt that ends up in the ground water