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In
the Lab
Total Suspended Solids
| At most LMVP sample sites, volunteers
collect and filter water to measure inorganic suspended solids (suspended
sediment). For this test, a volume of water is pulled through a
glass fiber filter using a vacuum pump. The filter strains tiny
particles from the water in much the same way a colander strains
pasta. Afterwards, the filter is carefully folded to make sure all
of the particles remain on the filter, placed in a protective filter
“house” and then frozen. |
| When we conduct the analyses for inorganic suspended
solids, the first step is to dry the filter to remove any remaining
water. To accomplish this, the filters are heated to 105 degrees
C (221 degrees F). Then the filters are weighed. After being weighed,
the filters are cooked at an extremely high temperature (500 degrees
C or 932 degrees F). At such a high temperature, any organic bits
are burned away, leaving only inorganic compounds behind. The organic
bits on the filters often spark and flash as we put the filters
in the oven! The filters are weighed again after cooking for 20
minutes. |
Lindsay
the Lab Tech takes filters out of the drying oven. The next
step is to weigh the filters, then cook them at 500 degrees
celcius (932 degrees F) |
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Here is where it can get really complicated.
We now have to compare the weight of the filters after cooking
to the weight we recorded before we gave the filters to the volunteers.
It is the only way we can determine the weight of the substances
on the filter. This means that we have to identify every single
filter by the number written on the paper filter “house”.
This is easily accomplished if a volunteer is only sampling one
site. However, when a volunteer samples multiple sites there is
often some confusion. What usually happens is that a filter intended
for one site will be used at another. As long as the change is
recorded on both the filter “house” and the data sheet,
and we can still read the original number, there is no problem.
It can be very confusing, though, if the volunteer isn’t
aware of the change, or a well-intentioned volunteer scratches
out the old site number and writes the new one in. It takes much
work, but these issues can usually be resolved through deductive
reasoning.
After we have identified the filters, we are ready to enter the
data into our database. From here we can make those nifty graphs
you see in the data report each year!
Tony Thorpe
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Remember:
1.)
Don't touch the filter with your bare hands
2.)
Don't alter the number on the filter
3.)
Be sure to record on the data sheet the filter number, the
site number (if applicable), and volume of water filtered |
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Back to
the Winter 2003 Newsletter
Brought to you by the Lakes of
Missouri Volunteer Program |
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