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Substrate research
Hi All,
It's been kinda slow this afternoon at work, so I started a little
project I've been curious about for some time now. My tanks use a
kitty litter/sand substrate and I've never had any complaints. First
off, I don't move the big plants around to disturb anything serious.
And, second, I don't have my 'mining cichlids' in those tanks,
either. My cichlid tank is about to undergo big changes, I'm
replacing the gravel bed with Fluorite. Being born with a very
stubborn, analytical brain, I had to research. I was very curious to
find what my substrates were made of, elementally. Since I work at
a lab and do trace metal analysis, I knew it was only a matter of
time before I got the best of myself.
I did analysis on 3 samples: Fluorite, Wal-Mart Special Kitty litter,
and soil from my garden. 1g of dry sample was pulverized by a
mortal/pestal and digested according to Method 3050B EPA Soil
method. *Disclaimer of method - This is not a total digestion. It is a
very strong acid digestion that will dissolve almost all elements that
could become "environmentally available". By design, elements
bound in silicate structures are not normally dissolved by this
procedure as they are not usually mobile in the environment.* This
is still a VERY good representation of what is in the sample, as we
use it daily for all kinds of solid samples. A Hydrofluoric acid
digestion in more complicated, but more geologically correct, as it
gets EVERY element in solution. I will do the HF digestion later to
compare results. Should be quite interesting. Here's what I got:
Element Soil (mg/kg) Litter (mg/kg) Fluorite (mg/kg)
Al 5700 6000 6800
As < 8.1 11.3
Ba 156 11.6 133
Be 0.2 0.5 0.3
Ca 5800 14300 530
Cd 0.6 2.4 <
Co 2.6 2.7 3.4
Cr 10 30 6.2
Cu 73 12.6 13.8
Fe 11500 14500 9610
K 433 2200 1700
Mg 1000 3760 1490
Mn 136 47.5 85.5
Na 570 395 444
Ni 4.1 21.1 8.0
Pb 218 ? 9.3 5.4
V 24.5 12.3 8.8
Zn 248 70.5 33.5
Three things caught my eye. First, where did my garden get Pb
from?? It's an old house and the garden in right against the wall, so
maybe years of lead paint leaching from rainwater into my soil. I
don't care, the veggies are delicious! Second, the As level in
Fluorite. It's addressed in their website, it doesn't leach out and is
no cause for concern. And, third, does my cat know he is standing
in Cd laced clay? I don't know where it came from, either, but
again, it doesn't leach out. My water tests sooo clean from my
tanks, and the only thing that ever shows is the things I add. I was
real surprised to see how dynamic my litter was. It's loaded with all
kinds of good stuff, plenty of Ca, Fe, K, and Mg. The soil looked
good, too, except for the lead. The Fluorite was the least reactive of
the three. It's hard as hell to grind up and just sits in the acid,
where the other two fizz and bubble, mainly because of the Ca
compounds and the organics in the soil. Small amounts of the litter
and soil went into solution, but I think all of the Fluorite stayed in
the beaker. It's like a crumbled brick sample.
I've got to admit I'm impressed by them all. I would've bet any one
of them would have lacked something important, but they're all
comparatively good. I didn't test my gravel, probably something like
950,000 mg/kg SiO2 ;-). I hope someone finds it all interesting.
Now, it's time to wash and rinse 45lbs of Fluorite.
Jamie
Jamie Johnson
Greenwood, SC
jjohnson at davisfloyd_com
jjirons at greenwood_net (home)