30-09-2004, 03:13 PM
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(Pat Kiewicz) wrote in message ...
simy1 said:
1) would you put furnace slag in your garden? if you google "slag
chremical composition" the first hit is from our own group and there
are sites linked from there that support the idea of using slag as a
source of micronutrients, specifically Mg, Mn, Fe, and S (there is
also lots of Ca and some K, but given that I already spread wood ash,
those are unneeded)
Some people would worry about heavy metals. Here's something from Penn State:
"Some slags may contain elevated concentrations of trace metals such as iron,
cadmium, chromium, copper, lead, molybdenum, nickel, and zinc. Concentrations
of these metals will vary in slags from different sources. All of these metals occur
naturally in soil, and many are essential plant nutrients. If concentrations in the
slag are similar to soil concentrations, they present no problem. If they are present
at substantially higher concentrations in the slag than in the soil, repeated
application of the slag could significantly increase soil concentrations of the metal
in soil. This possibly could lead to plant toxicity, increased plant uptake and transfer
of metals to animals or humans, or to other environmental problems. Before using
a slag, be sure to obtain several laboratory analyses of the total concentrations of
these trace metals in the slag."
I worked briefly in the past for a mining company, and chemical
composition of the rock was an issue. I was amazed at the difference
in heavy metals concentration between iron ore and granite rock. Iron
ore typically has 100 times less lead, mercury, or uranium than
granite. It is a very pure rock, as far as toxic stuff is concerned.
I understand that if the foundry is used to smelt lead all bets are
off, and of course I had not thought of Cd and was originally worried
about Al (the other elements will not be a problem for a light
application). On the other hand, anyone eating local foods in red clay
tropical areas intake far more aluminum than I would intake. In a
Michigan acid sandy soil, my guess is that slag mainly serves a
purpose of providing Mg and perhaps Ca.
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