Acid rain isn’t a new threat to the environment. But its effect on trees and soils has been a point of debate. Now, a new study supports the theory that acid rain can deplete nutrients in forest soil. The Great Lakes Radio Consortium’s Corbin Sullivan has more:
Acid rain isn’t a new threat to the environment. But its effect on trees and soils has
been a point of debate. Now, a new study supports the theory that acid rain can
deplete nutrients in forest soil. The Great Lakes Radio Consortium’s Corbin Sullivan
Acid rain is caused by emissions mostly from coal-fired power plants. It’s linked to “dead”
lakes and streams that have become too acidic for fish and other organisms.
But a new study published in the Soil Science Society of America Journal says the
addition of even a small amount of acid to forest soils can deplete minerals needed for
plant and animal survival.
Ivan Fernandez is the lead author of the study. He says the study showed the loss of
several nutrients, but he’s most concerned with calcium loss.
“Calcium both reduces the toxicity of bad things as well as being a required essential nutrient.
If you lose too much calcium, you can have direct nutrient deficiencies.”
Fernandez says when minerals like calcium and magnesium are lost the result is
slower plant growth. He also says the loss of these minerals can lead to poor water quality.
For the Great Lakes Radio Consortium, I’m Corbin Sullivan.
Sludge being spread over a field with a manure spreader. (Photo by D. Seliskar, Halophyte Biotechnology Center, Univ. of Delaware)
The more people inhabit the earth – the more sewage there is. Something has to be done with it. Before chemical fertilizers were invented, farmers used human manure to improve their crops. Some still do. About three million dry tons of treated sewage – called sludge – fertilize sod, pasture land and even food crops every year in the United States. The Great Lakes Radio Consortium’s Amy Tardif looks at what the practice may be doing to the environment:
The more people inhabit the earth – the more sewage there is. Something has to be done with it.
Before chemical fertilizers were invented, farmers used human manure to improve their crops.
Some still do. About three million dry tons of treated sewage – called sludge – fertilize sod,
pasture land and even food crops every year in the United States. The Great Lakes Radio
Consortium’s Amy Tardif looks at what the practice may be doing to the environment:
The U.S. Environmental Protection Agency says using treated human waste as fertilizer is the
most environmentally sound way to get rid of it. It used to get dumped in the oceans. The
pollution caused dead zones.
Now, using it on land is becoming controversial. As people move closer to rural areas, they
discover what’s happening. It smells. It might also cause damage. Tommy Drymon insists the
creek near his Florida home has changed because farmers near his house use sludge as fertilizer.
“This was the most beautiful place I’ve ever settled down to. And the creek just looks awful now.
It used to be clear and now it’s just black and mucky all the time.”
Drymon says not only has the color changed – there’s more icky residue on the shore. He rarely
sees otters, deer and other wildlife any more. He definitely stopped swimming in it. Drymon and
his neighbors think the human fertilizer nearby farmers use – known as sewage sludge – is to
Sludge is made at sewage treatment plants. The water people flush down their toilets gets pretty
clean with today’s methods. That means more of what’s leftover stays pretty dirty. It resembles a
thin pudding or a powder depending on how it’s treated. It can contain viruses, bacteria,
chemicals and cancer-causing heavy metals.
“Now this sewage sludge includes not just human waste, it includes Pine Sol if you clean your
toilet bowl with Pine Sol, or if you do oil painting and you flush the paints down the drain or if
you work in a chemistry lab….”
Eric Giroux is an attorney for Earthjustice. He’s handling a lawsuit for Tommy Drymon and his
neighbors. It claims sewage sludge dumped on farms there is wafting through the air making
them sick and running off into the creek.
There are federal, state and county rules meant to prevent runoff. There are buffer zones from
water bodies and rules to protect groundwater. But sludge is not always applied according to the
rules. And there are things missing from the rules – according to The Cornell Waste
Management Institute. They don’t deal with poisons such as flame retardants, the drugs we take
and toxic chemicals that harm fish and wildlife and inhibit plant growth.
But those who use sludge as fertilizer like it.
“It’s a product that has to have something done with it. And if it’s done properly there are no
Dennis Carlton has used the free product on his cow pastures for ten years. He says the calves
raised on those pastures end up weighing more than others. Sludge saves him sixty to 160 dollars
an acre on expensive chemicals.
“It’s cost effective and it does a better job than the commercial fertilizer because it last longer
because of the slow release qualities.”
Sludge contains lots of nitrogen – which is food for plants. It’s organic. Plants absorb it very
slowly. And that’s good.
Since 1997, University of Florida Soil scientist Martin Adjei has compared typical commercial
fertilizer – ammonium nitrate – with sludge. He says his studies show the good stuff in sludge gets
into the plants very nicely, and he says plants don’t seem to absorb the heavy metals.
“We measured lead, barium, cadmium, nickel in the plant. They were all point zero, zero two or
something parts per million in the plant.”
That’s lower than the EPA says it has to be. Adjei says only trace amounts of metals sunk into the
groundwater. He doesn’t know yet whether the metals drift into the soil. But he found too much
of the nutrient phosphorous builds up in the soil when fertilized with sludge year after year. He
admits there are many more tests to be done.
This year the EPA responded to complaints about sludge. It plans to test it for 50 chemicals – far
more than ever before. Geff Grubbs is the EPA’s Director of Science and Technology.
“We’re focusing on a couple of things, one is beginning to ramp up some of the research
investments to strengthen our understanding of some of the processes and nature of the
contaminants that could be present in sludge and what risk they might or might not pose. And we
do have a number of things that are in the works both near and longer term that might lead to
changes in the underlying regulations about what can be in biosolids before they are applied to
And, the EPA and a few industry groups have created a best practices program for willing
utilities. They pledge to control the odor and dust as well as manage the nutrients in their sludge.
The utilities are then audited by impartial, independent, third parties. There are only 48
municipalities participating nationwide.
For the Great Lakes Radio Consortium, I’m Amy Tardif.