Does anyone know how long DTT remains in the soil after spraying?

Question

In Rachel Carson's "Silent Spring"
She talks about the use of DDT that was often used in spraying as a pesticide. I believe it still is in the third world.
She talks of man's power to destroy nature, and war against nature is war against man.

I only want to know the answer to this to satisfy my own curiosity.

Thank you for your answers, they were very interesting to read. One wonders what effects DDT had on the generation when spraying was at it's worst, although I know these things don't usually show up until years later...

Answer 1

Problem with DDT is that it doesn't breakdown easily but bioaccumulates. This has led to poisoning events like the ones that Carson refers to.

Even what was seen as low level of use back in 50/60's remained in soil, washed into rivers, consumed via the contamination of organic foodstuffs (algae etc) by fish, then fish eaten by birds and the 'accumulation' effect led to toxic and deadly levels of ingestion by bird populatoon.

DDT should not be being used in the third world -- but chemical manufacturers have no conscience about such things. Their attitude is theat the 'buyer beware'...if somene wants to buy a posionous pesticide they will supply it!

Proft is their only motive and they shrug off responsibilty on the grouns that it 'a farmers choice'. This is why deaths and injury have occurred to many farmers in India.

QUOTE:
"...persistent organic pollutants.

POPs, which include DDT, are long-lived, highly toxic, and able to travel long distances.

WWF says that most of the millions of tonnes of DDT used in the past remain in the soil and spread throughout the environment.

It says one US orchard still contained 40% of the DDT that had been used on it 20 years previously.

The report says the chemical can be sprayed in an African village and end up in the fat of polar bears in the Arctic. "

Ref: http://news.bbc.co.uk/1/hi/sci/tech/262698.stm

Answer 2

Once in the environment, DDT in soil lasts for a very long time. Some studies show that half the DDT in soil breaks down within 2 years, but other studies show that it takes more than 15 years. Some DDT may evaporate from soil and enter the air, and some may be broken down by the sun or by microorganisms.

Answer 3

It can still be found in concentrations in the range of parts per billion (one part per billion is about the same as 1 second in 32 years). In some of the rural southern farmfields, where soils are disturbed by tilling everyear, you can still find trace amounts in the sediments that have runoff into the rivers.

It has been determined that it was better to leave them there than to dredge the river and disturb the stuff. But, there are warnings everywhere to watch the number of fish you eat (like no more than 2 a month).

Now, some of the fish were contaminated with mercury, but a few streams were impacted with DDT.