Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Half-Life of DDT
Name: John C. H.
Status: educator
Age: 60s
Location: N/A
Country: N/A
Date: 1999-2001


Question:
We are studying exponential growth and decay models in a precalculus course. One of my students has asked if there is such a thing as a "half-life" of DDT. If so, where do I get the data to model this compound?


Replies:
OOPS! Here is another iceberg inquiry -- the question is only reveals about 10% of the answer(s). I searched the term "DDT" on www.google.com and found many "hits". Estimates range from 28 days to 150 years, with some consensus of about 15-20 years. Here is why the answer is so tricky.

1. If you feed DDT to some test species for some period of time and then cease and monitor the level of DDT vs. time -- that gives one type of half-life that depends on the species, its diet, and other factors. For some birds I saw the figure of about 8 years.

2. If you measure the concentration of DDT in sun-exposed, oxygenated surface water and have conditions so that there is no steady state -- you get another half life. Under these conditions volatilization and absorption onto the river/lake bed occurs. I saw the number 28 days for this route.

3. If you measure the level of DDT in a contaminated soil, to which DDT adheres tenaciously, you get yet another half-life. This is where I saw the number from 15 to 20 years.

4. If you test the soil in temperate climates where the average temperature is milder, this decade or two stretches out to 3 or 4 decades.

5. In cool dry sand, I saw the number 150 years -- although that has to be suspect because DDT was not widely available until 1945-1950 (after World War II).

If this is for a pre-calc., you could introduce the concept of parallel first order decay processes!

Vince Calder


John,

The half life of DDT is about 12 years.

Regards,
ProfHoff 286



Click here to return to the General Topics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory