Subject: environ. model summary

From: [email-masked] (Marketing)
Date: Tue, 12 Jul 94 11:21:34 PDT

Dear Netters,

Here is the summary of responses to my query regarding environmental
modeling, which were extremely helpful. I have since obtained
two of the codes (PRZM and GLEAMS) from the EPA and USDA offices
listed in the postings below.

Many thanks again to all who responded or expressed interest.

Bill Glauser 

---------------------------------------------------------------------------

(Original posting)

 |Has anyone heard of any of the following codes:
 |  PRZM, GLEAMS, EXAMS, and EPIC

 |They are presumably used for environmental modeling to
 |assess the fate of pollutants in the environment.

 |I am curious as to the models that underlie these codes.
 |For example, what kinetic, thermodynamic, and transport
 |models are used to determine how a compound partitions
 |between the water, ground, and atmosphere?

 |On a related note, what is the level of maturity of the field
 |of environmental modeling (probably macroscopic)
 |versus molecular modeling (microscopic)?

 |Finally, where can one obtain these codes and on which platforms
 |do they run?

 |Thanks in advance for your help.

 |Bill

---------------------------------------------------------------------------
From: [email-masked] (Steve Bowlus)

GLEAMS and PRZM (and possibly the others) are soil fate models, commonly 
used in the pesticide industry for modeling runoff of pesticides from 
fields.  I forget the exact acronyms, but they are something like _G_round 
_L_oading _E_ffect... and _P_esticide _R_oot _Z_one _M_odel. . .you can get 
the drift from the names.  These are transport models, which depend on the 
physical properties of the materials being modeled.  At this point, the 
only "molecular modeling" that I have done in the systems is to evaluate 
physical properties, such as partition coefficients and Henry's constants.

Try R.A. Leonard, W.G. Kinsel and D.A. Still, Transac. Am. Soc. Ag. 
Engineers, vol 30 no. 5 (1987) for a description of GLEAMS.  

You can get a lot more information about these models from our biologists 
at our Gilroy test center:  talk to Rakesh Jain or Bob Lamoreaux.  We use a 
program called PRE-AP, which is a front end for GLEAMS.  Their number is (
408) 848-1474.

sb

---------------------------------------------------------------------------

From: Dr. Dave Winkler <[email-masked]>

I would greatly appreciate a summary of the responses.

---------------------------------------------------------------------------

From: [email-masked] (CGI Jim Jones)

Bill,

My company consults on high-level nuclear waste disposal and we are familiar    with most codes related to the environment, but have not heard the four that youmention.

There are several places you might try:

Energy Science and Technology Software Center
	e-mail:	[email-masked]

	phone:	703-487-4753

Let me know if you don't get what you want from those and I'll see if I can
point you to some other places.

If you do find out any information on those applications, could you let me know?

--------------------------------------------------------------------------

From: [email-masked] (Gary Meier)

I've had very limited exposure to PRZM (Pesticide Root Zone Model) and
GLEAMS (Groundwater Loading Effects of Agricultural Management Systems).
The former is available from the U. S. Environmental Protection Agency
Center for Exposure Assessment Modeling (CEAM) in Athens, Georgia,
(706)-546-3549.  The latter is available from the U. S. Department of
Agriculture, Agricultural Research Service.  Contact J. R. Williams or C.
W. Richardson at the Grassland, Soil & Water Research Lab in Temple, Texas,
817-770-6500.  As of a year ago, both programs were available without
charge (I think they want you to send them blank disks).  I believe both
programs run only on IBM PCs and clones.

I don't know a lot about the models that underly the codes, but PRZM at
least permits very detailed modeling of pesticide movement in the surface
water, throught the root zone, and in the ground water.  Effects of
weather, soil and crop types (including crop rotation), irrigation (if
used), pesticide application rate and timing, and a host of other
parameters are entered.  Pesticide movement is calculated using daily time
steps in simulations that typically cover several years to several decades.
When I was playing with the program, a three-year simulation of low to
moderate complexity required just 3 or 4 minutes on a 25 mhz 486 PC.

I haven't had opportunity to validate the programs or do any other
comparisons to real-world results, so I can't comment on how accurate the
simulations are.

I hope you find this useful.

Gary

--------------------------------------------------------------------------