INTRODUCTION

Groundwater quality is an issue which needs attention because of the potential hazard associated with contamination of our nation's water supplies. The United States depends on farmers and the agricultural industry to maintain current production levels of food and fibre. As a result, they make extensive use of fertilizers, pesticides, and other chemicals to control disease while promoting plant and animal growth. The negative aspect of the use of these chemicals is their possible transport into groundwater which supplies about 25%. of the nation's fresh water. Accurate information on the possible contamination of groundwater by agri-chemicals is needed for intelligent planning by management, government, and industry. Such information can only be obtained by creating and testing various hypotheses which attempt to describe chemical mobility. This can be accomplished by designing computer models which integrate and incorporate the latest scientific knowledge allowing simulations of environmental impact. Among these processes are physical, management, crop growth, nutrient, soil chemistry, and pesticide processes.

The pesticide processes include many physicochemical relationships. In order to simulate these processes, complete and accurate data on the properties of each chemical used must be available for input into the model. Without complete and accurate data, the accuracy, and hence value, of the model is severely reduced.

At present there is no definitive database of properties of chemicals used as pesticides. There are a number of compilations of data on pesticides, including Handbooks which are either devoted completely or partially to data on pesticides. However these sources or databases are incomplete in their scope of information and also lack criteria for defining the quality of the data reported. In addition, the data are often reported without mentioning the temperature at which the parameters were obtained, nor in the original source. These databases also have data gaps which limit their usefulness for many modeling activities. This research project is designed to produce a pesticide database containing the highest quality data available.

APPROACH

A definitive database of pesticide properties will be created with a well defined, step-wise systems approach. The overall steps are as follows:

1. Establish a Pesticide Properties Database (PPD) National Research Project Coordination Team (NRPCT).

2. Design the database, search the literature, obtain data from other sources, and enter the data into the database.

3. Evaluate the data (accuracy, quality, and completeness) according to established or newly developed criteria. Data will be evaluated in an objective manner, using a series of expert systems which will be developed for that purpose.

4. Fill in the data gaps by calculating missing properties using existing or newly developed theoretical techniques which have been validated for the various classes of compounds found in the database.

5. Disseminate the database.

6. Maintain and update the database.

STATUS

1. Establishment of a PPD National Research Project Coordination Team (NRPCT).

A team of scientists from ARS, other government agencies, and industry has been established to provide leadership and facilitate the team coordination. The team will function under the guidance of the ARS National Program staff (NPS) representatives. The team members will consist of scientists from the Systems Research Laboratory and the Pesticide Degradation Laboratory in Beltsville, Missouri, the Southeast Watershed Research Laboratory in Tifton, Georgia, scientists from other government agencies, and scientists from universities and industry (from companies belonging to the National Agriculture Chemical Association (NACAI). Representatives from the EPA Office of Toxic Substances, Office of Pesticide Program and US Geological survey are also being asked to serve on the team. A representative from the International Union of Pure and Applied Chemistry (IUPAC) Pesticide Commission will also be asked to serve on the team. IUPAC participation is important as part of the evaluation of the database and the distribution of the database to the scientific community. The team will use the System Research Laboratory's Agricultural Systems Research Resource (ASRR) computer conferencing software for continuing discussions. The conference. "PESTICIDE DATABASE" has been established and all interested parties are being invited to join the conference, which can be accessed by direct dial, Telenet, or Arpanet.

The PPD NRPCT will approve the plans submitted to the group by the Team Leader and generally oversee the activities to assure that they are on target, on time, and are supporting ARS objectives and other groundwater needs of the U.S.A. When necessary the PPD NRPCT will meet, although most of the work is expected to be done locally and via computer conferencing.

2. Design the database and search the literature, obtain data from other sources, and enter the data into the database.

The first 30 compounds have been chosen for the database from a prioritized list of compounds being studied by the ARS. These are shown in Figure 1. Many additional compounds are to be added in the next year as data are received by members of NACA who have agreed to voluntarily contribute data to the project: The data being submitted by industry to this project are the same as those provided to the states of California and Arizona under those states' pesticide registration laws. The initial list of some 40 properties (fields or data elements) which are to be included in the database have been chosen and the information associated with each item has been defined. This will include chemical names, CAS Registry Number (CAS RNI, and other identifiers, and variables (temperature, pressure, pH, and so forth), as well as important chemical properties such as solubility, vapor pressure, various partition coefficients, and rate constants. Details on the data elements, format, and access to the ARS ASRR computer system are available upon request from the senior author (SRH).

The dgasell computer database management system, coupled with the Clipper software, has been chosen for implementation of data entry, updating, search, and retrieval. Dgasell is so widely used and by using Clipper we are able to provide a royalty-free search system for IBM PC compatible computers, other software would have required royalty fees and would have involved other non-technical complications which would have made the world-wide dissemination of the PPD more difficult.

SUMMARY

To date most of the effort has been expends searching the literature and obtain any data from other sources. Cooperation from industry has been essential to the project's progress. The need for data evaluation has been pointed up most strikingly by data on the solubilityof the insecticide fenthion. We have found that for almost 30 years the solubility of fenthion has been reported in handbooks as about 55 ppm, whereas the correct solubility (run under proper experimental conditions) is actually 4.2 ppm. This difference of a factor of almost 15 is too great to be ignored. Table 2 shows the summary of the solubility values reported for fenthion [1].

After a year of work on the first evaluated database of pesticide properties we feel that the goals of the project can be accomplished, but that more time than originally anticipated will be required, as the available data are more difficult to obtain and are less reliable than first anticipated. An interim database of values obtained will be our first goal, followed closely by proper evaluation of the database, with appropriate data quality indicator ratings.

REFERENCES

[1] Heller, S. R., Scott, K, and Bigwood, D. W., The Need for Data Evaluation of Physical and Chemical Properties of Pesticides, Envirn. Sci. Tech., submitted.