Selected insecticides (chloropyrifos, diazinon, fonofos, and terbufos) in ground water

DESCRIPTION OF CONTENTS OF FILE GW1PEST4.DAT


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| DATA FILE FORMAT |
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columns  1-15  Station ID number
columns 21-26  Date (YYMMDD format)
columns 31-34  Time
columns 41-49  Water level (Storet code 72019, feet below land surface)
column  51     Remark for dissolved fonofos
columns 52-59  Dissolved fonofos (Storet code 04095, in micrograms per liter)
column  61     Remark for dissolved diazinon
columns 62-69  Dissolved diazinon (Storet code 39572, in micrograms per liter)
column  71     Remark for dissolved chlorpryifos
columns 72-79  Dissolved chlorpryifos (Storet code 38933, in micrograms per liter)
column  81     Remark for dissolved terbufos
columns 82-89  Dissolved terbufos (Storet code 82675, in micrograms per liter)


NOTES: A < symbol in the remarks field indicates the pesticide was not
       detected in the sample.


       An E in the remarks field indicates the concentration given is
       estimated.  (An E remark associated with a low concentration typically
       indicates the pesticide was positively identified by spectral
       characteristics and retention time but that the concentration is
       less than the method detection limit.  An E remark associated with a
       high concentration typically indicates the reported concentration
       exceeded the range of the calibration standards and was estimated by
       extrapolation.)


       Water levels or concentrations less than zero (for example -999.999)
       indicate no data are available for that observation.




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| STATION INFORMATION |
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Data are available for 94 wells.  Data were collected between June 1994 and
August 1995.  Well location, depth, and screened interval information may be
obtained by retrieving the file 'gw1sta.txt'.




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| METHODS          |
--------------------


All samples were analyzed by the U.S. Geological Survey National Water Quality
Laboratory.  Samples were collected using the methods of Koterba and others
(1995).  Pesticides were determined by Gas Chromatography/Mass Spectrometry
using the method of Zaugg and others (1995) was used.




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| REFERENCES       |
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Koterba, M.T., Wilde, F.D., and Lapham, W.W., 1995, Ground-water data-collection
protocols and procedures for the National Water-Quality Assessment Program:
Collection and documentation of water-quality samples and related data: U.S.
Geological Survey Open-File Report 95-399, 113 p.


Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, K.M., 1995, Methods of
Analysis by the U.S. Geological Survey National Water Quality
Laboratory--Determination of pesticides in water by C-18 solid-phase extraction
and capillary-column gas chromatography/mass spectrometry with selected-ion
monitoring: U.S. Geological Survey Open-File Report 95-181, 49 p.