plosives signatures at the surface were spatially het-

the two analysis times.* To test this hypothesis, 10

erogeneous.

archived soils were extracted using the protocol used

Of the sample extracts analyzed on site and also re-

at Fort Leonard Wood, then sequentially analyzed on

the same day by both GC-TID and GC-ECD. Table 3

turned to CRREL for analysis by GC-ECD (Method

shows the concentrations (g/kg) of 2,4-DNT and TNT

8095), only those that had an extract volume of 0.3 mL

obtained by these two methods of analysis. The good

or greater could be reanalyzed. This sample volume

agreement (low median %D) for both analytes is con-

limitation was necessary because of the capabilities of

sistent with the hypothesis that the discrepancy in the

the HP auto sampler used with the HP 6890 GC-ECD.

Table 2 shows the concentrations (g/kg) obtained for

TNT values for the Fort Leonard Wood samples was

due to TNT degradation during the time between on-

2,4-DNT, TNT, 4AmDNT, and 2AmDNT by both GC-

site and laboratory analysis (seven to 10 days).

TID and GC-ECD analysis for those sample extracts

that were analyzed both on site and in our laboratory.

Umatilla Chemical Depot

Also included in this table are the median and range of

Most of the samples analyzed on site at the Umatilla

the percent differences (%D) of the field results as com-

Chemical Depot were obtained during the character-

pared to the laboratory results. This comparison shows

ization of an area that had been used for the OB/OD of

that the median percent differences for 2,4-DNT,

2AmDNT, and 4AmDNT were less than 10%. The TNT

munitions. Furthermore, prior to the analysis by GC-

TID, several of the samples had been identified as hav-

values established in the field with GC-TID, however,

were biased high. One explanation for this discrepancy

is that TNT at these low concentrations (less than 250

g/kg) was not stable in the acetone extracts, therefore

*Personal communication, Marianne E. Walsh, Chemical

Engineer, CRREL, Hanover, New Hampshire, May 2000.

the TNT concentrations may have decreased between

Table 2. Comparison between GC-TID-1 field and GC-ECD laboratory (Method 8095) results for