Stirred composite samples

Table 7. Ratio of high to low analytical replicates

and ratio of high to low means for field replicates

The extreme sampling heterogeneity observed

taken at five nodes of a 1.82-m-square grid.

in the discrete sampling was reduced by compos-

iting (Tables 8 and 9). Relative standard devia-

First field

Second field

Ratio of

tions (%RSD) for each of the three mixing proto-

Analytical replicate

sample

sample

high:low means

cols were all much less than those observed for

Row 2, column 3

the discrete samples. However, none of the mix-

1

0.0049

0.0059

ing protocols consistently produced what might

2

0.0063

0.013

be considered low %RSDs. These results empha-

Mean

0.0056

0.00945

1.69

Ratio of high:low rep.

1.29

2.20

size the extreme difficulty in sampling for this

heterogeneously distributed contaminant.

Row 4, column 3

1

0.0542

0.0636