Traps, Mistakes, and Errors - Field Sampling: Principles and Practices in Environmental Analysis - page 285

Horizons Not noting changes in horizons and direction of movement

Project notebook Not recording all observations in the field notebook

Safety Two aspects

1. Not following safety rules
2. Not operating and maintaining equipment safely

Sample handling Not handling samples in the prescribed manner

11.6. ANALYZING OR SAMPLING FOR THE WRONG COMPONENT

An ammonia spill occurs in an open field. The weather and soil are warm and there is a
gentle misting rain each evening keeping the soil moistened at field capacity. Several
weeks after the spill, soil and water samples are taken. Ammonia levels are found to be at
acceptable levels and so the assumption is made that there should be no concern about the
spilled ammonia. It is obvious that much less ammonia has been spilled than was
reported. A week after the sampling, analysis, and declaration that no problem exists,
several babies in nearby houses that use well water for drinking come down with blue
baby syndrome [3]. Could there be a connection?
Under the soil and environmental conditions described above ammonia is rapidly
oxidized, first to nitrite and then to nitrate, which subsequently leaches into the
groundwater. Under the conditions described soil bacteria can convert kg of ammonia to
nitrate per day. Thus in a very short period of time the level of ammonia is back to its
background level. In this case analysis should be not only for ammonia, but also for
nitrate.
A company is accused of dumping chromate, specifically chromate(VI), which has
many adverse health affects, on a field. Soil analysis shows only the occurrence of small
amounts of Cr(VI). In this case it is important to know that Cr(VI) is quickly converted to
Cr(III) in soil, and so this is the species for which the soil should be analyzed.
The types of changes illustrated above can also occur with organic contamination. For
example, a monitoring well at a landfill that had been closed and capped years before was
observed to have rapidly increasing levels of vinyl chloride, which had some other
contaminants associated with it. It was hypothesized that illegally dumped or lost drums
of vinly chloride were the source of this chemical in the wells. However, all compounds
were found to be chemical and biological decomposition products of solvent mixtures in
decomposing drums 10 ft deep in the landfill.

11.7. ANTAGONISMS AND INTERFERENCES

There are numerous antagonisms between analytes and between analytes and matrices.
For instance, it is possible for two different compounds to elute from a gas
chromatograph column at the same time, thus obscuring the occurrence of both
compounds. Often a matrix will mask the occurrence of an analyte, making it appear not