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Chemical Analyses: Solids: Organic Contaminants
Modern industrialized societies have developed thousands of synthetic
organic compounds for thousands of uses. Included are plastics,
lubricants, refrigerants, fuels, solvents, pesticides and preservatives.
These contaminants enter the natural environment through accidental
leakage and spills, such as leaking underground storage tanks, or
through planned spraying or other treatments, such as application
of pesticides to agricultural land. Synthetic organic chemicals
can be found in virtually every corner of our environment, including
soil, groundwater, surface water, plants, and our bodies. They have
harmful environmental effects that may inhibit or kill soil organisms,
thereby undermining the balance of the soil community. In addition,
any number of organisms can contact, inhale, or ingest organic chemicals
that have entered waterbodies, volatilized in the air, been taken
up by vegetation, or remain in the soil.
Organic chemical contamination is a widespread problem around the
world and can commonly be a contamination factor at mine sites.
Underground storage of fuels for operation of equipment at mine
sites may be a source of organic contamination. Many storage tanks
have been found to leak allowing organic chemicals to leach into
soil and eventually into groundwater which transports the chemicals
to streams, rivers, agricultural fields, and drinking water sources
where the chemicals can be contacted, inhaled or ingested by fish,
animals, and humans.
Concentrations of different organic chemicals in soil, water and
plants are found by using gas chromatography (GC). Samples are heated
which volatilizes the organic chemicals into the gaseous state.
A small sample of the gaseous mixture is injected into a stream
of carrier gas that is passed through a GC column where the temperature
is maintained at a selected level so that each gas to be determined
moves through the column at a different rate (so that each gas under
analysis has a unique retention time within the column). The stream
of gas is passed through a detector that measures some property
of the gas stream and transmits this information to a recorder that
traces out the response of the detector as a function of time on
a chart called a chromatogram. The chart will have peaks at different
retention times and each retention time is specific to a certain
organic compound. To determine the concentrations of the different
contaminants, the area under each peak is compared to the area under
the peaks of known concentrations of each given contaminate. Many
samples can be measured easily using gas chromatography. Automated
sampling has increased the ease of sampling significantly since
samples do not have to be done one by one by a technician rather,
many samples can be placed in an "autosampler" and samples can be
analyzed without direct supervision. For more information on gas
chromatography, see Page
et al. (1982).
Chemical
Analysis | Physical
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