TEXT 5 78 ENVIRONMENTAL CHEMISTRY

ENVIRONMENTAL CHEMISTRY
Environmental chemistry is the scientific study of the chemical and biochemical
phenomena that occur in natural places. It should not be confused with green chemistry,
which seeks to reduce potential pollution at its source. It can be defined as the study of the
sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water
environments; and the effect of human activity and biological activity on these.
Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and
soil chemistry, as well as heavily relying on analytical chemistry and being related to
environmental and other areas of science. Environmental chemistry involves first
understanding how the uncontaminated environment works, which chemicals in what
concentrations are present naturally, and with what effects. Without this it would be
impossible to accurately study the effects humans have on the environment through the
release of chemicals. Environmental chemists draw on a range of concepts from chemistry
and various environmental sciences to assist in their study of what is happening to a chemical
species in the environment. Important general concepts from chemistry include understanding
chemical reactions and equations, solutions, units, sampling, and analytical techniques.
Contamination. A contaminant is a substance present in nature at a level higher than
typical levels or that would not otherwise be there. This may be due to human activity. The
term contaminant is often used interchangeably with pollutant, which is a substance that has a
detrimental impact on the surrounding environment. Whilst a contaminant is sometimes
defined as a substance present in the environment as a result of human activity, but without
harmful effects, it is sometimes the case that toxic or harmful effects from contamination only
become apparent at a later date. The "medium" (e.g. soil) or organism (e.g. fish) affected by
the pollutant or contaminant is called a receptor, whilst a sink is a chemical medium or
species that retains and interacts with the pollutant.
Environmental indicators. Chemical measures of water quality include dissolved
oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total
dissolved solids (TDS), pH, nutrients (nitrates and phosphorus), heavy metals (including
copper, zinc, cadmium, lead and mercury), and pesticides.
Applications. The major application areas of environmental chemistry are as below.
Risk or hazard assessments of environmental impact

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