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 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 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.

Concepts
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. Various environmental concepts include:

Contamination
A contaminant is a substance present in nature due to human activity, that would not otherwise be there. The term contaminant is often used interchangeably with pollutant, which is a substance that has a detrimental impact on the environment it is in. 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), biological oxygen demand (BOD), and pH.

Applications
Environmental chemistry is used by the Environment Agency (in England and Wales), the Environmental Protection Agency (in the United States), and other environmental agencies and research bodies around the world to detect and identify the nature and source of pollutants. These can include:
 * Heavy metal contamination of land by industry. These can then be transported into water flows and be taken up by living organisms.
 * Nutrients such as nitrate and phosphate leaching from agricultural land into water courses, which can lead to algal blooms and eutrophication.

Methods
Quantitative chemical analysis is a key part of environmental chemistry.