Analysis of Organic Pollutants in Water
Organic pollutants in water can harm the environment and also pose health risks for humans. Organic pollutants pose special risks because they are often not naturally broken down and can remain in water sources for decades or longer. The analysis of organic pollutants in water allows managers to assess the quality and safety of water sources.
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Persistent Organic Pollutants
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Some organic pollutants are byproducts of industrial production. The United States Environmental Protection Agency (EPA) monitors and analyzes organic pollutants in water. The EPA has established a list of a "dirty dozen" particularly widespread and persistent organic pollutants (POPs). Part of the EPA's mandate is to identify where these pollutants occur in water resources and to contain or mitigate POPs.
The Dirty Dozen
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Some pesticides have been identified as persistent organic pollutants. The POPs include intentionally produced chemicals such as pesticides as well as industry or combustion by-products. The dirty dozen are aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, PCBs, dioxins and furans. For information on other organic compounds the EPA analyzes in water, see Resources.
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Methods of Analysis
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EPA laboratories in Cincinnati, Ohio and Athens, Georgia investigated analytical methods to analyze organic pollutants in water based on gas chromatography separation of the pollutants and mass spectrometer identification and quantification. The research results were published as the EPA's test methods 624 and 625 for the standard analysis of organic pollutants in municipal and industrial effluent.
Gas Chromatography
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Gas chromatography separates organic pollutants for further analysis. The researcher injects a sample into the gas chromatography instrument. The instrument heats the sample to a gas and injects it into the gas chromatography tube or column. As the sample travels the length of the column, the different organic molecules condense and liquefy and then vaporize as a gas again. As a liquid, the molecules stick to the column, but as a gas, they travel through the column quickly. Different pollutants have different ratios of gas to liquid, so they each travel through the column at different speeds. The separated pollutants are then analyzed by mass spectrometry.
Mass Spectrometry
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A mass spectrometer ionizes a sample and shoots it through an electric field. The electric field bends the path (trajectory) of lighter molecules more than that of heavy molecules. The sample strikes a detector at a certain position based on its mass. This method identifies and quantifies organic pollutants in water after they have been separated by gas chromatography. The combination of gas chromatography and mass spectrometry give researchers complete information on the type of organic pollutants in a sample and the concentration of each pollutant in the sample.
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References
Resources
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