Organic Compounds in Groundwater

Virtually all natural waters contain at least some amounts of organic compounds. However, as human impact on the environment increases, the concentration of organic compounds, such as solvents or petroleum products, in the hydrosphere has increased in many places. Consequently, many aquifers experience a degradation of groundwater quality, and there is strong concern how to protect this valuable natural resource effectively from further contamination.

Organic compounds in groundwater can be of natural or anthropogenic origin. Naturally occurring organic compounds in terrestrial water include carbohydrates (sugars and cellulose), lipids (neutral fats), and proteins. The building blocks of proteins are amino acids, whereas functional proteins that act as biological catalysts are enzymes. Proteins are biopolymers that can form complexes with other organic compounds. Such compounds include tannins, which are phenolic compounds that occur naturally in bark, wood, leaves, or roots of many plants. The presence of elevated tannin levels in water results in a yellowish-brown discoloration. The parameter, dissolved organic carbon (DOC), is a commonly used measure for the concentration of organic compounds in aqueous solution. DOC is the fraction of total organic carbon (TOC is all carbon atoms covalently bonded in organic molecules) in water that passes through a 0.45 micron pore-diameter filter. Typical DOC concentrations for ground water range from a few micrograms to several 10 mg per liter and more. DOC concentrations depend on various factors, such as climate, soil and vegetation coverage, and land use.

Keywords: dissolved organic carbon (DOC); total organic carbon (TOC); polynuclear aromatic hydrocarbons (PAH); polychlorinated biphenyls (PCB); total petroleum hydrocarbons (TPH); volatile organic compounds (VOC); semivolatile organic compounds (SVOC); maximum contaminant levels (MCL); tetrachloroethene (PCE); trichloroethene (TCE); nonaqueous phase liquid (NAPL); light nonaqueous phase liquid (LNAPL); dense nonaqueous phase liquid (DNAPL)