Organic Matter in Rivers: The Crossroads between Climate and Water Quality

• Main Author: Davisson, M L
• Language: unknown
• Published: 2021
• Subjects: 54 ENVIRONMENTAL SCIENCES; CARBON 13; CLIMATES; DRINKING WATER; MISSOURI RIVER; ORGANIC MATTER; OXYGEN 18; PLANTS; RANGELANDS; RIVERS; SURFACE WATERS; WATER CHEMISTRY; WATER QUALITY; Arctic; St. Louis
• Online Access: http://www.osti.gov/servlets/purl/15005984; https://www.osti.gov/biblio/15005984

All surface waters in the world contain dissolved organic matter and its concentration depends on climate and vegetation. Dissolved organic carbon (DOC) is ten times higher in wetlands and swamps than in surface water of arctic, alpine, or arid climate. Climates of high ecosystem productivity (i.e., tropics) typically have soils with low organic carbon storage, but drain high dissolved organic loads to rivers. Regions with lower productivity (e.g. grasslands) typically have high soil carbon storage while adjacent rivers have high DOC contents. Most DOC in a free-flowing river is derived from leaching vegetation and soil organic matter, whereas in dammed rivers algae may comprise a significant portion. Water chemistry and oxygen-18 abundance of river water, along with radiocarbon and carbon-13 isotope abundance measurements of DOC were used to distinguish water and water quality sources in the Missouri River watershed. Drinking water for the City of St. Louis incorporates these different sources, and its water quality depends mostly on whether runoff is derived from the upper or the lower watershed, with the lower watershed contributing water with the highest DOC. During drinking water chlorination, DOC forms carcinogenic by-products in proportion to the amount of DOC present. This has recently led the USEPA to propose federal regulation standards. Restoration of natural riparian habitat such as wetlands will likely increase DOC concentrations in river water.