Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America
Article first published online: 23 MAY 2013
©2013. American Geophysical Union. All Rights Reserved.
Global Biogeochemical Cycles
Volume 27, Issue 2, pages 492–504, June 2013
How to Cite
2013), Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America, Global Biogeochem. Cycles, 27, 492–504, doi:10.1002/gbc.20044., , , , and (
- Issue published online: 25 JUL 2013
- Article first published online: 23 MAY 2013
- Accepted manuscript online: 25 APR 2013 08:13AM EST
- Manuscript Accepted: 8 APR 2013
- Manuscript Revised: 20 MAR 2013
- Manuscript Received: 16 OCT 2012
- National Aeronautics and Space Administration. Grant Number: NNX09AU89G and NNH04AA62I
 Understanding the processes controlling the transfer and chemical composition of dissolved organic carbon (DOC) in freshwater systems is crucial to understanding the carbon cycle and the effects of DOC on water quality. Previous studies have identified watershed-scale controls on bulk DOC flux and concentration among small basins but fewer studies have explored controls among large basins or simultaneously considered the chemical composition of DOC. Because the chemical character of DOC drives riverine biogeochemical processes such as metabolism and photodegradation, accounting for chemical character in watershed-scale studies will improve the way bulk DOC variability in rivers is interpreted. We analyzed DOC quantity and chemical character near the mouths of 17 large North American rivers, primarily between 2008 and 2010, and identified watershed characteristics that controlled variability. We quantified DOC chemical character using both specific ultraviolet absorbance at 254 nm (SUVA254) and XAD-resin fractionation. Mean DOC concentration ranged from 2.1 to 47 mg C L−1 and mean SUVA254 ranged from 1.3 to 4.7 L mg C−1 m−1. We found a significant positive correlation between basin wetland cover and both bulk DOC concentration (R2 = 0.78; p < 0.0001) and SUVA254 (R2 = 0.91; p < 0.0001), while other land use characteristics were not correlated. The strong wetland relationship with bulk DOC concentration is similar to that found by others in small headwater catchments. However, two watersheds with extremely long surface water residence times, the Colorado and St. Lawrence, diverged from this wetland relationship. These results suggest that the role of riverine processes in altering the terrestrial DOC signal at the annual scale was minimal except in river systems with long surface water residence times. However, synoptic DOC sampling of both quantity and character throughout river networks will be needed to more rigorously test this finding. The inclusion of DOC chemical character will be vital to achieving a more complete understanding of bulk DOC dynamics in large river systems.