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Water 2017, 9(6), 383; doi:10.3390/w9060383

An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States

1
Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MA 20740, USA
2
Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA
3
Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China
*
Author to whom correspondence should be addressed.
Academic Editor: Thilo Hofmann
Received: 20 February 2017 / Revised: 25 May 2017 / Accepted: 25 May 2017 / Published: 29 May 2017
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Abstract

Analyses of environmental controls on riverine carbon fluxes are critical for improved understanding of the mechanisms regulating carbon cycling along the terrestrial-aquatic continuum. Here, we compile and analyze riverine dissolved organic carbon (DOC) concentration data from 1402 United States Geological Survey (USGS) gauge stations to examine the spatial variability and environmental controls of DOC concentrations in the United States (U.S.) surface waters. DOC concentrations exhibit high spatial variability in the U.S., with an average of 6.42 ± 6.47 mg C/L (Mean ± Standard Deviation). High DOC concentrations occur in the Upper Mississippi River basin and the southeastern U.S., while low concentrations are mainly distributed in the western U.S. Soil properties such as soil organic matter, soil water content, and soil sand content mainly show positive correlations with DOC concentrations; forest and shrub land have positive correlations with DOC concentrations, but urban area and cropland demonstrate negative impacts; and total instream phosphorus and dam density correlate positively with DOC concentrations. Notably, the relative importance of these environmental controls varies substantially across major U.S. water resource regions. In addition, DOC concentrations and environmental controls also show significant variability from small streams to large rivers. In sum, our results reveal that general multi-linear regression of twenty environmental factors can partially explain (56%) the DOC concentration variability. This study also highlights the complexity of the interactions among these environmental factors in determining DOC concentrations, thus calls for processes-based, non-linear methodologies to constrain uncertainties in riverine DOC cycling. View Full-Text
Keywords: dissolved organic carbon; spatial variability; terrestrial-aquatic continuum; general multi-linear regression dissolved organic carbon; spatial variability; terrestrial-aquatic continuum; general multi-linear regression
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Yang, Q.; Zhang, X.; Xu, X.; Asrar, G.R. An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States. Water 2017, 9, 383.

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