An increase in the slope of the concentration-discharge relation for total organic carbon in major rivers in New England, 1973 to 2019

Thomas G Huntington; Michael E Wieczorek

doi:10.1016/j.scitotenv.2021.146149

An increase in the slope of the concentration-discharge relation for total organic carbon in major rivers in New England, 1973 to 2019

Sci Total Environ. 2021 Jul 15:778:146149. doi: 10.1016/j.scitotenv.2021.146149. Epub 2021 Mar 2.

Authors

Thomas G Huntington¹, Michael E Wieczorek²

Affiliations

¹ U.S. Geological Survey, New England Water Science Center, 196 Whitten Rd., Augusta, ME 04330, USA. Electronic address: thunting@usgs.gov.
² U.S. Geological Survey, Maryland-Delaware-D.C. Water Science Center, 5522 Research Park Drive, Catonsville, MD 21228, USA. Electronic address: mewieczo@usgs.gov.

PMID: 33714100
DOI: 10.1016/j.scitotenv.2021.146149

Abstract

The mobilization and transport of organic carbon (OC) in rivers and delivery to the near-coastal ocean are important processes in the carbon cycle that are affected by both climate and anthropogenic activities. Riverine OC transport can affect carbon sequestration, contaminant transport, ocean acidification, the formation of toxic disinfection by-products, ocean temperature and phytoplankton productivity. There have been many studies reporting temporal trends in OC concentrations in comparatively small streams with minimal anthropogenic influences but there have been fewer studies on larger rivers and fewer still that have investigated changes in OC concentration-discharge (C-Q) relations. This study examined changes in C-Q relations for total organic carbon (TOC) from 1973 to 2019 in 8 rivers in New England, USA. TOC concentrations declined in all rivers, and in most rivers, and in most seasons, the slope of the C-Q relation increased between 1973 to 1995 and 1996 to 2019. The increase in C-Q slope between periods may be related to changes in the magnitude of TOC sources. The most likely sources to have changed are wastewater inputs, urban runoff, production through photosynthesis in aquatic systems, and runoff from agricultural and forestry practices. Changes in wetland abundance and changes in sulfate concentrations can be ruled out as drivers of the observed changes in C-Q.

Keywords: Carbon sources in rivers; Concentration-discharge relation; Land cover change; Long-term water quality time series; Seasonal variation in water quality; Weighted regressions on time, discharge, and season model (WRTDS).