Regenerative stormwater conveyance (RSC) for reducing nutrients in urban stormwater runoff depends upon carbon quantity and quality

Shuiwang Duan; Paul M Mayer; Sujay S Kaushal; Barret M Wessel; Thomas Johnson

doi:10.1016/j.scitotenv.2018.10.197

Regenerative stormwater conveyance (RSC) for reducing nutrients in urban stormwater runoff depends upon carbon quantity and quality

Sci Total Environ. 2019 Feb 20:652:134-146. doi: 10.1016/j.scitotenv.2018.10.197. Epub 2018 Oct 16.

Authors

Shuiwang Duan¹, Paul M Mayer², Sujay S Kaushal³, Barret M Wessel⁴, Thomas Johnson⁵

Affiliations

¹ National Research Council Postdoctoral Research Associate, Washington, DC, United States of America; Department of Geology, University of Maryland, College Park, MD, United States of America. Electronic address: sduan@umd.edu.
² USEPA, National Health and Environmental Effects Research Laboratory, Corvallis, OR, United States of America.
³ Department of Geology, University of Maryland, College Park, MD, United States of America.
⁴ Department of Environmental Science and Technology, University of Maryland, College Park, MD, United States of America.
⁵ USEPA, National Center for Environmental Assessment, Washington, DC, United States of America.

Abstract

Regenerative stormwater conveyance (RSC), a relatively new stormwater management approach, is extensively implemented throughout the mid-Atlantic for nutrient control, but little is known of its pollutant reduction capabilities and controlling factors. This study examined effects of organic carbon (C) quantity and quality on stream water quality and nutrient retention at two RSCs near Annapolis, Maryland, USA by comparing longitudinal changes in water quality at paired restored and unrestored stream reaches, and conducting lab experiments simulating RSC processes. Results showed that RSCs consistently had lower dissolved oxygen saturation (DO%) and pH relative to nearby unrestored streams, probably due to release of labile dissolved organic carbon (DOC). At one RSC, with high nitrate (NO₃^-) inputs, retention of N (16-37%) and release of DOC (18-54%) were observed with the highest retention of N during summer, and the rates of N retention and DOC release were larger than that of the adjacent unrestored tributary (N: 5-8%, DOC: <18%). At another RSC site with lower NO₃^- concentrations, N retention and DOC release were not apparent. Mesocosm experiments showed that NO₃^- retention varies with organic C quantity and quality depending on incubating temperature; retention of total N did not increase with organic C due to release of other N species (e.g., organic N). Lab mesocosms showed an increase in the release of soluble reactive phosphorus (SRP) with increasing organic C quantity and quality. However, field measurements did not show any evidence of SRP release at RSCs. The changes in SRP concentrations in streams seemed to be a function of iron levels and leaf litter inputs, but control factors for SRP warrant further investigation. This study suggests that RSC as a restoration approach may be effective for reducing N depending upon C quantity and quality as well as water temperature and N levels.

Keywords: Dissolved oxygen; Nitrogen; Organic matter; Phosphorus; Regenerative stormwater conveyance.

Published by Elsevier B.V.

Grants and funding

EPA999999/Intramural EPA/United States