In situ monitoring of internal water storage reveals nitrogen first flush phenomena, intermittent denitrification, and seasonal ammonium flushing

Adrienne G Donaghue; Naomi Morgan; Laura Toran; Erica R McKenzie

doi:10.1016/j.jenvman.2023.117957

In situ monitoring of internal water storage reveals nitrogen first flush phenomena, intermittent denitrification, and seasonal ammonium flushing

J Environ Manage. 2023 Sep 1:341:117957. doi: 10.1016/j.jenvman.2023.117957. Epub 2023 May 2.

Authors

Adrienne G Donaghue¹, Naomi Morgan², Laura Toran³, Erica R McKenzie⁴

Affiliations

¹ Temple University, Department of Civil and Environmental Engineering 1947, North 12 Street, Philadelphia, PA, 19122, United States. Electronic address: donaghue.adrienne@epa.gov.
² Temple University, Department of Earth and Environmental Science, 322B Beury Hall, Philadelphia, PA, 19122, United States. Electronic address: nmorgan1904@gmail.com.
³ Temple University, Department of Earth and Environmental Science, 322B Beury Hall, Philadelphia, PA, 19122, United States. Electronic address: laura.toran@temple.edu.
⁴ Temple University, Department of Civil and Environmental Engineering 1947, North 12 Street, Philadelphia, PA, 19122, United States. Electronic address: ermckenzie@temple.edu.

PMID: 37141724
DOI: 10.1016/j.jenvman.2023.117957

Abstract

Internal water storage (IWS) can be included in bioretention practices to increase storage capacity or promote denitrification-the microbial reduction of nitrate to nitrogen gas. IWS and nitrate dynamics are well studied in laboratory systems. However, the investigation of field environments, consideration of multiple nitrogen species, and determination between mixing versus denitrification is lacking. This study employs in situ monitoring (∼24 h duration) of water level, dissolved oxygen (DO), conductivity, nitrogen species, and dual isotopes of a field bioretention IWS system for nine storms events over a year period. Rapid peaks in IWS conductivity, DO, and total nitrogen (TN) concentrations occurred along the rising limb of the IWS water level and indicated a first flush effect. TN concentrations generally peaked during the first ∼0.33 h of sampling and the average peak IWS TN concentration (C_max = 4.82 ± 2.46 mg-N/L) was 38% and 64% greater than the average TN along the IWS rising and falling limb, respectively. Dissolved organic nitrogen (DON) and nitrate plus nitrite (NO_x) were the dominant nitrogen species of IWS samples. However, average IWS peak ammonium (NH₄⁺) concentrations August through November (0.28 ± 0.47 mg-N/L) demonstrated statistically significant shifts compared to February through May (2.72 ± 0.95 mg-N/L). Average lysimeter conductivity measurements were more than ten times higher February through May. The sustained presence of sodium observed in lysimeters, from road salt application, contributed to NH₄⁺ flushing from the unsaturated media layer. Dual isotope analysis showed denitrification occurred for discrete time intervals along the tail of the NO_x concentration profile and the hydrologic falling limb. Longer antecedent dry periods (17 days) did not correlate to enhanced denitrification but did correspond to more leaching of soil organic nitrogen. Results from field monitoring highlight the complexities of nitrogen management in bioretention systems. First flush behavior into the IWS suggests management to prevent TN export is most critical during the onset of a storm.

Keywords: Bioretention; Nature-based solution; Road salts; Sodium dispersion; Underdrains; Urban stormwater.

Published by Elsevier Ltd.

MeSH terms

Denitrification
Isotopes / analysis
Nitrates*
Nitrogen* / analysis
Oxygen
Seasons
Water

Substances

Nitrogen
Nitrates
Water
Isotopes
Oxygen