Effects of Urban Stormwater Control Measures on Denitrification in Receiving Streams

Abstract

Urban areas are increasingly adopting the use of ecologically-based technologies for stormwater management to mitigate the effects of impervious surface runoff on receiving water bodies. While stormwater control measures (SCMs) reduce runoff, their ability to influence ecosystem function in receiving streams is not well known. To understand the effect of SCMs on net ecosystem function in stream networks, we measured sediment denitrification in four streams across a gradient of urban and suburban residential development in Charlotte, NC. We evaluated the influence of SCM inputs on actual (DNF) and potential (DEA) denitrification activity in stream sediments at the SCM-stream confluence to quantify microbial processes and the environmental factors that control them. DNF was variable across sites, ranging from 0–6.60 mg-N·m−2·h−1 and highly correlated with in-stream nitrate (NO3-N) concentrations. Sites with a greater impervious area showed a pattern of significantly higher DEA rates upstream of the SCM compared to downstream, while sites with less imperviousness showed the opposite trend. We hypothesize that this is because of elevated concentrations of carbon and nitrogen provided by pond and wetland outflows, and stabilization of the benthic habitat by lower peak discharge. These results suggest that SCMs integrated into the watershed have the potential to create cascading positive effects on in-stream nutrient processing and thereby improve water quality; however, at higher levels of imperviousness, the capacity for SCMs to match the scale of the impacts of urbanization likely diminishes.

Variability of Potential Soil Nitrogen Cycling Rates in Stormwater Bioretention Facilities

“…The measurement of N nit and N min via chloroform fumigation incubation induces turnover of the microbial biomass as a supply of organic N, but there are no supplemental additions of nutrients above in situ levels that promote maximum nitrification and mineralization. As a result, N nit and N min are likely more sensitive to changes to soil chemistry and physical properties and allow us to approximate current in situ processes and conditions [66].…”

Hyporheic exchanges due to channel bed and width undulations

“…Mindful design of PCRE is limited as of yet, but advocated by academics due to its selfsustainability based on flume, field, and numerical modeling studies (e.g., Jackson et al 2015, Repetto and Tubino 2001, Wheaton et al 2010. While studies have investigated hyporheic and denitrification effects in reaches with constructed riffles and pools (Mendoza-Lera and Datry 2017, Merill and Tonjes 2014, Rivers et al 2018), care has not been taken to isolate the PCRE configuration. Overall, both PERC and PCRE configurations are widespread in nature and increasingly used in river engineering, warranting a better understanding of their hyporheic flow processes.…”

Research Progress of Urban Floods under Climate Change and Urbanization: A Scientometric Analysis

“…Global urbanization and the increasing frequency and intensity of extreme weather events as a result of climate change are serious problems for urban floods [1][2][3][4]. Moreover, they have caused massive casualties and economic losses [5,6].…”