Date of Completion

8-4-2012

Embargo Period

1-31-2013

Open Access

Open Access

Abstract

Urban systems are impacted by changes in hydrology and water chemistry, altering their ability to mitigate detrimental impacts to coastal water bodies, particularly those that result from high volumes of stormwater runoff. The elevated level of impervious cover increases not only runoff but also contaminant loading of nutrients, metals, and road salt used for deicing in cold weather climates. Current stormwater management strategies, while focused on managing the changes in hydrology associated with urbanization, also are designed to mitigate the pollutant loading. Here we investigate the impact that road salt will have on nitrogen removal in roadside environments. Sediments were collected from a series of forested and roadside ponds and treated with a range of Cl- concentrations from 0-5000 mg/L for 96 hrs. Denitrification rates were measured by the isotope pairing technique using 15N-NO3-. Our results suggest that road salt inhibits denitrification in both roadside and forested ponds. The decrease in denitrification rates is lower for the roadside ponds which previously have been exposed to elevated concentrations of Cl- due to their proximity to roadways (m). Forested ponds demonstrated a greater decrease in denitrification rates suggesting that ponds that historically have not been exposed to Cl- are not able to adapt as quickly to increases in Cl-. At 5000 mg/L, denitrification rates in forested ponds decreased by three orders of magnitude from the baseline compared with a decrease of only two orders of magnitude in the roadside ponds. As development increases the impact to natural systems, the effectiveness of roadside ponds and stormwater detention ponds for mitigating nitrogen loading is critical to protect local and downstream water resources. Included is the necessity, as in the current investigation, to evaluate the synergistic impacts among pollutants in roadside environments.

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