Fate and Behavior of Pollutants in a Vegetated Pond System for Road Runoff

Abstract

Road runoff contains a variety of contaminants that threaten aquatic systems. Pollutant mitigation is therefore an important function of sustainable drainage systems such as vegetated ponds. Vegetated ponds have a variety of treatment mechanisms that potentially can remove different pollutants. However, design is predominantly based on “black box” approaches. This study monitored a swale and vegetated pond receiving road runoff over two years to investigate the interaction of various pollutant removal processes. Storm runoff, pond water, and sediments were monitored for general water quality, metals, hexane extractable hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). A non‐exponential “first flush” was apparent for biochemical oxygen demand, chemical oxygen demand, and solids with higher concentrations seen during the early stages of storms; however, for hydrocarbons and PAHs peak concentrations were often seen later in storm events. Due to interference from natural compounds, PAHs are probably more appropriate than hexane extracts for tracking runoff pollutant fate. Pyrene, despite having low concentrations in water, accumulated in soils and sediments (median = 850 µg/g). Naphthalene was more mobile, but was effectively removed in the pond. Metals had similar concentrations to other studies, with large removals of particularly Cu and Zn. However, metals exhibited different deposition patterns, with Zn and Cu accumulating in pond inlet sediments and Ni and Cr accumulating at the outlet. The different behaviors and fates of pollutants means that refining design guidance is difficult and requires consideration of how specific mechanisms may be enhanced for prioritizing removal of pollutants that pose the greatest risk.

Analysis of swale factors implicated in pollutant removal efficiency using a swale database

“…Technically, hydraulic processes of swale contribute to reduce both magnitude and volume of flows before potentially being discharged into either downstream drainage elements, such as inlet of sewers or other LID techniques (e.g., wet or dry pond), or grasslands (Lloyd et al 2001;Roinas et al 2014;Allen et al 2016;Xiao et al 2017). While stormwater flowing through the swale, a wide range of stormwater anthropogenic substances are candidate to be sequestered within the facility.…”

The effects of roadways on lakes and ponds: a systematic review and assessment of knowledge gaps

“…Though now seen as an obvious pollutant, it was not until the 21st century that road salt was seen as a major environmental issue, as investigators in past studies found it difficult to establish road salt as the point source contaminant (Judd 1970;Kattner et al 2000). There is very little doubt now that road salts are eventually flushed into lentic environments, where they cause geochemical changes to water and sediment quality, which in turn affects aquatic organisms (Roe and Patterson 2014;Roinas et al 2014). Our literature review found that road salt was the most investigated stressor on lakes and ponds (Fig.…”

“…The distribution and movement of metals into lakes was often via stormwater runoff, surrounding streams, or particles being captured in the atmosphere through road dust (Barbosa and Hvitved-Jacobsen 1999;Camponelli et al 2010;Jeong et al 2020). Concentrations of metals varied spatially within lakes (Rabajczyk et al 2011;Roinas et al 2014;Xu et al 2019). Zn and Cu accumulated in the inlet sediments of a pond, while Ni and Cr accumulated at the outlet (Roinas et al 2014).…”

“…Concentrations of metals varied spatially within lakes (Rabajczyk et al 2011;Roinas et al 2014;Xu et al 2019). Zn and Cu accumulated in the inlet sediments of a pond, while Ni and Cr accumulated at the outlet (Roinas et al 2014). Lake sediments are typically a sink for heavy metals but can act as a source if mobilized by salinity, pH changes, or redox condition changes, and impact the overall status of the lake (Gjessing et al 1984;Mayer et al 2008;Meriano et al 2009;Roinas et al 2014).…”

“…2). PAHs in lentic environments can come from a number of different sources such as soil runoff, agriculture, and industrial wastewater, but a significant source of PAHs in these environments can be sourced to road runoff (Li et al 2003;Chen et al 2004;Hijosa-Valsero et al 2016), with peak concentrations often measured after storm events (Roinas et al 2014). PAHs can also be transported atmospherically by road dust, and can be found in high concentrations 50 m from the road (Gjessing et al 1984).…”