Phase partitioning, transport and sources of Benzotriazole Ultraviolet Stabilizers during a runoff event

Boluwatife Awonaike; Ying Duan Lei; Abha Parajulee; Frank Wania

doi:10.1016/j.wroa.2021.100115

Phase partitioning, transport and sources of Benzotriazole Ultraviolet Stabilizers during a runoff event

Water Res X. 2021 Aug 19:13:100115. doi: 10.1016/j.wroa.2021.100115. eCollection 2021 Dec 1.

Authors

Boluwatife Awonaike¹, Ying Duan Lei¹, Abha Parajulee¹, Frank Wania¹

Affiliation

¹ Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Ontario M1C 1A4, Canada.

Abstract

Benzotriazole Ultraviolet Stabilizers (BT-UVs) are ubiquitous in the environment, given their wide use as additives in consumer products. Their bio-accumulative and toxic properties are increasingly being scrutinised, evinced by the recent proposition to add UV328 to the Stockholm Convention on Persistent Organic Pollutants. Here, we measured concentrations of six BT-UVs in the dissolved and particulate phases of stream water collected from an urban and rural stream during a runoff event. Under baseflow conditions, the less hydrophobic BT-UVs were present at low concentrations in the dissolved phase, while much higher loads of particulate BT-UVs occurred during stormflow, especially in the urban creek. Time-weighted average BT-UV concentrations were up to 4 times higher in the urban than in the rural creek. BT-UVs were found to be prevalent in water obtained from laundering textiles, which plausibly constitutes a major portion of domestic wastewater, and can serve as a BT-UV source to aquatic waterways. However, the observed dilution of a sewage tracer during the run-off event suggests that unregulated wastewater seepage is not responsible for the high BT-UV loads in storm water. High levels of UV328 and UV234 were detected in a select few plastic debris items collected from the urban watershed and in artificial turf grass, respectively. Whereas this may allow for the leaching of those BT-UVs into the creek, most plastic debris is more likely a sink than a source of BT-UVs. The observed input of particle-bound BT-UVs at the onset of the rain event indicates that most of the BT-UVs reach the creek with contaminated particles that had built up on surfaces during the antecedent dry period. UV328 was the dominant BT-UV in those particles. If such particle build-up occurs on road surfaces, it may suggest that the use of UV328 in automotive applications contributes to their presence in urban storm water.

Keywords: Plastics; Precipitation; Ultraviolet stabilizers; Urban runoff.