Runoff of the Tire-Wear Compound, Hexamethoxymethyl-Melamine into Urban Watersheds

Abstract

Hexamethoxymethyl-melamine (HMMM) is used as a crosslinking agent in resins and plastics and in the manufacture of tires. In the present study, surface water samples were collected from two rivers adjacent to high traffic highways in the Greater Toronto Area in Ontario, Canada. Composite samples collected from the Don River and Highland Creek during rain events and a period of rapid snowmelt were preconcentrated using solid phase extraction and analyzed using liquid chromatography with high-resolution mass spectrometry. Elevated concentrations (> 1 µg/L) of HMMM were detected in surface waters during rain events in October of 2019 and during snow melt in early March of 2020. There were lower average concentrations of HMMM detected during rain events in the winter and spring of 2020. Temporal profiles of changes in the concentrations of HMMM in composite samples collected every 3 h during a rain event in October 2019 closely corresponded to the hydrograph profiles at the sampling sites, with the HMMM concentrations peaking > 6 h after the peak in water levels. This work contributes to the literature showing that HMMM is a ubiquitous contaminant of urban watersheds and that runoff from roads is a vector for the transport of this compound into urban surface waters.

The Tire Wear Compounds 6PPD-Quinone and 1,3-Diphenylguanidine in an Urban Watershed

“…Samples were collected as part of a water quality monitoring program by the Ontario Ministry of Environment Conservation and Parks (MECP) using composite samplers, as previously described by Johannessen et al ( 2021a ). In brief, composite samples were collected in the fall of 2019, as well as in the winter and early spring of 2020.…”

“…Extraction was performed as described by Johannessen et al ( 2021a ) using Oasis hydrophilic-lipophilic balance (HLB) solid phase extraction (SPE) cartridges (6 cc, 500 mg) purchased from Waters (Milford, MA, USA). The cartridges were preconditioned with acetone, methanol, and pH neutral MilliQ water adjusted for pH with 3.0 M H 2 SO 4 .…”

“…The flow rate was 500 µL/min and the column was maintained at room temperature. The mobile phases and their gradients were as described by Johannessen et al ( 2021a , b ). In brief, the binary mobile phase consisted of Solvent A, MilliQ water (pH = 7) with 0.1% of formic acid, and Solvent B, methanol with 0.1% of formic acid.…”

“…The report of 6PPD-q as a highly toxic tire-derived chemical in urban streams prompted us to reinvestigate archived extracts from composite surface water samples collected from an urban watershed (i.e., Don River) in the GTA that is impacted by runoff from several multi-lane transportation corridors and other impermeable urban landscapes. Our previous analyses of these extracts from composite samples collected from the Don River showed that the levels of HMMM in the river followed the hydrological profile during major rain events, except there was a delay of several hours between the initiation of high flows in the river and the peak in the concentration of this tire-wear compound (Johannessen et al 2021a ). In the present study, we analyzed these archived samples for two additional tire-derived compounds, DPG and 6PPD-q.…”

“…Untreated road runoff is a significant source of these contaminants in the aquatic environment (Hou et al 2019 ). We recently showed that a tire cross-linking agent, hexamethoxymethylmelamine (HMMM) is transported during rain events from high traffic highways into urban surface waters in the Greater Toronto Area (GTA) of Canada (Johannessen et al 2021a ). This compound is transformed into numerous more waters-soluble transformation products (TPs) that are expected to readily partition into the aquatic environment (Alhelou et al 2019 , Johannessen and Parnis 2021 ), and we recently detected several of these TPs of HMMM in urban rivers in the GTA (Johannessen et al 2021b ).…”