Gravimetric and Number Distributions of Urban PM Residuals from Urban Maintenance Practices

Abstract

Particulate matter (PM) recovery from street sweeping (SS), catch basin (CB), and unit operation (UO) is essential for sustainability of these urban hydrologic functional units (HFUs). PM inventory in HFUs is of increasing interest. PM granulometry and transformations thereof are needed to examine loads and export from HFUs. This study uniquely examines transformation of PM distributions recovered from SS, CB, and UO, representing serial HFUs coupled from up- to downstream in drainage systems. HFUs are also indexed to land uses (residential, highway, commercial) across Florida (n=470 samples). Results indicate the dominant PM mass is sand-size from 425 to 1,000 μm. Gravimetrically, particle size distributions (PSDs) are represented by a cumulative gamma distribution (CGD) (Radj2:0.98–0.99). Particle number density (PND) is represented by a power law model (PLM) with a log-log transformation (R2:0.86–0.89). Results indicate UOs (n=163) as a downstream HFU had PSDs that were less heterodisperse and finer than CB (n=155) and SS (n=152). PNDs are statistically consistent between SS, CB, and UO, given the transport of suspended PM from pavement through UOs, which cannot capture suspended PM. PM from SS is statistically more enriched in the suspended and sediment fractions than CBs and UOs due to export from these HFUs. Land use has been hypothesized as a factor impacting PSDs. However, results indicate that the impact of land use is not statistically significant for recovered PSDs. These findings are a useful resource of PM granulometry for urban PM residuals and facilitate implementation of more sustainable drainage systems.