Flow and contaminant dispersion in sub-neighborhood scales: Hermoso Park study

Motivated by oft-quoted health concerns about locally generated air pollutants, a comprehensive three-month field study was conducted in the Hermoso Park neighborhood of South Phoenix, Arizona to measure meteorology, turbulence and air pollutants in the winter of 2008-09. This study encompassed 5.5 square kilometers of mixed industrial/residential land use. The observational study, which had two particulate matter monitoring sites in the neighborhood and a third at a nearby control site, was augmented by regional (MM5/SMOKE/CMAQ) and micro-scale (QUIC, AERMOD, ENVI-met) modeling to map pollutant concentrations on scales of 4x4 km down to 5x5 m. Specialized meteorological measurements were made with a tethered balloon (up to 100 m) and with a 10 meter tower instrumented with ultrasonic anemometers, radiometers, and thermocouples. Specialized speciation studies were also undertaken. This work revealed that (i) the (PM₁₀) concentrations have steep gradients at the micro-scale, dictated by local emissions, the speed and direction of surface layer air flow, and the degree of stratification, (ii) turbulence in the roughness sub-layer/constant flux layer generally scales with the mean velocity, (iii) local emissions contribute 20% to the neighborhood's (PM₁₀) concentrations, with the remainder coming from transported urban emissions, (iv) within the neighborhood (PM₁₀) concentrations tend to be highest in the northeast because of a sand-and-gravel operation, while all residents in homes along major arterial streets are exposed to elevated concentrations, and (v) two major industrial fires in the last 20 years left no residual chemical signatures in the topsoils.