Impact of Haboob Dust Storms on Air Quality in Phoenix, AZ

During the summer monsoon season, very intense dust storms, or haboobs, can occur in Arizona. These dust storms, characterized by a clear moving front can last from minutes to hours and have a substantial impact on local air quality in the Phoenix metropolitan area, evidenced by a sharp increase in particulate matter (PM) concentrations. These storms bring an influx of PM material and substantially impact local deposition fluxes.

During the monsoons seasons 2013 and 2014, background urban PM samples and the PM of haboob events (PM_2.5 and PM_>2.5) were collected on the Arizona State University Tempe Campus. Samples were analyzed for trace metals, organic and elemental carbon and organic molecular marker species such as polycyclic aromatic hydrocarbons (PAH) and sugars. This composition data will be discussed in conjunction with an analysis of the local air monitoring network data.

The PM₁₀ concentrations in these dust storms are typically on the order of 100s µg/m³ and can exceed 1,000 µg/m³ for short periods of times. PM_2.5 concentrations also increase typically by a factor 5-10 compared to pre-haboob conditions.

The chemical characterization shows that the dominant component of these dust storms is mineral dust, consistent with the formation mechanism of these storms as storm fronts entrain desert soil in monsoon storm outflows. However, chemical analysis also shows a general increase of all species, not only of the crustal component. In fact, elements typically associated with anthropogenic activities and sources, such as lead, cadmium, and antimony are also substantially increased in the fine particles during these events. This suggests a strong resuspension of urban and street dust. This observation is supported by organic molecular marker data, which also shows a substantial increase (e.g. factor of 5) for PAH in PM_2.5. The composition data will be further discussed relative to non-haboob dust events and background urban PM data.