Identifying and Quantifying the Impacts of Advected North African Dust on the Concentration and Composition of Airborne Fine Particulate Matter in Houston and Galveston, Texas

Abstract

Every summer, large-scale dust plumes emerge from the west coast of North Africa, cross the Atlantic, enter the Caribbean Basin, and on occasion pass over the southern United States. We show that such dust events significantly increase the concentration and alter the chemical composition of ambient fine particulate matter (PM 2.5 ) in southern Texas. Between 1 August and 13 September 2014, PM 2.5 was sampled daily at Clinton Drive, an industrial location in Houston, and at Galveston located on the Gulf of Mexico coast that is not directly/significantly impacted by local and regional pollution sources. Between 17-25 August, average PM 2.5 concentrations nearly doubled when a large dust-laden African air mass moved through the region. Using ground-based measurements, satellite observations, and modeling tools, we demonstrate that this massive influx of mineral dust greatly reduced the relative abundance of pollutants in Houston where aerosols are otherwise dominated by local and regional emissions. Chemical mass balance modeling estimated that African dust contributed 19-48% of PM 2.5 during the 9-day dust episode. Moreover, African dust was present throughout the measurement period even on days outside the main dust event contributing an estimated~8% of PM 2.5 which suggests that it may be a normal summertime component in this region. These measurements agree closely with inferences of "fine dust" based on a generic soil composition in the IMPROVE (National Interagency Monitoring of Protected Visual Environments) network. Our detailed protocol supports the conclusion that African dust affects a wide region of the South, Southeast, and East Coast United States.

Coupling Sr–Nd–Hf Isotope Ratios and Elemental Analysis to Accurately Quantify North African Dust Contributions to PM2.5 in a Complex Urban Atmosphere by Reducing Mineral Dust Collinearity

“…Previous studies of mineral dust elemental composition at this Barbados site show that for most elements, the composition is consistently very similar to that of upper-crust abundances and is relatively constant from year to year . Representative urban PM 2.5 was sampled from Clinton Drive, Houston (29.734N, 95.258W), which is surrounded by many industrial complexes, residential neighborhoods, and major roadways and has been the site of several previous PM investigations. ,,, The sampling campaign was designed to characterize two dust outbreaks in the year 2017 by capturing the same air masses in Barbados and Houston on both occasions after carefully tracking them using satellite and software products. For episode 1, two samples were collected in Barbados: one was integrated over 3 days to capture an entire outbreak (25–28 June) and one daily background sample immediately after the active event (28–29 June) and six daily samples at Houston spanning 28 June–04 July.…”

“…It is imperative to determine the sources and composition of airborne particulate matter (PM) in metropolitan areas to better understand its human health impacts, comply with regulations, and formulate policies and plans to control its concentrations. − Primary PM in urban atmospheres is typically a complex mixture of aerosols locally emitted by soil and road dust resuspension, industrial and construction activities, and automobiles − that can also be seasonally impacted by long-range transport. ,− One example of the latter is dust from the Sahara–Sahel region that, being the largest contributor to global dust flux, can substantially add to the aerosol burden already facing population centers in Europe ,, and the south and southeastern United States ,,, exacerbating concerns related to health, , regional haze, and regulatory compliance. Importantly, governments allow contributions from exceptional PM events that are not reasonably controllable or preventable to be excluded from regulatory decisions and actions.…”

“…Significant uncertainties are introduced during source apportionment of primary PM when potential tracers are coemitted by multiple sources or there is overlap in the composition of potential sources, especially when allocating low mass contributions. , For example, it is difficult to separate North African dust and non-African local soil at receptor sites since they both represent crustal material consequently possessing similar elemental composition. ,, Another concern is dust emanating from construction activities, which is composed largely of mineral materials lacking unique markers, , thereby leading to unreliable results when using receptor-based source apportionment models.…”

Characterizing and Quantifying African Dust Transport and Deposition to South America: Implications for the Phosphorus Budget in the Amazon Basin

“…The residue is ascribed to mineral dust. Elemental analyses of African dust (Arimoto et al, 1995; Bozlaker et al, 2017, 2019; Trapp et al, 2010) yield concentrations of major (and many minor) elements close to those of average crustal materials (Rudnick & Gao, 2003). See Text S1 for a detailed description of the sampling and analysis protocol.…”

Dust storm simulation over the Sahara Desert (Moroccan and Mauritanian regions) using HYSPLIT

“…Bozlaker et al, 2013 state that during the Saharan episode in 2008, the total dust contribution for PM10 increased by 85% in Houston, Texas, which shows a dominance of the transported PM10 particles from Sahara during dust episodes. Also, Bozlaker et al, 2019 found dust contributions of19% to 48% of PM2.5 during the 9‐day dust episode in 2014 to African dust. In addition, the results of the cluster analysis point out a number of source regions in the western Sahara that contributes to the rise in PM10 concentrations in the Southern Coast of the United States, such as Bir Anzarane Morocco, Nouakchott and Tichit Mauritania and Bordj Badji Mokhtar Algeria.…”