Quantification and Characterization of Particulate Matter Generated from Unpaved Roads in the Oil Development Area of Western North Dakota

Abstract. Western North Dakota, USA is experiencing economic growth due to the rapid oil development. The increased oil activities are also causing heavy vehicle traffic on the unpaved roads. Unpaved road traffic may create coarse particulate matter (PM₁₀) and fine particulate matter (PM_2.5), and Total Suspended Particles (TSP) emissions, and deposit them in adjacent areas. These PMs may affect human and animal health, and soil quality. To address this issue, a study was conducted to characterize and quantify PM₁₀, PM_2.5, and TSP generated from unpaved roads surrounding oil development areas. Particulate matter concentrations were measured using miniVOL^TM portable air samplers (Air Metrics, Springfield, OR, USA) at three pre-selected distances from the road using Federal Equivalent Method. Scanning Electron Microscopy (SEM) was done on dust samples to find out the elemental compositions and X-Ray Diffraction (XRD) to find minerals present. Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) was performed on soil samples taken from the same location as dust samples to determine the elemental composition. The PM₁₀ concentration was 22.39 ± 8.81 µg/m³ for the road that was treated regularly, whereas it was 91.87 ± 54.40 µg/m³ from a loose gravel road and not treated. The PM_2.5 concentration was 13.86 ± 5.82 µg/m³ at the first site, 23.73 ± 9.45 µg/m³ at the second site. TSP measurement was taken at another site to see the effect of treatments (control brine, magnesium chloride) and it was observed that magnesium chloride applied section accumulated minimal TSP concentration. SEM analysis of dust identified the presence of several minerals (i.e., silica, soot, aluminosilicates groups, biological particles, etc.), but nothing related to health concern. ICP-MS analysis of soil revealed that most of the metals concentration were below the reference level recommended by United States Environmental Protection Agency (USEPA) and United States Geological Survey (USGS). This study improve our understanding of PMs in Western North Dakota, USA and suggest avenues for future research to be taken for more in-depth study.