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

Abstract

Abstract. Heavy vehicle traffic on unpaved roads in western North Dakota, due to increasing oil extraction activities, is generating coarse particulate matter (PM10) and fine PM (PM2.5), and total suspended particles (TSP), potentially raising concerns for animal and human health and impacts on crop and plant growth. However, limited quantification and characterization are available for PM from unpaved roads next to oil activities. Therefore, a study was conducted to characterize and quantify the PM concentrations from heavy traffic on unpaved roads due to increasing oil activities in western North Dakota. Three unpaved road sites were selected and paired with application of two dust suppressants (brine and magnesium chloride). MiniVol air samplers were used to quantify PM, scanning electron microscopy (SEM) was used to characterize the minerals in PM samples, and inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the chemical composition of soil samples. The average PM10 and PM2.5 concentrations were higher at site 2 (untreated loose gravel road) than at site 1 (periodically treated with dust suppressants) during the study period (2015-2016). In addition, the PM concentrations were lower in 2016 because of decreased oil activities at site 2. Statistical analyses revealed that the PM concentrations were mostly correlated with vehicle count in addition to temperature, wind direction, and rainfall. Magnesium chloride was the most effective treatment for reducing PM. The SEM analyses of PM samples revealed that most particulates were quartz, other silicates, or biogenic particles. Soil sample analyses revealed that the concentrations of most elements were lower than the threshold values set by the USGS National Geochemical Survey. Keywords: Air pollution, Air quality, Dust, North Dakota, Oil development, Particulate matter.