Mineral dust arising from soil/road dust resuspension, construction activities, and long-range transport of crustal material is a major source of particulate matter (PM) of human health concern in many urban airsheds. Commonly applied techniques using elemental markers are often limited in the ability to trace and distinguish these sources, due to overlapping chemical profiles. It was hypothesized that coupled isotope ratios of Strontium-Neodymium-Hafnium (Sr-Nd-Hf) are superior to elemental markers in distinguishing these mineral sources of PM. For this reason, a novel high-yielding gravity flow column chromatography scheme was developed for facile and quantitative separation of Sr, Nd, and Hf, which facilitated precise and accurate measurements of their isotope ratios. The developed chromatography scheme was used to fingerprint five potential sources of Sr, Nd, and Hf namely (1) motor vehicles, (2) petroleum refining (3) local soil (4) concrete/cement dust from construction activities and (5) trans-Atlantic North African dust, a prominent summertime PM source in southeastern United States. A novel mass balance model was developed that combined 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf ratios with elemental concentrations to apportion PM2.5 in Houston, Texas to various sources during two North African dust events. The results demonstrate that the use of isotope ratios in aerosol research are better predictors for tracing and quantifying mineral sources of airborne PM2.5; highlighting their potential value in identifying local vs. long-distance sources of airborne PM emissions of health concern to help inform decision-making in support of improved air quality in urban environments.
About the Speaker
Dr. Sourav Das is a postdoctoral fellow in the School of Environment, working with Dr. Clare Wiseman. He graduated with a BTech (Hons.) in Civil Engineering from Indian Institute of Technology, Kharagpur in 2012 and a PhD in Environmental Engineering from Texas A&M University in 2021. His research work during his PhD had largely focused on developing methods to trace and quantify source contribution to airborne urban particulate matter using chemical characterization techniques. His current work focuses on the sources, elemental composition, and toxic potential of urban road dust.