Using trace metals to quantify long-range transported Saharan dust in Houston, Texas

\nEvery year, trade winds periodically transport Saharan-Sahelian dust westwards across the Atlantic Ocean towards North America during the months of May-September. These intercontinental events episodically increase airborne particulate matter (PM) concentrations in parts of Texas potentially endangering public health and compliance with National Ambient Air Quality Standards. This article reviews unique methods we developed to identify and quantify African dust episodes when superposed on industrial emissions in Houston, Texas. We measured ~50 elements in PM2.5 and PM10 including trace metals and used them as inputs to a receptor model. This approach accurately tracked foreign-born aeolian aerosols demonstrating the validity of our procedure, which uses rare earth elements and transition metals to discriminate local and distal sources of dust. Our procedures can be directly extended to discriminate and quantify Asian dust mixed with anthropogenic PM in population centres without loss of generality if unique geochemical signatures for source and sink regions can be established.\n