The long-term goal of this research is to identify chemical signatures and air masses of the particulate matter (PM) in the atmosphere and to potentially locate the local and regional origins of the known contaminants. We are currently examining atmospheric PM samples in areas representing varying populations, urban and rural, by comparing data from two local sites. The first site represents an urban environment and samples are collected daily at the Boise State University campus. The second site represents a rural environment and samples are collected weekly from the Dry Creek Experimental Watershed, located north of Boise. We can compare the effects of population on PM concentration for different sizes from these two sets of data. This data is relevant to public health because atmospheric pollution impacts respiratory health and the contamination of drinking water. We expect to find greater numbers of particulates at our urban site than at our rural site, thus informing us of anthropogenic pollution. We also expect to monitor large weather events, such as forest fires and sandstorms, allowing us to study the effects on air quality, both during and following the events.