Spatial and Geochemical Techniques to Improve Exposure Assessment of Manganese in Windsor, Ontario

Abstract

This study was conducted to investigate the urban geochemistry of the city of Windsor (Ontario) and to provide added source apportionment information to work being carried out by the Canadian government. The goal of this study was to investigate the distribution, spatial variation and sources of manganese in urban Windsor soil. The literature indicates that human exposure to high levels of manganese, via inhalation, can cause respiratory and/or neurological effects. At the outset of the present study it was first hypothesized that vehicular traffic was the dominant source of anthropogenic manganese. An alternative hypothesis was that there were multiple anthropogenic sources of manganese in Windsor. The sample collection scheme was designed to determine (1) the current and background soil concentrations of manganese in Windsor, (2) the spatial distribution of manganese in order to reveal sources of manganese, and (3) the manganese content of moss-sequestered airborne particles, which can potentially deposit onto the soil surface, using low-technology biomonitoring. The first phase of the study consisted of a preliminary soil survey which identified elevated areas of soil manganese concentrations. During this survey, the field efficiency of a field portable X-ray fluorescence (FPXRF) instrument, as well as sample preparation methods were evaluated. Efficiency of the FPXRF was determined by comparison to ICP-MS, a traditional trace element analysis method. The preliminary soil survey identified several areas of elevated (ranging from 884 to 2390 ppm) soil manganese which were further investigated during the second, more complete, soil survey. The moss biomonitoring technique of using moss bags was used to collect airborne particles for semi-quantitative analysis. Analysis of soil samples included total manganese and other trace elements, pH, moisture and carbon content, and manganese speciation. Urban Windsor soil manganese distribution revealed both natural and anthropogenic sources of soil manganese and three distinct soil sample types, transect, baseline and natural. In general, manganese in Windsor had a west-to-east trend of decreasing levels in soil and moss-sequestered airborne particles. The latter showed a modern-day elemental signature while the former (collocated soil) a legacy elemental signature. It was concluded that both the FPXRF instrument and the moss biomonitoring technique can be useful screening tools in studies of urban environments.