This study demonstrates significant correlations between the organic matter content of urban street dust and certain mineral magnetic properties, which accords with previous work that indicates magnetic parameters offer potential as a proxy for organic content. However, site-specific data demonstrate the relationship can be different for particular roads, even within the same area. This indicates the association may be more complex than previous work proposes and a cautionary note is required. It is recommended that the nature of the relationship between magnetic and organic properties should be fully explored for particular urban environments and individual field settings, before using magnetic measurements as a proxy for organic matter content. Furthermore, whilst soil is believed to significantly contribute to urban street dust, magnetic values in this study are much higher than those previously reported for top-soils and indicate the influence of other sources, such as anthropogenic pollutants. This suggests that using magnetic measurements to discriminate sources of urban particulates has considerable potential for development

Respirable particulate matter was collected inside and outside of a building located in Wolverhampton city centre during the same time period between 19/9/00 and 1/5/01. A total of 103 pairs of indoor and outdoor measurements were made using Casella personal dust monitors. The building monitored was located in a small street canyon produced by 4- and 5-storey buildings on both sides of the road. The road is the main approach road to a major bus station and is used by large numbers of heavy-duty diesel vehicles each day. The mean concentration for outdoor samples was 27.6 and 9.8 µg·m^–3 for indoor samples. The mean indoor/outdoor ratio for this period was 0.4 (±0.02 SE). Meteorological variables including wind speed, wind direction and precipitation were measured at a nearby urban monitoring station. A greater wind speed caused an increase in the quantity of outdoor generated particulates penetrating indoors. Wind direction affected both indoor and outdoor particulate concentrations, with lower concentrations being observed when the wind direction was parallel to the street canyon. The indoor/outdoor ratio also showed a decrease during parallel wind conditions. During days with high amounts of precipitation, the concentration of particulates, both indoors and outdoors, decreased significantly. The personal exposure of a building occupant was measured for 20 working days in conjunction with outdoor and indoor measurements. Personal exposure concentrations were well correlated with indoor concentrations (r² = 0.98). Forty of the indoor and outdoor particulate samples of dust were chemically analysed for sulphate, nitrate, chloride, zinc, copper, manganese and aluminium to determine any indoor/outdoor relationships of particulate chemistry and any interrelationships between the analytes.

Urban street dusts have been monitored monthly for one year (May 2000 to April 2001, their magnetic properties measured and their multivariate relationships modelled by Simultaneous R-and Q-mode Factor Analysis, so as to differentiate dusts from three urban roads (two in Wolverhampton and one in Dudley) in the West Midlands (U.K.). Results show the street dusts contain a large range of magnetic concentrations, magnetic mineralogy and magnetic domain sizes, which has enabled significant differences (p < 0.001) to be identified between individual roads. Whilst soil is proposed as a notable provenance for the dust, magnetic values in this study are much higher than those previously reported for topsoils and thus, indicate the influence of other sources, such as anthropogenic pollutants. This indicates the potential of magnetic methodologies as a valuable means of contributing to local and national road pollution monitoring schemes. Furthermore, Factor Analysis aided the interpretation of dust variations and simplified the inter-relationships between magnetic parameters, which highlights its potential for classifying and discriminating urban street dust sources.

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