Ambient air-quality data contains detailed information about individual sources that is currently under-exploited. This study examines ambient measurements of fine particulate matter (PM₁₀) from a complex industrial site, in order to show how ambient concentrations depend on factors related to dispersion - such as wind speed and wind direction, and on different levels of source activity - such as time-of-day and day-of-week. When this additional information is combined with inverse-modelling techniques, it can be used to attribute PM₁₀ impacts to individual sources. The information can also be used to comprehensively verify the performance of atmospheric dispersion models.