This work describes a system demonstrator for environmental monitoring based on participatory sensing. Mobile environmental sensors carried by citizens are used to measure pollutant concentrations and provide this data to a Unified Sensing Platform. It demonstrates platform features like visualization of different pollution maps, enabling participatory sensing via operator-initiated measurement campaigns, wherein reporters (e.g., citizens, public servants) are invited to submit measurements via mobile applications, creation of air quality alerts when pollutant thresholds are exceeded, local and remote configuration of mobile app and sensor devices, as well as pollutant statistics. In addition, various use cases like a health information service, urban planning, or workplace safety that can be realized by means of this platform are presented.