Different science and engineering communities are currently planning, developing, and deploying the next generation of large-scale sensor-based observing systems. These systems enable us to understand at local, regional, and global scales important man made and natural systems such as environmental health (e.g., global warming, biodiversity, drinking water, and pollution), traffic and transportation systems, critical infrastructure monitoring, and supply chains. In this proposal, we propose a monitoring infrastructure that integrates personalized and mobile sensors and apply it to the problems of air quality and traffic monitoring in Doha. The research makes contributions in two complementary areas: (1) At the infrastructure level: we propose supporting an infrastructure that integrates traditional sensors and data loggers, with commodity and low cost sensors opportunistically when they are available. The infrastructure will be used to investigate a number of research problems and next generation services including sensor data stream processing, integration of mobile sensors and data cleaning due to mobility, interoperability, and data visualization; and (2) At the application level: the proposed research will provide important data traffic and air quality data for Doha, allowing scientists to answer important environmental and health questions, and providing policy makers with critical information.