A Dense Sensor Network to Characterize Community Exposure to Black Carbon

Abstract

We developed a low-cost black carbon (BC) sensor and deployed over 100 of them as a connected air quality network in West Oakland, California. The West Oakland residential community is adjacent to port and rail facilities and surrounded by major freeways. As such, the community is affected by diesel particulate matter emissions from heavy-duty diesel trucks, locomotives, and ships associated with freight movement.In partnership with community stakeholders, we positioned BC sensors outside of residences and businesses, along truck routes and arterial streets, along the Port of Oakland boundary, and at upwind locations. We operated this first-of-its kind BC air quality network for 100 days in summer 2017 in conjunction with a complementary study of on-road air pollution mapping.Spatiotemporal patterns in BC concentrations in West Oakland are observed to be driven by truck activity within the community. Highest concentrations exist along truck routes, near trucking facilities, and around businesses that use trucks to transport goods and materials. Almost everywhere, BC concentrations are higher on week-days than weekend-days, as is truck activity. The community-average BC concentration matches well the concentration measured at a centrally located site operated by the Bay Area Air Quality Management District. However, on average, 75% of locations within the community are more polluted than the central monitoring site, with daytime average BC up to 1.75× higher. Daytime average BC concentrations along the Port of Oakland boundary and designated truck routes around the community are up to 3× higher than the central monitoring site average. Overnight, the spatial gradient within the West Oakland neighborhood diminishes, such that BC concentrations are more uniform. Areas downwind of the freeway, along the Port of Oakland boundary, and at some trucking facilities have persistent elevated BC concentrations in the evening and early morning hours.