Black carbon concentrations, sources, and health risks at six cities in Mississippi, USA.

Black carbon (BC) in ambient fine particulate matter (PM_2.5) was measured for 15 months (Sept 2013–Dec 2014) at six locations throughout the state of Mississippi, USA, to investigate the distribution, temporal variations, potential sources, and health risks of BC. Sampling sites were divided into two groups based on population: large cities (Gulfport, Hattiesburg, and Jackson) and small cities (Grenada, Hernando, and Pascagoula). The mean concentration of BC was higher in large cities compared to small (mean ranges of 1.55 to 2.04 µg m⁻³ in large cities and 1.01 to 1.73 µg m⁻³ in small cities) and across locations BC was impacted by season and meteorological variables, particularly wind and precipitation. The results of potential source contribution function (PSCF) and concentration weighted trajectory (CWT) and trajectory cluster analysis confirmed that the long-range transport impacted BC concentration and air masses from the north-west were a major distant source of BC at all study sites. The accumulation of pollutants was enhanced by short trajectories connected to air masses coming from the continental areas of the USA and Canada, while low BC concentrations in fast moving air masses originated in both the ocean and continental areas with lower emissions. Following BC environmental analyses, cancer and non-cancer risk assessments were conducted for BC exposure in adults and children, with cancer risks for adults being higher than the Environmental Protection Agency (EPA) recommended limits, while non-cancer risks were below the threshold values. BC is poorly understood in rural states, like Mississippi, and this research identifies patterns and potential health risks associated with BC. [ABSTRACT FROM AUTHOR]