A Study of Black Carbon Concentrations over Puerto Rico

Black carbon (BC) is the most strongly light-absorbing component of particulate matter (PM), and is formed by the incomplete combustion of fossil and modern fuels. BC particles absorb visible light at all wavelengths, leading to heating of the atmosphere, and cooling of the Earth's surface. It also affects cloud processes, visibility, the melting of snow and ice cover, and public health. BC is known as a short-lived climate pollutant due to its impact on climate and its short lifetime in the atmosphere (i.e. in the order of 7 to 10 days). For the Caribbean, specifically Puerto Rico, the lack of BC measurements leads to uncertainties in the understanding of the importance of this species to the region. This study seeks to gain a better understanding of the variations and trends in BC concentrations as measured with a seven-wavelength aethalometer and how these concentrations vary with season and with the origin of the air masses. We use aethalometer BC measurements for 10 years (2004-2013) that were performed at the UPR's atmospheric observatory in Cape San Juan, Puerto Rico. Aethalometer data were corrected for the loading effects. Preliminary results showed that there seems to be an increase in the concentrations of BC around the month of May for several years, but there is no identifiable seasonal variation yet. Results show BC background concentrations of about 70 ng m-3 for the period of time investigated. As part of the study we seek to distinguish what fraction of the BC is a product of biomass burning. Detailed results on seasonal variations in concentrations and relationships between BC and the origin of the air masses will be discussed at the meeting. With this study we and provide data that may lead to future BC mitigation strategies and various other studies regarding BC in the region.