Black carbon, the sooty byproduct of incomplete combustion of fossil fuels, has emerged as a major contributor to climate change and human health impacts. Researchers in the McKelvey School of Engineering at Washington University in St. Louis have used a variety of models to take on the challenging task of measuring ambient concentrations of black carbon in the "global south" and found estimates of these harmful emissions have been grossly underestimated.
Yuxuan Ren, a doctoral student in the lab of Randall Martin, the Raymond R. Tucker Distinguished Professor at McKelvey Engineering, led a study characterizing black carbon based on measurements from the Surface Particulate Matter Network (SPARTAN), a global measurement network led by McKelvey Engineering. Ren focused on black carbon concentrations in the air in the "global south," a loosely defined group of developing countries in Africa, Asia, Latin America and the Caribbean. The researchers found black carbon concentrations in low- and middle-income areas across the "global south" to be underestimated by about 38%.
The team conducted simulations with data from the Community Emissions Data System, the Emissions Database for Global Atmospheric Research and the Task Force on Hemispheric Transport of Air Pollution. Using the GEOS-Chem open-source community model of atmospheric composition, they were able to make better connections between global emissions and localized measurements. However, measuring black carbon is not as simple as it sounds because different parts of those areas burn different materials and fuels that contribute to black carbon, which makes equal comparisons difficult.
"There are different burning activities in this region, such as household burning of wood and charcoal for cooking and heating," Ren said. "Emission inventory developers will summarize the total amount of fuel used from all these sources and estimate the total black carbon emission in the air. By comparing different studies from different regions, estimating emissions from these diffuse and inefficient sources is challenging and may lead to a certain degree of bias. We think this is the primary reason for the underestimation of black carbon."
The greatest underestimations fell in several regions: Dhaka, Bangladesh, where burning of agricultural waste, crop residue, fuel wood and cow dung, as well as poorly regulated brick kilns, contributes to black carbon emissions; Addis Ababa, Ethiopia, where black carbon emissions come from diesel-fueled heavy-duty vehicles and burning wood for fuel; Ilorin, Nigeria, which has a poorly regulated oil and gas exploitation infrastructure; Mexico City; Abu Dhabi, United Arab Emirates; Bujumbura, Burundi, where there is dependence on diesel-fueled generators and kerosene; and Kanpur, India. Ren said the underestimation at these sites has global relevance.
"The widespread two- to four-fold underestimation in black carbon across sites in Bangladesh, Ethiopia, Nigeria and Mexico suggests that the radiative effect and health impacts of black carbon may be larger than previously expected, which highlights the continued importance of black carbon mitigation efforts with potential benefits for both climate and health that warrant further investigation," she said.
Martin called out the strength of the SPARTAN network.
"This work leverages the long-term development of the SPARTAN network," Martin said. "A shining point of this study is the global consistency of this measurement network, which offers a reference to enable global evaluation."
The results prompt renewed attention to characterizing harmful black carbon in the air in low- and middle-income countries in this region, the researchers said.
"This effort examines the potential for win-win strategies that address both human health and climate through a single pollutant that is affecting both, and that's an exciting opportunity," Martin said.
Ren Y, Oxford CR, Zhang D, Liu X, Zhu H, Dillner AM, White WH, Chakrabarty RK, Hasheminassab S, Diner DJ, Le Roy EJ, Kumar J, Viteri V, Song K, Akoshile C, Amador-Muñoz O, Asfaw A, Ying-Wen Chang R, Francis D, Gahungu P, Garland RM, Grutter M, Kim J, Langerman K, Lee P-C,Lestari P, Mayol-Bracero OL, Naidoo M, Nelli N, O'Neill N, Park SS, Salam A, Sarangi B, Schechner Y, Schofield R, Tripathi SN, Windwer E, Wu M-T, Zhang Q, Rudich Y, Brauer M, Martin RV. Black Carbon Emissions Generally Underestimated in the Global South as Revealed by Globally Distributed Measurements. Nature Communications. DATE, DOI.
Funding for this research was provided by the Clean Air Fund (001591), NASA (80NSSC21K0508), National Oceanic and Atmospheric Administration (NA230AR4310464 and NA24NESX432C0001T101), and National Science Foundation (2020673), with additional contributions from NASA and the US Agency for International Development via the MAIA project.
Originally published on the McKelvey Engineering website
