C02_01

Radiocarbon measurements on soot particles preserved in sediments illustrate past fossil fuel usage history in China

Dusek U¹,  Tang Y², N. Waters C⁴, Schneider T⁵, Yao P¹, Han Y^2,3

¹Centre for Isotope Reserach, University Of Groningen, Groningen, Netherlands, ²Institute of Earth Environment and Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xi'an, China, ³Jiaotong University, Xi'an, China, ⁴University of Leicester, Leicester, United Kingdom, ⁵Columia University, New York, USA

Fossil fuel (FF) combustion accounts for a large, but uncertain, amount of elemental carbon (EC) in the atmosphere, where EC plays an important role in climate warming and adversely affects human health. However, historical estimates of FF contributions to air pollution are limited by uncertainties in fuel usage and emission factors. Here, we developed a novel radiocarbon method specifically applied to sedimentary soot, defined as the most refractory part of EC. The method was based on a two-step thermal protocol for isolating EC from atmospheric aerosol samples. Then, we constrained FF-soot emissions from southeastern China over the past 110 years using a sediment core from a maar lake. For this lake, exogenic material such as soot, originates almost entirely from atmospheric deposition.

The reconstructed soot accumulations reflect the integrated effects of increased fossil fuel use caused by economic development and reductions in emissions due to pollution controls. A sharp increase in FF-soot started at 1950 as southeastern China industrialized and developed economically, but both the percentage and the fluxes of FF-soot fraction decreased over the past decade, confirming the efficiency of pollution controls on the reduction of soot emissions. We compare FF-soot history to changes in CO₂ emissions, industrial and economic activities, and pollution controls and show that FF-soot fluxes are more readily controlled than atmospheric CO₂. Our independent FF-soot record provides insights into the effects of economic development and controls on air pollution and the environmental impacts from the changes in soot emissions.