Observations of surface CO2 at an urban station in Wuhan, Central China: temporal variations, sources, and sinks

Abstract

Observation of atmospheric carbon dioxide (CO₂) is important to understand its temporal variations, sources, and sinks, which ultimately help mitigate its climate effects. While most CO₂ observations are conducted in background or remote regions, fewer studies focus on urban areas. This study reported a one-year continuous observation of CO₂ at an urban site in Wuhan, Central China. In 2023, the average CO₂ concentration at this site was 459 ± 23.5 ppm, which was 5.53 % higher than mean values collected from other urban stations. Using the moving average filtering method, the CO₂ concentrations were filtered as a pollution source, background, and absorption sink with mean concentrations of 494 ± 21.1 ppm, 455 ± 16.1 ppm, and 434 ± 9.61 ppm, respectively. Temporal variations of these components showed similar monthly trends but different diurnal patterns, reflecting the influences of terrestrial ecosystems and human activities. Model simulations from Carbon Tracker indicated that fossil fuel combustion was the primary source, increasing CO₂ levels by 125 ppm. The ocean and biosphere acted as CO₂ sinks, reducing concentrations by 31.6 ppm and 31.2 ppm, respectively. The conditional bivariate probability function results suggested that urban CO₂ levels were influenced by local emissions and regional transports. Combined with backward trajectory analysis and CO₂ emission inventory, the local and regional contributions were further quantified with percentages of 81.9 % and 18.1 %, respectively. This study enhances our understanding of greenhouse gas behaviors and contributes to efforts to achieve carbon neutrality in urban areas.