What question did this study set out to answer?

This research aims to assess CO2 dynamics in Guangzhou by differentiating between anthropogenic and biogenic sources. Understanding these patterns is crucial for effective urban carbon mitigation strategies.

March 5, 2026Open Access

Atmospheric CO 2 dynamics in a coastal megacity: spatiotemporal patterns, sea–land breeze impacts, and anthropogenic–biogenic emission partitioning

Key Points

This research aims to assess CO2 dynamics in Guangzhou by differentiating between anthropogenic and biogenic sources. Understanding these patterns is crucial for effective urban carbon mitigation strategies.
Analyzed CO2 and CO measurements across multiple sites from January 2023 to September 2024.
Utilized a site-specific relationship (ΔCO / ΔCO2) to resolve CO2 variability.
Studied the effects of sea-land breeze on CO2 concentrations along a coastal-urban-suburban gradient.
Quantified contributions of fossil-fuel and biogenic emissions without using fixed emission inventories.
Identified a seasonal 'coastal CO2 dome' with peak concentrations displaced from the urban core.
Demonstrated sea-land breeze effects: ventilating CO2 in spring-winter but causing accumulation in summer.
Found that summer biogenic uptake offsets about 60% of concurrent fossil-fuel emissions.
Establishing that urban CO2 attribution remains stable across different transport model configurations.

Abstract

Abstract. Attributing observed carbon dioxide (CO2) to fossil-fuel emissions versus biogenic fluxes is essential for assessing urban mitigation, but in coastal megacities it is complicated by anthropogenic–biogenic coupling and sea–land breeze (SLB) circulation. Here we analyze Guangzhou using multi-site in situ CO2 and CO measurements (January 2023–September 2024), transport footprints, and a site-specific ΔCO / ΔCO2 (RCO) relationship to resolve spatiotemporal variability, quantify SLB effects, and partition fossil-fuel (CO2ff) and biogenic (CO2bio) contributions without assimilating emission inventories. Along a coastal–urban–suburban gradient, the coastal site shows the largest seasonal amplitude, the vegetated site exhibits strong summertime diurnal amplitude, and the urban core is combustion-dominated. These gradients reveal a “coastal CO2 dome” that – unlike urban domes often conceptualized as core-anchored – is seasonally displaced, with peak concentrations shifting away from the core due to the interplay of coastal ventilation and biogenic exchange. SLB effects are seasonal: SLB ventilates CO2 in spring–winter but promotes summertime accumulation (+2.08 ppm) under stable stratification, accompanied by pronounced CO enhancements, consistent with trapped/recirculated combustion plumes. Regression-derived urban RCO is consistent with post-2013 broad tightening of coal/industrial and vehicle-emission controls. Winter-afternoon urban CO2ff attribution remains robust to transport-model configurations and measurement/background uncertainty. Summer-afternoon CO2bio shows substantial biogenic uptake, offsetting ∼ 60 % of concurrent CO2ff. These results demonstrate that coastal dynamics and urban greening reshape observed CO2 signals, highlighting that biogenic–anthropogenic decoupling and SLB-aware sampling are essential for the robust evaluation of carbon mitigation in coastal megacities.

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