Organic carbon (OC) and elemental carbon (EC) in PM2.5 influence regional climate change by scattering and absorbing solar radiation. Recent attention has focused on the long-range transport of OC and EC to high-altitude regions due to their potential role in accelerating spring snowmelt. Although subalpine and alpine areas account for only about 1% of South Korea, these high-elevation zones are highly vulnerable to climate change and provide important insights into how ecosystems may respond and adapt in the future. We collected 29 PM2.5 samples near Nogodan Peak (1,440 m a.s.l.) in Jirisan National Park and 10 samples at Seoul National University (91 m a.s.l.) between March 2022 and April 2024 to quantify OC and EC concentrations. The mean concentrations and standard deviations of OC and EC were 2.0±1.4 and 0.2±0.1 μg m-3 in Jirisan, and 3.6±0.9 and 0.3±0.2 μg m-3 in Seoul, respectively. These concentrations are lower than previously reported values across ~20 sites in South Korea, likely due to the national reduction in PM2.5 during the study period. Given these lower concentrations, the effect of EC on snowmelt might have been small in Jirisan. High OC/EC ratios (Jirisan: 22.1; Seoul: 12.5) may reflect biomass burning or the formation of secondary organic aerosols. As biomass burning is projected to increase under future climate scenarios and may alter the source and composition of carbonaceous aerosols, long-term research is essential to better understand their potential impacts on high-altitude ecosystems.

Carbon is not only an essential element for life but also a key player in climate change. The radiocarbon (14C) analysis using accelerator mass spectrometry (AMS) is a powerful tool not only to understand the carbon cycle but also to track pollutants derived from fossil carbon, which have a distinct radiocarbon isotope ratio (Δ14C). Many studies have reported Δ14C of carbon compounds in streams, rivers, rain, snow, throughfall, fine particulate matter (PM2.5), and wastewater treatment plant effluents in South Korea, which are reviewed in this manuscript. In summary, (1) stream and river carbon in South Korea are largely derived from the chemical weathering of soils and rocks, and organic compounds in plants and soils, strongly influenced by precipitation, wastewater treatment effluents, agricultural land use, soil water, and groundwater. (2) Unprecedentedly high Δ14C of precipitation during winter has been reported, which can directly and indirectly influence stream and river carbon. Although we cannot exclude the possibility of local contamination sources of high Δ14C, the results suggest that stream dissolved organic carbon could be older than previously thought, warranting future studies. (3) The 14C analysis has also been applied to quantify the sources of forest throughfall and PM2.5, providing new insights. The 14C data on a variety of ecosystems will be valuable not only to track the pollutants derived from fossil carbon but also to improve our understanding of climate change and provide solutions.