In Korea, while primary pollutants have generally declined, fine particulate matter (PM2.5) and ozone (O3) remain persistent challenges, underscoring the need for a strategic realignment of monitoring priorities. However, past practice has tended to m...
In Korea, while primary pollutants have generally declined, fine particulate matter (PM2.5) and ozone (O3) remain persistent challenges, underscoring the need for a strategic realignment of monitoring priorities. However, past practice has tended to maintain broad coverage of legacy pollutants such as SO2 and CO, even where consistently below the national standards and the marginal policy value of continued universal monitoring is limited. This study analyzes Chungcheongnam-do (Chungnam) integrating national and provincial emission inventories with long-term ambient observations and international benchmarks to evaluate network operation options. In Chungnam, annual PM2.5 concentrations have consistently exceeded the national standard since monitoring began, and O3 has shown a pronounced upward trend. By contrast, SO2 and CO concentrations remain far below their standards, reflecting effective combustion controls and sulfur management. Given the current concentration levels, detection limits of routine instruments, and the costs of procurement and maintenance, we assess the limited marginal utility of continuing SO2 and CO measurements at all urban air quality monitoring station (AQMS) sites. We therefore suggest reallocating capital and operating budgets from low-utility SO2 and CO monitoring to enhanced photochemical monitoring. These actions will increase the cost effectiveness and policy relevance of the AQMS network while maintaining representativeness for priority pollutants. Although the analysis centers on Chungnam, the framework and recommendations are transferable to other regions planning medium- to long-term AQMS strategies in the future.