Climate–Industry Interplay in Coastal Air Quality: A Comparative Sentinel-5P Study of the North Atlantic and Gulf of Mexico

Coastlines host dense human activity that concentrates combustion and elevates carbon monoxide (CO) and nitrogen dioxide (NO₂) burdens.Yet complex coastal meteorology often limits ground monitoring.This study addresses this gap with a multi-year, dual-pollutant, jurisdiction-scale analysis using a transparent Sentinel-5P column-burden workflow.This work employs the workflow on Canada's Nova Scotia (NS), a cool and relatively stable North Atlantic coast, and the US state of Louisiana (LA), a warm-humid Gulf coast with one of the densest refining hubs, providing two contrasting coastal domains.The present analysis evaluates 2019-2024 tropospheric column CO and NO₂, applies uniform quality-assured screening, generates time series composites at native resolution, classifies spatial fields with Jenks Natural Breaks, and examines temporal trends.Columns are compared with inventories and ground networks as consistency checks.Six-year means highlight persistent contrasts: NS's column CO is slightly higher than LA's (0.0338 vs. 0.0321 mol m⁻²), and NS's NO₂ is ≈ 2.5× LA's (6.09×10⁻⁵ vs. 2.39×10⁻⁵ mol m⁻²).In NS, NO₂ peaks in summer, while CO reaches its highest seasonal mean in spring; in LA, NO₂ peaks in winter and CO peaks in spring.Recurring hotspots appear over Halifax-Dartmouth and North Sydney, and along the Baton Rouge-New Orleans corridor and northern parishes.These patterns may reflect a combined influence of coastal setting, seasonal atmospheric structure, and local activity, although direct meteorological attribution was not performed.By integrating satellite archives with ground networks, the study provides a reproducible, auditable approach that translates seasonal column dynamics into jurisdiction-ready evidence for evaluation calendars and corridor-focused siting, improving the timing and targeting of coastal airquality management, and supporting United Nations Sustainable Development Goals (SDGs) 3 and 11.