Significant Latitudinal Gradient of Nitrate Production in the Marine Atmospheric Boundary Layer of the Northern Hemisphere

Abstract

Abstract Atmospheric samples collected during 2017 and 2018 Chinese Arctic Expedition cruises are used to investigate the latitudinal gradients of nitrate (NO 3 − ) sources and production in the marine atmospheric boundary layer of the Northern Hemisphere. Both concentration and isotopic composition (δ 15 N, δ 18 O, and Δ 17 O) of atmospheric NO 3 − show significant latitudinal gradients. δ 15 N suggests that continental sources dominate atmospheric NO 3 − in both mid‐and high‐latitudes, while oceanic RONO 2 emissions account for 21%–26% of the NO 3 − budget in mid‐latitudes. Slightly higher δ 15 N in high‐latitudes than in mid‐latitudes indicates insignificant isotope effects of long‐range atmospheric transport of NO 3 − . δ 18 O and Δ 17 O of NO 3 − are significantly higher in mid‐latitudes than in high‐latitudes, suggesting distinct main production pathways in the two regions. It is estimated that ∼69% of NO 3 − is produced via NO 2 + OH in the high‐latitudes, while ∼68% of NO 3 − is from N 2 O 5 + H 2 O and NO 3 + DMS/CH pathways in mid‐latitudes.