Water residence time controls seasonal nitrous oxide budget in a semi-enclosed bay: Insights from an improvement estimation method.

This study developed an estimation method for the NO budget using N stable isotope labeling techniques, a dual-layer model and a box model, which was used to elucidate the underlying dynamics of NO accumulation in Zhanjiang Bay. The results showed that although the net input of NO during the rainy season was 2.36 times higher than that during the dry season, the overall NO concentration was only 66.6 % of that during the dry season due to the extended water residence time in the dry season. Our findings highlighted that water residence time was the key factor for the NO emission, and a longer water residence time was unfavorable for the efflux of NO through hydrodynamic processes and was more conducive to the production and accumulation of NO within the bay. This research enhanced our comprehension of NO dynamics and provided crucial insights for refining nitrogen management strategies and mitigation efforts.