Biogeochemical material cycles between the atmosphere and marine/terrestrial ecosystems, their interactions with climate through atmospheric radiation and clouds, and the impacts of human activities on these processes have become extremely important issues in recent atmospheric chemistry studies. Sulfur and nitrogen components in atmospheric aerosols have attracted considerable attentions in these study areas. This special issue focuses on the sulfur and nitrogen components in atmospheric aerosols and introduces geochemical topics of recent interests in the series of processes from the emission of their precursor gases to the removal by deposition. The purposes of this issue are to summarize the current understanding of these components, to ask what kind of study will be needed in the future, and to help develop new study fields.

The oxidation of the marine biogenic dimethyl sulfide (DMS) in the atmosphere is a key process for the formation of sulfate aerosols that influence cloud properties and thus climate by serving as cloud condensation nuclei (CCN). This process has been poorly represented in global-scale atmospheric models, possibly contributing to a large low bias in CCN number concentrations recently highlighted in the clean remote marine troposphere such as the tropics and the summertime Southern Ocean. Understanding the processes controlling CCN in those “preindustrial-like” pristine environments is of critical importance for constraining the anthropogenic radiative forcing from the aerosol-cloud interaction. These backgrounds have stimulated the significant development in the understanding of DMS oxidation processes, including the recent discoveries of overlooked intermediates and reaction pathways. This paper synthesizes the recent findings in DMS oxidation processes and their subsequent role in CCN formation, mainly from the perspective of their representation in global-scale models but with feedback to the observational and laboratory works.

An organic sulfur gas, dimethylsulfide (DMS) plays potential roles in atmospheric chemistry and hence Earth’s climate regulation. DMS is produced in marine environments via biogeochemical processes and a part of the DMS is emitted from the ocean to the atmosphere at a rate of 15–40 TgS yr-¹. After CLAW hypothesis proposed, investigators have confirmed whether the cooling effect can control on-going global warming, and it has been concluded that the global contribution is too small to regulate the global warming. However, recent studies pointed out the local-scale effect of CLAW feedback especially in remote area from anthropogenic activities. Furthermore, over 35 years after the CLAW hypothesis, related research fields and techniques have been improved drastically. In this review, I describe the DMS-related sulfur cycle in surface ocean and overview the recent DMS research progresses and the future perspectives.

Ice cores, in which aerosols are preserved without changes in quality, are a tool for reconstructing past aerosol compositions and concentrations as well as the atmospheric environment associated with aerosols. In areas with cold temperature and high snowfall, aerosols stored near the snow surface are covered by new snow and stored in the snowpack before they undergo post-depositional effects such as volatilization into the atmosphere and photoreactions, so ice cores collected there have high temporal resolution and can reconstruct aerosols that are less affected by post-depositional effect. In this review paper, we present the results of research on aerosols obtained from ice cores collected in the southeastern part of the Greenland ice sheet, the region with the highest snowfall, and show future prospects for ice core research collected in highly recharged areas.

Reactive nitrogen (oxidized and reduced inorganic and organic forms of nitrogen),produced and emitted into the atmosphere during biogeochemical cycles in the ocean surface, plays a key role in atmospheric chemical and physical processes over the ocean. Understanding the oceanic emissions of reactive nitrogen is crucial to quantify the net flux of reactive nitrogen between the atmosphere and ocean including the atmospheric deposition, and to predict the subsequent influence of the flux on ocean biogeochemistry and climate. This paper reviews our understanding of the atmospheric emissions of reactive nitrogen from the ocean, with a focus on ammonia/ammonium, organic nitrogen, and nitric acid. The review places particular focus on the relevance to marine microbial activity to investigate the biogeochemical cycle of reactive nitrogen in the surface ocean–lower atmosphere and its possible changes in future.

Anthropogenic activities such as fossil fuel combustion, fertilizer use, and biomass burning lead to significant Nr (reactive nitrogen) deposition following atmospheric transportation and transformation. Atmospheric Nr deposition can alter nutrient stoichiometry in ecosystems, contributing to changes in the nitrogen cycle. Once deposited to land or surface water, Nr may stimulate primary productivity, reduce the diversity of plant species, acidify aquatic and terrestrial ecosystems. The size distribution of particulate Nr plays a crucial role in processes of particle transformation, transport and deposition. This changes depending on meteorological conditions, the interparticle condensations and/ or volatile during the transport, and the levels of air pollution. Current monitoring of atmospheric Nr mainly focuses on the inorganic nitrogen fraction, while the observation of ON_ws (water soluble organic nitrogen) remains disproportionally insufficient. Regarding ON_ws, its concentration, proportion to total nitrogen, sources, behavior in the atmosphere vary depending on the previous studies. The proportion of ON_ws that can be utilized by organisms also remains unclear. While the emissions of SO₂ and NO_X are decreasing, whereas the emissions of NH₃ are increasing, continuous monitoring is necessary to understand the long-term changes in air quality resulting from variations in emissions of pollutants and social conditions.

Nitrogen is an essential element for living organisms, originally derived from the atmosphere, and circulated in ecosystems. Nitrogen is a limiting factor for net primary production in ecosystems, and organisms acquire nitrogen through deposition of reactive nitrogen from the atmosphere and nitrogen fixation. Nitrogen oxides and ammonia released into the atmosphere by human activities can be deposited in excess in forests and oceans, affecting ecosystems. This review focuses on nitrogen deposition in forest and marine ecosystems and describes the status and issues in measuring and estimating wet and dry deposition. In addition, this paper describes how environmental and social transition caused by climate change can affect nitrogen deposition, and what kind of future research is necessary under such circumstances.