Past, Present and Future Atmospheric Nitrogen Deposition.

Area of Science:

• Atmospheric Chemistry
• Biogeochemical Cycles
• Environmental Science

Background:

• Rising atmospheric reactive nitrogen from human activities affects terrestrial and marine ecosystems.
• Nitrogen deposition is a critical factor influencing ecosystem productivity and health.

Purpose of the Study:

• To quantify the global distribution of total nitrogen deposition, including inorganic and organic fractions.
• To assess past and projected changes in nitrogen deposition due to anthropogenic activities.
• To incorporate organic nitrogen (ON) primary emissions into atmospheric modeling for a comprehensive analysis.

Main Methods:

• Utilized the atmospheric chemistry-transport model TM4-ECPL for global distribution calculations.
• Incorporated anthropogenic and biomass burning emissions from ACCMIP historical and RCP6.0/RCP8.5 scenarios.
• Accounted for both inorganic nitrogen (IN) and organic nitrogen (ON) in gaseous and particulate phases.

Main Results:

• Present-day global nitrogen emissions are ~60% anthropogenic, with ON comprising 20-25% of total deposition.
• Including ON emissions increased total N deposition by ~20% compared to models without ON.
• Soluble N deposition has increased 3-fold over land and 2-fold over oceans since 1850.
• Projections show regional shifts in N deposition composition, with reduced compounds gaining importance.

Conclusions:

• Organic nitrogen is a significant, often overlooked, component of the global nitrogen cycle and deposition.
• Anthropogenic activities have drastically increased nitrogen deposition, with substantial contributions from organic forms.
• Future projections indicate regional changes in nitrogen deposition chemistry, necessitating refined environmental management strategies.