Gaseous organic nitrogen contributes substantially to nitrogen deposition

What the study found: The study found that gaseous organic nitrogen made a substantial contribution to wet and dry nitrogen deposition at a coastal Hong Kong site. It also found that the total annual nitrogen deposition was 39.2 ± 5.2 kg N ha−1 yr−1, with ammonium, nitrate, and water-soluble organic nitrogen all contributing.
Why the authors say this matters: The authors say the findings matter because organic nitrogen is less monitored than inorganic nitrogen, which limits understanding of global nitrogen budgets and ecological impacts. The study suggests that coordinated measurements of gaseous and particulate organic and inorganic nitrogen are needed to better constrain deposition budgets.
What the researchers tested: The researchers carried out year-long measurements of dry and wet deposition at a coastal Hong Kong site. They measured water-soluble organic nitrogen and inorganic nitrogen using a dual-surface collector that allowed simultaneous dry deposition to pure water and to a quartz filter.
What worked and what didn't: Dry deposition to water was higher than dry deposition to the filter for ammonium, nitrate, and water-soluble organic nitrogen, indicating strong uptake by the water surface. The study reports the first quantification of gaseous versus particulate water-soluble organic nitrogen in dry organic nitrogen deposition, with gaseous contributions reaching up to about 80% of the total flux; the higher water-soluble organic nitrogen fraction in wet deposition than in atmospheric particles also points to gaseous water-soluble organic nitrogen as a key source in rainwater.
What to keep in mind: The abstract describes results from one coastal Hong Kong site over one year, so the scope is limited to that setting and period. It does not provide additional limitations beyond the need for broader coordinated measurements.

Key points

• Gaseous organic nitrogen was a major contributor to wet and dry nitrogen deposition at the Hong Kong site.
• Annual total nitrogen deposition was reported as 39.2 ± 5.2 kg N ha−1 yr−1.
• The total deposition included ammonium, nitrate, and water-soluble organic nitrogen.
• Dry deposition to pure water exceeded deposition to a quartz filter for ammonium, nitrate, and water-soluble organic nitrogen.
• Gaseous water-soluble organic nitrogen accounted for up to about 80% of dry organic nitrogen flux.
• The authors call for coordinated measurements of gaseous and particulate organic and inorganic nitrogen.