Precipitation frequency controls nitrogenous aerosol in a tropical coastal city and its implications for plant carbon sequestration

The concentration of nitrogenous aerosols is influenced by air mass transition, local meteorological conditions, local emissions, and the wet removal effect driven by precipitation. Deposited nitrogenous aerosols influence nitrogen availability in the canopy, affecting the amount of plant carbon sequestration. However, the factors controlling nitrogenous aerosol concentrations and their implications for plant carbon sequestration remain unclear. In this study, multiple stable nitrogen isotopes in atmospheric aerosols (delta 15N-TN, delta 15N-NO3-, and delta 15N-NH4+) and rainwater (rainwater delta 15N-NO3- and rainwater delta 15N-NH4+) in one-year observations were analyzed to explore the main factors controlling nitrogenous aerosol concentrations. The results showed that NO3-; and NH4+ were the major components of TN, and their concentrations in seasonal patterns were sensitive to frequent rainfall rather than local emissions or external contributions. The concentrations of nitrogenous aerosols were negatively correlated with precipitation frequency, indicating that increased precipitation frequency induced low concentrations of nitrogenous aerosols. Moreover, the positive matrix factorization (PMF) analysis showed that coarse mode NO3-; was generated in the wet season but not in the dry season, reflecting the removal of precipitation. With the increased precipitation frequency from May to July, 42.4% of aerosol NO(3)(-)was scavenged into rainwater, indicated by the variations in the delta 15N values of nitrogenous aerosols and rainwater. This result prompted us to calculate the loss of 12.1 +/- 3.9 Gg carbon/yr plant carbon sequestration. Our study suggests that nitrogenous aerosols are captured by the high precipitation frequency in tropical areas, decreasing nitrogen availability in the canopy, which might decrease plant carbon sequestration.

Automated summary

The concentration of nitrogenous aerosols in the atmosphere is affected by air mass transition, local meteorological conditions, local emissions, and precipitation-driven wet removal effect. This study analyzed stable nitrogen isotopes in atmospheric aerosols and rainwater to investigate the main factors controlling nitrogenous aerosol concentrations. The results showed that nitrogen compounds were mainly derived from rainfall rather than local emissions or external contributions, and their concentrations were negatively correlated with precipitation frequency. The analysis also suggested that the high precipitation frequency in tropical areas decreases nitrogen availability in the canopy, leading to a decrease in plant carbon sequestration.