Atmospheric deposition of inorganic and organic nitrogen and base cations in Hawaii

Atmospheric deposition of nitrogen (N) and base cations was measured for 5-7 years on the island of Hawaii and for 1.5 years on Kauai. On Hawaii, mean annual fluxes of K⁺, Mg²⁺, and Ca²⁺ were 15, 17, and 13 kg ha^-1 yr^-1, respectively. Fog interception was the largest deposition pathway. Sea salt contributed the majority of cations, although biomass burning and Asian dust were significant sources for some years. Total N deposition (inorganic and organic) averaged 17 kg N ha^-1 yr^-1. Fog interception was also the largest source of N, depositing 16 kg N ha^-1 yr^-1. Precipitation deposition was 1.0 and 0.2 kg N ha^-1 yr^-1, respectively on Hawaii and Kauai. Dry deposition on Hawaii was 0.1 kg N ha^-1 yr^-1. Organic N averaged 16 and 12% of total N in rain and fog, respectively. The δ¹⁵N values for NO₃^--N are consistent with long-range transport of N from Asia in the spring/summer and from North America in the fall/winter as nonvolcanic sources. Atmospheric deposition on Hawaii may completely account for a previously identified soil N imbalance.