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 + , Mg 2+ , and Ca 2+ 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 δ 15 N values for NO 3 − ‐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.