Ammonia, the dominant base in the remote marine troposphere: a review

Abstract

Ammonia appears to be the dominant base in the remote marine troposphere, yet its røle inatmospheric acid-base chemistry is not well understood. The physical and chemical interactionsof ammonia with acidic species is complicated by its presence in the gas and particlephases and in cloud-, rain- and seawater. This review summarizes the reported ammoniaconcentration data in these 5 phases as well as existing sampling and analysis methods. Anattempt is made to compare these data using equilibrium and scavenging calculations. Thelowest measured ammonia gas phase concentrations appear to be consistent with reportedsulfate and ammonium concentrations in the particulate phase. The high gas phase concentrationsof ammonia found in older data appear to be a result of sampling artifacts. Reportedammonium particle and rainwater data also appear to be consistent with each other. Calculations suggest that ammonia may be in equilibrium between the gas phase and theOcean surface. To confirm or refute these conclusions, the simultaneous measurement ofammonia and relevant acidic species in all 5 phases is needed.