Measurement Report: Changes of ammonia emissions since the 18^th century in south-eastern Europe inferred from an Elbrus (Caucasus, Russia) ice core record

Abstract. To investigate the historical levels of atmospheric ammonia (NH₃) pollution in south-eastern Europe, a 182 m long ice core was extracted from Mount Elbrus in the Caucasus, Russia. This ice core contains a record of ammonium (NH₄⁺) levels from ~1750 CE (Common Era) to 2009 CE. The NH₄⁺ ice core record indicates a 3.5-fold increase of annual concentrations from 34 ± 7 ng g^-1 (~1750–1830) to 117 ± 23 ng g^-1 over the recent decades (1980–2009). The increase remained moderate until 1950 CE (mean concentration of 49 ± 14 ng g^-1 over the 1830–1950 period), and then accelerated to reach a maximum close to 120 ng g^-1 in 1989. This ice core trend is compared to estimated past anthropogenic NH₃ emissions in Europe by using state-of-the-art atmospheric transport modeling of submicron aerosols (FLEXPART model driven with 0.5° x 0.5° ERA5 reanalysis data). It is shown that in summer, when both vertical atmospheric mixing and agricultural NH₃ emissions are strengthened, the NH₄⁺ ice core trend is in good agreement with the course of estimated NH₃ emissions from south-eastern Europe since ~1750 with a main contribution from south European Russia, Turkey, Georgia, and Ukraine. Examination of Mount Elbrus ice deposited over the second half of the 18^th century when agricultural activities were less than 10% of those during the 1990s, suggest a pre-1750 annual NH₄⁺ ice concentration related to natural emissions of 25 ng g^-1. This pre-1750 natural level mainly related to natural soil emissions represents ~20% of the 1980–2009 NH₄⁺ level, a level mainly related to current agricultural emissions that almost completely outweigh biogenic emissions from natural soils.