Ammonium record over the last 96 years from the muztagata glacier in Central Asia

As a major alkaline gas in the atmosphere, ammonia （NH3） plays an important role in atmospheric chemistry. However, there is little knowledge about NH3 variations in the Central Asia. Here we analyzed the ammonium （NH4^＋） history recorded in an ice core from the East Pamir in Central Asia, which was drilled on the Mt. Muztagata at the elevation of 7010 m a.s.I, in 2003. The core was carefully dated and NH; concentration history during 1907-2002 was reconstructed. The result shows that NH; concentration remained approximately constant until the 1930s after a sudden decrease at the very beginning of the 20th century, followed by a minimum in 1940 before increasing steadily to the peak at the end of 1990s. It is found that the annual mean NH4^＋ concentration was strongly associated with the Northern Hemisphere temperature, suggesting the impact of temperature on NH3 emissions in the Central Asia. Moreover, an increase of NH4^＋ concentration after 1940 also reflects the enhancement of NH3 emissions from anthropogenic sources such as fertilizer applications and livestock wastes in the 20th century.