Spatiotemporal variations of monocarboxylic acids in snow layers along a transect from Zhongshan Station to Dome A, eastern Antarctica

The spatiotemporal distributions of formate and acetate in snow layers along a transect from Zhongshan Station to Dome A are presented here. The mean concentrations of mono-carboxylic acids in summer surface snow layers were 2.93 ± 1.72 ng g− 1 and 10.07 ± 5.87 ng g− 1 for formate and acetate, respectively. In the snow pit samples, the concentrations varied between 0.47 ± 0.14 ng g− 1 and 3.12 ± 4.24 ng g− 1 for formate and between 5.31 ± 1.55 ng g− 1 and 13.29 ± 4.64 ng g− 1 for acetate. Spatially, the concentrations of both acids featured negative trends with increasing elevation and distance inland for the initial 600 km of the transect, which implies that marine sources from the coastal oceans dominate the acid supply. Different distribution styles of the acids in the interior section (600-1248 km) suggest that different source region and transporting mechanism may be responsible for the acid deposition in the interior regions. Seasonal variations in the amounts of acid in a coastal snow pit (29-A) indicate higher values in the summer and lower amounts in the winter. An enlarged source region and intensified production and transport mechanisms were primarily responsible for the higher values in summer. Longer records from the interior snow pits (29-L and 29-M) indicate elevated values in the 1970s and lower values in the 1980s and early 1990s. The increases in the mono-carboxylic acids since 1999 in snow pit 29-L and since 2005 in snow pit 29-M were temporally coincident with Chinese expedition activities in the area, suggesting that human activities were responsible for the increases in the acid load during recent decades.