Please select one of the following compounds:

• NH3 (Ammonia)
• NOx (Nitrogen Oxides)
• SO2 (Sulfur dioxide) 

NOx is also a precursor of tropospheric ozone; SO2 is also an precursor gas of sulphate aerosol. To a much lesser extent the greenhouse gas N2O is also an acidifying gas, since it is also contributes to a limited extent to deposition of atmospheric nitrogen.

• Global Emission Inventory Activity (GEIA) (Global gridded emission inventories)
• GEIA NH3 inventory (gridded, 1990 emissions)
• EEA (Information on acidification)
• US EPA (Information on acid rain)