Atmospheric deposition of nitrogen and sulphur in relation to critical loads of nitrogen and acidity in the Czech Republic

Abstract

Estimates of dry and wet deposition of sulphur and nitrogen were compared with critical loads of sulphur and nitrogen in the Czech Republic on 1 ×1 km grid. Deposition was estimated from monitored and modelled concentrations in the atmosphere and in precipitation where the most important acidifying compounds are sulphur dioxide, nitrogen oxides and ammonia, and their reaction products. Wet deposition was derived from concentration values for SO42-, NO3- and NH4+ in precipitation and from precipitation amounts. Dry deposition was derived from concentrations of gaseous components and aerosol in the air, and from their deposition velocities. A simple mass balance model was used to calculate critical loads of sulphur and nitrogen. The annual average value of total (potential) acid decreased from 4,147 to 2,185 mol H+/ha/year between 1991 and 2000. A reduction in total sulphur and nitrogen (total potential acid) deposition by about 60% would protect 98% of the area of sensitive forests.

Keywords

• acidity
• atmospheric deposition
• critical loads
• nitrogen oxides
• sulphur oxides