Deposition of the most acidifying components in The Netherlands during the period 1980–1986

Abstract

Detailed maps of the deposition of acidifying components in The Netherlands are presented. The deposition was estimated from measurements of concentrations in the atmosphere and precipitation. Lack of information on the concentration of ammonia and ammonium in air made it impossible to estimate dry deposition. Therefore, these were estimated by model calculations. The nationwide averaged deposition of total (potential) acid in 1980 was ca. 5800 mol H⁺ ha⁻¹ a⁻¹. The most important acidifying components are sulphur oxides, nitrogen oxides and ammonia and their reaction products. Sulphur compounds (SO_x) contributed about 49%, reduced nitrogen species (NH_x) 23% and oxidized nitrogen species (NO_ty) 28% to the total deposition. Wet deposition contributes 30% to the total deposition. The spatial distribution of the total deposition shows a gradient over The Netherlands with highest values in the south and lowest in the north.

In 1986 the total deposition was estimated to be ca. 4900 mol H⁺ ha⁻¹ a⁻¹ (40% SO_x, 32% NO_y and 28% NH_x. The decrease is mainly the result of the lower SO_x deposition. The relative contribution of inland emissions to the deposition in The Netherlands is about 41%. About 30% of the NH, deposition is due to foreign sources; for SO_x this is about 80% and for NO_y 65%. About 80% of Dutch emissions is deposited outside The Netherlands. The net export of SO_x decreased between 1980 and 1985 from 150 kt a⁻¹ to 35 kt a⁻¹, while the net export of NO_y (ca. 280 kt a⁻¹) and NH, (ca. 155 kt a⁻¹) has remained constant over the period 1980–1986.