Acidic Precipitation Research in The Netherlands

Abstract

Acidic precipitation in The Netherlands is measured with a dense monitoring system. Total deposition has dropped from 6000 mol ha^-1 a^-1 to 5000 (in equivalents H⁺). The distribution over substances, origin of the deposition, and wet and dry deposition is presented.

The Dutch Priority Program on Acidification allocates 80% for effect research, 10% for research on ammonia, and 10% for integrated assessment. It is financed by four ministries, oil refineries, and electricity producing companies. The program is coordinated by the National Institute of Public Health and Environmental Protection (RIVM). Effect research is centered at two forest sites (Douglas) and one heathland site where air, soil, and biota are continuously monitored. The research is supported by laboratory and field experiments. Ammonia research aims at better estimates of emissions from stables and fields. Integrated assessment is the focal point for the program and serves to formulate policy options.

The main concern is for forests. From 1983 to 1988 the percentage of hardly vital plus not vital forest increased from 9.5 to 21. Inputs from the atmosphere are considered important. Both coniferous and deciduous forests are damaged.

Hardly any heathland is left in The Netherlands without substantial growth of grasses, probably due to nitrogen. Small surface waters in sandy regions are almost all acidified. Damage to agricultural crops is estimated at 300 million guilders a year, monetary damage to materials at 200 million. Conclusions are related to critical loads and levels. Critical loads for total acid and nitrogen on forests and heathlands on poor sandy soils are surpassed 5 to 6 times. Heavily exposed objects (forest edges) receive 7 to 8 times the critical loads. Ozone concentrations are above critical levels but below levels where serious damage is expected.