Calculation and mapping of critical loads of sulfur and nitrogen in Flanders, Belgium

Up to now, critical loads calculations for the Flemish Region were based on European background data of surrounding countries. A first attempt has bee n made to calculate and map critical loads for forest ecosystems in Flander s using available site-specific information. Values of current deposition w ere used to calculate and map exceedances. The lowest critical loads for ac idification (697 eq ha(-1) year(-1)) occur in the Campine and the north of Limburg where ecosystems largely consist of coniferous forests on poor sand y soils. The dominance of coniferous forest types in the Campine is also re sponsible for low critical load values for eutrophication (between 536 and 971 eq ha(-1) year(-1)). Tn 75% of the receptor points that have been consi dered an exceedance of the critical load for acidification is noted, primar ily in areas with high SO2 and NOx depositions, such as the north of the pr ovinces East and West Flanders and Antwerp. The critical load for eutrophic ation is exceeded in ail points considered. Exceedances are particularly hi gh in coniferous forests in West Flanders, and in the north of the province s of Antwerp and Limburg, where especially NHx depositions amount to high v alues. Data needed for the calculation of critical loads are still sparse i n Flanders, e.g, for: (1) weathering rates of soil minerals; (2) intercepti on and evaporation of forest ecosystems; and (3) uptake of N and basic cati ons by vegetation. This supplementary information will contribute to a furt her refining of the calculated critical loads, which constitute indispensab le information in developing an emission abatement policy. (C) 2000 Elsevie r Science B.V. All rights reserved.