Dry deposition of SO2 over grassland and heather vegetation in the Netherlands

Abstract

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In this report the results are presented of measurements with a SO2 dry deposition monitoring system based on the micrometeorological gradient technique at two locations in the Netherlands. From these results dry deposition fluxes, dry deposition velocities and surface resistances for a heathland and for an agricultural grassland site have been estimated using a selected set of data and a calculation procedure based on micrometeorological theory. An extensive uncertainty analysis has been made to determine uncertainties in the resulting deposition parameters. From this analysis it is concluded that the uncertainty in the deposition parameters is almost completely determined by the measurement of the concentration gradient. The meteorological surface exchange parameters can be estimated sufficiently accurate (< 20% uncertainty). At the grassland site (Zegveld) an average surface resistance Rc to deposition of 6 (+-8) s m-1 and 13 (+-12)s m-1 has been estimated for wet and dry conditions, respectively. At the heather location (Elspeetsche Veld) also a distinct difference between Rc values for wet and dry conditions has been found. These values are 20 (+-21) s m-1 and 70 (+-90) s m-1, respectively. The yearly average dry deposition flux for SO2 at Zegveld amounts to 585 (+-330) mol ha-1 a-1, while at Elspeetsche Veld the yearly average flux was 300 (+-270) mol ha-1a-1. The yearly average dry deposition velocity was 1.2 (+-0.3) cm s-1 at zegveld and 0.8 (+-0.4)cm s-1 at Elspeetsche Veld.