Emission estimates based on ambient N2O concentrations measured at a 200m high tower in the Netherlands 1995–1997

Abstract

In the period 1995 to 199’7 the N~O concentration in ambient air at 200 m height was measured at the 200 m tower in Cabauw in the center of the Netherlands. These measurements were carried out simultaneously with CO~ and CHa measurements, h~ this paper fl~e thne series for the different trace gas species are compared for the year 1995. This comparison shows the different nature of N:O as compared to the two more abundant trace gases, methane (CH~) and carbon dioxide (COz). The diffuse character of the main N:O source in oar region, the agricnltural soils, in combination with the relatively poor resolution of the measurements as compared to the rcsolution of the COs and CH4 data, makes a detailed evaluation of the emissions impossible. Alternatively a simple calculation is proposed to evaluate the N~O emission for a region up to about 200 km upwind of the measurement location. This calculatiot~ uses the sudden increase in concentration that is observed after the break-up of a nocturnal inversion layer. The results of 26 nights show au emission level of 31 ± 13 kton N/year. Tb.is level is lower compared to the emission level of 47.4 kton N/year that is reported for 1996 for the Netherlands using bottom up inventories.