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Air Quality. Annual Survey 1993

Luchtkwaliteit. Jaaroverzicht 1993

Synopsis

Based upon the measurements carried out in 1993 in the urban environment only exceedances of the limit values for fine dust and tetrachloromethane can be concluded. Fine dust limit values were exceeded at almost all urban locations. Urban concentrations of fine dust are not noticeably higher than the regional background levels, which thus also exceeded the limit values. Model calculations led to the conclusion that in 1993 the limit values for one or more pollutants were exceeded along 340 km of busy streets in large cities (ca 10% of total streets considered). The last ten years have seen a clear downwards trend in lead and sulphur dioxide concentrations associated with emission reduction measures. A similar tendency is becoming clear for nitrogen oxides, carbon monoxide and benzo[a]pyrene. During the summer of 1993 medium smog was registered on a limited number of days (10) at one or more locations. Severe smog occurred on one day ; very severe smog was not recorded. The low frequency of summer smog in 1993 may be explained by the small number of "summer days" (days with a maximum temperature higher than 25 degrees C). The limit values for the ozone concentration were not exceeded in 1993. Neither the 50 percentile nor the 98 percentile ozone concentrations displayed any clear trend. Currently, VOC concentrations are about a third less than those in the early eighties. VOC play an important role in the formation of photochemical smog. In 1993 no exceedances of the medium winter smog level were observed. The slight smog level was exceeded at a few stations. In 1993 national average potential acid deposition was 4000 mol ha-1 a-1, equivalent to the (provisional) target for 1994. In 1993 oxides of sulphur contributed 28%, nitrogen oxides 24%, and ammonia and ammonium 48% to the total potential acid deposition. Foreign sources contribute about 45% (calculated on the basis of emission data from 1990). Since 1980 potential acid deposition has diminished by about 40%. Especially measures at SO2 sources have contributed to this reduction. In 1993 average nitrogen deposition in the Netherlands was about 2900 mol ha-1 a-1. There is a diminishing trend ; but the current value is still considerably higher than the targets for the years 2000 and 2010 of 1600 mol ha-1 a-1 and 1000 mol ha-1 a-1, respectively. Lead concentrations remained in 1993 well under the limit values. The WHO standard for cadmium was exceeded in 1993 at none of the measurement locations. The target value for the deposition of cadmium was exceeded to a limited extent in 1993 but cadmium emissions and emission sources are rather uncertain. As a result of lowering the lead content of petrol and subsequently the introduction of lead-free petrol, atmospheric concentration levels and deposition loads of lead have fallen dramatically in the last decade. The daily average limit value of fluoride was exceeded at one industry-near station on two days in 1993. The emission of halogenated hydrocarbons in the Netherlands in 1993 were at the levels agreed in the CFC action programme. The ozone layer above the Netherlands was thinner than the long-term average until September 1993, with February having the largest deviation (-17%). Emissions of greenhouse gases in the Netherlands have, with the exception of CFCs, been rising during the last decade. In terms of CO2 equivalents, reductions in CFC emissions compensate for increases in emissions of the other greenhouse gases.
 

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