In:
Environmental Sciences Europe, Springer Science and Business Media LLC, Vol. 24, No. 1 ( 2012-12)
Abstract:
The decreasing NO X concentrations at urban measurement stations in Germany are in agreement with the reduction of NO X emissions from vehicular traffic. However, the measured NO 2 concentrations are stagnating nationwide. In 2010, at more than the half of the urban measurement stations in Germany, annual mean values for NO 2 exceeded the new Europe-wide limit value of 40 μg/m 3 (20 ppbv) NO 2 . Similar findings are reported from many other member states of the European Union. Results The observed trend of the airborne NO 2 concentrations has different reasons. Firstly, the NO 2 /NO x emission ratio has increased significantly during the last two decades. Furthermore, secondary NO 2 , caused by the titration reactions of NO with ozone (O 3 ) and peroxy radicals (RO 2 ), is responsible for the major fraction (approximately 70%) of the measured NO 2 . However, secondary NO 2 shows a highly nonlinear dependency on NO x and thus, is decreasing much more slowly than expected from the decreasing NO x levels. Based on the results from the present study, the increased NO 2 /NO X emission ratio can only explain a minor fraction of the observed high airborne NO 2 concentration in the city center. Conclusions A further reduction of primary NO 2 emissions, due to improved exhaust gas treatment, will not have a strong influence on urban NO 2 levels, and a further significant reduction of the NO X emissions, in particular from vehicular traffic, is necessary in order to meet the annual mean limit value for NO 2 of about 20 ppb in the future.
Type of Medium:
Online Resource
ISSN:
2190-4707
,
2190-4715
DOI:
10.1186/2190-4715-24-21
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2012
detail.hit.zdb_id:
2593962-2
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