## 1 Introduction  
Particulate matter (PM) concentrations are known to have severe impact not only on global climate and atmospheric chemistry ([1] and references therein) but also on human health [2; 3]. Regarding the findings from these studies, the European Commission (EC) has established limit values for PM in the air quality directive 2008/50/EC. Therein, a daily limit for PM\({}_{10}\) of 50 \(\upmu\)g/m\({}^{3}\) is stated, which may be exceeded on 35 days per year. Also for other PM fractions such as PM\({}_{2.5}\) limit values are given by the EC; however, within this study, only PM\({}_{10}\) is investigated. Close to populated areas, exceedance of the limit values of PM\({}_{10}\) are caused mainly by anthropogenic sources such as energy production, traffic and industry, although natural sources can contribute as well [4]. The relative importance of the different sources depends strongly on regional and temporal scales, often the urban impact adds to a marked initial pollution load [5; 6]. Especially in the Mediterranean region natural mineral dust sources are known as important contributors to PM\({}_{10}\) exceedance [7; 8; 9]. If exceedance of limit values can be attributed to a natural phenomenon such as particle intrusion from arid regions (e.g., the Sahara, or the Arabian or Lybian deserts), they can be discounted. The EC provides a commission working staff paper [10] describing this procedure for Spain. In the underlying study of [PERSON] et al. [11] a methodology for quantifying the daily African PM\({}_{10}\) load during dust outbreaks for Southern Europe is proposed, using Spain as study area. They determined the regional background load via applying a monthly moving 30 th percentile to the PM\({}_{10}\) load at a regional background site, excluding the days affected by African dust transport and validated the methodology via crustal loads determined by chemical speciation of PM\({}_{10}\) filters. Within the working staff paper of the EC it is clearly stated that the use of this approach has not been validated for other countries and that no certainty exists on its accuracy for application. A recent study of [PERSON] et al. [7] investigates the applicability of the EC methodology for Italy, describing limitations and drawbacks in the identification of desert dust days as well as in the quantification of the regional background load. Specific solutions for Italy are proposed and introduced. In their adapted methodology, they use each site as reference for its own background load, reduced the time window over which the background load is determined and introduced an automatic, model-based method to identify desert dust affected days. It is well known that desert dust outbreaks regularly occur in Austria [12; 13; 14], although their impact is less pronounced than in the Mediterranean region. Their influence on air quality has not been investigated so far and a discussion of the EC methodology for the subtraction of desert dust contributions is completely missing. This study presents the first validity check of the applicability of the EC methodology for Austria. This is of high relevance as both facts, exceedances of short-term limit values of PM\({}_{10}\) and the influence of desert dust occur in Austria. The critical application of a methodology developed for the Mediterranean region to a country within Central Europe is of special interest for continuative use. We evaluate whether long-range transport of desert dust can be quantified via the EC methodology and whether the respective subtractions would influence the exceedance of the short-term limit value for PM\({}_{10}\), taking the urban-traffic sampling site Graz Don Bosco as main example. We compared three different stations for their suitability to be regarded as the regional background station, required for applying the EC methodology.