Abstract

In this study, the influence of traffic intensity on dewformation efficiency and chemistry is presented. The measurementswere conducted near the A4 motorway in SW Poland in almost flatland relief with intense agricultural activity. The dew/hoarfrost wascollected by means of insulated plain passive radiative condensersat three sites: AN and AS located in the close vicinity of themotorway (30 m) on the opposite sides of the road, and AR, representingrural background conditions beyond the motorwayinfluence. Measurements were conducted in two short campaigns inApril and September 2009 with 9 and 10 collection days respectively.The average daily efficiency of dew formation was 0.179 L/m2. Its value for AN, AS and AR was on average 0.170, 0.199 and0.173 L/m2, respectively. The efficiency of dew formation atmeasurement sites located on both sides of the road differed by upto about 200% during an individual dew episode. Maximum dailyvalue reached 0.389 L/m2. The average volume-weighted pH wasacidic and ranged from 4.29 (AS) to 4.58 (AR). The electric conductivity(EC) at all measurement sites was relatively low reachingon average 55.9 lS/cm for AN, 62.2 lS/cm for AS and 35.8 lS/cmfor AR. The average volume-weighted TIC parameter (total ioniccontent) reached the value of 0.62 meq/L (AN and AS) and0.38 meq/L (AR). Both EC and TIC values indicated stronginfluence of the motorway at sites located in its close vicinity (ANand AS). Depending on airflow direction during individual dewcollection events, AN or AS sites were situated alternatively onwindward or leeward side of the road, which distinctly influenceddew formation and chemistry: the leeward condenser was characterizedby smaller water volume, higher EC and higher TIC whencompared both with its windward counterpart and the backgroundsite. The ionic structure of the collected samples was similar at allmeasurement sites. The largest share had NO3- anion (28-32%)and Ca2? cation (22-25%). Thus, air pollution was relatively lowin the vicinity of the A4 motorway in SW Poland not exceeding thetypical values for urban background stations.

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