TEMPORAL AND ELEVATION-RELATED VARIABILITY IN PRECIPITATION CHEMISTRY FROM 1993 TO 2002, EASTERN ERZGEBIRGE, GERMANY FRANK ZIMMERMANN 3,∗ ,J ¨ ORG MATSCHULLAT 1 , ERIKA BR ¨ UGGEMANN 2 , KIRSTEN PLEßOW 1 and OTTO WIENHAUS 4 1 TU Bergakademie Freiberg, Interdisziplin¨ ares ¨ Okologisches Zentrum, Brennhausgasse 14, D-09599 Freiberg, Germany; 2 Leibniz-Institut f ¨ ur Troposph¨ arenforschung, Leipzig, Germany; 3 TU Darmstadt, Institut f ¨ ur Angewandte Geowissenschaften, Fachgebiet Umweltmineralogie, Schnittspahnstr. 9, D-64287 Darmstadt; 4 TU Dresden, Institut f¨ ur Pfl ¨ anzenchemie und Holzchemie ( ∗ author for correspondence, e-mail: zimmer f@geo.tu-darmstadt.de; Tel: 49(0)6151 16 43 44, Fax: 49(0)6151 16 4021) (Received 25 June 2004; accepted 6 September 2005) Abstract. The Erzgebirge, part of the so-called former “Black Triangle”, used to represent the strongest regional air pollution of Central Europe. To test the hypothesis of deposition enhancement with height, an altitudinal gradient along a N-S transect from the Elbe river lowlands to the Erzge- birge summit was chosen to investigate chemical composition, elevation-related variability, temporal changes, and seasonal patterns of ion concentrations from 1993 to 2002. The following questions were to be answered: (1) Which role does orography play on the composition of precipitation?, (2) Does fog occurrence overrule the orographic influence?, (3) Are there changes in the past 10 years, and if so, why?, (4) Do relevant seasonal changes occur and why? Air streams from westerly and to a lesser degree south-easterly directions prevail. The average precipitation was ion-poor (23 μS cm −1 ) and acidic (pH 4.5). Sulphate still was the dominant anion (52.3–59.9 μeq L −1 ), while NH + 4 determined the cations (41.9–62.2 μeq L −1 ). Ion concentrations decreased with altitude to about 735 m a.s.l. and subsequently increased. The seeder-feeder effect largely explains the chemical composition of precipitation; enhanced in winter through snow crystals. Sub-cloud scavenging does not explain the observed patterns. Fog occurrence enhanced the observed effects at higher altitudes. Deposition amounts doubled from the lowlands to the Erzgebirge summit. From 1993 to 2002, acidity decreased by about 50%, mainly due to reduced SO 2 -emissions. Keywords: altitudinal gradient, fog, wet deposition, seeder-feeder, ionic balances 1. Introduction The Erzgebirge, the mountain range forming the northern border between the Czech Republic and Germany, is yielded the highest atmospheric SO 2 -loads of Central Europe (so-called Black Triangle). Westerly air streams prevail, with southerly winds as a secondary wind direction (Flemming, 1993; Goldberg et al., 1998). Under those southerly air streams, the Erzgebirge has been exposed to highly pol- luted air masses (Matschullat et al., 2000; Zimmermann et al., 2003), originating from combustion of sulphur-rich brown coal and heavy industry in the Northern Water, Air, and Soil Pollution (2006) 170: 123–141 DOI: 10.1007/s11270-006-2860-2 C  Springer 2006