Atmospheric Chemistry and Physics

Abstract. In anthropogenically influenced atmospheres, sul-phur dioxide (SO2) is the main precursor of gaseous sul-phuric acid (H2SO4), which in turn is a main precursor for at-mospheric particle nucleation. As a result of socio-economic changes, East Germany has seen a dramatic decrease in an-thropogenic SO2 emissions between 1989 and present, as documented by routine air quality measurements in many locations. We have attempted to evaluate the influence of changing SO2 concentrations on the frequency and inten-sity of new particle formation (NPF) using two different data sets (1996–1997; 2003–2006) of experimental particle num-ber size distributions (diameter range 3–750 nm) from the at-mospheric research station Melpitz near Leipzig, Germany. Between the two periods SO2 concentrations decreased by 65 % on average, while the frequency of NPF events droppe