Isotopic composition of sulphates from meteoric precipitation as an indicator of pollutant origin in Wrocaw (SW Poland)

This paper describes the results of isotopic analyses of (i) hydrogen and oxygen in water (delta D-H2O and delta O-18(H2O)) and (ii) sulphur and oxygen in sulphates (delta S-34(sulphate) and delta O-18(sulphate)) from atmospheric precipitation collected within a one-year period between 25 May 2004 and 25 May 2005 in Wroclaw (SW Poland). The resulting equation of Local Meteoric Water Line for Wroclaw is delta D = 6.373 x delta O-18 - 0.047, (r(2) = 0.97, n = 32). The delta S-34(sulphate) varies from 1.1 to 4.2 parts per thousand (with an average of 2.5 parts per thousand), delta O-18(sulphate) varies from 9.0 to 16.7 parts per thousand (with an average of 13.8 parts per thousand) and delta O-18(H2O) varies from -0.8 to - 16.3 parts per thousand (with an average of - 8.2 parts per thousand). The above results indicate two main sources of sulphates in Wroclaw precipitation: (i) low-temperature secondary sulphates forming in situ in Wroclaw from the atmospheric SO2 as well as precipitation water (heterogeneous and homogeneous pathways oxidation) and (ii) high-temperature primary sulphates forming in rapid high-temperature hydratation of SO3- in an immediate proximity of industrial chimneys. We hypothesise that the secondary low-temperature type of sulphates is probably formed from the local sulphur and oxygen reservoirs, whereas the primary high-temperature type is allochthonous and it is probably transported from industrial areas located outside of Wroclaw.