Reliability and comparability - crucial aspects of research on atmospheric precipitation

ISSN： 0306-7319

Source： International Journal of Environmental and Analytical Chemistry, Vol.89, Iss.8-12, 2009-01, pp. : 901-916

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Abstract

The paper presents some research problems concerning the use of different methodologies, particularly focusing on reliability and comparability based on the authors' own research and some literature. The differences involving such factors as the place, mode and frequency of sampling, kinds of samples taken, duration and method of storage from the time of sampling to the time of analysis, preparation of samples for analysis, and verification and interpretation of the results, were investigated. The most significant changes were observed in precipitation samples obtained as a result of different collecting procedures - both in terms of method and frequency. The differences in concentrations of some ions for the corresponding samples of wet and bulk deposition exceeded 100%. On the other hand, the equalisation of samples and results led to the differences in results reaching 20%. The results of analyses of precipitation samples collected within a certain time sequence (monthly) poured together in amounts proportional to the precipitation events, differed from the figures obtained for samples collected on a daily basis and averaged. The greatest differences were observed in the pH and in concentrations of [image omitted], [image omitted], and Ca2+. The changes of the composition of precipitation samples stored at a variety of conditions were also investigated. The greatest changes were observed for [image omitted] [image omitted], and [image omitted] concentrations. Changes in pH during storage could even range over 1.6 units, which corresponded to more than a 15-fold difference in H+ concentrations. Evaluation of analytical methods applied with the verification of the validation parameters has been also presented. Moreover, data verification and interpretation by a different method, e.g. comparing the measured value of conductivity with the calculated one or balancing the determined cations and anions, as well as use of statistics (including chemometric techniques), are presented.