Performance of sulfation and nitration plates used to monitor atmospheric pollutant deposition in a real environment

Abstract

Sulfation and nitration plates were exposed outdoors for various periods of time to evaluate their performance in a real environment. These passive monitors are used to estimate the deposition of pollutants on metallic surfaces, and thus to evaluate the influence of the atmosphere on the corrosion. Single-column ion chromatography was used to determine the quantity of anions absorbed on the plates. This technique is better than other analytical procedures such as turbidimetry or colorimetry because passive monitors exposed in an atmosphere with a low degree of pollution can be analyzed without preconcentration. However, the pH of the sample to be injected on the Chromatographic column must be adjusted to between 6.0 and 12.0 in order to obtain reproducible sulfate values. For sulfation plates, the additivity of the deposition process is excellent for a period of exposure up to 3 months, with a reproducibility of about 2%. For nitration plates, the deposition process is not cumulative due to a physical change of the monitor during exposure. The correlation between the amounts of sulfate found on sulfation and nitration plates was also examined.