Protocol for analysis of trace metals and other ions in filtered and unfiltered fogwater

A preparative method for the analysis of soluble and total (soluble+insoluble) acidic fogwater fractions was developed. The soluble fraction was obtained by filtration through a 0.22-μm Millex filter without noticeable differences whether the filtration occurred before or after the sample dilution. Besides, after the test of different HNO3 concentrations, it appeared that the total (soluble+insoluble) fraction could be dissolved prior to analysis by 1.12 M HNO3. This method of dissolution was validated by comparison with another method commonly used for mineralisation of soil samples. The two fractions (soluble and total) were analysed using the same analytical method: inductively coupled plasma emission and/or mass spectroscopy. Using the same method for both fractions, we minimised the impact of systematic errors. The developed method was applied to 72 fog samples collected in an urban area (Strasbourg, East of France). They were analysed for their soluble and total fraction for Mg, Ca, Fe, Mn, Zn, Al, Cd, and Pb. These fog samples were also analysed by ion chromatography for Cl−, NO3−, SO42−, Na+, NH4+, K+, formate, and butyrate. Finally, the calculation of the ionic balance and the percentage differences was used to verify the ion analysis.