Analysis of elements in soluble and insoluble fractions of rain water by PIXE

Samples of rainwater were collected and filtered through a 47 mm θ Nuclepore filter (pore size 0.4 μm, 10 μm thickness), to separate soluble and insoluble materials. Yittrium solution was added to the samples as the internal standard, and the samples were concentrated to 1 ml by evaporation. 50 μl portions of the concentrated sample were dried on a Mylar film (4 μm thickness) and irradiated by the proton beam of 10 nA (2.50 MeV) from a Van de Graaf accelerator. The insoluble part of the sample on the Nuclepore filter was also irradiated in the same way. 10 elements K, Ca, Ti, V, Mn, Fe, Ni, Zn and Pb were determined with an accuracy of about 10%. The measured values were cross-checked by atomic absorption spectrometry. The concentrations of most elements were much higher in the soluble fraction, but soil derived elements such as Ti, Fe and Mn had considerably higher concentration in insoluble fractions.