X-ray fluorescence techniques in analysis of environmental pollutants

An energy dispersive X-ray fluorescence method is being used for the analysis of pollutants in particulate matter in the air, in plant material and in water. The measuring system consists of an Si(Li) detector, 109Cd, 238Pu and 55Fe sources of primary radiation, and a multichannel analyser with a minicomputer on-line. For low-Z elements a helium flow chamber is used. Methods of preparing and calibrating standards are discussed. Some examples of applying the method in pollution studies in industrialized, urban and other areas are given. The range of detection limits for metals in air-borne particulate matter is 10 to 1000 ng/m3. Plant material has been analysed either in the form of dried and pressed pellets or as ash left after combustion of the sample; detection limits for pollutant elements are 70 to 700 μg/cm2 of the solid sample. Metal pollutants in water were concentrated by selective ion exchange or precipitation with sodium diethyldithiocarbamate (NaDDTC). The chelating ion exchanger (Chelex-100) was used for determining trace metals in groundwater and rain water. The kinetics of the exchange reaction, the influence of water pH-value and the Ca and Na ions present have been studied. The estimated limit of determination is 10 pp109 for Mn, Fe and heavier metals. The NaDDTC reagent can be used for simultaneous determination of several metals in 'fresh' water as well as in saline solutions. The precipitate formed is filtered using a membrane filter and analysed by the X-ray fluorescence method. The limit of determination is 5 to 10 pp109 depending on the element to be determined. (author)