X-ray determination of brushite (CaHPO4 · 2H2O) suspended in the water of the Neckar River,west Germany

The results reported in the present paper are a by-product of a detailed study of the heavy metals (Zn, Pb, Cu, Cd, Co, Ni, Cr, Fe, Mn) carried by the Upper Neckar River, Germany. The purpose was to determine the pollution by industrial waste of the river waters (Abadian 1976). In order to elucidate the various mechanisms of heavy-metal transport in the river, the clay of the bottom sediments and that carried in suspension was analysed for the metals at a number of locations and subjected to X-ray diffraction for the determination of the clay minerals present. The bottom sediments consist of kaolinite, illite, random interstratification (of mica and expandable layers) and quartz. In some samples chlorite and calcite were detected as well. The mineral content of the suspended load was collected by pressure filtration on porous ceramic plates. The clay minerals determined by subjecting the plates plus filtered residue to X-ray diffraction were the same as in the sediments. In addition to the clay-mineral reflections, three of the samples obtained from suspension (locations 2, 3, and 5 in the map, Fig. 1) showed the strongest diffraction line of the mineral brushite, CaHPO₄·2H₂O, at 7.6 Å. In one sample (location 2) three more lines of brushite were observed. The occurrence of brushite in the Neckar may be taken as a mineralogical indicator of the pollution of the river, because the following materials may be possible sources of the phosphate: artificial fertilizers, liquid manure, water softeners, detergents, and industrial waste waters.