Background levels of trace elements in rain and river waters in Japan

It is important to know the concentrations of trace elements such as uranium, thorium and lanthanoids in river and rain waters for evaluation of various environmental radioactive contaminations and of safety of those elements. Analysis in combination of high resolution-induction combination plasma-mass spectrometry (HR-ICP-MS) and ultrasound nebulizer (USN) has made it possible to detect those element at ng/l levels. A preliminary study on concentrations of those elements was performed to know their natural abundance in those waters. Water samples of 82 rivers in Japan collected from 1989-1991 and of rain collected in Kohtoh district, Tokyo and in Tsukuba city, Ibaraki Prefecture from October, 1991-March, 1993 were filtered and subjected to analyses by HR-ICP-MS and USN with SPEX mix standard. Accuracy was 2-5% (low resolution) and 5-10% (high resolution) and detection limit, 0.0007 ng/l (U)-2 ng/l (Fe). From the upper to down stream of the river, a gradual increase in the concentration of those elements as Li, V, Rb, Cs, Ba, Tl and U was observed, a rapid increase, as NO3-N, NH4-N, Na, K, Ca, Mg, PO4-P, SO4-S, Cl, Co, Zn and heavy rare earth elements, and an unaltered concentration, as Mn, Fe, Ni, Cu, Cd, Pb, Ga, Bi, Y and middle and light rare earth elements. A great variety in element concentrations was observed in the rain. For lanthanoids, Oddo-Harkins law was observed in both river and rain waters. (K.H.)