Abstract
We investigated long term time variation of dissolved species in the water sampled from the Sagami River and its tributaries. The sampling had been done monthly from May 1993 to April 1999 at 30 sampling sites of Sagami River water system. Twenty-four major to trace elements (Li, Mg, Al, Ca, V, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, W, Tl, Pb, U) were determined using conventional Q-pole ICP-MS with direct nebulization. Chemical oxygen demand, alkalinity, pH, EC were also determined. The data accumulated for 6 years (except Ca, Fe, Ag, W, Tl) were examined using Fast Fourier Transformation (FFT) to extract dominant periodisities, their magnitudes and phases. Clear seasonal variations (12 months period) were observed for many elements at many sampling points especially at down stream area. Aluminum, Cs, V had concentration maxima in summer, while Mg, Mn, Ni, Zn, Mo, U had maxima in winter. On the other hand, Sr and Ba scarcely showed seasonal variation. It can be considered that the seasonal variations may be caused by either anthropogenic origin such as irrigation, wastewater discharge from industry or natural reason such as water temperature, pH, redox condition, water flux, activity of micro-organism in the water. In some cases, we found strong correlation with irrigation condition, water flux (Ni, Mo at down stream area) . In another case, activity of micro-organism could control the variation (Ni at down stream of reservoir, Lake Sagami and Tsukui) . However, we did not find any correlation with pH, and water temperature may not be a main controlling factor. Thus it is difficult to explain the seasonal variations of all elements with single factor. Even the same element at different sampling site may have different factor (s) of variation.
