Tadashi Shimamura

Long-term variations in dissolved trace elements in the Sagami River and its tributaries (upstream area), Japan

We investigated long-term variations in dissolved chemical species in water sampled from the Sagami River and its tributaries, Japan. The samples were taken monthly from May 1993 to April 2000 at 28 sampling sites in the Sagami River system. In this paper, we concentrate on 17 sites in the upper catchment. 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 by using conventional Q-pole ICP-MS with direct nebulizalion. Water flux was measured from 1995. The data for most species were subjected to fast Fourier transformation (FFT) to extract dominant periodicities, their magnitudes, and their phases. Clear seasonal variations were observed for Al, V, As, Rb and Cs at some sampling points, especially in the tributaries. The seasonal variations may be due to either anthropogenic causes, such as irrigation or wastewater discharge, or natural causes, such as water temperature, pH, redox condition, water flux, or activity of microorganisms. We found no correlation with pH. Water temperature may not be a main controlling factor, although the seasonal variability would be correlated with it. Hydrologic factors may have only minor effects. We suggest that most of the seasonal variation might be correlated with the irrigation of rice paddies. It was difficult to identify all the causes of the seasonal variability. To investigate interannual trends, we used centered 12-month moving averages to eliminate seasonal variations. The water quality of the uppermost streams was generally constant, being controlled by springs on Mt. Fuji. However, in 1993 and 1998, V, As, Rb, Cs and U were depleted briefly, possibly by dilution by overflow from Lakes Kawaguchi and Yamanaka. Hydrologic factors may be more important for interannual variability than seasonal variability. Some heavy trace elements (Zn, Ni, Cd and Sb) showed very irregular variations with high concentration peaks. These elements were discharged from either factories or abandoned mine tailings.

Determination of trace impurity rare earth elements in high-purity rare earth element samples using high-resolution inductively coupled plasma mass spectrometry

Trace impurity rare earth elements in high-purity Y2O3 and Gd2O3 were determined using high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). Interference problems from GdO, GdH and GdOH on Tb, Yb, Tm and Lu were overcome by using doubly charged ions for detection. The mass resolution was set to 400, which is much higher than the normal resolution (80–90) of a conventional quadrupole mass filter and much lower than the standard setting for ICP-MS in the high-resolution mode. As a result, the transmission decrease that occurs with a quadrupole mass filter if increased resolution is used was not a problem. The only controlling factor for the sensitivity was the production rate of doubly charged species. Hence optimization was applied to maximize the proportion of doubly charged species. The detection limits obtained were 0.05–3 ng 1–1 in solution. If singly charged ions were used, the detection limits were 5–30 pg 1–1. Determinations of the trace rare earth elements in three Y2O3 and three Gd2O3 test samples were performed. The concentrations of the trace rare earth elements were found to be variable between the samples.

Aging effects of major and trace elements in rat bones and their mutual correlations

The concentrations of 29 major to trace elements in rat bones (femur) aging from 5 to 113 weeks old were determined. The samples were decomposed by high purity nitric acid and hydrogen peroxide. Nine elements (Na, Mg, P, K, Ca, Fe, Ni, Zn, and Sr) were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and 20 elements (Li, B, Al, V, Cr, Mn, Cu, As, Se, Rb, Mo, Ag, Cd, Sb, Cs, Ba, W, Tl, Pb, and U) were determined by inductively coupled plasma mass spectrometry (ICP-MS). Aging effects on these elements and mutual elemental correlations were investigated. The concentrations of Ca, P and Na increased in the initial stage of 5-17 weeks and then maintained constant values, whereas those of Mg, K, Mn, Sr and Ba showed decreasing trends of differing patterns. Furthermore, Cu, Zn and Mo showed increasing trends for a whole range of ages. Selenium showed a remarkable increasing trend with a factor of 10. The values of Na, Mg, P, K, Ca, Mn, Cu, Zn, Se and Mo in the age-matched rats distributed narrow ranges, indicating that the metabolism of these elements in bone was well-established. By contrast, those of Al, V, Ni, Ag, Cd, Sb, W, Tl, and U were distributed across a broad range. The metabolism of these elements was not well-established. A cluster analysis was performed using an elemental correlation matrix.

Determination of trace silicon in ultra-high-purity water by inductively coupled plasma mass spectrometry

Determination of trace levels of Si in ultra-high-purity water was performed by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). Instrumental background, especially from the plasma torch is a serious problem. To overcome this problem a careful preconcentration procedure was adopted. This procedure allows excellent quantification down to sub-ng l–1 level. Total Si concentration is obtained regardless of the chemical state of Si. Consequently, by subtracting ionic Si, determined by colorimetric analysis, from total Si, it may be possible to obtain the concentration of non-ionic Si. Total Si concentration levels in semiconductor-grade water samples ranged from 0.5 to 1.0 ng g–1.

Age-related effects of major and trace element concentrations in rat liver and their mutual relationships.

The concentrations of 22 major and trace elements in livers from rats aging from 5 to 113 weeks old were determined. The rats investigated were the same rats previously reported with respect to 29 elements in bones (femur) and 26 elements in kidneys. The samples were decomposed with high-purity nitric acid and hydrogen peroxide. Seven elements (Na, Mg, P, K, Ca, Fe and Zn) were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), and 15 elements (Mn, Co, Cu, As, Se, Rb, Sr, Mo, Cd, Sn, Sb, Cs, Ba, Pb and Bi) were determined by inductively coupled plasma mass spectrometry (ICP-MS). Analysis of variance (ANOVA) for age variations indicated that the concentrations of many elements, such as Mg, P, K, Mn, Fe, Cu, Zn, Sr, Mo and Cd, were almost constant across the ages of the rats with the exception of 5 weeks old (p > 0.05). Arsenic, Pb and Bi showed significant increasing trends, while Na and Co showed decreasing trends (p < 0.01). Selenium showed a decreasing trend except at the initial stage of 5-9 weeks old. Calcium, Rb, Sn, Sb, Cs and Ba showed significant age-related variations, but their patterns were not monotonic. The liver clearly contrasts with the kidneys, in which many elements showed significant age-related variations with increasing trends. The concentration ranges of Mg, P, K, Mn, Cu, Zn, and Mo were controlled within 15% across all ages of rats. The homeostasis of the aforementioned elements may be well established in the liver. The toxic elements, such as Cd, Pb and Bi, showed a narrow concentration range among age-matched rats.

Lead Isotope Ratio in Rainfall Collected by a Sequential Sampler in Central Tokyo

Rainfall at central Tokyo was sequentially collected with a 1-mm precipitation interval. Lead (Pb) concentrations and isotopic compositions of each fraction were precisely determined by an inductively coupled plasma-quadrupole mass spectrometry and a multiple collector-inductively coupled plasma-mass spectrometry, respectively. The results showed that (1) Pb concentration in rainfall decayed according to a power law function along with rainfall depth; (2) Pb isotope ratios clearly changed during a single rainfall event; (3) mixing model having four or more end members could explain the variations of Pb isotope ratio; (4) Pb in rainfall was probably affected by diesel vehicle emission control commenced on 1st October 2003. Concerning (3), candidates of end member were estimated as local materials, e.g., natural soil components, airborne particle matter, automobile exhaust gases and fly ash from a municipal incinerator.