Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Although extensive epidemiological study has implicated high arsenic content in artesian well water in the endemic area, there is more to learn about the etiology of the disease. In this study, effort is paid on multielement determination and arsenic speciation in order to find out whether the trace element concentration pattern in well water in the Blackfoot disease endemic area is different from those of two control areas. Experimental results indicate that the concentrations of Fe, P, Na, and Ba in well water in the Blackfoot disease endemic area are found to be significantly higher than those of the controls, but they are still below the drinking water standard. The total arsenic in well water in the endemic area (671 +/- 149 ppb) is much higher than that of one normal control area of Hsin-Chu (< 0.7 ppb), but is a similar level as that of other control areas of I-Lan (653 +/- 71 ppb) where no Blackfoot disease has ever been found. It was also found that the insoluble arsenic in the endemic area (21.9 ppb) is much higher than that in two control areas (< or = 1.8 ppb), and the concentration ratio between As(III) and As(V) species in the endemic area (2.6) is much lower than that in one of the control areas, where the total arsenic is also high (14.7). The possible connection of Blackfoot disease with trace elements, arsenic species, and possibly other as yet undefined environmental factors in the artesian well water, is discussed.
e -Production cost (E) and reliability of generation system can be evaluatRd by probabilistic production simulation. The derivatives of FC and reliability refer to the changes of simulation results due to marginal variation of a specific system parameter, which may be an hourly load level, or the unit capacity (UC) or forced outage rate (FOR) of a generating unit. 4 recursive computational procedure. derived from the cumulant method for efficiently calculating these derivatives is proposed. The procedure is applicable to the derivatives with respect to load, UC or FOR. Moreover, the procedure could handle any number of cumulants without additional theoretical developnent or software implementation effort. The general accuracy of this procedure and three applications are presented.
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