图31 无锡化肥厂井 (a)水电导日均值，(b)氟离子电极电位测值日均值，

     (c)氯离子电极电位测值日均值曲线

Fig.31  Curves for daily mean value of electric conductance(a), electrode potential

        of Fˉ(b) and Clˉ(c) in water at the well of Wuxi chemical fertilizer

        factory