图16  长宁水氡月均值及其校正值曲线

      （a）原始值；（b）一般多项式分段曲线拟合值；

      （c）原始数据与一般多项式分段曲线拟合值之差

Fig.16  Curves of monthly mean value of radon content in

        groundwater and its corrected value at Changning station