PMF软件参数.doc

美国环保局认可的 EPA PMF 3.0 模型软件ignal to noise ratios (S/N=mean concentration/mean uncertainty) 信噪比S/N=平均浓度/平均不确定度 （方法不唯一） Coefficients of variation (CV=standard deviation/mean concentration) 变量系数CV=标准差/平均浓度 （标准差=） It is advised that FPEAK values range between ?1 and 1, with positive values causing extremes in the F matrix (values near 0 or 1) and negative values causing extremes in the G matrix. In the present work, FPEAK is zero for all PMF2 solutions, which corresponds to the default setting. The concentration values were used for the measured data, and the summation of the analytical uncertainty and one third of the detection limit value were used as the overall uncertainty assigned to each measured value. The missing data were replaced by the geometric mean of corresponding species, and four times of geometric mean were taken as the corresponding uncertainties. Values below the detection limit were replaced by half of the detection limit values, and their overall uncertainties were set at five sixth of the detection limit values. The uncertainty of the variables was calculated based on the detection limits and the concentration of each electrometer: 5/6 of the detection limit (DL) was used as corresponding uncertainty for data below the detection limit (BDL). The uncertainties for data above the DL were calculated according to the equation σij= DL/3 + c×xij, where σij= uncertainty, DL =detection limit, c = constant (0.1 if xij 3DL, 0.2 if xij≤ 3DL), and xij= concentration of the ith variable on the jth case. For stretches along which particle concentrations equaled to zero for a certain size range, the data were replaced by DL/2 for that size. FPEAK values between 0.2 and ?0.2 were tested to assess the in?uence of rotations on the solution, and the ?nal value was set to FPEAK = 0.