*2.3. Linear Weighting Method*

To measure the comprehensive pollution from three major industrial polluting sources wastewater, waste gas, and solid waste—we used the linear weighting method to calculate the comprehensive pollution index (*F*) based on data for pollution emissions:

$$F\_{\bar{i}} = \sum\_{j=1}^{n} \mathfrak{x}\_{\bar{i}\bar{j}} \times w\_{\bar{j}}$$

where *xij* is the normalized value of polluting emission *j* in year *i*, and *wj* represents the weight of polluting emission *j*, calculated as follows:

$$w\_{\bar{j}} = \frac{\sigma\_{\bar{j}}}{\sum\_{\bar{j}=1}^{n} \sigma\_{\bar{j}}}$$

where *σ* is the standard deviation of observations *xij*.
