Fig. 6. (a) Loading values of 20 companies in the 2nd principal component (PC2) and contribution ratios of different sources in the critical companies in PC2 in (b) 2012, (c) 2013, and (d) 2014. EC, L/UL, WWTP, OLS, and CT denote equipment component, loading/unloading, wastewater treatment plant, oil-water separator, and cooling tower, respectively. 