Figure 5 5-day retroplume (1 km footprint) for a receptor at an altitude of 1 km above (a) Baicheng; (b) Daan and (c) Songyuan corresponding to “A”, “B”, “C” as marked in Fig. 3. (d) 5-day retroplume (i.e., 100 m footprint) for a receptor at an altitude of 100 m above Baicheng sites; (e) 5-day retroplume (3 km footprint) and (f) 5-day retroplume (100 m footprint) for a receptor at an altitude of 3 km above Baicheng sites at 16: 00 LT on 30 July.