Figure 3

Air concentration of PCB28 in 2005: (a) January to March, (b) April to June, (c) July to September, and (d) October to December. The maps were drawn by the software of Surfer 9.0, http://www.goldensoftware.com/.
Air concentration of PCB28 in 2005: (a) January to March, (b) April to June, (c) July to September, and (d) October to December. The maps were drawn by the software of Surfer 9.0, http://www.goldensoftware.com/.