Supplementary Information

Polychlorinated Naphthalenes (PCNs) in Chinese forest soil: will the

combustion-related emission become the major source?

Total number of Figures: 14

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Figure S1. Sampling sites and forests distribution. Red dots are the sampling sites. To illustrate the

relative position clearly, the sampling sites were moved slightly from original position. The

precise sampling location, including latitude, longitude and altitude, can be found in Table S1

from supportive information.

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Figure S2 The composition pattern in the O-horizon and the A-horizon at each sampling site

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Figure S3. ΣPCN concentrations (pg/g C) in the O-horizon (A) and the A-horizon (B). The stretch

values along a green color ramp indicate population density. Red lines outline four major

industrial zones in China, including Northeast Industrial Base, Bohai Economic Circle, Yangtze

River Delta and Pearl River Delta

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Figure S4 The regression of CN concentrations vs. TOC for each homologue group. A significant relationship (p<0.01) only was observed for tri-, tetra- and pent-CNs in the A-horizon.

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Figure S5 The regression of CN concentrations vs. annual average precipitation. A significant relationship (p<0.01) only was observed for tri-, tetra- and pent-CNs in the O-horizon.

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Figure S6. Factor loadings plots for PCN congeners in the A-horizon (A) and O-horizon (B), red squares indicate combustion-related CN congeners.

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Figure S7 The spatial distribution of relative abundance of CN-51 in the O-horizon. Red lines outline four major industrial zones in China, including Northeast Industrial Base, Bohai Economic Circle, Yangtze River Delta and Pearl River Delta

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Figure S8 The spatial distribution of relative abundance of CN-73 in the O-horizon and coke consumption in each province.

Figure S9 The profiles of stack gas samples from 11 typical coke plants in China and 6 O-horizon soil samples close to areas with the highest cokes consumption in Fig S8. CC, PC and QC represent the charging of coal (CC), pushing of coke (PC) and Quenching of coking (QC) through the coking process. WY sites (Wuyuezhai Mountain) are the closest to coke consumption areas. BC1, BC5 (Baicaowa Mountain) and SH4 (Saihanba Mountain) were also closed to mega cities.

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Figure S10 Latitudinal trends of PCN homologue groups at Shennongjia Mountain in the A- and O-horizons.

Figure S11 Latitudinal trends of PCN homologue groups at Jiugong Mountain in the A-horizons.

Figure S12 Latitudinal trends of PCN homologue groups at Longquan Mountain in the A-horizons.

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Figure S13 Latitudinal trends of PCN homologue groups at Daxinganling Mountain in the A- and O-horizons.

Figure S14 Latitudinal trends of PCN homologue groups at Baicaowa in the A-horizons. The number of quantifiable sites was less than four in the O-horizon samples, therefore the plots of elevation gradients were not displayed.

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