Nitrogen isotope variations in camphor (Cinnamomum Camphora) leaves of different ages in upper and lower canopies as an indicator of atmospheric nitrogen sources

► Camphor leaves showed high δ15N values near roads and low values near the industrial area. ► The δ15N values of camphor leaves near roads increased with time of exposure. ► The δ15N values of camphor leaves near the industrial area decreased with time of exposure. ► More positive foliage δ15N values were found in the upper canopies near roads. ► Near the industrial area, the upper canopies showed more negative foliage δ15N values.