Fig. 9

Biplot for indicating potential sources. (a): ²⁰⁸Pb/²⁰⁶Pb vs. ²⁰⁷Pb/²⁰⁶Pb; (b): ⁸⁷Sr/⁸⁶Sr vs. ²⁰⁷Pb/²⁰⁶Pb). References: Yellow River sediment⁸¹; Loess⁸¹; Liao River sediment⁷⁵; Coal combustion^117,118; Automobile exhaust^98,119; Liaoning Dongsheng Pb Mine¹²⁰; North China aerosol^95,111; Atmospheric dustfall¹¹¹; Atmospheric aerosols²⁵; BB and LB (this study).