Parent and Substitute Polycyclic Aromatic Hydrocarbon Reduction in Urban Rivers—Benefits of the Energy Transition Policy from 2009 to 2017 in Beijing, China

The impact of the policy of coal-fired reduction and clean energy growth promoted in Beijing, China, during the 12th and 13th Five-Year Plan Period (2011–2020) on polycyclic aromatic hydrocarbons (PAHs) and typical substituted PAHs (SPAHs) in the urban rivers has largely been unknown. Here we show the concentrations of ΣPAHs and methyl PAHs (ΣMPAHs) in urban rivers from 2009 to 2017 decreased from 390 ± 102 to 135 ± 74 ng/L and from 125 ± 34 to 24 ± 16 ng/L, respectively, whereas oxygenated PAHs (ΣOPAHs) maintained at 109 ± 9 to 119 ± 62 ng/L. The reduction of PAHs and MPAHs in rivers was mostly contributed by the reduction in wastewater treatment plant (WWTP) influent (80 and 88%), rather than WWTP upgrading (8 and 3%) or other sources (12 and 9%). The emission reduction of PAHs and MPAHs from domestic coal, coking coal, industrial coal, diesel, and fuel oil was supposedly primarily responsible for the reduction of PAHs and MPAHs in the WWTP influent. The reduction of PAHs and MPAHs was a benefit of the reduction of coal, diesel, and fuel oil in mining, manufacturing, construction, electricity and heating production and supply, living consumption, and tertiary industries.