Sources and sinks evaluation of PAHs in leaves of Cinnamomum camphora in megacity: From the perspective of land-use types

Abstract

Direct and indirect effects of complex urban land-use types on polycyclic aromatic hydrocarbons (PAHs), including their total amount, composition, sources and sinks, were evaluated from 84 sampling points in the megacity of Shanghai. We measured the content and composition of PAHs adsorbed by the leaves of Cinnamomum camphora and established buffers of different radii at each point. The different land-use types areas were counted therewith to investigate their effects on the sources and sinks of PAHs in leaves. Results showed that the average value of PAHs in the leaves was 3014.06 ± 1879.713 ng g−1. The substance profiles were dominated by medium-molecular-weight (MMW, 54%) and high-molecular-weight (HMW, 45%) PAHs, and these fractions were much higher than that of low-molecular-weight (LMW, 1%) PAHs. Through correlation analysis, the land-use type of industry, road, business, and residential areas were initially assessed as the sources of PAHs, whereas water, farmland, and woodland areas were sinks. Lasso regression proved that road and residential areas have proven to be the main source of PAHs in Shanghai, rather than industry and business areas. Woodland was found to be a better sink for PAHs than water and farmland. Sources and sinks of PAHs with different benzene rings also differed greatly: the main sources of MMW PAHs were industrial emissions and commercial activities, with the main sinks being water and woodland; the primary sources of HMW PAHs were traffic emissions and residential activities, with the main sink being farmland. This study assessed the sources and sinks of PAHs in cities, from the perspective of varied effects of different urban land-use types on PAH composition and spatial distribution, and bridged the gap between urban PAHs alleviation and the land-use planning in megacity, with instructive significance for planning policy development.