Soil microbial response to multipollutant exposure in megacity parks: a study in Beijing

Soil life revolves around microorganisms that are crucial for soil ecosystems and health. In megacities, the combined exposure of multiple pollutants exerts a significant impact on the structure and function of soil microorganisms; however, there is a lack of empirical studies on this topic. Hence, we conducted a study including urban parks in Beijing, People’s Republic of China. The results showed that bacteria were abundant in the soils of Beijing parks and that they had the same dominant groups but different rare groups. The dominant groups included Actinobacteria and Proteobacteria. Candidate phyla radiation bacteria, a large evolutionary radiation of bacterial lineages whose members remain mostly uncultivated, were the main specialists. Under the combined exposure of multiple pollutants, the structure of soil microbial communities in different parks tended to be similar. Community change due to pollutants (31%) was higher than that due to natural factors (2.4%). Among multi-pollutants, organophosphate esters (OPEs), led by dibutyl phthalate (DBP), had the highest influence on microbial abundance and distribution. An increase in DBP concentration decreased the abundance of Firmicutes, while the abundance of Synergistota was increased. The interaction among pollutants affecting the bacteria was different. Bis(2-chloroethyl) phosphate (BCEP), nickel and benzo[g,h,i]perylene (BghiP) influenced microorganisms by working with OPEs. High-molecular-weight polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP) and BghiP, mainly acted on functional genes and thus affected multiple biogeochemical cycles. Benzo[a]anthracene (BaA), BCEP, and arsenic were the primary pollutants affecting metabolic pathways. Our research deepens the understanding of the impact of urban environmental pollution on soil microorganisms.