Effects of perfluorinated compounds homologues on chemical property, microbial composition, richness and diversity of urban forest soil

Perfluorinated compounds (PFCs), as an important class of new persistent organic pollutants, are widely distributed in the environment. Yet the effects of different types and concentrations of PFCs on soil microbial community in urban forest ecosystems are remain uncertain. Here, two typical PFCs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), were selected to carry out a pot experiment in greenhouse with singly and joint treatment at different concentrations, to examine their effects on composition and diversity of soil microorganisms and availability of soil macronutrients by using high-throughput Illumina sequencing approach. The results showed both PFOA and PFOS application significantly increased soil NO3--N and NH4+-N content, but did not alter total phosphorus content, compared to the control check (CK) treatments. Total po-tassium content was reduced in PFOA treatments but increased in PFOS and PFOAxPFOS treatments. The most dominant bacterial phylum was Chloroflezi in low and medium PFCs concentrations and the CK treatments, but it was switched to Acidobacteria in high concentrations. No obvious change was detected for the composition of the dominant fungi community in PFCs treatments compared to the CK treatments. With the increase of PFCs concentrations, soil bacterial richness decreased but its diversity increased, whereas the richness and diversity of fungal community usually decreased. Redundancy analyses revealed that soil fungal community was more sensitive to PFCs pollutants than soil bacterial communities. Further data analysis revealed by structural equa-tion model (SEM) that the PFCs exposed for 60 days indirectly affects the diversity and richness of soil bacteria and fungi by directly affecting NO3--N and NH4+-N content. The results suggested the concentration of PFCs pollutants played a primary role in determining the composition, richness and diversity of forest soil microbial communities.

Automated summary

Perfluorinated compounds (PFCs) are a class of new persistent organic pollutants widely found in the environment. This study examined the effects of two typical PFCs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), on the composition and diversity of soil microorganisms and the availability of soil macronutrients in urban forest ecosystems. The results showed that PFOA and PFOS application significantly increased soil nitrate and ammonium content, while total phosphorus content remained unchanged. Total potassium content decreased in PFOA treatments but increased in PFOS and PFOA-PFOS combined treatments. The dominant bacterial phylum shifted from Chloroflexi to Acidobacteria with increasing PFCs concentrations. Fungal community composition did not change significantly in response to PFCs treatments. Soil bacterial richness decreased but diversity increased, while fungal richness and diversity generally decreased with increasing PFCs concentrations. Soil fungal community was found to be more sensitive to PFCs pollutants than bacterial communities. Structural equation modeling revealed that PFCs exposure indirectly affected the diversity and richness of soil bacteria and fungi by directly impacting nitrate and ammonium content. The concentration of PFCs pollutants played a primary role in determining the composition, richness, and diversity of forest soil microbial communities.