Evidences for the influence from key chemical structures of per- and polyfluoroalkyl substances on their environmental behaviors

In recent years, perfluoroalkyl and polyfluoroalkyl substances (PFASs) have received widespread attention from the international community due to their persistence, long range atmospheric transport (LRAT), bioaccumulation and toxic. This study carried out the atmospheric and precipitation observation in Beijing for nearly one year, and firstly simultaneously observed the pollution characteristics of ultra short-chain, short-chain, long-chain PFASs and their main isomers, focusing on their gas-particle partitioning mechanism and dry and wet deposition characteristics. The results showed that the total concentration of PFASs was 3,415±2,932 pg m^-3, of which ultra short-chain PFASs accounted for the highest proportion (55%), followed by short chains (41%) and long chains (3.9%). The proportion of short-chain PFASs was greater than that of long-chain PFASs which may be because short-chains have been produced and consumed as substitutes for long-chain PFASs. After deducting PFASs in the aqueous phase of particulate matter, the gas-particle partitioning coefficients (-7.04 m³ μg to -5.49 m³ μg) were about 3–4 units smaller than the previous results (-2.77 m³ μg to -1.51 m³ μg), which could more accurately reflect the phase partitioning characteristics between the gas phase and the hydrophobic phase of particulate matter. All PFASs and their main isomers were more distributed in the gas phase, followed by the aqueous phase of particulate matter and the hydrophobic phase of particulate matter. Dry deposition was dominant in the atmospheric deposition of each PFAS and isomer, but the relative contribution of dry deposition was significantly different. It was found that the gas-particle partitioning coefficient can be influenced by key chemical structures such as carbon chain length, functional group type, and isomer structure. Furthermore, the gas-particle partitioning can influence the dry and wet deposition of PFASs. Specifically, PFASs with longer carbon chains, carboxylic acid functional group or branched chain structures had larger gas-particle partitioning coefficients and can be more distributed in the hydrophobic phase of particulate matter, and their relative contributions of dry deposition were smaller.