Partitioning of 1,2-dichlorobenzene onto organic and inorganic aerosols

Volatile organic compounds (VOCs) are not expected to partition onto aerosols because of their high vapour pressure. Studies on gas-aerosol partitioning of VOCs have been limited because of the challenge in discriminating the small mass fraction of the VOCs in the aerosol relative to that in the gas phase. Here, we developed a bench-scale system to investigate the partitioning of a surrogate VOC, 1,2-dichlorobenzene (1,2-DCB), into inorganic and organic aerosols under different relative humidities (RHs) and temperatures. The partitioning coefficient (K-ip) of 1,2-DCB into succinic acid (SA) aerosol was, similar to 10x higher than those into ammonium sulfate (Am Sulf) aerosol. These K-ip corresponded to 0.23-3.27 pg 1,2-DCB mu g(-1) of SA aerosol and 0.02-3.82 pg 1,2-DCB mu g(-1) of Am Sulf aerosol for RH levels of 5-95 %. Sorption of 1,2-DCB onto Am Sulf aerosol followed the classic relationship between K-ip and RH, whereas that onto SA did not. For AmSulf aerosols, RHlevels exceeding 50% have a negligible effect on partitioning, in which the extremely low amount of 1,2-DCB partitioned into the aerosol via dissolution. The octanol-air partition (K-OA) model predicted the K-ip of 1,2-DCB for SA aerosol better than the saturated vapour pressure partition (P-i(0)) model, whereas the P-i(0) model predicted K-ip better than the K-OA model only when absorptive partitioning was considered.

Automated summary

Studies showed that the partitioning coefficient (K-ip) of 1,2-dichlorobenzene (1,2-DCB) into succinic acid (SA) aerosol was more than 10 times higher than that into ammonium sulfate (Am Sulf) aerosol. Different relative humidities also had an impact on the partitioning of 1,2-DCB into aerosols.