UC San Diego

Phthalates (Phthalic Acid Esters; PAEs) are widely used toxic plasticizers, and their contamination in oceans and air is widespread due to their leachability. Previous studies have detected PAEs in air and water in remote marine environments worldwide, suggesting their transfer from the ocean to the atmosphere. However, no prior work has quantified PAE enrichment in the ocean surface layer or in marine aerosols. Here, we investigate the transfer characteristics and enrichment factors (EFs) of three common PAEs: dimethyl phthalate (DMP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP), from artificial seawater to an artificial (i.e., palmitic acid) sea surface microlayer (SML) and in nascent sea spray aerosols (SSA). The relative extent of enrichment was found to depend on PAE hydrophobicity and volatility. DBP exhibited the highest EFs in both the artificial SML and nascent SSA compared to other phthalates. DBP EFs in the artificial SML from two independently prepared tanks were 34.3(±1.6) and 20(±3) when present alone and 21.1(±0.9) and 16(±3) when mixed with DMP and DEHP. DMP EFs in the artificial SML were 1.25(±0.10) and 5.45(±0.19) when alone and 1.47(±0.10) and 1.47(±0.07) when mixed. DBP was also significantly more enriched than DMP in nascent SSA, with EFs of 28800(±1300) and 16000(±7000) when alone, and 57400(±2500) and 35000(±8000) when mixed. DMP EFs in SSA were much lower, with values of 6(±12) and 450(±50) when alone and 3(±1) and 542(±24) when mixed. EFs for DEHP were inconclusive due to potential matrix effects, contamination, or degradation. Greater EFs were measured when particles with Dp > 300 nm were absent, suggesting a size dependence in phthalate enrichment in SSA, consistent with other contaminant enrichment studies. These results demonstrate, for the first time, that the sea surface layer and sea spray aerosols may strongly enrich certain PAEs, particularly DBP. This highlights the importance of the ocean surface in mediating the transfer of toxic phthalates from the ocean to the atmosphere.