Air-Sea Exchange and Atmospheric Deposition of Phthalate Esters in the South China Sea

Phthalate esters are ubiquitous in theglobal environmentand subject to atmospheric and oceanic transport to the South ChinaSea. Phthalate esters(PAEs) have been investigated in paired air andseawater samples collected onboard the research vessel SONNE in theSouth China Sea in the summer of 2019. The concentrations of n-ary sumation (7)PAEs ranged from 2.84 to 24.3 ng/m(3) with a meanof 9.67 & PLUSMN; 5.86 ng/m(3) in air and from 0.96 to 8.35ng/L with a mean of 3.05 ng/L in seawater. Net air-to-seawater depositiondominated air-sea exchange fluxes of DiBP, DnBP, DMP, and DEP,while strong water-to-air volatilization was estimated for bis(2-ethylhexyl)phthalate (DEHP). The estimated net atmospheric depositions were 3740t/y for the sum of DMP, DEP, DiBP, and DnBP, but DEHP volatilizedfrom seawater to air with an average of 900 t/y. The seasonally changingmonsoon circulation, currents, and cyclones occurring in the Pacificcan significantly influence the concentration of PAEs, and alter thedirection and magnitude of air-sea exchange and particle depositionfluxes. Consequently, the dynamic air-sea exchange processmay drive the transport of PAEs from marginal seas and estuaries towardremote marine environments, which can play an important role in theenvironmental transport and cycling of PAEs in the global ocean.