The coupling between biological pump export and air-water exchange of organophosphate esters in a subtropical water environment

Abstract

Organophosphate esters (OPEs) are well-known persistent organic pollutants with their ubiquitous environmental presence and adverse ecological and human health impacts. To study the transport and fate of OPEs in a subtropical environment, nine OPE compounds were analyzed in the gas phase (air samples), dissolved phase (water samples), and plankton samples collected over one year from or in the vicinity of an urban lake in Guangzhou, South China. The mean concentrations of ∑9OPEs were 2.93 ± 1.68 ng/m3 in the air, 455 ± 236 ng/L in the dissolved phase, 81.3 ± 41.2 ng/L in phytoplankton, and 4.79 ± 1.94 ng/L in zooplankton. Although the compositional profiles of OPEs varied among different media, tris (1-chloro-2-propyl) phosphate (TCPP) was the predominant OPE in most samples. Less hydrophobic OPEs such as TCPP and tris (2-chloroethyl) phosphate (TCEP) had lower bioaccumulation potential in the lake. The biological pump export played an important role in eliminating OPEs from the surface water, with fluxes ranging from 30.5 to 361 ng/m2/d. The more phytoplankton biomass in surface water, the greater the role of the biological pump. The fugacity fractions and air-water exchange fluxes suggested that TCPP and tris (1,3-dichloro-2-propyl) phosphate (TDCP) would enter the urban lake by gaseous deposition. Nevertheless, the lake acted as an important “secondary source” for TCEP and triphenyl phosphate (TPhP). The bio-pump might influence the air-water exchange processes of OPEs.