Spatial distribution and air-water exchange of organophosphate esters in the lower Great Lakes.

Organophosphate esters (OPEs) have been detected at elevated concentrations in the Great Lakes region, dwarfing other flame retardants, such as polybrominated diphenylethers (PBDEs), as chemicals of emerging concern (CECs). This prompted us to deploy polyethylene (PE) passive samplers in air and water column of the lower Great Lake region (Lake Erie and Lake Ontario) to detect gaseous and dissolved OPEs, evaluate their occurrence and spatial distribution, and estimate their air-water gas exchange fluxes. The median concentration of the total dissolved and gaseous phase OPEs detected (Σ9OPEs) were 95 ng L-1 and 404 pg m-3, respectively, during April-November 2014. Gaseous and dissolved concentrations were dominated by chlorinated compounds, in particular (tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloroisopropyl) phosphate (TCPP), while tri-n-butyl phosphate (TnBP) was the dominant non-chlorinated OPEs in both media. Decreasing concentration gradients from shoreline/nearshore to offshore sites for both gaseous and aqueous OPEs reflect anthropogenic influence from the adjacent rural and urban regions. The partial dependence of gaseous OPEs on temperature indicate the importance of volatilization from local sources, fresh emissions as well as advection from distant sources to air. Almost all OPEs underwent net gas-phase deposition to the lakes, dominated by TCEP and TCPPs with median fluxes of -3980 ng/m2/day and -1320 ng/m2/day; the exception was TnBP, which underwent volatilization with the median fluxes of 1980 ng/m2/day. For all air-water pairs, the gaseous diffusive fluxes were 2-4 orders of magnitude greater than the estimated particle dry deposition fluxes.

Depth Profiles of Persistent Organic Pollutants in the North and Tropical Atlantic Ocean.

Little is known of the distribution of persistent organic pollutants (POPs) in the deep ocean. Polyethylene passive samplers were used to detect the vertical distribution of truly dissolved POPs at two sites in the Atlantic Ocean. Samplers were deployed at five depths covering 26-2535 m in the northern Atlantic and Tropical Atlantic, in approximately one year deployments. Samplers of different thickness were used to determine the state of equilibrium POPs reached in the passive samplers. Concentrations of POPs detected in the North Atlantic near the surface (e.g., sum of 14 polychlorinated biphenyls, PCBs: 0.84 pg L(-1)) were similar to previous measurements. At both sites, PCB concentrations showed subsurface maxima (tropical Atlantic Ocean -800 m, North Atlantic -500 m). Currents seemed more important in moving POPs to deeper water masses than the biological pump. The ratio of PCB concentrations in near surface waters (excluding PCB-28) between the two sites was inversely correlated with congeners' subcooled liquid vapor pressure, in support of the latitudinal fractionation. The results presented here implied a significant amount of HCB is stored in the Atlantic Ocean (4.8-26% of the global HCB environmental burdens), contrasting traditional beliefs that POPs do not reach the deep ocean.