Air-water Exchange and Phytoplankton Accumulation of Pesistent Organic Pollutants in the Greenland Current and Artic Ocean

Here we show the PCB, HCH and HCB concentrations in air (gas and aerosol phases), water (dissolved and particulate) and Phytoplankton. The results were obtained during the Spanish ATOS-ARTIC Cruise on RV Hespérides during July 2007 in a Transect starting in Iceland and finishing at Svalvard. Our results shows the downslope concentrations of PCBs and HCHs in water and air according to time trends of the last years especially in the case of HCHs. The POP concentrations in phytoplankton were similar than the results previously published for arctic planktonic organisms. The atmospheric halflife estimations (less than 2 days) indicate a decrease in air concentrations when transported northward for HCHs and PCBs. If we study the same phaenomenom for HCB there is no clear tendency in transport showing a lot of variability in the concentrations in air. These trends are consistent with a net absorption of POPs from the atmosphere to water, presumably driven by the high productivity of the region. The close conditions to equilibrium as elucidated from POP fugacities in air and water, suggest a dynamic cycling between the lower atmosphere and surface waters. Bioconcentrations factors for most POPs to Phaeocycties colonies are higher than those predicted from hydrophobicity, even though there is a lack of studies specific to these phytoplankton species, the results suggests that these colonies have a high capacity to uptake POPs and potential mechanisms are reviewed. The present work suggest that phytoplankton plays a ah key role in the biological pump in polar areas. In addition the potential role of ice melting as a source of POPs to water and atmosphere is assessed

Atmospheric occurrence, transport and deposition of polychlorinated biphenyls and hexachlorobenzene in the Mediterranean and Black seas

The Mediterranean and Black seas are unique marine environments subject to important anthropogenic pressures due to direct and indirect loads of atmospheric inputs of organochlorine compounds (OCls) from primary and secondary sources. Here we report the results obtained during two east-west sampling cruises in June 2006 and May 2007 from Barcelona to Istanbul and Alexandria, respectively, where gas-phase and aerosol-phase samples were collected. Both matrices were analyzed for 41 polychlorinated biphenyls (PCBs), including dioxin-like congeners, and hexachlorobenzene (HCB). The values reported in this study for gas-phase HCB and Sigma 41PCB limit of detection (LOD) to 418.3 pg m(-3) and from 81.99 to 931.6 pg m(-3) respectively) are in the same range of those reported in former studies, possibly suggesting a limited decline in their atmospheric concentrations during the last decade for the Mediterranean region due to land-based OCl sources. There is a clear influence of the direction of the air mass on the atmospheric concentrations of PCBs, with higher concentrations when the air mass was from southern Europe, and the lowest concentrations for air masses coming from the SW Mediterranean and Atlantic Ocean. PCBs and HCB are close to air-water equilibrium for most sampling periods, thus resulting in low atmospheric deposition fluxes at open sea. This is consistent with the oligotrophic character of the Mediterranean Sea with a small influence of the biological pump capturing atmospheric PCBs. Therefore, degradation of gas-phase PCBs by OH radicals is estimated to be the main loss process of atmospheric PCBs during their transport over the Mediterranean Sea. Conversely, atmospheric residence times of HCB are predicted to be very long due to a lack of atmospheric degradation and low depositional fluxes due to concentrations at air-water equilibrium

Atmospheric Occurrence and Deposition of Polychlorinated Dibenzo- p -Dioxins and Dibenzofurans (PCDD/Fs) in the Open Mediterranean Sea

International audienceThe overall objective of this work is to provide the firstevaluation of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) occurrence and deposition to Mediterraneanopen seawater. Σ2,3,7,8-PCDD/F air (gas+aerosol) concentrationsover the Mediterranean Sea ranged from 60 to1040fg m-3. The highest value (1555 fg m-3) was measured in areference sample taken in the SW Black Sea. No consistenttrend regarding the diel cycle of PCDD/Fswasobserved.PCDD/Fs transported to the open sea waters from continental areasand across the Atlantic as well as ship emissions may besignificant sources to the open Mediterranean. Seawaterconcentrations in the Mediterranean ranged from 42 to 64 fgL-1. The Σ2,3,7,8-PCDD/F dry deposition fluxes in theMarmara and Black Seas (210 kg year-1) are from 2 to 55times higher than dry fluxes in the Mediterranean Sea (4-156kg year-1). Analysis of estimated diffusive air-water fluxesand air/water fugacity ratios show that a net volatilization ofsome PCDD congeners is feasible. However, evidence of anet absorption flux for the rest of PCDD/F is found. When bothatmospheric deposition processes are considered togetherthe open Mediterranean Sea is a net sink of PCDD/F, due tothe importance of dry deposition fluxes of aerosol-boundPCDDFs

Biodegradation as an important sink of aromatic hydrocarbons in the oceans

Atmospheric deposition of semivolatile aromatic hydrocarbons accounts for an important input of organic matter to the surface ocean. Nevertheless, the biogeochemical cycling and sinks of semivolatile aromatic hydrocarbons in the ocean remain largely uncharacterized. Here we present measurements of 64 polycyclic aromatic hydrocarbons in plankton and seawater from the Atlantic, Pacific, Indian and Southern Oceans, as well an assessment of their microbial degradation genes. Concentrations of the more hydrophobic compounds decreased when the plankton biomass was higher, consistent with the relevance of the biological pump. The mass balance for the global oceans showed that the settling fluxes of aromatic hydrocarbons in the water column were two orders of magnitude lower than the atmospheric deposition fluxes. This imbalance was high for low molecular weight hydrocarbons, such as phenanthrene and methylphenanthrenes, highly abundant in the dissolved phase. Parent polycyclic aromatic hydrocarbons were depleted to a higher degree than alkylated polycyclic aromatic hydrocarbons, and the degradation genes for polycyclic aromatic hydrocarbons were found to be ubiquitous in oceanic metagenomes. These observations point to a key role of biodegradation in depleting the bioavailable dissolved hydrocarbons and to the microbial degradation of atmospheric inputs of organic matter as a relevant process for the marine carbon cycl

Fate of Chiral and Achiral Organochlorine Pesticides in the North Atlantic Bloom Experiment

Organochlorine pesticides (OCPs) were measured in the surface seawater and lower atmosphere during the North Atlantic Bloom Experiment in the spring 2008 from samples collected on the R/V Knorr. The gaseous concentration profiles resulted from both long-range transport (LRT) from the Arctic by polar easterlies and local biogeochemical processes. Relatively constant α/α-hexachlorocyclohexane (HCH) ratios and enantiomer fractions of α-HCH indicated that a single water mass was sampled throughout the cruise. Changes in dissolved phase concentrations were dominated by bloom processes (air-water exchange, partitioning to organic particles, and subsequent sinking) rather than LRT. α-HCH and dissolved phase trans-chlordanes showed depletion of (+) enantiomer, whereas depletion of the (̄) enantiomer was observed for heptachlor exo-epoxide (HEPX) and cis-chlordanes. Fugacity ratio calculations suggest that hexachlorobenzene (HCB) and α-HCH were depositing from air to water whereas heavier OCPs (chlordanes, HEPX) were evaporating. Dissolved phase concentrations did not decrease with time during the three-week bloom period; neither were lipophilic OCPs drawn down from air to water as previous studies hypothesized. Comparison with Arctic measurements suggested that the Arctic returned higher concentrations of α-HCH and HCB through both the atmospheric (polar easterlies) as well as oceanic transport (East Greenland Current) to the lower latitudes. © 2012 American Chemical Society