Climatic and Biogeochemical Controls on the Remobilization and Reservoirs of Persistent Organic Pollutants in Antarctica

After decades of primary emissions, reservoirs of persistent organic pollutants (POPs) have accumulated in soils and snow/ice in polar regions. These reservoirs can be remobilized due to decreasing primary emissions or due to climate change-driven warmer conditions. Results from a sampling campaign carried out at Livingston Island (Antarctica) focusing on field measurements of air–soil exchange of POPs show that there is a close coupling of the polychlorinated biphenyls (PCBs) in the atmosphere and snow/ice and soils with a status close to air–surface equilibrium to a net volatilization from Antarctic reservoirs. This remobilization of PCBs is driven by changes in temperature and soil organic matter (SOM) content, and it provides strong evidence that the current and future remobilization and sinks of POPs are a strong function of the close coupling of climate change and carbon cycling in the Antarctic region and this is not only due to warming. Whereas an increase of 1 °C in ambient temperature due to climate change would increase current Antarctic atmospheric inventories of PCBs by 21–45%, a concurrent increase of 0.5% SOM would counteract the influence of warming by reducing the POP fugacity in soil. A 1 °C increase in Antarctic temperatures will induce an increase of the soil–vegetation organic carbon and associated POPs pools by 25%, becoming a net sink of POPs, and trapping up to 70 times more POPs than the amount remobilized to the atmosphere. Therefore, changes in soil biogeochemistry driven by perturbations of climate may increase to a larger degree the soil fugacity capacity than the decrease in air and soil fugacity capacity due to higher temperatures. Future research should focus on quantifying these remobilization fluxes and sinks for the Antarctic region

Organophosphate Ester (OPE) Flame Retardants and Plasticizers in the Open Mediterranean and Black Seas Atmosphere

The presence of organophosphate ester (OPE) flame retardants and plasticizers has been confirmed for the first time in the atmosphere over the Mediterranean and Black Seas. Atmospheric aerosol samples were collected during two West–East oceanographic cruises across the Mediterranean and in the southwest Black Sea. This comprehensive assessment of baseline concentrations of aerosol phase OPEs, spatial distribution, and related deposition fluxes reveals levels ranging from 0.4 to 6.0 ng m^–3 for the ∑₁₄OPEs and a lack of significant differences among sub-basins. Levels measured across the Mediterranean Sea and in the Black Sea are in the upper range or higher than those from previous reports for the marine atmosphere, presumably due to proximity to sources. From 13 to 260 tons of OPEs are estimated to be annually loaded to the Mediterranean Sea open waters from the atmosphere. Tris-(1-chloro-2-propyl)­phosphate (TCPP) was the most abundant compound over the atmosphere of all the Mediterranean and Black Sea sub-basins, and therefore the chemical reaching surface waters at a higher extent by dry deposition. The atmospheric deposition fluxes of phosphorus due to OPE deposition is a significant fraction of known atmospheric inputs of new organic phosphorus (P), suggesting the relevant role that anthropogenic organic pollutants could play in the P cycle

The “Degradative” and “Biological” Pumps Controls on the Atmospheric Deposition and Sequestration of Hexachlorocyclohexanes and Hexachlorobenzene in the North Atlantic and Arctic Oceans

The cycling of hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCHs) has been studied in the North Atlantic and Arctic Ocean. Concentrations of HCHs and HCB were measured simultaneously in the atmosphere (gas and aerosol phases), seawater (dissolved and particulate phases), and phytoplankton. The atmospheric concentrations of HCHs decrease during transport over the Greenland Current with estimated e-folding times of 1.6 days, a trend not observed for HCB. This strong decrease in atmospheric concentrations of HCH is consistent with the estimated atmospheric depositional fluxes driven by the air–water disequilibrium. The removal of HCHs from the surface ocean by the degradative pump due to hydrolysis and microbial degradation and by the biological pump due to settling of particle-associated HCHs are estimated; the removal fluxes are within a factor of 2 of the atmospheric inputs for most sampling events, suggesting an important role of the degradative pump in the overall oceanic sink of HCHs. Conversely, the lack of degradation of HCB in surface waters and its relatively low hydrophobicity imply a lack of effective removal processes, consistent with the observed air and water concentrations close to equilibrium. This work is the first that estimates the relative importance of the biological and degradative pumps on the atmospheric deposition of the less persistent organic pollutants and points out the need for further research for quantifying the magnitude of degradative processes in the environment

Influence of Organic Matter Content and Human Activities on the Occurrence of Organic Pollutants in Antarctic Soils, Lichens, Grass, and Mosses

Banned pesticides such as HCB and <i>p</i>,<i>p</i>′-DDE, and other legacy and ongoing pollutants such as PCBs and PAHs, were measured in different vegetation types and soil samples collected at selected areas from Antarctic Peninsula (Deception and Livingstone Islands, Southern Shetlands). Two Antarctic expeditions (in 2005 and 2009) were carried out to assess POPs levels at remote areas, and close to current and abandoned Antarctic research settlements, to assess potential sources of pollutants. Overall, the patterns in lichens, mosses, and grass were dominated by low molecular PCB congeners and PAHs and the presence of HCB and <i>p</i>,<i>p</i>′-DDE rather than heavier compounds, suggesting the importance of long-range atmospheric transport of POPs as the main vector for the introduction of these chemicals to Antarctica. Statistically significant correlations (<i>p</i>-level < 0.05) between concentrations in vegetation of PCBs, <i>p</i>,<i>p</i>′-DDE, and the more volatile PAHs with lipid content were found with <i>r</i>² of 0.22–0.52 for PCBs, 0.42 for <i>p</i>,<i>p</i>′-DDE, and 0.44–0.72 for the more volatile PAHs. Thus, lipid content is an important factor controlling POPs in Antarctic lichens, mosses, and grass. A strong significant dependence of HCB (<i>r</i>² = 0.83), <i>p</i>,<i>p</i>′-DDE (<i>r</i>² = 0.60), and PCBs (<i>r</i>² = 0.36–0.47) concentrations in soil on its organic carbon content was also observed, indicating the important role of soil organic matter (SOM) in the retention of PCBs and OCPs in Polar Regions, where SOM content is low. Penguin colonies enhance the SOM content in some areas which is reflected in higher concentrations of all POPs, especially of persistent compounds such as <i>p</i>,<i>p</i>′-DDE. Higher concentrations of PCBs and PAHs found at the currently active Byers Camp (in an Antarctic Specially Protected Area) were explained by higher SOM content, thus indicating that Antarctic regulations are being successfully fulfilled in this small research area. On the other hand, PAHs in soils proximate to current Juan Carlos I research station show that even small human settlements are an important source of PAHs to the local environment. Therefore, even though the concentrations in Antarctica are low, there is evidence of local hotspots of contamination

Agents de coneixement i expertesa tecnològica : grups TECNIO UdG

Presentació a càrrec de Marc Sabater, Sebastià Puig i Joseta Roca del grup TECNIO de la Universitat de Giron

Unexpected Occurrence of Volatile Dimethylsiloxanes in Antarctic Soils, Vegetation, Phytoplankton, and Krill

Volatile methyl siloxanes (VMS) are high-production synthetic compounds, ubiquitously found in the environment of source regions. Here, we show for the first time the occurrence of VMS in soils, vegetation, phytoplankton, and krill samples from the Antarctic Peninsula region, which questions previous claims that these compounds are “flyers” and do not significantly reach remote ecosystems. Cyclic VMS are the predominant compounds, with concentrations ranging from the limits of detection to 110 ng/g in soils. Concentrations of cyclic VMS in phytoplankton are negatively correlated with sea surface salinity, indicating a source from ice and snow melting and consistent with snow depositional inputs. After the summer snow melting, VMS accumulate in the Southern Ocean and Antarctic biota. Therefore, once introduced into the marine environment, VMS are eventually trapped by the biological pump and, thus, behave as “single hoppers”. Conversely, VMS in soils and vegetation behave as “multiple hoppers” due to their high volatility

Background Concentrations of Polychlorinated Dibenzo‑<i>p</i>‑Dioxins, Dibenzofurans, and Biphenyls in the Global Oceanic Atmosphere

The remote oceans are among the most pristine environments in the world, away from sources of anthropogenic persistent organic pollutants (POP), but nevertheless recipients of atmospheric deposition of POPs that have undergone long-range atmospheric transport (LRAT). In this work, the background occurrence of gas and aerosol phase polychlorinated dibenzo-<i>p</i>-dioxins and dibenzofurans (PCDD/Fs) and dioxin like polychlorinated biphenyls (dl-PCB) is evaluated for the first time in the atmosphere of the tropical and subtropical Atlantic, Pacific, and Indian oceans. Thirty-nine air samples were collected during the eight-month Malaspina circumnavigation cruise onboard the R/V <i>Hespérides.</i> The background levels of dioxins and dl-PCBs remained very low and in many cases very close to or below the limit of detection. Expectedly, the levels of PCBs were higher than dioxins, PCB#118 being the most abundant compound. In the particular case of dioxins, octachlorodibenzo-<i>p</i>-dioxin (OCDD) was the most abundant PCDD/F congener. Distribution of dl-PCB is dominated by the gas phase, while for PCDD/F the aerosol phase concentrations were higher, particularly for the more hydrophobic congeners. The Atlantic Ocean presented on average the highest PCDD/F and dl-PCB concentrations, being lower in the southern hemisphere. The assessment of air mass back trajectories show a clear influence of continental source regions, and lower concentrations when the air mass has an oceanic origin. In addition, the samples affected by an oceanic air mass are characterized by a lower contribution of the less chlorinated dioxins in comparison with the furans, consistent with the reported higher reaction rate constants of dibenzo-<i>p</i>-dioxins with OH radicals than those of dibenzofurans. The total dry atmospheric deposition of aerosol-bound ∑PCDD/F and ∑dl-PCB to the global oceans was estimated to be 354 and 896 kg/year, respectively

Field Measurements of the Atmospheric Dry Deposition Fluxes and Velocities of Polycyclic Aromatic Hydrocarbons to the Global Oceans

The atmospheric dry deposition fluxes of 16 polycyclic aromatic hydrocarbons (PAHs) have been measured, for the first time, in the tropical and subtropical Atlantic, Pacific, and Indian Oceans. Depositional fluxes for fine (0.7–2.7 μm) and coarse (>2.7 μm) aerosol fractions were simultaneously determined with the suspended aerosol phase concentrations, allowing the determination of PAH deposition velocities (<i>v</i>_D). PAH dry deposition fluxes (<i>F</i>_DD) bound to coarse aerosols were higher than those of fine aerosols for 83% of the measurements. Average <i>F</i>_DD for total (fine + coarse) Σ₁₆PAHs (sum of 16 individual PAHs) ranged from 8.33 ng m^–2d^–1 to 52.38 ng m^–2d^–1. Mean <i>F</i>_DD for coarse aerosol’s individual PAHs ranged between 0.13 ng m^–2d^–1 (Perylene) and 1.96 ng m^–2d^–1 (Methyl Pyrene), and for the fine aerosol fraction these ranged between 0.06 ng m^–2d^–1 (Dimethyl Pyrene) and 1.25 ng m^–2d^–1 (Methyl Chrysene). The estimated deposition velocities went from the highest mean <i>v</i>_D for Methyl Chrysene (0.17–13.30 cm s^–1), followed by Dibenzo­(ah)­Anthracene (0.29–1.38 cm s^–1), and other high MW PAHs to minimum values of <i>v</i>_D for Dimethyl Pyrene (<0.04 cm s^–1) and Pyrene (<0.06 cm s^–1). Dry depositional processes depend on the concentration of PAHs in the suspended aerosol, but also on physicochemical properties and environmental variables (vapor pressure, wind speed, and on the affinity of aerosols for depositing to the sea surface). Empirical parametrizations are proposed to predict the dry depositional velocities of semivolatile organic compounds to the global oceans

Role of Snow Deposition of Perfluoroalkylated Substances at Coastal Livingston Island (Maritime Antarctica)

Perfluoroalkyl substances (PFAS) are ubiquitous in the environment, including remote polar regions. To evaluate the role of snow deposition as an input of PFAS to Maritime Antarctica, fresh snow deposition, surface snow, streams from melted snow, coastal seawater, and plankton samples were collected over a three-month period (December 2014–February 2015) at Livingston Island. Local sources of PFASs were significant for perfluoroalkyl sulfonates (PFSAs) and C7–14 perfluoroalkyl carboxylates (PFCAs) in snow but limited to the transited areas of the research station. The concentrations of 14 ionizable PFAS (∑PFAS) in freshly deposited snow (760–3600 pg L^–1) were 1 order of magnitude higher than those in background surface snow (82–430 pg L^–1). ∑PFAS ranged from 94 to 420 pg L^–1 in seawater and from 3.1 to 16 ng g_dw^–1 in plankton. Ratios of individual PFAS concentrations in freshly deposited snow relative to surface snow (<i>C</i>_SD/<i>C</i>_Snow), snowmelt (<i>C</i>_SD/<i>C</i>_SM), and seawater (<i>C</i>_SD/<i>C</i>_SW) were close to 1 (from 0.44 to 1.4) for all perfluorooctanesulfonate (PFOS) isomers, suggesting that snowfall does not contribute significantly to PFOS in seawater. Conversely, these ratios for PFCAs ranged from 1 to 33 and were positively correlated with the number of carbons in the PFCA alkylated chain. These trends suggest that snow deposition, scavenging sea-salt aerosol bound PFAS, plays a role as a significant input of PFCAs to the Maritime Antarctica

Clade-Specific Quantitative Analysis of Photosynthetic Gene Expression in <i>Prochlorococcus</i>

<div><p>Newly designed primers targeting <i>rbc</i>L (CO₂ fixation), <i>psb</i>A (photosystem II) and <i>rnp</i>B (reference) genes were used in qRT-PCR assays to assess the photosynthetic capability of natural communities of <i>Prochlorococcus</i>, the most abundant photosynthetic organism on Earth and a major contributor to primary production in oligotrophic oceans. After optimizing sample collection methodology, we analyzed a total of 62 stations from the Malaspina 2010 circumnavigation (including Atlantic, Pacific and Indian Oceans) at three different depths. Sequence and quantitative analyses of the corresponding amplicons showed the presence of high-light (HL) and low-light (LL) <i>Prochlorococcus</i> clades in essentially all 182 samples, with a largely uniform stratification of LL and HL sequences. <i>Synechococcus</i> cross-amplifications were detected by the taxon-specific melting temperatures of the amplicons. Laboratory exposure of <i>Prochlorococcus</i> MED4 (HL) and MIT9313 (LL) strains to organic pollutants (PAHs and organochlorine compounds) showed a decrease of <i>rbc</i>L transcript abundances, and of the <i>rbc</i>L to <i>psb</i>A ratios for both strains. We propose this technique as a convenient assay to evaluate effects of environmental stressors, including pollution, on the oceanic <i>Prochlorococcus</i> photosynthetic function.</p></div