In this study, perfluoroalkylated substances (PFASs) were analyzed in 92 surface seawater samples taken during the Malaspina 2010 expedition which covered all the tropical and subtropical Atlantic, ...Pacific and Indian oceans. Nine ionic PFASs including C6–C10 perfluoroalkyl carboxylic acids (PFCAs), C4 and C6–C8 perfluoroalkyl sulfonic acids (PFSAs) and two neutral precursors perfluoroalkyl sulfonamides (PFASAs), were identified and quantified. The Atlantic Ocean presented the broader range in concentrations of total PFASs (131–10900 pg/L, median 645 pg/L, n = 45) compared to the other oceanic basins, probably due to a better spatial coverage. Total concentrations in the Pacific ranged from 344 to 2500 pg/L (median = 527 pg/L, n = 27) and in the Indian Ocean from 176 to 1976 pg/L (median = 329, n = 18). Perfluorooctanesulfonic acid (PFOS) was the most abundant compound, accounting for 33% of the total PFASs globally, followed by perfluorodecanoic acid (PFDA, 22%) and perfluorohexanoic acid (PFHxA, 12%), being the rest of the individual congeners under 10% of total PFASs, even for perfluorooctane carboxylic acid (PFOA, 6%). PFASAs accounted for less than 1% of the total PFASs concentration. This study reports the ubiquitous occurrence of PFCAs, PFSAs, and PFASAs in the global ocean, being the first attempt, to our knowledge, to show a comprehensive assessment in surface water samples collected in a single oceanic expedition covering tropical and subtropical oceans. The potential factors affecting their distribution patterns were assessed including the distance to coastal regions, oceanic subtropical gyres, currents and biogeochemical processes. Field evidence of biogeochemical controls on the occurrence of PFASs was tentatively assessed considering environmental variables (solar radiation, temperature, chlorophyll a concentrations among others), and these showed significant correlations with some PFASs, but explaining small to moderate percentages of variability. This suggests that a number of physical and biogeochemical processes collectively drive the oceanic occurrence and fate of PFASs in a complex manner.
Long range atmospheric transport and deposition is a significant introduction pathway of organic pollutants to remote oceanic regions, leading to their subsequent accumulation in marine organisms. ...Persistent organic pollutants (POPs) bioconcentrate in planktonic food webs and these exert a biogeochemical control on the regional and global cycling of POPs. Therefore, an important issue is to determine whether the anthropogenic chemical perturbation of the biosphere introduced by the myriad of organic pollutants present in seawater influences phytoplankton abundance and productivity. The results reported here from five sets of experiments performed in the NE Atlantic Ocean show that there is a toxic effect induced by trace levels of complex mixtures of organic pollutants on phytoplankton oceanic communities. The levels of single pollutant, such as phenanthrene and pyrene, at which lethality of phytoplankton is observed are high in comparison to field levels. Complex mixtures of organic pollutants, however, have an important toxic effect on phytoplankton abundances, viability and concentrations of Chlorophyll
a at pollutant concentrations 20–40 folds those found in the open ocean. The toxicity of these complex mixtures of organic pollutants exceeds by 10
3 times the toxicity expected for a single pollutant. Therefore, our results point out the need for a systematic investigation of the influence of complex mixtures of organic hydrophobic pollutants to oceanic phytoplankton communities, a perturbation not accounted for on previous assessments of anthropogenic pressures in the marine environment.
As much as 400 Tg of carbon from airborne semivolatile aromatic hydrocarbons is deposited to the oceans every year, the largest identified source of anthropogenic organic carbon to the ocean. ...Microbial degradation is a key sink of these pollutants in surface waters, but has received little attention in polar environments. We have challenged Antarctic microbial communities from the sea-surface microlayer (SML) and the subsurface layer (SSL) with polycyclic aromatic hydrocarbons (PAHs) at environmentally relevant concentrations. PAH degradation rates and the microbial responses at both taxonomical and functional levels were assessed. Evidence for faster removal rates was observed in the SML, with rates 2.6-fold higher than in the SSL. In the SML, the highest removal rates were observed for the more hydrophobic and particle-bound PAHs. After 24 h of PAHs exposure, particle-associated bacteria in the SML showed the highest number of significant changes in their composition. These included significant enrichments of several hydrocarbonoclastic bacteria, especially the fast-growing genera
Pseudoalteromonas
, which increased their relative abundances by eightfold. Simultaneous metatranscriptomic analysis showed that the free-living fraction of SML was the most active fraction, especially for members of the order Alteromonadales, which includes
Pseudoalteromonas
. Their key role in PAHs biodegradation in polar environments should be elucidated in further studies. This study highlights the relevant role of bacterial populations inhabiting the sea-surface microlayer, especially the particle-associated habitat, as relevant bioreactors for the removal of aromatic hydrocarbons in the oceans.
Planktonic food webs play an important role driving the environmental fate of persistent organic pollutants, and POP accumulation in phytoplankton has been previously studied for its importance as a ...first step in the aquatic food webs. However, little is known about the accumulation and cycling of organic pollutants between zooplankton and water. The present study shows the results of laboratory experiments on the bioconcentration (by passive uptake) of polycyclic aromatic hydrocarbons in phytoplankton (Rhodomonas salina) and accumulation in copepods (Paracartia(acartia) grani), by ingestion and diffusion. Both bioconcentration (BCF) and bioaccumulation (BAF) factors show significant correlation with the octanol−water partition coefficient (K ow) for phytoplankton and zooplankton. The BCF values for phytoplankton were 2 orders of magnitude higher than those for copepods. The analysis of fecal pellets shows that elimination by defecation is mainly significant for PAHs taken up from ingested phytoplankton but not due to passive uptake. However, the dominant elimination mechanisms are by far metabolism and diffusive depuration. Indeed, the mass balance suggests that metabolism of PAHs by copepods is a significant process that could play a role in the fate of PAHs in the water column. Uptake, depuration, eggestion, and ingestion rates increased with hydrophobicity of the chemical, while the metabolism rate was slightly higher for the less hydrophobic compounds. Passive partitioning dominated the accumulation of POPs in zooplankton. The derivation of all the uptake and loss rate constants for PAHs opens the door to future modeling studies of the role of zooplankton in PAH cycling in the marine environment.
Persistent Organic Pollutants (POPs) are toxic, bioaccumulable and semi‐volatile compounds that have been detected in all environmental compartments, even in remote pristine regions where they have ...never been produced or used. Long range atmospheric transport (LRAT) and subsequent deposition is the major route of introduction of POPs to the oceans, including remote regions, and thus to the marine food‐webs. It has been suggested that when POPs travel through the atmosphere, they tend to move in stages. This is known as the grasshopper effect, a repeated process of volatilization and deposition, even though the measure of grasshopping potential has been elusive. Here we show the spatial and seasonal variability of the grasshopper and LRAT potentials for polychlorinated biphenyls (PCB), a significant class of POPs. The number of hops that a chemical undergoes during LRAT over the oceans presents an important spatial and seasonal variability driven by biogeochemical processes occurring in the water column. These results have important implications for the understanding of the widespread distribution and fractionation processes of POPs at the global scale, showing that transport events to remote regions, such the Arctic, are maximized during seasons of low primary productivity.
The composition of bacteria inhabiting the sea-surface microlayer (SML) is poorly characterized globally and yet undescribed for the Southern Ocean, despite their relevance for the biogeochemistry of ...the surface ocean. We report the abundances and diversity of bacteria inhabiting the SML and the subsurface waters (SSL) determined from a unique sample set from a polar coastal ecosystem (Livingston Island, Antarctica). From early to late austral summer (January–March 2018), we consistently found a higher abundance of bacteria in the SML than in the SSL. The SML was enriched in some Gammaproteobacteria genus such as
Pseudoalteromonas
,
Pseudomonas
, and
Colwellia
, known to degrade a wide range of semivolatile, hydrophobic, and surfactant-like organic pollutants. Hydrocarbons and other synthetic chemicals including surfactants, such as perfluoroalkyl substances (PFAS), reach remote marine environments by atmospheric transport and deposition and by oceanic currents, and are known to accumulate in the SML. Relative abundances of specific SML-enriched bacterial groups were significantly correlated to concentrations of PFASs, taken as a proxy of hydrophobic anthropogenic pollutants present in the SML and its stability. Our observations provide evidence for an important pollutant-bacteria interaction in the marine SML. Given that pollutant emissions have increased during the Anthropocene, our results point to the need to assess chemical pollution as a factor modulating marine microbiomes in the contemporaneous and future oceans.
The Mediterranean and Black Seas are unique marine environments subject to important anthropogenic pressures due to atmospheric and riverine inputs of organic pollutants. They include regions of ...different physical and trophic characteristics, which allow the studying of the controls on pollutant occurrence and fate under different conditions in terms of particles, plankton biomass, interactions with the atmosphere, biodegradation, and their dependence on the pollutant physical chemical properties. Polycyclic Aromatic Hydrocarbons (PAHs) have been measured in samples of seawater (dissolved and particulate phases) and plankton during two east‐west sampling cruises in June 2006 and May 2007. The concentrations of dissolved PAHs were higher in the south‐western Black Sea and Eastern Mediterranean than in the Western Mediterranean, reflecting different pollutant loads, trophic conditions and cycling. Particle and plankton phase PAH concentrations were higher when lower concentrations of suspended particles and biomass occurred, with apparent differences due to the PAH physical chemical properties. The surface PAH particle phase concentrations decreased when the total suspended particles (TSP) increased for the higher molecular weight (MW) compounds, consistent with controls due to particle settling depletion of water column compounds and dilution. Conversely, PAH concentrations in plankton decreased at higher biomass only for the low MW PAHs, suggesting that biodegradative processes in the water column are a major driver of their occurrence in the photic zone. The results presented here are the most extensive data set available for the Mediterranean Sea and provide clear evidence of the important physical and biological controls on PAH occurrence and cycling in oceanic regions.
Key Points
PAHs were measured in samples of seawater and plankton of two east‐west cruises
The results evidence biogeochemical controls on PAH cycling in oceanic regions
Soils are the main reservoir of persistent organic pollutants (POPs) and thus air−soil exchange and partitioning are key processes controlling the fate and transport of POPs at regional and global ...scales. To date, soil fugacity has been estimated from models of the soil−air partition coefficients, with the associated unavoidable uncertainties; or by experimental procedures in the laboratory with uncertain application in field conditions. The development of an operational soil fugacity sampler is presented here; one which ensures optimal field data of the POP fugacity in soil and environmentally relevant surface (soil+grass, etc.) and therefore ensuring accurate soil−air partition coefficients and surface−air fugacity gradients. The sampler flow rate is optimized, sampler reproducibility is assessed, and equilibrium between the gas and soil concentrations of polychlorinated biphenyls and polycyclic aromatic hydrocarbons is demonstrated. The development and comprehensive validation of a soil fugacity sampler opens the door for the first time to field studies that accurately determine the variables driving the soil−air partitioning and fluxes of POPs.
Sulfate is an important component of global atmospheric aerosol, and has partially compensated for greenhouse gas-induced warming during the industrial period. The magnitude of direct and indirect ...radiative forcing of aerosols since preindustrial times is a large uncertainty in climate models, which has been attributed largely to uncertainties in the preindustrial environment. Here, we report observations of the oxygen isotopic composition (Δ17O) of sulfate aerosol collected in the remote marine boundary layer (MBL) in spring and summer in order to evaluate sulfate production mechanisms in pristine-like environments. Model-aided analysis of the observations suggests that 33–50 % of sulfate in the MBL is formed via oxidation by hypohalous acids (HOX = HOBr + HOCl), a production mechanism typically excluded in large-scale models due to uncertainties in the reaction rates, which are due mainly to uncertainties in reactive halogen concentrations. Based on the estimated fraction of sulfate formed via HOX oxidation, we further estimate that daily-averaged HOX mixing ratios on the order of 0.01–0.1 parts per trillion (ppt = pmol/mol) in the remote MBL during spring and summer are sufficient to explain the observations.
This work describes the assessment of a selection of fullerenes including C60 and C70 fullerene, N-methylfulleropyrrolidine, C60 pyrrolidine tris-acid ethyl ester, 6,6-Phenyl-C61 butyric acid butyl ...ester and 6,6-Thienyl C61 butyric acid methyl ester, in airborne particulate from the Mediterranean Sea collected during two sampling campaigns from Barcelona to Istanbul and Alexandria, respectively. The analysis of the samples was carried out using a new method based on liquid chromatography coupled to mass spectrometry (LC-MS) presenting sensitivities between 5.4 and 20.9 pg/m3. A total number of 43 samples covering the different basins of Mediterranean Sea were analyzed. Fullerenes were detected in all analyzed samples and quantifiable concentrations were found in 28 of the analyzed samples. The median of C60 and C70 fullerenes aerosol phase concentrations were 0.06 ng/m3 and 0.48 ng/m3 respectively for the Mediterranean Sea atmosphere. C70 fullerene was the most frequently detected compound and also it was found in the higher concentrations for most samples, reaching 233.8 ng/m3. The modeled back-trajectories disclose that those samples with higher concentrations of fullerenes were related to air masses which had been circulating over regions with an intense industrial activity, but the variability of the C70/C60 ratio suggests multiple different sources. These results are related to the incidental emissions from urban and industrial development, underpinning the need of studying the possible risks associated to carbon nanoparticles in the environment and the need of evaluating the possible consequences of their ubiquitous occurrence.
PDF
