Occurrence of emerging contaminants in three river basins impacted by wastewater treatment plant effluents: Spatio-seasonal patterns and environmental risk assessment.

The concern on the fate and distribution of contaminants of emerging concern (CECs) is a burning topic due to their widespread occurrence and potential harmful effects. Particularly, antibiotics have received great attention due to their implications in antimicrobial resistance occurrence. The impact of wastewater treatment plants (WWTP) is remarkable, being one of the main pathways for the introduction of CECs into aquatic systems. The combination of novel analytical methodologies and risk assessment strategies is a promising tool to find out environmentally relevant compounds posing major concerns in freshwater ecosystems impacted by those wastewater effluents. Within this context, a multi-target approach was applied in three Spanish river basins affected by different WWTP treated effluents for spatio-temporal monitoring of their chemical status. Solid phase extraction followed by ultra-high-performance liquid chromatography were used for the quantification of a large panel of compounds (n = 270), including pharmaceuticals and other consumer products, pesticides and industrial chemicals. To this end, water samples were collected in four sampling campaigns at three locations in each basin: (i) upstream from the WWTPs; (ii) WWTP effluent discharge points (effluent outfall); and (iii) downstream from the WWTPs (500 m downriver from the effluent outfall). Likewise, 24-h composite effluent samples from each of the WWTPs were provided in all sampling periods. First the occurrence and distribution of these compounds were assessed. Diverse seasonal trends were observed depending on the group of emerging compounds, though COVID-19 outbreak affected variations of certain pharmaceuticals. Detection frequencies and concentrations in effluents generally exceeded those in river samples and concentrations measured upstream WWTPs were generally low or non-quantifiable. Finally, risks associated with maximum contamination levels were evaluated using two different approaches to account for antibiotic resistance selection as well. From all studied compounds, 89 evidenced environmental risk on at least one occasion in this study.

High microbiome and metabolome diversification in coexisting sponges with different bio-ecological traits.

Marine Porifera host diverse microbial communities, which influence host metabolism and fitness. However, functional relationships between sponge microbiomes and metabolic signatures are poorly understood. We integrate microbiome characterization, metabolomics and microbial predicted functions of four coexisting Mediterranean sponges -Petrosia ficiformis, Chondrosia reniformis, Crambe crambe and Chondrilla nucula. Microscopy observations reveal anatomical differences in microbial densities. Microbiomes exhibit strong species-specific trends. C. crambe shares many rare amplicon sequence variants (ASV) with the surrounding seawater. This suggests important inputs of microbial diversity acquired by selective horizontal acquisition. Phylum Cyanobacteria is mainly represented in C. nucula and C. crambe. According to putative functions, the microbiome of P. ficiformis and C. reniformis are functionally heterotrophic, while C. crambe and C. nucula are autotrophic. The four species display distinct metabolic profiles at single compound level. However, at molecular class level they share a "core metabolome". Concurrently, we find global microbiome-metabolome association when considering all four sponge species. Within each species still, sets of microbe/metabolites are identified driving multi-omics congruence. Our findings suggest that diverse microbial players and metabolic profiles may promote niche diversification, but also, analogous phenotypic patterns of "symbiont evolutionary convergence" in sponge assemblages where holobionts co-exist in the same area.

Optimization for the analysis of 42 per- and polyfluorinated substances in human plasma: A high-throughput method for epidemiological studies.

There is an increasing awareness about the presence of per- and polyfluoroalkyl substances (PFAS) in many environmental and biological compartments, including human biofluids and tissues. However, the increase of PFAS replacements, including alternatives with shorter chain or less bioaccumulative potential, has broaden the exposure and the need for wider identification procedures. Moreover, the low volumes available for human blood or plasma, and the high number of samples needed to assess adequately epidemiologic studies, require particularly fast, reproducible and, if possible, miniaturized protocols. Therefore, accurate and robust analytical methods are still needed to quantify the PFAS's burden in humans and to understand potential health risks. In this study, we have developed and validated the analysis of 42 PFAS in human plasma by means of a Captiva 96-well micro extraction plate and a LC-q-Orbitrap. For the optimization of the analytical workflow, three extraction/clean-up methods were tested, and the selected one was validated using spiked artificial and bovine plasma at four concentration levels. The final method showed high absolute recoveries for the 42 PFAS, ranging from 52% to 130%, instrumental detection limits between 0.001-0.6 ng mL-1, overall good precision (CV < 20% for most of the PFAS) and a low uncertainty (< 30% of relative expanded deviation, k = 2). The method was further validated both with the NIST plasma Standard Reference Material 1950, showing that the accuracy of the provided results was between 63%-101%, and by the proficiency test arranged by the Arctic Monitoring Assessment Program (AMAP, 2022) obtaining satisfactory results within 95% confidence interval of the assigned value.

Suspect Screening of Chemicals in Hospital Wastewaters Using Effect-Directed Analysis Approach as Prioritization Strategy.

The increasing number of contaminants in the environment has pushed water monitoring programs to find out the most hazardous known and unknown chemicals in the environment. Sample treatment-simplification methods and non-target screening approaches can help researchers to not overlook potential chemicals present in complex aqueous samples. In this work, an effect-directed analysis (EDA) protocol using the sea urchin embryo test (SET) as a toxicological in vivo bioassay was used as simplified strategy to identify potential unknown chemicals present in a very complex aqueous matrix such as hospital effluent. The SET bioassay was used for the first time here to evaluate potential toxic fractions in hospital effluent, which were obtained after a two-step fractionation using C18 and aminopropyl chromatographic semi-preparative columns. The unknown compounds present in the toxic fractions were identified by means of liquid chromatography coupled to a Q Exactive Orbitrap high-resolution mass spectrometer (LC-HRMS) and using a suspect analysis approach. The results were complemented by gas chromatography-mass spectrometry analysis (GC-MS) in order to identify the widest range of chemical compounds present in the sample and the toxic fractions. Using EDA as sample treatment simplification method, the number of unknown chemicals (>446 features) detected in the raw sample was narrowed down to 94 potential toxic candidates identified in the significantly toxic fractions. Among them, the presence of 25 compounds was confirmed with available chemical standards including 14 pharmaceuticals, a personal care product, six pesticides and four industrial products. The observations found in this work emphasize the difficulties in identifying potential toxicity drivers in complex water samples, as in the case of hospital wastewater.

Spatio-seasonal patterns of the impact of wastewater treatment plant effluents on antibiotic resistance in river sediments.

There is a growing concern about the risk of antibiotic resistance emergence and dissemination in the environment. Here, we evaluated the spatio-seasonal patterns of the impact of wastewater treatment plant (WWTP) effluents on antibiotic resistance in river sediments. To this purpose, sediment samples were collected in three river basins affected by WWTP effluents in wet (high-water period) and dry (low-water period) hydrological conditions at three locations: (i) upstream the WWTPs; (ii) WWTP effluent discharge points (effluent outfall); and (iii) downstream the WWTPs (500 m downriver from the effluent outfall). The absolute and relative abundances of 9 antibiotic resistance genes (ARGs), 3 mobile genetic element (MGE) genes, and 4 metal resistance genes (MRGs) were quantified in sediment samples, as well as a variety of physicochemical parameters, metal contents, and antibiotic concentrations in both sediment and water samples. In sediments, significantly higher relative abundances of most genes were observed in downstream vs. upstream sampling points. Seasonal changes (higher values in low-water vs. high-water period) were observed for both ARG absolute and relative abundances in sediment samples. Chemical data revealed the contribution of effluents from WWTPs as a source of antibiotic and metal contamination in river ecosystems. The observed positive correlations between ARG and MGE genes relative abundances point out to the role of horizontal gene transfer in antibiotic resistance dissemination. Monitoring plans that take into consideration spatio-temporal patterns must be implemented to properly assess the environmental fate of WWTP-related emerging contaminants in river ecosystems.

Effect-directed analysis of a hospital effluent sample using A-YES for the identification of endocrine disrupting compounds.

An effect-directed analysis (EDA) approach was used to identify the compounds responsible for endocrine disruption in a hospital effluent (Basque Country). In order to facilitate the identification of the potentially toxic substances, a sample was collected using an automated onsite large volume solid phase extraction (LV-SPE) system. Then, it was fractionated with a two-step orthogonal chromatographic separation and tested for estrogenic effects with a recombinant yeast (A-YES) in-vitro bioassay. The fractionation method was optimized and validated for 184 compounds, and its application to the hospital effluent sample allowed reducing the number of unknowns from 292 in the raw sample to 35 after suspect analysis of the bioactive fractions. Among those, 7 of them were confirmed with chemical standards. In addition, target analysis of the raw sample confirmed the presence of mestranol, estrone and dodemorph in the fractions showing estrogenic activity. Predictive estrogenic activity modelling using quantitative structure-activity relationships indicated that the hormones mestranol (5840 ng/L) and estrone (128 ng/L), the plasticiser bisphenol A (9219 ng/L) and the preservative butylparaben (1224 ng/L) were the main contributors of the potential toxicity. Derived bioanalytical equivalents (BEQs) pointed mestranol and estrone as the main contributors (56 % and 43 %, respectively) of the 50 % of the sample's explained total estrogenic activity.

Effects of aquaculture waste feeds and antibiotics on marine benthic ecosystems in the Mediterranean Sea.

Intensive aquaculture is an important source of organic waste and antibiotics into the marine environment. Yet, their impacts on benthic marine ecosystems are poorly understood. Here, we investigated the ecological impacts of fish feed waste alone and in combination with three different antibiotics (i.e., oxytetracycline, florfenicol and flumequine) in benthic ecosystems of the Mediterranean Sea by performing a field experiment. We assessed the fate of the antibiotics in the sediment and their accumulation in wild fauna after two weeks of exposure. Moreover, we investigated the impact of the feed waste alone and in combination with the antibiotics on sediment physico-chemical properties, on benthic invertebrates, as well as on the microbiota and resistome of the sampled sediments. One week after the last antibiotic application, average oxytetracycline and flumequine concentrations in the sediment were <1% and 15% of the applied dose, respectively, while florfenicol was not detected. Flumequine concentrations in wild invertebrates reached 3 µg g-1, while concentrations of oxytetracycline were about an order of magnitude lower, and florfenicol was not detected. Feed waste, with and without antibiotics, increased the concentration of fine particulate matter, affected the pH and redox conditions, and significantly reduced the biodiversity and abundance of benthic invertebrates. Feed waste also had a significant influence on the structure of sediment microbial communities, while specific effects related to the different antibiotics ranged from insignificant to mild. The presence of antibiotics significantly influenced the normalized abundance of the measured antibiotic resistance genes. Florfenicol and oxytetracycline contributed to an increase of genes conferring resistance to macrolides, tetracyclines, aminoglycosides and chloramphenicol, while flumequine had a less clear impact on the sediment resistome. This study demonstrates that feed waste from aquaculture farms can rapidly alter the habitat and biodiversity of Mediterranean benthic ecosystems, while antibiotic residual concentrations can contribute to the enrichment of bacterial genes resistant to antibiotic classes that are of high relevance for human medicine.

Gametogenesis-Related Fluctuations in Ovothiol Levels in the Mantle of Mussels from Different Estuaries: Fighting Oxidative Stress for Spawning in Polluted Waters.

Reactive oxygen species present a challenge for marine organisms releasing gametes into the water. Thiol-containing molecules protect cells against oxidative stress, and ovothiol (OSH), an antioxidant-reducing mercaptohistidine, has been described as especially relevant in the oocytes of marine invertebrates. Ovothiol synthase (ovoA), in charge of the first step in OSH synthesis, was sequenced in mussels, Mytilus galloprovincialis. Transcription levels of ovoA in mantle did not significantly change along the reproductive cycle. No alterations of ovoA transcription were observed after a laboratory copper (10 µg/L) exposure or in mussels captured in a highly polluted site. Conversely, the metabolomic analysis of the hydrophilic metabolite content in mantle clearly classified mussels according to their site of origin, especially at the most advanced stages of oogenesis. Quantification of OSH-A and -B and glutathione (GSH), revealed stable levels in mantle at early gametogenesis in the unpolluted sampling site, but a strong increase in female mantle previous to spawning in the polluted site. These increased concentrations under pollution suggest that OSH-A accumulates along oogenesis, independent of gene transcription regulation. The concerted accumulation of OSH-A and GSH suggests the building of a balanced cellular redox-system to scavenge ROS produced in the oocyte before and during fertilization.

Vertical transport and sinks of perfluoroalkyl substances in the global open ocean.

The ubiquitous occurrence of perfluoroalkyl substances (PFAS) in the open ocean has been previously documented, but their vertical transport and oceanic sinks have not been comprehensively characterized and quantified at the oceanic scale. During the Malaspina 2010 circumnavigation expedition, 21 PFAS were measured at the surface and at the deep chlorophyll maximum (DCM) in the Atlantic, Indian and Pacific oceans. In this work, we report an extended data set of PFAS dissolved phase concentrations at the DCM. ∑PFAS at the DCM varied from 130 to 11 000 pg L-1, with a global average value of 500 pg L-1. Perfluorooctanesulfonate (PFOS) abundance contributed 39% of ∑PFAS, followed by perfluorodecanoate (PFDA, 17%), and perfluorohexanoate (PFHxA, 12%). The relative contribution of the remaining compounds was below 10%, with perfluorooctanoate (PFOA) contributing only 5% to PFAS measured at the DCM. Estimates of vertical diffusivity, derived from microstructure turbulence observations in the upper (<300 m) water column, allowed the derivation of PFAS eddy diffusive fluxes from concurrent field measurements of eddy diffusivity and PFAS concentrations. The PFAS concentrations at the DCM predicted from an eddy diffusivity model were lower than field-measured concentrations, suggesting a relevant role of other vertical transport mechanisms. Settling fluxes of organic matter bound PFAS (biological pump), oceanic circulation and potential, yet un-reported, biological transformations are discussed.

An optimized sample treatment method for the determination of antibiotics in seawater, marine sediments and biological samples using LC-TOF/MS.

Antibiotics used in marine aquaculture have been reported to accumulate in sediments and non-target aquatic organisms, modifying the biodiversity and the environmental conditions in areas close to the fish farms. Improved analytical methods are required to assess the spread and the impacts of aquaculture antibiotics in the marine environment, as well as to estimate resistance development risks. In this study, we have optimized a method for simultaneous quantitative determination of oxytetracycline, florfenicol and flumequine in marine samples using liquid chromatography coupled to time-of-flight high resolution mass spectrometry (LC-TOF/MS). The method optimization was carried out for seawater, sediment and biological samples (biofilm and two benthic invertebrate species: Gammarus aequicauda and Monodonta articulata). Special attention was paid to the optimization of the extraction and purification steps, testing: liquid-liquid and solid-liquid extractions, the use of silica and other commercial sorbents' clean-up, and single and tandem solid phase extraction procedures. The limits of quantification (MQLs) achieved with the developed method are 0.1-0.5 µg L-1 in seawater; 1-5 µg kg-1 in marine sediments; 5-25 µg kg-1 in biofilm; and 100-500 µg kg-1 in invertebrates, with good accuracy and precision. Method recoveries in spiked samples are 65-120% in seawater and sediment samples, and 63-110% in the biological samples. The method has been successfully implemented for the determination of antibiotic concentrations in sediment and invertebrate samples collected from a Mediterranean bay in south-east Spain. These represent significant advances in the analysis of antibiotics in environmental samples, especially for wild marine taxa, and attend for a proper assessment of the environmental fate and side effects of aquaculture antibiotics in the marine environment.

Long-range transport of airborne microbes over the global tropical and subtropical ocean.

The atmosphere plays a fundamental role in the transport of microbes across the planet but it is often neglected as a microbial habitat. Although the ocean represents two thirds of the Earth's surface, there is little information on the atmospheric microbial load over the open ocean. Here we provide a global estimate of microbial loads and air-sea exchanges over the tropical and subtropical oceans based on the data collected along the Malaspina 2010 Circumnavigation Expedition. Total loads of airborne prokaryotes and eukaryotes were estimated at 2.2 × 1021 and 2.1 × 1021 cells, respectively. Overall 33-68% of these microorganisms could be traced to a marine origin, being transported thousands of kilometres before re-entering the ocean. Moreover, our results show a substantial load of terrestrial microbes transported over the oceans, with abundances declining exponentially with distance from land and indicate that islands may act as stepping stones facilitating the transoceanic transport of terrestrial microbes.The extent to which the ocean acts as a sink and source of airborne particles to the atmosphere is unresolved. Here, the authors report high microbial loads over the tropical Atlantic, Pacific and Indian oceans and propose islands as stepping stones for the transoceanic transport of terrestrial microbes..

Dysregulation of photosynthetic genes in oceanic Prochlorococcus populations exposed to organic pollutants.

The impact of organic pollutants on oceanic ecosystem functioning is largely unknown. Prochlorococcus, the most abundant known photosynthetic organism on Earth, has been suggested to be especially sensible to exposure to organic pollutants, but the sub-lethal effects of organic pollutants on its photosynthetic function at environmentally relevant concentrations and mixtures remain unexplored. Here we show the modulation of the expression of two photosynthetic genes, rbcL (RuBisCO large subunit) and psbA (PSII D1 protein), of oceanic populations of Prochlorococcus from the Atlantic, Indian and Pacific Oceans when exposed to mixtures of organic pollutants consisting of the non-polar fraction of a seawater extract. This mixture included most persistent organic pollutants, semivolatile aromatic-like compounds, and the unresolved complex mixture of hydrocarbons. Prochlorococcus populations in the controls showed the expected diel cycle variations in expression of photosynthetic genes. However, exposure to a complex mixture at concentrations only 2-fold above the environmental levels resulted in a decrease of expression of both genes, suggesting an effect on the photosynthetic function. While organic pollutant effects on marine phytoplankton have been already demonstrated at the cellular level, this is the first field study showing alterations at the molecular level of the photosynthetic function due to organic pollutants.

Accumulation of Perfluoroalkylated Substances in Oceanic Plankton.

The bioaccumulation of perfluoroalkylated substances (PFASs) in plankton has previously been evaluated only in freshwater and regional seas, but not for the large oligotrophic global oceans. Plankton samples from the tropical and subtropical Pacific, Atlantic and Indian Oceans were collected during the Malaspina 2010 circumnavigation expedition, and analyzed for 14 ionizable PFASs, including perfluorooctanoate (PFOA), perfluorooctanesulfonate (PFOS) and their respective linear and branched isomers. PFOA and PFOS concentrations in plankton ranged from 0.1 to 43 ng gdw-1 and from 0.5 to 6.7 ng gdw-1, respectively. The relative abundance of branched PFOA in the northern hemisphere was correlated with distance to North America, consistent with the historical production and coherent with previously reported patterns in seawater. The plankton samples showing the highest PFOS concentrations also presented the largest relative abundances of branched PFOS, suggesting a selective cycling/fractionation of branched PFOS in the surface ocean mediated by plankton. Bioaccumulation factors (BAFs) for plankton were calculated for six PFASs, including short chain PFASs. PFASs Log BAFs (wet weight) ranged from 2.6 ± 0.8 for perfluorohexanesulfonic acid (PFHxS), to 4.4 ± 0.6 for perfluoroheptanoic acid (PFHpA). The vertical transport of PFASs due to the settling of organic matter bound PFAS (biological pump) was estimated from an organic matter settling fluxes climatology and the PFAS concentrations in plankton. The global average sinking fluxes were 0.8 ± 1.3 ng m-2d-1 for PFOA, and 1.1 ± 2.1 ng m-2d-1 for PFOS. The residence times of PFAS in the surface ocean, assuming the biological pump as the unique sink, showed a wide range of variability, from few years to millennia, depending on the sampling site and individual compound. Further process-based studies are needed to constrain the oceanic sink of PFAS.

Organophosphate Ester Flame Retardants and Plasticizers in the Global Oceanic Atmosphere.

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers and have been detected ubiquitously in the remote atmosphere. Fourteen OPEs were analyzed in 115 aerosol phase samples collected from the tropical and subtropical Atlantic, Pacific, and Indian Oceans during the MALASPINA circumnavigation campaign. OPEs were detected in all samples with concentrations ranging from 360 to 4400 pg m-3 for the sum of compounds. No clear concentration trends were found between the Northern and Southern hemispheres. The pattern was generally dominated by tris(1-chloro-2-propyl) phosphate (TCPP), although tri-n-butyl phosphate (TnBP) had a predominant role in samples close to continents and in those influenced by air masses originating in continents. The dry deposition fluxes of aerosol phase ∑14OPE ranged from 4 to 140 ng m-2 d-1. An estimation of the OPE gas phase concentration and gross absorption fluxes by using three different sets of physical chemical properties suggested that the atmosphere-ocean diffusive exchange of OPEs could be 2-3 orders of magnitude larger than dry deposition. The associated organic phosphorus inputs coming from diffusive OPE fluxes were estimated to potentially trigger up to 1.0% of the reported primary production in the most oligotrophic oceanic regions. However, the uncertainty associated with these calculations is high and mostly driven by the uncertainty of the physical chemical properties of OPEs. Further constraints of the physical chemical properties and fluxes of OPEs are urgently needed, in order to estimate their environmental fate and relevance as a diffusive source of new organic phosphorus to the ocean.

Oceanic Sink and Biogeochemical Controls on the Accumulation of Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, and Biphenyls in Plankton.

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) were measured in plankton samples from the Atlantic, Pacific, and Indian Oceans collected during the Malaspina circumnavigation cruise. The concentrations of PCDD/Fs and dl-PCBs in plankton averaged 14 and 240 pg gdw(-1), respectively, but concentrations were highly variable. The global distribution of PCDD/Fs and dl-PCBs was not driven by proximity to continents but significantly correlated with plankton biomass, with higher plankton phase PCDD/F and dl-PCB concentrations at lower biomass. These trends are consistent with the interactions between atmospheric deposition, biomass dilution, and settling fluxes of organic matter in the water column (biological pump), as key processes driving POPs plankton phase concentrations in the global oceans. The application of a model of the air-water-plankton diffusive exchange reproduces in part the influence of biomass on plankton phase concentrations and suggests future modeling priorities. The estimated oceanic sink (Atlantic, Pacific, and Indian Oceans) due to settling fluxes of organic matter bound PCDD/Fs and dl-PCBs is of 400 and 10,500 kg y(-1), respectively. The atmospheric inputs due to gross diffusive absorption and dry deposition are nearly 3 and 10 times larger for PCDD/Fs and dl-PCBs, respectively, than the oceanic sink. These observations suggest that the coupling of atmospheric deposition with water column cycling supports and drives the accumulation of dl-PCBs and PCDD/Fs in plankton from the global oligotrophic oceans.

Perfluoroalkylated substances in the global tropical and subtropical surface oceans.

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.

Background concentrations of polychlorinated dibenzo-p-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-p-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 Hespérides. 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-p-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-p-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 (vD). PAH dry deposition fluxes (FDD) bound to coarse aerosols were higher than those of fine aerosols for 83% of the measurements. Average FDD for total (fine + coarse) Σ16PAHs (sum of 16 individual PAHs) ranged from 8.33 ng m(-2)d(-1) to 52.38 ng m(-2)d(-1). Mean FDD for coarse aerosol's individual PAHs ranged between 0.13 ng m(-2)d(-1) (Perylene) and 1.96 ng m(-2)d(-1) (Methyl Pyrene), and for the fine aerosol fraction these ranged between 0.06 ng m(-2)d(-1) (Dimethyl Pyrene) and 1.25 ng m(-2)d(-1) (Methyl Chrysene). The estimated deposition velocities went from the highest mean vD 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 vD 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.