Little is known about the distribution of polybrominated diphenyl ethers (PBDE) -also known as flame retardants- in major ocean compartments, with no reports yet for the large deep-water masses of ...the Arctic Ocean. Here, PBDE concentrations, congener patterns and inventories are presented for the different water masses of the pan-Arctic shelf seas and the interior basin. Seawater samples were collected onboard three cross-basin oceanographic campaigns in 2001, 2005, and 2008 following strict trace-clean protocols. ∑14PBDE concentrations in the Polar Mixed Layer (PML; a surface water mass) range from 0.3 to 11.2 pg·L–1, with higher concentrations in the pan-Arctic shelf seas and lower levels in the interior basin. BDE-209 is the dominant congener in most of the pan-Arctic areas except for the ones close to North America, where penta-BDE and tetra-BDE congeners predominate. In deep-water masses, ∑14PBDE concentrations are up to 1 order of magnitude higher than in the PML. Whereas BDE-209 decreases with depth, the less-brominated congeners, particularly BDE-47 and BDE-99, increase down through the water column. Likewise, concentrations of BDE-71 -a congener not present in any PBDE commercial mixture- increase with depth, which potentially is the result of debromination of BDE-209. The inventories in the three water masses of the Central Arctic Basin (PML, intermediate Atlantic Water Layer, and the Arctic Deep Water Layer) are 158 ± 77 kg, 6320 ± 235 kg and 30800 ± 3100 kg, respectively. The total load of PBDEs in the entire Arctic Ocean shows that only a minor fraction of PBDEs emissions are transported to the Arctic Ocean. These findings represent the first PBDE data in the deep-water compartments of an ocean.
There is a scarcity of data on the amount and distribution of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) and its metabolites in intermediate and deep ocean water masses. Here, ...the distribution and inventories of DDTs in water of the Arctic shelf seas and the interior basin are presented. The occurrence of ∑6DDT (0.10–66 pg L–1) in the surface water was dominated by 4,4′-DDE. In the Central Arctic Ocean increasing concentrations of DDE with depth were observed in the Makarov and Amundsen basins. The increasing concentrations down to 2500 m depth is in accordance with previous findings for PCBs and PBDEs. Similar concentrations of DDT and DDEs were found in the surface water, while the relative contribution of DDEs increased with depth, demonstrating a transformation over time and depth. Higher concentrations of DDTs were found in the European part of the Arctic Ocean; these distributions likely reflect a combination of different usage patterns, transport, and fate of these compounds. For instance, the elevated concentrations of DDTs in the Barents and Atlantic sectors of the Arctic Ocean indicate the northbound Atlantic current as a significant conveyor of DDTs. This study contributes to the very rare data on OCPs in the vast deep-water compartments and combined with surface water distribution across the Arctic Ocean helps to improve our understanding of the large-scale fate of DDTs in the Arctic.
Given the potential for permafrost carbon (PF/C)‐climate feedbacks in the Siberian‐Arctic land‐ocean system, there is a need for understanding the fate of thawed‐out PF/C. Here we show that the ...sequestration of OC by reactive iron (OC‐Fe) ranges between 0.5 and 22% on the Eurasian Arctic Shelf, with higher values in the Kara Sea (KS) (18 ± 6%) and the Laptev Sea (LS) (14 ± 4%). The Δ14C/δ13C signatures of the OC‐Fe are substantially older and more terrestrial than the bulk sediment OC in the LS but younger and more dominated by marine plankton sources in the East Siberian Sea (ESS). Statistical source apportionment modeling reveal that reactive iron phases resequestered 15 ± 5% of thawing PF/C in the LS and 6.4 ± 5% in the ESS, derived from both coastal erosion of ice complex deposit and thawing topsoil. This Fe‐associated trap of PF/C constitutes a reduction of the degradation/outgassing and thus also an attenuation of the PF/C‐climate feedback.
Key Points
Insights on what OC fractions are trapped by reactive Fe phases
The thawed PF/C is partly trapped by reactive Fe on the largest Arctic shelf
This rusty carbon sink attenuates the PF/C‐climate feedback
The effect of shear-enhanced filtration by vibratory process in microalgae dewatering is presented in this paper. The aim of this research was to investigate the technical performance and improvement ...of vibrating membrane filtration compared with conventional tangential cross-flow filtration in microalgae concentration. An industrial-scale available commercial set-up was used. Several membrane materials as polyethersulfone, polyacrylonitrile, etc., and mean pore sizes (from 7000Da to 0.2μm) were tested and compared in both filtration set-ups. Experiments were carried-out with Nannochloropsis gaditana and Phaeodactylum tricornutum microalgae. It has been demonstrated that, even if the choice of the membrane depends on its cut-off, its material and the type of microalgae filtrated, dynamic filtration is always the best technology over a conventional one. If with conventional filtration permeability values were in the vicinity of 10L/h/m(2)/bar in steady state phase, with dynamic filtration these values increased to 30L/h/m(2)/bar or more.
The marine diatom
Thalassiosira pseudonana
grown under air (0.04% CO
2
) and 1 and 5% CO
2
concentrations was evaluated to determine its potential for CO
2
mitigation coupled with biodiesel ...production. Results indicated that the diatom cultures grown at 1 and 5% CO
2
showed higher growth rates (1.14 and 1.29 div day
−1
, respectively) and biomass productivities (44 and 48 mg
AFDW
L
−1
day
−1
) than air grown cultures (with 1.13 div day
−1
and 26 mg
AFDW
L
−1
day
−1
). The increase of CO
2
resulted in higher cell volume and pigment content per cell of
T
.
pseudonana
. Interestingly, lipid content doubled when air was enriched with 1–5% CO
2
. Moreover, the analysis of the fatty acid composition of
T
.
pseudonana
revealed the predominance of monounsaturated acids (palmitoleic-16:1 and oleic-18:1) and a decrease of the saturated myristic acid-14:0 and polyunsaturated fatty acids under high CO
2
levels. These results suggested that
T
.
pseudonana
seems to be an ideal candidate for biodiesel production using flue gases.
Fiberboards are readily available components which can be used in construction for various functions such as furniture, insulation, or soundproofing. Research in the field of fiberboards has ...developed considerably in trying to match the practical needs of the construction element together with the new environmental challenges, that favour the production of panels in using by-products without adhesives. This review article presents an overview on fiberboard production and may offer a way to establish all the necessary steps to make binderless fiberboards attractive on the market, by considering economic and sustainable issues. Feedstock procurement is analysed, considering the effect of chemical composition of raw material on fiberboard quality. Lignin represents the most important component for bonding ability. However, at the same time, the need to use a by-product, which may result in choosing a material with less lignin and more hemicelluloses, will worsen dimensional stability, and therefore, a pre-treatment of lignocellulosic material may be necessary. Many pre-treatments have been studied and optimised in recent years. This paper analyses mechanical, chemical, hydrothermal and biological ones, and considers the pros and cons of each one of them. The choice of pre-treatment depends on which result is to be achieved. Some applications are considered to conclude the production chain. What emerges is that the application phase is not yet fully developed and scaling up from laboratory to the industrial stage is not yet achieved.
•It is possible to use lignocellulosic by-products to produce fiberboard panels.•Those panels can be manufactured without the addition of any fossil molecule.•The fiberboards can surpass accomplishing the (construction) parameter (exterior/interior) specifications.•The resulting panels have the potential of being produced and being economically competitive with other commercial methods.
The purpose of this study was to explore efficient methods of harvesting the microalga Phaeodactylum tricornutum. Natural sedimentation experiments, performed at different light and temperature ...conditions, did not yield significant improvements in efficiency even after 1 week. When alkalinity-induced flocculation was performed, both the flocculation efficiency and the concentration factor dramatically improved at pH = 9.75 (0.5–0.7 units over the original pH of the culture) after 10 min settling time. Sedimentation rates are documented at pH ranging between pH 9.75 and 11.0. The results of the application of two conventional flocculants used in wastewater treatment, polyaluminium chloride and aluminium sulphate, are also presented. Chitosan was also used as a natural flocculating agent to improve possible contamination problems in the downstream process. pH was adjusted in order to determine optimum flocculation efficiency of chitosan in combination with a high concentration factor. Satisfactory results were found with chitosan at an adjusted pH of 9.9 using concentrations as low as 20 mg L−1, after testing a flocculant range of 5–200 mg L−1.
The aim of this study is to completely characterize technical lignins so they can be incorporated into phenolic resins such as phenol–formaldehyde. Technical lignins such as Kraft (KL), ...lignosulfonate (LS), soda-anthraquinone (SAL), organosolv (OSL) and ethanol process lignins (EPL) were characterized by elemental analysis, functional groups analysis, molecular weight distribution, Mannich reactivity and other techniques.
Results from elemental analysis (% nitrogen), ash content and polysaccharides show that all these lignins have a high level of purity after treatment except for lignosulfonate, which has a high ash content, and ethanol process lignin, which has a high nitrogen content. We discuss the results of the functional analysis and molecular weight distribution (
M
w,
M
n,
M
w/
M
n) for all lignins in order to select a good lignin for adhesive production. After characterizing the lignins, we provide an approximate C
9 formula and active reaction sites for each lignin.
Our study of lignin reactivity by Mannich reactivity and UV-spectroscopy shows that Kraft and soda-anthraquinone lignins are more reactive towards modification than the others studied. These lignins may be good raw material for lignin derivatives such as lignin-based phenol–formaldehyde resins.
Ongoing global warming in high latitudes may cause an increasing supply of permafrost-derived organic carbon through both river discharge and coastal erosion to the Arctic shelves. Mobilized ...permafrost carbon can be either buried in sediments, transported to the deep sea or degraded to CO2 and outgassed, potentially constituting a positive feedback to climate change. This study aims to assess the fate of terrigenous organic carbon (TerrOC) in the Arctic marine environment by exploring how it changes in concentration, composition and degradation status across the wide Laptev Sea shelf. We analyzed a suite of terrestrial biomarkers as well as source-diagnostic bulk carbon isotopes (δ13C, Δ14C) in surface sediments from a Laptev Sea transect spanning more than 800 km from the Lena River mouth (< 10 m water depth) across the shelf to the slope and rise (2000–3000 m water depth). These data provide a broad view on different TerrOC pools and their behavior during cross-shelf transport. The concentrations of lignin phenols, cutin acids and high-molecular-weight (HMW) wax lipids (tracers of vascular plants) decrease by 89–99 % along the transect. Molecular-based degradation proxies for TerrOC (e.g., the carbon preference index of HMW lipids, the HMW acids ∕ alkanes ratio and the acid ∕ aldehyde ratio of lignin phenols) display a trend to more degraded TerrOC with increasing distance from the coast. We infer that the degree of degradation of permafrost-derived TerrOC is a function of the time spent under oxic conditions during protracted cross-shelf transport. Future work should therefore seek to constrain cross-shelf transport times in order to compute a TerrOC degradation rate and thereby help to quantify potential carbon–climate feedbacks.
The significance of the offshore vertical convection currents in the transport and sinking of water-soluble organic pollutants into marine deep basins has been evaluated. For this purpose, sediment ...cores were collected in the Gulf of Lion (GoL) at sites between 26 and 2330 m water depth. The top core layers were analyzed for aromatic and aliphatic hydrocarbons and organochlorine compounds. Organic compounds with logKAW (air water partition coefficient) between −2 and −4, e.g. lindane, PCB 28, PCB 52, phenanthrene, methylphenanthrenes, dimethylphenanthrenes, C14–C23n-alkanes, are found in higher concentrations or exhibit relative concentration increases in the sediments deposited in the continental rise as consequence of the open-sea convection processes associated with the formation of Western Mediterranean Deep Water (WMDW). In contrast, the organic pollutants with intermediate air-water distribution coefficients, logKAW between −2 and 0, and high octanol water distribution coefficients (logKow > 6), e.g. highly chlorinated PCBs, DDTs, DDEs, DDDs, C25–C35n-alkanes, and polycyclic aromatic hydrocarbons with molecular weight higher than 200, occur in association to sediment particles, which are mainly transported by the Northern current along the continental shelf forming the mud belt. The Rhône prodelta is therefore the area of the GoL showing the highest concentrations of this group of organic compounds, which are preferentially associated with water particles. Overall, the results show that vertical open-sea convection processes related with offshore formation of WMDW may have an important role in the transport and accumulation of water soluble pollutants to deep marine environments of the GoL (>2000 m water depth).
Display omitted
•Lindane is more abundant in the continental rise of the GoL than in the mud belt.•Open-sea convection accumulates organic compounds in the continental rise.•Sea convection enhances the transport of low hydrophobic compounds to deep waters.•The Rhone prodelta is a sink for the river discharged hydrophobic organochlorines.•Hydrophobic organochlorines and river particles in the GoL show similar distributions.
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