The recent intensification of energy resource exploration and human activities in the Barents Sea (BS) requires a more thorough assessment of the natural and anthropogenic impact of hydrocarbons on ...the environment. We analyzed a wide set of sensitive indicators, including hydrocarbon molecular markers and organic matter (OM) maturity parameters in the Holocene sediments from three regions of the BS: the Kola-Kanin Monocline (KKM), the Svalbard shelf, and the Shtokman gas-condensate field (GCF). An increase in pyrogenic polycyclic aromatic hydrocarbons toward the core surface traces the intensification of anthropogenic contamination in the KKM region during last century. An input of highly mature OM from the eroded coal rocks of Barentsburg were confirmed by comparison of biomarker distribution in sediments and coals. An increase in biogenic hopanes and hopenes content down-core, and a crude-oil stage of OM maturity in surface sediments of the Shtokman GCF attests to hydrocarbons migration from subsurface strata.
•Recent sediments from Svalbard Shelf, Shtokman and Kola-Kanin Monocline areas studied•Significant variation in hydrocarbons genesis in the Barents Sea sediments detected•Svalbard sediments show the highest level of organic matter maturity.•In the Shtokman area, molecular marker distributions indicated hydrocarbon migration•Sediment PAH composition of Kola-Kanin Monocline suggested anthropogenic impact.
Growing anthropogenic activity in the Arctic, especially near regional municipal and transportation hubs, threatens coastal environments with significant changes and contamination. A detailed study ...of a wide set of organic-geochemical proxies in surface and subsurface sediments and soils around the typical urbanized Arctic area (Tromsø, Norway) was performed to investigate natural and anthropogenic input of hydrocarbons. The sites were located close to main areas of human activity and differed in the level of anthropogenic pressure: oil terminal, boat harbor and recreation beach zone in the city center, and a remote, conditionally-clean area. The samples from each site were collected along four subtidal – intertidal – supratidal transects. GC–MS data on the distribution of more than 110 compounds were obtained including n-alkanes, isoprenoids, terpanes, parent polycyclic aromatic hydrocarbons (PAHs), and alkyl PAHs. Organic matter embedded in a mineral matrix was more thermally mature than its fresh non-bound fraction. Biomarker distribution and diagnostic ratios attested to the predominantly local origin of near-shore organic matter formation (phytoplankton, algae, high foliar plants, grass). PAH composition revealed a significant input of pyrogenic components from liquid and solid fuel combustion to the surface coarse-grained sediments. Background bacterial activity was evidenced by the high content of biohopanes and hopenes in less polluted sediments and soils. The presence of an unresolved complex mixture and even n-alkanes in sediment profiles from the most polluted sites attested to the active biodegradation that, together with the erosion of the upper layers by tidal currents, reduces the toxic compound penetration deeper into the sediments.
•Organic matter in intertidal deposits of the urbanized Arctic area was studied.•Organic matter bonded with the mineral matrix is of local origin and highly mature.•Variations in organic-geochemical proxies attest to recent human impact.•Contaminants accumulate predominantly in the surface coarse-grained sediments.•Biomarker composition evidences biodegradation process in polluted sites.
•CNT cloth affords flexible binder-free electrode with resistivity as low as 9 µΩ m.•Wet oxidative functionalization pushes the cloth capacitance from 48 up to 71 F g−1.•Carboxylic and phenolic ...surface groups mostly contribute to the pseudocapacitance.•CNT cloth cyclic stability exceeds 98% over 30,000 cycles at 200 mV s−1 scan rate.•Flexible supercapacitor with CNT cloth electrodes shows excellent performance.
Electrochemical recharging behavior of a binder-free flexible carbon nanotube cloth (CNTC) material in respect to aqueous supercapacitor applications is reported. To provide high enough pseudocapacitance, the surface of CNTC was exposed to wet oxidative functionalization by a KMnO4 treatment in an acidic medium. We report the effect of a KMnO4 to CNT molar ratio on capacitance, electrical resistivity and specific surface area of the CNTC material. The change in the composition of oxygen-containing interfacial functional groups attached to the carbon surface is also investigated by X-ray photoelectron spectroscopy and temperature-programmed desorption methods. For the most oxidized CNTC sample the capacitance of ca. 71 F g−1 (29 µF cm−2BET) in 0.5 M H2SO4 (slightly decreasing with a scan rate up to 100 mV s−1) with the retention of ca. 99% during 30,000 recharging cycles as well as specific resistivity of ca. 31 µΩ m are achieved. Finally, two flexible symmetric supercapacitor prototypes based on a 38% H2SO4 solution and operating at 1.3 or 1.5 V were assembled from the freestanding and graphite foil supported functionalized CNTC electrodes, respectively. For the former device, the volumetric capacitance of ca. 22 F cm−3, power density of ca. 10 kW l−1 and energy density of ca. 3 Wh l−1 (per total volume of both electrodes) are demonstrated. The issues of the long-term stability and self-discharge behavior of assembled prototypes are also considered. Reported results allow us to consider the functionalized CNTC material as a promising electrode material for flexible aqueous supercapacitors.
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Polycyclic aromatic hydrocarbons (PAHs) are key contaminants of concern under the Arctic Environmental Monitoring Programme (AMAP) due to their carcinogenic potential. The concentration of the ...different PAH components may be connected to the geochemical background of the sediments, including leakage and erosion of fossil carbon, as well as epigenetic processes such as decaying peat. In other cases there is a human influnce connected to petroleum spills or combustion of fossil fuel or other human activities. The overall goal of this study was to identify and an analyze existing comparable datasets on PAHs from Norwegian and Russian arctic shelves, and use the concentration and composition of PAH components in the selected datasets to assess baseline concentration of PAH, geographical anomalies and sources and routes of transport, as well as the bit human impact. PAHs in 330 samples of surface sediment from the Barents and Kara Sea shelves, collected during the period 1991-1998, have been selected for the study. In the Southwest Barents Sea the nature of PAHs is formed by a complex sedimentation regime made up of inflowing Atlantic and North Sea water, coastal discharges, coastal abrasion and atmospheric transport. The PAHs basically correspond to background compositions with a low but notable anthropogenic influence. In the Northern Barents Sea both concentration and composition of PAHs are genetically (genesis, conditions and level of transformation) connected with eroded sediment material from the Spitsbergen and Franz Josef Land archipelagos. The relative high PAH levels observed off Spitsbergen thus generally may have a non- anthropogenic explanation. In the central part of the Barents Sea the PAH levels in the deep-water bottom sediments are generally low, non-anthropogenic in origin, and determined by endogenous processes. Erosion and re-deposition of Novaya Zemlya strata do not have a significant influence on PAH composition in this part of the Barents Sea. In the Southeast Barents Sea (Pechora Sea) the PAH composition corresponds, in general, well with the PAH allocation in the Barents Sea. However, the terrigenous influence is stronger. The PAH composition exhibits both epigenetic processes (such as the high level of perylene which most probably is derived from decaying peat) and the presence of petrogenic PAH. The latter findings may be due to the influx of rivers draining oil-rich onshore territories. In estuaries and offshore the Kara Sea the PAH composition of bottom sediments reflects the significant influence of river run-off (with the same patterns as in the Pechora Sea), but also atmospheric transport of combustion derived PAHs, most probably from the smelters in Norilsk.
Rat liver chromatin activated by partial hepatectomy is more susceptible to the action of DNAse I than control chromatin isolated from intact liver. The study on the transfer of chromatin material to ...the acid-soluble fraction reveals a higher rate of activated chromatin degradation. Activated chromatin shows also an increased capacity for ethidium bromide (EB) binding as estimated from the isotherms of adsorption. The difference in EB binding between activated and control chromatin is abolished after DNAse I treatment. Conditions of mild digestion with DNAse I have been found under which the number of binding sites for EB per nucleotide decreases to almost the same level in activated and non-activated chromatin. The results suggest a preferential degradation of those DNA sequences in activated chromatin that are responsible for the increase in the ligand binding.
