Arctic haze is a seasonal phenomenon with high concentrations of accumulation-mode aerosols occurring in the Arctic in winter and early spring. Chemistry transport models and climate chemistry models ...struggle to reproduce this phenomenon, and this has recently prompted changes in aerosol removal schemes to remedy the modeling problems. In this paper, we show that shortcomings in current emission data sets are at least as important. We perform a 3 yr model simulation of black carbon (BC) with the Lagrangian particle dispersion model FLEXPART. The model is driven with a new emission data set ("ECLIPSE emissions") which includes emissions from gas flaring. While gas flaring is estimated to contribute less than 3% of global BC emissions in this data set, flaring dominates the estimated BC emissions in the Arctic (north of 66° N). Putting these emissions into our model, we find that flaring contributes 42% to the annual mean BC surface concentrations in the Arctic. In March, flaring even accounts for 52% of all Arctic BC near the surface. Most of the flaring BC remains close to the surface in the Arctic, so that the flaring contribution to BC in the middle and upper troposphere is small. Another important factor determining simulated BC concentrations is the seasonal variation of BC emissions from residential combustion (often also called domestic combustion, which is used synonymously in this paper). We have calculated daily residential combustion emissions using the heating degree day (HDD) concept based on ambient air temperature and compare results from model simulations using emissions with daily, monthly and annual time resolution. In January, the Arctic-mean surface concentrations of BC due to residential combustion emissions are 150% higher when using daily emissions than when using annually constant emissions. While there are concentration reductions in summer, they are smaller than the winter increases, leading to a systematic increase of annual mean Arctic BC surface concentrations due to residential combustion by 68% when using daily emissions. A large part (93%) of this systematic increase can be captured also when using monthly emissions; the increase is compensated by a decreased BC burden at lower latitudes. In a comparison with BC measurements at six Arctic stations, we find that using daily-varying residential combustion emissions and introducing gas flaring emissions leads to large improvements of the simulated Arctic BC, both in terms of mean concentration levels and simulated seasonality. Case studies based on BC and carbon monoxide (CO) measurements from the Zeppelin observatory appear to confirm flaring as an important BC source that can produce pollution plumes in the Arctic with a high BC / CO enhancement ratio, as expected for this source type. BC measurements taken during a research ship cruise in the White, Barents and Kara seas north of the region with strong flaring emissions reveal very high concentrations of the order of 200–400 ng m−3. The model underestimates these concentrations substantially, which indicates that the flaring emissions (and probably also other emissions in northern Siberia) are rather under- than overestimated in our emission data set. Our results suggest that it may not be "vertical transport that is too strong or scavenging rates that are too low" and "opposite biases in these processes" in the Arctic and elsewhere in current aerosol models, as suggested in a recent review article (Bond et al., Bounding the role of black carbon in the climate system: a scientific assessment, J. Geophys. Res., 2013), but missing emission sources and lacking time resolution of the emission data that are causing opposite model biases in simulated BC concentrations in the Arctic and in the mid-latitudes.
Despite relatively good knowledge of the biogeochemistry of Siberian thermokarst lakes during summer base flow, their seasonal dynamics remains almost unexplored. This work describes the chemical ...composition of ~130 thermokarst lakes ranging in size from a few m2 to several km2, located in the discontinuous permafrost zone. Lakes were sampled during spring flood, just after the ice break (early June), the end of summer (August), the beginning of ice formation (October) and during the full freezing season in winter (February). The lakes larger than 1000 m2 did not exhibit any statistically significant control of the lake size on dissolved organic carbon (DOC), the major and trace element concentrations over three major open water seasons. On the annual scale, the majority of dissolved elements including organic carbon increased their concentration from 30 to 500%, with a statistically significant (p < 0.05) trend from spring to winter. The concentrations of most trace elements (TEs) increased in the order spring > summer > autumn > winter. The ice formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the ice surface. This water was subsequently frozen and formed layered ice rich in organic matter. As a result, the DOC and metal (Mn, Fe, Ni, Cu, Zn, As, Ba and Pb) concentrations were highest near the surface of the ice column (0 to 20 cm) and decreased by a factor of 2 towards the bottom. The main implications of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficients of a TE between amorphous organo-ferric coagulates and lake water (<0.45 μm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (<1 kDa, or <1–2 nm) fractions of thermokarst lake waters, suggesting massive co-precipitation of TE with amorphous Fe oxyhydroxide stabilized by organic matter. Although the concentration of most elements was lowest in spring, this period of maximal water coverage of land created a significant reservoir of DOC and soluble metals in the water column that can be easily mobilized to the hydrological network. The highest DOC concentration observed in the smallest (<100 m2) water bodies in spring suggests their strongly heterotrophic status and, therefore, a potentially elevated CO2 flux from the lake surface to the atmosphere.
A comprehensive study of the magnetic behavior, morphology, and composition of Fe-containing oxide coatings on aluminum and titanium has been carried out to investigate the origin of their ...ferromagnetism. The coatings have been formed by the plasma electrolytic oxidation (PEO) technique in slurry electrolytes containing colloidal particles of iron(III) hydroxides. On the surface of coatings on Al, iron is distributed unevenly concentrating in defective areas with a large number of small pores, and near large pores. On the surface of coatings on Ti, iron and titanium are distributed in antiphase in areas of comparable size. Within the pores, iron concentration appears about 5–10 times higher and oxygen concentration 3–4 times lower than their average concentration over the surface. In both cases, localization of the areas with ferromagnetic properties follows the peculiarities of iron distribution on the surface. The magnetic fraction in the coatings on aluminum appears to be represented by iron-aluminum spinel Fe3-xAlxO4 with x > 0.06, likely cation-deficient. Elemental iron and traces of iron hydroxides are also possibly present. In the coatings on titanium, titanomagnetite (Fe3-xTixO4, where x ∼ 0.2–0.3) or its oxidized analogue, titanomaghemite, appear to be present, and possibly also some Fe–Ti alloy particles.
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•Oxide layers are formed on Al and Ti in electrolytes with iron hydroxides.•Ferromagnetism at 2–900 K, composition and surface morphology were studied.•The concentration of iron in the pores is 5–10 times higher than on the surface.•Iron oxides and/or Fe-particles are responsible for ferromagnetism of Al samples.•Titanomagnetites and/or Fe–Ti particles give ferromagnetic properties to Ti-samples.
The estuarine behavior of organic carbon (OC) and trace elements (TE) was studied for the largest European sub-Arctic river, which is the Severnaya Dvina; this river has a deltaic estuary covered in ...ice during several hydrological seasons: summer (July 2010, 2012) and winter (March 2009) baseflow, and the November-December 2011 ice-free period. Colloidal forms of OC and TE were assessed for three pore size cutoffs (1, 10, and 50 kDa) using an in situ dialysis procedure. Conventionally dissolved (< 0.22 mu m) fractions demonstrated clear conservative behavior for Li, B, Na, Mg, K, Ca, Sr, Mo, Rb, Cs, and U during the mixing of freshwater with the White Sea; a significant (up to a factor of 10) concentration increase occurs with increases in salinity. Si and OC also displayed conservative behavior but with a pronounced decrease in concentration seawards. Rather conservative behavior, but with much smaller changes in concentration (variation within plus or minus 30%) over a full range of salinities, was observed for Ti, Ni, Cr, As, Co, Cu, Ga, Y, and heavy REE. Strong non-conservative behavior with coagulation/removal at low salinities (< 5ppt) was exhibited by Fe, Al, Zr, Hf, and light REE. Finally, certain divalent metals exhibited non-conservative behavior with a concentration gain at low (~ 2-5ppt, Ba, Mn) or intermediate (~ 10-15ppt, Ba, Zn, Pb, Cd) salinities, which is most likely linked to TE desorption from suspended matter or sediment outflux. The most important result of this study is the elucidation of the behavior of the "truly" dissolved low molecular weight LMW< 1 kDa fraction containing Fe, OC, and a number of insoluble elements. The concentration of the LMW fraction either remains constant or increases its relative contribution to the overall dissolved (< 0.22 mu m) pool as the salinity increases. Similarly, the relative proportion of colloidal (1 kDa-0.22 mu m) pool for the OC and insoluble TE bound to ferric colloids systematically decreased seaward, with the largest decrease occurring at low (< 5ppt) salinities. Overall, the observed decrease in the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the HMW1 kDa-0.22 mu m portion by the LMW< 1 kDa fraction. These patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable) fraction of the OC, Fe and insoluble TE. The size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. In particular, LMW< 1 kDa ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous DOM and/or photodestruction. Given the relatively low concentration of particulate versus dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. As a result, the majority of dissolved components exhibited either conservative (OC and related elements such as divalent metals) or non-conservative, coagulation-controlled (Fe, Al, and insoluble TE associated with organo-ferric colloids) behavior. The climate warming at high latitudes is likely to intensify the production of LMW< 1 kDa organic ligands and the associated TE; therefore, the delivery of potentially bioavailable trace metal micronutrients from the land to the ocean may increase.
The cytotoxicity of doxorubicin (Dox) and its peptide modifications Z-Gly-Pro-Dox and Boc-Gly-Pro-Dox were studied.
Tetrahymena pyriformis
was used as a test system, which made it possible, due to ...the short life cycle and high reproduction rate of ciliates, to trace their response to the effects of toxicants over several generations. It was found that peptide modification of the Dox molecule markedly reduces its cytotoxic and cytostatic effect. The Z-Gly-Pro-Dox modification has less cytotoxic and cytostatic effect compared to Boc-Gly-Pro-Dox. When determining the ability of drugs (at a concentration of 100 μM) to prevent bacterial contamination of samples, it was shown that the smallest degree of overgrowth was recorded in the presence of Dox (OD
600nm
81.1). Boc-Gly-Pro-Dox also had a bacteriostatic effect, though less pronounced (OD
600nm
93.8). The degree of overgrowth in the presence of Z-Gly-Pro-Dox was close to that of distilled water. The results obtained on ciliates did not contradict the data obtained in similar studies on mice.
The influence of various factors on the efficiency of introducing deuterium into 3-(
N
-pyrrolyl)-propanoyl-L-histidine and 3-(
N
-salicyl)-propanoyl-L-histidine was studied. Heavy water was used as ...a source of deuterium. It is shown that the content of deuterium atoms in the substance can be increased by pretreating the reaction mixture with deuterium gas. The new approach opens up additional possibilities both for obtaining high labeled pharmaceuticals by introducing hydrogen isotopes into organic compounds, and theoretically for a deeper understanding of the role in this process of activated deuterium or tritium particles solvated on the carrier and in the pool of matter.
Thermokarst (thaw) lakes of the Western Siberian Lowland (WSL), the World´s largest permafrost peatland, contain important but poorly constrained stocks of organic carbon (OC) and nitrogen. These ...lakes are highly vulnerable to climate warming and permafrost thaw. The present work aims to quantify the OC and total nitrogen (TN) stocks and accumulation rates in sediments of 11 thermokarst lakes in the WSL across a permafrost gradient, from isolated to discontinuous and continuous permafrost. We found an increase in OC and TN stocks in lake sediments (0–30 cm) from the northern taiga with sporadic permafrost (285 Tg C and 10.5 Tg N) to the tundra zone with continuous permafrost (628 Tg C and 26 Tg N). The upper 30 cm thermokarst lake sediments of the permafrost-affected WSL store 1250 ± 35 Tg C and 50 ± 1.4 Tg N). The OC accumulation rates in thermokarst lake sediments ranged from 36 to 250 g C m
−2
year
−1
, which is 5 to 10 times higher than C accumulation rates in peatlands of western Siberia. The total OC accumulation in lakes of WSL is 7.8 ± 0.7 Tg C year
−1
. This is about 24–47% of the C emission from the WSL thermokarst lakes, implying that it represents an important factor in the C budget to consider in order to understand impacts of climate change and permafrost thaw on the C cycle.
Peptide derivatives of dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) acylated with lauric acid (LA) and oleic acid (OA), including LA-Gly-Pro-DA, LA-Gly-Pro-5-HT, OA-Gly-Pro-DA, and ...OA-Gly-Pro-5-HT, were synthesized. A mass spectrometric method for assessing the content of the DA and 5-HT derivatives in phosphate buffered saline (PBS Am-E404 – 100, pH 7.4) was developed. It was shown that these compounds could penetrate through artificial membranes. A special mixture of these compounds was used for modeling a situation where the molecules of DAand 5-HT derivatives diffused through the membrane as a result of their competitive interaction, which allowed a reliable determination of which compounds in the mixture penetrated more easily through artificial membranes. The comparative permeability of the blood–brain barrier (BBB) was evaluated by the method of parallel artificial membrane permeability assay (PAMPA). It was established that derivatives LA-Gly-Pro-5-HT and LA-Gly-Pro-DA, which were acylated by LA, were most promising for overcoming the BBB.
Objective:
The resistance of carnosine, pyrrolylcarnosine (PC) and salicylcarnosine (SC) to the action of leucine aminopeptidase and carboxypeptidases B and Y was evaluated.
Methods:
Proteolysis of ...carnosine and its derivatives under the action of leucine aminopeptidase, carboxypeptidases Y and B, or under the action of enzyme systems of plasma membranes of rat brain cells or blood plasma.
Results and Discussion:
It was found that proteolysis of carnosine, PC and SC under the action of leucine aminopeptidase does not occur. Carboxypeptidases B and Y, as well as the enzyme systems of blood plasma and plasma membranes of rat brain cells, degraded peptides containing β-alanyl,
N
-pyrrolyl,
N
-salicylic fragments to varying degrees. In all cases, histidine was formed. The formation of pyrrole or salicylic acid did not occur.
Conclusions:
It was found that carnosine, PC and SC showed high resistance to the action of amino- and carboxypeptidases in
in
vitro
experiments.
The amidoalkylation of a phosphonous acid containing a structural isostere of diethyl glutamiate, using ethyl carbamate and 3-(methylthio)propionaldehyde, was proposed for the synthesis of ...NC(O)OEt-protected phosphinic pseudo-Met-Glu-peptide. Subsequent adamantyl protection of the phosphorylic function and hydrolysis of carboxylic groups made it possible to obtain phosphinic Met-P-Glu peptide in the form of cyclic glutamate anhydride. It was found that the latter reacts with the third amino acid component histidine to form the phosphinic Met-P-Glu-γ-His tripeptide.
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