Sulfate Peak Research Articles

Online single particle measurement of fireworks pollution during Chinese New Year in Nanning

Time-resolved single-particle measurements were conducted during Chinese New Year in Nanning, China. Firework displays resulted in a burst of SO2, coarse mode, and accumulation mode (100–500nm) particles. Through single particle mass spectrometry analysis, five different types of particles (fireworks-metal, ash, dust, organic carbon-sulfate (OC-sulfate), biomass burning) with different size distributions were identified as primary emissions from firework displays. The fireworks-related particles accounted for more than 70% of the total analyzed particles during severe firework detonations. The formation of secondary particulate sulfate and nitrate during firework events was investigated on single particle level. An increase of sulfite peak (80SO3−) followed by an increase of sulfate peaks (97HSO4−+96SO4−) in the mass spectra during firework displays indicated the aqueous uptake and oxidation of SO2 on particles. High concentration of gaseous SO2, high relative humidity and high particle loading likely promoted SO2 oxidation. Secondary nitrate formed through gas-phase oxidation of NO2 to nitric acid, followed by the condensation into particles as ammonium nitrate. This study shows that under worm, humid conditions, both primary and secondary aerosols contribute to the particulate air pollution during firework displays.

Assessing the correlation between the degree of disc degeneration on the Pfirrmann scale and the metabolites identified in HR-MAS NMR spectroscopy

ObjectiveThe objective of this study is to assess the correlation between the degree of degeneration of lumbar discs according to the Pfirrmann classification system and the concentrations of metabolites determined by means of 1H high-resolution magic angle spinning nuclear magnetic resonance (1H HR MAS NMR) spectroscopy. Materials and methodsTwenty-six human intervertebral lumbar discs that were operated on due to degenerative disease were analyzed. Routine preoperative 1.5T, T2-weighed magnetic resonance (MR) images were used to classify the cases according to the Pfirrmann classification system. In all the cases, during microdiscectomy, the fragments of the annulus fibrosus and nucleus pulposus were harvested and their metabolic profile was examined by means of 1H HR MAS. The grades of disc degeneration on the Pfirrmann scale were correlated with the metabolite concentrations. ResultsSpectral analyses of the intervertebral discs with Pfirrmann grades IV and V demonstrated significantly higher concentrations of creatine, glycine, hydroxyproline, alanine, leucine, valine, acetate, isoleucine, α,β-glucose, and myo-inositol, and a lower intensity of the N-acetyl peak of chondroitin sulfate, compared to the spectra with Pfirrmann grade III. ConclusionOur results demonstrate correlations between metabolite concentrations and the degree of lumbar disc degeneration assessed using the Pfirrmann grading system and provide another step toward the potential use of in vivo MR spectroscopy for investigation of biomarkers in lumbar disc degeneration.

Investigation of a deep ice core from the Elbrus western plateau, the Caucasus, Russia

Abstract. A 182 m ice core was recovered from a borehole drilled into bedrock on the western plateau of Mt. Elbrus (43°20´53.9'' N, 42°25´36.0'' E; 5115 m a.s.l.) in the Caucasus, Russia, in 2009. This is the first ice core in the region that represents a paleoclimate record that is practically undisturbed by seasonal melting. Relatively high snow accumulation rates at the drilling site enabled the analysis of the intraseasonal variability in climate proxies. Borehole temperatures ranged from −17 °C at 10 m depth to −2.4 °C at 182 m. A detailed radio-echo sounding survey showed that the glacier thickness ranged from 45 m near the marginal zone of the plateau up to 255 m at the glacier center. The ice core has been analyzed for stable isotopes (δ18O and δD), major ions (K+, Na+, Ca2+, Mg2+, NH4+, SO42-, NO3-, Cl-, F-), succinic acid (HOOCCH2COOH), and tritium content. The mean annual net accumulation rate of 1455 mm w.e. for the last 140 years was estimated from distinct annual oscillations of δ18O, δD, succinic acid, and NH4+. Annual layer counting also helped date the ice core, agreeing with the absolute markers of the tritium 1963 bomb horizon located at the core depth of 50.7 m w.e. and the sulfate peak of the Katmai eruption (1912) at 87.7 m w.e. According to mathematical modeling results, the ice age at the maximum glacier depth is predicted to be ~ 660 years BP. The 2009 borehole is located downstream from this point, resulting in an estimated basal ice age of less than 350–400 years BP at the drilling site. The glaciological and initial chemical analyses from the Elbrus ice core help reconstruct the atmospheric history of the European region.

Impact of wildfires on size-resolved aerosol composition at a coastal California site

Size-resolved aerosol composition measurements were conducted at a coastal site in central California during the Nucleation in California Experiment (NiCE) between July and August of 2013. The site is just east of ship and marine emission sources and is also influenced by continental pollution and wildfires, such as those near the California–Oregon border which occurred near the end of NiCE. Two micro-orifice uniform deposit impactors (MOUDIs) were used, and water-soluble and elemental compositions were measured. The five most abundant water-soluble species (in decreasing order) were chloride, sodium, non-sea salt (nss) sulfate, ammonium, and nitrate. During wildfire periods, nss K mass concentrations were not enhanced as strongly as other species in the sub-micrometer stages and even decreased in the super-micrometer stages; species other than nss K are more reliable tracers for biomass burning in this region. Chloride levels were reduced in the fire sets likely due to chloride depletion by inorganic and organic acids that exhibited elevated levels in transported plumes. During wildfire periods, the mass size distribution of most dicarboxylic acids changed from unimodal to bimodal with peaks in the 0.32 μm and 1.0–1.8 μm stages. Furthermore, sulfate's peak concentration shifted from the 0.32 μm to 0.56 μm stage, and nitrate also shifted to larger sizes (1.0 μm to 1.8–3.2 μm stages). Mass concentrations of numerous soil tracer species (e.g., Si, Fe) were strongly enhanced in samples influenced by wildfires, especially in the sub-micrometer range. Airborne cloud water data confirm that soil species were associated with fire plumes transported south along the coast. In the absence of biomass burning, cloud condensation nuclei (CCN) composition is dominated by nss sulfate and ammonium, and the water-soluble organic fraction is dominated by methanesulfonate, whereas for the samples influenced by wildfires, ammonium becomes the dominant overall species, and oxalate is the most abundant organic species.

On the origin of the occasional spring nitrate peak in Greenland snow

Abstract. Ice core nitrate concentrations peak in the summer in both Greenland and Antarctica. Two nitrate concentration peaks in one annual layer have been observed some years in ice cores in Greenland from samples dating post-1900, with the additional nitrate peak occurring in the spring. The origin of the spring nitrate peak was hypothesized to be pollution transport from the mid-latitudes in the industrial era. We performed a case study on the origin of a spring nitrate peak in 2005 measured from a snowpit at Summit, Greenland, covering 3 years of snow accumulation. The effect of long-range transport of nitrate on this spring peak was excluded by using sulfate as a pollution tracer. The isotopic composition of nitrate (δ15N, δ18O and Δ17O) combined with photochemical calculations suggest that the occurrence of this spring peak is linked to a significantly weakened stratospheric ozone (O3) layer. The weakened O3 layer resulted in elevated UVB (ultraviolet-B) radiation on the snow surface, where the production of OH and NOx from the photolysis of their precursors was enhanced. Elevated NOx and OH concentrations resulted in enhanced nitrate production mainly through the NO2 + OH formation pathway, as indicated by decreases in δ18O and Δ17O of nitrate associated with the spring peak. We further examined the nitrate concentration record from a shallow ice core covering the period from 1772 to 2006 and found 19 years with double nitrate peaks after the 1950s. Out of these 19 years, 14 of the secondary nitrate peaks were accompanied by sulfate peaks, suggesting long-range transport of nitrate as their source. In the other 5 years, low springtime O3 column density was observed, suggesting enhanced local production of nitrate as their source. The results suggest that, in addition to direct transport of nitrate from polluted regions, enhanced local photochemistry can also lead to a spring nitrate peak. The enhanced local photochemistry is probably associated with the interannual variability of O3 column density in the Arctic, which leads to elevated surface UV radiation in some years. In this scenario, enhanced photochemistry caused increased local nitrate production under the condition of elevated local NOx abundance in the industrial era.

Constraints on climate forcing by sulphate aerosols from seasonal changes in Earth's spin

AbstractAngular momentum exchanges between atmosphere and solid Earth are strongly modulated by variations in global atmospheric circulation. Geodetically determined length-of-day (LOD) fluctuations provide an independent resource to investigate climate changes. Here, I evaluate the effects of volcanic and anthropogenic sulphate aerosols on Earth's rotational energy variations. The period analysed, 1980–2002, shows that the strongest seasonal LOD variations are related to sulphate peak concentrations from the El-Chichón 1982, and Pinatubo and Cerro Hudson 1991 volcanic eruptions. The Earth's rotational energy budget implies that radiative forcing alone cannot produce the observed LOD anomalies. Rather, the required amount of atmospheric kinetic energy can be explained only by a strong influence of sulphate aerosols on energy partitioning into the atmosphere, for example, as sulphate aerosols affect latent heat release and transport during condensation–evaporation–freezing cycles. Overall, the effects of sulphate aerosols on Earth's spin changes are faster than those produced by greenhouse gases.

The stability, sensitivity and response transients of ZnO, SnO2 and WO3 sensors under acetone, toluene and H2S environments

Chemoresistive H2S sensors using various oxide nanoparticles were prepared and heat-treated at 600°C in an effort to define halitosis in human breath. WO3, ZnO, and SnO2 were tested as sensing materials, among which WO3 showed the highest stability to H2S. XPS analysis showed a metal sulfate peak on the surface of ZnO and SnO2, which causes a recovery problem after 2ppm H2S exposure. On the contrary, the WO3 sensor showed a stable signal in long-term operation in the presence of H2S gas.WO3 gas sensors decorated with various catalytic metals were fabricated to investigate their sensing properties in the 0.2–5ppm H2S range with 80% relative humidity (RH). A 0.03wt% Au-doped WO3 sensor exhibited excellent H2S sensitivity (Rair/Rgas=12.40at 2ppm) toward H2S, whereas pure WO3 showed a sensitivity of 4.85 with negligible interference from the volatile organic compounds (VOCs).

The Oxidation State of Sulfur on the Air Side Surface of Soda-Lime Float Glass as Determined by X-Ray Absorption near Edge Structure Spectra

Three ways were used to prepare sulfide in soda-lime-silicate glass samples, i.e., glass heat-treated in N2/H2 (90/10 volume ratio), doped with different Carbon/Sulfur in mol ratio, as well as different sulfur source respectively. The oxidation state of sulfur on the air side surface of float glass heat-treated in N2/H2 and the bulk samples of the other two were determined by X-ray absorption near edge structure spectra (XANES). It was observed on the air side that: 1) A weak pre-edge exhibits at 2466.8eV which appears only with sulfite at high temperature and related to sulfur source; 2) A typical peak of sulfate at 2482.4eV decreases with increasing the temperature and heating duration. 3) Two peaks associated with sulfide, a broader one at about 2476.3eV and a sharper one with an accurate position at 2473.7eV. The S2- content at air side of glass heat-treated at 750 is higher than that of the glass treated at other temperatures, and increases with the heating duration, which is just the reverse at 1050, because the S2- volatilizes to the atmosphere easily at higher temperature. In addition, the content of S2- increases with increasing C/S ratio. The local environment of S2- in the glass with Na2S is different from that of with FeS, as indicated by the broader resonance. The spectra indicate that the glass heat-treated in N2/H2 (90/10), doped with different C/S ratio and with Na2S have the same sulfites or sulfites.

Perturbation of the endothelial glycocalyx in post cardiac arrest syndrome

BackgroundThe prognosis of immediate survivors of cardiac arrest remains poor, as the majority of these patients develops an inflammatory disorder known as the post-cardiac arrest syndrome (PCAS). Recently, the endothelial glycocalyx has been shown to be a key modulator of vascular permeability and inflammation, but its role in PCAS remains unknown. MethodsPlasma levels of the glycocalyx components syndecan-1, heparan sulfate and hyaluronic acid were measured in 25 patients after immediate survival of cardiac arrest during different phases of PCAS. Twelve hemodynamically stable patients with acute coronary syndrome served as controls. ResultsCardiac arrest resulted in a significant increase in syndecan-1, heparan sulfate and hyaluronic acid levels compared to controls, indicating a shedding of the endothelial glycocalyx as a pathophysiological component of the post cardiac arrest syndrome. The time course differed between the individual glycocalyx components, with a higher increase of syndecan-1 in the early phase of PCAS (2.8-fold increase vs. controls) and a later peak of heparan sulfate (1.7-fold increase) and hyaluronic acid (2-fold increase) in the intermediate phase. Only the plasma levels of syndecan-1 correlated positively with the duration of CPR and negatively with the glycocalyx-protective protease inhibitor antithrombin III. Plasma levels of both syndecan-1 and heparan sulfate were higher in eventual non-survivors than in survivors of cardiac arrest. ConclusionOur data for the first time demonstrates a perturbation of the endothelial glycocalyx in immediate survivors of cardiac arrest and indicate a potential important role of this endothelial surface layer in the development of post-cardiac arrest syndrome.

Development and Validation of an HPLC Assay For Dual Detection of Gentamicin Sulfate and Leucine From a Novel Dry Powder For Inhalation

TM ; Dual de- tection; Dry powder; Inhalation Abstract A stability indicating HPLC assay with UV detection was developed for the simultaneous quantification of Gentamicin Sulfate and L-leucine from NanoGENT™ dry powder for inhalation. In order to support the development of the NanoGENT™ (dry powder Gentamicin Sulfate for inhalation) the assay was created to allow simultaneous detection of the active pharmaceutical ingredient (Gentamicin Sulfate) and the primary excipient (L-leucine). In order to quantify Gentamicin Sulfate by UV detection derivatization was required. The assay resolved L-leucine from all four Gentamicin Sulfate peaks and all four Gentamicin Sulfate peaks from each other with a reversed phase isocratic assay. Once developed the assay was validated in accordance with regulatory guidance in order to support regulatory approval of the NanoGENT™ dry powder inhalation formulation. The validation data indicated that the dual detection assay meets or exceeded all criteria for use as a stability indicating assay. Orally inhaled therapeutics are a mainstay in the treatment of asthma and COPD and is growing rapidly in the treatment of other pulmonary and systemic indications. The growth of orally inhaled therapeutics to treat atypical indications has broadened beyond vaccines and insulin to include biological threats. This growth has exacerbated the fact that there are currently a minimal number of GRAS excipients for inhalation delivery (1). Further, the excipients that are considered GRAS do not span the range of physical chemical properties that are often required for formulations of a material for delivery to the lungs.

Crystal Structure of the E2 Domain of Amyloid Precursor Protein-like Protein 1 in Complex with Sucrose Octasulfate

Missense mutations in the amyloid precursor protein (APP) gene can cause familial Alzheimer disease. It is thought that APP and APP-like proteins (APLPs) may play a role in adhesion and signal transduction because their ectodomains interact with components of the extracellular matrix. Heparin binding induces dimerization of APP and APLPs. To help explain how these proteins interact with heparin, we have determined the crystal structure of the E2 domain of APLP1 in complex with sucrose octasulfate (SOS). A total of three SOS molecules are bound to the E2 dimer. Two SOSs are bound inside a narrow intersubdomain groove, and the third SOS is bound near the two-fold axis of the protein. Mutational analyses show that most residues interacting with SOS also contribute to heparin binding, although in varying degrees; a deep pocket, defined by His-376, Lys-422, and Arg-429, and an interfacial site between Lys-314 and its symmetry mate are most important in the binding of the negatively charged polysaccharide. Comparison with a lower resolution APP structure shows that all key heparin binding residues are conserved and identically positioned, suggesting that APLP1 and APP may bind heparin similarly. In transfected HEK-293 cells, mutating residues responsible for heparin binding causes little change in the proteolysis of APP by the secretases. However, mutating a pair of conserved basic residues (equivalent to Arg-414 and Arg-415 of APLP1) immediately adjacent to the heparin binding site affects both the maturation and the processing of APP.

Characterization of the sources and processes of organic and inorganic aerosols in New York city with a high-resolution time-of-flight aerosol mass apectrometer

Abstract. Submicron aerosol particles (PM1) were measured in-situ using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer during the summer 2009 Field Intensive Study at Queens College in New York, NY. Organic aerosol (OA) and sulfate are the two dominant species, accounting for 54% and 24%, respectively, of the total PM1 mass. The average mass-based size distribution of OA presents a small mode peaking at ~150 nm (Dva) and an accumulation mode (~550 nm) that is internally mixed with sulfate, nitrate, and ammonium. The diurnal cycles of both sulfate and OA peak between 01:00–02:00 p.m. EST due to photochemical production. The average (±σ) oxygen-to-carbon (O/C), hydrogen-to-carbon (H/C), and nitrogen-to-carbon (N/C) ratios of OA in NYC are 0.36 (±0.09), 1.49 (±0.08), and 0.012 (±0.005), respectively, corresponding to an average organic mass-to-carbon (OM/OC) ratio of 1.62 (±0.11). Positive matrix factorization (PMF) of the high resolution mass spectra identified two primary OA (POA) sources, traffic and cooking, and three secondary OA (SOA) components including a highly oxidized, regional low-volatility oxygenated OA (LV-OOA; O/C = 0.63), a less oxidized, semi-volatile SV-OOA (O/C = 0.38) and a unique nitrogen-enriched OA (NOA; N/C = 0.053) characterized with prominent CxH2x + 2N+ peaks likely from amino compounds. Our results indicate that cooking and traffic are two distinct and mass-equivalent POA sources in NYC, together contributing ~30% of the total OA mass during this study. The OA composition is dominated by secondary species, especially during high PM events. SV-OOA and LV-OOA on average account for 34% and 30%, respectively, of the total OA mass. The chemical evolution of SOA in NYC appears to progress with a continuous oxidation from SV-OOA to LV-OOA, which is further supported by a gradual increase of O/C ratio and a simultaneous decrease of H/C ratio in total OOA. Detailed analysis of NOA (5.8% of OA) presents evidence that organic nitrogen species such as amines might have played an important role in the atmospheric processing of OA in NYC, likely involving both acid-base chemistry and photochemistry. In addition, analysis of air mass trajectories and satellite imagery of aerosol optical depth (AOD) indicates that the high potential source regions of secondary sulfate and aged OA are mainly located in regions to the west and southwest of the city.

36 CHANGES IN PLASMA CONCENTRATIONS OF PROGESTERONE AND ESTROGENS DURING GESTATION IN COWS WITH STILLBORN SOMATIC CELL CLONED CALVES

Cloning of mammals by nuclear transfer frequently results in gestational or neonatal failure with a variety of abnormalities that are likely caused by inappropriate epigenetic reprogramming. Early diagnosis of fetal abnormality is important for efficient production of cloned animals. Sex steroids are produced in the bovine placenta and their levels in the blood might be useful as a measure of fetal well being, as they are in humans. The objective of this study was to investigate whether changes in peripheral concentrations of progesterone and estrogens reflect fetal conditions. Donor cells for nuclear transfer were obtained from subculture of cumulus cells retrieved from ovarian follicles of a Japanese Black cow. Recipient oocytes were derived from ovaries obtained at an abattoir and matured in vitro. Metaphase II oocytes were enucleated and each fused with a donor cell by DC pulses. Nuclear transferred oocytes were activated and cultured for 7 days. Embryos developed to the blastocyst stage were transferred into the uterine horn ipsilateral to the ovary bearing the CL of 29 multiparous Japanese Black and Holstein crossbred cows at 7 to 8 days after the day of standing oestrus (Day 0). Blood was collected at regular intervals from Day 40 until parturition. Plasma progesterone, estrone, oestradiol-17β, and estrone sulfate were measured by RIA in 4 recipient cows. 2 vaginally delivered healthy calves weighed 35 and 36 kg on days 278 and 280, respectively. The other 2 delivered stillborn calves weighed 42 and 31 kg by Caesarean section on days 267 and 287, respectively. Steroid profiles were compared with each other and with those in a cow made pregnant by embryo transfer. Statistical differences at stages of gestation were analysed with repeated-measures ANOVA. Stillborn calves were subjected to necropsy and histopathological analysis. Significant differences in steroid levels were observed individually and temporarily. In the cow bearing the former stillborn, progesterone and oestradiol-17β concentrations tended to be lower during mid and late gestation, respectively. Large offspring syndrome, ventricular septal defect, pulmonary oedema, hepatic fibrosis, and placental dysplasia were found in the calf by necropsy and histopathological analysis. In the cow bearing the second stillborn, plasma progesterone concentrations were temporarily increased from days 220 to 230 and reached a peak of 16 ng mL–1, which was approximately 3 times as high as before (5.0 ± 0.9; mean ± s.d.), then followed by a similar transient increase in estrogens during days 240 and 250 (170 pg mL–1, 16 pg mL–1, and 21 ng mL–1 at peak of estrone, oestradiol-17β, and estrone sulfate, respectively). Thereafter, oestrogen concentrations stayed low until parturition. As internal organs of the stillborn calf were severely autolysed with polyhydramnios at birth, the fetus might have been dead around Day 250. These results imply that changes in peripheral steroid concentrations in some cases reflect fetal condition.

Nighttime enhancement of PM2.5 nitrate in ammonia-poor atmospheric conditions in Beijing and Shanghai: Plausible contributions of heterogeneous hydrolysis of N2O5 and HNO3 partitioning

Abstract In our previous study, exceptionally high concentrations of nitrate (24-h average of up to 42 μg m −3 ) were found in ammonium-deficient samples of PM 2.5 during summer 2005 near Beijing and Shanghai. The formation of such high levels of nitrate in ammonium-poor PM 2.5 cannot be explained by the homogeneous gas-phase reaction mechanism involving ammonia and nitric acid. Hence, we postulated that high levels of nitrate were formed via the heterogeneous hydrolysis of N 2 O 5. In the present study, we further examine the formation of nitrate using hourly measurements of sulfate and nitrate and a multiphase chemistry box model (RACM + CAPRAM). Enhancements of nitrate and the NO 3 − /NO y ratio were observed at nighttime when sulfate and NO y concentrations remained relatively stable. These enhancements and a concomitant shift in the size of the nitrate concentration peak to a bin larger than that of sulfate peak suggested the possibility that nitrate was formed on pre-existing sulfate aerosol surfaces. A multiphase chemistry box model was set up to simulate the observed enhancement of nitrate at nighttime. The model was constrained by the measured concentrations of sulfate, nitrate, ammonium and O 3 and NO y , and estimated acidity and aerosol water content using a thermodynamic model (AIM). Assuming an NO 2 /NO y ratio in the range of 0.2–0.4 for Beijing and 0.4–0.6 for Shanghai, the model results suggest that the heterogeneous hydrolysis of N 2 O 5 contributed 50%–100% of the nighttime enhancement of nitrate concentration. Sensitivity analysis shows that increasing the aerosol water content significantly favors the partitioning of nitrate in the aerosol phase that was formed via the hydrolysis of N 2 O 5 at nighttime.

Sulfate Spikes in the Deep Layers of EPICA-Dome C Ice Core: Evidence of Glaciological Artifacts

A detailed ionic component record was performed on EPICA Dome C ice core (East Antarctica) to a depth of 3190 m using Ion Chromatography and Fast Ion Chromatography (FIC). At depths greater than 2800 m, the sulfate profile shows intense, sharp spikes which are not expected due to the smoothing of sulfate peaks by diffusion processes. Moreover, these spikes show an "anomalous" chemical composition (e.g., unusually low acidity, high Mg(2+) concentration and high Mg(2+)/Ca(2+) ratio). These peaks and the surrounding layers also exhibit good Mg(2+) vs SO(4)(2-) and Cl(-) vs Na(+) correlations through both glacial and interglacial periods. Furthermore, the high-resolution analysis of two horizontally contiguous ice sections showed that some fraction of the impurities are characterized by a heterogeneous distribution. Altogether, these results suggest the occurrence of long-term postdepositional processes involving a rearrangement of impurities via migration in the vein network, characterized by sulfuric acidity and leading to the formation of soluble particles of magnesium sulfate salts, along with ionic association of ions in the liquid films along boundaries. This evidence should be taken into consideration when inferring information on for rapid climatic and environmental changes from ice core chemical records at great depths. At Dome C, the depth threshold was found to be 2800 m.

Raman Spectroscopic Investigation of Peptide—Glycosaminoglycan Interactions

Protein-glycosaminoglycan (GAG) interactions play a central role in tissue engineering and drug delivery. A rapid and efficacious method for screening these interactions is essential. Raman spectroscopy was used to identify chemical interactions and conformational changes occurring upon binding between a synthetic peptide (QRRFMQYSARRF) and two glycosaminoglycans (GAGs), heparin and chondroitin 6-sulfate (C6S). The results identify three main chemical groups that are involved in the binding of the synthetic peptide with heparin and C6S. Tyrosine formed hydrogen bonds with the GAGs via its hydroxyl group. The amide I band demonstrated substantial shifts in Raman wavenumbers when bound to heparin and C6S (Deltaomega=-10.2+/-0.7 cm(-1) and Deltaomega=-11.9+/-0.3 cm(-1), respectively), suggesting that the peptide underwent planar conformational changes after binding occurred. Upon binding to the peptide, the sulfate peak of heparin displayed a substantially greater shift in the Raman wavenumber (-7.5+/-0.5 cm(-1)) than that of C6S (-2.6+/-0.5 cm(-1)). The greater amide I and sulfate band shifts seen during peptide-heparin interactions are indicative of a stronger association compared to that between the peptide and C6S. This observation was confirmed by capillary electrophoresis, which demonstrated a lower dissociation constant (KD) between the peptide and heparin (KD of 19.2+/-3.3 microM) than between the peptide and C6S (26.7+/-2.5 microM). We conclude that the shift in the Raman wavenumbers of amide I and sulfate groups can be used for high-throughput screening of interaction affinities between libraries of peptides and GAGs.

The oxidation state of sulfur in synthetic and natural glasses determined by X-ray absorption spectroscopy

Sulfur K-edge X-ray absorption near edge structure (XANES) spectra were recorded for experimental glasses of various compositions prepared at different oxygen fugacities ( fO 2) in one-atmosphere gas-mixing experiments at 1400 °C. This sample preparation method only results in measurable S concentrations under either relatively reduced (log fO 2 < −9) or oxidised (log fO 2 > −2) conditions. The XANES spectra of the reduced samples are characterised by an absorption edge crest at 2476.4 eV, typical of S 2−. In addition, spectra of Fe-bearing compositions exhibit a pronounced absorption edge shoulder. Spectra for all the Fe-free samples are essentially identical, as are the spectra for the Fe-bearing compositions, despite significant compositional variability within each group. The presence of a sulfide phase, such as might exsolve on cooling, can be inferred from a pre-edge feature at 2470.5 eV. The XANES spectra of the oxidised samples are characterised by an intense transition at 2482.1 eV, typical of the sulfate anion SO 4 2−. Sulfite (SO 3 2−) has negligible solubility in silicate melts at low pressures. The previous identification of sulfite species in natural glass samples is attributed to an artefact of the analysis (photoreduction of S 6+). S 4+ does, however, occur unambiguously with S 6+ in Fe-free and Fe-poor compositions prepared in equilibrium with CaSO 4 at 4–16 kbar, and when buffered with Re/ReO 2 at 10 kbar. Solubility of S 4+ thus requires partial pressures of SO 2 considerably in excess of 1 bar. A number of experiments were undertaken in an attempt to access intermediate fO 2s more applicable to terrestrial volcanism. Although these were largely unsuccessful, S 2− and S 6+ were found to coexist in some samples that were not in equilibrium with the imposed fO 2. The XANES spectra of natural olivine-hosted melt inclusions and submarine glasses representative of basalts at, or close to, sulfide saturation show mainly dissolved S 2−, but with minor sulfate, and additionally a peak at 2469.5 eV, which, although presumably due to immiscible sulfide, is 1 eV lower than that typical of FeS. These sulfate and sulfide-related peaks disappear with homogenisation of the inclusions by heating to 1200 °C followed by rapid quenching, suggesting that both these features are a result of cooling under natural conditions. The presence of small amounts of sulfate in otherwise reduced basaltic magmas may be explained by the electron exchange reaction: S 2− + 8Fe 3+ = S 6+ + 8Fe 2+, which is expected to proceed strongly to the right with decreasing temperature. This reaction would explain why S 2− and S 6+ are frequently found together despite the very limited fO 2 range over which they are thermodynamically predicted to coexist. The S XANES spectra of water-rich, highly oxidised, basaltic inclusions hosted in olivine from Etna and Stromboli confirm that nearly all S is dissolved as sulfate, explaining their relatively high S contents.

A novel method for determination of low molecular weight dicarboxylic acids in background atmospheric aerosol using ion chromatography

This paper describes a novel gradient elution ion chromatographic method using a Dionex AS11 system for the determination of low molecular weight dicarboxylic acids (low- M w DCAs) in background atmospheric aerosol. Interference with the oxalic acid peak from sulfate in background PM 2.5 aerosol, 15.8 times the oxalic acid concentration, was remedied by removing sulfate using a barium cartridge, whilst interference with the malonic acid peak from carbonate was reduced by using a carbonate removal device. An alternative remedy to sulfate interference was use of an AS14 system using isocratic eluent, and this produced good resolution of oxalic acid from a high sulfate peak. In both the AS11 and the AS14 system, linear correlation coefficients were at all times >0.9990 with excellent linear range, the recoveries ranged from 92.8 to 106%, with relative standard deviation of 3.67–6.30%, whilst method detection limits (MDLs) ranged from 0.36 μg L −1 for malic acid to 3.87 μg L −1 for maleic acid. These data indicate that the analytical methods developed herein produce excellent separation efficiency and good determination of low- M w DCAs with satisfactory accuracy, recoveries, and MDLs. Samples left at room temperature (20 °C) for 300 min in a simulation of the ‘waiting time’ involved in the proposed IC analysis decayed to between 86% (oxalic acid) and 39% (succinic and malonic acids) of their original concentration, whilst at 4 °C concentrations remained at 96–101% of original, indicating that maintaining samples at a low temperature prior to injection into the IC analyzer is vital for obtaining accurate results when analyzing low- M w DCAs. Oxalic acid was found to be the most prevalent low- M w DCA in background aerosol, comprising 57% of the total low- M w DCAs and 0.959% of the PM 2.5 aerosol mass, followed by succinic acid and malonic acid.

Methane and sulfate profiles within the subsurface of a tidal flat are reflected by the distribution of sulfate-reducing bacteria and methanogenic archaea

The anoxic layers of marine sediments are dominated by sulfate reduction and methanogenesis as the main terminal oxidation processes. The aim of this study was to analyze the vertical succession of microbial populations involved in these processes along the first 4.5 m of a tidal-flat sediment. Therefore, a quantitative PCR approach was applied using primers targeting the domains of Bacteria and Archaea, and key functional genes for sulfate reduction (dsrA) and methanogenesis (mcrA). The sampling site was characterized by an unusual sulfate peak at 250 cm depth resulting in separate sulfate-methane transition zones. Methane and sulfate profiles were diametrically opposed, with a methane maximum in the sulfate-depleted zone showing high numbers of archaea and methanogens. The methane-sulfate interfaces harbored elevated numbers of sulfate reducers, and revealed a slight increase in mcrA and archaeal 16S rRNA genes, suggesting sulfate-dependent anaerobic oxidation of methane. A diversity analysis of both functional genes by PCR-denaturing gradient gel electrophoresis revealed a vertical succession of subpopulations that were governed by geochemical and sedimentologic conditions. Along the upper 200 cm, sulfate-reducing populations appeared quite uniform and were dominated by the Deltaproteobacteria. In the layers beneath, an apparent increase in diversity and a shift to the Firmicutes as the predominant group was observed.

The evolution of the global aerosol system in a transient climate simulation from 1860 to 2100

Abstract. The evolution of the global aerosol system from 1860 to 2100 is investigated through a transient atmosphere-ocean General Circulation Model climate simulation with interactively coupled atmospheric aerosol and oceanic biogeochemistry modules. The microphysical aerosol module HAM incorporates the major global aerosol cycles with prognostic treatment of their composition, size distribution, and mixing state. Based on an SRES A1B emission scenario, the global mean sulfate burden is projected to peak in 2020 while black carbon and particulate organic matter show a lagged peak around 2070. From present day to future conditions the anthropogenic aerosol burden shifts generally from the northern high-latitudes to the developing low-latitude source regions with impacts on regional climate. Atmospheric residence- and aging-times show significant alterations under varying climatic and pollution conditions. Concurrently, the aerosol mixing state changes with an increasing aerosol mass fraction residing in the internally mixed accumulation mode. The associated increase in black carbon causes a more than threefold increase of its co-single scattering albedo from 1860 to 2100. Mid-visible aerosol optical depth increases from pre-industrial times, predominantly from the aerosol fine fraction, peaks at 0.26 around the sulfate peak in 2020 and maintains a high level thereafter, due to the continuing increase in carbonaceous aerosols. The global mean anthropogenic top of the atmosphere clear-sky short-wave direct aerosol radiative perturbation intensifies to −1.1 W m−2 around 2020 and weakens after 2050 to −0.6 W m−2, owing to an increase in atmospheric absorption. The demonstrated modifications in the aerosol residence- and aging-times, the microphysical state, and radiative properties challenge simplistic approaches to estimate the aerosol radiative effects from emission projections.