Sulfate Molar Ratio Research Articles

Seasonal and short-term variability in dimethyl sulfide, sulfur dioxide and biogenic sulfur and sea salt aerosol particles in the arctic marine boundary layer during summer and autumn

The International Arctic Ocean Expedition (IAOE), lasting from August to mid-October 1991, provided a unique opportunity to characterize and quantify relationships within the natural sulfur cycle in the marine boundary layer under conditions of limited anthropogenic influence. Concentrations of dimethyl sulfide, sulfur dioxide, and submicrometer aerosol concentrations of methane sulfonate, non-sea-salt sulfate, ammonium and elemental carbon ranged from 17 to 0.05 nmol m3 (380–1 ppt(v)), 1.7–0.04 nmol m3 (38–0.9 ppt(v)), 1.4–0.002 nmol m-3 (31–0.05 ppt(v), 6.9–0.03 nmol m-3 (155–0.7 ppt(v)), 3.9–0.03 nmol m-3 (90–0.7 ppt(v)) and 0.51–0.009 nmol m-3 (11–0.2 ppt(v)), respectively. Observations showed a seasonal variation of concentrations with highest values for all the marine biogenic sulfur gas-aerosol parametres along the ice edge zone in August and lowest values over the pack ice in late September On average concentrations fell with a decline rate of about 20–40% per week. A similar seasonal change was also reflected in particulate ammonium. This therefore indicates links between the different sulfur compounds as well as between the biogenic sulfur and nitrogen cycles. Concentrations over the pack ice region were generally lower than over the open waters at the ice edge with an estimated net loss rate of roughly 35% per day of transport over the pack ice. Contrary to earlier marine sulfur studies performed outside the Arctic region, a constant methane sulfonate to non-sea-salt sulfate molar ratio was found in the submicrometer size fraction for samples with a minimal influence from fog and anthropogenic sources. This ratio had a value of 0.22 in spite of large seasonal changes in temperature and concentrations of methane sulfonate and non-sea-salt sulfate. Thus we conclude that the sum of the proceses controlling the measured particle properties do not exhibit a net temperature dependence. The one to one molar ratio of ammonium to non-sea-salt sulfate indicated a partly neutralised ammoniated sulfate aerosol. This was further verified by single particle analysis. Measurements of non-sea-salt sulfate and ammonium revealed a bimodal size distribution with about 70% of their mass found in the submicrometer size fraction. Methane sulfonate was mainly associated with submicrometer particles, with less than 8% of the mass observed in the largest particles. We have also shown that the interchange of air between the surface mixed layer and clouds, caused by atmospheric wave motions, dominated the short time variations in atmospheric DMS and submicrometer aerosol concentrations. This interchange will have a strong influence on the chemical and physical processes that control the properties of the aerosol, and deserves more attention in future work.

Variations in the methanesulfonate to sulfate molar ratio in submicrometer marine aerosol particles over the south Pacific Ocean

Seawater concentrations of dimethylsulfide (DMS) and atmospheric concentrations of DMS, sulfur dioxide, methanesulfonate (MSA), and non‐sea‐salt (nss) sulfate were measured over the eastern Pacific Ocean between 105° and 110°W from 20°N to 60°S during February and March 1989. Although the samples collected in the southern hemisphere appear to be of marine origin, no significant correlation was found between the latitudinal distributions of DMS, SO2, MSA, and nss SO4=. However, an inverse correlation (r2 = 0.87) was found between atmospheric temperature and the MSA to nss SO4= molar ratio in submicrometer aerosol particles with a decrease in temperature corresponding to an increase in the molar ratio. Although this trend is consistent with laboratory results indicating the favored production of MSA at lower temperatures, it is contrary to southern hemisphere baseline station data. This suggests either a decrease in the supply of DMS relative to nonmarine sources of nss SO4= at the baseline stations in winter or additional mechanisms that affect the relative production of MSA and nss SO4=.

Equilibria of the marine multiphase ammonia system

A lack of empirical data has made it difficult to ascertain whether ammonia is in equilibrium between the oceanic, atmospheric gas and atmospheric particle phases in the remote marine environment. Reported here are simultaneous measurements of the saturation concentration of ammonia relative to ammonia concentrations in ocean surface waters; total seawater ammonia; atmospheric gas phase ammonia; and atmospheric particulate-phase ammonium, non-seasalt sulfate, methanesulfonate, and nitrate. Sampling was performed in May of 1987 in the northeast Pacific Ocean environment and in April and May of 1988 in the central Pacific Ocean environment. These measurements were used to determine the degree to which ammonia approached equilibrium between the oceanic and atmospheric gas and aerosol particle phases. The experimental atmospheric gas phase ammonia concentrations were compared with calculated equilibrium concentrations assuming a Henry's law type of partitioning between the gas and condensed phases. Characteristic times of the processes controlling the fate of ammonia in the marine environment also were compared. The measured atmospheric gas phase and oceanic concentrations of ammonia indicate that ammonia is not in a Henry's law equilibrium across the air/sea interface. This disequilibrium is a result of the long air/sea exchange equilibration time relative to the lifetime of ammonia in the atmosphere. Comparison of the calculated equilibrium gas phase ammonia concentrations with the measured gas phase ammonia concentrations shows that attainment of equilibrium between the atmospheric gas and particle phases is a strong function of the chemical composition of the aerosol particles. The data suggest that fully neutralized aerosol particles are not in Henry's law equilibrium with the gas phase while equilibrium is observed for particles with an average ammonium to non-seasalt sulfate molar ratio less than 1.8.

Spontaneous precipitation of barium sulfate in aqueous solution

The formation of barium sulfate scale in oil wells and in several industrial processes in which water supersaturated with respect to this salt is used, is often a serious cause of energy losses. The spontaneous precipitation in aqueous solutions containing relatively high barium and sulfate concentrations was investigated in the present work. In our experiments the supersaturation of the solutions was chosen so that an induction period preceded the onset of precipitation. In all cases the induction time was found to be inversely proportional to the solution supersaturation and the rates of the subsequent precipitation were higher the higher the solution supersaturation. The stability domain of the barium sulfate system was not affected by the barium: sulfate molar ratio which ranged from 0.01to ca. 100. The dependence of the induction time on the initial barium concentration was linear and irrespective of the molar ratio of barium: sulfate the same slope was obtained. The slope may be related to the size of the critical nucleus. The kinetic data obtained suggested a surface-controlled, polynuclear mechanism. On the basis of this model a value of 86 mJ m–2 was obtained for the surface energy of the precipitaing solid phase.

North Pacific marine background aerosol: Average ammonium to sulfate molar ratio equals 1

Measurements of the chemical composition of marine aerosol were made at a location on the north‐west coast of the continental United States. The average concentration of sulfate ion in submicrometric aerosol particles was 0.4 μg m−3. The average ammonium ion to sulfate ion molar ratio was 1.0 and was nearly the same as the ratio of 1.1 for concurrently collected rain samples. There was a large variability in these parameters on the 3‐hour basis of the measurement method.

Factors affecting surface expression of glycolipids: influence of lipid environment and ceramide composition on antibody recognition of cerebroside sulfate in liposomes.

The reactivity of the acidic glycolipid cerebroside sulfate (CBS) with antibody was studied as a function of its lipid environment in vesicles and of its ceramide composition. The lipid environment was varied by using phosphatidylcholine of varying chain length with cholesterol in a phosphatidylcholine:cholesterol:cerebroside sulfate molar ratio to glycolipid of 1:0.75:0.1. The ceramide structure of CBS was varied by using synthetic forms containing palmitic acid, lignoceric acid, or the corresponding alpha-hydroxy fatty acids. Reactivity with antibody was determined by measuring complement-mediated lysis of the vesicles containing a spin-label marker, tempocholine chloride. The data were analyzed by a theoretical model which gives relative values for the dissociation constant and concentration of antibodies within the antiserum which are able to bind to the glycolipid. If the phosphatidylcholine chain length was increased, increasing the bilayer thickness, only a small population of high-affinity antibodies were able to bind to cerebroside sulfate, suggesting decreased surface exposure of the glycosyl head group. A larger population of lower affinity antibodies were able to bind to it in a shorter chain length phosphatidylcholine environment. However, if the chain length of the cerebroside sulfate was increased, it could be recognized by more antibodies of lower affinity than the short chain length form, suggesting that an increase in chain length of the glycolipid increased surface exposure. Hydroxylation of the fatty acid inhibited antibody binding; only a smaller population of higher affinity antibodies was able to bind to the hydroxy fatty acid forms.(ABSTRACT TRUNCATED AT 250 WORDS)

In-situ, rapid response measurement of H 2SO 4/(NH 4) 2SO 4 aerosols in urban Houston: A comparison with rural Virginia

We report measurements taken in Houston, Texas of the chemical composition and degree of hydration of haze particles and compare these results with previously reported measurements taken in rural Virginia. Our in-situ, real time measurements are based on detecting changes in particle light scattering extinction with changes in relative humidity and air temperature. With these methods we can determine fine particle mass and sulfate mass concentrations, and sulfate to ammonium ion molar ratio. In Houston, fine particle sulfate averaged 42 % of fine particle mass and the composition in terms of ammonium to sulfate molar ratio ranged from 0.5 to 2 with strong diurnal variation. The particles were most acid during the period 1500 to 2000 and neutral during 0200 to 0900. About 1 3 of the time the particles were droplets supersaturated in terms of salt content. In Virginia, the particles were on average more acidic and contained more water than those in Houston, but the particles were never observed to be supersaturated solution droplets. The difference in the hygroscopic behavior of the particles at the two sites is consistent with differences in both particle chemistry and ambient relative humidity.

Chemical speciation of H 2S0 4—(NH 4) 2S0 4 particles using temperature and humidity controlled nephelometry

Measurment of the response of sulfate compounds in aerosol particles tp thermal decomposition at specific relative humidities providies semiquantitative chemical analysis for sulfate compounds and ammonium to sulfate molar ratio. Laborotory data are presented and discussed . Experiments at one Eastern U.S. site show ambient aerosol NH 4 +/SO 4 = between 0.5 and 2.0.

Characterization of the sulfated glycosaminoglycan on the surface and in the storage granules of rabbit platelets

Rabbit platelets were labeled in vivo with 35S for characterization of platelet sulfated glycosaminoglycan. When rabbit platelets were aggregated by ADP, sulfated proteoglycan was lost from the platelet surface although no release of granule contents occurred. The sulfated proteoglycan contained in the granules of platelets pretreated with ADP was subsequently released by treatment with thrombin. The 35S-labeled proteoglycan from both sources was isolated by gel filtration and the glycosaminoglycan portion of the proteoglycan was characterized as chondroitin 4-sulfate by examining the products of digestion with hyaluronidase, chondroitinase AC and ABS, and chondro-4- and 6-sulfatases; by identification of the hexosamine as N-acetylgalactosamine; by determination of a 1 : 1 : 1 molar ratio of N-acetylgalactosamine, uronic acid and inorganic sulfate; and by cetylpyridinium chloride cellulose chromatography. In these studies, the use of 35S-labeled proteoglycan made possible detection and quantification of much smaller amounts of material than would be possible with unlabeled material. Chondroitin 4-sulfate was the only sulfated glycosaminoglycan identified in the proteoglycan lost from the platelet surface during ADP-induced aggregation and in the proteoglycan released from the granules when the platelets were exposed to thrombin.

Ammonia in the human airways: neutralization of inspired acid sulfate aerosols.

In the human being, expired ammonia concentrations from 7 to 520 micrograms per cubic meter are controlled by the last airway segment traversed by the air, and such concentrations are higher in the mouth than nose. Inspired submicrometric sulfuric acid aerosol at a mass concentration of 600 +/- 100 micrograms per cubic meter was found to be an ammonium salt with an average ammonium to sulfate molar ratio of greater than or equal to 1, when sampled within 0.5 second after exhalation.

Isolation and Properties of a New Type of Sialopolysaccharide-Protein Complex from the Jelly Coat of Sea Urchin Eggs

Abstract A heteropolysaccharide-protein complex containing 70% sialic acid was isolated from the jelly coat of the eggs of the sea urchin, Pseudocentrotus depressus. The yield of this sialopolysaccharide-protein complex was 0.32% of the whole jelly powder. Purified by centrifugation and chromatography on Bio-Gel, the complex was found to be homogeneous by the criteria of electrophoresis and ultracentrifugation. Its sedimentation coefficient, s020 ,w, was 5.1, and the material carried a strong negative charge. The carbohydrate composition of the complex, expressed in percentages of the dry weight, was sialic acid, 70.0; fucose, 9.2; hexose, 3.7; and hexosamine, 2.4. Analyses for glycolic acid strongly indicated that all of the sialic acid occurred in glycolyl form. The molar ratio of sulfate to fucose was 1.42:1. The combined weights of monosaccharide, sulfate, and amino acid residues accounted for 96.0% of the complex weight. Thin layer chromatography of the sialopolysaccharide-protein complex after hydrolysis in mild acid showed five spots stained by Ehrlich's reagent. The major spot migrated as N-glycolylneuraminic acid. No indication of N-acetylneuraminic acid appeared. It is proposed that there are several new, undescribed neuraminic acids in the jelly coat, since the sialic acid yielded only 45% of the color in the reaction with thiobarbituric acid as compared with the direct Ehrlich assay and, moreover, no release of sialic acid from the complex by neuraminidase treatment was obtained.