Concentrations Of Dicarboxylic Acids Research Articles

Role of aerosol liquid water content on the production of dicarboxylic acids in the dust-laden air masses over the Arabian Sea: Implications for heterogeneous chemistry

Oxalic acid and the related organics are ubiquitous water-soluble constituents of ambient organic aerosols (OA). Their molecular distributions and relative abundances provide crucial insights on the secondary OA formation processes in the marine atmosphere and are important for understanding the cloud-aerosol interactions. Here, we measured the concentrations of dicarboxylic acids, pyruvic acid, ω-oxocarboxylic acids and α-dicarbonyls alongside aerosol chemical composition in the South Asian outflow to the Arabian Sea. Oxalic acid (C2) was the most abundant dicarboxylic acid followed by succinic (C4) and malonic (C3) acids; this distribution is typical of “less aged OA”. Oxalic acid levels correlated well with aerosol liquid water content (ALWC) and non-sea-salt (nss)-SO42− (a tracer of coal combustion influence), suggesting an important aqueous phase oxidation of successive higher homologs. This was inferred based on the prevailing inverse relationships between the relative abundances of oxalic acid in total aliphatic dicarboxylic acids and those of malonic, succinic, glutaric, adipic, and azelaic acids. Likewise, the concentrations of glyoxal (Gly: a major compound emitted from vehicular exhaust) and glyoxylic acid (ωC2) correlated strongly with C4, nss-Ca2+ (dust tracer) and elemental carbon (EC: a combustion tracer from biomass/fossil-fuels). These observations suggest gas/particle partitioning and subsequent aqueous phase oxidation of Gly to ωC2 and then elongation (oligomerization) to succinic acid associated with the mineral dust particles. This means relative abundances of anthropogenic SO42− in the dust-laden air masses govern the secondary OA formation over the Arabian Sea.

Effects of SLCO1B1 Genetic Variant on Metabolite Profile in Participants on Simvastatin Treatment.

Organic-anion-transporting polypeptide 1B1 (OATP1B1), encoded by the solute carrier organic anion transporter family member 1B1 gene (SLCO1B1), is highly expressed in the liver and transports several endogenous metabolites into the liver, including statins. Previous studies have not investigated the association of SLCO1B1 rs4149056 variant with the risk of type 2 diabetes (T2D) or determined the metabolite signature of the C allele of SLCO1B1 rs4149056 (SLCO1B1 rs4149056-C allele) in a large randomly selected population. SLCO1B1 rs4149056-C inhibits OATP1B1 transporter and is associated with increased levels of blood simvastatin concentrations. Our study is to first to show that SLCO1B1 rs4149056 variant is not significantly associated with the risk of T2D, suggesting that simvastatin has a direct effect on the risk of T2D. Additionally, we investigated the effects of SLCO1B1 rs4149056-C on plasma metabolite concentrations in 1373 participants on simvastatin treatment and in 1368 age- and body-mass index (BMI)-matched participants without any statin treatment. We found 31 novel metabolites significantly associated with SLCO1B1 rs4149056-C in the participants on simvastatin treatment and in the participants without statin treatment. Simvastatin decreased concentrations of dicarboxylic acids, such as docosadioate and dodecanedioate, that may increase beta- and peroxisomal oxidation and increased the turnover of cholesterol into bile acids, resulting in a decrease in steroidogenesis due to limited availability of cholesterol for steroid synthesis. Our findings suggest that simvastatin exerts its effects on the lowering of low-density lipoprotein (LDL) cholesterol concentrations through several distinct pathways in the carriers of SLCO1B1 rs4149056-C, including dicarboxylic acids, bile acids, steroids, and glycerophospholipids.

Molecular distributions of dicarboxylic acids, oxocarboxylic acids, and α-dicarbonyls in aerosols over Tuoji Island in the Bohai Sea: Effects of East Asian continental outflow

Field measurements of the concentrations of dicarboxylic acids and related compounds (oxocarboxylic acids and α-dicarbonyls) in PM2.5 were conducted on a background island (Tuoji Island, China) over the Bohai Sea to better understand the effects of pollution downwind of the East Asian continental outflow. Air mass backward trajectory calculations demonstrated that the distributions of dicarboxylic acids and related compounds at Tuoji Island depended strongly on the East Asian continental outflow and correlated with the hours spent by an air parcel in the polluted boundary layer. Based on the data analysis, the sampling period was categorized into heavy aerosol pollution periods (HAPPs) and light aerosol pollution periods (LAPPs). The average concentration of dicarboxylic acids and related compounds during HAPPs (1280 ± 503 ng m−3) was approximately seven times higher than that during LAPPs (189 ± 90.8 ng m−3). The order of the major species of dicarboxylic acids and related compounds, ranked by concentrations, was oxalic acid (C2) > glyoxylic acid (ωC2) > succinic acid (C4) > terephthalic acid (tPh) during HAPPs, and C2 > malonic acid (C3) > ωC2 > C4 during LAPPs. Results of positive matrix factorization (PMF) showed that secondary sources were the dominant source of dicarboxylic acids and related compounds, with contributions of 38% and 57% during HAPPs and LAPPs, respectively. Primary sources of biomass burning and plastic waste burning were also significant during HAPPs (contributions: 26% and 20%, respectively) and LAPPs (contributions: 18% and 12%, respectively). The concentration ratios of C3 to C4 (C3/C4), C2 to C4 (C2/C4), fumaric acid to maleic acid (F/M), phthalic acid to azelaic acid (Ph/C9), adipic acid to azelaic acid (C6/C9), and the positive correlations of Ph or tPh with dicarboxylic acids, and levoglucosan with dicarboxylic acids and related compounds further support the PMF results.

Clinical, Biochemical, and Molecular Analyses of Medium-Chain Acyl-CoA Dehydrogenase Deficiency in Chinese Patients.

ObjectiveMedium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare inherited metabolic disorder of fatty acid β-oxidation. The present study aimed to evaluate clinical and biochemical manifestations, and the mutation spectrum of this disorder in a large cohort of Chinese patients.MethodsA total of 24 patients were enrolled, and blood acylcarnitine and urinary organic acid levels were measured by tandem mass spectrometry and gas chromatography–mass spectrometry (GC–MS), respectively. Mutations in the ACADM gene were detected by Sanger or next-generation sequencing. Clinical progression, acylcarnitine spectra, and mutations were analyzed and described in detail.ResultsAmong the 24 patients, six cases were diagnosed because of disease onset with symptoms such as vomiting, diarrhea, convulsion, and hypoglycemia; 18 patients without symptoms were diagnosed by newborn screening (NBS). All patients who accepted treatment after diagnosis developed normal intelligence and physique. The concentrations of octanoylcarnitine, the octanoylcarnitine/decanoylcarnitine ratio, and the octanoylcarnitine/acetylcarnitine ratio in the blood and urinary dicarboxylic acid concentrations were consistently elevated. Blood biomarkers failed to decrease after treatment. DNA sequencing revealed seven known and 17 novel mutations in the ACADM gene of patients. Mutation p.T150Rfs∗4 was most frequent, followed by p.R31C, p.F103Y, p.I223T, p.G362E, and c.387+1delG.ConclusionDespite biochemical abnormalities, medium-chain acyl-CoA dehydrogenase deficiency showed relatively mild clinical phenotypes with low mortality and optimistic prognoses in China. NBS is crucial for early diagnosis, treatment, and prognosis.

Comparison of Atmospheric Monocarboxylic and Dicarboxylic Acids in Xi’ an, China, for Source Apportionment of Organic Aerosols

To investigate the characteristic distributions and formation mechanism of the polar organic components in atmospheric aerosols, atmospheric particulates were simultaneously sampled at three typical sites in urban(U), suburban(S) and rural(R) of Xi’an in summer and winter. Organic compositions, including dicarboxylic acids (DCAs), monocarboxylic acids (MCAs) were emphatically analyzed to explore the seasonal, spatial, and other variations. The results showed that total concentrations of DCAs and MCAs in winter were higher than those in summer. Athough the total content of DCAs in PM10 in winter is lower than that of MCAs, the total concentration of DCAs in PM2.5 and PM10 in summer are higher than that of MCAs. The total concentration of DCAs in PM2.5 in winter and summer were 1878 ± 1425 ng/m3 and 1334 ± 493 ng/m3, 1294 ± 943 ng/m3 and 728 ± 477 ng/m3 in PM10. While the total concentration of MCAs in PM2.5 in winter and summer were 1193 ± 1142 ng/m3 and 541 ± 367 ng/m3, 1659 ± 1162 ng/m3 and 492 ± 424 ng/m3 in PM10. Urban subtotal concentrations of DCAs from PM2.5 were the highest, and mass of organic acids in sunny days were significantly lower than the hazy days. Strong correlations were observed among the DCAs with ambient oxidants and precursors. Moreover, DCAs concentrations were vulnerable to the environmental factors, such as light intensity and relative humidity. Comparisons demonstrated that MCAs mainly comes from coal combustion, vehicle exhaust and other primary emissions, while the secondary photochemistry and liquid phase oxidation are the main sources of DCAs.

Activity of renal organic anion transporters in a model of ischemia and reperfusion injury in vitro

The aim of the work is to study the functional characteristics of SLC transporters of organic anions: OAT1 and OAT3 in normal conditions and in model ischemia/reperfusion injury.Materials and methods. The HEK293 cell line was used as a model for the study. Conditions of ischemia/reperfusion injury were created by the previously described method. The activity of the transporters was assessed by the capture of the marker substrate - fluorescein. The concentration of fluorescein was measured using a plate fluorimeter. The results were normalized by the amount of total protein.Results. In condition of ischemia/reperfusion injury, the activity of organic anion transporters decreased in comparison with the norm. The data obtained allow us to conclude that in conditions of ischemia/reperfusion injury, the concentration of dicarboxylic acids in the cell is low, which in turn can lead to a decrease activity of transporters.

Mixed-mode SPE followed by GC-MS analysis to determine water soluble organic compounds in aerosol and historical mortars affected by marine atmosphere: The case of Punta Begoña Galleries (Getxo, North of Spain)

This work describes the development of an analytical procedure for the determination of short chain dicarboxylic acids (C2-C10) both in aqueous and solid matrices such as aerosols and mortars. The developed and validated methodology was based on the preconcentration of compounds by means of mixed-mode solid phase extraction and gas chromatography-mass spectrometry, regardless the analyzed samples. In the case of solid samples, a prior extraction of target compounds using ultrasonic probe-assisted solid-liquid extraction was required. In general terms, the developed procedure rendered good results in terms of accuracy (apparent recoveries in the range 90–130% and 86–98% for marine aerosol and mortar samples, respectively) and repeatability (%RSD < 25%) except for those compounds interacting more strongly with the solid matrix and being more reactive. The method was applied to detect dicarboxylic acids in marine aerosol water samples and in mortars of a 20th century historical building (Punta Begoña Galleries, Getxo) located in a coastal environment (Biscay Gulf, Basque Country, Northern Spain) with industrial activity. According to the results, harbor activities may have effect on the concentrations of dicarboxylic acids found in both matrices since the façade of the building exposed to the industrial harbor (southwest orientation) appears to be more contaminated than the one oriented to the northwest.

Seasonal Variations in PM10 and Associated Chemical Species in Jiuxian Mountain in Fujian Province

PM10 samples were collected at the top of Jiuxian Mountain in Fujian Province from March 2011 to January 2012 and were analyzed for inorganic water-soluble ions and dicarboxylic acids to investigate their seasonal variations and sources. The results showed that PM10 and its associated species exhibited much higher levels in the spring than those in other seasons but the total contribution of the nine species of dicarboxylic acids to PM10 (0.51%±0.41%) was significantly lower than that of the water-soluble ions (18.07%±8.73%). The water-soluble ions were characterized by the highest concentrations of SO42- and NO3-, followed by Na+ and NH4+. Significant positive correlations were observed between cation and anion equivalents, as well as between NH4+ and SO42- or NO3- equivalents. Individual dicarboxylic acid showed a monotonically decreasing trend with increasing carbon number in which oxalic acid accounted for approximately 75% of the total dicarboxylic acids. Characteristic ratios of malonic acid to succinic acid and adipic acid to azelaic acid, MODIS fire spots, and backward trajectories showed that dicarboxylic acids mainly originated from secondary reactions in the atmosphere and that the direct contributions of open biomass burning to dicarboxylic acid concentrations were negligible.

Chemical characteristics of dicarboxylic acids and related organic compounds in PM2.5 during biomass-burning and non-biomass-burning seasons at a rural site of Northeast China

Fine particulate matter (PM2.5) samples were collected using a high-volume air sampler and pre-combusted quartz filters during May 2013 to January 2014 at a background rural site (47∘35 N, 133∘31 E) in Sanjiang Plain, Northeast China. A homologous series of dicarboxylic acids (C2-C11) and related compounds (oxoacids, α-dicarbonyls and fatty acids) were analyzed by using a gas chromatography (GC) and GC-MS method employing a dibutyl ester derivatization technique. Intensively open biomass-burning (BB) episodes during the harvest season in fall were characterized by high mass concentrations of PM2.5, dicarboxylic acids and levoglucosan. During the BB period, mass concentrations of dicarboxylic acids and related compounds were increased by up to >20 times with different factors for different organic compounds (i.e., succinic (C4) acid > oxalic (C2) acid > malonic (C3) acid). High concentrations were also found for their possible precursors such as glyoxylic acid (ωC2), 4-oxobutanoic acid, pyruvic acid, glyoxal, and methylglyoxal as well as fatty acids. Levoglucosan showed strong correlations with carbonaceous aerosols (OC, EC, WSOC) and dicarboxylic acids although such good correlations were not observed during non-biomass-burning seasons. Our results clearly demonstrate biomass burning emissions are very important contributors to dicarboxylic acids and related compounds. The selected ratios (e.g., C3/C4, maleic acid/fumaric acid, C2/ωC2, and C2/levoglucosan) were used as tracers for secondary formation of organic aerosols and their aging process. Our results indicate that organic aerosols from biomass burning in this study are fresh without substantial aging or secondary production. The present chemical characteristics of organic compounds in biomass-burning emissions are very important for better understanding the impacts of biomass burning on the atmosphere aerosols.

Secondary formation of oxalic acid and related organic species from biogenic sources in a larch forest at the northern slope of Mt. Fuji

To better understand the formation of water-soluble organic aerosols in the forest atmosphere, we measured low molecular weight (LMW) dicarboxylic acids, oxocarboxylic acids, α-dicarbonyls, unsaturated fatty acids (UFAs), and water-soluble organic carbon (WSOC) in aerosols from a Larix kaempferi forest located at the northern slope of Mt. Fuji, Japan, in summer 2012. Concentrations of dicarboxylic acids, oxocarboxylic acids, α-dicarbonyls, and WSOC showed maxima in daytime. Relative abundance of oxalic acid in LMW dicarboxylic acids was on average 52% and its average concentration was 214 ng m−3. We found that diurnal and temporal variations of oxalic acid are different from those of isoprene and α-pinene, whereas biogenic secondary organic aerosols (BSOAs) derived from isoprene and α-pinene showed similar variations with oxalic acid. The mass concentration ratios of oxalic acid/BSOAs were relatively constant, although a large variation in the concentrations of toluene that is an anthropogenic volatile organic compound was observed. These results suggest that formation of oxalic acid is associated with the oxidation of isoprene and α-pinene with O3 and other oxidants in the forest atmosphere. In addition, concentrations of UFAs were observed, for the first time, to decrease dramatically during daytime in the forest. Mass concentration ratios of azelaic acid to UFAs showed a positive correlation with O3, suggesting that UFAs are oxidized to yield azelaic acid, which may be further decomposed to oxalic acid in the forest atmosphere. We found that contributions of oxalic acid to WSOC are significantly high ranging from 3.7 to 9.7% (average 6.0%). This study demonstrates that forest ecosystem is an important source of oxalic acid and other dicarboxylic acids in the atmosphere.

Chemometric analysis of composition of bio-crude and aqueous phase from hydrothermal liquefaction of thermally and chemically pretreated Miscanthus x giganteus

Bio-crude from hydrothermal liquefaction (HTL) of lignocellulosic biomass is a potential alternative to conventional fossil fuels. Continuous HTL of lignocellulosic biomass requires feedstock pretreatment to obtain pumpable slurries. This work extends upon previous evaluations of pretreatment methods for obtaining stable slurries of Miscanthus х giganteus. In the current study, extensive characterization of the bio-crude and aqueous phase from HTL of thermally and chemically pretreated M. х giganteus is reported and molecular differences of these samples are evaluated. The bio-crude and aqueous phase is characterized with gas chromatography coupled to mass spectrometry using pre-derivatization with silylating reagent and methyl chloroformate, respectively. Principal component analysis shows that bio-crudes of untreated and slurry stabilized samples have higher concentrations of small organic acids and fatty acids, samples pretreated at mild alkali conditions have higher concentrations of alcohols, polyaromatics, and methylated phenolics, and samples pretreated with strong alkali conditions have higher concentrations of cyclic oxygenates and ketonized aromatics. Aqueous phases are separated based on the addition of slurry stabilizer which has higher concentrations of dicarboxylic acids and phenol. The detailed exploration of both bio-crude and aqueous phase will be of interest for other investigations of the pretreatment effects on biomass for hydrothermal liquefaction.

Seasonal and longitudinal distributions of atmospheric water‐soluble dicarboxylic acids, oxocarboxylic acids, and α‐dicarbonyls over the North Pacific

AbstractIn order to assess the seasonal variability of atmospheric abundances of dicarboxylic acids, oxocarboxylic acids, and α‐dicarbonyls over the North Pacific and Sea of Japan, aerosol samples were collected along the longitudinal transacts during six cruises between Canada and Japan. The back trajectory analyses indicate that aerosol samples collected in winter and spring are influenced by the East Asian outflow, whereas summer and fall samples are associated with the pristine maritime air masses. Molecular distributions of water‐soluble organics in winter and spring samples show the predominance of oxalic acid (C2) followed by succinic (C4) and malonic acids (C3). In contrast, summer and fall marine aerosols are characterized by the predominance of C3 over C4. Concentrations of dicarboxylic acids were higher over the Sea of Japan than the North Pacific. With a lack of continental outflow, higher concentrations during early summer are ascribed to atmospheric oxidation of organic precursors associated with high biological activity in the North Pacific. This interpretation is further supported by the high abundances of azelaic acid, which is a photochemical oxidation product of biogenic unsaturated fatty acids, over the Bering Sea in early summer when surface waters are characterized by high biological productivity. We found higher ratios of oxalic acid to pyruvic and glyoxylic acids (C2/Pyr and C2/ωC2) and glyoxal and methylglyoxal (C2/Gly and C2/MeGly) in summer and fall than in winter and spring, suggesting a production of C2 from the aqueous‐phase oxidation of oceanic isoprene. In this study, dicarboxylic acids account for 0.7–38% of water‐soluble organic carbon.

Seasonal Variations and Sources of Carboxylic Acids in PM2.5 in Wuhan, China

ABSTRACTAerosol PM2.5 samples collected from three sites in Wuhan, China, during 2011–2012 were analyzed by gas chromatography-mass spectrometry to better understand the molecular composition and sources of carboxylic acids. The concentrations of total monocarboxylic acids did not show apparent seasonal variations in Wuhan. Palmitic acid and stearic acid were the most abundant species, accounting for 32.4%–62.4% (average 51.8%) of all quantified monocarboxylic acids. Oxalic acid was found as the most dominant dicarboxylic acid, followed by succinic acid at the three sampling sites. The total concentration of dicarboxylic acids displayed obvious seasonal variation, with the highest in summer (1036.7–1546.4 ng/m3) and the lowest in winter (126.8–211.0 ng/m3). Positive matrix factorization (PMF) revealed that coal combustion, traffic-related emissions and biomass burning are the most important contributors to carboxylic acids at industrial site, downtown site and botanical garden, respectively. Plant waxes and secondary photochemical products are also significant sources of carboxylic acids at the three sampling sites.

Seasonal variation and source apportionment of organic tracers in PM10 in Chengdu, China.

Organic compound tracers including n-alkanes, triterpane, sterane, polycyclic aromatic hydrocarbons (PAHs) and dicarboxylic acids of airborne particulate matter (PM10) were characterized for samples collected at five sites from July 2010 to March 2011 using GC/MS. Spatial and temporal variations of these organic tracers in PM10 were studied, and their sources were then identified respectively. Average daily concentrations of PM10 varied in different seasons with the trend of PM10 in winter (0.133 mg/m(3)) > autumn (0.120 mg/m(3)) > spring (0.103 mg/m(3)) > summer (0.098 mg/m(3)). Daily concentrations of n-alkanes (C11-C36) ranged from 12.11 to 163.58 ng/m(3) with a mean of 61.99 ng/m(3). The C max and CPI index of n-alkanes indicated that vehicle emissions were the major source in winter, while the contributions of high plant wax emissions became significant in other seasons. It was discovered that the main sources of triterpenoid and steranes were gasoline and diesel engine emissions. Concentrations of ∑15PAHs in PM10 also varied (12.25-58.56 ng/m(3)) in different seasons, and chrysene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi) perylene and fluoranthene were the dominant components. In the four seasons, the concentration of ∑15PAHs was relatively higher at the northern site because of traffic congestion. The main source of airborne PAHs was traffic emissions and coal combustion. Average daily concentrations of dicarboxylic acids (C4-C10) in PM10 ranged from 12.11 to 163.58 ng/m(3), of which azeleic acid was the major compound (0.49-52.04 ng/m(3), average 14.93 ng/m(3)), followed by succinic acid (0.56-19.08 ng/m(3), average 6.84 ng/m(3)). The ratio of C6/C9 showed that the major source in winter was biological, while the contributions of emissions from anthropogenic activities were much higher in summer.

Evolution of chemical composition of fogwater in winter in Chengdu, China

Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon (TOC) > total nitrogen (TN) > total inorganic carbon (TIC) was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes (C11–C37) at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57–21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog (393.12 ng/mL) which was more than ten times that in the fog formation period (27.83 ng/mL) and the fog dissipation period (14.87 ng/mL). Concentrations of Σ15PAHs were in the range of 7.27–38.52 ng/mL at the urban site and 2.59–22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog (27.15 ng/mL) > fog dissipation period (11.59 ng/mL) > fog formation period (6.42 ng/mL). Concentrations of dicarboxylic acids (C5–C9) ranged from 10.92 to 40.78 ng/mL, with glutaric acid (C5) as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.

Observations of Sharp Oxalate Reductions in Stratocumulus Clouds at Variable Altitudes: Organic Acid and Metal Measurements During the 2011 E-PEACE Campaign

This work examines organic acid and metal concentrations in northeastern Pacific Ocean stratocumulus cloudwater samples collected by the CIRPAS Twin Otter between July and August 2011. Correlations between a suite of various monocarboxylic and dicarboxylic acid concentrations are consistent with documented aqueous-phase mechanistic relationships leading up to oxalate production. Monocarboxylic and dicarboxylic acids exhibited contrasting spatial profiles reflecting their different sources; the former were higher in concentration near the continent due to fresh organic emissions. Concentrations of sea salt crustal tracer species, oxalate, and malonate were positively correlated with low-level wind speed suggesting that an important route for oxalate and malonate entry in cloudwater is via some combination of association with coarse particles and gaseous precursors emitted from the ocean surface. Three case flights show that oxalate (and no other organic acid) concentrations drop by nearly an order of magnitude relative to samples in the same vicinity. A consistent feature in these cases was an inverse relationship between oxalate and several metals (Fe, Mn, K, Na, Mg, Ca), especially Fe. By means of box model studies we show that the loss of oxalate due to the photolysis of iron oxalato complexes is likely a significant oxalate sink in the study region due to the ubiquity of oxalate precursors, clouds, and metal emissions from ships, the ocean, and continental sources.

Synthesis of octacalcium phosphate with incorporated succinate and suberate ions

Octacalcium phosphate (OCP) has a layered structure composed of apatitic and hydrated layers. HPO42− in the hydrated layer can be substituted by dicarboxylate ions. The synthesis of octacalcium phosphate with incorporated dicarboxylate ions (octacalcium phosphate carboxylate, OCPC), was investigated through the effects of the initial concentration of dicarboxylic acid on the formation of OCPC. Succinic acid (Suc) and suberic acid (Sub) were used as dicarboxylic acids for preparing OCPC, and crystalline phases of the products were characterized by powder X-ray diffraction (XRD). When the amount of added dicarboxylic acid was 1–5 times the amount corresponding to the stoichiometric composition of OCPC, incorporation of dicarboxylate ions progressed with increasing amount of added dicarboxylic acids, although OCP without incorporated dicarboxylate ions was also present. When the amounts of added Suc and Sub were larger than 10 times the stoichiometric amount in OCPC, a single OCPC phase was detected in the powder XRD patterns. Amounts of Suc and Sub greater than 10 times the stoichiometric amounts facilitated formation of the OCPCs and inhibited formation of OCP. The incorporation of dicarboxylate ions into OCP competes with incorporation of HPO42−. Hence a high concentration of dicarboxylic acids is required for complete incorporation of dicarboxylate ions in OCP.

Secondary organic aerosol production from modern diesel engine emissions

Abstract. Secondary organic aerosol (SOA) production was observed at significant levels in a series of modern diesel exhaust (DE) aging experiments conducted at the European Outdoor Photoreactor/Simulation Chamber (EUPHORE). The greatest production occurred in DE with toluene addition experiments (&gt;40%), followed by DE with HCHO (for OH radical generation) experiments. A small amount of SOA (3%) was observed for DE in dark with N2O5 (for NO3 radical production) experiments. The analysis for a limited number (54) of polar organic compounds (POC) was conducted to assess the composition of modern DE and the formation of photochemical transformation products. Distinct POC formation in light versus dark experiments suggests the role of OH initiated reactions in these chamber atmospheres. A trend of increasing concentrations of dicarboxylic acids in light versus dark experiments was observed when evaluated on a compound group basis. The four toluene addition experiments in this study were performed at different [tol]o/[NOx]o ratios and displayed an average SOA %yield (in relation to toluene) of 5.3±1.6%, which is compared to past chamber studies that evaluated the impact of [tol]o/[NOx]o on SOA production in more simplified mixtures.

Speciation and temporal characterization of dicarboxylic acids in PM 2.5 during a PM episode and a period of non-episodic pollution

PM 2.5 aerosol was collected during a PM episode and a non-episodic pollution period between September and November 2004 in suburban southern Taiwan and dicarboxylic acid and inorganic species content and provenance were investigated. Oxalic acid was the dominant dicarboxylic acid species, followed by succinic acid and malonic acid. Tartaric acid concentrations were the lowest. There was 49.3% more dicarboxylic acid in PM episode aerosol than in non-episodic aerosol. However, daily oxalic acid concentration increased 72.7% in PM episode aerosol, while succinic acid fell 20.9% and malonic acid fell 21.6%, indicating higher conversion of these acids into oxalic acid in PM episode aerosol. Dicarboxylic acid concentrations, particularly oxalic acid, peaked at night during the PM episode, due to accumulation of daytime oxalic acid combined with low wind velocity and low mixing layer height at this time. SO 4 2−, NO 3 − and NH 4 + were the dominant ionic species in both PM episode and non-episodic aerosols. NO 3 − concentration increased 106% during the PM episode, while HNO 3, a gaseous precursor of NO 3 −, fell 57%, indicating a large conversion of HNO 3 to aerosol phase NO 3 − in PM episode aerosol. Backward trajectory data indicate that burning of paddy fields may also contribute to oxalic acid content in PM episode aerosol in the study area, especially during nighttime. Principal component analyses showed that succinic acid, malonic acid and oxalic acid were important factors in both pollution periods and also that there was high correlation between tartaric acid and NO x or HNO 2, indicative of vehicle emissions. The mass ratio of oxalic acid to sulfate in this aerosol was as high as 60.3‰, 35.5% higher than in non-episodic aerosol. Principal component analyses showed that photochemical aerosols contributed by succinic acid, malonic acid and oxalic acid were important factors in both periods. There was high correlation between tartaric acid and NO x or HNO 2, indicative of vehicle emissions.

Metastable equilibria among dicarboxylic acids and the oxidation state during aqueous alteration on the CM2 chondrite parent body

Linear saturated dicarboxylic acids are present in carbonaceous chondrite samples at concentrations that suggest aqueous alteration under conditions of metastable equilibrium. In this study, previously published values of dicarboxylic acid concentrations measured in Murchison, Yamato-791198, and Tagish Lake carbonaceous chondrites are converted to aqueous activities during aqueous alteration assuming water:rock ratios that range from 1:10 to 10:1. Logarithmic plots of the aqueous activities of any two dicarboxylic acids are proximal to lines whose slope is fixed by the stoichiometry of reactions describing the oxidation–reduction equilibrium between the two species. The precise position of any line is controlled by the equilibrium constant of the reaction relating the species and the hydrogen fugacity for the reaction of interest. Reactions among succinic (C4), glutaric (C5), and adipic (C6) acids obtained from CM2 chondrites show evidence of metastable equilibrium and yield log f H 2 values that agree to within 0.3 log units at 298.15 K and 0.6 log units at 473.15 K. At a water:rock ratio of 1:1, metastable equilibrium among succinic, glutaric, and adipic acids results in calculated log f H 2 values during aqueous alteration that range from −6.2 at 298.15 K to −3.3 at 373.15 K. These values are consistent with those obtained in previous work on carbonaceous chondrites and with metastable equilibrium at temperatures ranging from 300 to 355 K in contact with cronstedtite + magnetite.