Abstract In this paper, recent advances in using stable isotopes of atmospheric nitrate to trace the origin and fate are reviewed. While nitrogen isotopes have been used as the indicators of NOx source contributions to the atmospheric nitrate, cautions must be taken for the isotopic fractionations during the photochemical reactions of NOX in atmosphere. On the other hand, the triple oxygen isotope composition (Δ17O) is a robust tracer for the photochemical reaction path of NOX in atmosphere. Besides, the triple oxygen isotope composition can be applied to trace the fate of atmospheric nitrate and to evaluate biological processing of nitrate within the earth surface ecosystems.
Abstract Stable isotope information for atmospheric sulfate and its related species are the useful tool which enables us to elucidate their sources and formation and sink processes. In this paper, recent knowledge obtained for sulfate aerosols using traditional and non-traditional isotopic analyses is reviewed. For the stratospheric sulfate aerosols (SSA), carbonyl sulfide isotopic composition and isotopic fractionations for its sink processes are discussed to test the source of background SSA, and stratospheric volcanic signals for polar sulfate using 33S excess are reviewed. For the tropospheric sulfate aerosols, various sources and fractionations for the atmospheric processes are summarized, and investigations of sulfate formation pathways using 17O excess for sulfate are introduced.
Abstract Radiocarbon (14C) is a powerful tracer for source apportionment of carbonaceous aerosols, because it can provide a measure for estimating the ratio of carbonaceous fraction from fossil and biomass/biogenic sources. To quantify 14C concentration not only for total carbon (TC), but also organic carbon (OC), elemental carbon (EC) and water-soluble OC (WSOC) in atmospheric aerosol, separation techniques of carbonaceous fractions have been investigated so far. This paper focuses on the methods for separating carbonaceous fractions and on the intercomparison of 14C concentration measurements of each carbonaceous fraction. Recent studies on the separation of OC and EC for 14C measurements have suggested the importance of 1) extraction of WSOC before thermal separation, 2) heating temperature for the removal of refractory OC, and 3) comparison of 14C concentrations in each fraction measured with different protocols. Direct measurements of 14C concentration in WSOC have also been reported. The measurements of 14C in carbonaceous fractions help revealing the carbonaceous sources and behaviors in environments.
Abstract We introduce the fundamentals of molecular simulations for a quantum fluid like hydrogen at low temperatures, and quantum molecular sieving of hydrogen isotope at 77 K. We show that the so-called isotope effects come not only from the difference in the diffusion coefficient but also from the difference in intermolecular interaction due to quantum effects. We also describe the problems and foresight about the molecular simulations for the quantum systems in nanospaces.
Abstract In order to investigate the influences of organic acids on heterogeneous reactions of SO2 with CaCO3 which is contained in mineral dust, a Raman microscope was used for tracking microscopic temporal changes in the reactions of the droplet of organic acids solution dissolving CaCO3 and gaseous SO2. Oxalic acid, malonic acid, citric acid, benzoic acid, acetic acid and propionic acid with different acidities were selected. The oxalic acid could easily combined with the calcium in solution and produce the calcium oxalate which is unsolvable. The Ca2＋ dissolved in solution of acetic and propionic acids reacted with SO2 to form CaSO4·2H2O which was gypsum. The CaCO3 solution containing malonic, citric or benzoic acids considerably enhanced the SO2 absorption because of the effect of buffered solution which consists of a mixture of a weak acid and its calcium compounds. Effects of organic acids on heterogeneous reactions of SO2 with CaCO3 were strongly dependent on the acidity of organic acids and the solubilities of produced organic calcium compounds.
Abstract To evaluate seasonal variations and sources of the carbonaceous components in aerosols emitted from biomass burning and vegetation in urban site, we measured organic carbon, elemental carbon, radiocarbon (14C) in total carbon (TC), and levoglucosan concentrations in total suspended particulate matter collected in Nagoya. Higher 14C concentrations were observed during spring (56.4 pMC) and summer–early fall (57.4 pMC) than during late fall–winter (47.1 pMC). In particular, 14C concentration in April was influenced by pollens, and it showed the highest 14C value (about 70 pMC) in our observations. Levoglucosan concentrations had clear seasonal variations: the contents from late fall–winter were higher than those in other seasons, similar to other reports in Japan. Moreover, levoglucosan had a good correlation with non-fossil carbon in total carbon (TCnf) calculated by 14C concentration, from early fall–winter. Furthermore, TCnf was roughly divided into two origins: biomass burning (TCbb) and biogenic carbon except for biomass burning (TCbio). The contributions of TCbb to TCnf and TC in late fall–winter were found to be the highest. Meanwhile, TCbio was higher than TCbb in all seasons, and the main sources of TCbio were considered to vary by seasons: pollens in spring and biogenic secondary organic aerosols in summer.