Chemical interactions of polycyclic organic compounds with coal fly ash and related solid surfaces

The interactions of polycyclic aromatic hydrocarbons (PAHs) with particulate surfaces (especially those of coal fly ash) have been investigated, and the influence of coal ash surface properties on the photochemical transformation of adsorbed PAHs has been studied. The overall objective of the work has been to characterize the effects of adsorption onto atmospheric particulate matter on the chemical behavior of PAHs released into the atmosphere via combustion processes. Progress is reported in the following areas of effort: (a) Major emphasis has been devoted to the interactions of PAHs with the different particulate phases that are found in heterogeneous coal ash samples. Techniques have been developed and thoroughly characterized for the fractionation of coal ashes into carbonaceous, mineral-magnetic, and mineral-nonmagnetic subfractions. Heats of adsorption for pyrene on such subfractions have been measured by gas-solid chromatography, and the photoreactivity of pyrene and benz[a]anthracene on ash subfractions has been examined. Carbonaceous particles exhibit the highest affinity for vapor-phase PAHS; mineral magnetic particles usually exhibit the smallest tendency to sorb PAHs from the vapor phase. Adsorption of PAHs on carbonaceous particles suppresses, virtually completely, their tendency to undergo photochemical transformation. For coal ashes that contain few carbonaceous particles, the adsorption and photochemical transformation of PAHs tend to be dominated by the mineral nonmagnetic particles; PAHs adsorbed on these particles tend to exhibit relatively efficient phototransformation

Sorption and chemical transformation of PAHs on coal fly ash

The objective of this research is to characterize the interactions of coal fly ash with polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and to understand the influence of the surface properties of coal ash (and other atmospheric particles) on the chemical transformations of polycyclic aromatic compounds. During the past year the following specific aspects of this broad problem area have been investigated: (a) Fractionation of heterogeneous coal fly ash samples into different particle types varying in size and chemical composition (carbonaceous, mineral-magnetic, and mineral nonmagnetic); (b) The use of gas-solid chromatography to measure heats of sorption of PAHS, and PAH derivatives, on coal fly ashes and ash fractions. (c) Identification of the major photoproduct(s) of the photodecomposition of one PAH (benz[a]anthracene) sorbed on model adsorbents; (d) Estimation of fractal dimensions'' of coal fly ash particles by use of specific surface area measurements, with an ultimate objective of using these measurements to assess the importance of inner-filter effects'' on the photodecomposition of PAHs sorbed on fly ash particles. (e) The photochemical transformation of a representative nitro-PAH derivative (1-nitropyrene) sorbed on fly ash. (f) Development of techniques for studying the nonphotochemical reactions of hydroxyl radicals (and other atmospheric constituents) with PAHs sorbed on fly ash. Progress achieved, and problems encountered, in each of these major areas of emphasis is described below

Dust detection by the wave instrument on STEREO: nanoparticles picked up by the solar wind?

The STEREO/WAVES instrument has detected a very large number of intense voltage pulses. We suggest that these events are produced by impact ionisation of nanoparticles striking the spacecraft at a velocity of the order of magnitude of the solar wind speed. Nanoparticles, which are half-way between micron-sized dust and atomic ions, have such a large charge-to-mass ratio that the electric field induced by the solar wind magnetic field accelerates them very efficiently. Since the voltage produced by dust impacts increases very fast with speed, such nanoparticles produce signals as high as do much larger grains of smaller speeds. The flux of 10-nm radius grains inferred in this way is compatible with the interplanetary dust flux model. The present results may represent the first detection of fast nanoparticles in interplanetary space near Earth orbit.Comment: In press in Solar Physics, 13 pages, 5 figure

The Effect of Calcium Ions on Mechanosensation and Neuronal Activity in Proprioceptive Neurons

Proprioception of all animals is important in being able to have coordinated locomotion. Stretch activated ion channels (SACs) transduce the mechanical force into electrical signals in the proprioceptive sensory endings. The types of SACs vary among sensory neurons in animals as defined by pharmacological, physiological and molecular identification. The chordotonal organs within insects and crustaceans offer a unique ability to investigate proprioceptive function. The effects of the extracellular environment on neuronal activity, as well as the function of associated SACs are easily accessible and viable in minimal saline for ease in experimentation. The effect of extracellular [Ca2+] on membrane properties which affect voltage-sensitivity of ion channels, threshold of action potentials and SACs can be readily addressed in the chordotonal organ in crab limbs. It is of interest to understand how low extracellular [Ca2+] enhances neural activity considering the SACs in the sensory endings could possibly be Ca2+ channels and that all neural activity is blocked with Mn2+. It is suggested that axonal excitability might be affected independent from the SAC activity due to potential presence of calcium activated potassium channels (K(Ca)) and the ability of Ca2+ to block voltage gated Na+ channels in the axons. Separating the role of Ca2+ on the function of the SACs and the excitability of the axons in the nerves associated with chordotonal organs is addressed. These experiments may aid in understanding the mechanisms of neuronal hyperexcitability during hypocalcemia within mammals

Sorption and chemical transformation of PAH`s on coal fly ash

The major objective of this work was to characterize the interactions of coal fly ash with polycyclic aromatic hydrocarbons (PAHS) and their derivatives, and to attempt to understand the influence of the surface properties of coal ash (and other atmospheric particles) on the chemical transformations of polycyclic aromatic compounds. Our studies have concentrated on the photochemical behavior of PAHs sorbed form the vapor phase on coal fly ashes, and compositional subfractions obtained therefrom. The PAHs are deposited onto the fly ash substrates from the vapor phase, using apparatus and techniques developed in this laboratory in order to simulate, as closely as possible under laboratory conditions, the processes by which PAHs deposit onto fly ash particles in the atmosphere. In this report phototransformation of pyrene sorbed on fly ash fractions, and phototransformations of 1-nitropyrene sorbed on fly ash fractions are discussed

Sorption and chemical transformation of PAHs on coal fly ash. Annual technical progress report No. 4, [November 1, 1991--October 31, 1992]

The objective of this research is to characterize the interactions of coal fly ash with polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and to understand the influence of the surface properties of coal ash (and other atmospheric particles) on the chemical transformations of polycyclic aromatic compounds. During the past year the following specific aspects of this broad problem area have been investigated: (a) Fractionation of heterogeneous coal fly ash samples into different particle types varying in size and chemical composition (carbonaceous, mineral-magnetic, and mineral nonmagnetic); (b) The use of gas-solid chromatography to measure heats of sorption of PAHS, and PAH derivatives, on coal fly ashes and ash fractions. (c) Identification of the major photoproduct(s) of the photodecomposition of one PAH (benz[a]anthracene) sorbed on model adsorbents; (d) Estimation of ``fractal dimensions`` of coal fly ash particles by use of specific surface area measurements, with an ultimate objective of using these measurements to assess the importance of ``inner-filter effects`` on the photodecomposition of PAHs sorbed on fly ash particles. (e) The photochemical transformation of a representative nitro-PAH derivative (1-nitropyrene) sorbed on fly ash. (f) Development of techniques for studying the nonphotochemical reactions of hydroxyl radicals (and other atmospheric constituents) with PAHs sorbed on fly ash. Progress achieved, and problems encountered, in each of these major areas of emphasis is described below

Chemical interactions of polycyclic organic compounds with coal fly ash and related solid surfaces. Final report, July 1, 1987--December 31, 1989

The interactions of polycyclic aromatic hydrocarbons (PAHs) with particulate surfaces (especially those of coal fly ash) have been investigated, and the influence of coal ash surface properties on the photochemical transformation of adsorbed PAHs has been studied. The overall objective of the work has been to characterize the effects of adsorption onto atmospheric particulate matter on the chemical behavior of PAHs released into the atmosphere via combustion processes. Progress is reported in the following areas of effort: (a) Major emphasis has been devoted to the interactions of PAHs with the different particulate phases that are found in heterogeneous coal ash samples. Techniques have been developed and thoroughly characterized for the fractionation of coal ashes into carbonaceous, mineral-magnetic, and mineral-nonmagnetic subfractions. Heats of adsorption for pyrene on such subfractions have been measured by gas-solid chromatography, and the photoreactivity of pyrene and benz[a]anthracene on ash subfractions has been examined. Carbonaceous particles exhibit the highest affinity for vapor-phase PAHS; mineral magnetic particles usually exhibit the smallest tendency to sorb PAHs from the vapor phase. Adsorption of PAHs on carbonaceous particles suppresses, virtually completely, their tendency to undergo photochemical transformation. For coal ashes that contain few carbonaceous particles, the adsorption and photochemical transformation of PAHs tend to be dominated by the mineral nonmagnetic particles; PAHs adsorbed on these particles tend to exhibit relatively efficient phototransformation

Sorption and chemical transformation of PAHs on coal fly ash. Technical progress report No. 5, [November 1, 1992--January 31, 1993]

The objective of this work is to characterize the interactions of coal fly ash with polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and to understand the influence of the surface properties of coal ash (and other atmospheric particles) on the chemical transformations of polycyclic aromatic compounds. Specific investigations directed toward this overall objective include: (a) Fractionation of heterogeneous coal fly ash samples into different particle types varying in size and chemical composition (carbonaceous, mineral-magnetic and mineral nonmagnetic); (b) measurement of the rates of chemical transformation of PAHs and PAH derivatives (especially nitro-PAHs) and the manner in which the rates of such processes are influenced by the chemical and physical properties of coal fly ash particles; (c) Chromatographic and spectroscopic studies of the nature of the interactions of coal fly ash particles with PAHs and PAH derivatives; (d) Characterization of the fractal nature of fly ash particles (via surface area measurements) and the relationships of ``surface roughness`` of fly ash particles to the chemical behavior of PAHs sorbed on coal ash particles; PAHs are deposited, under controlled laboratory conditions, onto coal ash surfaces from the vapor phase, in order to mimic the processes by which PAHs are deposited onto particulate matter in the atmosphere