Mineral dust aerosol is known to provide a reactive surface in the troposphere for heterogeneous chemistry to occur. Certain components of mineral dust aerosol, such as semiconductor metal oxides, can act as chromophores that initiate chemical reactions, while adsorbed organic and inorganic species may also be photoactive. However, relatively little is known about the impact of heterogeneous photochemistry of mineral dust aerosol in the atmosphere. In this study, we investigate the heterogeneous photochemistry of trace atmospheric gases including HNO(3) and O(3) with components of mineral dust aerosol using an environmental aerosol chamber that incorporates a solar simulator. For reaction of HNO(3) with aluminum oxide, broadband irradiation initiates photoreactions to form gaseous NO and NO(2). A complex dynamic balance between surface adsorbed nitrate and gaseous nitrogen oxide products including NO and NO(2) is observed. For heterogeneous photoreactions of O(3), iron oxide shows catalytic decompositions toward O(3) while aluminum oxide is deactivated by ozone exposure. Furthermore, the role of relative humidity, and, thus, adsorbed water, on heterogeneous photochemistry has been explored. The atmospheric implications of these results are discussed.

Metal-regulatory transcription factor 1 (MTF1) is a conserved metal-binding transcription factor in eukaryotes that binds to conserved DNA sequence motifs, termed metal response elements. MTF1 responds to both metal excess and deprivation, protects cells from oxidative and hypoxic stresses, and is required for embryonic development in vertebrates. To examine the role for MTF1 in cell differentiation, we use multiple experimental strategies [including gene knockdown (KD) mediated by small hairpin RNA and clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein 9 (CRISPR/Cas9), immunofluorescence, chromatin immunopreciptation sequencing, subcellular fractionation, and atomic absorbance spectroscopy] and report a previously unappreciated role for MTF1 and copper (Cu) in cell differentiation. Upon initiation of myogenesis from primary myoblasts, both MTF1 expression and nuclear localization increased. Mtf1 KD impaired differentiation, whereas addition of nontoxic concentrations of Cu + -enhanced MTF1 expression and promoted myogenesis. Furthermore, we observed that Cu + binds stoichiometrically to a C terminus tetra-cysteine of MTF1. MTF1 bound to chromatin at the promoter regions of myogenic genes, and Cu addition stimulated this binding. Of note, MTF1 formed a complex with myogenic differentiation (MYOD)1, the master transcriptional regulator of the myogenic lineage, at myogenic promoters. These findings uncover unexpected mechanisms by which Cu and MTF1 regulate gene expression during myoblast differentiation.-Tavera-

Environmental context. Iron, a limiting nutrient of plankton in the ocean, is deposited to the sea from atmospheric aerosols. In particular, atmospheric acidic conditions promote dissolution of iron from fly ash, a byproduct of coal-fired power plants. Here, we report that the iron leached from fly ash depends on its source region, and that the type of combustion process may influence the iron species mobilized.Abstract. Fly ash, an iron-containing by-product of coal-fired power plants, has been observed in atmospheric aerosol plumes. Under the acidic atmospheric conditions resulting from the uptake of atmospheric gases, iron leached from fly ash can impact global biogeochemical cycles. However, the fly ash source region, as well as its generating power plant, plays an important role in the amount, speciation and lability of iron. Yet no comparative studies have been made on iron leached from fly ash from different sources. This study reports the iron mobilisation by proton-promoted dissolution from wellcharacterised fly ash samples from three distinctive locations: the USA Midwest, north-east India and Europe. In addition, pH dependency was also investigated. Proton-promoted dissolution showed a variability between source regions with a relative iron leach in the order USA Midwestern . north-east Indian . European ash. In addition, the initial rate of iron leach suggests that source region is indeed a determining factor in the iron leaching capacity of fly ash, because dissolution from Midwestern fly ash is also faster than both European and Indian ash. Finally, the combustion process of fly ash proved to be significant for the iron speciation, given that well-combusted fly ash samples leached mostly Fe 3þ rather than bioavailable Fe 2þ . The role of fly ash should therefore be taken into account in order to better understand the effects of combustion particles in atmospheric iron deposition.

In this study, CO 2 adsorption in the presence and absence of co-adsorbed H 2 O was investigated in zeolite Y. Several different zeolite Y materials were investigated including commercial NaY, commercial NaY ion-exchanged with Ba 2+ and nanocrystalline NaY; herein referred to as NaY, BaY and nano-NaY. Following heating of these zeolites to 573 K and cooling to room temperature, CO 2 was adsorbed as a function of pressure. FTIR spectra show that a majority of CO 2 adsorbs in the pores of these three zeolites (NaY, BaY and nano-NaY) in a linear complex with the exchangeable cation, as indicated by the intense absorption band near 2350 cm À1 , assigned to the n 3 asymmetric stretch of adsorbed CO 2 . Most interestingly is the formation of carbonate and bicarbonate on the external surface of nano-NaY zeolites as indicated by the presence of several broad absorption bands in the 1200-1800 cm À1 region, suggesting unique sites for CO 2 adsorption on the surface of the nanomaterial. For the other two zeolite materials investigated, bicarbonate formation is only evident in BaY zeolite in the presence of co-adsorbed water. Adsorption of 18 O-labeled carbon dioxide and theoretical quantum chemical calculations confirm these assignments and conclusions.

Environmental context. Dust particles produced from wind blown soils are of global significance as these dust particles not only impact visibility, as evident in the recent 2009 Australian dust storm, but also atmospheric chemistry, climate and biogeochemical cycles. The amount of water vapour in the atmosphere (relative humidity) can play a role in these global processes yet there are few studies and little quantitative data on water-dust particle interactions. The focus of this research is on quantifying water-dust particle interactions for several dust sources including Asia and Africa where dust storms are most prevalent. Abstract. Mineral dust aerosol provides a reactive surface in the troposphere. The reactivity of mineral dust depends on the source region as chemical composition and mineralogy of the aerosol affects its interaction with atmospheric gases. Furthermore, the impact of mineral dust aerosol in atmospheric processes and climate is a function of relative humidity. In this study, we have investigated water uptake of complex dust samples. In particular, water uptake as a function of relative humidity has been measured on three different dust sources that have been characterised using a variety of bulk and surface techniques. For these well-characterised dust samples, it is shown that although there are variations in chemical composition and mineralogy, on a per mass basis, water uptake capacities for the three dusts are very similar and are comparable to single component clay samples. These results suggest that the measured uptake of water of these bulk samples is dominated by the clay component.