Thermodynamic properties of the isomers of [HNOS], [HNO2 S], and [HNOS2 ] and the role of the central sulfur.

Simple hydrides of compounds containing N, S, and O are of significant interest due to the role that they play in atmospheric chemistry and in biological pathways. There is a lack of quantitative thermodynamic data on these compounds. We have used a reliable computational chemistry approach based on valence CCSD(T) calculations extrapolated to the complete basis set limit with additional corrections to predict the heats of formation and bond dissociation energies of such compounds. The results show that compounds with the ability of the central S atom to effectively expand its valency leads to more stable isomers and, as a consequence, that those with the NSO structural motif are thermochemically more stable than those with the SNO motif. In addition, SO bonds are preferred over NO bonds.

Multiresidues of pesticides in the particulate matter (PM10) emitted by rural soils of the semiarid pampas, Argentina. A potential source of air pollution.

The aim of this work was to evaluate the presence of 40 pesticides in the PM10 emitted by rural soils of the semiarid region of Argentina. Six agricultural soils for grain production under no till and with high use of pesticides (AG), 5 agricultural soils for forage and grain production under conventional tillage (AFG) and 5 unpaved rural roads (RR) were sampled. The PM10 was generated using the Easy Dust Generator and it was collected with an electrostatic precipitator. The presence of 20 herbicides, 14 insecticides and 6 fungicides was analyzed in the soil and in the PM10. More than 70% of the pesticides analyzed were detected in the soil and in the PM10. All agricultural soils and 87% of RR soils showed at least one residue of pesticides. Multiresidues of pesticides were found in the 100% of PM10 emitted by rural soils. The mean number of pesticides was higher in the PM10 (7) than in the soil (5). Some pesticides were not detected in the soils but they were detected in the PM10 (triticonazole, carbofuran, metsulfuron methyl) and vice versa. In general, the concentrations of herbicides were higher in the PM10 than in the soil, while the concentrations of insecticides and fungicides were lower in the PM10 than in the soil. These results suggest that the concentrations of pesticide in the PM10 (inhalable fraction) should be used instead the concentrations of pesticide in the soil to calculate the exposure factor to pesticides by dust inhalation. This study provides the initial evidence of the presence of multiple pesticide residues in PM10 emitted by rural soils under different land management. Also confirms that the PM10 is a potential source of air contamination with pesticides. Future studies should be driven to measure the concentrations of pesticides and their dynamics in the PM10.

First evidence of glyphosate and aminomethylphosphonic acid (AMPA) in the respirable dust (PM10) emitted from unpaved rural roads of Argentina.

The aim of this work was to compare the concentration of glyphosate and AMPA in the PM10 and the actual PM10 emission from agricultural soils and unpaved roads, located inside and outside farm fields. To determine the actual PM10 emission by wind erosion, the actual wind erosion was estimated using the Wind Erosion Equation, and the PM10 emission efficiency was measured with the Easy Dust Generator. PM10 was collected in an electrostatic precipitator coupled to the Easy Dust Generator. Actual PM10 emission was 11.5 g ha-1 year-1 in agricultural soils and 4711.4 g ha-1 year-1 in unpaved roads. The high value of actual PM10 emission in unpaved roads was due to their high actual wind erosion and the high PM10 emission efficiency, while the low value in agricultural soils was due to their low actual wind erosion. Content of glyphosate in the PM10 ranged from 59 to 359 µg kg-1 in agricultural soils, from 382 to 454 µg kg-1 in unpaved roads inside farm fields, and from 39 to 639 µg kg-1 in unpaved roads outside farm fields. Content of AMPA in the PM10 ranged from 387 to 7228 µg kg-1 in agricultural soils, from 900 to 4138 µg kg-1 in unpaved roads inside farm fields, and 98 to 500 µg kg-1 in unpaved roads outside farm fields. AMPA concentration in PM10 was higher than that of glyphosate due to the longer persistence of AMPA than glyphosate. Glyphosate and AMPA concentrations in PM10 were higher than in soil, which is an additional risk that should be considered when the effect of PM10 emitted by agricultural soils and unpaved roads on human health are evaluated. Our results show that the amount and chemical composition of PM10 emitted by wind erosion from unpaved roads should be studied in other regions.

Chemical reactivity of the frustrated Lewis pairs in borophosphines: a theoretical analysis of their Lewis acidity, Lewis basicity and Fukui function.

The chemical reactivity of a set of borophosphines of the general formula R2B-G-PY2, where G is the connector group between the Lewis acidic site, a borane group, and the Lewis basic site, a phosphine fragment, is theoretically investigated through their Lewis acidity and Lewis basicity, as well as the location of the Fukui function and the shape of the molecular electrostatic potential. The role of some global reactivity descriptors, like the vertical ionization potential, I, and the vertical electron affinity, A, is also analyzed in order to gain a deeper insight on the intrinsic chemical reactivity of these borophosphines. We also use the energies involved in the formation of the adducts between the borophosphine and the ions H- and H+ to estimate the Lewis acidity and Lewis basicity, respectively; by their nature, these energies represent local reactivity descriptors. Some of these borophosphines are able to activate the covalent bond in the hydrogen molecule. Possible paths for the hydrogen release reaction from the zwitterion R[Formula: see text]HB-G-PH[Formula: see text] are studied using the mentioned quantities, suggesting that an intramolecular hydride shift mechanism seems to be more favorable than a proton migration process. The acceptor Fukui function f+(r) proved to be useful to identify the acidic molecular sites for the interaction with the hydride ion and the relative stability of the corresponding adducts is related to the relative values of this function.

Dynamics of volcanic ash remobilisation by wind through the Patagonian steppe after the eruption of Cordón Caulle, 2011.

Wind erosion of freshly-deposited volcanic ash causes persistent storms, strongly affecting ecosystems and human activity. Wind erosion of the volcanic ash was measured up to 17 months after the ash deposition, at 7 sites located within the ash-deposition area. The mass flux was measured up to 1.5 m above ground level. Mass transport rates were over 125 times the soil wind-erosion rates observed before the ash deposition, reaching up to 6.3 kg m-1 day-1. Total mass transport of ash during the 17 months ranged between 113.6 and 969.9 kg m-1 depending on topographic location and wind exposure. The vertical distribution of the mass flux at sites with higher vegetation cover was generally inverted as compared to sites with lower vegetation cover. This situation lasted 7 months and then a shift towards a more uniform vertical distribution was observed, in coincidence with the beginning of the decline of the mass transport rates. Decay rates differed between sites. Despite changes over time, an inverse linear correlation between the mass transports and the mass-flux gradients was found. Both the mass-flux gradients and the average mass-transport rates were not linked with shear-stress partition parameters, but with the ratio: ash-fall thickness to total vegetation cover.

Iron emission lines from extended x-ray jets in SS 433: reheating of atomic nuclei.

Powerful relativistic jets are among the most ubiquitous and energetic observational consequences of accretion around supermassive black holes in active galactic nuclei and neutron stars and stellar-mass black holes in x-ray binary (XRB) systems. But despite more than three decades of study, the structure and composition of these jets remain unknown. Here we present spatially resolved x-ray spectroscopy of arc second-scale x-ray jets from XRB SS 433 analyzed with the Chandra advanced charge-coupled device imaging spectrometer. These observations reveal evidence for a hot continuum and Doppler-shifted iron emission lines from spatially resolved regions. Apparently, in situ reheating of the baryonic component of the jets takes place in a flow that moves with relativistic bulk velocity even more than 100 days after launch from the binary core.