Variation of NO2 and NOx concentrations between and within 36 European study areas: Results from the ESCAPE study

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Spatial variation of PM2.5, PM10, PM2.5 absorbance and PMcoarse concentrations between and within 20 European study areas and the relationship with NO2 - Results of the ESCAPE project

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Nothing Lasts Forever: Environmental Discourses on the Collapse of Past Societies

The study of the collapse of past societies raises many questions for the theory and practice of archaeology. Interest in collapse extends as well into the natural sciences and environmental and sustainability policy. Despite a range of approaches to collapse, the predominant paradigm is environmental collapse, which I argue obscures recognition of the dynamic role of social processes that lie at the heart of human communities. These environmental discourses, together with confusion over terminology and the concepts of collapse, have created widespread aporia about collapse and resulted in the creation of mixed messages about complex historical and social processes

Syntheses of oxygen analogues of sulfhemes-A and -C

Syntheses of metal-free oxygen analogues of the sulfhemes-A and -C from protoporphyrin-IX dimethyl ester I are presented. Oxasulfporphyrin-C dimethyl ester 5 is obtained by intramolecular displacement of a primary tosylate by a tertiary hydroxyl in an appropriately constructed precursor 18, or by surface-catalyzed rearrangement of the epoxide-bearing oxasulfporphyrin-A dimethyl ester 23. Compound 23 is in turn prepared by Mitsunobu type internal dehydration of the precursor 12. The methodology is then successfully extended to more symmetric porphyrin systems. Compounds 23, 25, 46, and 61/62 are the first porphyrin epoxides to be synthesized

Syntheses of new porphyrin-type photosensitizers for photodynamic therapy

In the first part of this paper, syntheses of water-soluble photosensitizers for use in photodynamic therapy are described. Vinylporphyrins and vinylchlorins react with N.N- dimethylmethyleneammonium iodide (Eschenmoser\u27s reagent) to give 2- (dimethylaminomethyl)vinyl derivatives which can be readily quaternized with methyl iodide to give highly water-soluble quaternary ammonium salts. Deuteroporphyrin-IX dimethyl ester undergoes direct substitution with dimethylaminomethyl at the nuclear 2- and 4-positions. The second part of this report describes the syntheses of bacteriochlorin analogues of natural chlorophyll derivatives; these are obtained by osmium tetraoxide oxidation of chlorins to give vic-dihydroxybacteriochlorins. Acid catalyzed pinacol-pinacolone rearrangements of a number of vic-dihydroxybacterochlorins to given ketobacteriochlorins are described, and the chemistry of the rearrangement is investigated. Biological studies of all sensitizers described will be reported elsewhere

Ice-Nucleating Particles Near Two Major Dust Source Regions

Mineral dust and sea spray aerosol represent important sources of ice-nucleating particles (INPs), the minor fraction of aerosol particles able to trigger cloud ice crystal formation and, consequently, influence multiple climate-relevant cloud properties including lifetime, radiative properties and precipitation initiation efficiency. Mineral dust is considered the dominant INP source in many parts of the world due to its ice nucleation efficiency and its sheer abundance, with global emission rates of up to 4700 Tg a−1. However, INPs emitted from the ocean surface in sea spray aerosol frequently dominate INP populations in remote marine environments, including parts of the Southern Ocean where cloud-resolving model simulations have demonstrated that cloud radiative properties are likely strongly controlled by INPs. Here we report INP concentrations measured in aerosol and seawater samples during Air Quality and Climate Change in the Arabian Basin (AQABA), a shipborne campaign that spanned the Red Sea, Gulf of Aden, Arabian Sea, Arabian Gulf and part of the Mediterranean. In aerosol samples collected within a few hundred kilometers of the first and second ranked sources of dust globally, the Sahara and Arabian Peninsula, INP concentrations ranged from 0.2 to 11 L−1 at −20 ∘C with observed ice-active surface site densities (ns) 1–3 orders of magnitude below levels predicted by mineral dust INP parameterizations. Over half of the samples (at least 14 of 26) were collected during dust storms with average dust mass concentrations between 150 and 490 µg m−3 (PM10), as simulated by the Modern-Era Retrospective analysis for Research and Application, version 2 (MERRA-2). The impacts of heat and peroxide treatments indicate that organics dominated the observed ice nucleation (IN) activity at temperatures ≥ −15 ∘C with proteinaceous (heat-labile) INPs frequently observed at high freezing temperatures >−10 ∘C. INP concentrations in seawater samples ranged between 3 and 46 mL−1 at −19 ∘C, demonstrating the relatively low INP source potential of seawater in the region as compared to seawater from multiple other regions reported previously. Overall, our results demonstrate that despite proximity to the Sahara and the Arabian Peninsula and the dominance of mineral dust in the aerosol sampled, existing mineral dust parameterizations alone would not skillfully represent the near-surface ns in the observed temperature regime (−6 to −25 ∘C). Future efforts to develop or improve representations of dust INPs at modest supercooling ( ∘C) would benefit from a characterization of the specific organic species associated with dust INPs. More generally, an improved understanding of the organic species associated with increased IN activity and their variability across dust source regions would directly inform efforts to determine whether ns-based parameterizations are appropriate for faithful representation of dust INPs in this sensitive temperature regime, whether region-specific parameterizations are required, or whether an alternative to the ns approach is necessary

Ice-Nucleating Particles Near Two Major Dust Source Regions

Mineral dust and sea spray aerosol represent important sources of ice nucleating particles (INPs), the minor fraction of aerosol particles able to trigger cloud ice crystal formation and, consequently, influence multiple climate-relevant cloud properties including lifetime, reflectivity, and precipitation efficiency. Mineral dust is considered the dominant INP source in many parts of the world due to its ice nucleation efficiency and its sheer abundance, with global emission rates of up to 4700 Tg a−1. However, INPs emitted from the ocean surface in sea spray aerosol frequently dominate INP populations in remote marine environments, including parts of the Southern Ocean where cloud-resolving model simulations have demonstrated that cloud reflectivity is likely strongly controlled by INPs. Here we report INP concentrations measured in aerosol and seawater samples during Air Quality and Climate Change in the Arabian BAsin (AQABA), a shipborne campaign that spanned the Red Sea, Gulf of Aden, Arabian Sea, Arabian Gulf, and part of the Mediterranean. In aerosol samples collected within a few hundred kilometers of the first and second ranked sources of dust globally, the Sahara and Arabian Peninsula, INP concentrations ranged from 0.2 to 11 L−1 at −20 °C with observed ice nucleation site densities (ns) 1–3 orders of magnitude below levels predicted by mineral dust INP parameterizations. Over half of the samples (at least 14 of 26) were collected during dust storms with average dust mass concentrations between 150 and 490 μg m−3 (PM10). The impacts of heat and peroxide treatments indicate that organics were responsible for the observed ice nucleation (IN) -activity at temperatures ≥ −15 °C with proteinaceous (heat-labile) INPs frequently observed at higher freezing temperatures > −10 °C. Overall, results demonstrate that despite proximity to the Sahara and the Arabian Peninsula and the dominance of mineral dust in the aerosol sampled, existing mineral dust parameterizations alone would not skillfully represent the near-surface ns in the observed temperature regime (−6 to −25 °C). The decreased ns, and results demonstrating that organics dominated the observed IN activity > −15 °C, indicate that the IN-active organic species are limited compared to the mineral IN components of dust. Future efforts to develop or improve representations of dust INPs at modest supercooling (> −15 °C) would benefit from a characterization of the specific organic species associated with dust INPs. More generally, an improved understanding of the organic species associated with increased IN -activity and their variability across dust source regions would directly inform efforts to determine whether ns-based parameterizations are appropriate for faithful representation of dust INPs in this sensitive temperature regime, whether region-specific parameterizations are required, or whether an alternative to the ns approach is necessary