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- Budhavant, K. B., et al.
(författare)
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Chemical composition of the inorganic fraction of cloud-water at a high altitude site in West India
- 2014
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 88, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- Data from a ground-based cloud-water collection system intercepting water from clouds at a mountain field station, Sinhagad near Pune in India are presented. This study was part of an Indo-Swedish Collaboration Project on Atmospheric Brown Cloud-Asia (ABC-A). Cloud-water and rainwater (wet-only) samples were collected during June 2007-Dec. 2010. Concentrations of major anions and cations were determined. Ion concentrations were generally higher (NO3-, about 8 times; SO42- and K+, 5 times; NH4+ times and Cl-, Na+, Ca2+, Mg2+ 3 times) in cloud-water samples than in rainwater samples collected during the same days. The average pH of cloud-water samples was 6.0 with about 20% of the values below 5.6 and only 4% less than 5.0. Despite high concentrations of SO42- and NO3- the cloud water samples were on average not more acidic than rainwater samples. This is different from most of the other studies of cloud-water composition which have noted a substantially higher acidity (i.e. lower pH) in cloud-water than in rainwater. The slightly alkaline (pH > 5.6) nature of the cloud-water samples is mainly due to the presence of soil derived calcium carbonate in quantities more than enough to neutralize the acids or their precursors. A separation of the cloud-water data into trajectory groups showed that samples in air-masses having spent the last few days over the Indian sub-continent were in general more acidic (due to anthropogenic emissions) than those collected during days with air-masses of marine origin. A high correlation mutually between Ca2+, Na+, NO3- and SO42- makes it difficult to estimate the contribution to SO42- from different sources. Anthropogenic SO2- emissions and soil dust may both give important contributions.
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- De Geer, Lars-Erik, et al.
(författare)
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A Nuclear Jet at Chernobyl Around 21:23:45 UTC on April 25, 1986
- 2018
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Ingår i: Nuclear Technology. - : Informa UK Limited. - 0029-5450 .- 1943-7471. ; 201:1, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- The nature of two explosions that were witnessed within 3 s at the Chernobyl-4 reactor less than a minute after 21:23:00 UTC on April 25, 1986, have since then been the subject of sprawling interpretations. This paper renders the following hypothesis. The first explosion consisted of thermal neutron mediated nuclear explosions in one or rather a few fuel channels, which caused a jet of debris that reached an altitude of some 2500 to 3000 m. The second explosion would then have been the steam explosion most experts believe was the first one. The solid support for this new scenario rests on two pillars and three pieces of corroborating evidence. The first pillar is that a group at the V. G. Khlopin Radium Institute in then Leningrad on April 29, 1986, detected newly produced, or fresh, xenon fission products at Cherepovets, 370 km north of Moscow and far away from the major track of Chernobyl debris ejected by the steam explosion and subsequent fires. The second pillar is built on state-of-the-art meteorological dispersion calculations, which show that the fresh xenon signature observed at Cherepovets was only possible if the injection altitude of the fresh debris was considerably higher than that of the bulk reactor core releases that turned toward Scandinavia and central Europe. These two strong pieces of evidence are corroborated by what were manifest physical effects of a downward jet in the southeastern part of the reactor, by seismic measurements some 100 km west of the reactor, and by observations of a blue flash above the reactor a few seconds after the first explosion.
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- Gustafsson, Örjan, et al.
(författare)
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Brown clouds over South Asia: Biomass or fossil fuel combustion?
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 323:23 January, s. 495-498
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Tidskriftsartikel (refereegranskat)abstract
- Carbonaceous aerosols cause strong atmospheric heating and large surface cooling that is as important to South Asian climate forcing as greenhouse gases, yet the aerosol sources are poorly understood. Emission inventory models suggest that biofuel burning accounts for 50 to 90% of emissions, whereas the elemental composition of ambient aerosols points to fossil fuel combustion. We used radiocarbon measurements of winter monsoon aerosols from western India and the Indian Ocean to determine that biomass combustion produced two-thirds of the bulk carbonaceous aerosols, as well as one-half and two-thirds of two black carbon subfractions, respectively. These constraints show that both biomass combustion (such as residential cooking and agricultural burning) and fossil fuel combustion should be targeted to mitigate climate effects and improve air quality.
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- Kleman, Johan, et al.
(författare)
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Rubbat förtroende för forskarna
- 2010
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Ingår i: Svenska Dagbladet. - 1101-2412. ; :25 maj
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Tidskriftsartikel (populärvet., debatt m.m.)
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