Studying seasonal variations in carbonaceous aerosol particles in the atmosphere over central Siberia

The results of 2-year (2010–2012) measurements of the concentrations of organic carbon (OC) and elemental carbon (EC), which were taken at the Zotino Tall Tower Observatory (ZOTTO) Siberian background station (61° N, 89° E), are given. Despite the fact that this station is located far from populated areas and industrial zones, the concentrations of OC and EC in the atmosphere over boreal forests in central Siberia significantly exceed their background values. In winter and fall, high concentrations of atmospheric carbonaceous aerosol particles are caused by the long-range transport (~1000 km) of air masses that accumulate pollutants from large cities located in both southern and southwestern regions of Siberia. In spring and summer, the pollution level is also high due to regional forest fires and agricultural burning in the steppe zone of western Siberia in the Russian–Kazakh border region. Background concentrations of carbonaceous aerosol particles were observed within relatively short time intervals whose total duration was no more than 20% of the entire observation period. In summer, variations in the background concentrations of OC closely correlated with air temperature, which implies that the biogenic sources of organic-particle formation are dominating.     

Colour-differential interferometry for the observation of extrasolar planets

We present the high angular resolution technique of colour-differential interferometry for direct detection of extrasolar giant planets (EGPs). The measurement of differential phase with long-baseline ground-based interferometers in the near-infrared could allow the observation of several hot giant extrasolar planets in tight orbit around the nearby stars, and thus yield their low- or mid-resolution spectroscopy, complete orbital data set and mass. Estimates of potentially achievable signal-to-noise ratios are presented for a number of planets already discovered by indirect methods. The limits from the instrumental and atmospheric instability are discussed, and a subsequent observational strategy is proposed.     

A multi-proxy record of the Last Glacial Maximum and last 14,500?years of paleoenvironmental change at Lone Spruce Pond, southwestern Alaska

Sediment cores from Lone Spruce Pond (60.007°N, 159.143°W), southwestern Alaska, record paleoenvironmental changes during the global Last Glacial Maximum (LGM), and during the last 14,500 calendar years BP (14.5?cal?ka). We analyzed the abundance of organic matter, biogenic silica, carbon, and nitrogen, and the isotope ratios of C and N, magnetic susceptibility, and grain-size distribution of bulk sediment, abundance of alder shrub (Alnus) pollen, and midge (Chironomidae and Chaoboridae) assemblages in a 4.7-m-long sediment sequence from the depocenter at 22?m water depth. The basal unit contains macrofossils dating to 25?C21?cal?ka (the global LGM), and is interpreted as glacial-lacustrine sediment. The open water requires that the outlet of the Ahklun Mountain ice cap had retreated to within 6?km of the range crest. In addition to cladocerans and diatoms, the glacial-lacustrine mud contains chironomids consistent with deep, oligotrophic conditions; several taxa associated with relatively warm conditions are present, suggestive of relative warmth during the global LGM. The glacial-lacustrine unit is separated from the overlying non-glacial lake sediment by a possible disconformity, which might record a readvance of glacier ice. Non-glacial sediment began accumulating around 14.5?cal?ka, with high flux of mineral matter and fluctuating physical and biological properties through the global deglacial period, including a reversal in biogenic-silica (BSi) content during the Younger Dryas (YD). During the global deglacial interval, the ??¹³C values of lake sediment were higher relative to other periods, consistent with low C:N ratios (8), and suggesting a dominant atmospheric CO₂ source of C for phytoplankton. Concentrations of aquatic faunal remains (chironomids and Cladocera) were low throughout the deglacial interval, diversity was low and warm-indicator taxa were absent. Higher production and air temperatures are inferred following the YD, when bulk organic-matter (OM) content (LOI 550?°C) increased substantially and permanently, from 10 to 30?%, a trend paralleled by an increase in C and N abundance, an increase in C:N ratio (to about 12), and a decrease in ??¹³C of sediment. Post-YD warming is marked by a rapid shift in the midge assemblage. Between 8.9 and 8.5?cal?ka, Alnus pollen tripled (25?C75?%), followed by the near-tripling of BSi (7?C19?%) by 8.2?cal?ka, and ??¹⁵N began a steady rise, reflecting the buildup of N and an increase in denitrification in soils. Several chironomid taxa indicative of relatively warm conditions were present throughout the Holocene. Quantitative chironomid-based temperature inferences are complicated by the expansion of Alnus and resulting changes in lake nutrient status and production; these changes were associated with an abrupt increase in cladoceran abundance and persistent shift in the chironomid assemblage. During the last 2,000?years, chironomid-assemblage changes suggest cooler temperatures, and BSi and OM values were generally lower than their maximum Holocene values, with minima during the seventh and eighth centuries, and again during the eighteenth century.     

Changes in soil organic carbon and other physical soil properties along adjacent Mediterranean forest, grassland, and cropland ecosystems in Turkey

Cultivation, overgrazing, and overharvesting are seriously degrading forest and grassland ecosystems in the Taurus Mountains of the southern Mediterranean region of Turkey. This study investigated the effects of changes on soil organic carbon (SOC) content and other physical soil properties over a 12-year period in three adjacent ecosystems in a Mediterranean plateau. The ecosystems were cropland (converted from grasslands in 1990), open forest, and grassland. Soil samples from two depths, 0–10 and 10–20 cm, were collected for chemical and physical analyses at each of cropland, open forest, and grassland ecosystems. SOC pools at the 0–20 cm depth of cropland, forest, and grassland ecosystems were estimated at 32,636, 56,480, and 57,317 kg ha⁻¹, respectively. Conversion of grassland into cropland during the 12-year period increased the bulk density by 10.5% and soil erodibility by 46.2%; it decreased SOM by 48.8%, SOC content by 43%, available water capacity (AWC) by 30.5%, and total porosity by 9.1% for the 0–20 cm soil depth (p<0.001). The correlation matrix revealed that SOC content was positively correlated with AWC, total porosity, mean weight diameter (MWD), forest, and grassland, and negatively with bulk density, pH, soil erodibility factor, and cropland. The multiple regression (MLR) models indicated that any two of the three ecosystems and one of the two soil depths accounted for 86.5% of variation in mean SOC values ((p<0.001).     

Earthquakes in Switzerland and surrounding regions during 2006

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2006. During this period, 572 earthquakes and 91 quarry blasts were detected and located in the region under consideration. Of these earthquakes, two occurred in conjunction with the construction of the new Gotthard railway tunnel and 165 were induced artificially by the stimulation of a proposed geothermal reservoir beneath the city of Basel. With 20 events with M _L ≥ 2.5, five of which were artificially induced, the seismic activity in the year 2006 was far below the average over the previous 31 years. Nevertheless, six events were felt by the public, most prominently the strongest of the induced Basel events (M _L 3.4), which caused some non-structural building damage. Noteworthy are also the two earthquakes near Cortaillod (M _L 3.2), on the shore of Lake Neuchatel, and in Val Mora (M _L 3.5), between the Engadin and Val Müstair, as well as the 42 aftershocks of the M _L 4.9 Vallorcine earthquake, between Martigny and Chamonix, of September 2005. Editorial handling: Stefan Bucher     

The System CaO-CO2-H2O and the Origin of Carbonatites

The ternary isobaric (TX) prism for the system CaO–CO₂–H₂Owas determined at 1,000 bars pressure between 600? C and 1,320?C. At this pressure, calcite melts incongruently at 1,310? C,portlandite (Ca(OH)₂) melts congruently at 835? C, a binaryeutectic exists between calcite and portlandite at 685? C, meltingbegins at 740? C on the join calcite-water and the univariant(isobaric invariant) equilibria lime?calcite?portlandite?liquidand calcite?portlandite?liquid?vapour occur at 683? C and 675?C, respectively. The latter is the minimum liquidus temperaturein the TX prism, and the composition of this liquid is 65CaO,19CO₂, 16H₂O (in weight per cent). PT curves were determinedfor several univariant equilibria. In the binary system CaO-H₂O,four univariant curves meet at an invariant point, at 810? Cand 100 bars pressure. Portlandite dissociates only at pressuresbelow this point. The minimum liquidus temperature in the ternarysystem varies between 685? C and 640? C in the pressure interval27 bars to 4, 000 bars. Liquids in the system are regarded as simplified carbonatitemagmas in which CaO represents the basic oxides, and CO₂ andH₂O the volatile constituents. The liquids have low viscosityas indicated by the rapid attainment of equilibrium and theobservation that crystal settling takes place in 15-min runs.The existence of such liquids at moderate temperatures througha wide pressure range leaves little reason to doubt a magmaticorigin for those carbonatites which appear to be intrusive.Differentiation could occur in multicomponent magmas by separationof the successive liquid fractions produced by crystallizationof calcite, dolomite, and siderite. The determined phase relationsdo not favour an origin by gas transfer. The results also suggestthat partial melting of limestones is likely at igneous contacts,and that impure limestones may be partially melted during high-graderegional metamorphism.     

Holocene evolution of the Canet-St Nazaire lagoon (Golfe du Lion, France) as determined from a study of sediment properties

The sedimentation in the lagoons of the Golfe du Lion coast (Mediterranean Sea, France) records their post-Holocene evolution. The Canet-St Nazaire lagoon provides an example of such an evolution. Eight cores (ranging from 13.5 to 19.7 m in length) from a transect of the lagoon provide a cross-section of the late Quaternary stratigraphy. The sedimentary sequence comprises mud and sand layers. The two sand formations are identified as parts of two distinct shelf-sedimentary prisms. Stratigraphic analysis defines three stages in the recent, muddy infilling, corresponding to the last divisions of the Holocene. Sedimentation rates of the muds, related to climatic and palaeogeomorphological events, largely determine their geotechnical and geochemical properties. It appears, indeed, to be the most important factor in determining the compressibility index, the saturated bulk density and the organic and water contents of the deposits. Subboreal muds, poorly consolidated and rich in organic matter, correspond to a high rate of deposition. In the Subatlantic muds, in contrast, the sedimentation rate is lower whilst there is a decrease in the organic matter and an increase in the degree of cohesion.     

The Zoned Clinopyroxenes of the Shiant Isles Sill, Scotland

The zoned clinopyroxenes in samples from a near-vertical sectionthrough the main Shiant Isles sill have been studied using theelectron microprobe. In terms of Ca: Mg: Fe the over-all fractionationtrend is much greater than had been believed from bulk pyroxeneanalyses and is of a distinctive calcic augite-hedenbergitetype. In this respect it differs from both the augite-ferroaugiteand salite-aegirine trends generally regarded as typical oftholeiitic and alkaline basic magmas respectively, and it isproposed that this trend represents a third major type typicalof mildly alkaline basic magmas. The Al, Ti, and Na contentsof the pyroxenes are dependent on the degree of fractionationas represented by Mg/(Mg+Fe) and it is suggested that the Aland Ti contents are controlled by the Ti content of the liquidand the crystallization of titaniferous magnetite whereas theentry of Na into the pyroxene as aegirine is dependent on theactivity of Fe³⁺ in the liquid. To provide a basis for discussion of the crystallization ofthe zoned clinopyroxenes the existing petrogenetic hypothesesfor the Shiant Isles sill are reviewed and a new model proposedfor its emplacement and differentiation. It is concluded thatthe differences between the pyroxenes of the mildly alkalineShiant Isles sill and those of more strongly alkaline basicmagmas result from fundamental chemical differences in the magma.The lower Ca contents of the early pyroxenes are due to theslightly higher Si activity of the magma and the subsequenttrend towards hedenbergite rather than aegirine is due to crystallizationunder conditions of relatively lower oxygen fugacity, probablyas a result of lower initial H₂O content of the magma.