High-resolution provenance of desert dust deposited on Mt. Elbrus, Caucasus in 2009–2012 using snow pit and firn core records

The first record of dust deposition events on Mt. Elbrus, Caucasus Mountains derived from a snow pit and a shallow firn core is presented for the 2009–2012 period. A combination of isotopic analysis, SEVIRI red-greenblue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analyses of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 20–100 km) resolution. Seventeen dust deposition events were detected; fourteen occurred in March–June, one in February and two in October. Four events originated in the Sahara, predominantly in northeastern Libya and eastern Algeria. Thirteen events originated in the Middle East, in the Syrian Desert and northern Mesopotamia, from a mixture of natural and anthropogenic sources. Dust transportation from Sahara was associated with vigorous Saharan depressions, strong surface winds in the source region and mid-tropospheric southwesterly flow with daily winds speeds of 20–30 m s−1 at 700 hPa level. Although these events were less frequent than those originating in the Middle East, they resulted in higher dust concentrations in snow. Dust transportation from the Middle East was associated with weaker depressions forming over the source region, high pressure centred over or extending towards the Caspian Sea and a weaker southerly or southeasterly flow towards the Caucasus Mountains with daily wind speeds of 12–18 m s−1 at 700 hPa level. Higher concentrations of nitrates and ammonium characterised dust from the Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 µm and 4.16 µm. Most samples were characterised by modal values of 2.0– 2.8 µm with an average of 2.6 µm and there was no signifi- cant difference between dust from the Sahara and the Middle East

The Great Acceleration of fragrances and PAHs archived in an ice core from Elbrus, Caucasus

The Great Acceleration of the anthropogenic impact on the Earth system is marked by the ubiquitous distribution of anthropogenic materials throughout the global environment, including technofossils, radionuclides and the exponential increases of methane and carbon dioxide concentrations. However, personal care products as direct tracers of human domestic habits are often overlooked. Here, we present the first research combining fragrances, as novel personal care products, and polycyclic aromatic hydrocarbons (PAHs) as combustion and industrial markers, across the onset of the Great Acceleration in the Elbrus, Caucasus, ice core. This archive extends from the 1930s to 2005, spanning the profound changes in the relationship between humans and the environment during the twentieth century. Concentrations of both fragrances and PAHs rose throughout the considered period, reflecting the development of the Anthropocene. However, within this rising trend, remarkable decreases of the tracers track the major socioeconomic crises that occurred in Eastern Europe during the second half of the twentieth century

Direct characterization of circulating DNA in blood plasma using μLAS technology

Circulating cell-free DNA (cfDNA) is a powerful cancer biomarker for establishing targeted therapies or monitoring patients' treatment. However, current cfDNA characterization is severely limited by its low concentration, requiring the extensive use of amplification techniques. Here we report that the μLAS technology allows us to quantitatively characterize the size distribution of purified cfDNA in a few minutes, even when its concentration is as low as 1 pg/μL. Moreover, we show that DNA profiles can be directly measured in blood plasma with a minimal conditioning process to speed up considerably speed up the cfDNA analytical chain

Пути дальнего переноса пыли на ледники Кавказа и химический состав снега на Западном плато Эльбруса

We present and discuss the chronology of dust deposition events documented by the shallow firn and ice cores extracted on the Western Plateau, Mt. Elbrus (5150 m a.s.l.) in 2009, 2012 and 2013. Snow and ice samples were analysed for major ions and minor element concentrations including heavy metals. Dust layers are formed on the surface of the glaciers as a result of atmospheric transport of mineral dust and aerosol particles to the Caucasus region. Satellite imagery (SEVIRI), trajectory models, and meteorological data were used for accurate dating of each the dust layers revealed in the ice cores. Then we tried to determine origins of the dust clouds and to investigate their transport pathways with high resolution (50–100 km). It was found that the desert dust is deposited on Caucasus glaciers 3–7 times in a year and it comes mainly from deserts of the Middle East and more rarely from the Northern Sahara desert. For the first time average annual dust flux (264 µg/cm2 per a year) and average mass concentration (1.7 mg/kg) over the period 2007–2013 were calculated for this region. The deposition of dust resulted in elevated concentrations consists of mostly ions, especially Ca2+, Mg2+, K+, and sulphates. Dust originated from various sources in the Middle East, including Mesopotamia, or similar dust clouds passing over the Middle East are characterised by high concentrations of nitrates and ammonia that may be related to atmospheric transport of ammonium from agricultural lands that may explain high concentrations of ammonium in the dust originating from this region. Mean values of crustal enrichment factors (EF) for the measured minor elements including heavy metals were calculated. We believe that high content of Cu, Zn and Cd can be a result of possible contribution from anthropogenic sources. Studies of the Caucasus ice cores may allow obtaining new independent data on the atmosphere circulation and high-altitude environment of this region.Исследованы образцы из снежных шурфов и керна из неглубоких скважин, пробуренных на Западном плато Эльбруса на высоте 5100 м в 2009, 2012 и 2013 гг. Образцы снега и льда проанализированы на содержание основных соединений и микроэлементов, включая тяжёлые металлы. В результате переноса минеральных частиц на ледники Кавказа в снежно-фирновой толще формируются отчётливо различимые горизонты загрязнения. Анализ космических снимков SEVIRI, полей оптической толщины атмосферы, траекторий движения воздушных масс и метеорологических данных позволил определить первичные источники минеральных частиц для переноса пыли с высокой точностью (50–100 км). Cоставлена хронология событий переноса пыли. Установлено, что такие явления происходят на Кавказе 3–7 раз в год. Пыль принесена на ледники Эльбруса с Ближнего Востока и из Северной Африки. Выполнено первое для Кавказа прямое определение количества твёрдого вещества, выпадающего из атмосферы на поверхность на больших высотах – 264 мкг/см2 в год. Химический анализ образцов снега из горизонтов загрязнения, образовавшихся в 2009 г., показал высокое содержание нитратов, аммония и сульфатов, что связано с поступлением пыли из сельскохозяйственных районов в Месопотамии. Обнаружено повышенное содержание Cu, Zn и Cd по сравнению с естественным фоном, что может указывать на повышенный региональный фон этих элементов в Северной Африке и на Ближнем Востоке, а также на вероятный вклад антропогенных аэрозолей.

Source apportionment study on particulate air pollution in two high-altitude Bolivian cities: La Paz and El Alto

La Paz and El Alto are two fast-growing, high-altitude Bolivian cities forming the second-largest metropolitan area in the country. Located between 3200 and 4050 m a.s.l. (above sea level), these cities are home to a burgeoning population of approximately 1.8 million residents. The air quality in this conurbation is heavily influenced by urbanization; however, there are no comprehensive studies evaluating the sources of air pollution and their health impacts. Despite their proximity, the substantial variation in altitude, topography, and socioeconomic activities between La Paz and El Alto result in distinct sources, dynamics, and transport of particulate matter (PM). In this investigation, PM10 samples were collected at two urban background stations located in La Paz and El Alto between April 2016 and June 2017. The samples were later analyzed for a wide range of chemical species including numerous source tracers (OC, EC, water-soluble ions, sugar anhydrides, sugar alcohols, trace metals, and molecular organic species). The United States Environmental Protection Agency (U.S. EPA) Positive Matrix Factorization (PMF v.5.0) receptor model was employed for the source apportionment of PM10. This is one of the first source apportionment studies in South America that incorporates an extensive suite of organic markers, including levoglucosan, polycyclic aromatic hydrocarbons (PAHs), hopanes, and alkanes, alongside inorganic species. The multisite PMF resolved 11 main sources of PM. The largest annual contribution to PM10 came from the following two major sources: the ensemble of the four vehicular emissions sources (exhaust and non-exhaust), accountable for 35 % and 25 % of the measured PM in La Paz and El Alto, respectively; and dust, which contributed 20 % and 32 % to the total PM mass. Secondary aerosols accounted for 22 % (24 %) in La Paz (El Alto). Agricultural smoke resulting from biomass burning in the Bolivian lowlands and neighboring countries contributed to 9 % (8 %) of the total PM10 mass annually, increasing to 17 % (13 %) between August–October. Primary biogenic emissions were responsible for 13 % (7 %) of the measured PM10 mass. Additionally, a profile associated with open waste burning occurring from May to August was identified. Although this source contributed only to 2 % (5 %) of the total PM10 mass, it constitutes the second largest source of PAHs, which are compounds potentially hazardous to human health. Our analysis additionally resolved two different traffic-related factors, a lubricant source (not frequently identified), and a non-exhaust emissions source. Overall, this study demonstrates that PM10 concentrations in La Paz and El Alto region are predominantly influenced by a limited number of local sources. In conclusion, to improve air quality in both cities, efforts should primarily focus on addressing dust, traffic emissions, open waste burning, and biomass burning.</p

Pressure is not a state function for generic active fluids

Pressure is the mechanical force per unit area that a confined system exerts on its container. In thermal equilibrium, it depends only on bulk properties (density, temperature, etc.) through an equation of state. Here we show that in a wide class of active systems the pressure depends on the precise interactions between the active particles and the confining walls. In general, therefore, active fluids have no equation of state, their mechanical pressures exhibit anomalous properties that defy the familiar thermodynamic reasoning that holds in equilibrium. The pressure remains a function of state, however, in some specific and well-studied active models that tacitly restrict the character of the particle-wall and/or particle-particle interactions.Comment: 8 pages + 9 SI pages, Nature Physics (2015

Notes on factorization algebras, factorization homology and applications

These notes are an expanded version of two series of lectures given at the winter school in mathematical physics at les Houches and at the Vietnamese Institute for Mathematical Sciences. They are an introduction to factorization algebras, factorization homology and some of their applications, notably for studying $E_n$-algebras. We give an account of homology theory for manifolds (and spaces), which give invariant of manifolds but also invariant of $E_n$-algebras. We particularly emphasize the point of view of factorization algebras (a structure originating from quantum field theory) which plays, with respect to homology theory for manifolds, the role of sheaves with respect to singular cohomology. We mention some applications to the study of mapping spaces and study several examples, including some over stratified spaces.Comment: 122 pages. A few examples adde

Review article of the current state of glaciers in the tropical Andes: a multi-century perspective on glacier evolution and climate change

The aim of this paper is to provide the community with a comprehensive overview of the studies of glaciers in the tropical Andes conducted in recent decades leading to the current status of the glaciers in the context of climate change. In terms of changes in surface area and length, we show that the glacier retreat in the tropical Andes over the last three decades is unprecedented since the maximum extension of the LIA (mid 17th–early 18th century). In terms of changes in mass balance, although there have been some sporadic gains on several glaciers, we show that the trend has been quite negative over the past 50 yr, with a mean mass balance deficit for glaciers in the tropical Andes that is slightly more negative than the computed global average. A break point in the trend appeared in the late 1970s with mean annual mass balance per year decreasing from −0.2m w.e. in the period 1964–1975 to −0.76m w.e. in the period 1976–2010. In addition, even if glaciers are currently retreating everywhere in the tropical Andes, it should be noted that as a percentage, this is much more pronounced on small glaciers at low altitudes that do not have a permanent accumulation zone, and which could disappear in the coming years/decades. Monthly mass balance measurements performed in Bolivia, Ecuador and Colombia showed that variability of the surface temperature of the Pacific Ocean is the main factor governing variability of the mass balance variability at the interannual to decadal time scale. Precipitation did not display a significant trend in the tropical Andes in the 20th century, and consequently cannot explain the glacier recession. On the other hand, temperature increased at a significant rate of 0.10◦Cdecade−1 in the last 70 yr. The higher frequency of El Nin ̃o events and changes in its spatial and temporal occurrence since the late 1970s together with a warming troposphere over the tropical Andes may thus explain much of the recent dramatic shrinkage of glaciers in this part of the world