Hybrid Targeted/Untargeted Screening Method for the Determination of Wildfire and Water-Soluble Organic Tracers in Ice Cores and Snow.

Wildfires can influence the earth's radiative forcing through the emission of biomass-burning aerosols. To better constrain the impacts of wildfires on climate and understand their evolution under future climate scenarios, reconstructing their chemical nature, assessing their past variability, and evaluating their influence on the atmospheric composition are essential. Ice cores are unique to perform such reconstructions representing archives not only of past biomass-burning events but also of concurrent climate and environmental changes. Here, we present a novel methodology for the quantification of five biomass-burning proxies (syringic acid, vanillic acid, vanillin, syringaldehyde, and p-hydroxybenzoic acid) and one biogenic emission proxy (pinic acid) using solid phase extraction (SPE) and ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry. This method was also optimized for untargeted screening analysis to gain a broader knowledge about the chemical composition of organic aerosols in ice and snow samples. The method provides low detection limits (0.003-0.012 ng g-1), high recoveries (74 ± 10%), and excellent reproducibility, allowing the quantification of the six proxies and the identification of 313 different molecules, mainly constituted by carbon, hydrogen, and oxygen. The effectiveness of two different sample storage strategies, i.e., re-freezing of previously molten ice samples and freezing of previously loaded SPE cartridges, was also assessed, showing that the latter approach provides more reproducible results

Antarctic ozone hole modifies iodine geochemistry on the Antarctic Plateau

Polar stratospheric ozone has decreased since the 1970s due to anthropogenic emissions of chlorofluorocarbons and halons, resulting in the formation of an ozone hole over Antarctica. The effects of the ozone hole and the associated increase in incoming UV radiation on terrestrial and marine ecosystems are well established; however, the impact on geochemical cycles of ice photoactive elements, such as iodine, remains mostly unexplored. Here, we present the first iodine record from the inner Antarctic Plateau (Dome C) that covers approximately the last 212 years (1800-2012 CE). Our results show that the iodine concentration in ice remained constant during the pre-ozone hole period (1800-1974 CE) but has declined twofold since the onset of the ozone hole era (~1975 CE), closely tracking the total ozone evolution over Antarctica. Based on ice core observations, laboratory measurements and chemistry-climate model simulations, we propose that the iodine decrease since ~1975 is caused by enhanced iodine re-emission from snowpack due to the ozone hole-driven increase in UV radiation reaching the Antarctic Plateau. These findings suggest the potential for ice core iodine records from the inner Antarctic Plateau to be as an archive for past stratospheric ozone trends.Fil: Spolaor, Andrea. Consiglio Nazionale Delle Ricerche. Istituto Di Scienze Polari.; Italia. Universita' Ca' Foscari Di Venezia; ItaliaFil: Burgay, François. Universita' Ca' Foscari Di Venezia; Italia. Paul Scherrer Institute; SuizaFil: Fernandez, Rafael Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Interdisciplinario de Ciencias Básicas. - Universidad Nacional de Cuyo. Instituto Interdisciplinario de Ciencias Básicas; ArgentinaFil: Turetta, Clara. Consiglio Nazionale Delle Ricerche. Istituto Di Scienze Polari.; Italia. Universita' Ca' Foscari Di Venezia; ItaliaFil: Cuevas, Carlos A.. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Kim, Kitae. Korea Polar Research Institute; Corea del SurFil: Kinnison, Douglas E.. National Center for Atmospheric Research; Estados UnidosFil: Lamarque, Jean-François. National Center for Atmospheric Research; Estados UnidosFil: de Blasi, Fabrizio. Consiglio Nazionale Delle Ricerche. Istituto Di Scienze Polari.; Italia. Universita' Ca' Foscari Di Venezia; ItaliaFil: Barbaro, Elena. Consiglio Nazionale Delle Ricerche. Istituto Di Scienze Polari.; Italia. Universita' Ca' Foscari Di Venezia; ItaliaFil: Corella, Juan Pablo. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Vallelonga, Paul. Universidad de Copenhagen; Dinamarca. University of Western Australia; AustraliaFil: Frezzotti, Massimo. Università Roma Tre Iii. Dipartimento Di Scienze.; ItaliaFil: Barbante, Carlo. Consiglio Nazionale Delle Ricerche. Istituto Di Scienze Polari.; Italia. Universita' Ca' Foscari Di Venezia; ItaliaFil: Saiz López, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; Españ

Long-term spectral and timing properties of the soft gamma-ray repeater SGR 1833-0832 and detection of extended X-ray emission around the radio pulsar PSR B1830-08

SGR 1833-0832 was discovered on 2010 March 19 thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, Rossi X-ray Timing Explorer, and XMM-Newton. Using these data, which span about 225 days, we studied the long-term spectral and timing characteristics of SGR 1833-0832. We found evidence for diffuse emission surrounding SGR 1833-0832, which is most likely a halo produced by the scattering of the point source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT=1.2 keV and absorbing column nH=(10.4+/-0.2)E22 cm^-2, while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at about 3.7E-12 erg/cm^2/s for the first 20 days after the onset of the bursting episode, then it faded by a factor 40 in the subsequent 140 days, following a power-law trend with index alpha=-0.5. We obtained a phase-coherent timing solution with the longest baseline (225 days) to date for this source which, besides period P=7.5654084(4) s and period derivative dP/dt=3.5(3)E-12 s/s, includes higher order period derivatives. We also report on our search of the counterpart to the SGR at radio frequencies using the Australia Telescope Compact Array and the Parkes radio telescope. No evidence for radio emission was found, down to flux densities of 0.9 mJy (at 1.5 GHz) and 0.09 mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs.Comment: 12 pages, 7 colour figures and 3 tables, accepted for publication in MNRAS. Figure 6 in reduced quality and abstract abridged for astro-ph submissio

The seasonal change of PAHs in Svalbard surface snow

The Arctic region is threatened by contamination deriving from both long-range pollution and local human activities. Polycyclic Aromatic Hydrocarbons (PAHs) are environmental tracers of emission, transport and deposition processes. A first campaign has been conducted at Ny-Ålesund, Svalbard, from October 2018 to May 2019, monitoring weekly concentrations of PAHs in Arctic surface snow. The trend of the 16 high priority PAH compounds showed that long-range inputs occurred mainly in the winter, with concentrations ranging from 0.8 ng L−1 to 37 ng L−1. In contrast to this, the most abundant analyte retene, showed an opposite seasonal trend with highest values in autumn and late spring (up to 97 ng L−1), while in winter this compound remained below 3 ng L−1. This is most likely due to local contributions from outcropping coal deposits and stockpiles. Our results show a general agreement with the atmospheric signal, although significant skews can be attributed to post-depositional processes, wind erosion, melting episodes and redistribution

200-year ice core bromine reconstruction at Dome C (Antarctica): observational and modelling results

15 pags., 4 figs., 2 tabs.Bromine enrichment (Brenr) has been proposed as an ice core proxy for past sea-ice reconstruction. Understanding the processes that influence bromine preservation in the ice is crucial to achieve a reliable interpretation of ice core signals and to potentially relate them to past sea-ice variability. Here, we present a 210 years bromine record that sheds light on the main processes controlling bromine preservation in the snow and ice at Dome C, East Antarctic plateau. Using observations alongside a modelling approach, we demonstrate that the bromine signal is preserved at Dome C and it is not affected by the strong variations in ultraviolet radiation reaching the Antarctic plateau due to the stratospheric ozone hole. Based on this, we investigate whether the Dome C Brenr record can be used as an effective tracer of past Antarctic sea ice. Due to the limited time window covered by satellite measurements and the low sea-ice variability observed during the last 30 years in East Antarctica, we cannot fully validate Brenr as an effective proxy for past sea-ice reconstructions at Dome C.This research has been supported by the Horizon 2020 (Beyond EPICA; grant no. 815384), by the Programma Nazionale per la Ricerca in Antartide (PNRA; project no. PNRA16_00295), and by the bilateral international exchange award Royal Society (UK)-CNR, titled “Antarctic sea-ice history: developing robust ice core proxies” (grant no. IEC/R2/202110), awarded to Rachael H. Rhodes and Andrea Spolaor.Peer reviewe

Detection of ice core particles via deep neural networks

Insoluble particles in ice cores record signatures of past climate parameters like vegetation dynamics, volcanic activity, and aridity. For some of them, the analytical detection relies on intensive bench microscopy investigation and requires dedicated sample preparation steps. Both are laborious, require in-depth knowledge, and often restrict sampling strategies. To help overcome these limitations, we present a framework based on flow imaging microscopy coupled to a deep neural network for autonomous image classification of ice core particles. We train the network to classify seven commonly found classes, namely mineral dust, felsic and mafic (basaltic) volcanic ash grains (tephra), three species of pollen (Corylus avellana, Quercus robur, Quercus suber), and contamination particles that may be introduced onto the ice core surface during core handling operations. The trained network achieves 96.8 % classification accuracy at test time. We present the system's potential and its limitations with respect to the detection of mineral dust, pollen grains, and tephra shards, using both controlled materials and real ice core samples. The methodology requires little sample material, is non-destructive, fully reproducible, and does not require any sample preparation procedures. The presented framework can bolster research in the field by cutting down processing time, supporting human-operated microscopy, and further unlocking the paleoclimate potential of ice core records by providing the opportunity to identify an array of ice core particles. Suggestions for an improved system to be deployed within a continuous flow analysis workflow are also presented

Fe²⁺ in ice cores as a new potential proxy to detect past volcanic eruptions

Volcanic eruptions are widely used in ice core science to date or synchronize ice cores. Volcanoes emit large amounts of SO₂ that is subsequently converted inthe atmosphere into sulfuric acid/sulphate.Its discrete and continuous quantification is currently used to determine the ice layers impacted by volcanic emissions, but available high-resolution sulphate quantification methods in ice core (Continuous Flow Analysis (CFA)) struggle with insufficient sensitivity. Here, we present a new high-resolution CFA chemiluminescence method for the continuous determination of Fe²⁺ species in ice cores thatshowsclear Fe²⁺ peaks concurrent with volcanicsulphate peaks in the ice core record. The method, applied on a Greenland ice core, correctly identifies all volcanic eruptions from between 1588 to 1611 and from 1777 to 1850. The method has a detection limit of ∽5pgg⁻¹ and a quadratic polynomial calibration range of up to at least 1760 pg g⁻¹. Our results show that Fe²⁺ is a suitable proxy for identifying past volcanic events

Dust in snow cores: an integrated study on an Italian alpine glacier

On a global scale, mineral dust accounts for the major contribution to the mass load of airborne particles in the atmosphere. It consists of micron-sized minerals mainly deflated from arid and semiarid regions by eolian processes. It can affect glaciers reducing the albedo and it can transform the snowpack leading the formation of melting-refreezing crusts and hoar crystals weak layers. To evaluate these processes, snow and ice cores provide a privileged archive to reconstruct the Earth’s past atmospheric composition. Moreover, they can be powerful tools to assess the impact of human activities on the environment, also enabling albedo evaluation and avalanches forecasting. For these reasons we performed, for the first time, an integrated study on three shallow firn cores (3-4 m long), representative of the previous winter season, collected in June 2015, 2016, and 2017 on the top of the Rutor glacier (Aosta Valley, Italy, 46.637° N, 7.016° E - 3200 m a.s.l.). On these cores we carried out the optical characterization at the EuroCold laboratory (University of Milano-Bicocca) and chemical analyses at the Institute of Polar Science and Ca’ Foscari University of Venice. The physical quantities were analyzed with the SPES (Single Particle Extinction and Scattering) method and with a hyperspectral imaging device. The results were related to the stratigraphic data and compared to the chemical analysis. The SPES method provides extinction cross-section and optical thickness of single particles and their relative concentration in each sample. The particle-by-particle approach and the simultaneous measurement of two optical parameters for each particle pave the way for characterizing the samples avoiding the problem of inverting the particle size distribution. Moreover, from the two dimensional distribution, absorbing particles can be isolated in each sample. Furthermore, the snow cores were analyzed by a non-destructive hyperspectral imaging device to quantify the Aerosol Optical Depth (AOD) and other optical parameters of the snow useful for albedo evaluation. To better assess the particle sources, on the same samples a high temporal-resolution chemical analysis was performed. Specifically, we found that Levoglucosan, a key biomass burning tracer, is mildly correlated with the AOD anomalies, whereas Polycyclic Aromatic Hydrocarbon (PAH) diagnostic ratios clearly suggest their pyrogenic origin from combustion sources. The integration of the chemical results, together with the physical properties of the particles, can provide a detailed characterization of the glacier. This is important for the determination of the anthropogenic contamination and the snow ablation linked to climate changes

Sea ice fluctuations in the Baffin Bay and the Labrador Sea during glacial abrupt climate changes

Sea ice decline in the North Atlantic and Nordic Seas has been proposed to contribute to the repeated abrupt atmospheric warmings recorded in Greenland ice cores during the last glacial period, known as Dansgaard-Oeschger (D-O) events. However, the understanding of how sea ice changes were coupled with abrupt climate changes during D-O events has remained incomplete due to a lack of suitable high-resolution sea ice proxy records from northwestern North Atlantic regions. Here, we present a subdecadal-scale bromine enrichment (Brenr) record from the NEEM ice core (Northwest Greenland) and sediment core biomarker records to reconstruct the variability of seasonal sea ice in the Baffin Bay and Labrador Sea over a suite of D-O events between 34 and 42 ka. Our results reveal repeated shifts between stable, multiyear sea ice (MYSI) conditions during cold stadials and unstable, seasonal sea ice conditions during warmer interstadials. The shift from stadial to interstadial sea ice conditions occurred rapidly and synchronously with the atmospheric warming over Greenland, while the amplitude of high-frequency sea ice fluctuations increased through interstadials. Our findings suggest that the rapid replacement of widespread MYSI with seasonal sea ice amplified the abrupt climate warming over the course of D-O events and highlight the role of feedbacks associated with late-interstadial seasonal sea ice expansion in driving the North Atlantic ocean–climate system back to stadial conditions

Towards an interdisciplinary characterization of the Rutor glacier (Aosta Valley)

The Rutor Glacier is located in the upper part of La Thuile valley, Italy (46.637° N, 7.016° E, area 7.5 km2, length 3.8 km, elevation between 2600-3420 m). It is one of the ten biggest glaciers in Italian Alps. Its basin is bound to the south-west by French/Italian border and the accumulation area is open to the western (Atlantic) fluxes. Three shallow firn cores (3-4 m long), representative of the previous winter season, were collected in June 2015, 2016, and 2017 on the top of the glacier. Samples were divided into two aliquots for physical analyses at the EuroCold laboratory of the University of Milano-Bicocca and for chemical analyses at the Institute of Polar Sciences and Ca’ Foscari University of Venice. The optical characterization has been carried out at EuroCold with the SPES method, which provides the extinction cross-section and optical thickness of single particles, as well as the relative concentration of particles in each sample. These physical quantities were related to the stratigraphic data and compared to the chemical analyses. The particle-by-particle approach and the simultaneous measurement of two optical parameters allow sample characterization beyond the measurement of their particle size distribution. Moreover, from the two-dimensional distribution, absorbing particles can be isolated in each sample; samples exhibiting contamination or melting and refreezing are easily recognized. The chemical analyses were devoted to the quantification of inorganic and organic species. We focused on the high-temporal resolution quantification of heavy metals, crustal elements, and Levoglucosan as biomass burning tracer, and on the year-averaged quantification of a set of organic contaminants (PFASs and their precursors, PAHs, PBDEs, PCBs, PCDD/Fs), providing the first comprehensive environmental quality study of the Rutor Glacier. The integration of the chemical results with the physical properties of the particles and future back-trajectory studies will be introductory for the determination of the contamination sources that affect the Rutor Glacier during winters. Moreover, the quantification of the organic pollutants in the ice will provide preliminary indications on their potential release in the environment under a global warming scenario