72 research outputs found
APPLICATION OF INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS ON ICE CORE SAMPLES
A first application of INAA (Instrumental Neutron Activation Analysis) to ice core sample
Mountain glaciers darkening: geochemical characterizazion of cryoconites and their radiative impact on the Vadret da Morteratsch (Swiss Alps)
Mountain glaciers represent an important source of fresh water across the globe. It is well known that these
reservoirs are seriously threatened by global climate change, and a widespread reduction of glacier extension
has been observed in recent years. Surface processes that promote ice melting are driven both by air temperature/precipitation and surface albedo. This latter is mainly influenced by the growth of snow grains and by the
impurities content (such as mineral dust, soot, ash etc.). The origin of these light-absorbing impurities can be local
or distal, and often, as a consequence of melting processes, they can aggregate on the glacier tongue, forming
characteristics cryoconites, that decrease ice albedo and hence promote the melting.
In this contribution, we coupled satellite images (EO1 \u2013 Hyperion and Landsat 8 - OLI) and ground hyperspectral
data (ASD field spectrometer) for characterizing ice and snow surface reflectance of the Vadret da Morteratsch
glacier (Swiss Alps). On the glacier ablation zone, we sampled ice, snow, surface dust and cryoconite material.
To evaluate the possible impact of anthropogenic and natural emissions on cryoconites formation, we determined
their geochemical composition (through the Neutron Activation Analysis, NAA) and the concentration of Black
Carbon (BC), Organic Carbon (OC), Elemental Carbon (EC) and Levoglucosan.
From satellite data, we computed the Snow Darkening Index (SDI), which is non-linearly correlated with dust
content in snow. Results showed that, during 2015 summer season, ice albedo in the ablation zone reached very
low values of about 0.1-0.2. The darkening of the glacier can be attributed to the impact of surface dust (from
lateral moraine and Saharan desert) and cryoconites, coupled with grain growth driven by the extremely warm
2015 summer. The geochemical characterization of non-ice material contained in the cryoconites can provide
important information regarding their source and the possible impact of anthropogenic emissions on cryoconites
formation and evolution
Cryoconite as a temporary sink for anthropogenic species stored in glaciers
Cryoconite, the typical sediment found on the surface of glaciers, is mainly known in relation to its
role in glacial microbiology and in altering the glacier albedo. But if these aspects are relatively well
addressed, the same cannot be said about the geochemical properties of cryoconite and the possible
interactions with glacial and peri-glacial environment. Current glacier retreat is responsible for the
secondary emission of species deposited in high-altitude regions in the last decades. The role played by
cryoconite in relation to such novel geochemical fluxes is largely unknown. Few and scarce observations
suggest that it could interact with these processes, accumulating specific substances, but why, how and
to what extent remain open questions. Through a multi-disciplinary approach we tried to shed lights.
Results reveal that the peculiar composition of cryoconite is responsible for an extreme accumulation
capability of this sediment, in particular for some, specific, anthropogenic substances
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 96.8â% 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
Cryoconite â from minerals and organic matter to bioengineeredsediments on glacier's surfaces
Cryoconite is a mixture of mineral and organic material covering glacial ice, playing important roles in biogeochemical
cycles and lowering the albedo of a glacier surface. Understanding the differences in structure of
cryoconite across the globe can be important in recognizing past and future changes in supraglacial environments
and ice-organisms-minerals interactions. Despite the worldwide distribution and over a century of studies, the
basic characteristics of cryoconite, including its forms and geochemistry, remain poorly studied. The major purpose
of our study is the presentation and description of morphological diversity, chemical and photoautotrophs
composition, and organic matter content of cryoconite sampled from 33 polar and mountain glaciers around the
globe. Observations revealed that cryoconite is represented by various morphologies including loose and granular
forms. Granular cryoconite includes smooth, rounded, or irregularly shaped forms; with some having their
surfaces covered by cyanobacteria filaments. The occurrence of granules increased with the organic matter content
in cryoconite.Moreover, amajor driver of cryoconite colouringwas the concentration of organicmatter and
its interplay with minerals. The structure of cyanobacteria and algae communities in cryoconite differs between
glaciers, but representatives of cyanobacteria families Pseudanabaenaceae and Phormidiaceae, and algae families
Mesotaeniaceae and Ulotrichaceaewere themost common. Themost of detected cyanobacterial taxa are known
to produce polymeric substances (EPS) that may cement granules. Organic matter content in cryoconite varied
between glaciers, ranging from 1% to 38%. The geochemistry of all the investigated samples reflected local sediment
sources, except of highly concentrated Pb andHg in cryoconite collected fromEuropean glaciers near industrialized
regions, corroborating cryoconite as element-specific collector and potential environmental indicator of
anthropogenic activity. Our work supports a notion that cryoconite may bemore than just simple sediment and
instead exhibits complex structure with relevance for biodiversity and the functioning of glacial ecosystem
Atmospheric mineral dust in ice cores: application of Neutron Activation and Synchrotron Radiation X-ray fluorescence
It is estimated that several million of tons of mineral dust are constantly transported in the atmosphere. Such a massive burden has a great influence on many dynamics of our planet, from biogeochemistry, to radiative processes, to sedimentology. An important aspect concerns the tight relationship between dust and climate, at different spatial and temporal scales. Ice cores allowed reconstructing the more detailed and extended records related to atmospheric dust deposition and transport. Measuring the physical and chemical properties of mineral particles, it was possible to understand the influence of climate on the dust cycle and vice versa, i.e. the influence of mineral particles on climate.
In this thesis recent advancements about the understanding of the dust cycle in different contexts (Antarctica and the Alps) will be presented. A significative part of the work is dedicated to the development of new methods for the geochemical investigation of ice cores. Applying these new methods and other established ones, it was possible to draw new insights about the provenance of dust during different climatic periods in Antarctica, focusing on the different response associated to local and distal dust sources in relation to climate changes and on the effect of climate on dust geochemistry. In particular new evidences concern dust properties during Holocene, when dust deposition in Antarctica reaches its lower levels. Turning the attention to the Alps it was possible to highlight the influence of anthropic emission on dust composition, with anomalous values for many elements related to industrial and domestic activities. In addition the construction of a high resolution record allowed studying in detail the phenomenon of Saharan dust deposition in Southern Europe, a process with many and different environmental consequences
- âŚ