Analytical Chemistry in High-Alpine Environmental Research

Snow and ice chemistry studies in the high-altitude regions of the Alps give insight into present and past atmospheric chemistry. Impurities found in snow originate from atmospheric aerosol particles or reactive trace gases and, thus, represent a broad spectrum of chemical species such as water-soluble inorganic and organic ions, insoluble minerals, organic components, soot, trace metals, etc. Consequently, a variety of analytical techniques need to be applied in snow chemistry studies, including ion chromatography, inductively coupled plasma optical emission or mass spectrometry, atomic absorption spectrometry etc. A few details of the respective methods used in our laboratory are discussed here. Since snow samples are characterised by low impurity concentrations, they are particularly sensitive with respect to stability and contamination. Thus, special care in sample handling is required. Investigations of the geographical, seasonal and year-to-year variations of the concentrations and deposition fluxes of major ionic species were carried out in the Alps. Concentrations of ammonium, nitrate and sulphate showed a West to East increase, which was, however, not reflected in the total flux, since precipitation heights exhibited an opposite pattern. Long-term records from an alpine glacier revealed substantial increases of sulphate, ammonium, nitrate, and lead in the course of the last 100 years

Spectral Signatures of Submicron Scale Light-Absorbing Impurities in Snow and Ice Using Hyperspectral Microscopy

Light-absorbing impurities (LAI) can darken snow and ice surfaces, reduce snow/ice albedo and accelerate melt. Efforts to allocate the relative contribution of different LAI to snow/ice albedo reductions have been limited by uncertainties in the optical properties of LAI. We developed a new method to measure LAI spectral reflectance at the submicron scale by modifying a Hyperspectral Imaging Microscope Spectrometer (HIMS). We present the instrument’s internal calibration, and the overall small influence of a particle’s orientation on its measured reflectance spectrum. We validated this new method through the comparison with a field spectroradiometer by measuring different standard materials. Measurements with HIMS at the submicron scale and the bulk measurements of the same standard materials with the field pectroradiometer are in good agreement with an average deviation between the spectra of 3.2% for the 400–1000 nm wavelength range. The new method was used (1) to identify BC (black carbon), mineral dust including hematite and the humic substances present in an environmental sample from Plaine Morte glacier and (2) to collect the individual reflectance spectra of each of these types of impurity. The results indicate that this method is applicable to heterogeneous samples such as the LAI found in snow and ice

Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps

Crystal orientation fabric (COF) analysis provides information about the c-axis orientation of ice grains and the associated anisotropy and microstructural information about deformation and recrystallisation processes within the glacier. This information can be used to introduce modules that fully describe the microstructural anisotropy or at least direction-dependent enhancement factors for glacier modelling. The COF was studied at an ice core that was obtained from the temperate Rhonegletscher, located in the central Swiss Alps. Seven samples, extracted at depths between 2 and 79 m, were analysed with an automatic fabric analyser. The COF analysis revealed conspicuous four-maxima patterns of the c-axis orientations at all depths. Additional data, such as microstructural images, produced during the ice sample preparation process, were considered to interpret these patterns. Furthermore, repeated high-precision global navigation satellite system (GNSS) surveying allowed the local glacier flow direction to be determined. The relative movements of the individual surveying points indicated longitudinal compressive stresses parallel to the glacier flow. Finally, numerical modelling of the ice flow permitted estimation of the local stress distribution. An integrated analysis of all the data sets provided indications and suggestions for the development of the four-maxima patterns. The centroid of the four-maxima patterns of the individual core samples and the coinciding maximum eigenvector approximately align with the compressive stress directions obtained from numerical modelling with an exception for the deepest sample. The clustering of the c axes in four maxima surrounding the predominant compressive stress direction is most likely the result of a fast migration recrystallisation. This interpretation is supported by air bubble analysis of large-area scanning macroscope (LASM) images. Our results indicate that COF studies, which have so far predominantly been performed on cold ice samples from the polar regions, can also provide valuable insights into the stress and strain rate distribution within temperate glaciers

High-altitude glacier archives lost due to climate change-related melting.

Global warming has caused widespread surface lowering of mountain glaciers. By comparing two firn cores collected in 2018 and 2020 from Corbassière glacier in Switzerland, we demonstrate how vulnerable these precious archives of past environmental conditions have become. Within two years, the soluble impurity records were destroyed by melting. The glacier is now irrevocably lost as an archive for reconstructing major atmospheric aerosol components

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

Aromatic acids in an Arctic ice core from Svalbard: a proxy record of biomass burning

This study presents vanillic acid and parahydroxybenzoic acid levels in an Arctic ice core from Lomonosovfonna, Svalbard covering the past 800 years. These aromatic acids are likely derived from lignin combustion in wildfires and long-range aerosol transport. Vanillic and para-hydroxybenzoic acid are present throughout the ice core, confirming that these compounds are preserved on millennial timescales. Vanillic and para-hydroxybenzoic acid concentrations in the Lomonosovfonna ice core ranged from below the limits of detection to 0.2 and 0.07 ppb, respectively (1 ppb =1000 ng L-1). Vanillic acid levels are high (maximum of 0.1 ppb) from 1200 to 1400 CE, then gradually decline into the twentieth century. The largest peak in the vanillic acid in the record occurs from 2000 to 2008 CE. In the para-hydrobenzoic acid record, there are three centennialscale peaks around 1300, 1550, and 1650 CE superimposed on a long-term decline in the baseline levels throughout the record. Ten-day air mass back trajectories for a decade of fire seasons (March-November, 2006-2015) indicate that Siberia and Europe are the principle modern source regions for wildfire emissions reaching the Lomonosovfonna site. The Lomonosovfonna data are similar to those from the Eurasian Arctic Akademii Nauk ice core during the early part of the record (1220-1400 CE), but the two ice cores diverge markedly after 1400 CE. This coincides with a shift in North Atlantic climate marked by a change of the North Atlantic Oscillation from a positive to a more negative state

Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200–800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700–50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures

A multi-proxy approach for revealing recent climatic changes in the Russian Altai

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ13C and δ18O in cellulose chronologies obtained for the period 1779-2007 and cell wall thickness (CWT) for 1900-2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ13C data contain a strong summer temperature signal, while δ18O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ13C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ18O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstructio

Twentieth-century warming preserved in a Geladaindong mountain ice core, central Tibetan Plateau

High-resolution δ18O records from a Geladaindong mountain ice core spanning the period 1477-1982 were used to investigate past temperature variations in the Yangtze River source region of the central Tibetan Plateau (TP). Annual ice-core δ18O records were positively correlated with temperature data from nearby meteorological stations, suggesting that the δ18O record represented the air temperature in the region. A generally increasing temperature trend over the past 500 years was identified, with amplified warming during the 20th century. A colder stage, spanning before the 1850s, was found to represent the Little Ice Age with colder periods occurring during the 1470s–1500s, 1580s–1660s, 1700s–20s and 1770s–1840s. Compared with other temperature records from the TP and the Northern Hemisphere, the Geladaindong ice-core record suggested that the regional climate of the central TP experienced a stronger warming trend during the 20th century than other regions. In addition, a positive relationship between the Geladaindong δ18O values and the North Atlantic Oscillation index, combined with a wavelet analysis of δ18O records, indicated that there was a potential atmospheric teleconnection between the North Atlantic and the central TP