G. Cozzi

Trace elements in winter snow of the Dolomites (Italy): A statistical study of natural and anthropogenic contributions

Knowledge of the occurrence of trace elements deposited in fresh alpine snow is very limited. Although current sources of major ionic inorganic species have been well established, this is not the case for many trace elements. This manuscript attempts to reconstruct the origin of Ag, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mo, Mn, Pb, Sb, Ti, U, V and Zn in winter surface snow, extensively collected in the Dolomites region (Eastern Alps, Italy). Sampling of surface snow was conducted weekly during the winter 1998 at 21 sites at altitudes ranging from approximately 1000 to approximately 3000 m. This led to a remarkable dataset of trace element concentrations in surface snow from low latitudes. Here we show a preliminary statistical investigation conducted on the 366 samples collected. It was found that V, Sb, Zn, Cd, Mo and Pb have a predominantly anthropogenic origin, linked to the road traffic in the alpine valleys and the nearby heavily industrialised area of the Po Valley. In addition, the occasionally strong Fe and Cr input may reflect the mechanical abrasion of ferrous components of the vehicles. However, much of the Fe along with Mn, U and Ti originates primarily from the geological background of the Dolomites. A marine contribution was found to be negligible for all the trace elements. The origin of other trace elements is less clear: Ag can be possibly attributed to a predominantly anthropogenic origin while Cr, Co, Cu and Ba are usually from crustal rocks but different than the Dolomites.

Direct determination of mercury at the sub-picogram per gram level in polar snow and ice by ICP-SFMS

An analytical method for the direct determination of mercury (Hg) in polar snow and ice cores and surface snow based on inductively coupled plasma sector field mass spectrometry (ICP-SFMS) has been developed. Various Hg isotopes, such as 199Hg, 200Hg, 201Hg and 202Hg, appear to be free of polyatomic interferences in such matrices and allow the measurements to be made in low resolution mode, leading to high sensitivity. Ultra-low concentration Hg standards (from 1.5 to 20 pg g−1) were used for the calibration of the Thermo Finnigan MAT Element2, and a detection limit as low as 0.18 pg g−1 was achieved using 202Hg. Ultra-clean procedures used from field sampling to final laboratory analysis show no significant blank contributions and appear suitable for the reliable determination of Hg at ultra-low concentrations. Precision of the Hg measurements was estimated to be 15% in terms of relative standard deviation on five replicates and accuracy was checked with an analytical reference material (102% recovery). Hg concentrations in surface snow samples from the Northern Hemisphere collected in the Canadian Arctic and in Svalbard (Norway) show high variability (1.2–32.0 pg g−1). In Antarctica, Hg was determined in different ice core sections from Dome C, spanning the last 18000 years BP (range from 0.7 to 3.2 pg g−1), and in snow samples from Coats Land covering the last 150 years (range from 0.2 to 16.1 pg g−1).

Determination of rare earth elements in tomato plants by inductively coupled plasma mass spectrometry techniques

In recent years identification of the geographical origin of food has grown more important as consumers have become interested in knowing the provenance of the food that they purchase and eat. Certification schemes and labels have thus been developed to protect consumers and genuine producers from the improper use of popular brand names or renowned geographical origins. As the tomato is one of the major components of what is considered to be the healthy Mediterranean diet, it is important to be able to determine the geographical origin of tomatoes and tomato-based products such as tomato sauce. The aim of this work is to develop an analytical method to determine rare earth elements (RRE) for the control of the geographic origin of tomatoes. The content of REE in tomato plant samples collected from an agricultural area in Piacenza, Italy, was determined, using four different digestion procedures with and without HF. Microwave dissolution with HNO3 + H2O2 proved to be the most suitable digestion procedure. Inductively coupled plasma quadrupole mass spectrometry (ICPQMS) and inductively coupled plasma sector field plasma mass spectrometry (ICPSFMS) instruments, both coupled with a desolvation system, were used to determine the REE in tomato plants in two different laboratories. A matched calibration curve method was used for the quantification of the analytes. The detection limits (MDLs) of the method ranged from 0.03 ng g(-1) for Ho, Tm, and Lu to 2 ng g(-1) for La and Ce. The precision, in terms of relative standard deviation on six replicates, was good, with values ranging, on average, from 6.0% for LREE (light rare earth elements) to 16.5% for HREE (heavy rare earth elements). These detection limits allowed the determination of the very low concentrations of REE present in tomato berries. For the concentrations of REE in tomato plants, the following trend was observed: roots > leaves > stems > berries.

Iron speciation in aerosol dust influences iron bioavailability over glacial‐interglacial timescales

[1]xa0Iron deposition influences primary production and oceanic sequestration of atmospheric carbon dioxide (CO2). Iron has two oxidation states, Fe(II) and Fe(III), with Fe(II) being more soluble and available for oceanic phytoplankton uptake. The past proportions of soluble iron in aerosol dust remain unknown. Here we present iron speciation (Fe2+ and Fe3+) in the Antarctic Talos Dome ice core over millennial time scales. We demonstrate that iron speciation over the last 55 kyr is linked to increasing quantities of fine dust (FD) (0.7–5u2009µm) and intensified long-range dust transport. We propose that Fe(II) and Fe2+ production is principally enhanced in FD by photoreduction, although pH and organic complexation may also contribute to the speciation dynamics. During the Last Glacial Maximum, Fe2+ concentrations in dust increased by up to seven times more than interglacial levels, while Fe3+ only doubled. Cold and dusty climatic periods may increase the percentage of biologically available Fe(II) and Fe2+ deposited in the nutrient-limited Southern Ocean, allowing greater phytoplankton uptake and perhaps increased CO2 drawdown.

Elemental indicators of natural and anthropogenic aerosol inputs to Law Dome, Antarctica

Abstract A selection of elements (Bi, Ca, Cd, Co, Cu, Mn, Na, Sr, U, V, Zn) were measured by high-resolution inductively coupled plasma sector-field mass spectrometry in firn- and ice-core samples from Law Dome, Antarctica, corresponding to the period 4500 BC to AD 1989. Concentrations of rock dust and sea salts were calculated for each sample and then used to determine concentrations of each element originating from crustal and marine aerosol emissions, respectively. Where calculated contributions from crustal and marine aerosol sources failed to account for the total measured concentration of an element, the remainder was apportioned to volcanic and/or anthropogenic sources and defined as an enrichment. On this basis, it was determined that Bi and Cd concentrations in Law Dome ice are overwhelmingly influenced by volcanic emissions (enrichments 150–250x crustal and marine inputs); Co, Cu, Pb and Zn concentrations in Law Dome ice are largely influenced by volcanic emissions (enrichments 16–36x crustal and marine inputs); and Mn, Sr, U and V concentrations in Law Dome ice are minimally influenced by volcanic emissions (enrichments 1.5–4x crustal and marine inputs). During the 20th century, enrichments of Pb and Cu concentrations were observed to be greater than in earlier centuries, consistent with increasing anthropogenic emissions of Pb and Cu in the Southern Hemisphere over that period.