Chemical Fractionation of Trace Elements in Arctic PM10 Samples

In this study, the information potential of a two-step sequential extraction procedure was evaluated. For this purpose, first of all the elemental composition of Arctic PM10 samples collected in Ny-Ålesund (Svalbard Islands) from 28 February 2015 to 21 October 2015 was investigated. Enrichment Factors, Principal Component Analysis and Hierarchical Cluster Analysis were performed to identify PM10 sources and to understand the effects of short- and long-range transport processes. The investigation of the potential source areas was also aided by taking into account back-trajectories. Then, the sequential extraction procedure was applied to some of the samples in order to obtain more information on these sources. This approach allowed us to establish that most of the elements prevalently having an anthropogenic origin not only were present in higher concentrations, but they were also more easily extractable in late winter and early spring. This confirms the common statement that the anthropogenic portion of the elements present in a sample is generally loosely bound to the particulate matter structure, and so it is more easily extractable and releasable on the Arctic snowpack. Moreover, in the samples collected in late winter and early spring, even the elements prevalently having a crustal origin were more easily extractable, probably due to the particle size selection occurred during the long-range transport.

Optimization and assessment of a sequential extraction procedure for calcium carbonate rocks

Sequential extraction analyses are widely used for the determination of element speciation in sediments and soils. Typical sequential extraction protocols were developed to extract from low-carbonate samples and therefore are not necessarily suitable for high-carbonate samples. In this study, we tested increased reagent to sample ratios to adjust an existing sequential extraction procedure to analyze high-CaCO3 samples with concentrations ranging from 70 to above 90 %. Complete dissolution of the CaCO3 phase, and a higher extraction efficiency of manganese associated with the carbonate phase, was achieved when using four times the original reagent to sample ratio in the 2nd extraction step. This increase of reagent did not compromise the extraction of subsequent phases as shown by unaffected Fe concentrations in a low-carbonate sample. Hence, an essential outcome was that increasing the solution to sample ratio did not lead to the dissolution of other sedimentary phases, such as hydrous and crystalline iron oxides or sulfides. Thus, compared to other extraction protocols that use a lower reagent to sample ratio in the carbonate dissolution step, the new protocol allowed the complete extraction of oxide and sulfide phases in the following extraction steps. Furthermore, the study demonstrated the benefit of replacing Na-acetate with NH4-acetate to extract exchangeable ions and carbonates. We observed increased intensities for several analytes, i.e., trace metals such as Mo and As, due to less suppression of the analyte signal by NH4-acetate than by Na-acetate during analysis by inductively coupled plasma optical emission spectrometry (ICP-OES).

Mobility of Potentially Toxic Elements from the Abandoned Uranium Mine’s Spoil Bank

This study is part of the ongoing environmental monitoring program of the abandoned Mecsek uranium mine during the remediation period. During this program on the recultivated No.1 spoil bank, the radioactivity and the potentially toxic element (PTE) contents in the covering soil had shown some anomalies which refers to possible migration alongside the slope. Therefore, in a previous study, soil and plant samples were collected from top to bottom position of the slope and the total element content was determined by multi-elemental inductively coupled plasma-optical emission spectrometry. The results have indicated that there was a high possibility for PTEs to be mobile and available for uptake by plants. To confirm this indication in the present study for the soil samples the BCR sequential extraction procedure was applied to characterise the environmental mobility of PTEs, and it was compared with soil pH and cation exchange capacity (CEC). The results indicated that the ratio of Cd, Co, Mn, Pb, and U in the non-residual fractions ranged between 36.8 to 100 % and increased from top to bottom direction. The comparison showed that the samples with the lowest pH and CEC had the most mobility of the PTEs. The distribution of U, Cd, Mn, Co, and Pb in fractions indicated that some parts of the spoil deposit require additional steps to hinder the migration through the covering soil layer, and the BCR sequential extraction procedure has proven to be useful in providing information for the planning and management of remediation operations.

SEQUENTIAL EXTRACTION PROCEDURE: A VERSATILE TOOL FOR ENVIRONMENTAL RESEARCH

The sequential extraction procedure as a tool to assess the environmental risk of metals in solid matrices has been widely studied. In this work, another promising application of these methods is proposed: the evaluation of the recoverability of critical raw materials from a solid matrix. To this aim, the normalized sequential extraction procedure BCR was applied to a contaminated soil from the south of Spain. In addition to this, the influence of the incomplete dissolution of carbonates contained in the soil on the fractionation results has been also studied. The high percentage of metal in the most mobile fractions suggested the potential use of the solid matrix as secondary source. The use of this approach together with environmental and economic feasibility studies would be an approach toward the circular economy.