Surface Microanalysis and Sequential Chemical Extraction as Tools for Reliable Environmental Mobility Assessment of Sb and Other Metals

Abstract

Sequential extraction procedures (SEPs) are widely used in environmental studies to infer the chemical and/or mineralogical forms of pollutants of concern in soils and sediments. Although there is no general agreement among the scientific community, these methods have shown some limitations, especially those with a lack of objectivity in their interpretation. In this work, a soil sampling campaign was carried out in an area affected by an abandoned Sb mine. Samples (0–15 cm) were carefully prepared and analyzed by an SEP. They were also studied by conventional mineralogical methods (optical and electronic microscopy, both scanning and transmission, with a coupled energy dispersive X-ray (EDX) spectrometer). When comparing the results obtained from both techniques, some discrepancies are highlighted, with As, Cu, Pb, Sb and Zn as elements of concern. For Sb, Cu, Pb and As the predominant fraction (excluding the residual one) is that associated with organic matter (from 8.54 for Sb to 18.90% for Cu). The fractions of pollutants linked to Fe and/or Mn oxides are quantitatively important for As, Pb and Zn (6.46%, 12.05% and 7.43%, respectively) and almost negligible for Cu and Sb. On the contrary, analyses carried out by EDX at a grain scale pointed out that no detectable quantities of the elements of concern were present on the surface of the organic particles. Sb and Pb were always detectable in Fe oxides (up to 1.84 and 5.76%, respectively). Regarding the role of the clayey fraction, the only disagreement between the employed SEP and the microanalysis is in relation to As. Arsenic bound to clay minerals was found to be an order of magnitude lower than As associated with Fe oxides (0.56% and 6.46%, respectively); in contrast, EDX microanalyses showed similar As contents in both groups. Given the objectiveness of EDX microanalysis, these differences should be considered inaccuracies in the interpretation of the sequential extraction results.

Comparative assessment of phytoavailable cadmium by using various extractants in texturally different contaminated soils during the growth of maize crop

“…Environmental studies frequently use sequential extraction techniques to determine the mineralogical and/or chemical forms of contaminants that are hazardous in soils and sediments. Metals bound to various mineral or organic phases can potentially be estimated more accurately using sequential extraction techniques (Abedin et al, 2012;Álvarez-Quintana et al, 2022). Sequential extraction methods are time-consuming and laborious methods as compared to single extraction method which uses a single extractant to extract the trace metal (Kumkrong et al, 2022;Mbodji et al, 2022).…”

The concept of building a robotic system for monitoring the quality of ores in a natural occurrence

“…Nowadays a clear understanding has been formed that the level of industrial development of the state should be determined not by their resource capabilities and the size of the production of products with a low level of technological processing, but by the degree of development of science-intensive, technologically advanced industries. One of the key aspects of a new type of innovative development in the field of high technologies is analytical instrumentation, based on the development of high-precision energy-dispersive X-ray fluorescent analytical instruments and their modifications [1,2], which are widely used to solve various problems [3][4][5][6].…”