Sequential Extraction Analysis of Arsenic in Soil Samples Collected in an Agricultural Area of Brindisi, Apulia (Italy), in the Proximity of a Coal-Burning Power Plant

Abstract

In order to evaluate the local environmental risk deriving from coal transport and burning, 30 soil samples were collected along the coal conveyor belt and around the coal-burning power plant Federico II of Brindisi (Apulia, southern Italy). Since soil pollution of metals and metalloids is measured not only by their total concentration but also by evaluating their mobility and availability, arsenic sequential extraction, leaching test and speciation analysis were performed. The analytical results showed that the most abundant As amount was contained in the final residue of the sequential extraction procedure, the so-called occluded As, embedded in rock formations such as sulphides. Moreover speciation chemical analysis showed that As(V) was by far the most abundant species, whereas As(III), which represents the most soluble and available species, was only a very small fraction. No arsenic organic species were detected in the soil samples.

Quantification of Arsenic in Soil Samples Collected in an Industrial Area of Brindisi (Apulia, Italy): Speciation Analysis and Availability

“…Ammonium oxalate extractions showed that, even in the deeper layers of the sampled sites, a non-negligible quantity of strongly bound or occluded arsenic is present, as already observed in other sites in the area [22], pointing at least partially to a possible natural soil origin.…”

“…Obviously the collection of this type of data would have required a much more extensive approach. Nevertheless, the speciation analyses confirmed that most As occurs as relatively immobile or slowly exchangeable forms, suggesting that it is a naturally occurring component of the soil in the area [22]. In fact, As is generally associated with sulfide minerals, and its mobility and availability in soils are strictly related to pH, redox potential, ionic composition, and mineral type.…”

“…Many minerals containing As (for example arsenopyrite, FeAsS) may be found in soils without presenting an immediate risk because of a very low solubility, except in specific conditions or in the long-term [21]. Therefore, sequential extractions may be needed to investigate the effective mobility and availability of the As contained in the samples [22].…”

Fractionation of Metal(loid)s in Three European Mine Wastes by Sequential Extraction

“…Operationally defined fractionation of elements in various environmental samples has been conducted using sequential leaching methods. Examples are river sediments [13][14][15], soils [16][17][18], coal ash [4,19,20], green liquor dregs [21], black shale [22], phosphogypsum [23], sewage sludges [24][25][26], and mine wastes [27][28][29][30][31].…”

Biogeochemistry of arsenic and lead in sediment and water amended with biochar

“…The chemical sequential extraction has some problems related to the solubilized phase and/or the extracted fraction, in addition to the possibility of losing soil/sediment mass during the sequential extraction (Martin et al, 1987;Migoni et al, 2021). Non-destructive analyzes, such as those based on synchrotron radiation (Lombi and Susini, 2009) have been used as an alternative for sequential extraction.…”