Mercury (Hg) contamination of soils and sediments represents a serious concern for human and ecosystem health. The mobility and bioavailability of Hg in the environment are function of its chemical form, so Hg speciation analysis represents a key aspect for assessing the fate of Hg and the environmental and health risk associated with Hg contamination. The occurrence of different Hg species in environment samples is usually assessed by means of multiple step extraction procedures, which, however, are time-consuming and characterized by low reproducibility and non-specific removal of species (Issaro et al., 2009). In this work, we evaluate the possible application of a thermo-desorption (TD) Hg speciation technique, which allows a prompt evaluation of Hg species according to their release temperature, for the risk assessment procedure at a Hg contaminated site of Friuli-Venezia Giulia region by comparing results obtained through this approach with those derived from the commonly used selective sequential extraction (SSE) method (e.g. Bloom et al., 2003). For risk calculations, relative amounts of non-cinnabar compounds determined through TD and mobile Hg fractions obtained from SSE procedure were considered. The study site is a portion of the embankment of the Marano and Grado Lagoon, an area impacted by Hg as a result of past mining (cinnabar extraction) and industrial activities. In this work, 23 surface and deep soil samples were collected and analyzed for total Hg (THg) concentration and Hg speciation through TD, whereas SSE was applied only to four samples characterized by the highest THg contents. The THg concentrations found in this study ranged between 0.240 and 3.091 mg/kg, exceeding the Italian regulation limit (1 mg/kg) in the eastern part of the study area. However, the calculated risk resulted “acceptable” using both SSE and TD data, despite the higher abundance of potentially mobile forms of Hg found through the latter technique. Besides, TD data are referred to the results obtained from all the 23 soil samples collected in the study area, providing a major representativeness. Considering also its celerity, reproducibility, low costs and accuracy in Hg species discrimination, the TD technique could then represent a useful and low expensive tool for future risk assessments of Hg contaminated sites, particularly those characterized by the occurrence of cinnabar, easily discriminable through this technique. Bloom N.S., Preus E., Katon J. & Hiltner M. (2003) - Selective extractions to assess the biogeochemically relevant fractionation of inorganic mercury in sediments and soils. Anal Chim Acta, 479, 233-248. Issaro N., Abi-Ghanem C. & Bermond A. (2009) - Fractionation studies of mercury in soils and sediments: A review of the chemical reagents used for mercury extraction. Anal Chim Acta, 631, 1-12
Application of a thermo-desorption technique for mercury speciation on soil samples to support the risk assessment procedure of Mercury-contaminated sites.
Floreani F.
;Petranich E.;Covelli S.
2021-01-01
Abstract
Mercury (Hg) contamination of soils and sediments represents a serious concern for human and ecosystem health. The mobility and bioavailability of Hg in the environment are function of its chemical form, so Hg speciation analysis represents a key aspect for assessing the fate of Hg and the environmental and health risk associated with Hg contamination. The occurrence of different Hg species in environment samples is usually assessed by means of multiple step extraction procedures, which, however, are time-consuming and characterized by low reproducibility and non-specific removal of species (Issaro et al., 2009). In this work, we evaluate the possible application of a thermo-desorption (TD) Hg speciation technique, which allows a prompt evaluation of Hg species according to their release temperature, for the risk assessment procedure at a Hg contaminated site of Friuli-Venezia Giulia region by comparing results obtained through this approach with those derived from the commonly used selective sequential extraction (SSE) method (e.g. Bloom et al., 2003). For risk calculations, relative amounts of non-cinnabar compounds determined through TD and mobile Hg fractions obtained from SSE procedure were considered. The study site is a portion of the embankment of the Marano and Grado Lagoon, an area impacted by Hg as a result of past mining (cinnabar extraction) and industrial activities. In this work, 23 surface and deep soil samples were collected and analyzed for total Hg (THg) concentration and Hg speciation through TD, whereas SSE was applied only to four samples characterized by the highest THg contents. The THg concentrations found in this study ranged between 0.240 and 3.091 mg/kg, exceeding the Italian regulation limit (1 mg/kg) in the eastern part of the study area. However, the calculated risk resulted “acceptable” using both SSE and TD data, despite the higher abundance of potentially mobile forms of Hg found through the latter technique. Besides, TD data are referred to the results obtained from all the 23 soil samples collected in the study area, providing a major representativeness. Considering also its celerity, reproducibility, low costs and accuracy in Hg species discrimination, the TD technique could then represent a useful and low expensive tool for future risk assessments of Hg contaminated sites, particularly those characterized by the occurrence of cinnabar, easily discriminable through this technique. Bloom N.S., Preus E., Katon J. & Hiltner M. (2003) - Selective extractions to assess the biogeochemically relevant fractionation of inorganic mercury in sediments and soils. Anal Chim Acta, 479, 233-248. Issaro N., Abi-Ghanem C. & Bermond A. (2009) - Fractionation studies of mercury in soils and sediments: A review of the chemical reagents used for mercury extraction. Anal Chim Acta, 631, 1-12Pubblicazioni consigliate
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