Mineralogy, solid-phase fractionation and chemical extraction to assess the mobility and availability of arsenic in an urban environment

Abstract

A multidisciplinary approach, using chemical extraction and analytical structural techniques, has been used to assess the mobility and availability of arsenic in urban soil samples from two current housing sites. Arsenic concentrations in each site varied between 126-1,660 mg/kg (Site A) and 40-24,900 mg/kg (Site B). Using a non-specific sequential extraction approach, it was possible to identify two distinct, site specific, As-containing fractions i.e. Fe-As-Ca (Site A) and As-Fe (Site B), in the soils. Further investigation using a sequential extraction approach identified the main As component in the reducible fraction, linking As with Fe-oxides in the soils. Further investigation of the crystalline mineral phases, by X-ray diffraction, within the most As-contaminated soils (up to 24,000 mg/kg) identified no Asbearing minerals but identified the major component as quartz (SiO2) with an array of minor and trace minerals. Further mineralogical investigation, using micro-Raman in the major Ascontaminated soils (from Site B) as well as reconfirming the presence of the major mineral (quartz) additionally identified the As-bearing minerals pharmacosiderite (KFe4[(H2O)4(AsO4)3].6H2O) and mimetite (Pb5(AsO4)3Cl) in the trace mineral component, alongside amorphous carbon, chromite (FeCr2O4), goethite (α-FeO(OH)), gypsum (CaSO4.H2O), muscovite (KAl2(AlSi3O10)(F,OH)2), magnetite (Fe3O4), martite (α-Fe2O3), psilomelane (Ba,H2O)2Mn5O10), pyrrhotite (Fe7S8) and rutile (TiO2). The identification and presence of several Fe-rich minerals could be considered as the major hosts of As in the soil matrix. It is concluded that while the soil contains elevated levels of As, it's lack of mobility in the soil, means that minimal remedial action is required provided the sites are left undisturbed and free of human endeavour and activity.

Investigating the Geochemical Controls on Pb Bioaccessibility in Urban Agricultural Soils to Inform Sustainable Site Management

“…The solid-phase fractionation of the test soils was determined using the Chemometric Identification of Substrates and Elements Distributions (CISED) method [12][13][14][15].…”

“…80%) and a much lower variability in Ca content suggesting it represents a purer form of Ca carbonate than cluster 4. The peaks of extraction of each component are more variable than those in cluster 4 (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). This may suggest that some of these components are more crystalline than those in cluster 4 which may be a more fine-grained amorphous material.…”

Biogeochemistry of Household Dust Samples Collected from Private Homes of a Portuguese Industrial City

“…A total of 14 extracts per dust were obtained for analysis of 30 elements by ICP-MS. Subsequently, the multi-element extract data were subject to a chemometric self-modelling mixture resolution (SMMR) procedure, as described elsewhere [32,34]. For data quality control, blanks, and reference material (BGS102) were included in the extraction procedure.…”

“…An earlier version of this same reference material has been analysed previously by Cave and co-authors [35]. Several studies were shown the CISED as a useful methodology for understanding the biogeochemistry of trace elements in soil and dust [30,34,36].…”

“…Compositional similarities and an equal number of components obtained by the SMMR modelling were observed for sites #1, #2, and #8. As such, the dust extracts were processed as a group and then combined into a single input data for the SMMR analysis as described elsewhere [34]. For this group, the chemometric data analysis identified seven physicochemical components.…”