Validation of an updated fractionation and indirect speciation procedure for inorganic arsenic in oxic and suboxic soils and sediments. (December 2016)

• Record Type: Journal Article
• Authors: Lock, Alan; Wallschläger, Dirk; McMurdo, Colin; Tyler, Laura; Belzile, Nelson; Spiers, Graeme
• Is Part Of: Environmental pollution. Volume 219(2016)
• Page Start: 1102
• Page End: 1108
• Publication Date: 2016-12
• Subjects: Arsenic -- Speciation -- Sequential extraction -- Mobility; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2016.09.013
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: A sequential extraction procedure (SEP) for the speciation analysis of As(III) and As(V) in oxic and suboxic soils and sediments was validated using a natural lake sediment and three certified reference materials, as well as spike recoveries of As(III) and As(V). Many of the extraction steps have been previously validated making the procedure useful for comparisons to similar previous SEP studies. The novel aspect of this research is the validation for the SEP to maintain As(III) and As(V) species. The proposed five step extraction procedure includes the extraction agents (NH4 )2 SO4, NH4 H2 PO4, H3 PO4 + NH2 OH·HCl, oxalate + ascorbic acid (heated), and HNO3 + HCl + HF, targeting operationally defined easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and residual As fractions, respectively. The third extraction step, H3 PO4 + NH2 OH·HCl, has not been previously validated for fraction selectivity. We present evidence for this extraction step to target As complexed with amorphous Fe oxides when used in the SEP proposed here. All solutions were analyzed on ICP-MS. The greatest concentrations of As were extracted from the amorphous Fe oxide fraction and the dominant species was As(V). Lake sediment materials were found to have higher As(III) concentrations than the soil materials. Because different soils/sediments have different chemical characteristics, maintenance of As species during extractions must be validated for specific soil/sediment types using spiking experiments. Graphical abstract: Highlights: Validated sequential extraction procedure that maintains As(III) and As(V) species. Evidence supports H3 PO4 extraction targets As complexed with amorphous Fe oxides. Amorphous Fe oxide fraction binds the largest concentration of As. As(V) is the dominant species extracted from all samples and fractions. New sample matrixes must be validated to maintain As species using spike recoveries. Abstract : A sequential extraction procedure that maintains As(III) and As(V) species has been validated providing an analytical tool to assist environmental As investigations.