The ageing effect on the bioaccessibility and fractionation of arsenic in soils from China

Abstract

Ingestion of contaminated soil has been recognized as an important exposure pathway of arsenic for humans, especially for children through outdoor hand-to-mouth activities. An improved sequential extraction procedure was employed in an attempt to reveal the relationship between bioaccessibility and fractionation of As in five soils from China. Arsenic bioaccessibility in acidic (%pH 4.5) soils reached approximately stable levels after a sharp decline within one week of ageing. In contrast, As bioaccessibility in higher pH (>6.0) soils was found to be significantly higher and took two weeks of ageing to reach stable levels. The artificially added As was more labile than indigenous As. The main proportions of added As were found in the specifically sorbed and amorphous and poorly-crystalline hydrous Fe/Al oxide-bound fractions. Correlation analysis shows that the non-specifically and specifically sorbed As are likely to constitute the main proportion of bioaccessible soil As. The soil content of amorphous and crystalline Fe/Al oxides and soil pH appear to be the key factors controlling, not only the time needed to reach a steady state, but also the magnitude of the bioaccessibility of As added to the soils.

An inter-laboratory trial of the unified BARGE bioaccessibility method for arsenic, cadmium and lead in soil

“…This can also be seen in the very high uncertainty in the in vivo measurements (Figures 5(a) to 5(d)). Variability in bioaccessible As can be reduced by careful control of in vitro pH which has been shown to greatly affect the measured metal bioaccessibility (Oomen et al, 2002;Yang et al, 2003;Waisberg et al, 2004;Tang et al, 2006;Tang et al, 2007;Tang et al, 2008).…”

Modelling lead bioaccessibility in urban topsoils based on data from Glasgow, London, Northampton and Swansea, UK

“…Cave et al (2011) have described how specific properties of soil, such as pH, organic matter content, mineral constituents, solid phase partitioning of PHEs and soil ageing may influence bioaccessibility of priority contaminants of concern. A number of workers have successfully carried out multiple linear regression (MLR) modelling of the bioaccessible PHE content of soils, specifically arsenic (As), using their physicochemical properties, such as the elemental composition of the soil and soil pH as the predictor variables (Yang et al, 2002;Klinck et al, 2005;Tang et al, 2007). Pb bioaccessibility studies have generally focussed on the relationships between total and bioaccessible Pb concentrations (Farmer et al, 2011;Cave et al, 2011) sometimes with due consideration given to the different sources of Pb contamination (Smith et al 2011).…”

Anthropogenic and geogenic impacts on arsenic bioaccessibility in UK topsoils

“…have described how specific properties of soil, such as pH, organic matter content, mineral constituents, solid phase partitioning of As and soil ageing may influence bioaccessibility of As and other contaminants. A number of workers have successfully carried out multiple linear regression (MLR) modelling of the bioaccessible As content of soils using their physico-chemical properties, such as the elemental composition of the soil and soil pH as the predictor variables (Yang et al, 2002;Klinck et al, 2005;Tang et al, 2007;Juhasz et al, 2007bJuhasz et al, , 2008. Sarkar et al (2007) used the element composition, pH, clay content and cation exchange capacity and Cave et al (2007) used spectral properties derived from near infra-red spectra of the soils.…”