Uptake of Arsenic by Plants in Southwest England

Abstract

The literature concerning arsenic in soils and plants is reviewed briefly. The uptake of arsenic by a number of plants that colonize sites, contaminated by arsenic from past mining and smelting activities, is described. Plants growing on soil with high As were stunted and displayed a red coloration. Armeria martima operates an exclusion mechanism, with low root/soil concentration ratios. Uptake of arsenic from soil in Calluna vulgaris and Agrostis tenuis show weak correlations with Fe in soil and soil pH. The relative accumulation (leaf/soil ratio) of As in Calluna at one site plotted against soil concentration approximated to a hyberbolic curve.The sources of naturally occurring arsenic in the environment are primary minerals including arsenopyrite (FeAsS), orpiment (As 2 S 3 ), realgar (As 4 S 4 ) and secondary minerals of arsenic (1,2). The geochemistry of arsenic has recently been reviewed (3-5), including estimates of the arsenic global cycle (5).Arsenic concentrations in uncontaminated soils have been reported in the range 0.1-40 μg/g worldwide (6,7) with an average of 5-6 μg/g (8) and 5-100 μg/g for the UK (9). High concentrations in soils, relative to these values, can occur in many areas; these arise from (4): naturally occurring arsenic-rich minerals and rocks, such as pyrite; waste materials resulting from mining and smelting activities; the burning of arsenic-rich coal; arsenic-containing agrochemicals (10), and organoarsenic-based warfare agents (//).Depending on pH and Eh, arsenic is present in soils as As(III) or As(V) (2). Microbial activity within the soil gives rise to a number of reactions, including methylation, demethylation, oxidation and reduction (2). Under aerobic conditions arsenate(V) is precipitated as ferric arsenate in horizons rich in iron. Both As(III) and As(V) complex with hydrous oxides of Fe, Mn and Al (12, 13). The sorption of As by hydrous iron oxides occurs both in acid and in alkaline soils, whereas sorption by hydrous oxides of Al is reported to be important only in acidic soils (14)(15)(16). Under reducing sulfidic conditions, As(III) associates with metal sulfides, sulfidic minerals being formed under extreme reducing conditions. Clay minerals and organic ligands can also influence the species of arsenic present in soil.Many authors have sought to discover the species of arsenic present in soil, the leachability and the potential bioavailability of arsenic to biota, including post-ingestion bioavailability to humans. Arsenic-bearing phases in soils and waste materials have been characterized using electron microprobe analysis (EMPA) (17) and extended X-ray absorption fine-structure spectroscopy (EXAFS) (18). Single (19) and sequential (20-25), extraction schemes have been developed leading to operationally determined associations between arsenic oxyanions and other soil constituents, many based on the similar chemistry of As and Ρ (26,27). The introduction of chromatographic separation coupled with inductively coupled plasma -mass spectrometry (ICP-MS) has lead to the i...

An investigation of arsenic contamination in Peninsular Malaysia based on Centella asiatica and soil samples

“…4). As was found in most plants, its biochemical role is unclear (Farago et al 2003;Kabata-Pendias and Mukherjee 2007).…”

Portable X-ray fluorescence in the characterisation of arsenic contamination associated with industrial buildings at a heritage arsenic works site near Redruth, Cornwall, UK

“…These sources are estimated to have contaminated some 700 km 2 of soil in Devon and Cornwall (Abrahams and Thornton 4 ). Detailed studies of 13 contaminated and control areas reviewed by Farago et al 5 have identified particularly high concentrations in soils at sites associated with smelting at Roseworthy (range 815 to 161000 mg g 21 , Frizzell 6 ), Devon Great Consols (120-52000 mg g 21 , Kavanagh et al 7 ), Poldice (432-37600 mg g 21 , Farago et al 8 ) and the Tamar Valley (120-52600 mg g 21 , Kavanagh et al 11 ). In terms of health risks, the potential for human exposure in the home environment has been investigated by the chemical analysis of house dusts (Johnson, 9 and Elgahi 10 ) and of human urine (Kavanagh et al 12 ).…”