Speciation and Fractionation of Soil Arsenic from Natural and Anthropogenic Sources: Chemical Extraction, Scanning Electron Microscopy, and Micro-XRF/XAFS Investigation

Abstract

A large amount of excavated soils with low-level As contamination caused by civil construction projects is of great concern in Japan. This study investigated the chemical speciation and extractability of As in 24 soil samples from the sites affected and unaffected (naturally contaminated) by anthropogenic pollution. The results of As K-edge XANES demonstrated that naturally contaminated soils were grouped into two types: (i) soils containing FeAsS-like and As2S3-like species (ave. 53%, hereafter As-S species) and (ii) soils with no or minor As-S species (ave. 3%). Clear differences were found in As, Fe, and S fractionations by sequential extraction. From naturally contaminated soils enriched with As-S species, more than 50% of As was extracted in the oxidizable fraction. Arsenic was mainly recovered in the reducible fraction for naturally contaminated soils with no or minor As-S species and anthropogenically contaminated soils. The μ-XRF and μ-XAFS revealed that the naturally contaminated soils containing As-S species were abundant in pyrite framboids (∼20 μm in diameter) in which As occurred as multiple oxidation states. The results suggest that framboidal pyrite becomes a source of As in naturally contaminated soils after being excavated and exposed to the surface environment.

A review on arsenic in the environment: contamination, mobility, sources, and exposure

“…, 17 and the mineralization of FeAsS and As 2 S 3 -like species in soil results in its pollution with As. 188…”

“…Arsenic in soils results from anthropogenic activities, and the main sources in the soil are naturally occurring minerals, such as arsenopyrite, gelignite, realgar, orpiment, etc., 17 and the mineralization of FeAsS and As 2 S 3 -like species in soil results in its pollution with As. 188 The major inputs of As in soil are associated with burning of fossil fuels and biomass, mining activities, industrial effluents, use of pesticides (e.g. monosodium methyl arsenate, disodium methyl arsenate and cacodylic acid) in agriculture, lumber preservatives (e.g.…”

Dual Regulatory Role of Penicillium oxalicum SL2 in Soil: Phosphorus Solubilization and Pb Stabilization

“…The soil samples were freeze-dried and screened through 100 mesh. One-step extraction (0.05 mol/L EDTA, 0.43 mol/L HNO 3 and 0.01 mol/L CaCl 2 ) 32 and sequential-steps extraction (BCR method) 33 were used to analyze the Pb availability in soil. The extraction solution was filtered by 0.22 μm and determined by ICP-MS (PlasmaQuant MS, Analytik-Jena, Germany).…”

Atomic Spectrometry Update: review of advances in elemental speciation

“…Several workers have reported on As speciation in soils and sediments. A study to investigate the chemical speciation and extractability of As in 24 soil samples from sites potentially affected by anthropogenic pollution in Japan has been reported by Itabshi et al 83 The results of As K-edge XANES demonstrated that naturally contaminated soils were grouped into two types: (i) soils containing FeAsS-like and As 2 S 3 -like species (average 53%) and (ii) soils with no or minor As-S species (average 3%). Clear differences were found in As, Fe, and S fractionation by sequential extraction.…”