The influence of adsorption on the rates oi n degradation of arsenic species in sediments1

Abstract

A model to describe the rates of microbially mediated transformations is presented along with a simple numerical method for kinetic computations in complex systems. The model is tested against the results of arsenic demethylation experiments assuming first-order kinetics and Langmuir adsorption. There is agreement between theory and experiment.

Dynamics of organic and inorganic arsenic in the solution phase of an acidic fen in Germany

“…Increased methyl substitution of As species resulted in both decreased adsorbed As at low As concentrations in solution phases and increased As release from the Fe oxide surface. The adsorption of As species to Al oxides, was As(V) > As(III) > MMA = DMA (Xu et al, 1991) In aerobic soils, the order of sorption was As(V) = M-MA > DMA (Wauchope, 1975) and in aerobic river sediment, the order of sorption was As(V) > MMA > DMA (Holm et al, 1980). Arsenic methylation can be thus regarded as a process of As mobilization in soils and sediments.…”

“…Tetramethylarsonium ion (TETRA), arsenobetaine (AsB), arsenocholine (AsC), and arsenosugars, are thought to be originated from biosynthesis, e.g., by alga or microorganisms (Pongratz, 1998;Geiszinger et al, 2002). The toxicity and mobility of As species depends on their chemical forms: inorganic As species are more toxic and less mobile than organic As species (Wauchope, 1975;Holm et al, 1980;Chiu and Hering, 2000;Mandal and Suzuki, 2002). Thus, investigation on the total As (As total ) is not sufficient for risk assessment of As in the environment.…”

Organic Arsenic in the Soil Environment: Speciation, Occurrence, Transformation, and Adsorption Behavior

“…For example, the order of sorption was DMAA<MMAA≈As(V) in aerobic soils (Wauchope 1975). In aerobic river sediment, the order of sorption was DMAA<MMAA<As(V) (Holm et al 1980). Thus, As may become more mobile and bioavailable in soil systems where As methylation is favored.…”

Soil redox-pH stability of arsenic species and its influence on arsenic uptake by rice

“…As for the inorganic As chemical forms (Livesey and Huang, 1981;Pierce and Moore, 1982) Fe-oxides have been implicated in the sorption of MMAA by soils (Holm et al, 1980). The observed responses of MMAA solubility to redox and pH are likely due to reduced sorption capacity of the soil caused by decreasing redox or increasing pH.…”