Record details

Title
    Behavior of arsenic and geochemical modeling of arsenic enrichment in aqueous environments
Statement of responsibility
    Ondra Sracek, Prosun Bhattacharya, Gunnar Jacks, Jon-Petter Gustafsson, Mattias von Brömssen
Other titles
    Arsenic in groundwater of sedimentary aquifers (Variant.)
Author
    Bhattacharya, Prosun
    Brömssen, Mattias von
    Gustafsson, Jon-Petter
    Jacks, Gunnar
    Šráček, Ondřej
Language
    anglicky
Source title - serial
    Applied geochemistry
Vol./nr.
    Vol. 19, no. 2
Pages
    p. 169-180
Year
    2004
Notes
    Bibliografie na s. 178-180
    Zkr. název ser.: Appl. Geochem.
Classfication no.
    504.05
    504.4
    628.19
Conspectus category
    504
    556
Subject group
    adsorpce
    arzén
    arzenopyrit
    auripigment
    hydroxidy
    izotermy
    modelování
    oxidace
    oxidy
    pyrit
    roztok vodný
    transport roztoků
    voda podzemní
    znečištění
    železo
Geographical name
    USA
Keyword
    Aqueous
    Arsenic
    Behavior
    Enrichment
    Environments
    Geochemical
    Modeling
Abstract (in english)
   Arsenic is present in aqueous environments in + III and +V oxidation states. In oxidizing environments, the principle attenuation mechanism of As migration is its adsorption on Fe(III) oxide and hydroxides. The adsorption affinity is higher for As(V) under lower pH conditions and for As(III) under higher pH conditions. Ferric oxide and hydroxides can dissolve under low Eh and pH conditions releasing adsorbed As. Oxidation-reduction processes often involve high organic matter content in sediments and also contamination by organics such as BTEX. Arsenic may desorb under high pH conditions. Changes of pH can be related to some redox reactions, cation exchange reactions driving dissolution of carbonates, and dissolution of silicates. In very reducing environments, where S04 reduction takes place, secondary sulfide minerals like As-bearing pyrite and orpiment, As2S3, can incorporate As.
   Geochemical modeling can be divided into two principal categories: (a) forward modeling and (b) inverse modeling. Forward modeling is used to predict water chemistry after completion of predetermined reactions. Inverse modeling is used to suggest which processes take place along a flowpath. Complex coupled transport and geochemistry programs, which allow for simulation of As adsorption, are becoming available. A common modeling approach is based on forward modeling with surface complexation modeling (SCM) of As adsorption, which can incorporate the effect of different adsorbent/As ratios, adsorption sites density, area available for adsorption, pH changes and competition of As for adsorption sites with other dissolved species such as phosphate. The adsorption modeling can be performed in both batch and transport modes in codes such as PHREEQC. Inverse modeling is generally used to verify hypotheses on the origin of As.
   Basic prerequisites of inverse modeling are the knowledge of flow pattern (sampling points used in model have to be hydraulically connected) and information about mineralogy including As mineral phases. Case studies of geochemical modeling including modeling of As adsorption are presented
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    27. 4. 2007
Import date
    8. 8. 2012