Registration Dossier
Registration Dossier
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EC number: 236-715-1 | CAS number: 13466-20-1
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
Additional information
The mobility of barium in soils depends on the solubility of the formed compounds.
Barium bis(dihydrogenorthophosphate) will not exist in this from in the environment. The high water solubility of the substance (WS: 27.79 ± 0.63 g/L at 20 °C and pH 2.9 - 3.0) indicates that barium bis(dihydrogenorthophosphate) dissociates to phosphate species and barium ion. Under natural conditions barium occurs in the +2 oxidation state. The ion doesn’t exist as free metal in the environment but will mainly form insoluble inorganic complexes such as barium sulphate and barium carbonate. Both barium salts will precipitate from the water column. Due to the low water solubility barium sulphate and barium carbonate are not mobile in soils. The solubility and thus the mobility increases with decreasing pH. Furthermore the mobility in soil strongly depends on the cation exchange capacity (CEC) of the soil. In soils with a high CEC i.e. soils with more clay or organic matter, barium will be less mobile due to the adsorption to clay minerals (ATSDR, 2007).
The phosphate species can occur in three states of protonation, which is pH dependent. In soil H2PO4 and HPO4 are the dominant species for pH values of 4.5 – 6.2, which are occur normally in soil. This is the form in which phosphorus is used by plants. Precipitation-dissolution and sorption-desorption processes control the concentration pf phosphate ions in solution. Phosphorus ions are mainly immobilised in soils by adsorption to solid matter or by reaction with aluminium or iron to aluminium- and ironphosphates (Cornforth 2008). Except in very acid or alkali conditions, phosphate exists mainly as organic or inorganic complexes which determine the transport and distribution behaviour of phosphorous (De Vos, 2006).
Reference
ATSDR, Agency for Toxic Substances and Disease Registry, 2007, Toxicological profile for Barium and Barium compounds. U.S.Department of Health and Human Services.
Cornforth I.S. (2008) The fate of phosphate fertilizers in soil. New Zealand Institute of Chemistry. II-Chemicals and Soils-D-Phosphate-2 (with reference to: Dahal 1977; McLaren and Cameron 1990; Syers and Cornforth 1983)
De Vos W. and Tarvainen T. (2006), Eds., Geochemical Atlas of Europe Part 2: Interpretation of Geochemical Mops, Additional Tables, Figures, Maps and Related Publications, EuroGeosurveys & Foregs, Espoo, Finland, 2006.
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