Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Due to a strong dependence on pH and concentration which leads to a dynamic polymerisation-depolymerisation equilibrium with speciation into a variety of mono-, oligo-, and polymeric anions and amorphous silica, calculations on the distribution in various environmental compartments are not feasible (HERA 2005).

Dissolved silica from commercial soluble silicates is indistinguishable from natural dissolved silica. Of the elemental composition of the earth’s crust, SiO2represents about 59%. Thus, silica is the second most abundant element on earth. Similar percentages are obtained for many sediments and soils (Jackson 1964 as cited in HERA 2005).

Compounds of silicon and oxygen are ubiquitous in the environment; they are present in inorganic matter, like minerals and soils as well as in organic matter, like plants, animals and man. By weathering of soil, rocks and sediments and by atmospheric deposition, silica is released into surface and ground waters from where it may be removed by precipitation and sedimentation or taken up by living organisms, especially diatoms. Dead sedimenting diatoms also contribute significantly to sediment silica (diatomaceous earth). Silica is found in all natural waters with an average concentration of 10-20 mg SiO2/L (HERA 2005), in European rivers in mean concentrations of 7.5 mg SiO2/L (Jorgensen et al. 1991). Due to the low vapour pressure, volatilisation is not expected.

Silicic acid, lithium salt, if released into the environment, is expected to combine indistinguishably with the soil or sediment due to its similarity with inorganic soil/sediment matter and will be subjected to natural processes under environmental conditions (cation exchange, dissolution, sedimentation). It is expected to distribute mainly into soils and sediments, weakly into water and probably not at all into the air.