Trichloro(methyl)silane

Other distribution data

Administrative data

Endpoint:

other distribution data

Type of information:

calculation (if not (Q)SAR)

Remarks:

Migrated phrase: estimated by calculation

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Acceptable calculation method

Data source

Reference

Reference Type:

other: calculation method

Title:

Estimations Programs Interface (EPI) Suite™.

Author:

United States Environmental Protection Agency

Year:

2000

Materials and methods

Principles of method if other than guideline:

Modeling

Type of study:

other: Fugacity Model Level I, II and III

Media:

other: Multimedia (i.e., fugacity) modeling

Test material

Test material information

Constituent 1

Reference substance name:

Trichloro(methyl)silane

EC Number:

200-902-6

EC Name:

Trichloro(methyl)silane

Cas Number:

75-79-6

Molecular formula:

CH3Cl3Si

IUPAC Name:

trichloro(methyl)silane

Results and discussion

Any other information on results incl. tables

Level-I Simulation:  A Level-I simulation evaluates the equilibrium  

distribution of a fixed quantity of chemical in a closed environment with  

no degradation reactions, no advective processes, and no intermedia  

transport process (e.g., no wet deposition or sedimentation).  Output  

from the Level-I simulation provides a general indication of the likely  

media into which a chemical will tend to partition and the relative  

concentrations in each medium.

Results from the Level-I simulation (Table 2) indicate that  

trichloromethylsilane has the tendency to partition exclusively into the  

air compartment, which holds essentially 100% of the total chemical mass.   

Insignificant amounts of trichloromethylsilane (< 0.5% of the total  mass) 

are expected to partition to the water, soil, and sediment  compartments.

Table 2.  Environmental distribution of trichloromethylsilane, based on  

Level-I fugacity modeling.
        Environmental Distribution (%)
        Air        Water        Soil        Sediment
        99.5        0.4        0.0        0.0

Level-II Simulation:  A Level-II simulation evaluates the equilibrium  

distribution of a chemical that is continuously discharged to the  

environment at a constant rate, and achieves a steady-state condition at  

which the input and output rates are equal.  Degradation reactions and  

advective processes are treated as the mechanism of loss or output.   

Intermedia transport processes are not quantified (e.g., no wet  

deposition or sedimentation).  Similar to a Level-I simulation, output  

from a Level-II simulation provides an indication of the likely media  

into which a chemical will tend to partition and the relative  

concentrations in each medium.  In addition, the Level-II simulation also  

provides an indication of environmental persistence and the loss  

processes that are likely to be most important.

Results from the Level-II simulation (Table 3) show the same  

environmental distribution characteristics as the Level-I simulation  

(Table 2), with > 99% of the total mass of trichloromethylsilane found in  

the air compartment.  The results also show that degradation (i.e.,  

hydrolysis) in air and water are the primary mechanisms of removal for  

trichloromethylsilane in the local environment, with advective losses  

accounting for only < 0.1% of the total mass removed.  Output from the  

model indicates that trichloromethylsilane will have a local persistence  

of about 0.04 hours (2 min) and a global persistence of about 0.04 hours  

(2 min).

Table 3.  Distribution and environmental residence time of  

trichloromethylsilane, based on Level-II fugacity modeling.
        Environmental Compartment
                        Air        Water        Soil        Sediment
Distribution (%)        99.5        0.4        0.0        0.0
Reaction losses (%)        95.8        4.1        0.0        0.0
Advective losses (%)        0.0        0.0                0.0

Overall residence time (h)        0.04
Reaction residence time (h)        0.04
Advective residence time (h)        100

Level-III Simulation:  A Level-III simulation is similar to a Level-II 

simulation in that a) the chemical is continuously discharged to the 

environment at a constant rate, b) achieves a steady-state condition 

at which the input and output rates are equal, and c) the mechanism 

of loss is determined by degradation reactions and advective processes.  

However,  unlike a Level-II simulation, equilibrium between environmental  

compartments is not assumed and intercompartmental transport processes  

are quantified (e.g., wet deposition, sedimentation, resuspension, soil  

runoff, aerosols, etc. are taken into account).  Output from a Level-III  

simulation provides a more realistic description of a chemical's fate,  

including the important degradation and advective losses and the  

intermedia transport processes.  In addition, the simulation gives an  

indication on how source of entry of a chemical to the environment (e.g.,  

to air, to water, and/or to soil) effects distribution and persistence.

Results from the Level-III simulations (Tables 4a-4c) demonstrate that 

essentially 100% of the total mass of trichloromethylsilane released into  

an environmental compartment (i.e., air, water, or soil) will be degraded  

within that compartment.  As expected on the basis of the Level-II  

simulation (Table 3), emission of trichloromethylsilane directly to air  

results in 100% of the total chemical mass residing in the air  

compartment, with degradation in air accounting for >99% of the total  

mass removed from the local environment (Table 4a).  Similar results were  

obtained when trichloromethylsilane was released directly to soil (Table  

4b) or water (Table 4c).  In all simulations, intermedia exchange of  

trichloromethylsilane between the other compartments was insignificant  

and advective losses represented only a minor amount of the total  

chemical mass (< 0.1%) removed from the system.  Persistence of  

trichloromethylsilane in the model system was about 0.04 hours (2 min).

Table 4a.  Distribution and environmental residence time of  

trichloromethylsilane emitted to the atmospheric compartment, based on  

Level-III fugacity modeling.
Emission Rates (kg/h):  Air = 1000; Soil = 0; Water = 0
        Environmental Compartment
                        Air        Water        Soil        Sediment
Distribution (%)        100        0.0        0.0        0.0
Reaction losses (%)        100        0.0        0.0        0.0
Advective losses (%)        0.0        0.0                0.0

Overall residence time (h)        0.04
Reaction residence time (h)        0.04
Advective residence time (h)        100

Table 4b.  Distribution and environmental residence time of  

trichloromethylsilane emitted to the soil compartment, based on Level-III  

fugacity modeling.
Emission Rates (kg/h):  Air = 0; Soil = 1000; Water = 0
        Environmental Compartment
                        Air        Water        Soil        Sediment
Distribution (%)        0.1        0.0        99.9        0.0
Reaction losses (%)        0.1        0.0        99.9        0.0
Advective losses (%)        0.0        0.0                0.0

Overall residence time (h)        0.04
Reaction residence time (h)        0.04
Advective residence time (h)        82,725

Table 4c.  Distribution and environmental residence time of  

trichloromethylsilane emitted to the water compartment, based on  

Level-III fugacity modeling.
Emission Rates (kg/h):  Air = 0; Soil = 0; Water = 1000
        Environmental Compartment
                        Air        Water        Soil        Sediment
Distribution (%)        0.0        100        0.0        0.0
Reaction losses (%)        0.0        100        0.0        0.0
Advective losses (%)        0.0        0.0                0.0

Overall residence time (h)        0.004
Reaction residence time (h)        0.004
Advective residence time (h)        999

Air % (Fugacity Model Level I): 99.5
Water % (Fugacity Model Level I): 0.4
Soil % (Fugacity Model Level I): 0

Applicant's summary and conclusion

Conclusions:

Results from the multimedia model simulations indicate that trichloromethylsilane will not exist in the environment. Rather, trichloromethylsilane will rapidly degrade (i.e., hydrolyze) to HCl and methylsilanetriol within the environmental compartment (air, water, soil) to which it was released. Because of the rapid rates of degradation, advective losses and intermedia exchange of trichloromethylsilane between other compartments are insignificant. However, the fate, transport, and distribution of the hydrolysis product, methylsilanetriol (see Tables 6a-6c in the General Remarks Section), is strongly dependant upon the environmental compartment in which trichloromethylsilane was originally released. For example, emission of trichloromethylsilane directly to air or soil results in 22-28% of the generated mass of methylsilanetriol partitioning to water and 72-78% partitioning to soil (Tables 6a and 6b). About 90% of the methylsilanetriol generated in air or soil is removed from the local environment through biodegradation in soil and water, with advective losses in water accounting for the remaining 10%. In contrast, > 99% of the methylsilanetriol generated from trichloromethylsilane emitted directly to the water compartment is retained in the water, with biodegradation accounting for 66% of the totalchemical mass removed from the model system (Table 6c). Global persistence of methylsilanetriol in the model system was about 22 days regardless if trichloromethylsilane was released directly to air (Table 6a), soil (Table 6b), or water (Table 6c). Hence, the environmental compartments of concern for trichloromethylsilane, based on formation of the degradation product methylsilanetriol (and ignoring the effects of HCl), are water and soil.