Modelling Emissions in the Air

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23/09/19 Sciences Reference this

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Table of Content

1.1 Nomenclature…………………………………………………………………………. 3

1.2 Chemical and physical property………………………………………………………3

1.3 Impurities and stabilizers……………………………………………………………..4

1.4 Production……………………………………………………………………………..4

1.5 Uses……………………………………………………………………………………..4

2.1 Input data in EQC model……………………………………………………………..5

2.2 Level one assessment………………………………………………………………… 6

2.3 Level two assessment………………………………………………………………….7

2.4 Level three assessment………………………………………………………………..8

2.4.1 Emission in sediment ( consider this as case 1)……………………………………8

2.4.2 Emission in air ( consider this as case 2)…………………………………………..9

2.4.3 Emission in soil (consider this as case 4)…………………………………………..9

2.4.4 Emission in soil (consider this as case 4)…………………………………………10

 

 

Introduction

1.1 Nomenclature

IUPAC name: Trichloroethene

Abbreviation: TCE, trichloro, Trike, Tricky and tri

Trade name: Trimar and Trilene

Molecular structure: There are 3 atoms of chlorine and one atom of hydrogen. There is a double bond connecting carbon.

 

1.2 Chemical and physical property

 

Characteristics: Trichloroethylene is a clear, colourless, non-viscous liquid with slightly sweet odour. Its odour is similar to chloroform ( McNeill, 1979).It has molecular weight of 131.4 g/mole and is unsaturated and chlorinated compound (Schaumburg 1990). It is a strong solvent for large number of natural and synthetic substances. It has melting point of -83.5’C and boiling point of 86.7’ C. TCE had high density (1.46 g.m l-1 at 20’C) and low surface tension of 0.029 N/m compared to water. Vapour pressure is heavier than air (Eisenreich et al. 1981; ATSDR 1989).

Solubility: TCE has moderate aqueous solubility of 1450 mg/L (arithmetic mean of 7 values; coefficient of variation 15%; Hsieh et al. 1994).

Vapour pressure: The vapour pressure of TCE at 25’C is 9700 Pa (Hsieh,1994) while at 5’C the vapour pressure is 3500 Pa.

Henry’s law Constant (H):Trichloroethylene has a Henry’s law constant of 890 Pa-m3/mol at the temperature range of 20-25’C (Hsieh et al 1994).

Stability: The chemical is stable in air while it is unstable in light and moisture (Browning, Tox

Metab Indus Solv, 1965 and Osal, 1980).

Reactivity: Incompatible with alkalis and chemically active with metals such as barium, lithium, sodium and beryllium (NIOSH Pocket Guide Chemical Hazards, 1994).

Organic Carbon-water partition coefficient (Koc): Hsieh et al. (1994) estimated the Koc of trichloroethylene to be 86. The coefficient was estimated based on the arithmetic mean of 13 measured values.

1.3 Impurities and stabilizers

 

Trichloroethylene produced for reagent uses has maximum purity of 99.8% while the commercial product may contain impurities.

1.4 Production

 

Trichloroethylene is generally produced using chlorination of either ethylene or ethylene dichloride. The chemical was produced at two plants in Canada; both in Shawinigan, Quebec.

The maximum production was done in the year of 1970 which was as much as 22.5 kilotonnes.

However, later these plants closed , due to decrease in domestic demands. The production of TCE declined and in 2001, the total domestic demand in Canada was 2.4 kilotonnes, which was met entirely through imports. Total Canadian imports of trichloroethylene were 1.6 kt, of which 0.1 kt was re-exported (CIS 1991).

1.5 Uses

 

The domestic use is the major use of trichloroethylene in Canada. It is used for vapour degreasing and cold cleaning of fabricated metal parts in automotive and metals industries (CIS 2002). As per Health Canada (2004), 90% of total domestic use of TCE is used in metal degreasing applications.  Minor uses include the production of adhesive, household and industrial der cleaning, textile manufacturing, cleaning of electronic components, paint removal and laboratory applications (Bruckner, 1989).

Majority of TCE used is emitted in the environment instead of destroying it. Both the closure of both Canadian plants, the chemical was used to sysnthesis tetrachloroethylene (CPI 1986).

Modelling Results and Discussion

 

2.1 Input data in EQC model

 

Following are the data used in the EQC model:

Chemical name: Trichloroethylene

Chemical type:1

Data temperature: 25’C

Reaction half-life of Air: 84 hours

Reaction half-life of Water: 2880 hours

Reaction half-life of sediments: 5280 hours

Reaction half-life of Soil: 22320 hours

Water solubility: 11g/m2

Vapour pressure: 9700 Pa

Log Kow: 320

Melting point: 189.7

(Picture 1: input data in EQC model)

2.2 Level one assessment

 

Level one calculation of trichloroethylene is shown in the picture below. The level consist of air water, soil and sediments. It shows the concentration and amount in each phase. The level is based upon concentration difference and equilibrium concepts. It is simple calculation but it can become tedious sometimes.

According to the picture, the concentration in air is 1000ng/m3 while the amount is 99995 kgs.

The amount for soil is 1.20 kg while for water and sediments is 4.28 kg and 0.026 kg.

The concentration of soil is 5.55 e^-05, water is 0.0214 ng/L and sediments is 1.11e^-04.

Fugacity in level on does not changes. As there is no effect of advection and reaction in level one, there is no loss in level one.

As the concentration of TCE is more in air it can be said that the chemical is more liking toward air compared to other mediums.

(Picture 2: Level one calculation)

2.3 Level two assessment

 

Level two calculation consist of advection and reaction, due to which there is loss from the system; otherwise there is no major change in the calculation of level one and level two. Picture 3 shows the EQC model data of level two calculation of trichloroethylene. Assessment of each medium is states below:

Air: The concentration in air is 548ng/m3 and the amount is 54794 kg. As mentioned above the loss by advection is 548kg/h and loss by reaction is 452 kg/h. Thus, the total loss from air is 1000kg/h.

Water: The amount of water in system is 2.34kg while the concentration is 0.0117 ng/L. loss by advection is 2.34e^-03 and reaction is 5.64e^04.  The loss by reaction is more than advection.

Sediment: The amount of sediment in system is 0.0146kg and the concentration is 6.08e^-05ng/g solids. The system loss more in reaction then in advection as the loss by advection is 2.92e^-07 and the loss by reaction is 1.91e^-06.

Soil: There is only 2.04e^-05 loss in soil phase and that is by reaction. The concentration is 3.04e^-05 ng/g solids and amount is 0.867 kg.

(Picture 3: Level two calculation)

Thus, the maximum loss is from air and least is from sediments. From the picture it can be stated that trichloroethylene is more likely to stay in air medium.

2.4 Level three assessment

 

In level three the system is not in equilibrium; as a result it represents the true picture of environmental conditions. In this level there is a clear study of fugacity which shows the direction of mass transfer, intermediate transfer rates between all phases and D values which gives residence time. Even in level two there are two types of losses- reaction and advection.

There are four condition which we have considered:

Emission from air, emission from water, emission from sediments and emission from soil. We selected the various categories so that we can study chemical fate in different medium.

2.4.1 Emission in sediment ( consider this as case 1)

The emission in sediments is considered as 1000kg/h. In sediments, the concentration is 4077 ng/g solids and amount is 1.29e^06 . Fugacity is calculated at 693 Pa. The loss by advection and reaction is 25.9 and 170 respectively.  Considering the fugacity of water (0.948 Pa), the mass transfer will travel from sediment to water as the it travels from higher fugacity to lower fugacity. As compared to level two the losses and concentration from sediments have increased.

In the case of air and fugacity the fugacity of water is more and hence the mass transfer will take from water to air. Again loss and concentration increased as compared to level 2. The loss from air is decreased as compared to level two. As fugacity is same in air and soil there is no mass transfer. Figure 4 shows the picture of level three calculation-emission in sediments.

(Picture 4: Level three calculation- emission in sediments)

2.4.2 Emission in air ( consider this as case 2)

Fugacity in air is more as compared to water and thus the mass transfer will take from air to water. The loss and concentration from air is same as level two but it is more as compared from level three calculation – emission from sediments. In the case of water and sediments, the fugacity in water is slightly more then sediments. Again the fugacity in air and soil is same. Loss from air is more and it is least from sediments. Total residence time of system, reaction and advection has decreased as compared to case 1. Thus it is not as harmful as case one.

(Picture 5: Level three calculation – emission in air)

 

2.4.3 Emission in water ( consider this as case 3)

Comparing the fugacity of water in all the three cases uptil  now ( case 1, case 2 and case 3), the maximum fugacity of water is in case 3. Fugacity of water is more than both air and sediments in case 3. Thus the mass transfer is from air and sediment to water. Loss from water increased as compared to both the above cases.

The total residence time of the system is more than case two but less than case one. As a result, case 3 is more harmful then case 2 but less then case 1. Again the concentration has increased as compared to both the above cases.

(Picture 6: Level three calculation – emission in water)

 

2.4.4 Emission in soil (consider this as case 4)

 

Fugacity and amount is more in this case as compared to air water and sediments. In this case the loss from advection and reaction is more from air then water and sediments. Fugacity of soil is more thus mass transfer will take from soil to air. Again the mass in air is more than other phases, thus trichloroethylene is more likely to stay in air. Comparing the residence time of the total system of case 4 with above cases then it is less as compared to case 1 and case 3 but it is more in case 2. Thus this case is less harmful then case 1 and case 3 but a little harmful then case 2.

 

 

 

 

 

Conclusion

From the study of EQC model results, it can be stated that the chemical trichloroethylene likes to stay more in air as compared to other phases. As we know chemical like to stay in more in air then we have to take appropriate measuring steps to reduce this rate so that it do not harm environment badly.

References

  • ATSDR (Agency for Toxic Substances and Disease Registry), 1997. Toxicological Profile for Trichloroethylene. U.S. Department of Health and Human Services.
  • Bruckner, J.V., B.D. Davis, and J.N. Blancato. 1989. Metabolism, toxicity, and carcinogenicity of trichloroethylene. Toxicology. 20(1): 31–50.
  • CIS (Camford Information Services). 2002. CPI Product Profiles: Trichloroethylene. Toronto, Ontario.
  • CPI. 1986. Canadian Process Industries (Corpus Information Services), Don Mills, Ontario. Trichloroethylene. 3p.
  • Eisenreich, S.J., B.B. Looney, and J.D. Thornton. 1981. Airborne organic contaminants in the Great Lakes Ecosystem. Environ. Sci. Technol. 15:30–38.
  • Hsieh, D.P.H., T.E. McKone, F.F. Chiao, and R.C. Currie. 1994. Intermedia transfer factors for Contaminants found at hazardous waste sites. Trichloroethylene (TCE). Risk Science Program (RSP), Department of Environmental Toxicology, University of California, Davis, California 95616.

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