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Category for ground water

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Lu Chen
Lu Chen's picture
Category for ground water

I am wondering if I want to calculate the Human toxicity of Hydrofracking chemicals in groundwater which category I should use, soil or water? Or I need to calculate CF by myself? 

Another thought is that it might be better to focuse on aquatic resource instead of human toxicity. What do you think?

USEtox Team
USEtox Team's picture
Emissions to groundwater

Thank you for your question.

Hydrofracking chemicals may certainly be a human toxicity concern and exposure via drinking of groundwater might be a related important exposure pathway.

For fracking process emissions, USEtox is not the appropriate model and, instead, another model should be used to predict the transport to and pollution of the higher saturated zone.

Lu Chen
Lu Chen's picture
Thank you for your response.

Thank you for your response. Could you specify which model is more appropriate?

 

USEtox Team
USEtox Team's picture
Emissions for hydrofracking chemicals

The actual emission compartment for hydrofracking chemicals is deep (very deep) soil, where there will be limited microbial degradation of the chemicals and the main route of exposure will go through upwelling and contamination of the groundwater layers that are used for drinking water. To model this with USEtox, it is necessary to model this pathway and bring the chemicals that are emitted very deep in the soil up to a level where they actually reach a layer that can be used as emissions in models like USEtox (like e.g. freshwater). Hydrofracking industry must most likely do risk assessments and hence this would be the place to look for models that can appropriately model this pathway. In LCIA, we currently do not know of any such model.

D_Avila
D_Avila's picture
Chemicals used in hydraulic fracturing.

Assuming that the chemicals flow back in the water (which they do) and having an inventory table with volumes and mass of the chemicals used. The main problem then becomes the substances that are used. Most of them are inorganic substances. Is it possible to include these in USEtox or not at all?

Do you recommend any other methodology suitable for this? What is insightful of USEtox, is the endpoint CF which can be translated to a number that policy makers can understand (with the corresponding uncertainty). Any recommendations on this?

 

USEtox Team
USEtox Team's picture
Inorganic substances in USEtox

Inorganic substances other than metal ions, such as cyanides or bromides, can currently not be characterized in USEtox. What is needed to characterize inorganics in USEtox is to account for the complex reaction chemistry in the environment, which is currently missing in USEtox and any other LCIA models. As first proxy, the LCA practitioner could try to find all related reaction products of emitted inorganic substances and their contributing mass fraction and use these as emitted substances in USEtox. If the reacation products themselves are still inorganics, they cannot yet be characterized.

The USEtox team is currently working in a PhD project on characterizing inorganic substances in LCA, and first results are expected by end of 2018.