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Variation in results, freshwater ecotoxicity

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D_Avila's picture
Variation in results, freshwater ecotoxicity

Dear USEtox team,

I recently graduated from Industrial Ecology. I assessed more than 38K fracking wells from USA which I simulated in Mexico.

I wonder if my regions are so different among them, why the impacts that relate to ecosystem quality are almost the same across them. I attach a table with the regionalization and the resulting impact assessment. The different colors correspond to seven different energy scenarios I have assessed in each region and refer to the median of all the wells.






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USEtox Team
USEtox Team's picture
Spatial variability in freshwater ecotoxicity

Depending on chemical properties, the concentration in freshwater will vary substantially if the water volume or source vary a lot, in particular for short-lived substances (see the respective main diagonal element of the fate factors matrix in the RUN sheet of the USEtox model file). However, the time and space integrated increase in concentration which is used to calculate the ecotoxicological impact will be nearly the same, unless the removal rate changes substantially (e.g by having  a reduced compartment height or depth... if either volatilization or sedimentation are important removals - or an increased advection if chemical persistence is high).

If you are interested in looking at the difference in increase in concentration (and not just chemical mass), you might divide the fate factor [kg in freshwater per kg emitted/day] by the different volumes [m³], to get the concentration [kg/m³] increase in freshwater per kg emitted/day. This will vary much more, but not necessarily the impact, since if volume increases you will mostly have a lower concentration but on a larger area.

In Kounina et al. and Wannaz et al., spatial variation of ecotoxicity factors is further discussed.