Deck 24: Dispersion Modeling in Air, Water, and Soil: Likely Route of Exposure and Most Sensitive Organism Based on Dispersion and Concentration

Question 1

In a framework for comparative toxicity assessment of Figure 24-2 (in the text) , what are differences between calculating human versus ecosystem effects?

Answer 1

One critical assumption is that the human spends only a given amount of time in the affected area and obtains a dose rather than a concentration that other species may have no ability to escape. This may work for some circumstances, but may not apply to air or water pollution in a city in a developing country where environmental regulations are not very strict or well-enforced.

Question 2

Why is concentration in air, water or soil models worst case in the U.S.?

Answer 2

All environments cannot be measured at every height and distance so computer modeling makes best use of the topography, geology, soils, flow rate of rives, weather, etc. to derive an environmental concentration that would be based on the highest output and concentration that a smoke stack, pipe, etc. would deliver to the environment and its concentration at a point outside the property line of the emitter where humans and other species might encounter the toxicants.

Question 3

Why is a plume model used in air, soils, and other dispersion calculations?

Answer 3

Usually there is a source and a direction of flow that determines a plume and its dispersion. Concentrations can be predicted or plotted over time to see how the plume may affect certain populations and note changes in the plume that might change future expansions that affect other populations.