Dimensions are 40m by 10m A chemical tanker truck was driving on Pleasant Valley Way (a road that goes by Diamond Mill Pond) and the driver fell asleep and crashed into the pond. There was a spill of 50 kg of Atrazine (a common Herbicide). If we are trying to determine the fate and transport of the spill we should try to figure out how and if it will travel through the system. Assume there is no reaction occurring in the system. For all the scenarios below maintain the same flow rate and dimension as identified in problem 1. 2. Scenario one. If we assume that the Atrazine will only travel through the system in the water. Assume the pond has the dimensions above (question 1) and the flow is constant and uniform. If we have a Longitudinal Mixing coefficient of 0.1 m/min, how long will it take for the center of mass to leave the pond? 3. Scenario two. If we assume the pond is a completely mixed reactor and the atrazine will only travel in the water phase. How long will it take for the atrazine to decrease in the system to a level below the surface water quality standard of 760 ug/L? 4. Scenario three. If we assume that the Atrazine will bind with the surficial sediments at the bottom of the pond. Simulate the pond as a completely mixed reactor with the same dimensions as in problem 1. The soil that is exposed to the Atrazine in the water is the uppermost 10 cm of the sediment which has a mass of 130 kg/m2 of the lake bed. It has an organic fraction of 11% and the distribution of atrazine between the water and sediment is always at equilibrium. If we assume that the release is instantaneous and the entire 50 kg is distributed throughout the model domain and no new atrazine is added to the pond, how long will it take for the atrazine to decrease in the system to a level below the surface water quality standard of 760 ug/L? 5. Based on your knowledge from this class (including the chemical parameters for Atrazine) (a.) which of the 3 scenarios presented above is the most appropriate? (b.) If you were the environmental profession who was given the task of simulating this spill what additional scenarios would you propose and why? 6. It has been suggested that aeration of Diamond Mill Pond could be a method to remove the Atrazine from the water. If we disregard any interactions that the atrazine has with sediment and model this process as a completely mixed reactor with air flowing through the pond. Is this and efficient system that can get the atrazine to decrease in the system to a level below the surface water quality standard of 760 ug/L? Use an air flow rate of 100 m3/min, assume that the influent air is free of atrazine and the water and air reach equilibrium as the air bubbles travel through the water column. (Hint: write out a mass balance of all losses from the system)
