Atrazine is the second most widely used herbicide in the US. The EPA estimates that 80 million pounds are used annually. In 2001, over 7 million pounds of atrazine were used in Indiana, and over 12 million pounds were used in Illinois. Because atrazine has been linked to health problems, the US Environmental Protection Agency has established a drinking water standard for atrazine of 3 parts per billion, or 0.003 mg/L. Atrazine has been under review by the USEPA and a regulatory decision is anticipated in 2016.
Calculations – to be handed in during class
Consider an agricultural watershed with an area of 7000 hectares (ha). A stream drains the watershed into a lake with a surface area of 36 ha and a depth of 5 meters. The outflow of the lake is 118 liters per second. A nearby town uses the lake as a water supply. Atrazine is applied to the watershed each year at an average rate of 0.045 kg/ha. Answer the following questions:
1. In one year, how much atrazine is applied to the watershed in total?
2. If, during a normal year, 3 % of the total atrazine applied to the watershed was washed off the fields by rain storms and transported to the lake, what would be the resulting concentration of atrazine in the lake? Express your answer in parts per billion. . (HINT: first calculate the volume of the lake, then determine the atrazine concentration in the lake.).
3. Calculate the average residence time of Atrazine in the lake.
In wet years as much as 7% or more of total Atrazine applied can be lost to surface water sources. Please write a policy memo that persuades policy makers either in favor of the continued use of Atrazine or to ban Atrazine as the UK has already done. Please address the following questions in the memo and address the concerns that may be present.
• The towns concern about their drinking water supply in this scenario?
• What type of pesticide atrazine is and how long is remains in the environment?
• the effects of atrazine on human health
• the effects of atrazine on wildlife
• Impact of atrazine on groundwater
• the implications to farmers if Atrazine was banned, ie address cost benefit issues if a ban