A commonly used agricultural herbicide, atrazine, was detected in ground water in the alluvial aquifer along the Platte River near Lincoln, Nebraska. Atrazine is not applied in the vicinity of the well-field, so it was hypothesized that ground-water withdrawals at the well field caused contaminated river water to move into the aquifer. Water samples were collected from monitoring wells located at different distances from the river near the well field. The data can be seen in the illustration above.

Question

A commonly used agricultural herbicide, atrazine, was detected in ground water in the alluvial aquifer along the Platte River near Lincoln, Nebraska. Atrazine is not applied in the vicinity of the well-field, so it was hypothesized that ground-water withdrawals at the well field caused contaminated river water to move into the aquifer. Water samples were collected from monitoring wells located at different distances from the river near the well field. The data can be seen in the illustration above.
Can you see any patterns of concentrations of atrazine in the ground water as indicated by the graphs? (Choose 3)
Responses
A	The closer the well is to the river, the lower the concentrations of atrazine.The closer the well is to the river, the lower the concentrations of atrazine.
B	Atrazine concentrations in groundwater were highest during July and early August.Atrazine concentrations in groundwater were highest during July and early August.
C	Atrazine in the river water can contaminate groundwater great distances from the original source of the herbicide.Atrazine in the river water can contaminate groundwater great distances from the original source of the herbicide.
D	Atrazine was present in groundwater throughout the year, regardless of the distance from the river.

GPT-4o mini · Answer

Based on the information provided, the patterns of atrazine concentrations in groundwater may include the following:

B. Atrazine concentrations in groundwater were highest during July and early August. C. Atrazine in the river water can contaminate groundwater great distances from the original source of the herbicide. D. Atrazine was present in groundwater throughout the year, regardless of the distance from the river.

A does not seem to be a valid pattern if the hypothesis suggests that contaminated river water is moving into the aquifer, likely resulting in higher concentrations closer to the river. Thus, the selected patterns are B, C, and D.