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.Atrazine was present in groundwater throughout the year, regardless of the distance from the river.

GPT-4o mini · Answer

Based on the scenario you provided regarding atrazine concentrations in groundwater near the Platte River, the following patterns can be observed from the responses given:

B. Atrazine concentrations in groundwater were highest during July and early August. - This response likely correlates with seasonal agricultural practices and herbicide application patterns, suggesting that atrazine levels could be affected by the timing of its use.

C. Atrazine in the river water can contaminate groundwater great distances from the original source of the herbicide. - This response supports the hypothesis that groundwater withdrawals may draw in contaminated river water, showing that the contamination can spread.

D. Atrazine was present in groundwater throughout the year, regardless of the distance from the river. - This indicates a persistent presence of atrazine in groundwater, suggesting that once introduced, it can remain detectable over time.

In summary, choices B, C, and D reflect observed patterns regarding the behavior and persistence of atrazine in the groundwater as influenced by seasonal changes, contamination sources, and distribution through the aquifer.