Based on the responses you've provided, the following three patterns regarding the concentrations of atrazine in groundwater can be identified:
B. Atrazine concentrations in groundwater were highest during July and early August. - This indicates a seasonal pattern where atrazine levels increase during specific months, likely linked to agricultural practices during the growing season.
C. Atrazine in the river water can contaminate groundwater great distances from the original source of the herbicide. - This suggests that atrazine has the ability to migrate through the environment, emphasizing a concern for its movement from surface water to groundwater.
D. Atrazine was present in groundwater throughout the year, regardless of the distance from the river. - This indicates a consistent presence of atrazine implying that it may be pervasive in the groundwater system, not just limited to areas close to the river.
These three responses highlight seasonal variations, the potential for widespread groundwater contamination, and the persistent nature of atrazine in the environment.