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Comparison of nitrite (NO2-N) production over time in groundwater under denitrifying conditions in the absence (CK) or presence of (a) sulfamethazine (SM-0.01, -0.1, and -1.0 mg/L) and (b) chlortetracycline (CT-0.01, -0.1, and -1.0 mg/L). Same letters above each bar indicate no difference between different treatments at a 0.05 significance level of the Tukey's studentized range test.
