Keywords: monitoring Systems: groundwater Substances: 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 4-Acetamidoantipyrin ( N-Acetyl-4-Aminoantipyrin 4-AAA) (OIAGWXKSCXPNNZ-UHFFFAOYSA-N) 2 -2 -Difluorodeoxyuridin (FIRDBEQIJQERSE-QPPQHZFASA-N)