exceeded the ES. However, total atrazine concentrations began increasing again and by
5/20/93 deisoproplyatrazine began appearing in the wells (except well 1 where it had
been present since 10/8/91) and a third metabolite, diaminoatrazine which had been
added to the analysis, was also present. Diaminoatrazine exceeded PAL in all 6 wells
and 4 of these wells had total atrazine concentrations exceeding the ES. However it is
necessary to add that in 1993 and 1995 other triazine products were used at this study
site (Cyanazine (Bladex), 1993; Simazine (Princep) and Cyanazine (Bladex), 1995).
Diamino and Deisopropylatrazine are also metabolites of these 2 products.
Concentrations of diamino and deisopropylatrazine peak in 1993 and 1995 which may be
attributed to the application of these other triazine products.
The data from the last sample set taken on 5/17/95 indicate that well 1 and 5
exceeded the ES, wells 2, 3, and 4 exceeded the PAL, and well 6 has no detect of
atrazine or metabolites.
The study site near Muscoda in the LWRV is- one of the most vullnerable settings
in the state of Wisconsin. The Sparta loamy fine sand overlays a shallow aquifer which
ranges from 4 to 10 feet below the ground surface. With irrigation scheduling, water is
applied at rates to meet the needs of the crop. However, large rainfall events and
rainfall that occurs soon after irrigating causes water movement beyond the root zone,
and leachable materials in the soil, such as nitrates, move with it.