Fig. 9. ¹⁵N-NO₃ values vs. depth (m). Well 3E-S had the most positive shallow well ¹⁵N value (in August, 1996). Well 1E-I had the least positive ¹⁵N value (in April, 1997). Well 3B-D showed several very positive ¹⁵N values, with dissolved oxygen < 2 mg/L and pH > 5. This well is within an organic silt layer (see Fig. 2b).