Fig. 5. Distributions of reconstructed ¹⁵N[NO₃^–]⁰ of ground water (including undenitrified samples) compared to points (diamonds) showing ¹⁵N for surface soils, and box plots of ¹⁵N values for aquifer sediments at all study sites. Values of ¹⁵N are given with respect to air N₂, in parts per thousand. For the box plots, error bars show the minimum and maximum values, boxes show the interquartile range, and horizontal lines show the median.