Click on image to view larger version.
Fig. 10. Boxplots of 
15N-NO3 and nitrate N concentrations in stream-edge (Nest E) wells of Transects 3 and 6, showing trends with depth. The 15N enrichment is pronounced only in shallow wells, indicating little denitrification in deeper stream-edge wells. This limited nitrate attenuation allows the off-site export of sprayfield nitrate via discharge of high-nitrate ground water to the stream that drains the sprayfields and then enters Stewarts Creek. Boxes enclose the upper and lower quartile (25%) of data about the median, which is represented by a horizontal line within each box. Whiskers above and below boxes represent the upper quartile plus 1.5 times the interquartile distance (IQD) and the lower quartile minus 1.5 times the IQD. Outliers are represented by circles.
