Fig. 8. Vertical variation of chemical and isotopic data at piezometer nest HC9, sampled 19–26 Apr. 1996 (Table 3). Data for excess N₂ were derived from measurements of total N₂ (Fig. 7). Measured values for selected sources of N (open circles) and S (open diamonds) are shown for comparison. X° and X indicate samples related by the reaction given in Eq. [4].