TABLE 2.
Atom percent excess of N measured in nitrogen fractions in sediment enriched with 15NH4NO3a
| Carbon treatment | Nitrogen fraction | Mean atom% excess (SEM) (n = 3) at:
|
||
|---|---|---|---|---|
| 6 h | 24 h | 48 h | ||
| Control | NO3− | 0.11 (0.04) | 0.51 (0.16) | 0.90 (0.26) |
| NH4+ | 31.38 (0.30) | 29.52 (0.30) | 26.51 (0.35) | |
| NO2− | 2.24 (0.63) | 3.73 (0.50) | 4.13 (0.79) | |
| N2O | 0.57 (0.14) | 0.53 (0.05) | 0.57 (0.07) | |
| Glycine | NO3− | 0.05 (0.01) | 0.62 (0.20) | 0.21 (0.01) |
| NH4+ | 23.25 (0.77) | 19.13 (1.52) | 14.32 (0.23) | |
| NO2− | 0.35 (0.02) | 0.51 (0.05) | 0.25 (0.04) | |
| N2O | 0.18 (0.06) | 0.30 (0.02) | 0.26 (0.02) | |
| Acetate | NO3− | 0.07 (0.02) | 0.05 (0.01) | 0.08 (0.01) |
| NH4+ | 28.92 (0.14) | 28.18 (0.16) | 27.45 (0.21) | |
| NO2− | 0.00 (0.00) | 0.03 (0.01) | 0.01 (0.01) | |
| N2O | 0.03 (0.02) | 0.07 (0.01) | 0.06 (0.01) | |
| Formate | NO3− | 0.20 (0.09) | 0.02 (0.00) | 0.05 (0.01) |
| NH4+ | 28.87 (0.09) | 28.20 (0.34) | 27.66 (0.27) | |
| NO2− | 0.00 (0.00) | 0.00 (0.00) | 0.00 (0.00) | |
| N2O | 0.02 (0.03) | 0.02 (0.00) | 0.00 (0.00) | |
| Glucose | NO3− | 0.18 (0.11) | 0.32 (0.17) | 1.12 (0.36) |
| NH4+ | 31.39 (0.35) | 28.33 (0.72) | 23.34 (2.45) | |
| NO2− | 1.03 (0.05) | 1.24 (0.21) | 0.59 (0.22) | |
| N2O | 0.41 (0.03) | 0.34 (0.02) | 0.30 (0.01) | |
a
15N was measured in nitrogen fractions during incubation of sediment enriched with 15NH4NO3 and supplemented with different sources of carbon at 1.0 g of C liter−1. NB, it is not possible to measure 15N enrichment of N2 under 15NH4NO3 conditions.