Assessing seasonal variation of diffusive nitrous oxide emission from freshwater wetland in Keibul Lamjao National Park, Manipur Northeast India

Abstract

Nitrous oxide (N 2 O) is an important atmospheric trace gas that contributes to the present global warning and is responsible for the destruction of stratospheric ozone. The emission of N 2 O from the natural freshwater wetland to the atmosphere is poorly understood. We investigated N 2 O flux using the static chamber method and their controlling factor in the freshwater wetland of Keibul Lamjao National Park (KLNP), Manipur. The overall mean N 2 O flux from the park was 0.10 ± 0.04 μg m −2 d −1 . Nitrous oxide emission showed evident seasonal changes, the highest flux occurring in the summer (with a mean value of 0.14 ± 0.02 μg m −2 d −1 ), while the lowest flux appeared in the winter (0.05 ± 0.01 μg m −2 d −1 ). There were significant seasonal variations of N 2 O emission. The NH 4 + – N and NO 3 − – N have a significantly positive correlation with N 2 O flux (p < 0.001). By comparing the slopes of the regression equations obtained between the emission of nitrous oxide and the content of NO 3 − – N and NH 4 + – N in water, we found that N 2 O flux were predominantly by NH 4 + – N. The results imply that nitrification played a crucial role in N 2 O emissions from the wetland park. Additionally, the decay of submerged macrophytes in the lake contributes to N 2 O flux, particularly during the summer. • KLNP is a wetland protected area in the Eastern Indian Himalayas. • N 2 O flux was measured in the wetland of KLNP. • The emission of N 2 O from the wetland showed seasonal variation. • Nitrification is the major contributor to the N 2 O emission in KLNP.