Biosphere‐atmosphere exchange of NO_<i>x</i> in the tropical mangrove forest

Abstract

Biosphere‐atmosphere exchange of NO x at the Sundarban mangrove forest along the northeast coast of the Bay of Bengal, India, showed uptake rates of −0.84 to −1.63 ng N m −2 s −1 during the day and both uptake and emission rates of −0.36 to 5.19 ng N m −2 s −1 during the night from September to February. However, during the period from March to August, NO x emission ranged between 0.34 and 2.13 ng N m −2 s −1 and 0.88 and 3.26 ng N m −2 s −1 in daytime and nighttime, respectively. During the postmonsoon period, NO x uptake could be attributed to mangrove stomatal activity during the day. Mangroves absorbed nitrogen from both the soil and the atmosphere. Seasonal and diurnal variability of NO x and O 3 is partly due to plant growth in the postmonsoon period. In addition to the NO x ‐O 3 photochemical cycle, stomatal uptake of NO x could also be an important process for keeping a low‐ozone state at the land‐ocean boundary of the northeast coast of the Bay of Bengal.