Zinc (Zn) affects nitrogen cycling but the effect of Zn in wastewater on the emission of
nitrous oxide (N2O) from the soil has not been reported. This study compared N2O emissions
from mangrove soil receiving livestock wastewater containing various Zn2þ concentrations
and evaluated how long the effects of Zn would last in these soil-wastewater
microcosms. Significant increases in N2O flux were observed soon after the discharge of
wastewater with a low Zn content. On the other hand, the flux was reduced significantly in
the wastewater with high Zn levels but such inhibitory effect was not observed after tidal
flushing. Continuous monitoring of the N2O fluxes also confirmed that the inhibitory effect
of Zn was confined within a few hours and the fluxes recovered in 6e9 h after the
wastewater was completely drained away. These results indicated that the inhibitory effect
of Zn on N2O fluxes occurred immediately after wastewater discharge and disappeared
gradually. In the surface soil, nitrate levels increased with the addition of wastewater but
there was no significant accumulation of NHþ
4
N, irrespective of the Zn content in the
wastewater. The study also showed that nitrification potential and immediate N2O emissions
were inhibited by high Zn levels in the soil, but the total oxidation of ammonium to
nitrate was not affected.