Greenhouse gas concentrations in tropical wetlands of the Cross River estuary, Nigeria

Abstract

The Cross River estuary is a coastal wetland in the south-eastern part of the Niger Delta region of Nigeria with its hydrological cycle largely dependent on precipitation. The purpose of this study was to determine the greenhouse gas (GHG) concentrations in water from selected wetlands in the Cross River estuary. Water samples were collected from the Ikang, Anantigha and Adiabo wetlands and the major GHGs were analysed using a gas chromatography coupled to a mass spectrometer. The mean concentration levels of carbon dioxide (CO2), nitrous oxide (N2O) and sulphur oxide (SO2) were measured in the water samples for both seasons. There was a significant difference in concentrations of all the greenhouse gases in the water samples for both seasons. The exceptions were: SO2 in Adiabo, CO2 in Anantigha and N2O in Ikang, which showed insignificant differences for both seasons. The water CO2 concentrations from the Adiabo wetland recorded the largest contribution of greenhouse gas levels, ranging between 6.88 ± 2.22 ppm and 11.02 ± 2.52 ppm. These levels were in the range of those reported in the Congo basin. The variation in concentrations could be due to location, hydrological characteristics, nutrient load injection or the nitrification and denitrification processes of wetlands.