Estimation of Greenhouse Gases in the Ambient Air

At present scenario, estimation of Greenhouse Gas (GHG) emission in the ambient air has becomes a major concern. Emission of GHG has the direct linkage with ambient air pollution and also poses global environmental threats and challenges. Though several scientists are working to mitigate the emission of GHGs but till date no mitigation/management plan has been implemented in global scale. The emission of GHGs are in general from multiple sectors like energy, industry, waste management plant, agricultural sector etc. The major GHGs are methane (CH₄), carbon dioxide (CO₂) and nitrous oxide (N₂O). In the present study GHG (CH₄, CO₂ and N₂O) fluxes have been reviewed from wastewater treatment plant (WWTP), constructed wetlands (CWs) and irrigated rice fields (IRF) in India and compared with other countries like Australia, Europe and China. The emission of CH₄, CO₂ and N₂O fluxes from WWTP in Australian condition varied in an average from 0 to 111, 0 to 769 and 0 to 3 ton/year respectively whereas in Indian condition CH₄ and N₂O fluxes varied in an average from 0 to 6, and 0 to 0.01 ton/year. The higher emission of CH₄ and N₂O in Australia might be due to higher capacity of WWTP and advance biological treatment plant as compared to India. In Indian and China climatic condition the emission of CH₄, CO₂ and N₂O fluxes from IRF varied from 107 × 10⁴ to 110 × 10⁴, 2116 × 10⁴ to 6096 × 10⁴ and 4 × 10⁴ to 5 × 10⁴, 644 × 10⁴ to 1202 × 10⁴, 205 × 10⁴ to 1208 × 10⁴ and 29 × 10⁴ to 41 × 10⁴ ton/year respectively. The higher fluxes of GHG w.r.t CH₄ and N₂O might be due to continuous flooding in China, application of nitrogen fertilizers in large scale in the rice field, and likely to be due to overburden pressure for production of rice as compared to India. CWs are the well-known natural CH₄ producer in the atmosphere. The emission of CH₄ from CWs in India and Europe varied from 46 to 1103 and negative to 38,000 mg/m²/day respectively. CH₄ emission depends on tropical coastal wetland condition and type of surface flow in the wetland. India is fewer producers to GHGs as compared to other countries. Appropriate management plan will further reduce the emission of GHGs as well as ambient air pollution.