Emission of Greenhouse Gases due to River Pollution

Greenhouse gases and environmental pollution are directly linked. We need to rethink the role of river pollution in greenhouse gas emissions and how cleaning rivers can contribute to the prevention of climate change.

Derrick Yuk Fo Lai is a Professor in the Department of Geography and Resource Management at the Chinese University of Hong Kong. With information from river studies, he said,

“By greenhouse gases, we basically mean carbon dioxide, methane, and nitrous oxide. Examination of water samples collected from polluted rivers showed that the amount of these three gases in the rivers of Hong Kong was excessive. Surprisingly, 4.5 times more than the presence of these gases in the air in multiple samples were found in river water.”

Professor Lai’s research clearly demonstrated that river pollution has a direct role to play in climate change. As part of this research project, a sample of all the rivers in Hong Kong that were listed and tested was found to have almost the same picture. That is, a large part of the presence of greenhouse gases in the atmosphere comes from polluted water bodies. 

In addition to some of the common causes behind the excessive presence of carbon dioxide, methane, and nitrous oxide in the atmosphere, there are also gases from polluted river water. Research data suggests that ensuring quality purity of river water will improve riverine ecosystems, which will also reduce the rate of environmental pollution.

There are multiple causes of river pollution. When a cattle farm is set up along the river, the wastes of the animals living there often fall into the river. The design of drainage systems in various old buildings dates back to the Mandhata period, due to which the polluted water mixes directly with the river water. Sewage disposal systems in various installations, factories, and cities are so faulty, incomplete, and weak that they are dumped in river water before treatment. Due to these factors, the presence of carbon dioxide, methane and nitrous oxide gas in Hong Kong’s highly polluted rivers was 2.2, 1.5 and 4.0 times higher than that of ordinary rivers, respectively.

A research project on river pollution was conducted under the leadership of Long Tuan Hao, a postdoctoral researcher at Ghent University in Belgium. At the end of the project, rivers’ global warming potential (GWP) increased tenfold as pollution levels increased. When the quality of river water drops from acceptable levels to contaminated levels, there is evidence that carbon dioxide, methane, and nitrous oxide levels in the water have increased by 10% and 15%, respectively. 

Greenhouse gases are usually based on carbon or nitrogen. When human waste, sewage, livestock waste, factory waste, etc. are mixed in a pure river, the various activities of microorganisms living in the aquatic ecosystem of the river convert the nitrogen and carbon in this waste into greenhouse gases. Anaerobic bacteria (which cause anaerobic respiration) accelerate the production of carbon dioxide and methane from various organic matter, especially when the amount of dissolved oxygen is reduced due to pollution in a body of water. Denitrifying bacteria, on the other hand, convert nitrate into nitrous oxide. 

So much can be claimed from multiple studies conducted in different countries that it is important to look at river pollution from now on and the steps generally taken in environmental pollution. Even if river pollution is left out of the discussion, we have yet to find a significant solution to the catastrophic climate change that is taking place through the emission of greenhouse gases from a variety of conventional sources. To solve the problem of global warming, scientists need to think holistically. 

Members of the Water and Development Research Group at Alto University in Finland were surveyed in 2011. According to the survey, more than half of the world’s population lives within three kilometers of a freshwater reservoir. Excessive urbanization has reduced both the number and size of villages. On the other hand, naturally, new settlements, the growth of factories, etc., are being built around the reservoirs for the growth of urban areas. The settlement is getting closer and closer to the reservoir. Due to the increasing growth in urban areas, 80% of municipal waste is being discharged directly into some reservoirs. Most of these wastes come from untreated sewage, agricultural residues (fertilizers, pesticides), and stored silt. 

Environmental pollution, climate change, global warming, the problem of greenhouse gases, whatever they may be, must be addressed with the river in mind. The clearer the river water, the closer it will be to normal levels of clean water, the fewer greenhouse gases will be available. If the level of pollution in the river water is tolerable, there will be no opportunity to produce carbon dioxide, nitrous oxide, methane or pollutants. Research also shows that the amount of greenhouse gases in the water has decreased significantly after the water of the already polluted river has been cleaned. 

So is river cleaning the only solution? Giving this all a quick read, it seems we are pretty much in agreement. Because it will indirectly encourage more pollution. No matter how polluted the river is, the way to clean it is still open. An even more sustainable solution is to focus on minimal pollution. Prevention is better than cure.