Chennai

Are Chennai’s kidneys packing up?

An aerial view of the Pallikaranai Marsh with the Thoraipakkam-Pallavaram Radial Road cutting through it. File Photo: Shaju John

An aerial view of the Pallikaranai Marsh with the Thoraipakkam-Pallavaram Radial Road cutting through it. File Photo: Shaju John   | Photo Credit: shaju John

Researchers at the Centre for Climate Change and Disaster Management at Anna University have been pointing out that unless the problems of garbage dumping and sewage inflow are addressed, the Pallikaranai Marsh will be unable to perform its vital function efficiently

In Samuel Beckett's play “Waiting For Godot”, the two main characters don’t get anywhere even in the rare occasions when they display some degree of decisiveness. At the end of the play, they are still where they began.

The narrative about the Perungundi landfill and the Pallikaranai Marsh is somewhat similar. There have been a lot of conversations and even some efforts in recent times to do something about the landfill that has been plonked in a wetland, which include reducing the amount of garbage reaching it, and still the problem seems ominously big.

During the decade that just passed into history, the Centre for Climate Change and Disaster Management (CCC&DM) at Anna University had been carrying out studies to assess how well the Marsh plays its role as natural kidneys in a urban expanse.

Over the years, the Marsh may have shrunk due to encroachments, and now reduced to a wafer-thin semblance of what it once was. However, the focus now is on what remains of the wetland and how to make it an effective filter, which is what wetlands are supposed to be. And how the landfill is queering the pitch, is an inextricable part of this narrative.

Environment scientists and researchers at CCC&DM point out that the Marsh is under-performing and also causing damage to the environment, due to the garbage piled up on one section and also the sewage and grey water that are flowing into it.

“Pallikaranai Marsh is a bad emitter rather than a good sinker. It emits considerable amounts of methane. It is supposed to function as a carbon sink, but it emits more carbon dioxide than it absorbs. As per our studies, the carbon sequestration potential of the wetland is 0.0020 Giga grams of carbon/year; and the wetland emits 26.6 Giga grams of carbon/ year. At this Marsh, the dissolved oxygen is considerably less, which pushes up the biological oxygen demand of living organisms,” says A. Ramachandran, emeritus professor, CCC&DM, who conducted the study “Identification of Pollution Source, Biodiversity Degradation and Adaptive Mechanism for Sustainable Management of Pallikaranai Marshland – Phase I”. The study was carried out on behalf of The Tamil Nadu Forest Department.

Though this study was carried out from 2010 to 2013, it gained traction around the corresponding time last year, around World Wetlands Day, when a seminar discussing the Marsh and its role as an ecosystem-regular was organised.

It is a moot point whether the message of this study has spurred a powerful wave of initiatives. As this study and a couple of others, conducted by the Centre, evoke a sense of urgency, their core message is being shared on the eve of another World Wetlands Day. Significantly, the theme of the Day this year is “Wetlands and Biodiversity” and this decade — 2020s — has been named the “United Nations Decade on Ecosystem Restoration”.

By their very nature, wetlands characterised as they are by anaerobic conditions, will generate methane as a natural process of organic matter (plants and animals) being decomposed as soil carbon — it is termed methanogenesis. However, there is cause for concern when the amounts of methane that are produced and let into the atmosphere are high. A high level of methanogenesis is a characteristic feature of wetlands marked by a great degree of pollution. As methane is one of the most significant greenhouse gases contributing to climate change, this is a really serious concern.

“The landfill on the Perungudi side of the Marsh is pushing methanogenesis to an alarmingly high level, due to the huge amount of biodegradeable waste from the landfill getting decomposed in the Marsh. Besides, heavy metal components – such as lead, chromium and iron – from the landfill leaches into the wetland, and poses a threat to the organisms in it. When the metallic concentration and other polluting material increase, the biological oxygen demand will be higher, due to reduced level of dissolved oxygen in the wetland. Due to the reduced dissolved oxygen, aquatic fauna will suffer,” says Ramachandran.

That takes us to the obvious question of reducing the garbage that reaches the landfill. In recent times, there has been considerable focus on composting at the residential and institutional level. Last year, the Greater Chennai Corporation shared information on how the amount of garbage reaching the landfill is being reduced, through composting of biodegradable waste as well as material-recovery initiatives related to dry waste and e-waste.

The sense one gets from scientific community’s view of the situation is that there has to be more of the good initiatives that are being carried out, and they have to be executed at a maddeningly accelerated speed.

“If this situation continues, without any strong intervention, there is a very high possibility that biological systems at the Marsh will collapse sooner than we expect. Diatoms, which form a carpet of green; algae and bryophytes will be hit. As the presence of lead and chromium is huge in the Marsh, this can affect the fish population significantly. Those fish species that are more resilient and survive the heavy metal contamination, will be carriers passing on the toxins to those next in the food-chain, in a case of bio-magnification,” says Ramachandran.

K. Palanivelu, director, CCC&DM, says, “In a study about the seasonal variations in the quality of water in the Pallikaranai Marsh, we found heavy metal contamination around the place where the landfill is located. The presence of lead, chromium, nickel and zinc is significantly huge.”

Now, the issue of bio-magnification cuts closer than we may think. People are known to fish in the Perumbakkam wetland, a spit of a wetland that is cut off from the Marsh but is actually a part of it, and signifies a part of its southern section.

Besides the landfill, there is the problem of sewage and grey water making their way into the Pallikaranai Marsh through its various channels.

“Treated or partially treated sewage water is being let into the Pallikaranai Marsh,” says Palanivelu.

Besides, water from many lakes in the surrounding areas flow into the Pallikaranai Marsh before entering the Buckingham Canal via Okkiyam Maduvu. These lakes being polluted on account of the sewage and grey water that are illegally let into them, they carry the problem to Pallikaranai marsh.

In certain parts of the world, a section of wetlands are used as natural filters for grey water, by growing certain plants that can carry out this filtration process efficiently. Can’t such a exercise be carried out at small outlying sections of the Pallikaranai marsh, with the grey water treated in this manner before being allowed to get into the Marsh? “That is possible only if there is an interface between the catchment area and the wetland. Only in the presence of such an interface can the exercise be carried out without the wetland being affected. That is not the case with the Pallikaranai Marsh. There is no question of an interface anymore. The inflow of polluted water is straight, coming from urban sections that swarm around the wetland. So, we have gone well beyond the stage where we could have earmarked small sections of the Pallikaranai Marsh for such an exercise. Now, given the huge sewage pollution, there is a need to have sewage and effluent treatment facilities at all the inlet points, around the Marsh,” says Ramachandran.

There seems to be a lot of work on our hands. And it is also clear that there is no time to waste anymore.

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Printable version | Feb 20, 2020 9:58:04 AM | https://www.thehindu.com/news/cities/chennai/are-chennais-kidneys-packing-up/article30712047.ece

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