Kathmandu’s air quality competes with the worst polluted cities in the world. Pollutants recorded in the city, especially during the winter, are way above levels recommended by the World Health Organization.
While the devastating effects of air pollution on human health has been documented in detail, its impact on cultural monuments in the ancient city has not been studied much. But a recent study has pointed out that air pollution is affecting historical monuments in Kathmandu, especially the gilded structures the city was once famous for.
The recent study, conducted by a team of Indian scientists, shows that the golden windows of the historic Patan Palace are being corroded, thanks to air pollution.
During the research, seven windows from around the palace were sampled. According to the researchers, particles such as elemental carbon, sulphur dioxide, chlorine and organic matter were found in the sample. The compositional analysis of the gilded windows was then studied using a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). “The dirty windows were first to be scanned in the device which showed evidence of carbonaceous compounds and the poor layer of the gold layer on top of the copper windows,” say the researchers.
They found that the windows had cracks and some even had parts clipped off. Researchers believe that those could have been developed due to exposure to various atmospheric conditions in Kathmandu. They also argue that it might have been due to the reaction between chloride and sulphate ions present in the environment as pollutants. The two ions are known to corrode gilded structures. The study points out that gilded structures corrode when sulphur dioxide and nitrogen oxide (found in vehicular emissions) get dissolved in the rain or get mixed with fog or mist. The gases then form acids such as sulphuric acid and nitric acid to attack the metals.
The study comes at a time when conservationists were already saying that pollution is taking a toll on cultural monuments in the city, and it’s not just the metals they are worried about. “Upon inspection of the ancient structures, one can notice that the dust and smoke have deteriorated wooden structures and have blackened the exteriors of gilded structures,” adds Rohit Ranjitkar from Kathmandu Valley Preservation Trust.
The study shows that there are more reasons for the government to take action against pollution. The health benefits of reduced pollution have already been discussed a lot. But controlling pollution will have long-lasting impacts on the country’s treasured cultural monuments as well.