Assessment of ambient air quality in Bishnumati corridor, Kathmandu metropolis
The Kathmandu valley urban area is growing as a metropolis. Bishnumati corridor in Kathmandu valley is is a target of increased pollution. The unabated solid waste land-filling on either side of the river-bank and animal slaughter houses and biological waste arising from these activities, busy commercial and high residential density characterize the corridor. Six areas, namely Teku Dovan, Kalimati Bridge, Kankeswori, Shova Bhagwati, Balaju and New Bus Park areas, all areas falling within the Bishnumati corridor were selected to measure air quality representing corridor. The pollutants quantified were respirable particulate matter – PM10, sulphur dioxide and oxides of nitrogen. The air-borne microbial flora and fungi load quantification were also carried out. Teku Dovan (918.92 µg/m3) and Shovabhagavati areas (847.45 µg/m3) showed higher levels of particulates. Kankeswori area showed highest levels of aerial bacterial (3.7x107 cfu/m3) and fungal load (4.8x108 cfu/m3). The PM10 levels at all the sites are substantial and fall in the categories of ‘Harmful’ and ‘Hazardous’ quality of air suggesting that the corridor needing intervention to minimize the risk from air pollution. Non-judicious open-air combustion of the solid waste contributes to air pollution. Heavy traffic and few roads not clad with asphalt; perceivable mal-odor and persistent stench emanating from the indiscriminate disposal and consequent putrefaction processes, dense population and increased commercial activities are other principal contributing sources to the resulting pollution of the corridor. In view of this status, mitigating measures to minimize exposure to the toxicants in the corridor is a necessity.