Abstract
Abstract. The Kathmandu Valley in south Asia is considered as one of the global "hot spots" in terms of urban air pollution. It is facing severe air quality problems as a result of rapid urbanization and land use change, socioeconomic transformation, and high population growth. In this paper, we present the first full year (February 2013–January 2014) analysis of simultaneous measurements of two short-lived climate forcers/pollutants (SLCF/P), i.e., ozone (O3) and equivalent black carbon (hereinafter noted as BC) and aerosol number concentration at Paknajol, in the city center of Kathmandu. The diurnal behavior of equivalent BC and aerosol number concentration indicated that local pollution sources represent the major contributions to air pollution in this city. In addition to photochemistry, the planetary boundary layer (PBL) and wind play important roles in determining O3 variability, as suggested by the analysis of seasonal changes of the diurnal cycles and the correlation with meteorological parameters and aerosol properties. Especially during pre-monsoon, high values of O3 were found during the afternoon/evening. This could be related to mixing and entrainment processes between upper residual layers and the PBL. The high O3 concentrations, in particular during pre-monsoon, appeared well related to the impact of major open vegetation fires occurring at the regional scale. On a synoptic-scale perspective, westerly and regional atmospheric circulations appeared to be especially conducive for the occurrence of the high BC and O3 values. The very high values of SLCF/P, detected during the whole measurement period, indicated persisting adverse air quality conditions, dangerous for the health of over 3 million residents of the Kathmandu Valley, and the environment. Consequently, all of this information may be useful for implementing control measures to mitigate the occurrence of acute pollution levels in the Kathmandu Valley and surrounding area.
Highlights
Air pollution is a major environmental challenge in several regions of the world, defined as “hot spots” (Monks et al, 2009)
The diurnal behavior of equivalent black carbon (BC) and aerosol number concentration indicated that local pollution sources represent the major contributions to air pollution in this city
Over the whole measurement period, T had an average value of 18.7 ± 5.6 ◦C
Summary
Air pollution is a major environmental challenge in several regions of the world, defined as “hot spots” (Monks et al, 2009). The Kathmandu Valley in Nepal, the largest metropolitan region at the Himalayan foothills (one of the most polluted but still least sampled regions of the world), represents one of the regional hot spots in terms of air pollution. This area, having a cross section of about 20 km north to south and 30 km east to west, comprises three administrative districts, Kathmandu, Lalitpur, and Bhaktapur, and has undergone rapid but unplanned urbanization due to high population growth, dramatic land use changes, and socioeconomic transformation, facing severe air pollution problems. An improved scientific understanding of the main sources and impacts of air pollution in the region is a prerequisite for designing effective mitigation options
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
