Evaluation of aircraft emission at Tribhuvan international airport and its contribution to air quality in Kathmandu, Nepal

The recent rise in the number of aircraft flights and the subsequent increase in emissions has raised concerns worldwide, and this increasing trend is expected to continue. This research provides an overall estimation of the landing and take-off cycle (LTO) emissions from Tribhuvan International Airport (TIA) as well as the associated contribution of these emissions to ambient air quality in Kathmandu valley. The aircraft emissions of nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbon (HC), sulfur dioxide (SO2), volatile organic compounds (VOCs), particulate matter (PM10, and PM2.5), and black carbon (BC) during the LTO are estimated for recent 20 years by using the emission factor method. The corresponding contribution to ambient air quality was simulated using AERMOD and Weather Research and Forecasting (WRF) models. The research reveals that total LTO emissions by aircraft at TIA range from 898 to 2123 tonnes per year (2000–2019). The average LTO emissions of NOx, CO, HC, VOC, SO2, PM10, PM2.5, and BC were around 14512, 8142, 2387, 1737, 1247, 481, 472, and 231 tonnes respectively during the period of 20 years. The highest aircraft emission was shown in taxi/idle mode for the LTO cycle, with major constituents being HC and CO. The LTO emissions and their effect on air quality have continually increased. The highest contribution of the LTO emissions on air quality was found in the pre-monsoon season. The dominant pollutants in TIA were nitrogen oxides and its average 24-h concentration was 158.1 μg/m3, which exceeded the National Ambient Air Quality Standard (NAAQS) limit value. Hence, LTO emission significantly contributed to ambient air quality in Kathmandu city

Numerical Evaluation of the Impact of Urbanization on Summertime Precipitation in Osaka, Japan

This study utilized the Weather Research and Forecasting (WRF) model version 3.5.1 to evaluate the impact of urbanization on summertime precipitation in Osaka, Japan. The evaluation was conducted by comparing the WRF simulations with the present land use and no-urban land use (replacing “Urban” with “Paddy”) for August from 2006 to 2010. The urbanization increased mean air temperature by 2.1°C in urban areas because of increased sensible heat flux and decreased mean humidity by 0.8 g kg−1 because of decreased latent heat flux. In addition, the urbanization increased duration of the southwesterly sea breeze. The urbanization increased precipitation in urban areas and decreased in the surrounding areas. The mean precipitation in urban areas was increased by 20 mm month−1 (27% of the total amount without the synoptic-scale precipitation). The precipitation increase was generally due to the enhancement of the formation and development of convective clouds by the increase in sensible heat flux during afternoon and evening time periods. The urbanization in Osaka changes spatial and temporal distribution patterns of precipitation and evaporation, and consequently it substantially affects the water cycle in and around the urban areas of Osaka

A Comparative Study of Stack Emissions from Straight-Line and Zigzag Brick Kilns in Nepal

Nepal has approximately 1000 operational brick kilns, which contribute significantly to ambient air pollution. They also account for 1.81% of the total bricks produced in the South Asian region. Little is known about their emissions, which are consequently not represented in regional/global emission inventories. This study compared emissions from seven brick kilns. Four were Fixed Chimney Bull’s Trench Kilns (FCBTKs) and three were Induced-Draught Zigzag Kilns (IDZKs). The concentrations of carbon dioxide (CO2), sulfur dioxide (SO2), black carbon (BC), and particulate matter (PM) with a diameter less than 2.5 µm (PM2.5) were measured. The respective emission factors (EFs) were estimated using the carbon mass balance method. The average fuel-based EF for CO2, SO2, PM2.5, and BC were estimated as 1633 ± 134, 22 ± 22, 3.8 ± 2.6 and 0.6 ± 0.2 g per kg, respectively, for all FCBTKs. Those for IDZKs were 1981 ± 232, 24 ± 22, 3.1 ± 1, and 0.4 ± 0.2 g per kg, respectively. Overall, the study found that converting the technology from straight-line kilns to zigzag kilns can reduce PM2.5 emissions by ~20% and BC emissions by ~30%, based on emission factor estimates of per kilogram of fuel. While considering per kilogram of fired brick, emission reductions were approximately 40% for PM2.5 and 55% for BC, but this definitely depends on proper stacking and firing procedures