Seasonal Variations of Aerosols in Pakistan: Contributions of Domestic Anthropogenic Emissions and Transboundary Transport

10.4209/aaqr.2014.12.0332

Muhammad Zeeshaan Shahid；Hong Liao；Jian-Ping Li；Imran Shahid；Arifa Lodhi；Muhammad Mansha

WRF-Chem ； Aerosols in Pakistan ； Seasonal variations

Aerosol and Air Quality Research

15卷4期（2015 / 08 / 01）

1580 - 1600

英文

Air pollution has become a serious challenge for developing countries like Pakistan. Very scarce information is available regarding pollution levels in this geographic region. This study presents the first modelling work to simulate the spatial distribution and temporal variation of aerosol concentrations over Pakistan by using the Weather Research and Forecasting Model coupled with chemistry (WRF-Chem). Simulated aerosols species include sulfate, nitrate, ammonium, organic carbon, black carbon, and PM_(2.5) (particles with a diameter of 2.5μm or less), which are evaluated against groundbased observations and satellite measurements. In year 2006, simulated PM_(2.5) concentrations averaged over northeastern Pakistan (71-74.5°E, 28-34°N) are 55, 48.5, 31.5, and 98μg/m^3 in January, April, July, and October, respectively. The simulated highest PM_(2.5) concentration in October results from the relatively low temperatures that favor nitrate formation as well as the lowest precipitation that leads to the smallest wet deposition of all aerosol species. The simulated lowest concentration of PM_(2.5) in July can be attributed to the largest precipitation associated with the South Asian summer monsoon. Sensitivity studies show that transboundary transport contributes to PM_(2.5) aerosol levels in northeastern Pakistan by 10-20% in January and April and by 10-40% in July and October of year 2006. Wind over India and Pakistan is found to be the major meteorological parameter that determines the transboundary aerosol transport.