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Spatial and Temporal Variations of Gaseous and Particulate Pollutants in Six Sites in Tibet, China, during 2016–2017

Category: Urban Air Quality

Volume: 19 | Issue: 3 | Pages: 516-527
DOI: 10.4209/aaqr.2018.10.0360
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Pengfei Chen1, Shichang Kang 1,2, Junhua Yang1, Tao Pu1, Chaoliu Li2,3, Junming Guo1, Lekhendra Tripathee1

  • 1 State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou 730000, China
  • 2 CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100085, China
  • 3 Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, CAS, Beijing 100101, China

Highlights

Air pollution characteristics were analyzed in six cities of Tibetan Plateau.
Air pollutants are more prevalent in Lhasa and Nagchu than in other sites in Tibet.
All pollutants except O3 have higher concentrations in winter than those in summer.
Diurnal PM2.5, PM10, SO2, NO2, and CO values showed two peaks around noon and midnight.


Abstract

Long-term air quality data with high temporal and spatial resolutions are necessary to understand some processes influencing air quality and corresponding environmental and health effects. In this study, spatiotemporal variations of PM2.5, PM10, SO2, NO2, CO, and O3 were investigated over a one-year period (June 2016–May 2017) at six sites of the Tibetan Plateau (TP). The annual mean concentrations of PM2.5 in all cities except Nagchu were below the Grade II standard (35 µg m–3), and the values in Nagri and Nyingchi were even less than the Grade I standard (15 µg m–3). PM10 concentrations showed similar distribution pattern with PM2.5. Evident seasonal variations of PM2.5, PM10, SO2, NO2, and CO concentrations were observed, with the highest seasonal average value being in winter followed by fall, spring, and summer, in descending order. By contrast, the 8-h O3 concentration showed an opposite seasonal variation because the O3 depended on lots of factors such as stratospheric incursions, weather conditions, and intensity of solar radiation. The diurnal trends of PM2.5, PM10, SO2, NO2, and CO concentrations in study region generally showed a flat “W” shape with two peaks occurring around noon (10:00–12:00) and midnight (21:00–23:00); these peaks were found to be affected by emission sources and weather conditions. However, the O3 concentration trends did not significantly differ among the six regions, with the maximum concentration being in the afternoon. In sum, cities on the TP showed slightly higher pollution levels in regions affected by anthropogenic activities such as Lhasa and Nagchu, whereas other cities showed good air quality. Beside long-range transport pollutants from surrounding regions, local emissions (e.g., biomass burning, religious activities) also contributed much to the atmospheric pollutants. This study provides a basis for the formulation of future urban air pollution control measures on the TP.

Keywords

PM2.5 Ozone Air pollution Distribution Tibetan Plateau


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