How Will Air Quality Change in South Asia by 2050?

Over last two decades, South Asia has witnessed a rapid increase in population, industrialization, and energy demands. Consequently, 2-6 fold increase in the emission of particulate matter (PM) and trace gases were reported. Air pollution in South Asia has more adverse impact and is linked to nearly 1 million premature deaths and around 10 million tonnes of crop loss in a year. So, monitoring of trace gases and PM concentrations over urban centers has received significant attention among scientists, policymakers, health regulatory agencies, and the media. Particularly over the Indian region, this becomes significant, as the observation of trace gases and PM concentrations with fairly good temporal and spatial resolutions is limited. Concerns about air quality and transport pathways on a regional scale also place more stringent demand on observations and modeling effort. Quantifying the source contribution (regional emission due to various anthropogenic activities such as city traffic density vs. long-range transport due to meteorological influence) of trace gases and PM over different temporal and spatial scales has been receiving significant attention. In view of this, measurement of trace gases and PM in concurrence with meteorological variables (wind speed and direction) is of paramount importance.&#160;In this study, we have presented three-year surface measurements of TGs (O3, CO, NOx, SO2 and NH3) and PMs (PM2.5 and PM10) at three coastal and urban sites, namely, Trivandrum (TVM, 8.5&#176;N, 76.9&#176;E, 5m AMSL), Chennai (CHN, 13.7&#176;N, 80.2&#176;E, 6.7m AMSL) and Bhubaneswar (BHB, 20.2&#176;N, 85.8&#176;E, 45m AMSL) located in India. -In addition to that Ozone Monitoring Instrument OMI&#8217;s, surface mass concentration data for SO2 and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts data were also used to identify potential sources. The principal component analysis (PCA) and concentrated weighted trajectories (CWT) were applied to the dataset. The TGs and PM showed high values during winter and lower values in a monsoon at these sites. Both TGs and PM values were higher at BHB compared to those at TVM and CHN.&#160; Surface O3 at BHB was about 3 times higher than that at TVM and 2.2 times higher than that at CHN.&#160; Interestingly, PCA suggests that the major concentrations of O3, PM10, and SO2 at TVM and CHN were transported from different locations and not produced locally except for pre-monsoon at CHN, which was of local origin.&#160; CWT analysis and OMI&#8217;s surface mass concentration data also suggest that the air quality at TVM could be influenced by heavy emissions transported from the Indo-Gangetic plain. The Merra-2 reanalysis well captured seasonal variations of TGs and PMs; and it overestimated surface O3, by a factor of about 2 to the measurement at the study sites.&#160;&#160;&#160;

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COVID-19 pandemic lockdown: effects on the air quality of South Asia

Environmental Sustainability ◽

10.1007/s42398-020-00154-6 ◽

2021 ◽

Author(s):

Ritu Kandari ◽

Ashwani Kumar

Keyword(s):

Air Quality ◽

South Asia

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High-resolution modeling the distribution of surface air pollutants and their intercontinental transport by a global tropospheric atmospheric chemistry source-receptor model (GNAQPMS-SM)

10.5194/gmd-2021-201 ◽

2021 ◽

Author(s):

Qian Ye ◽

Jie Li ◽

Xueshun Chen ◽

Huansheng Chen ◽

Wenyi Yang ◽

...

Keyword(s):

Air Quality ◽

High Resolution ◽

North America ◽

East Asia ◽

South Asia ◽

North Pacific ◽

Receptor Model ◽

The North ◽

Intercontinental Transport ◽

The North Pacific

Abstract. Many efforts have been devoted to quantifying the impact of intercontinental transport on global air quality by using global chemical transport models with horizontal resolutions of hundreds of kilometers in recent decades. In this study, a global online air quality source-receptor model (GNAQPMS-SM) is designed to effectively compute the contributions of various regions to ambient pollutant concentrations. The newly developed model is able to quantify source-receptor (S-R) relationships in one simulation without introducing errors by nonlinear chemistry, which largely reduces the computation costs compared to the brute force method. We calculate the surface and planetary boundary layer (PBL) S-R relationships in 19 regions over the whole globe for ozone, black carbon (BC) and non-sea-salt sulphate (nss-sulphate) by conducting a high-resolution (0.5° × 0.5°) simulation for the year 2018. The model exhibits a realistic capacity in reproducing the spatial distributions and seasonal variations of tropospheric ozone, carbon monoxide, and aerosols at global and regional scales (Europe, North America and East Asia). The correlation coefficient (R) and normalized mean bias (NMB) for seasonal ozone at global background and urban-rural sites ranged from 0.49 to 0.87 and −2 % to 14.97 %, respectively. For aerosols, the R and NMB in Europe, North America and East Asia mostly exceed 0.6 and are within ±15 %. These statistical parameters based on this global simulation can match those of regional models in key regions. The simulated tropospheric nitrogen dioxide and aerosol optical depths are generally in agreement with satellite observations. The model overestimates ozone mixing ratios in the upper troposphere and stratosphere in the tropics, mid-latitude and polar regions of the Southern Hemisphere due to the use of a simplified stratospheric ozone scheme and/or biases in estimated stratosphere-troposphere exchange dynamics. We find that O3 in the surface layer can travel a long distance and contributes a nonnegligible fraction to downwind regions. Nonlocal source transport explains approximately 35–60 % of surface O3 in East Asia, South Asia, Europe and North America. The O3 exported from Europe can also be transported across the Arctic Ocean to the North Pacific and contributes nearly 5–7.5 % to the North Pacific. BC, as a primary aerosol, is directly linked to local emissions, and each BC source region mainly contributes to itself and surrounding regions. For nss-sulphate, contributions of long-range transport account for 15–30 % within the PBL in East Asia, South Asia, Europe and North America. Our estimated international transport is lower than that from the Hemispheric Transport of Air Pollution (HTAP) assessment report in 2010. In this study, local contributions to surface nss-sulphate and BC exceed the ranges given in the HTAP model, while local contributions to nss-sulphate and BC within the PBL are mainly within the ranges. This difference may be related to the different simulation years, emission inventories, horizontal resolutions and S-R revealing methods. The S-R relationship of aerosols within the East Asia subcontinent is also assessed. The model that we developed creates a link between the scientific community and policymakers. Finally, the results are discussed in the context of future model development and analysis opportunities.

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