Long-term monitoring (2015–2019) of atmospheric trace gases (NH3, NO, NO2 and SO2) and aerosols (PM2.5 and PM10) was carried out at Palampur, Himachal Pradesh (HP) over the western Himalayan region of India to explore the influence of trace gases and meteorology on secondary inorganic aerosol (SIA) formation. During the entire monitoring period, the mean concentrations of NH3, NO, NO2 and SO2 were 13.4 ± 8.9 µg m−3, 15.2 ± 12.6 µg m−3, 13.0 ± 9.8 µg m−3 and 7.1 ± 5.1 µg m−3, respectively, whereas the mean concentrations of PM2.5 and PM10 were 19.3 ± 14.5 µg m−3 and 39.4 ± 22.9 µg m−3, respectively. Although the annual mean concentrations of these trace gases and aerosols were well within the National Ambient Air Quality Standards (NAAQS) during 2015–2019, however, the daily mean value of these pollutants (NO, NO2, SO2, PM2.5 and PM10) occasionally breached the NAAQS (prescribed for the ecologically sensitive area as well as rural areas). The concentrations of trace gases and aerosols showed significant diurnal, seasonal and monthly variations during the monitoring period. The mean concentrations of all the trace gases were observed highest in winter (except SO2) whereas the lowest in the monsoon season. The mass concentrations of PM2.5 (23.1 ± 11.2 µg m−3) and PM10 (47.5 ± 13.3 µg m−3) were recorded highest in summer and lowest in monsoon seasons. The mean PM2.5/PM10 ratio during winter, summer and post-monsoon seasons were estimated to be 0.52, 0.49, and 0.52, respectively; indicating almost 50% contribution of fine fraction of aerosol in PM10 (except monsoon season) supporting the influence of secondary formation. The SIA formation through gas-to-particle process over the study site may leads the dense haze formation during winter and colder months. Result reveals the inter-annual variability of trace gases (NH3, NO, NO2 and SO2) and aerosols (PM2.5 and PM10) concentrations over the monitoring site in the western Himalayas. The surface wind analysis with wind direction revealed the local activities/tourism, agricultural activities, vehicular emissions and combustion to be the main sources of trace gases and aerosols over the western Himalayas. The linear positive relationship of NH3 with NO, SO2, and PM2.5 suggests the influence of trace gases in the SIA formation at the study site. The present study on the interaction of ambient trace gases and aerosols over the Himalayas region is a valuable document for the policymakers for further mitigation and reduction in pollutants loading to improve the air quality of the Himalayan region.

Long-Term Relationship of Atmospheric Trace Gases, Aerosols and Meteorology Over the Western Himalayan Region of India

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发表日期：

2026年3月25日

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Manisha,
Ashish Ranjan,
Shankar G. Aggarwal,
Sachchidanand Singh,
Sanjay K. Uniyal,
Vijender Kumar Bambal,
Sudhir Kumar Sharma

摘要

Long-term monitoring (2015–2019) of atmospheric trace gases (NH₃, NO, NO₂ and SO₂) and aerosols (PM_2.5 and PM₁₀) was carried out at Palampur, Himachal Pradesh (HP) over the western Himalayan region of India to explore the influence of trace gases and meteorology on secondary inorganic aerosol (SIA) formation. During the entire monitoring period, the mean concentrations of NH₃, NO, NO₂ and SO₂ were 13.4 ± 8.9 µg m⁻³, 15.2 ± 12.6 µg m⁻³, 13.0 ± 9.8 µg m⁻³ and 7.1 ± 5.1 µg m⁻³, respectively, whereas the mean concentrations of PM_2.5 and PM₁₀ were 19.3 ± 14.5 µg m⁻³ and 39.4 ± 22.9 µg m⁻³, respectively. Although the annual mean concentrations of these trace gases and aerosols were well within the National Ambient Air Quality Standards (NAAQS) during 2015–2019, however, the daily mean value of these pollutants (NO, NO₂, SO₂, PM_2.5 and PM₁₀) occasionally breached the NAAQS (prescribed for the ecologically sensitive area as well as rural areas). The concentrations of trace gases and aerosols showed significant diurnal, seasonal and monthly variations during the monitoring period. The mean concentrations of all the trace gases were observed highest in winter (except SO₂) whereas the lowest in the monsoon season. The mass concentrations of PM_2.5 (23.1 ± 11.2 µg m⁻³) and PM₁₀ (47.5 ± 13.3 µg m⁻³) were recorded highest in summer and lowest in monsoon seasons. The mean PM_2.5/PM₁₀ ratio during winter, summer and post-monsoon seasons were estimated to be 0.52, 0.49, and 0.52, respectively; indicating almost 50% contribution of fine fraction of aerosol in PM₁₀ (except monsoon season) supporting the influence of secondary formation. The SIA formation through gas-to-particle process over the study site may leads the dense haze formation during winter and colder months. Result reveals the inter-annual variability of trace gases (NH₃, NO, NO₂ and SO₂) and aerosols (PM_2.5 and PM₁₀) concentrations over the monitoring site in the western Himalayas. The surface wind analysis with wind direction revealed the local activities/tourism, agricultural activities, vehicular emissions and combustion to be the main sources of trace gases and aerosols over the western Himalayas. The linear positive relationship of NH₃ with NO, SO₂, and PM_2.5 suggests the influence of trace gases in the SIA formation at the study site. The present study on the interaction of ambient trace gases and aerosols over the Himalayas region is a valuable document for the policymakers for further mitigation and reduction in pollutants loading to improve the air quality of the Himalayan region.