A comprehensive study of variability in total column of ammonia using quantile regression approach over non-attainment cities of the North-Western Himalayas

The present study has investigated the relationship between total column ammonia (TCNH₃) and different environmental factors in the non-attainment regions viz., Damtal, Baddi and Paonta Sahib in the North-Western Himalayas. The 12 years satellite data was obtained from the Infrared Atmospheric Sounding Interferometer (IASI) and the quantile regression (QR) tool was used to study the variability in long-term trends of TCNH₃ across its distribution. The maximum concentration of TCNH₃ was observed during July in Paonta Sahib followed by Baddi and Damtal. Simultaneously, august month shows notable decrease in TCNH₃ levels, while winter season again shows opposite trend in Paonta Sahib. Further, a significant positive correlation is observed between TCNH₃ and key environmental variables such as PM_2.5, temperature, total column water vapour (TCWV), and rainfall. Similarly, an increasing trend was also highlighted in higher quantile (τ>0.8) across all cities, while, negative trend was observed (τ<0.8) in Damtal and Paonta Sahib. Additionally, PM_2.5 levels displayed substantial positive trends in significantly higher quantiles (τ>0.95), while rainfall showed significant variability with notable negative trends in higher quantiles (τ>0.9). Overall, the present study enhanced the understanding of TCNH₃ variability across the three non-attainment cities of Himachal Pradesh, emphasizing the need for continued monitoring and targeted environmental management strategies to mitigate the impact of industrial emissions on air quality and public health.