Influence of Seasonal Emissions, Regional Transport, and Particle Morphology on PM2.5-Bound Elements in Rural Northern India

Rural environments play a critical role in shaping regional air quality and atmospheric chemistry due to their distinct emission sources, seasonal activities, and meteorological conditions. This study investigates the seasonal variability of PM_2.5 mass concentrations and their associated major and trace elements in a rural region of Uttar Pradesh, India, based on day- and nighttime sampling conducted from July 2023 to May 2024. A total of 135 samples were collected and analysed for elemental composition. In total, 31 elements (Li, B, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Zr, Mo, Ag, Cd, Sn, Sb, Ba, Pb, Bi) were quantified using ICP–MS.

Seasonal analysis revealed that nighttime PM2.5 levels were consistently higher than daytime concentrations (1.3–1.5 times higher), with the highest mass loadings observed during the post-monsoon season, followed by the winter, pre-monsoon, and monsoon seasons. In contrast, elemental concentrations peaked in winter despite lower PM_2.5 mass relative to the post-monsoon period, indicating stronger influences from combustion and industrial emissions along with reduced atmospheric dispersion. Enrichment factor (EF) analysis revealed a strong enrichment of anthropogenic elements (K, Cu, Zn, Pb, Sb, Bi), while crustal elements (Ca, Al, Fe, Mg, Ti) exhibited low EF values, confirming a significant contribution from soil and resuspended dust. FTIR analysis further revealed seasonal shifts in functional groups, with higher contributions of organic and carbonyl species in winter and post-monsoon periods.

Principal Component Analysis (PCA) identified major source categories—including biomass burning, industrial emissions, and traffic-related sources in agreement with EF-derived source signatures. HYSPLIT back-trajectory analysis further demonstrated the influence of regional long-range transport on seasonal aerosol composition. SEM–EDX morphological analysis also revealed clear seasonal differences in particle size and structure, with substantially higher particle loading during the winter and post-monsoon seasons.

Health risk assessment indicated substantially elevated risks during winter, with carcinogenic risk increasing by ~1.8-fold relative to post-monsoon and ~2.3-fold relative to monsoon, and non-carcinogenic hazards rising by 0.5–7.6-fold across seasons. Elements such as Pb, Cr, V, and Mn were the dominant contributors to both carcinogenic and non-carcinogenic risks.

Overall, the findings highlight the significant influence of seasonal emission patterns, combustion activities, and atmospheric dynamics on shaping the composition of rural aerosols and their associated health impacts.

 

Keywords: Particulate matter; Elements Analysis: Principal component analysis; Enrichment factor; Health risk assessment.