Contrasting optical properties of fine particulate matter in Seoul and Mexico City highlight climate impacts

Severe fine mud air pollution over Seoul and Mexico City, being composed of the identical sort of fine particulate matter (PM_2.5), reveals markedly completely different traits. Seoul’s air tends to mirror daylight, contributing to a cooling impact on Earth, whereas Mexico City’s particles are extra inclined to soak up daylight, probably accelerating world warming.

A analysis workforce led by Professor Sang Seo Park from the Department of Civil, Urban, Earth and Environmental Engineering at UNIST analyzed chemical samples and optical knowledge of PM_2.5 collected from 14 cities around the globe.

Their findings, published in the journal Environmental Science & Technology, reveal notable variations in the optical and chemical traits of fine particles in these two city environments.

According to the research, Seoul’s fine particulate matter has a excessive proportion of sulfate and nitrate compounds, which are likely to strongly scatter daylight, exhibiting a reflective (albedo) nature.

In distinction, Mexico City has a comparatively greater presence of black carbon—soot—that absorbs daylight, displaying an absorptive property. This implies that, even with the identical PM_2.5 ranges, Seoul’s particles mirror daylight again into house, exerting a cooling affect, whereas particles in Mexico City soak up photo voltaic vitality, probably accelerating native warming.

The analysis in contrast chemical composition knowledge (SPARTAN) and optical measurements (AERONET)—a ground-based community that assesses how daylight is scattered and absorbed because it passes by the ambiance—from 14 cities worldwide, together with Seoul, Beijing, and Mexico City. AERONET knowledge allows estimation of particulate matter focus primarily based on how a lot sunlight is dimmed and scattered by atmospheric aerosols.

Results indicated {that a} greater ratio of scattering elements, corresponding to sulfate and nitrate, correlates with elevated Single Scattering Albedo (SSA) values.

SSA quantifies the proportion of gentle mirrored versus absorbed by airborne particles; values approaching 1 signify predominantly scattering particles, whereas decrease values point out greater absorption.

The research discovered that because the quantity of absorbing elements like black carbon elevated, SSA decreased, particularly at longer wavelengths (870–1,020 nm). Additionally, bigger quantities of soil mud led to fast modifications in wavelength-dependent scattering properties (dSSA and rSSA).

Sujin Eom, the primary creator of the research, defined, “This research demonstrates, through direct measurements rather than modeling, how differences in chemical composition influence the optical behavior and climate effects of aerosols. It highlights the importance of considering not just PM_2.5 concentrations but also their composition in air quality and climate studies.”

Professor Park added, “Our findings establish a basis for indirectly estimating the toxicity differences of fine particles based on their optical properties. This approach can enhance the accuracy of air quality forecasts and inform public health policies.”

This joint analysis was carried out in collaboration with the UNIST Particle Pollution Research and Management Center.