Understanding PM-bound trace element solubilities: Controls, anthropogenic and natural sources

Area of Science:

• Environmental Science
• Analytical Chemistry
• Atmospheric Chemistry

Background:

• Urbanization and industrialization increase heavy metal pollution in fine particulate matter (PM2.5).
• Understanding the chemical characteristics and sources of PM2.5-bound trace elements (TEs) is crucial for environmental and health risk assessment.

Purpose of the Study:

• To investigate the chemical fractions and sources of key TEs in PM2.5.
• To analyze the impact of COVID-19 lockdowns on TE mobility and bioavailability.

Main Methods:

• A two-year (2019-2020) study analyzed key TEs (Al, Si, Ca, Fe, Ti, K, S, P, Mn, Ni, V, Cr, Cu, Zn, Pb) in PM2.5.
• A four-step sequential extraction method and inductively coupled plasma optical emission spectrometry were used for TE analysis.
• Positive Matrix Factorization (PMF) was applied to identify TE sources.

Main Results:

• The PMF model identified five main sources of TEs in PM2.5: mineral dust, agricultural crop burning, vehicular emissions, coal combustion, and industrial emissions.
• TE mobility from geogenic sources increased in 2020, likely due to secondary inorganic species formation.
• Mobility of TEs from anthropogenic sources decreased during the 2020 COVID-19 lockdowns.

Conclusions:

• Anthropogenic activities significantly influence the abundance, solubility, and bioavailability of TEs in PM2.5.
• Environmental policies and lockdowns can alter the behavior and impact of PM2.5-bound TEs.
• Further research is needed to fully understand the long-term implications of these findings on ecosystem and human health.