Secondary organic aerosols (SOAs) are tiny particles formed in the atmosphere from natural and man-made emissions. These aerosols influence both climate and air quality. Also, their levels have changed dramatically since the Industrial Revolution, making it even crucial to understand their evolution from the preindustrial era to the present day.

A recent study led by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences has shed new light on how human activities have altered the composition of the atmosphere over time, with a particular focus on SOAs.

The study, published in Advances in Atmospheric Sciences, highlighted the need to quantify the differences in SOA levels between the preindustrial period and today to accurately assess the environmental impact of human activities.

Historically, there were two major challenges that hindered accurate SOA simulations.

"One is missing historical data. There is limited information about vegetation cover during the preindustrial period, making it difficult to estimate natural emissions," said Dr. CHEN Xueshun, one of the corresponding authors. "The other is uncertainties in SOA formation. Understanding how SOAs form is complex, and existing models have struggled to capture this process accurately."

To overcome these obstacles, the research team incorporated advanced tools into their models, including the Model of Emissions of Gases and Aerosols from Nature (MEGAN) and the Aerosol and Atmospheric Chemistry Model of the Institute of Atmospheric Physics (IAP-AACM). They also used a dynamic vegetation model to simulate the natural emissions from plants, allowing for a more accurate comparison of SOA levels between the two periods.

The study found that while natural emissions (biogenic SOAs) dominated the preindustrial atmosphere, human-made SOAs have surged since the Industrial Revolution. Today, anthropogenic SOAs contribute up to 53% of total SOA levels, a significant increase from preindustrial times.

"In the preindustrial period, natural sources were the primary contributors to SOA. However, our findings show that human activities have greatly amplified SOA production in the present day, leading to significant changes in global air quality," said CHEN.

Looking ahead, the team plans to delve deeper into the climate impacts of these aerosols. "Our next step is to quantify the climate effects of organic aerosols and explore the interactions between vegetation, air quality, and climate," said Prof. WANG Zifa, another corresponding author of the study. "This will help people better understand the full scope of human impact on the environment."

The significant impact of non-traditional sources and atmospheric oxidation on secondary organic aerosols (SOA) before and after the Industrial Revolution. (Image by IAP)