School of Earth and Atmospheric Sciences Professor Yuhang Wang and his team studied the factors affecting SO₂ and sulfate concentrations during winter and summer in the “Rust Belt” — from New York through the Midwest — and the Southeast regions of the U.S. over two decades (2004 to 2023). Supported by the National Science Foundation and Georgia Tech’s Brook Byers Institute for Sustainable Systems, the team also developed an ensemble machine learning approach to project seasonal patterns until 2050. 

“Power plants, particularly those burning coal and oil, are a major source of SO₂ emissions in these regions,” says Wang, who co-authored, with Ph.D. students Fanghe Zhao and Shengjun Xi, the study recently published in Environmental Science & Technology Letters. 

Seasonal differences in atmospheric chemistry 

In the U.S., the chemistry in the atmosphere varies among the seasons. During summer, solar radiation from ample sunlight activates oxidant reactions that produce hydrogen peroxide (H₂O₂) in the atmosphere. The supply of H₂O₂ is determined by the amount of emitted air pollution, and once in the atmosphere, H₂O₂ can oxidize SO₂ quickly into sulfate aerosols in the aqueous phase. 

Sulfate aerosols from the oxidation of SO₂ contribute to the formation of particulate matter less than 2.5 micrometers in diameter (PM2.5). Particulate sulfate poses significant environmental and public health risks, including air pollution, acid rain, and circulatory and respiratory issues. 

“The supply of H₂O₂ in summer is eight times greater than in winter — a huge difference — which means sulfate concentrations are generally higher in summer and a reduction in SO₂ emissions leads to a proportional decrease in sulfate concentrations,” explains Wang. “When SO₂ emissions exceed the available supply of H₂O₂ in winter, the reduction in sulfate concentrations can be much smaller because of a ‘chemical damping’ effect that causes sulfate levels to decline more slowly than SO₂ emissions.” 

Narrowing the disparities between seasonal sulfate levels 

The study’s two-decade observations revealed distinct patterns in the reduction of SO₂ emissions and sulfate concentrations during winter and summer. 

While SO₂ emissions significantly decreased in both seasons­ over time — primarily from the Clean Air Act and more power plants transitioning from coal to natural gas — the reduction of sulfate concentrations initially showed large seasonal differences. However, over the past decade, the disparity between winter and summer sulfate levels narrowed as SO₂ emissions decreased.

According to Wang, the seasonal disparity of sulfate was caused by changing chemical regimes in winter over time. Although the lower supply of H₂O₂ remained stable in winter, SO₂ wintertime emissions were higher from 2004 to 2013, then dropped below the level of H₂O₂ after 2013 — reaching parity with the levels of reduced SO₂ emissions in the summer. 

“When you have this complexity of atmospheric chemistry, there is a non-linear effect in winter — as SO₂ emissions decreased, sulfate aerosol production efficiency increased until 2013, then flattened as of today. The reduction in sulfate aerosols initially lagged behind the decrease in SO₂ emissions but eventually caught up as a result of sustained air quality control efforts,” says Wang. “Conversely, there is a simple, linear effect in summer — the more SO₂ emissions, the more sulfate aerosols in the atmosphere — and if you reduce one, the other is reduced by the same proportion.”

Decades-long full impact 

From now until 2050, the researchers’ machine learning projections indicate a continuing decrease of winter and summer sulfate levels, which are currently around 20 percent, as SO₂ emission controls achieve comparable efficacy across the seasons. 

“We’re now seeing the full impact from the Clean Air Act,” concludes Wang, “and the nation’s sustained effort in pollution reduction is key to improving air quality and health outcomes.”

Beginning July 1, Techwood Drive will be fully closed to vehicular traffic between Bobby Dodd Way and North Avenue to support utility work associated with the renovation of the Smith and Howell residence halls. The sidewalk next to Bobby Dodd Stadium at Hyundai Field will be closed to pedestrians. The eastern sidewalk, in front of the residence halls, will be open on either side of the project entrance.  

The latest rankings build on a record year for Georgia Tech commercialization. In 2025, the Institute reported advancing hundreds of technologies toward the marketplace, while achieving record levels of invention disclosures, issued patents, and licensed technologies. Those milestones underscore Georgia Tech’s expanding role in transforming research discoveries into products, companies, and partnerships that create economic and societal value.

“The strong performance reflects a commercialization strategy focused not only on protecting IP, but also on helping researchers translate discoveries into practical applications,” said Raghupathy “Siva” Sivakumar, chief commercialization officer at Georgia Tech. “Whether through licensing technologies, launching startups, or partnering with industry, we are building pathways that help researchers transform discoveries into real-world solutions.” 

From advanced health technologies to environmental monitoring tools and next-generation aerospace ventures, Georgia Tech innovations are reaching users and markets in increasingly diverse ways. One example is Kinemo, a startup developed through Georgia Tech research that is helping people with limited mobility regain independence through wearable assistive technology. Founded by researchers from the College of Engineering, Kinemo uses physiological sensing and small intentional movements to enable users to control digital devices. The company works closely with clinicians and patients at Shepherd Center to refine the technology and expand accessibility for individuals living with spinal cord injuries and mobility limitations.

Another example is Skopii, a startup launched from research in the lab of environmental engineering professor Ameet Pinto. The company is commercializing portable imaging and artificial intelligence technology that enables users to rapidly analyze microorganisms in water and environmental systems, eliminating the need for lengthy laboratory testing. The technology has the potential to improve decision-making for water utilities, food production systems, and environmental monitoring efforts.

As research institutions face increasing pressure to demonstrate impact beyond publications and laboratory discoveries, Georgia Tech continues to show how world-class research can translate into technologies, startups, jobs, and solutions that improve lives. The latest AUTM rankings provide another measure of that success, highlighting an innovation ecosystem that consistently moves ideas from the lab to the marketplace.

Startups such as Kinemo and Skopii illustrate the broader commercialization approach reflected in Georgia Tech's AUTM rankings. 

The University System of Georgia’s (USG) Unified Enterprise Resource Planning (ERP) Program team continues to make steady progress through the Architect and Configure phase, which will continue through the calendar year.