Research

Iron is food for oceanic phytoplankton. This research estimated how much iron humans emit via combustion and how much it reaches the ocean's iron-sensitive parts!

2024 Constraining iron emissions: Used models and observations to obtain the best estimates of anthropogenic iron emissions. Observations compiled from all 6 continents and this work has 35 co-authors!

2022 Atmospheric radiative and oceanic biological responses to anthropogenic combustion iron emissions: Used a mineralogy-based iron representation to estimate how humans affect the radiative budget (DRP) and oceanic phytoplankton growth (NPP) via iron emissions. 

2020 Emission inventory development: Anthropogenic iron emissions' magnitude and solubility highly depend on source representation and mineralogy assumptions. Used findings from metallurgy and chemical transformations to build an iron mineralogy model.

Phosphorus is another biogeochemically important chemical and along with oceanic parts, many regions of the land are also phosphorus-limited.

2025 Phosphorus emissions from fertilizer production: This in-review work estimated global particulate phosphorus emissions from phosphatic fertilizer production, a source no one thought of before! We found that this source can rival global dust and biogenic aerosol particle phosphorus emissions! Stay tuned!

Anthropogenic emissions also rival natural sources for molybdenum and manganese emissions!

2021 Molybdenum emissions and their impact on soils: Michelle Wong (now at Yale) led this work and I contributed to the anthropogenic inventory. "We estimated global emissions of atmospheric Mo in aerosols (<10 μm in diameter) to be 23 Gg Mo yr−1, with 40%–75% from anthropogenic sources."

2024 Manganese emissions: Louis Lu at Cornell led this work and I contributed to the anthropogenic inventory. "We estimated global emissions of atmospheric Mn in aerosols (<10 μm in aerodynamic diameter) to be 1,400 Gg Mn year−1. Approximately 31% of the emissions come from anthropogenic sources. "

Energy transition globally can have local, inequitable impacts. I looked at the air pollution impacts of a global energy transition in the metals and ammonia industries.

2022 Metals for renewables: This research estimated the amount of mining and smelting required to achieve climate goals and the potential air-quality impacts due to those activities! Work done as a Young Scientists Summer Program at IIASA, Austria!

2023 Ammonia for shipping: Using ammonia for shipping can cut reliance on fossil fuels and thus help reduce greenhouse gas emissions. But ammonia leaks can form secondary aerosols in the air and cause air-quality issues in ports where the ships refuel!

The U.S. natural gas distribution system is largely undersampled to be confident in its emission estimates. 

2025 Uncertain methane emissions: This in-prep work examines the uncertainty in emission estimates due to undersampling in the emission factors in the U.S. natural gas distribution system. For example, methane emission from 90 million households that use natural gas are estimated from emission factors obtained from a sample of 75 homes in California!

How can we control the amount of greenhouse gases in the atmosphere?

2024 CDR scale-up pathways: We examined if current carbon dioxide removal technologies can scale-up fast enough and in time to meet climate goals. Work led by Morgan Edwards and Zach Thomas in the La Follette School of Public Affairs at UW-Madison.

2024 Atmospheric methane removal: I led a National Academies of Science-invited (commissioned) chapter on the review and cost analysis of current state of ambient methane removal technologies such as electrocatalysis, which of these are feasible currently, and which of them can even scale up to meet climate goals.

How much and how did the reduction in sulfur dioxide emissions from the USA due to the Clean Air Act in 1970s increase the solar radiation that reaches the North Atlantic?

Ongoing project in the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison, with Prof. Daniel J. Vimont

2025 Sulfate seasonality over the North Atlantic: This submitted paper in GRL examines how the U.S. SO2 emissions cause an SO4 seasonality over the North Atlantic, how SO4 seasonality has changed over the North Atlantic between 1970 and now, and what are its radiative forcing implications. Stay tuned for more updates!

How much carbon monoxide do vehicles emit during their operation?

I did an undergraduate project to assemble a low-cost carbon monoxide sensor the size of a small (a phone's surface area) box that can be put inside a car and sampled directly from the exhaust pipe. The sensor measures carbon monoxide concentration in the outlet stream and I looked at how cars emit CO during a normal start, acceleration, cruise, deceleration, and steady operation.

Findings: The variations in CO were not much! But a more important finding was that many cars I sampled did not emit more than 10% of the current Indian emission standards! It certainly was a sampling bias as I got my hands on only newer cars.