Phil Kong

Research Highlights

Satellite chlorophyll-a map of the study area showing the bloom's formation.
Average chl-a (a) and soluble aerosol Fe flux (b) of surface waters within the bloom compared to three areas where the bloom did not form.

A link between aerosol Fe and atmospheric CO2 drawdown

In July 2022, a large phytoplankton bloom formed in the surface ocean northeast of the Hawaiian Islands. Within the bloom, we measured high iron concentrations in waters where the larger cell organisms and nitrogen fixers, both which have higher demand for Fe to grow, were thriving.

We observed that a large pulse of atmospheric iron was deposited 4-weeks prior to the formation of the bloom and may have played a role in providing critical nutrients to the waters where nitrogen fixing organisms can rapidly grow. We developed a modeling framework to identify and quanitfy atmospheric deposition pulses of Fe to the surface waters where the bloom formed.

Independent observations (Chow et al., 2025; Seelen et al., 2025) demonstrate that, following nutrient addition, the incubation period required to detect discernible nitrogen fixation activity in this region is approximately 3–4 weeks. We demonstrate that aerosol Fe deposition may play a critical role in facilitating atmospheric carbon dioxide drawdown during the summer months in this region.

Work published in Global Biogeochemical Cycles

DOI PDF

Source dust provenance of aerosols in the North Pacific.
Aerosol sampling locations (pentagons) overlaid on modeled percentage of dust deposition supplied by the dominant source region, adapted from Kok et al. 2021. Colors on the background map represent the different source regions for aerosol dust, with contours indicating regional source contribution changes by 10%.
Latitudinal distributions of (a) particulate Fe in bulk aerosols, (b) δ56Fe in bulk aerosols, (c) fraction of Fe solubilized by ultrapure water (UPW), (d) UPW soluble δ56Fe in aerosols, (e) particulate Fe in rainwater, (f) particulate δ56Fe in rainwater, (g) particulate Fe in surface seawater, (h) particulate δ56Fe in surface seawater.

Aerosol Fe supply to the North Pacific Ocean

Atmospheric deposition delivers Fe to the remote ocean where other sources are minimal. However, given their disparate and episodic nature, it is challenging to quantify their contribution to the surface ocean inventory.

Bulk aerosol Fe concentrations are collelated with Fe in rainwater and particulate Fe in the underlying surface seawater, indicating that atmospheric deposition is the primary source of Fe in the North Pacific Subtropical Gyre. Aerosol Fe solubility varies inversely with bulk aerosol Fe concentration, such that the highest-concentration samples in the subtropical gyre are the least soluble (1%) and the lowest-concentration equatorial samples are the most soluble (15%). We attribute this inverse relationship to the lithogenic content of the aerosol: samples with high total Fe are dominated by mineral dust, in which Fe is held in refractory aluminosilicate phases of low solubility, whereas samples with low total Fe likely carry a proportionally greater contribution from combustion and biomass-burning particles.

Work in prep for publication

Long term impact of contaminant loading after an urban fire

The Eaton Fires led to the destruction of over 20,000 homes in January 2025. Contaminants, including in lead, were significantly elevated immediately after the fire, measured in the smoke plume, runoff, and roadside dust. The source of lead likely came from burning structures containing lead in paint, plumbing, and car batteries, and resulted in widespread urban lead contaminants.

Source dust provenance of aerosols in the North Pacific.
32 sampling locations (11 within the burn zone and 21 outside of it) that compares levels of lead in roadside dust collected at those locations in early 2025 to samples collected in early 2026.
Average lead concentrations of roadside dust collected within (red) and outside (gray) the burn scar of the Eaton Fires. Lead concentrations were high within the burn scar during January 2025 immediately after the fires, and decreased closer to lead concentrations measured outside the burn scar after subsequent rain events that likely washed the roadside dust away

Contact

Email
kyeongpi at usc.edu
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