Photo by Edsel Pingol on Unsplash
MANILA, PHILIPPINES [TAC] – Naturally occurring sea salt interacts with urban emissions to create complex chemical reactions that impact air quality in coastal megacities like Metro Manila, according to a study published by researchers from the Manila Observatory – Ateneo de Manila University and the University of Arizona.
The research, published in ACS Earth and Space Chemistry, used the unique conditions of the COVID-19 pandemic lockdowns to isolate how human activity influences the behavior of salt-derived aerosols—specifically sodium and chloride—in the atmosphere.
The study revealed that sea salt particles do not merely mix with urban smog but undergo chemical transformations. In high-pollution environments, vehicle and industrial emissions create an acidic
atmosphere that triggers “chloride depletion,” a process that strips chloride from sea salt particles.
“The researchers showed that sea salt particles and urban pollution do not simply mix when they meet in the atmosphere; pollutants chemically react with and transform the sea salt particles,” the report stated, noting that these interactions can have negative effects on respiratory health.
Data gathered during 48-hour sampling intervals showed that chloride and sodium concentrations actually increased after lockdown measures were implemented. With the reduction in traffic and industrial activity, the air became less acidic, allowing the naturally occurring chloride to persist in the atmosphere rather than being depleted by pollutants.
The findings highlight the challenges for policymakers in coastal regions, where natural marine elements and man-made pollutants create a volatile atmospheric mix. The team, led by researcher Grace Betito and experts from Ateneo de Manila University, suggests that future government interventions must be evidence-based and account for these complex chemical dynamics.
The authors have recommended further integrated studies measuring gas emissions and weather conditions to better understand the long-term implications for climate and public health in the Philippines’ capital.
