NASA satellite captures massive wastewater flows off the California coast

In 2022, NASA’s Jet Propulsion Laboratory launched a satellite sensor to map minerals in dusty and arid areas of the planet. But that’s not all for this – in a new study, scientists used spectroscopic tools to study the flow of large amounts of sewage into the sea off the coast of Southern California.

Every year, unceremoniously dumped into the Tijuana River, millions of gallons of untreated and treated wastewater are dumped into the Tijuana River, polluting through communities on both sides of the U.S.-Mexico border before reaching the ocean. In a study published in the Journal Total Environmental Sciencethe researchers used the Hyperspectral Imaging Instrument (EMIT) on the International Space Station to examine this nauseating wastewater plume in the Tijuana River Delta.

The pollution of wastewater is not beautiful. It can bring toxic chemicals, harmful algae blooms and unfriendly bacteria that affect off-roaders’ health.

People usually rely on water quality dashboards to tell them when it is not safe to swim, but these usually rely on on-site samples that do not always cover the full range of contamination. Collecting these samples also takes time and money, especially in contaminated areas.

This is where the launch is. It uses imaging spectroscopy, a technique that captures spatial and spectral information by measuring sunlight reflected from the Earth’s surface. Each image can capture hundreds of wavelengths per pixel, allowing scientists to give detailed introductions to the molecular composition and material properties on the ground.

This allows the researchers to measure the spectral characteristics of wastewater plumes. The researchers compared the hyperspectral satellite images taken by EMIT with the spectra sampled by untreated wastewater, diluted wastewater and plume samples near the plume. They also compared the Emit image with the readings from the ground spectrometer. They found that water with high wastewater contamination emits a unique red spectral feature that allows researchers to monitor future levels of pollution, although the source of the feature remains unclear.

The researchers hope the data can supplement water quality near the estuary by telling water scientists where to take samples.

“From the track, you can’t see that the wastewater plume has extended to where you haven’t taken samples,” Christine Lee, a scientist at JPL in Southern California, said in a statement. “It’s like a doctor’s office diagnosis, telling you, ‘Hey, let’s take a closer look.'”

EMIT has also been shown to be used to detect methane and carbon dioxide emissions from gas leaks, assess forest health, and estimate snow melting rates.

Now, Emit has another job. “The discovery of launches in the coastal area is consistent with measurements in the field,” Eva Scrivner, a doctoral student at the University of Connecticut and lead author of the study, said in a statement. “It’s really exciting.”