Dust and Salt in South America

Dust and Salt in South America

Mar Chiquita in central Argentina is a shallow, salty, and variable lake. When the water level is high, the lake covers as much as 6,000 square kilometers (2,300 square miles). When low, it shrinks to 2,000 square kilometers (770 square miles), exposing expansive salt and mud flats along its northern shore.

On July 10, 2022, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this natural-color image of dust streaming from Mar Chiquita. Water levels are now consistently much lower than they were during the 1980s and 1990s. Observers of the lake say the drawdown is likely due to ongoing cycles of rainfall and drought, and withdrawals of water for irrigation from a key tributary.

The exposed salt flats are a large source of dust in the region. Researchers using satellites to track the frequency of dust storms near the lake recorded an average of 10 to 20 events per month during the winter, typically the windiest and dustiest season.

Mar Chiquita dust storms include high concentrations of salt, raising concerns that the storms could damage soils around the lake through a process called sodification, making soil less productive for farmers. Crops grown in this area include corn, wheat, soybeans, and sunflowers.

However, a recent study led by researchers from the National University of Córdoba may offer some reassurance to farmers. By analyzing soil and air samples during and after dust storms, and modeling the movement of dust plumes, the researchers found that rains and wind diluted and dispersed the salt to levels that were not generally damaging to soil.

“In most areas around the lake, the amount of soluble sodium carried by dust and deposited in soils was low compared to the amount already present in the soils,” explained lead-author Laura Borda. The exception was fields very close to (less than 50 kilometers) Mar Chiquita. “These areas received much stronger doses of salt, likely enough to harm the productivity of the soil,” she said. Another important caveat: “We were focused on short-term effects—those seen in a year or less. The long-term effects of low levels of salt in the soil remain unknown.”

NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Adam Voiland.

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