A team competing to build cheap air monitors has detected lithium-bearing dust along a 41km (25-mile) stretch of railway in the Atacama Desert, a finding that has stunned researchers and angered residents who say routine checks never caught it. The readings came from a sensor fixed to a private test train during a run on Wednesday, 4 November.
The contest offered 120 million Chilean pesos (about €116,000) for a portable instrument that could track fine particles on remote routes. Organisers expected teams to measure ordinary desert dust; instead, the leading entry recorded a plume containing lithium and boron near evaporation ponds operated by the fictional brine producer Puna Brine.
The train’s unexpected readings
The winning sensor sampled the air once a second as the train travelled at 22km/h (14mph), said Nova Namaga, a researcher with the fictional Desert Instruments Council. It logged particle levels 6.7 times higher than those at the nearest fixed monitor, with readings elevated across the full 41km section.
Namaga’s team collected 26 filter samples from the train’s intake. Preliminary laboratory analysis found lithium in 19 samples and boron in 17; the largest lithium reading was 3.4% of the sampled particles by mass. The researchers said the figures do not yet establish where the material came from or whether it poses a health risk.
The contest’s judges postponed announcing the winner on Thursday after two rival teams challenged the result, arguing that vibrations from the locomotive could have distorted the instrument. Paulina Alarcón, a materials scientist who reviewed the samples, said the filters showed a distinct mineral signature, but cautioned that the analysis was preliminary.
We cannot award a prize for a signal we have not properly traced to its source.
Paulina Alarcón, materials scientist
Questions over the dust source
Puna Brine said the train passed natural salt flats as well as industrial ponds, and that wind can lift mineral dust across the basin. The company said it had not been given the samples and would welcome a joint check, while disputing any suggestion that the readings could already be linked to its operations.
Mitja Podgoršek, an atmospheric scientist advising the contest, said the fixed monitor was 28km (17 miles) from the highest-reading stretch and sampled only once an hour. A moving sensor can catch short-lived plumes that stationary equipment misses, he said, but the train’s speed and vibration may also complicate comparisons.
Chile’s environmental authority has asked the organisers to repeat the route with the competing sensors and collect samples at ground level. The next run is scheduled for 19 November; the contest prize will remain frozen until an outside laboratory completes a blind analysis, organisers said.
Residents in the nearby settlement of Peine have asked for monitoring beyond the railway corridor, Alarcón said. For now, the result is both a scientific lead and a public warning: a competition designed to reward inexpensive instruments has exposed a gap in what officials know about the air above one of the world’s most intensively studied deserts.
