Ambient PM10 impacts brought by the extreme flooding event of March 24–26, 2015, in Copiapó, Chile

Abstract

On March 24–26, 2015, the Chilean city of Copiapó (27° 22′ S, 70° 20′ W), located in the hyperarid Atacama Desert, suffered an intense flooding brought by an extreme, unique rainfall event with a 35-year record of daily precipitation. A receptor model (positive matrix factorization, version 5) analysis, applied to ambient PM10 chemical speciation from three short-term sampling campaigns, resolved four sources: crustal/road dust, sea salt, secondary sulfates, and emissions from Paipote copper smelter located 8 km east of Copiapó. Wind trajectories computed with US NOAA’s Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) supported the above source identification and explained variability in source contributions. It was found that crustal/road dust increased 50 μg/m3, in April 8–10, 2015, as compared with values in November 2014 and October–November 2015, respectively. This was the dominant PM10 source after the flooding and before debris were cleaned up, being on order of magnitude higher that the other source contributions. The Paipote copper smelter contributed with primary PM10 emissions and secondary sulfates; this combined contribution averaged 11.8 μg/m3. Sea salt contributions contributed an average of 3.3 μg/m3. In normal conditions, crustal/road dust averaged 2.9 μg/m3, but the other resolved sources also contributed with crustal elements as their emissions are transported by winds to Copiapó. The positive matrix factorization solution included an unresolved concentration of 7.4 μg/m3. The small number of samples and the lack of measurements of nitrate, ammonia, and organic and elemental carbon may explain this result. Hence, sources such as secondary nitrates and combustion sources plus fugitive dust from sources surrounding Copiapó might be included in that unresolved concentration.