Source apportionment of PM10 and PM2.5 near a large mining zone in Northern Chile

Chile's economic growth is mainly driven by intensive mining activities; currently Chile produces ~ 40% of copper worldwide. Most of those activities are located in northern Chile, in a desert region where strong regional winds contribute with soil erosion as well. The city of Calama (22.4°S, 68.9°W) is about 17 km south of Chuquicamata, one of the largest open pit copper mines in the world, both located on the west edge of the Andes; Calama is at 2,400 m asl and it is 215 km east of the Pacific Ocean. The mining complex releases ~ 21 kton/y of PM10 and ~ 78 kton/y of SO2 from a copper smelter. The levels of ambient PM10 have steadily increased at Calama in the last 5 years, so there is concern about the impacts from copper industry in the city´s inhabitants, most of who work in mining or related economic activities. A campaign was conducted at Calama between October and December 2007, sampling ambient PM10 and PM2.5 at several sites across the city. Filters were analyzed at the Desert Research Institute, Reno, NV for elemental composition by XRF and for elemental and organic carbon using thermal analysis. The application of positive matrix factorization (PMF) model identified four sources contributing to ambient PM2.5: secondary sulfates (49%), traffic emissions (37%), dust street (9%) and copper smelter emissions (5%). In the coarse fraction, four sources were identified: dust street (45%), wind erosion (34%), mineral processing (14%) and copper smelter emissions (7%). No natural background was found for PM2.5. For ambient PM10 the source apportionment obtained is: mining activities (33%), street dust (34%), wind erosion (22%) and traffic emissions (12%). With a current PM10 annual average of 58 μg/m3 and further mining activities projected in the area, there is a big challenge to improve air quality in the populated area close to the mining operations.