Source apportionment of PM10 and PM2.5 in a desert region in south. http://dx.doi.org/10.1016/j.scitotenv.2012.12.007

Abstract

Estimating contributions of anthropogenic sources to ambient particulate matter (PM) in desert regions is achallenging issue because wind erosion contributions are ubiquitous, significant and difficult to quantify byusing source-oriented, dispersion models. A receptor modeling analysis has been applied to ambient PM10and PM2.5 measured in an industrial zone ~20 km SE of Antofagasta (23.63°S, 70.39°W), a midsize coastalcity in northern Chile; themonitoring site is within a desert region that extends fromnorthern Chile to southern Perú. Integrated 24-hour ambient samples of PM10 and PM2.5 were taken with Harvard Impactors; samples were analyzed by X Ray Fluorescence, ionic chromatography (NO3− and SO4=), atomic absorption (Na+, K+) and thermal optical transmission for elemental and organic carbon determination. Receptor modeling was carried out using Positive Matrix Factorization (US EPA Version 3.0); sources were identified by looking at specific tracers, tracer ratios, local winds and wind trajectories computed from NOAA’s HYSPLIT model. For the PM2.5 fraction, six contributions were found — cement plant, 33.7±1.3%; soil dust, 22.4±1.6%; sulfates, 17.8±1.7%; mineral stockpiles and brine plant, 12.4±1.2%; Antofagasta, 8.5±1.3% and copper smelter, 5.3±0.8%. For the PM10 fraction five sources were identified — cement plant, 38.2±1.5%; soil dust, 31.2±2.3%; mineral stockpiles and brine plant, 12.7±1.7%; copper smelter, 11.5±1.6% and marine aerosol, 6.5±2.4%.Therefore local sources contribute to ambient PM concentrations more than distant sources (Antofagasta,marine aerosol) do. Soil dust is enriched with deposition of marine aerosol and calcium, sulfates and heavymetals from surrounding industrial activities. The mean contribution of suspended soil dust to PM10 is 50 μg/m3and the peak daily value is 104 μg/m3. For the PM2.5 fraction, suspended soil dust contributes with an average of 9.3 μg/m3 and a peak daily value of 31.5 μg/m3.