Determination of the Impact to air quality by the sugar cane burning during harvesting in Costa Rica: regional and temporal analysis.

Abstract:

In Costa Rica, as in other countries, sugar-cane crops are burned to facilitate harvesting, and such process causes environmental pollution from the smoke that is released to the atmospheric boundary layer. In this study, during the harvest season, were determined PM₁₀, PM_2.5, ions, heavy metals and PAHs concentrations in the air of 8 different regions of Costa Rica. The sampling methodology included 47 events with 3 sampling sites per each; these sites covered different climate regions of the country. PM₁₀ and PM_2.5 were collected using Hi-vol samplers with quartz-fiber filters using a thermal pre-preprocess for organics. PM₁₀ ranged from 25 to 390 µg/m³, PM_2.5 from 25 to 354 µg/m³; the minimum results were obtained at the sixth region and the maximum ones at the second one, both located in the North Pacific. As a reference, in the metropolitan area of Costa Rica the PM10 usually have had annual means behind 30 µg/m³. The most abundant ions found in PM₁₀ were chloride, nitrate and sulfate. Meanwhile, the ranges of Fe, Cr, Cu, and Pb were 0,03 – 6,80 µg/m³, 10,6 – 358,0 ng/m³, 11,8 – 361,4 ng/m³ and 0,67 – 479,50 ng/m³, respectively. The PAH most abundant were the naphthalene and the acenaphthylene. The mean total concentration of PAHs in PM₁₀ was 7,9 ng/m³ with a standard deviation of 3,3 between regions. According to the PM₁₀ medians, the regions with more pollution levels were the 3 and 4, while the regions 4 and 5 were the least contaminated. On the other hand, the atmospheric contaminants’ concentration was significantly higher in the diurnal burnings than the nocturnal ones. The sampling sites were directly affected by the emission of the sugar-cane burning.