BVOC Emissions Along the Eastern and Western Slopes of the Andes Central Range with Strong Altitudinal Gradient over a Wide Range of Andean Ecosystems: Model Estimation/Disaggregation with BIGA

Abstract

Spatial and temporal emissions of biogenic volatile organic compounds (BVOCs) were estimated over a wide range of Andean ecosystems/ecotones, exhibiting high variability and highlighting the importance of BVOC emissions in the Tropical Andes, as precursors of secondary pollutants, of which the main concern is tropospheric ozone. The biogenic altitudinal gradient (BIGA) model was applied to a 7436-km2 area of the Colombian Andes with an altitude ranging from 140 to 5287 m a.s.l. Preliminary results revealed critical points of BVOC emission in lower elevational zones. Isoprene and monoterpene emissions were 41% and 20%, respectively, and were higher on dry days. For both dry and wet, the maximum fluxes occurred at 15:00 hours. Isoprene emissions were also estimated with the Weather Research and Forecasting model coupled to Chemistry (WRF-Chem) model that incorporates the module of Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGANv2.1). Isoprene comparison between MEGAN-WRF-Chem and BIGA suggests that these models estimate similar emission fluxes (maximum 13,200 μg m−2 h−1) on the same regions. However, the BIGA model was able to estimate higher-resolution flux and indicated the importance to resolve in mountain zones the altitude effect on BVOC emission. The BIGA model requires information from surface temperature and solar radiation (SR), a digital elevation model (DEM), and land cover and use (LCU) maps. This local information was processed at a resolution of 90 m × 90 m. The basic algorithm proposed by Guenther et al. (Journal of Geophysical Research 98:12609–12617, 1993) was implemented in the BIGA model using Matlab; the results were visualized with ArcGIS. In the Tropical Andes, small areas can be characterized by many distinct climactic zones that range from grasslands to mountain forests and paramo impacting BVOC emission rates and spatial distribution. Preliminary results show that the BIGA model adequately incorporated the strong Andean altitudinal gradient and differs from the global model MEGAN-WRF-Chem.