c8.3.7 – A GIS-based model to estimate the speciific biogenic volatile organic compounds (BVOC) emissions from some Italian terrestrial ecosystems

Kemper Pacheco CJ

Collocazione: c8.3.7 – Tipo Comunicazione: Presentazione orale
8° Congresso SISEF *
Sessione 3: “Clima e Foreste: quali scenari di impatto, mitigazione e adattamento?” *

Contatto: Claudia Justina Kemper Pacheco (claudia.kemper@mlib.imc.cnr.it)

Abstract: A GIS (Geographic Information System) model has been developed to estimate of the BVOC-specific emissions from plant species dominant in Italian forest ecosystems. BVOC play an important role in climatic changes because they are capable to produce tropospheric ozone and secondary organic aerosols (SOA), when exposed to the UV radiation in the presence of sufficient amounts of nitrogen oxides (NO and NO2). SOA can act as cloud condensation nuclei (CCN), that affect the radiation balance of the earth by promoting cloud formation. The model allows to estimate the emissions of individual components formed by the plant through different biochemical pathways. The model is unique because until now, biogenic emission has been expressed only in terms of isoprene and total monoterpenes. The aim of this work was to develop and test a GIS-based model able to predict the BVOC potential emission from forest areas of the Italian Peninsula at a 1 x 1 km spatial resolution in the frame of the Carboitaly Project. By using the emission rates of individual components obtained through several laboratory and field experiments carried out on different vegetation species of the mediterranean basin, maps of isoprene and individual monoterpenes were generated for the most relevant Italian forest ecosystems. The model, that can be run on an hourly basis, has been used to get data on a daily basis. The following are the methodological reports of the various modules of the GIS model with the frequency of each set of input data implemented in this work: a. The spatial distribution and fractional contents of vegetation species present in the Italian forest ecosystems was obtained by combining the CORINE IV land cover map with National Forest Inventory based on ground observations performed at local levels by individual Italian regions (22) in which the country is divided. b. In general, basal emission rates of isoprene and monoterpenes reported by Steinbrecher et al. 1997 and Karl et al. 2009 were used. In the latter case, classes were further subdivided into T and L T emitters as a function of the active pool Steinbrecher et al. 1997 and Karl et al. 2009. In many instances, however they were reviser based on the results obtained in our Institute through determinations performed at leaf, branch (cuvette method) or ecosystem level (REA and the gradient method). In the latter case, studies performed in Italy and/or Mediterranean countries were used. For most of the prevalent species, a data base for individual isoprenoids was created. c. An empirical light extinction function as a function of the canopy type and structure was introduced. The classical algorithms proposed by (Guenther et al. 1993) were used, but, they were often adapted to fit with the experimental observations made in the Mediterranean Areas. They were corrected for a seasonality factor (Steinbrecher et al. 2009) taking into account a time lag in leaf sprouting due to the plant elevation. d. A simple parameterization with LAI (Leaf Area Index) was introduced to account for the amount of monoterpene biomass from the litter of stands composed by plants equipped with storage organs. Daily data of incident PAR (Photosynthetically active radiation) and leaf temperature obtained from high resolved satellite observation were provided by the partners of the CARBOITALY Project. They were available for the entire year 2006. They were disaggregated into proper day-night cycle. Emission values predicted by the model are in perfect agreement with those that were measured by different micrometeorological techniques in Castelporzioano (Ciccioli et al, J Chromatogr., 2003) and in the Collelongo site (Baraldi et al. 2010). The good correlation between modeled and measured values emphasizes the fact that accurate predictions can be obtained if validated emission factors for individual VOC are used in the model. The almost equivalent potential emission of isoprene and monoterpenes reported in a previous work was confirmed, although lower values of total biogenic emissions were found for both classes of hydrocarbons. This is consistent with the fact that most abundant oak species present in Italy (Quercus Cerris) can be considered a non –isoprene emitter. Data from individual monoterpenes indicates also that highly reactive cis- and b-ocimenes are also quite abundant in many Italian forest ecosystems, including those dominated by coniferous trees, such as Pinus pinaster and sylvestris. This may lead to rather low dominance of pinene generated particles in the air. The high spatial and temporal resolution, combined with the species-specific emission output makes our model particularly suitable for ozono and SOA prediction with both Eulerian and Lagrangian photochemical models, at the scale at which ozono pollution develops in Italy.

Parole chiave: Volatile Organic Compounds, Monoterpenes, Geographic Information System, Light, Temperature

Citazione: Kemper Pacheco CJ (2011). A GIS-based model to estimate the speciific biogenic volatile organic compounds (BVOC) emissions from some Italian terrestrial ecosystems . 8° Congresso Nazionale SISEF, Rende (CS), 04 – 07 Ott 2011, Contributo no. #c8.3.7