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Environmental impacts of oil activities in the Northeastern Ecuadorian Amazon: From the spatial study of vulnerability to risk assessments

Abstract : Ecuador is the 5th oil producer in Latin America. Most of crude oil reserves lie beneath the north-eastern Ecuadorian Amazon (NEA), representing 15% of the entire country, yet encompassing high biodiversity and cultural heritage. Crude oil and gas production generate toxic wastes potentially polluting the environment. The methodology was set to evaluate hazards and environmental vulnerability, using score indexes and rankings, as independent components of risk. Then, they were combined using spatial overlay methods. An observed hindrance for risk analysis was the quality of public data that were used in this study. In this context, the first aim was to determine accidental oil spill volumes in well-documented oil blocks. Then, putative spill volumes were allocated to poorly-documented oil blocks to obtain a homogeneous map. The second aim was to map key atmospheric emissions associated to gas flaring, i.e., greenhouse gas (CO2, CH4) and black carbon (BC) particles. The third aim was to assess the potential vulnerability of natural heritage using regional scale proxies such as protection status and land use. Finally, the fourth aim was to exemplify the presented risk assessment approach by evaluating total petroleum hydrocarbons (TPH) potentially flowing to groundwater from oil pits. Main results indicate 10,000.2 t (909.1 t.yr-1; SD = 1,219.5) oil spilled in the NEA during the 2001-2011 period (11 years), according to recorded events. However, a 54.8% increase was found when extrapolating spill rates from well-documented oil blocks to poorly-documented ones. Spatial prediction accuracy ranged from 32 to 97%. Gas flared amounted to 7.6 Gm3 (760 Mm3.yr-1), equivalent to a range of 3.7 – 4.5 kt.yr-1 BC, during 2003-2012 lapse. Total petroleum hydrocarbons in unlined oil pits was estimated to 49,436.4 t. Several maps resulted from this thesis. Spatial emissions indicate spills and gas flaring are occurring at higher rates in settlements of Joya de los Sachas, Dayuma and Shushufindi. The natural heritage vulnerability maps indicated 42% of highly vulnerable surface at the most eastern side of the studied area. Groundwater vulnerability was low to medium in most areas; furthermore, the example considered for risk assessment of groundwater and unlined oil pits, indicated highest potential impacts in settlements of Nueva Loja, Tarapoa and Shushufindi. Publicly available data quality was found to be acceptable. For instance, when comparing airborne emission estimates with some other independent estimates only 2.5-fold difference was found at most. Spatial allocation accuracy of oil spills showed promising methodology for improving hazard mapping. Vulnerability assessment indicated natural heritage proxies to be suitable for building vulnerability indexes at regional scale as land use is significantly correlated to species richness, and protected areas are efficiently conserved in the long term, thus conveying some information on ecological integrity. Moreover, there was only 8.8% of spatial incongruence between the two proxies. Groundwater vulnerability mapping indicated gaps in knowledge that were discussed; some distance thresholds were proposed to select validation sites in future studies. In conclusion, estimates and maps obtained may be valuable for safety and security monitoring, accountability of public institutions and land use planning to lessen future risks.
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  • HAL Id : tel-02080465, version 1

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Juan Durango. Environmental impacts of oil activities in the Northeastern Ecuadorian Amazon: From the spatial study of vulnerability to risk assessments. Biodiversity and Ecology. Université Toulouse 3 Paul Sabatier, 2019. English. ⟨tel-02080465⟩

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