ENSO effects on the relationship between aerosols and evapotranspiration in the south of the Amazon biome.

The effects of the El Nino-Southern Oscillation (ENSO) events have local, regional, and global consequences for water regimes, causing floods or extreme drought events. Tropical forests are strongly affected by ENSO, and in the case of the Amazon, its territorial extension allows for a wide variation of these effects. The prolongation of drought events in the Amazon basin contributes to an increase in gas and aerosol particle emissions mainly caused by biomass burning, which in turn alter radiative fluxes and evapotranspiration rates, cyclically interfering with the hydrological regime. The ENSO effects on the interactions between aerosol particles and evapotranspiration is a critical aspect to be systematically investigated. Therefore, this study aimed to evaluate the ENSO effect on a site located on the southern portion of the Amazonian region. In addition to quantifying and testing possible differences between aerosols and evapotranspiration under different ENSO classes (El Niño, La Niña and Neutrality), this study also evaluated possible variations in evapotranspiration as a function of the aerosol load. A highly significant difference was found for air temperature, relative humidity and aerosol load between the El Niño and La Niña classes. For evapotranspiration, significant differences were found for the El Niño and La Niña classes and for El Niño and Neutrality classes. Under the Neutrality class, the aerosol load correlated significantly with evapotranspiration, explaining 20% of the phenomenon. Under the El Niño and La Niña classes, no significant linear correlation was found between aerosol load and evapotranspiration. However, the results showed that for the total data set, there is a positive and significant correlation between aerosol and evapotranspiration. It increases with a quadratic fit, i.e., the aerosol favors evapotranspiration rates up to a certain concentration threshold. The results obtained in this study can help to understand the effects of ENSO events on atmospheric conditions in the southern Amazon basin, in addition to elucidating the role of aerosols in feedback to the water cycle in the region.

Estimates of methane emissions and comparison with gas mass burned in CDM action in a large landfill in Eastern Amazon.

This work studied the methane gas production of the Aura landfill, the official destination of all Municipal Solid Waste of the Metropolitan Region of Belem (Brazil), operational until 2015. In 2007, the Aura Landfill was equipped with a landfill gas burning system in a CDM/UNFCCC project, with reported measured volumes of burned methane gas. These volumes were used to retrieve the methane generation potential (L0) and the decay rate (k) parameters of single-phase, first order landfill emission model, yielding L0=(61.0±6.6)mCH43/MgMSW and k=(0.25±0.07)yr-1. To model the Aura landfill, local gravimetric waste composition and local per capita waste production studies were collected, and the IPCC first order multiphase model was used. For the generation potential, observation and model are consistent, but for the decay rate, observations provide a 39% higher value, suggesting that the methane production from deposited MSW is occurring much faster than predicted by the IPCC model. Applying the retrieved parameters for the whole landfill's lifetime, the total produced methane is estimated to be 497 Gg (ranging from 444 Gg to 550 Gg), of this total 48% may have been emitted before the implementation of the collection system, indicating that it was implemented too late, and 81% may have been emitted before the closing date, with only 19% to be emitted after the end of operations. Subtracting the total methane volume burned in the CDM Activity, the Aura landfill may have emitted on total from 9.4 to 9.8 Tg of CO2 equivalent.