Methane gas emissions from savanna fires: what analysis of local burning regimes in a working West African landscape tell us

Savanna fires contribute significantly to greenhouse gas emissions. While it is recognized that these fires play a critical role in the global methane cycle, there are too few accurate estimates of emissions from West Africa, the continent's most active fire region. Most estimates of methane emissions contain high levels of uncertainty as they are based on generalizations of diverse landscapes that are burned by complex fire regimes. To improve estimates we used an approach grounded in the burning practices of people who set fires to working landscapes. We collected and analyzed smoke samples for 36 experimental fires using a canister method for the early dry season (EDS) and mid-dry season (MDS). We also collected data for savanna type, grass type, biomass composition and amount consumed, scorch height, speed of fire front, fire type, and ambient air conditions for two sites in Mali. We report values for fire intensity, combustion completeness, patchiness, modified combustion efficiency (MCE), emission factor (EF) and methane emission density. Our study found that mean methane EFs ranged from 3.83 g kg−1 in the EDS to 3.18 g kg−1 in the MDS, but the small sample did not provide enough power for this effect to be significant. We found head fires had nearly double the CH4 EF of backfires (5.12 g kg−1 to 2.74), a significant difference. Byram's fire intensity was a significant driver of CH4 EF but with weak effect. Methane emission density increased marginally from 0.839 g m−2 in the EDS to 0.875 g m−2 in the MDS, a difference that was not significant. Head fires, however, had much higher emission densities than backfires – 1.203 vs. 0.708 g m−2 – respectively, a significant difference. We suggest the reason for the higher methane emissions from head fires, which have higher intensity, is the longer flame lengths that burn green leaves on trees, releasing methane. We conclude that policies aimed at shifting the burning regime earlier to reduce methane emissions will not have the desired effects, especially if fire type is not considered. Future research should consider the state and amount of leafy biomass combusted in savanna fires.

Долговременная воспроизводимость эмиссионных характеристик алмазографитовых полевых источников электронов в нестационарных вакуумных условиях эксплуатации

The results of a study of the long-term reproducibility of the emission characteristics of electron sources with field emission density of up to 1000 A/cm2 of based on composite nanocarbon films are presented. It was found that high-current field emission is accompanied by the sputtering of residual gas ions from atoms of the cathode material and its sedimentation on the anode. The results can be used to predict the durability of high-current diamond-graphite cathodes with field emission when operating in unsteady temperature-vacuum conditions.

Pollutant emission in the air of Mogilev region

The purpose of this article is to highlight and analysis of trends in total emissions of polluting substances in atmospheric air of Mogilev region. The main material. A brief overview of Belarusian scientistsʹ research in the fi eld of geoecological conditions of atmospheric air is given in the article. The article deals with pollutants accumulation in the air of Mogilev region from various sources. Mobile sources (64.1% in 2015) are mainly responsible for air pollution in the region. In 2015 in comparison with 2010 there was a decrease in pollutant emissions as a result of transport functioning. Sources of pollutants accumulating in the air are exhaust gases from internal combustion engines, crankcase gases and fuel evaporation from fuel systems. Automobiles dominate in the structure of vehicles (85.3% in 2015). The article considers dynamics of pollutant emissions from stationary sources. The majority of pollutants are found in the air because of technological processes. Hydrocarbons and sulfur dioxide prevail in the structure of emissions of these sources. Chemical industry enterprises (Mogilev chemical fiber, Mogilev artificial fiber plant, etc.) are the sources of air pollution. Substances of the 4th and 3d danger classes predominate in the structure of pollutants in Mogilev region. Substances of the 1st and 2nd danger classes are insignificant. Conclusions. As a result of the conducted research uneven territorial distribution of emission density of the main pollutants in the air of Mogilev region has been established. Kostiukovich and Krichevsk districts are characterized by high level of emission density of suspended substances, carbon monoxide, sulfur dioxide in the air from stationary sources. Cherikov district is characterized by a low level of carbon monoxide, sulfur dioxide, nitrogen oxide emissions per unit area. 71.4% of the administrative districts of Mogilev region are characterized by an average density level of carbon monoxide emissions from stationary sources in relation to the average regional level, 14.3% of districts by lower level, 4.8% by low level and 9.5% by high level. It is advisable to improve the production technology, to equip enterprises with new gas cleaning facilities in order to reduce the anthropogenic load on the environment.

Experimental Study on Diesel Engine Fueled with Different Proportions of Diesel – Methanol Blend

Cosolvent is used and a fuel blend of diesel oil and methanol is made to help solve the problem of intermiscibility of the two. Comparative experiment is made on the power performance and emission characteristics of a 4102QB DI diesel engine with diesel and different proportion of fuel blend of 10%, 20% and 30% methanol respectively. Test results indicate that, providing there is no change to the diesel engine parameter and basic structure, the increased percent of methanol will cause drops of power performance and significant reduction of smoke emission density and CO, but amount of emission density of HC and NOxis slightly increased. However, the emission density does not change too much.