Joint influence of architectural and spatiotemporal factors on the presence of Aedes aegypti in urban environments.

BACKGROUND: Urbanization has led to the proliferation of high-rise buildings, which have substantially influenced the distribution of dengue vectors, such as Aedes aegypti (L.). However, knowledge gaps exist regarding the individual and combined effects of architectural and spatiotemporal factors on dengue vector. This study investigated the interrelationship between Ae. aegypti presence, building architectural features, and spatiotemporal factors in urban environments. RESULTS: The mosquito Ae. aegypti presence varied by location and seasons, being higher in outdoor environments than in indoor environments. Lingya (Kaohsiung City, Taiwan) had the highest mosquito numbers, particularly in basement and first floor areas. Ae. aegypti was found on multiple floors within buildings, and their presence was greater in summer and autumn. The XGBoost model revealed that height within a building, temperature, humidity, resident density, and rainfall were key factors influencing mosquito presence, whereas openness had a relatively minor impact. CONCLUSION: To effectively address the problems caused by urbanization, the three-dimensional distribution of Ae. aegypti, including their spatial distribution across heights and areas within the urban environment, must be considered. By incorporating these multiple factors, this approach provides valuable insights for those responsible for urban planning and disease management strategies. Understanding the interplay between architectural features, environmental conditions, and the presence of Ae. aegypti is essential for developing targeted interventions and mitigating the adverse impacts of urbanization on public health. © 2023 Society of Chemical Industry.

Enhancement of mercury capture by the simultaneous addition of hydrogen bromide (HBr) and fly ashes in a slipstream facility.

Low halogen content in tested Powder River Basin (PRB) coals and low loss of ignition content (LOI) in PRB-derived fly ash were likely responsible for higher elemental mercury content (averaging about 75%) in the flue gas and also lower mercury capture efficiency by electrostatic precipitator (ESP) and wet-FGD. To develop a cost-effective approach to mercury capture in a full-scale coal-fired utility boiler burning PRB coal, experiments were conducted adding hydrogen bromide (HBr) or simultaneously adding HBr and selected fly ashes in a slipstream reactor (0.152 x 0.152 m) under real flue gas conditions. The residence time of the flue gas inside the reactorwas about 1.4 s. The average temperature of the slipstream reactor was controlled at about 155 degrees C. Tests were organized into two phases. In Phase 1, only HBr was added to the slipstream reactor, and in Phase 2, HBr and selected fly ash were added simultaneously. HBr injection was effective (>90%) for mercury oxidation at a low temperature (155 degrees C) with an HBr addition concentration of about 4 ppm in the flue gas. Additionally, injected HBr enhanced mercury capture by PRB fly ash in the low-temperature range. The mercury capture efficiency, attesting conditions of the slipstream reactor, reached about 50% at an HBr injection concentration of 4 ppm in the flue gas. Compared to only the addition of HBr, simultaneously adding bituminous-derived fly ash in a minimum amount (30 lb/MMacf), together with HBr injection at 4 ppm, could increase mercury capture efficiency by 30%. Injection of lignite-derived fly ash at 30 lb/MMacf could achieve even higher mercury removal efficiency (an additional 35% mercury capture efficiency compared to HBr addition alone).

Mercury emissions during cofiring of sub-bituminous coal and biomass (chicken waste, wood, coffee residue, and tobacco stalk) in a laboratory-scale fluidized bed combustor.

Four types of biomass (chicken waste, wood pellets, coffee residue, and tobacco stalks) were cofired at 30 wt % with a U.S. sub-bituminous coal (Powder River Basin Coal) in a laboratory-scale fluidized bed combustor. A cyclone, followed by a quartz filter, was used for fly ash removal during tests. The temperatures of the cyclone and filter were controlled at 250 and 150 degrees C, respectively. Mercury speciation and emissions during cofiring were investigated using a semicontinuous mercury monitor, which was certified using ASTM standard Ontario Hydra Method. Test results indicated mercury emissions were strongly correlative to the gaseous chlorine concentrations, but not necessarily correlative to the chlorine contents in cofiring fuels. Mercury emissions could be reduced by 35% during firing of sub-bituminous coal using only a quartz filter. Cofiring high-chlorine fuel, such as chicken waste (Cl = 22340 wppm), could largely reduce mercury emissions by over 80%. When low-chlorine biomass, such as wood pellets (Cl = 132 wppm) and coffee residue (Cl = 134 wppm), is cofired, mercury emissions could only be reduced by about 50%. Cofiring tobacco stalks with higher chlorine content (Cl = 4237 wppm) did not significantly reduce mercury emissions. This was also true when limestone was added while cofiring coal and chicken waste because the gaseous chlorine was reduced in the freeboard of the fluidized bed combustor, where the temperature was generally below 650 degrees C without addition of the secondary air. Gaseous speciated mercury in flue gas after a quartz filter indicated the occurrence of about 50% of total gaseous mercury to be the elemental mercury for cofiring chicken waste, but occurrence of above 90% of the elemental mercury for all other cases. Both the higher content of alkali metal oxides or alkali earth metal oxides in tested biomass and the occurrence of temperatures lower than 650 degrees C in the upper part of the fluidized bed combustor seemed to be responsible for the reduction of gaseous chlorine and, consequently, limited mercury emissions reduction during cofiring. This study identified the important impacts of temperature profile and oxides of alkali metal (alkali earth metal) on mercury emissions during cofiring in the fluidized bed combustor.