Polycyclic aromatic hydrocarbons (PAHs), a ubiquitous substance in the environment, are closely associated with human energy consumption, which can be released to the environment from incomplete biomass combustion or emitted from petroleum. There is currently a knowledge gap on the relationships between energy consumption structures (ECSs) and PAH contamination, especially in African countries. This study investigated the distribution, sources, and risks of 16 prioritized PAH compounds (Σ16PAHs) in Ethiopia, and explored the impact of ECSs on PAH contamination. The concentrations of Σ16PAHs ranged from 12.51 to 435.67 ng/g, descending across an urban-rural gradient. Based on diagnostic ratios and positive matrix factorization (PMF) model, biomass combustion and vehicle emissions were the most important sources. By comparing the ECSs and PAH concentrations in African countries, it was found that differences in ECSs shaped the diverse patterns of sources and concentrations of PAHs in Africa. The results of incremental lifetime cancer risk assessment suggested PAHs posed a low risk to children, adolescents, and adults at some sampling sites. The Ethiopian government has been making continuous efforts to develop cleaner energy and optimize ECSs to decrease soil PAH concentrations and reduce potential risks. This study will provide support for Ethiopia to improve energy structure management.

Human activity increases as population increases. The environment must be altered in response to the pressures increasing population creates. Altering the environment may pose a risk to the health of natural habitats. The health and quality of habitats promotes biodiversity in ecosystems. Biodiversity is necessary for a functioning ecosystem as species work synergistically to create a livable environment. It is therefore important to know how practices and events threaten these habitats and the species living in them. This work details how research is used to formulate a framework for identifying habitat threats in any given region, determine habitat suitability, assess habitat sensitivity to different threats, and ultimately model how the quality of habitats change under different land use/cover scenarios. A meta-analysis of how different authors define and characterize threat in various contexts was done. The results of this analysis aids in the process of threat mapping, regional analysis, and land development planning. Knowledge gained from this study was used to evaluate regions on a watershed level using a combination of GIS technology and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model with the goal of performing vulnerability analyses.

The hydrological processes in Upper Choctawhatchee River Watershed were modeled using the Soil and Water Assessment Tool (SWAT) to investigate the impacts of climate and land use change. We integrated land use projection based in the Shared Socioeconomic Pathways with future climate data to study the combined effects on Hydrological response of the watershed. Future rainfall and temperature, for two time periods, were obtained using General Climate Models to provide SWAT with the climatic forcing in order to project water balance variables. The simulation was carried out under two radiative forcing pathways of RCP4.5 and RCP6.0. Model calibration metrics of NSE, R2, and p-factor were 0.88, 0.89, and 0.68, respectively. Results revealed increases as high as 2.55 ℃ and 2.4 ℃ for average annual minimum and maximum temperature, respectively, especially during Summer and Winter. Average annual precipitation was estimated to increase up to 11% under both emission scenarios; however, under severe emissions of RCP6.0, it was projected for two decades earlier. Land use change focused on urbanization dominated the climate changes. Impacts on water balance variables differed seasonally. Results showed surface runoff experienced major changes under both emission scenarios in some months up to 5 times increase. Among the water balance variables, ET as the least dominant pathways for water loss, showed the modest changes with the largest decrease during Fall and Summer. Projection indicated more frequent extreme behavior regarding water balance during midcentury. Discharge was estimated to increase through the year and the highest changes were projected during Summer and Fall with 186.3% increase in November under RCP6.0. Relying on rainfall for farming along with reduced agricultural landuse (11.8%) and increased urban area (47%) and population growth, would likely make the water use efficiency critical. The model demonstrated satisfactory performance, capturing the hydrologic parameters. It thus can be used for further modelling of water quality to determine the sustainable conservation practices, extreme weather events such as hurricane and tropical storms.