National energy consumption structures modulate PAH source apportionment in Ethiopian soils

Abstract

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.