A comparative study was conducted to (1) assess the potential of raw sewage used for urban agriculture to disseminate bacterial resistance in two cities of different size in Cameroon (Central Africa) and (2) compare the outcome with data obtained in Burkina Faso (West Africa). In each city, raw sewage samples were sampled from open-air canals in three neighbourhoods. After DNA extraction, the microbial population structure and function, presence of pathogens, antibiotic resistance genes and Enterobacteriaceae plasmids replicons were analysed using whole genome shotgun sequencing and bioinformatics. Forty-three pathogen-specific virulenc e factor genes were detected in the sewage. Eighteen different incompatibility groups of Enterobacteriaceae plasmid replicon types (ColE, A/C, B/O/K/Z, FIA, FIB, FIC, FII, H, I, N, P, Q, R, T, U, W, X, and Y) implicated in the spread of drug-resistance genes were present in the sewage samples. One hundred thirty-six antibiotic resistance genes commonly associated with MDR plasmid carriage were identified in both cities. Enterobacteriaceae plasmid replicons and ARGs found in Burkina Faso wastewaters were also present in Cameroon waters. The abundance of Enterobacteriaceae, plasmid replicons and antibiotic resistance genes was greater in Yaounde, the city with the greater population.In conclusion, the clinically relevant environmental resistome found in raw sewage used for urban agriculture is common in West and Central Africa. The size of the city impacts on the abundance of drug-resistant genes in the raw sewage while ESBL gene abundance is related to the prevalence of Enterobacteriaceae along with plasmid Enterobacteriaceae abundance associated to faecal pollution.

Aerosol black carbon (BC) is the second strongest contributor to global warming, after CO₂, and it is linked to many adverse health effects. A sampling campaign of 15 months was carried out in León (Spain) in order to evaluate the scavenging of BC with an ensemble aethalometer-disdrometer. The aethalometer provides the concentration of equivalent black carbon (eBC), and the disdrometer, the raindrop size distribution. A total of seventy-five rain events were studied and in 73% of them there was an effective (eBCᵢₙᵢₜᵢₐₗ > eBCfᵢₙₐₗ) scavenging, with a mean decrease of 48 ± 37% in long rain events (>8 h) and 39 ± 38% in short rain events. The scavenging of BC is strongly related to its source. Thus, the scavenging coefficient (SC) mean value of the BC from fossil fuel (eBCff) for short and long rain events was 5.1 10⁻⁵ and 1.3 10⁻⁵ s⁻¹, respectively. For the BC from biomass burning (eBCbb), the SC values were 1.6 10⁻⁴ and 2.8 10⁻⁵ s⁻¹ in short and long events, respectively. There was a significant positive correlation between the SC and the number of drops with diameters between 0.375 and 2.5 mm. Rain scavenging of eBC was analyzed depending on the air mass origin obtaining an effective scavenging for air masses from Atlantic, Arctic and Africa. A linear model (R² = 0.72) was built to estimate the ΔeBC values with variables from an aethalometer, a disdrometer and a weather station: eBC concentration before rain, swept volume and precipitation accumulated. A Kolmogorov-Smirnov statistical test confirmed the goodness of fit of the model to the measured data.

As the global population becomes more concentrated in urban areas, resource consumption, including access to pharmaceuticals, is increasing and chemical use is also increasingly concentrated. Unfortunately, implementation of waste management systems and wastewater treatment infrastructure is not yet meeting these global megatrends. Herein, pharmaceuticals are indicators of an urbanizing water cycle; antidepressants are among the most commonly studied classes of these contaminants of emerging concern. In the present study, we performed a unique global hazard assessment of selective serotonin reuptake inhibitors (SSRIs) in water matrices across geographic regions and for common wastewater treatment technologies. SSRIs in the environment have primarily been reported from Europe (50%) followed by North America (38%) and Asia-Pacific (10%). Minimal to no monitoring data exists for many developing regions of the world, including Africa and South America. From probabilistic environmental exposure distributions, 5th and 95th percentiles for all SSRIs across all geographic regions were 2.31 and 3022.1 ng/L for influent, 5.3 and 841.6 ng/L for effluent, 0.8 and 127.7 ng/L for freshwater, and 0.5 and 22.3 ng/L for coastal and marine systems, respectively. To estimate the potential hazards of SSRIs in the aquatic environment, percent exceedances of therapeutic hazard values of specific SSRIs, without recommended safety factors, were identified within and among geographic regions. For influent sewage and wastewater effluents, sertraline exceedances were observed 49% and 29% of the time, respectively, demonstrating the need to better understand emerging water quality hazards of SSRIs in urban freshwater and coastal ecosystems. This unique global review and analysis identified regions where more monitoring is necessary, and compounds requiring toxicological attention, particularly with increasing aquatic reports of behavioral perturbations elicited by SSRIs.

Since 2011, tropical beaches from Africa to Brazil, Central America, and the Caribbean have been inundated by tons of sargassum seaweed from a new equatorial source of pelagic sargassum in the Atlantic. In recent years the extraordinary accumulations of sargassum make this a nuisance algal bloom for tropical coasts. In 2018 satellite data indicated floating mats of sargassum that extended throughout the Caribbean to the northeast coast of Brazil with the highest percent coverage over the water yet recorded. A literature review suggests that Atlantic equatorial recirculation of seaweed mats combined with nutrients from several possible sources may be stimulating the growth and accumulations of sargassum. In the western equatorial recirculation area, new nutrient sources may include Amazon River floods and hurricanes; in the eastern equatorial recirculation area, nutrient sources that could sustain the sargassum blooms include coastal upwelling and Congo River freshwater and nutrients.

The toxic equivalences (TEQs) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) from sediment of aquatic systems in Durban, South Africa were determined in two ways: 1) TEQs of PAHs and PCBs were determined by instrumental analyses and converted to 2,3,7,8‑tetrachlorodibenzo‑para‑dioxin equivalence (TCDDeq). 2) Bioassay equivalences (BEQs) of aryl hydrocarbon receptor (AhR) ligands were analysed using the H4IIE-luc bioassay. TEQs of PCBs ranged from below limit of detection (<LOD) to 57 pg TCDDeq·g⁻¹ while PAHs ranged from <LOD to 790 pg TCDDeq·g⁻¹. BEQs were 100- to 1000-fold greater than TEQs. Potency-balance revealed <10% of the BEQs were explained by instrumentally analysed compounds. Sediment quality guidelines indicated di minimis risk relating to TEQs, however had potential risk due to BEQs. The results reveal that far more AhR ligands were present in the sediments than what was instrumentally analysed and capable of causing AhR-mediated toxicity.

Although the role that renewable energy consumption plays on economic growth and emissions has been widely studied, there are relatively few papers focusing on the determinants of renewable energy consumption, and only one study focuses on the factors related to the share of renewables in the energy consumption in Africa. This paper contributes to the literature by filling the gap in knowledge by exploring the nexus between the share of renewables in energy consumption and social and economic variables, for a panel consisting of 21 African countries for the period between 1990 and 2013, extending the set of variables and the time span used by a previous study. Estimating a random-effects generalized least squares regression, we find that countries with a higher Human Development Index and a higher gross domestic product per capita have a lower share of renewable energy in the national grid. On the other hand, an increase in foreign direct investment has been found to be related to higher renewable energy integration. The level of democracy, measured by the Freedom House political rights and civil liberties ratings, does not directly affect the integration level of renewable energy sources. The negative relationship between gross domestic product per capita and the share of renewables contradicts previous findings for developed countries. This contradiction and policy implications are discussed in the light of the review of the energy mix of the selected countries.

The distribution of emerging organic contaminants in drinking water sources in Africa is a subject with very scanty data and information. In order to fill knowledge gaps, we report here the distribution and potential ecological risks of three phenolic compounds (bisphenol A (BPA), 4-nonylphenol (NP), and 4-tert-octylphenol (OP)), which have been previously identified to have the potential of endocrine disrupting activity, in surface water and sediment of the New Calabar River. The compounds were quantified using GC-MS. At all sampling sites, a similar concentration pattern of BPA > NP > OP was recorded, with the exception of Choba sampling station in which the levels of these endocrine disrupting compounds were low or undetectable. The levels of BPA in surface water ranged from 1.20 to 63.64 μg/L, whereas those of NP and OP ranged from < 0.20 to 2.15 μg/L and from < 0.10 to 0.68 μg/L, respectively. For sediments, measured levels were from 1.20 to 66.57 μg/kg for BPA, from < 0.35 to 3.37 μg/kg for NP, and from < 0.13 to 0.90 μg/kg for OP. Risk quotients (RQs) assessed for some sensitive organisms (algae, Daphnia magna, and fish) were above 1 for BPA and NP, whereas RQs for OP were below 1. This implies that BPA and NP at the levels detected could have potential risks to the sensitive organisms considered, but low risk for OP.

In this study, we assess the validity of an African-scale groundwater pollution model for nitrates. In a previous study, we identified a statistical continental-scale groundwater pollution model for nitrate. The model was identified using a pan-African meta-analysis of available nitrate groundwater pollution studies. The model was implemented in both Random Forest (RF) and multiple regression formats. For both approaches, we collected as predictors a comprehensive GIS database of 13 spatial attributes, related to land use, soil type, hydrogeology, topography, climatology, region typology, nitrogen fertiliser application rate, and population density. In this paper, we validate the continental-scale model of groundwater contamination by using a nitrate measurement dataset from three African countries. We discuss the issue of data availability, and quality and scale issues, as challenges in validation. Notwithstanding that the modelling procedure exhibited very good success using a continental-scale dataset (e.g. R² = 0.97 in the RF format using a cross-validation approach), the continental-scale model could not be used without recalibration to predict nitrate pollution at the country scale using regional data. In addition, when recalibrating the model using country-scale datasets, the order of model exploratory factors changes. This suggests that the structure and the parameters of a statistical spatially distributed groundwater degradation model for the African continent are strongly scale dependent.

The climate change issue becomes more challenging with the increasing pace of urbanization in Africa. For this purpose, we attempt to examine the relationship urbanization and CO₂ emissions by applying the panel smooth transition regression model for 47 African countries during the spanning time 1990–2014. Our results reveal that the nexus between urbanization and CO₂ emissions is non-linear. Our highlights recorded a monotonic nexus confirming the existence of the EKC hypothesis for the urbanization. In addition, our empirical results determine the threshold of the transition which takes the value of 42.01. Moreover, the estimated slope parameter implies that the nexus between urbanization and CO₂ emissions smoothly switches from one regime to another regime but relatively rapid. Hence, it is extremely important to understand this nexus to take seriously climate change vulnerabilities. Indeed, the African economies are invited to establish efficiently the low-carbon and reduce the spatial heterogeneity to generate the green development path and provide effective structures for a platform for sustainable cities.

Human health risks of five different heavy metals were assessed in nine typical areas in Asia, Europe, and Africa. The geoaccumulation index (Igₑₒ) of arsenic (As) in Hyderabad (HB), cadmium (Cd) in Veles (VL), and lead (Pb) in Murcia (MC) were found to be 5, indicating extreme contamination. This is related to their high concentrations in soil. The concentration of As in wheat in Niger Delta (ND) and European Union (EU) areas were 3.3 and 2.55 mg/kg, which were 22 and 17 times respectively of the World Health Organization (WHO)/Food and Agriculture Organization (FAO) criteria. In general, the concentrations of heavy metals in wheats were higher than those in corns, indicating that heavy metals were easier to accumulate in wheats than in corns. The human risks induced by the carcinogenic metals As and Cd were much higher than those induced by noncarcinogenic metals in different exposure ways. The human health risks of heavy metals in different exposure ways were Rw₋ᵢₙg > Rc₋ᵢₙg > Rₛ₋ᵢₙg > Rₛ₋dₑᵣ > Rₛ₋ᵢₙₕ. The human health risks induced by wheat ingestion for adults and children accounted for 67.75–97.52% and 69.52–98.04%, respectively, of the total human health risks. The total human health risks in the VL and MC areas were 1.58 × 10⁻⁴ a⁻¹ and 1.3 × 10⁻⁴ a⁻¹ for adults and 1.14 × 10⁻⁴ a⁻¹ and 9.47 × 10⁻⁵ a⁻¹ for children, respectively, which were significantly high according to the Environmental Protection Agency and International Commission on Radiological Protection. The ranking of the total human health risks in different areas were RVL > RMC > RND > REU > RHB > RKY > RTB > RMLV > RNHM. The total human health risks of adults were higher than those of children.