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.

The usage of inadequately processed industrial waste water (WW) can lead to strong soil alkalinity and soil salinization of agricultural fields with negative consequences on soil properties and biota. Gypsum as a soil amendment to saline-sodic soils is widely used in agricultural fields to improve their soil physical, chemical and hence biological properties. This study aimed at analysing the effects of intensive WW irrigation on the structure and composition of soil-dwelling arthropods on spinach fields (Spinacia oleracea L.) in a West African urban vegetable production system. We used gypsum as a soil amendment with the potential to alleviate soil chemical stress resulting in a potentially positive impact on soil arthropods. A total of 32 plots were established that showed a gradient in soil pH ranging from slight to strong soil alkalinity and that were irrigated with WW (n = 12) or clean water (CW; n = 20), including eight plots into which gypsum was incorporated. Our study revealed a high tolerance of soil-dwelling arthropods for alkaline soils, but spinach fields with increased soil electrical conductivity (EC) showed a reduced abundance of Hymenoptera, Diptera and Auchenorrhyncha. Arthropod abundance was positively related to a dense spinach cover that in turn was not affected by WW irrigation or soil properties. Gypsum application reduced soil pH but increased soil EC. WW irrigation and related soil pH affected arthropod composition in the investigated spinach fields which may lead to negative effects on agronomical important arthropod groups such as pollinators and predators.

This study examines the effect of globalization and urbanization on deforestation in Burkina Faso, over the period 1980 to 2017. The study employed the autoregressive distributive lag (ARDL) model and the Toda-Yamamoto Granger causality approach. Empirical findings affirmed that globalization, urbanization, and agricultural land have a positive and significant effect on deforestation in the long run, while population density reduces the deforestation rate, thus indicating an improvement in environmental quality. On the other hand, urbanization, economic growth, and population density have a positive and significant impact on deforestation in the short run. Furthermore, the Granger causality approach confirmed a bidirectional association between deforestation and urbanization and between globalization and agricultural land, as well as between urbanization and population density. The result further affirmed a unidirectional causal link running from urbanization to agricultural land. Based on the empirical findings, the study recommends that the government should ensure more regulation on the removal of barriers to international trade. The study further recommends that the government should implement relevant agricultural policies to guard against deforestation since the results of the study suggest that agriculture contributes negatively to deforestation in Burkina Faso.

The present study aims to assess the impact of a gold mine located in the southeastern part of Burkina Faso on local soil quality. This information is needed in order to determine any health hazards and potential remediation strategies as the mining site is expected to be turned over to the local community after the closure of the mine. For the purpose, total minor and trace elements analysis as well as a sequential extraction were performed and results were interpreted using different methodologies: enrichment factor (EF), geoaccumulation index (Igeo) computed using two separate background samples, and comparison to selected national standard. The soil analysis revealed a moderate to significant soil EF and Igeo with hotspots located closer to the ore processing plant and on the east side of the site, with a maximum arsenic concentration of 286.55 ± 12.50 mg/kg. Sequential extraction revealed, however, that less than 2% of the arsenic is found in the exchangeable part. Cobalt and zinc are more distributed in the different fractions than arsenic. Geogenic and anthropogenic contributions were revealed by the study. Graphical Abstract .

Spatial variations of Carbon Monoxide (CO) are examined in the urban environment of Ouagadougou, Burkina Faso. Focus is given on the variations between urban background, roadside and in-traffic measurements. Results show significant differences between the three methods where average in-traffic values were 2-3 times higher than average roadside values and 10-12 times higher than average background values. During traffic congestions these differences extended up to 6 and 20 times respectively. Results are discussed in relation to human exposure assessments and WHO guidelines.

The construction of a subsurface dam and/or physical cutoff barriers is one of the most known techniques used to prevent seawater intrusion during excessive exploitation of freshwater from a coastal aquifer. This method is widely used in many sites around the world (Japan, Brazil, India, Burkina Faso…). In this study, we present an innovative technique for constructing subsurface barriers based on geochemical reactions. A calcite cutoff wall is developed by mixing two aqueous solutions Na₂CO₃ and CaCl₂ under pCO₂ equal to 3.16·10⁻⁴ bar. The deposition of calcite in the mixing zone induces a high clogging, which greatly reduces the porosity and then the permeability of the aquifer into the injection zone. We use GEODENS code to study the effect of a developed geochemical cutoff wall on saltwater intrusion and to assess their protective effect on preventing seawater intrusion. The GEODENS code can solve these equations by a finite element procedure; it can handle density-dependent flow, transport, and geochemical reactions in porous media. The effect of depth and location of the geochemical cutoff wall is tested and results showed a significant reduction of seawater intrusion penetration length. According to the budget used in many barrier construction projects, we have shown that the developed geochemical cutoff wall presented in this work could produce a lower seawater intrusion penetration length than the traditionally used barriers at a very lower cost.

Low-quality water such as sodic alkaline industrial wastewater is often used to irrigate crops of intensively managed urban gardening systems in the semi-arid tropics to help meet the fresh food demands of a rapidly increasing city population. An on-farm experiment was established to examine the effects of sodium (Na) and bicarbonate (HCO₃₋)-loaded industrial wastewater on soil and crops on the one hand, and to determine melioration effects on soil condition and plant development on the other hand. To ameliorate the sodified soil, fine-powdered gypsum (CaSO₄) was applied as soil amendment onto the upper soil (0–20 cm) before sowing of crops. Depending on soil pH and exchangeable sodium percentage (ESP), which reflected the level of soil degradation (SDL), two different amounts of gypsum were applied: 6.8 t ha⁻¹ in moderate and 10 t ha⁻¹ in high SDL plots. Subsequently rainfed maize (Zea mays L.) and irrigated spinach (Spinacia oleracea L.) under two irrigation water qualities (clean and wastewater) were cultivated. Chemical and physical soil parameters, as well as plant root density (RLD), crop yield and concentrations of major plant nutrients and Na were determined. The results showed that gypsum application reduced soil pH on average below 8 and reduced ESP below 18%. Furthermore, gypsum-treated soils showed a significant reduction of sodium absorption rate (SAR) from 14.0 to 7.9 and aggregate stability was increased from 44.2 to 51.2%. This in return diminished Na concentration in plant tissues up to 80% and significantly increased RLD of maize. Overall, calcium (Ca) addition through the gypsum amendment changed the soil cation balance by increasing the Ca:Mg ratio from 3.5 to 7.8, which likely influenced the complex interactions between competing cations at the exchange surfaces of the soil and cation uptake by plant roots.

In Burkina Faso where cooking with biomass is very common, little information exists regarding kitchen characteristics and their impact on air pollutant levels. The measurement of air pollutants such as respirable particulate matter (PM₁₀), an important component of biomass smoke that has been linked to adverse health outcomes, can also pose challenges in terms of cost and the type of equipment needed. Carbon monoxide could potentially be a more economical and simpler measure of air pollution. The focus of this study was to first assess the association of kitchen characteristics with measured PM₁₀and CO levels and second, the relationship of PM₁₀with CO concentrations, across these different kitchen characteristics in households in Nouna, Burkina Faso. Twenty-four-hour concentrations of PM₁₀(area) were measured with portable monitors and CO (area and personal) estimated using color dosimeter tubes. Data on kitchen characteristics were collected through surveys. Most households used both wood and charcoal burned in three-stone and charcoal stoves. Mean outdoor kitchen PM₁₀levels were relatively high (774 μg/m³, 95 % CI 329–1,218 μg/m³), but lower than indoor concentrations (Satterthwaite t value, −6.14; p < 0.0001). In multivariable analyses, outdoor kitchens were negatively associated with PM₁₀(OR = 0.06, 95 % CI 0.02–0.16, p value <0.0001) and CO (OR = 0.03, 95 % CI 0.01–0.11, p value <0.0001) concentrations. Strong area PM₁₀and area CO correlations were found with indoor kitchens (Spearman’s r = 0.82, p < 0.0001), indoor stove use (Spearman’s r = 0.82, p < 0.0001), and the presence of a smoker in the household (Spearman’s r = 0.83, p < 0.0001). Weak correlations between area PM₁₀and personal CO levels were observed with three-stone (Spearman’s r = 0.23, p = 0.008) and improved stoves (Spearman’s r = 0.34, p = 0.003). This indicates that the extensive use of biomass fuels and multiple stove types for cooking still produce relatively high levels of exposure, even outdoors, suggesting that both fuel subsidies and stove improvement programs are likely necessary to address this problem. These findings also indicate that area CO color dosimeter tubes could be a useful measure of area PM₁₀concentrations when levels are influenced by strong emission sources or when used in indoors. The weaker correlation observed between area PM₁₀and personal CO levels suggests that area exposures are not as useful as proxies for personal exposures, which can vary widely from those recorded by stationary monitors.

This study examined the long-term effects of the landfill disposal of untreated urban waste for soil fertilization on the prevalence and antibiotic resistance profiles of various human opportunistic pathogens in soils from Burkina Faso. Samples were collected at three sites in the periphery of Ouagadougou during two campaigns in 2008 and 2011. At each site, amendment led to changes in physico-chemical characteristics as shown by the increase in pH, CEC, total C, total N, and metal contents. Similarly, the numbers of total heterotrophic bacteria were higher in the amended fields than in the control ones. No sanitation indicators, i.e., coliforms, Staphylococci, and Enterococci, were detected. Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) were detected at a low level in one amended field. Stenotrophomonas maltophilia was detected from both campaigns at the three sites in the amended fields and only once in an unamended field. Diversity analysis showed some opportunistic pathogen isolates to be closely related to reference clinical strains responsible for nosocomial- or community-acquired infections in Northern countries. Antibiotic resistance tests showed that P. aeruginosa and Bcc isolates had a wild-type phenotype and that most S. maltophilia isolates had a multi-drug resistance profile with resistance to 7 to 15 antibiotics. Then we were able to show that amendment led to an increase of some human opportunistic pathogens including multi-drug resistant isolates. Although the application of untreated urban waste increases both soil organic matter content and therefore soil fertility, the consequences of this practice on human health should be considered.