Research Article
Physico-chemical and Bacteriological Characterization of Surface Waters in the City of Dolisie, Republic of Congo
Nicole Prisca Makaya Dangui Nieko*,
Jean de Dieu Nzila,
Tarcisse Baloki Ngoulou,
Emerson Maganga,
Doria Moise Kaya-Ongoto,
Faly Armel Soloka Mabika,
Etienne Nguimbi
Issue:
Volume 14, Issue 1, February 2026
Pages:
1-10
Received:
14 November 2025
Accepted:
11 December 2025
Published:
19 January 2026
Abstract: Surface water quality in Dolisie (southwest of the Republic of Congo) is strongly impacted by human activities, particularly domestic wastewater discharge, agriculture, and livestock farming, leading to progressive degradation of water resources and posing risks to public health as well as domestic and agricultural uses. This study assessed water quality through analysis of physico-chemical and bacteriological parameters at several sites representative of domestic and agricultural areas. Physico-chemical analysis showed that pH ranged from 5.5 (Ninja Lake) to 9.9 (marsh near the Orthodox Church), with a mean of 6.58 ± 1.18. Water temperature varied from 25.36°C (upstream of the Loubomo River) to 28.5°C (Tahiti fish ponds), with an average of 26.83 ± 0.93°C. Electrical conductivity ranged from 115.66 to 315.33 µS/cm (mean 213.65 ± 73.18 µS/cm), while total dissolved solids (TDS) varied from 57 to 210.5 ppm (mean 112.52 ± 46.70 ppm). Three heavy metals were detected: cadmium (0.049–0.070 ppm, mean 0.057 ± 0.005 ppm), copper (0.0217–0.0509 ppm, mean 0.037 ± 0.010 ppm), and zinc (0.0004–0.00311 ppm, mean 0.004 ± 0.008 ppm). Microbiologically, total mesophilic aerobic flora (TMAF) ranged from 1,000 to 6,000 CFU/100mL (mean 3,333 ± 1,670), total coliforms from 69 to 193 CFU/100mL (mean 133 ± 43), and fecal coliforms from 32 to 102 CFU/100mL (mean 64 ± 21), exceeding WHO standards and indicating significant fecal contamination. Fecal streptococci ranged from 30 to 72 CFU/100mL, Staphylococcus spp. from 14 to 97 CFU/100mL, Salmonella from 40 to 110 CFU/100mL, Shigella from 19 to 77 CFU/100mL, and Pseudomonas aeruginosa from 15 to 62 CFU/100mL. Correlation analyses revealed significant relationships: temperature correlated with total coliforms (r = 0.69) and fecal coliforms (r = 0.63), electrical conductivity correlated with TDS (r = 0.91), and several bacterial groups showed positive correlations among themselves. Principal component analysis associated the F1 axis (42.24% of variance) with microbiological parameters and the F2 axis (20.7%) with physico-chemical parameters. These findings reveal progressive deterioration of surface water quality in Dolisie and emphasize the urgent need for sustainable management measures, public awareness, and wastewater control to preserve water resources and protect public health.
Abstract: Surface water quality in Dolisie (southwest of the Republic of Congo) is strongly impacted by human activities, particularly domestic wastewater discharge, agriculture, and livestock farming, leading to progressive degradation of water resources and posing risks to public health as well as domestic and agricultural uses. This study assessed water q...
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Research Article
Pilot Study to Assess the Contamination of Cottonseed Oil Produced in Mali by Organochlorine Pesticide Residues
Issue:
Volume 14, Issue 1, February 2026
Pages:
11-16
Received:
2 January 2026
Accepted:
13 January 2026
Published:
30 January 2026
DOI:
10.11648/j.ijema.20261401.12
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Abstract: In Mali, cotton cultivation generates large quantities of cottonseed, from which edible cottonseed oil is widely produced and consumed. As part of national food safety surveillance, sanitary standards and market authorization requirements are being strengthened, necessitating routine pesticide residue assessments. This study aimed to evaluate the presence and levels of organochlorine pesticide residues in cottonseed oil marketed in Mali. A total of 27 cottonseed oil samples from different processing units were collected and anonymized by coded labeling. Laboratory analyses were conducted at the Environmental Toxicology and Quality Control Laboratory (ETQCL). Pesticide residues were extracted using the laboratory’s standard liquid–liquid extraction protocol, and quantification was performed using gas chromatography equipped with an electron capture detector (GC-µECD). Given the persistence and bioaccumulation potential of organochlorines, the investigation focused on this class of pesticides. Results indicated that 62.95% of samples were free of the targeted organochlorine residues, while 37.05% contained detectable levels. Eight out of the ten pesticides screened were identified, with concentrations ranging from 0.046 to 0.501 mg/L. DDT recorded the highest level (0.501 mg/L), whereas dieldrin showed the lowest (0.046 mg/L). Several detected concentrations exceeded the Codex Alimentarius maximum residue limits for edible oils. These findings demonstrate potential health risks associated with the consumption of contaminated cottonseed oil. It is therefore recommended to enhance pesticide regulation in cotton production, promote safer pest management alternatives, and establish regular monitoring systems to ensure oil safety for consumers.
Abstract: In Mali, cotton cultivation generates large quantities of cottonseed, from which edible cottonseed oil is widely produced and consumed. As part of national food safety surveillance, sanitary standards and market authorization requirements are being strengthened, necessitating routine pesticide residue assessments. This study aimed to evaluate the p...
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Research Article
Quantifying Contributions of Biomass Burning to Air Quality in Africa
Issue:
Volume 14, Issue 1, February 2026
Pages:
17-30
Received:
24 December 2025
Accepted:
12 January 2026
Published:
31 January 2026
DOI:
10.11648/j.ijema.20261401.13
Downloads:
Views:
Abstract: One of the major sources of tropospheric ozone (O3) precursors such as nitrogen oxides (NOx), carbon monoxides (CO), and non-methane volatile organic compounds (NMVOCs) is biomass burning. The emissions from the burning not only affect air quality and climate locally, but also on a continental to hemispheric scales through long-range transport. We used NASA’s Global Modeling Initiative Chemistry and Transport Model (GMI-CTM), to quantify the changes in surface ozone over Northern Sub-Saharan Africa (NSSA: 0 – 20N, 20W – 55E), as triggered by biomass burning from different regions. During the winter months (i.e., January), most of the burning is concentrated in the NSSA region while in summer it shifts southward outside the NSSA region. Our analysis reveals that out of the total contribution to surface ozone from biomass burning emissions in the NSSA region, 92% is due to NSSA biomass burning while the remaining 8% is from outside the NSSA. In fact, most (~75%) of the 8% comes from outside the African continent because little to no biomass burning occurs in Africa outside of the NSSA region during this time of year. However, during the summer months (i.e., July), most of the contribution to NSSA surface ozone (96%) is due to burning from outside NSSA. Only 10% of the 96% comes from outside the African continent because during this time most of the burning is from outside the NSSA but within the African continent. In spring (i.e., April) approximately equal percentages of contributions come from within and outside the NSSA region.
Abstract: One of the major sources of tropospheric ozone (O3) precursors such as nitrogen oxides (NOx), carbon monoxides (CO), and non-methane volatile organic compounds (NMVOCs) is biomass burning. The emissions from the burning not only affect air quality and climate locally, but also on a continental to hemispheric scales through long-range transport. We ...
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,
Sissoko Aminata
