Assessment of Heavy Metal Contamination and Potential Ecological Risk in Water and River Sediments from Moboma Artisanal Gold Mining Sites in Southwest Central African Republic

Gildas DOYEMET^{1, 2,} , Barthel Primael KOGUENGBA KOGBO², Oscar ALLAHDIN², Baghdad OUDDANE¹, Eric FOTO² and Michel WARTEL¹

¹Laboratoire Avancé de Spectroscopie Pour les Interactions, la Réactivité et l’Environnement, Université de Lille, CNRS, UMR 8516—LASIRE, 59000 Lille, France

²Chaire Unesco «Sur la gestion de l’eau», Laboratoire Hydrosciences Lavoisier, Faculté des Sciences, Université de Bangui, Bangui 908, Central African Republic

Cite this paper:
Gildas DOYEMET, Barthel Primael KOGUENGBA KOGBO, Oscar ALLAHDIN, Baghdad OUDDANE, Eric FOTO and Michel WARTEL. Assessment of Heavy Metal Contamination and Potential Ecological Risk in Water and River Sediments from Moboma Artisanal Gold Mining Sites in Southwest Central African Republic. American Journal of Water Resources. 2025; 13(2):19-25. doi: 10.12691/ajwr-13-2-1

Abstract

The study revealed high concentrations of cadmium (Cd), mercury (Hg) and uranium (U) in the tributary streams of the Lobaye river in the Moboma region. The results of mathematical models of sediment contamination suggest that anthropogenic activities may be the main sources of heavy metal pollution, which may come from gold mining activities. All the watercourses present a considerable ecological risk index. The effects of this pollution are devastating. Heavy metals, such as mercury, accumulate in sediments and bioaccumulate in the food chain, affecting not only aquatic fauna, but also the human communities that depend on these resources for their livelihood. The contamination of water resources by gold mining calls for effective decontamination solutions. Among the techniques available, media filtration, in particular the use of zeolite bricks, stands out as an inexpensive option that can be easily adapted to the CAR. Thanks to their porous structure and ion exchange properties, these local materials effectively trap heavy metals such as mercury, lead and others. This simple, cost-effective filtration system offers a sustainable alternative to costly chemical methods. By incorporating this technology, local communities can reduce the toxicity of their water resources while minimising environmental impacts.

Keywords:
gold panning contamination water sediment Moboma

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References:

[1]	APP. (2013). Equité et Industries Extractives en Afrique Pour une gestion au service de tous [Rapport sur les progrès en Afrique], 120p.
[2]	Ouedraogo, L. (2019). Orpaillage artisanal et développement rural [Thèse]. Université de Laval, Canada, 152p.
[3]	C.M. Dipakama, N. Watha-Ndoudy, J. Nzila, I. Nguelet, V. Kimpouni .Impact de l’exploitation artisanale de l’or sur l’environnement dans le secteur de Dimonika (Massif forestier du Mayombe, Congo).
[4]	O. BAMBA, S. PELEDE, A. SAKO, N. KAGAMBEGA, M. Y. W. MININGOU .impact de l’artisanat minier sur les sols d’un environnement agricole aménage au Burkina Faso. Journal des Sciences. /J. Sci. Vol. 13, N° 1 (Octobre 2013) 1-11.
[5]	Lucas Moses Kouadio, 2023. Contribution à l’évaluation des niveaux de contamination des eaux et des sols des sites d’orpaillage clandestin et élimination des métaux (Hg, Pb, Cd) et de l’arsenic des eaux polluées, à l’aide des argiles de Côte d’Ivoire - Archive ouverte HAL.
[6]	G. Y. Hadzi, D. K. Essumang, G. A. Ayoko. Assessment of contamination and potential ecological risks of heavy metals in riverine sediments from gold mining and pristine areas in Ghana. Journal of Trace Elements and Minerals 7 (2024) 100109.
[7]	H.A. Kyowe, O.O. Awotoye, J.A.O. Oyekunle, J.A. Olusola. Index of heavy metal pollution and health risk assessment with respect to artisanal gold mining operations in Ibodi-Ijesa, Southwest Nigeria. Journal of Trace Elements and Minerals 9 (2024) 100160.
[8]	A. A. Surour, M. M. El Desouky, M. M. Ismail, R. A. Aissa H. Zaghloul a Gold mineralization and environmental impacts of artisanal mining in the Um Araka area, Egypt: Microanalyses and heavy metals assessment. Journal of African Earth Sciences 223 (2025) 105519.
[9]	A. Jaillon, G. de Brier, Cartographie des sites miniers artisanaux dans l’ouest de la Centrafrique, IPIS, novembre 2019.
[10]	K. McCourt, G. Sautter, S.L. Estes, C. McMahan, C. Lee, E.R. Carraway, I. Vélez-Torres, D. Vanegas. Participatory assessment of pollution and health risk in artisanal and small-scale gold mining communities in Colombia. GroundwaterforSustainableDevelopment25(2024)101158.
[11]	Stambuk-Giljanovic. N.. 1999. Water quality evaluation by index in Dalmatia. Water Resour. 33. 3423–3440.
[12]	Yidana. S.M.. Yidana. A.. 2010. Assessing water quality using water quality index and multivariate analysis. Environ. Earth Sci. 59 (7). 1461–1473.
[13]	Varol. S.. Davraz. A.. 2015. Evaluation of the groundwater quality with WQI (Water Quality Index) and multivariate analysis: a case study of the Tefenni plain (Burdur/ Turkey). Environ. Earth Sci. 73. 1725–1744.
[14]	Sener. S.. Sener. E.. Davraz. A.. 2017. Evaluation of water quality using water quality index (WQI) method and GIS in Aksu River (SW-Turkey). Sci. Total Environ. 584–585. 131–144.
[15]	M. N. Ayiwouo . F. N. Yamgouot. L. L. N. Mambou. S. T. Kingni. I. Ngounouno. Impact of gold mining on the water quality of the lom river. Gankombol. Cameroon. Heliyon 8 (2022) e12452
[16]	Müller G. Die Schwermetallbelastung der Sedimente des Neckars und seiner Nebenflusse: eine Bestandsaufnahme. Chemiker Zeitung 1981; 105: 157164.
[17]	Ruiz F. Trace Metals in Estuarine Sediments from the Southwestern Spanish Coast. Marine Pollution Bulletin 2001; 42: 481489.
[18]	Sainz A, Ruiz F. Influence of the very polluted inputs of the TintoOdiel system on the adjacent littoral sediments of southwestern spain: A statistical approach. Chemosphere 2006; 62: 16121622.
[19]	Turner A, Millward GE. Suspended particles: their role in estuarine biogeochemical cycles. Estuarine, Coastal and Shelf Science 2002; 55: 857883.
[20]	Williams J.A., Antoine J. Evaluation of the elemental pollution status of Jamaican surface sediments using enrichment factor, geoaccumulation index, ecological risk and potential ecological risk index.
[21]	Kim B. S. M, Angeli J. L. F., Ferreira P. A. L., Michaelovich de Mahiques M., Figueira R C. L. Critical evaluation of different methods to calculate the Geoaccumulation Index for environmental studies: A new approach for Baixada Santista Southeastern Brazil.
[22]	Ruiz F. Trace Metals in Estuarine Sediments from the Southwestern Spanish Coast. Marine Pollution Bulletin 2001; 42: 481489.
[23]	Ryan J.D., Windom H.L. A geochemical and statistical approach for assessing metal pollution in coastal sediments. Metals in Coastal Environments of Latin America. Springer, Berlin Heidelberg, 1988; 47–58.
[24]	Sinex S.A., Wright D.A. Distribution of trace metals in the sediments and biota of Chesapake Bay. Marine Pollution Bulletin, 1988; 19: 425–431.
[25]	Emmerson R.H.C., O'Reilly-Wiese S.B., Macleod C.L., Lester J.N. A multivariate assessment of metal distribution in intertidal sediments of the Blackwater Estuary, UK. Marine Pollution Bulletin, 1997; 34: 960– 968.
[26]	Emmerson R.H.C., O'Reilly-Wiese S.B., Macleod C.L., Lester J.N. A multivariate assessment of metal distribution in intertidal sediments of the Blackwater Estuary, UK. Marine Pollution Bulletin, 1997; 34: 960– 968.
[27]	Hakanson. L. An ecological risk index for aquatic pollution control.a sedimentological approach. Water Reseach. Volume 14, Issue 8, 1980, Pages 975-1001.
[28]	Ma, J., Han, C., Jiang, Y., 2020. Some problems in the application of potential ecological risk index. Geogr. Res. 39 (6), 1233–1241.
[29]	J. GAILLARDET, B. DUPRE, and C. J. ALLEGRE. A global geochemical mass budget applied to the Congo Basin rivers: Erosion rates and continental crust composition. 0016-7037(95)00230-8. Geochimica et Cosmochimica Acta, Vol. 59, No. 17, pp. 3469-3485, 1995.
[30]	Taylor, S.R., 1964. Abundance of chemical elements in the continental crust: a new table. Geochim. Cosmochim. Acta 28 (8), 1273–1285.