Heavy metal and bacteria contamination of selected wetland ecosystems on the eastern slope of Mount Cameroon: implications for human and ecosystem health

Abstract

The wetland ecosystems on Mount Cameroon’s eastern slope, known for their agroecological significance and biodiversity, are facing potential threats such as heavy metal and bacterial contamination due to poor waste management systems and anthropogenic activities. A study was conducted to quantify the heavy metals and bacterial loads in Solanum scabrum Mill., Amaranthus cruentus L., and Talinum fruticosum (L.) Juss., three major vegetables grown in the area. Soil and water samples were collected and analysed for the concentrations of 24 elements, including heavy metals, using the inductively coupled plasma-mass spectrometry (ICP-MS) approach. The bacteria in the samples were isolated and cultured in lactose broth, and the total coliform count was estimated using the maximum probable number (MPN) technique. The heavy metals in both soil and plant samples occurred in the order Mn > Zn > Cr > Ni > Cu > Co > Pb > Fe > Al. The contamination indices of Mn > 5807.3 and Cr > 4698.3 indicated varied sources of these metal contaminants. The bioaccumulation coefficient (BAC) was > 1 for most of the metals, with T. fruticosum having the highest BAC value (3.60) for the leaves. The mean bacteria count indicated high contamination with Enterobacteria (600 coliform forming units (CFU)) and E. coli (500 CFU) in vegetables across all sampling sites. The high concentration of bacterial contaminants in the soil, water, and plants across the study sites indicates a high health risk, making the ecosystem not pristine and thus impossible for these wetlands to improve food security. Consequently, this study provides crucial information for policymakers and stakeholders to develop effective strategies for the conservation and sustainable management of these wetlands.