This current study focused on heavy metal and bacteria contamination of selected wetland ecosystems on the eastern slope of mount cameroon and its implications for human and ecosystem health. Across the research region, heavy metal concentrations were found to be higher in the stems and roots (non-edible portions) of the vegetables compared to the leaves (edible part) of all the plant species. The rapid loss of water by transpiration at the leaf level may be to blame for this phenomenon. Alternatively, heavy metals might be more volatilized off the leaf surface due to high transpiration rates, resulting in a lower concentration. This agrees with research by Warner (1993) and Zhou et al. (2016) that found a greater concentration of heavy metals in plant roots compared to leaves and even lower concentrations in fruits and seeds. Differences in the morpho-physiological traits of T. fruticosum, S. scabrum, and A. cruentus plants may account for the observed discrepancy in bioaccumulation potentials amongst the three vegetable kinds. T. fruticosum's capacity to bioaccumulate heavy metals may be attributable, in part, to its noticeably thicker and succulent tissues compared to the other two vegetables. In other investigations, other researchers have also found similar outcomes. Plant species, intrinsic control, and soil quality are the three most important factors in determining element absorption (Chunilall et al. 2005). Concurrently, Farooq et al. (2008) also found that... Along with soil and climate, numerous other factors influence metal accumulation and bioavailability. These include, but are not limited to, plant genotype, agronomic management principles (such as active/passive transfer processes, sequestration, and speciation), redox states, root system type, and plant response to elements related to seasonal cycles (Kabata-Pendias 2011).
One of the most important factors in metal absorption is soil quality. Metal availability for plant uptake is influenced by clay particles as well. The study found a substantial relationship between the plants' metal absorption capability and the physicochemical characteristics. This confirms what Ghosh and Singh (2005) found: that pH, metal concentration, cation exchange capacity, organic carbon content, and the system's oxidation state are the primary determinants of metal solubility in soils. Mbong et al. (2014) and Askoy et al. (2000) both found the same thing. Although trace levels of certain metals are necessary for plant metabolism, heavy metal pollution generally modifies the makeup and interactions of soil microbial communities, which in turn negatively affects plant growth, metabolism, and ecosystem health (Nagajyoti et al. 2010; Li et al. (2017). In comparison to previous research, this one found rather high average amounts of Pb, Cu, and Zn (Table 3). The typical amounts of lead, copper, and zinc in plants are 5, 10, and 100 mg Kg-1, as stated by Zu et al. (2004). Comparisons with the criteria established by Zu et al. (2004) are shown in Table 3. Compared to the lowest allowable limits set by the WHO/FAO (2007), the values found in this investigation were also much higher. Numerous more research using vegetables and other food crops have also documented the concentrations of these and other components. Table 2 provides a summary of the metal content in several plant kinds included in this investigation, as well as those reported by Odai et al. (2008) and Obiora et al. (2015). It also includes the lowest acceptable levels set by the EU (2023) and WHO/FAO (2007). Specifically, newborns are at increased risk of heavy metal exposure due to the severity and concentrations of soil pollution (Olawoyin et al. 2012).
Several variables, including pH, organic matter content, and plant type, might explain the high transfer factor (BAC values > 1) for the base metals Ni, Pb, Cu, and Zn at mile 16 and Musaka. Different land use practices and soil qualities in various places might explain the variations from one site to another. Finding BAC > 1 for certain elements in Amaranthus cruentus, particularly in its roots and stems, may suggest that plants have developed ways to phytoextract these metals from soil. Even though the levels measured in this investigation are elevated, in the same general area, Khan et al. (2010) found the same thing in the province of Northern Pakistan's volcanic and meta-sedimentary rock. In a similar vein, the findings are in agreement with those of Mahmood and Malik (2014) in the vicinity of Pakistani irrigation sites.
According to the results of the DIM and HRI analyses, the locals who eat these veggies might be putting themselves at serious risk from the presence of Mn, Zn, Cu, and Ni. All the human-made things that have happened in these regions might be to blame. These results are consistent with what Singh et al. (2010) predicted would happen due to Pb and Cd exposure in India's tropical regions. Consistent with the anthropogenic factors, we find a pattern that agrees with Ngole-Jeme's (2016) conclusions about heavy metal contamination in soils along Cameroon's unpaved roads. These roads are high-traffic areas, which increases the risk of long-term exposure for road users, and the risks are moderate to high. The gold mining sites in Ghana's Western District were found to have a significant risk of lead, cadmium, nickel, copper, and zinc, according to research by Musah et al. (2013).
The research region often has a high total coliform burden. Despite their lack of pathogenicity, coliform bacteria are good markers for the presence of other pathogens. There is clear evidence of human contamination from faeces since Salmonella typhi was found at every location. There was an effect of heavy metals on SRB presence (H2S- Salmonella), metal contamination sensitivity, and community structure. Wu et al. (2019) found a similar pattern in their study of mangrove sediments. This may be because these wetlands are used as a direct location for trash disposal and are located close to human settlements. Unfortunately, some people's toilets empty into these habitats, and even worse, some people just defecate in the water. When looking at the disposal of household garbage by communities surrounding Barombi Mbo Lake, Tabot et al. (2016) found similar outcomes.
At all of the research locations, E. coli, a bacterium that causes acute infection diarrhoea, was present in high concentrations. Other bacteria that cause disease include Vibrio, Salmonella, bacterial and parasitic dysentery, and E. coli. The global incidence and prevalence of illnesses can be attributed, primarily, to inadequate sanitation practices and the pollution of food and water sources (Khalid et al. 2013). The World Health Organisation (2007) and the World Bank HDN (2013) both agree that they are a leading cause of microbial pathogen contamination and, consequently, higher child death rates in poor nations.