Artisanal (illegal) mining has been reported to have environmental and health effects on the surrounding communities due to heavy metals pollution. The determination of total heavy metal concentration does not reflect the toxicity and bioavailability of the metals. Toxicity and bioavailability of the metals can be achieved by determining the form in which the metal exist in the environment (speciation). This present work evaluated the heavy metals’ {cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb), zinc (Zn) &nickel (Ni)} contamination and the form in which they exist at some mining sites in Mangu LGC, Plateau state, Nigeria. Aqua regia ((HCl + HNO3, 3:1 v/v) was used for total metal concentration while sequential extraction method was used to orderly determine the speciation of the heavy metals. The level of the heavy metals in the digested solutions were determined using Buck Scientific model 210VGP Atomic Absorption Spectrophotometer (AAS). The results divulged that the concentrations of the heavy metals were within the FEPA and WHO recommended permissible limit except Cd and Ni. The values of the metals at Mangu Halle mining site followed the sequence: Mn > Zn > Ni > Pb > Cu > Cd whereas the sequence at Alogwom was Mn > Zn > Pb > Ni > Cu > Cd. The results of the speciation indicated that all metals were bound to the five fractions with the residual fraction dominating except Cd which was bound mostly to the soluble and exchangeable fractions. It could be concluded that the presence of these heavy metals in the mobile fractions, indicate that they could be easily released to the environment from soil. Thus, they are also likely to cause toxicity in the environment. Proper monitoring of the mining activities in the communities was recommended.

When the mining process is not properly controlled, it can be a source of heavy metals pollution in the environment. The uptake of these heavy metals in edible parts of vegetables can be a direct source of the metals into the human food chain. This study assessed the concentrations of lead (Pb), manganese (Mn), zinc (Zn), copper (Cu), nickel (Ni) and chromium (Cr) in soil and vegetables obtained from nine (9) farms around mining sites in Mangu LGA. Concentrations of heavy metals in soil and vegetables were determined using atomic absorption spectrophotometer (AAS). The results revealed the concentrations of the heavy metals at the farms to be within the recommended maximum levels of world soils but were higher than their respective controls. This implies that the artisanal mining contributed to the increased values of these heavy metals in the environment. Also, the mean concentrations of the heavy metals at Mangu Halle mining site decreased in the order Mn > Zn > Cr > Cu > Ni > Pb > Cd whereas at Alogwom it decreased in the order Mn > Zn > Pb > Cu > Ni > Cr > Cd. The enrichment factor (EF) of the elements showed deficiency to minimum enrichment for all the heavy metals whereas the pollution index (PI) of the metals indicated very slight contamination to moderate pollution. The results of the heavy metals in the vegetables showed that the bioaccumulation of the metals followed a pattern: Zn > Cu > Pb > Cr > Cd > Ni. Levels of Cd, Pb and Ni in the vegetables were observed to be higher than the recommended limit for vegetables whereas Cu, Cr and Zn exhibited lower values than recommended standards. Thus, their consumption might pose health risk to consumers and therefore there is the need for proper monitoring of the illegal mining activities to reduce health risk and the extent of heavy metals contamination.

Wetlands provide several ecosystem services including carbon capture and storage, water filtration, nutrient cycling, and support agriculture among others. The biogeochemical process and decomposition parameters in ‘Fadama' wetland soils comprising of Gada biyu, Pwomol and Kpang referred to as sites A, B, and C respectively all of Heipang District in Barkin Ladi, Plateau State was investigated using standard operating procedures (SOP). Results of investigations revealed that soils from Kpang had slightly higher water content (34.52%) than those from Pwomol (33.48%) and Gada biyu (32.03%). While soils from Gada biyu had the highest solid organic matter (SOM) (10.79%) followed by Pwomol (8.15%) as Kpang had the least (7.85%). Gada biyu soils had the lowest Phenol oxidases activity (1536.56 nmol dicq g-1 h-1) while those from Pwomol (5340.44 nmol dicq g-1 h-1) was highest. All sites had similar concentrations of soil phenolics (76.58 µg g-1, 79.98µg g-1, and 83.25µg g-1). The activity of hydrolyses (β-glucosidase) in Gada biyu soil (2.93 nmol g-1 min-1) was lower than those from Pwomol (6.13 nmol g-1 min-1). These parameters indicate the level of biogeochemical processes in the soil at each site. Gada biyu had the highest rate of CH4 (0.84 ug g-1h-1) flux. Decomposition of organic matter, carbon cycling and greenhouse gas storage in wetland soil, is due to the anoxic condition comprising of low oxygen availability, cool temperatures, anaerobic conditions, reduced microbial activity, and the quality of organic matter substrates in such soils.  Anthropogenic disturbances affecting wetlands must be discouraged to promote vital ecosystem services.