4^th European Chemistry Congress

Biography

Biography: J.C.Nnaji

Abstract

Physico-chemical parameters and heavy metals (Cd, Cr, Hg and Pb) concentrations were determined in wastewater, sediment and soils collected from Nassarawa-Kainji artisanal gold processing area. Gold bearing rocks excavated from other areas within Mashegu and Borgu LGAs are brought to Nasarawa-Kainji for crushing, grinding, washing and extraction of gold. Soil samples were collected from ten randomly selected washing pond sites. Soil from about 1 km away from the ponds area were collected as the control soil. Physico-chemical parameters of water, soil and sediments were analyzed using standard methods while heavy metal concentrations were determined after sample digestion with Varian AA240 Flame Atomic Absorption Spectrophotometer (FAAS). Hg was analyzed with the vapour generation accessory (Varian VGA 77) with closed end cell. Mean values for wastewater parameters were; temperature 28.06±0.99 °C, pH was 6.62±0.76, electrical conductivity (EC) 554.00±164.19 µScm^-1, total solids 1142.55 ±378.06 mg/L, total dissolved solids 409.59±118.87, turbidity 20.3±6.93 NTU, dissolved oxygen 4.46±0.84 mg/L, hardness 147.41±38.74 mg/L and alkalinity 92.40±39.58 mgCaCO₃/L. Mean nitrate, phosphate and chloride contents were 2.35±0.57, 1.03±0.45 and 2.39 ±0.69 mg/L, respectively. Mean values for sediment parameters were; pH 6.80±0.73, EC 214.60±48.81µScm^{- 1}, organic matter (OM) 1.10±0.25 %, total nitrogen (TN) 0.93 ±0.38 mg/kg, nitrate 0.63±0.29 mg/kg, total phosphorus (TP) 1.83 ±0.85 mg/kg and available phosphorus (AP) 1.22 ±0.49 mg/kg. Mean pH in soil samples from both the grinding section (GS) and washing section (WS) were similar (P > 0.05) but mean EC in the WS was significantly higher (P < 0.05) than in the GS. However, mean OM content was significantly higher (P < 0.05) in the GS than in the WS.  Mean TP and AP in GS were also significantly higher in the GS than in the WS. There were no significant differences (P > 0.05) in mean TN and nitrate concentrations in both sections. Mean Cd, Cr, Hg and Pb concentrations in the wastewater samples were 0.510±0.436, 0.523 ±0.295, 0.509±0.671 and 1.357±0.868 mg/L, respectively while mean concentrations in the sediment samples were Cd 1.065±0.765, Cr 1.084±0.476, Hg 1.611±1.463 and Pb 4.675±3.138 mg/L. Mean total metal concentrations Soil samples from Grinding Section (GS) were Cd 0.784±0.332, Cr 21.912±7.667, Hg 4.669±2.082 and Pb 83.188±63.926 mg/kg. In the washing section, mean Cd, Cr, Hg and Pb concentrations in soil samples were 0.854±0.347, 35.82±12.134, 7.210±2.649 and 70.219±38.778 mg/kg, respectively. Mean total metal concentrations control soil sample were Cd 0.159±0.084, Cr 2.140±0.805, Hg 0.071±0.022 and Pb 7.560 ±2.819 mg/kg. Concentrations of Cr, Pb and Hg were significantly higher (P<0.05) in soil samples than in wastewater and sediment samples. Results suggest substantial metal enrichment in soil samples due to gold ore processing and there is urgent need for the regulation of mining activities in the area.