Application of pollution assessment models in soil contaminated by heavy metals in two steel rods markets, Port Harcourt, Rivers State, Nigeria

Soil samples were collected at a depth of 0-30cm within two steel markets and a control site in Port Harcourt, Rivers State Nigeria to assess the level of heavy metals (Fe, Pb, Cu, Cd, Cr, Ni and As) in the environment. Atomic Adsorption Spectrophotometer was used to analyze the samples for heavy metals. The concentrations of all the heavy metals in the steel rods markets exceeded that of the control. The results indicated that heavy metals concentrations in the sites were in the order; Mile III > Kala > RSU. The average levels of contamination of heavy metals recorded followed the order Fe > Cr > Cu > Pb > Ni > As > Cd in Mile III, Fe > Pb > Cu > Cr > Ni > As > Cd in Kala and Fe > Cu > Pb > Cr > Ni > As > Cd in RSU (control). Mean concentrations obtained for heavy metals within the months of investigation were; 1420.931±9.155, 7.753±0.184, 8.730±0.050, 2.843±0.124, 9.428±0.122, 7.433±0.047 and 3.732±0.047 mg/Kg for Fe, Pb, Cu, Cd, Cr, Ni and As respectively at the mile III station, while the mean concentrations of heavy metals observed at the Kala station were; 1161.173±1.823, 9.425±0.054, 7.596±0.027, 1.425±0.020, 6.507±0.006, 5.455±0.033 and 1.901±0.010 mg/Kg for Fe, Pb, Cu, Cd, Cr, Ni and As respectively. The mean values of heavy metals concentrations observed at the RSU station within the period were; 892.064±1.025,5.603±0.007, 5.841±0.051, 0.173±0.005, 3.389±0.009, 2.309±0.010 and 0.706±0.006 mg/Kg for Fe, Pb, Cu, Cd, Cr, Ni and As respectively. Pollution assessment models used for assessing the anthropogenic input on the quality of the soil in the area using the control site as the basis of judgment were: contamination factor (CF), pollution load index (PLI), contamination degree (CD), modified contamination degree (mCD), potential ecological risk coefficient (Eir), potential ecological risk index (RI), Geo-accumulation index (Igeo) and anthropogenicity. These indices revealed that the steel markets were contaminated and polluted and poses ecological risks by heavy metals, even though the values obtained were still below the WHO acceptable limits. The steel rods markets need to be adequately monitored and regulated to avoid further soil contamination by heavy metals to a degree that will be dangerous to human health.

Heavy Metal Contamination and Ecological Risk Assessment of Overlying Water and Sediments of Nkozoa Lake (Southern Cameroon)

Examination of heavy metals (Cr, Cu, Zn, Pb, Hg, Cd and Ni) in overlying water and sediments was conducted in Lake Nkozoa, in a peripheral area of Yaoundé characterized by a high population density and rapid economic development in Cameroon. Sediment samples were collected at the entrance and near the center of the lake, using a raft and polyvinyl chloride (PVC) pipes. They were subjected to water quality parameters, heavy metals comparisons and calculations of pollution indices and ecological risks followed by statistical analysis in order to identify and estimate the sources of metal contamination in overlying water and sediments of the Nkozoa Lake. The physico-chemical parameters of water show that the pH (5 < pH < 6), total dissolved solids (TDS~130 g/L) and conductivity (EC~194.8 µs/cm) are below the recommendations of the WHO. The average heavy metal concentrations in sediments, except Cd, are lower than the upper continental crust (UCC) and several environmental contamination monitoring parameters, such as threshold effect level (TEL), probable effect level (PEL), and severe effect level (SEL). The sediment samples show a low heavy metal contamination degree (class 0) and low potential ecological risk (PER) level, except for Cd and Hg which have high contamination degree (class 1 to 6) and moderate PER. Matrix correlation shows that some parameters like pH, EC, Cr and TDS, Cu, Hg in water have perfect positive correlations (r = 1.00) suggesting common sources of contamination. Cluster analyses coupled with matrix data for sediments revealed that Cd is the most contaminant elements derived from anthropogenic sources.

Seasonal assessment of drinking water sources in Rwanda using GIS, contamination degree (Cd), and metal index (MI)

The quality of drinking water source remains as a major concern in areas of developing and underdeveloped countries worldwide. The treatment and supply of drinking water in Rwanda are carried out by Water and Sanitation Corporation, a state-owned public company. However, it is not able to supply water to all households. Consequently, the non-serviced households depend on natural water sources, like springs, to meet their water requirements. Nevertheless, the water quality in these springs is scarcely known. Therefore, this study assessed and compared metal elements in drinking water sources in the dry and rainy seasons in 2017 using the contamination degree, metal index, and geographic information systems to reveal the spatial distribution of water quality within the considered water sources of springs in Rwanda. The samples were collected monthly from nine water sources of springs and the measured elements are aluminium, calcium, copper, iron, manganese, and zinc. The metal index indicated that during the dry season and rainy season, the sites of Kibungo (1.10 and 1.26) and Kinigi (1.01 and 1.54) have assessed a metal index which is higher than 1. Thus, the water quality of those sites was getting the threshold of warning. The analysis indicated that pollutants are easily transported into water bodies during the rainy season in urban and rural areas to a greater extent than during the dry season .