Heavy Metals Contents of Municipal Solid Waste Dumpsites in Potiskum, Yobe State Nigeria

The concentrations of As, Cd, Cr, Cu, Ni, Pb, Fe and Zn in selected dumpsites in Potiskum were determined with Buck Scientific 210VGB Atomic Absorption Spectrometer (AAS) AVG 210. One-way ANOVA was deployed at p < 0.05 level of significance for obtained triplicate values. It was found that the concentration (mg·kg-1) of studied heavy metals in Potiskum dumpsites ranged from 0.108 ± 0.02 - 262.536 ± 0.68 with pattern of accumulation Pb (262.536 ± 0.02) > Zn (183.369 ± 0.58) > Fe (159.453 ± 0.50) > Cu (111.382 ± 0.62) > Cr (43.523 ± 0.36) > Ni (6.419 ± 0.26) > Cd (0.679 ± 0.01) > As (0.108 ± 0.02) mg·kg-1. The concentrations of As, Cr, Ni, Fe and Zn fell below the WHO standards while those of Pb, Cd and Cu were above set limits by WHO. High acidity corresponds markedly with high levels of Cd, Cu, Cr and Zn and requires urgent attention as this trend is capable of groundwater contamination that will cause public health concern in affected areas.

Mechanical and environmental properties of geopolymer-stabilized domestic waste incineration slag in an asphalt pavement base

Domestic waste incineration slag(WIS)includes fly ash and slag.Fly ash is classified as hazardous waste because it contains heavy metals.Most of slag are directly stacked or landfilled due to problems such as large output and low utilization rate.Harmless treatment is imminent.If WIS is used effectively in the road engineering,which can realize the high-quality and high-efficiency recycling of WIS,and it is of great significance to save resources and protect the environment.This study applies a geopolymer prepared from WIS fly ash as a stabilizing agent in WIS blending macadam for use as a pavement base mixture,and reports the mechanical properties(unconfined compressive strength,splitting strength,and resilience modulus)of the geopolymer-stabilized WIS blending macadam(GeoWIS).The leaching concentrations of harmful heavy metals of GeoWIS soaked in water were also investigated.Finally,the strength formation and heavy metal stability mechanisms were explored.The unconfined compressive strength,splitting strength,and compressive resilient modulus of GeoWIS all increased with increasing geopolymer content and decreasing WIS content.The strength of GeoWIS was derived from its geopolymerization and hydration products(C-S-H gel,N-A-S-H gel,and AFt).When the geopolymer content reached 12%–14%,the GeoWIS without natural macadam met the strength criterion of the asphalt pavement base.Through physical adsorption and chemical bonding,the geopolymer significantly reduced the leaching of harmful heavy metals.In GeoWIS with 50%WIS and stabilized with 10%geopolymer,the Cr,Ni,Cd,and Pb concentrations met the grade III groundwater standard.Concentrations of heavy metals leached from GeoWIS are low and exert little impact on environment.

Feasibility of Estimating Heavy Metal Contaminations in Floodplain Soils Using Laboratory-Based Hyperspectral Data—A Case Study Along Le’an River, China

It is necessary to estimate heavy metal concentrations within soils for understanding heavy metal contaminations and for keeping the sustainable developments of ecosystems.This study,with the floodplain along Le'an River and its two branches in Jiangxi Province of China as a case study,aimed to explore the feasibility of estimating concentrations of heavy metal lead(Pb),copper(Cu) and zinc(Zn) within soils using laboratory-based hyperspectral data.Thirty soil samples were collected,and their hyperspectral data,soil organic matters and Pb,Cu and Zn concentrations were measured in the laboratory.The potential relations among hyperspectral data,soil organic matter and Pb,Cu and Zn concentrations were explored and further used to estimate Pb,Cu and Zn concentrations from hyperspectral data with soil organic matter as a bridge.The results showed that the ratio of the first-order derivatives of spectral absorbance at wavelengths 624 and 564 nm could explain 52% of the variation of soil organic matter;the soil organic matter could ex-plain 59%,51% and 50% of the variation of Pb,Cu and Zn concentrations with estimated standard errors of 1.41,48.27 and 45.15 mg·kg-1;and the absolute estimation errors were 8%-56%,12%-118% and 2%-22%,and 50%,67% and 100% of them were less than 25% for Pb,Cu and Zn concentration estimations.We concluded that the laboratory-based hyperspectral data hold potentials in esti-mating concentrations of heavy metal Pb,Cu and Zn in soils.More sampling points or other potential linear and non-linear regression methods should be used for improving the stabilities and accuracies of the estimation models.

Assessment of Municipal Organic Solid Waste, as a Potential Feedstock for Briquette Production in Kampala, Uganda

The current shortage of energy resources coupled with environmental degradation problems resulting from deforestation in Uganda has contributed to increased demand for renewable energy resources including municipal organic solid waste and agricultural residues. However, organic waste from Municipal Solid Waste (MSW) may contain contaminants that are harmful to public health and the environment. This study determined the heavy metal concentration in MSW in Kampala City, Uganda. Also, the physicochemical properties of briquettes produced from the MSW were compared with charcoal. The waste samples were collected from residential, institutional and market areas over a period of two weeks. They were then analyzed for the presence of heavy metals. Briquettes were made from the bio-waste and were subjected to calorific and proximate analysis. Results indicated that the mean concentrations of Cd, Cr, Cu, Fe, and Pb were 1.25 mg/kg, 2.04 mg/kg, 38.2 mg/kg, 3.97 mg/kg and 1.99 mg/kg respectively while Hg was not detected. The calorific values of briquettes ranged from 8.9 to 15.3 MJ/kg and were lower than those of charcoal. Heavy metal concentrations in bio-waste collected were below the permissible acceptable limits. These findings indicate that the sampled MSW does not pose a health hazard arising from the presence of such heavy metals and therefore could be a safe source of renewable energy.