Assessments of the Ecological and Health Risks of Potentially Toxic Metals in the Topsoils of Different Land Uses: A Case Study in Peninsular Malaysia

Soil Risk Assessment in the Surrounding Area of Hulene-B Waste Dump, Maputo (Mozambique)

Soil contamination in areas close to unplanned dumpsites represents an increasing risk to the ecosystems and human health. This study aimed to evaluate soil quality in the area surrounding the Hulene-B waste dump, Maputo, Mozambique, and to estimate potential ecological and human health risks. A total of 71 surface soil samples were collected in the surrounding area of the dump, along with 10 samples in areas considered not impacted by the dump. Chemical and mineralogical analyses were performed using XRF and XRD. Quartz was the most abundant mineral phase, followed by feldspars, carbonates, clay minerals, and Fe oxides/hydroxides. Results showed a significant contribution to ecological degradation by PTE enrichment, ranked as Zn >> Cu > Cr > Zr > Pb > Ni > Mn. Carcinogenic risk for both children and adults was significant due to Pb soil content. Soil sample concentrations of Cr, Cu, Mn, Ni, Pb, Zn, and Zr, posing a risk especially in children, suggested the need for continuous monitoring, as well as the definition and implementation of mitigation measures.

High Ecological Health Risks of Potentially Toxic Metals in Polluted Drainage Sediments: Is There a Need for Public Concern during Flash Floods?

The present study aimed to investigate the concentrations of potentially toxic metals (PTMs) in the drainages, rivers, and coast of Malacca in Peninsular Malaysia. The ranges of total PTM concentrations (mg/kg dry weight) were 1.88–7.01 for Cd, 18.9–1689 for Cu, 26.0–850 for Ni, 56.5–307 for Pb, and 75.4–312 for Zn. Based on an ecological risk assessment and geochemical fractions, it was concluded that heavy metals pollute the drainages and the Malacca River. The potential ecological risk index (PERI) categorised the drainage and river sites as a “very high ecological risk”. Therefore, it was shown that elevated levels of PTMs in the drainages near Malacca Industrial Area and in the Malacca River sediment were most probably attributed to untreated (or incomplete treatment of) industrial effluents. The drainage sediments were found to have higher hazard quotient (HQ) values for the three pathways of the PTMs for children and adults. Although in general, the non-carcinogenic risks of the PTMs for children and adults indicated no significant detrimental health effects, the hazard index (HI) for Pb in children at drainage locations surpassed 1.0, suggesting a non-carcinogenic risk (NCR), which is a cause for worry. Consequently, the ecological health risk assessments offered critical information for PTM pollution reduction and environmental management in future sustainable development initiatives in Peninsular Malaysia’s drainages and rivers. The present findings on the ecological health risks of PTMs based on 2006 samples can serve as an important baseline for future reference and comparison. This work should encourage future investigations on the direct impact of the risks to the residents during floods in Malaysia, as part of mitigation and risk assessments of the contaminated drainage and river sediments in an attempt to lower the hazards for the surrounding residents.

Integration of Electrical Resistivity and Modified DRASTIC Model to Assess Groundwater Vulnerability in the Surrounding Area of Hulene-B Waste Dump, Maputo, Mozambique

In this study, electrical resistivity was applied in six 400 m profiles around the Hulene-B waste dump (Mozambique). Afterwards, an inversion was performed by RES2Dinv. The use of the electrical resistivity method allowed us to characterize in detail some underlying aspects of the DRASTIC index by identifying anomalous zones considered to be permeable and prone to leachate migration. The modified DRASTIC index revealed high values in areas near contaminated surface groundwater and surface layers of the vadose zone, characterized by low resistivities. Areas with lower index results were characterized by high resistivity on surface layers and high depth at which groundwater was detected. The overall modified DRASTIC index result revealed medium vulnerability. However, high vulnerability index values were detected in areas with higher surface elevation, suggesting groundwater contamination by horizontal dilution of leachates from the surrounding area of the Hulene-B waste dump.