Assessment of Potentially Toxic Elements as Non-Point Sources of Contamination in the Upper Crocodile Catchment Area, North-West Province, South Africa

Modelling relationships between land use and water quality using statistical methods: A critical and applied review

Land use/land cover (LULC) can have significant impacts on water quality and the health of aquatic ecosystems. Consequently, understanding and quantifying the nature of these impacts is essential for the development of effective catchment management strategies. This article provides a critical review of the literature in which the use of statistical methods to model the impacts of LULC on water quality is demonstrated. A survey of these publications, which included hundreds of original research and review articles, revealed several common themes and findings. However, there are also several persistent knowledge gaps, areas of methodological uncertainty, and questions of application that require further study and clarification. These relate primarily to appropriate analytical scales, the significance of landscape configuration, the estimation and application of thresholds, as well as the potentially confounding influence of extraneous variables. Moreover, geographical bias in the published literature means that there is a need for further research in ecologically and climatically disparate regions, including in less developed countries of the Global South. The focus of this article is not to provide a technical review of statistical techniques themselves, but to examine important practical and methodological considerations in their application in modelling the impacts of LULC on water quality.

Anthropogenic Land Use and Land Cover Change as Potential Drivers of Sediment Sources in the Upper Crocodile River, North West Province, South Africa

In this study, we investigated the accelerating pace of anthropogenic land use and land cover change (LULCC) disturbance, which has generated enormous impacts on the Crocodile River. Spot images from 1996, 2009 and 2022 were used to generate the land use maps and quantify the changes. A supervised classification with the maximum likelihood classifier was used to classify the images. Sediment sources were classified into two sources, revealed by erosional characteristics in the catchment. A gamma spectrometry detector, high-purity germanium (HPGe) "Well" detector by Canberra and inductively coupled plasma mass spectrometry (ICP-MS) were used for the analysis of the samples. The results revealed that from 1996-2022, built-up areas, bare land and water bodies increased by 3.48%, 2.47% and 1.90%, respectively. All the LULCC classes increased annually from 1996-2022, except for grassland, which shrunk. The results of the radionuclides analysis showed that ²¹⁰Pb_ex was found to be a more effective tracer than ¹³⁷Cs. The mass balance model revealed that subsurface sources contributed 60%, while surface sources contributed 40%, of the sediment load in the river. This research provides valuable information necessary for integrated catchment management policies for future LULCC and soil erosion to be adopted.

A review on the adsorption mechanism of different organic contaminants by covalent organic framework (COF) from the aquatic environment

Recently, covalent organic frameworks (COFs) have gained significant attention as a promising material for the elimination of various organic pollutants due to their distinctive characteristics such as high surface area, adjustable porosity, high removal efficiency, and recyclability. The efficiency and selectivity of COFs depend on the decorated functional group and the pore size of the chemical structure. Hence, this review highlights the adsorption removal mechanism of different organic contaminants such as (pharmaceutical and personal care products, pesticides, dyes, and industrial by-products) by COFs from an aqueous solution. Spectroscopic techniques and theoretical calculation methods are introduced to understand the mechanism of the adsorption process. Also, a comparison between the performance of COFs and other adsorbents was discussed. Furthermore, future research directions and challenges encountered in the removal of organic contaminants by COFs are discussed.

Aquatic Ecological Risk of Heavy-Metal Pollution Associated with Degraded Mining Landscapes of the Southern Africa River Basins: A Review

Africa accounts for nearly 30% of the discovered world’s mineral reserves, with half of the world’s platinum group metals deposits, 36% of gold, and 20% of cobalt being in Southern Africa (SA). The intensification of heavy-metal production in the SA region has exacerbated negative human and environmental health impacts. In recent years, mining waste generated from industrial and artisanal mining has significantly affected the ecological integrity of SA aquatic ecosystems due to the accelerated introduction and deposition of heavy metals. However, the extent to which heavy-metal pollution associated with mining has impacted the aquatic ecosystems has not been adequately documented, particularly during bioassessments. This review explores the current aquatic ecological impacts on the heavily mined river basins of SA. It also discusses the approaches to assessing the ecological risks, inherent challenges, and potential for developing an integrated ecological risk assessment protocol for aquatic systems in the region. Progress has been made in developing rapid bioassessment schemes (RBS) for SA aquatic ecosystems. Nevertheless, method integration, which also involves heavy-metal pollution monitoring and molecular technology, is necessary to overcome the current challenges of the standardisation of RBS protocols. Citizenry science will also encourage community and stakeholder involvement in sustainable environmental management in SA.

Modelling the dynamics of the cancer risk due to potentially toxic elements in agricultural soils, in the upper Crocodile River catchment, North-West province, South Africa

Contaminated agricultural soil with potentially toxic elements (PTEs) poses a threat to food safety and can adversely affect human health. This study evaluates the potential health risk caused by PTEs contamination in cultivated soils and the possible related health effect. Sixty-four (64) soil samples from cultivated soils before crop cultivation and post-crop were harvested and twenty-four (24) soil samples from a natural game reserve park were collected and. The PTEs were analysed using the inductively coupled plasma-mass spectrometry (ICP-MS) for the following elements As, Cd, Cr, Cu, Ni, Pb, Zn, Mn, Al, and Fe. The contamination factor (CF), pollution load index (PLI), hazard quotient (HQ), and hazard index (HI) was calculated to assess the human health risks for the different pathways to the exposed population. A carcinogenic probabilistic risk model based on the mathematical derivation and PTEs transmission pathways is presented. The mean concentrations of the PTEs in the cultivated soil varied in order of Al > Fe > Mn > Cr > Ni > Zn > Cu > Pb > As > Cd. Cr and Ni concentrations in all the cultivated soils were found to be higher than the Canadian guidelines and the Finnish permissible threshold guidelines for agricultural. The CF in the soil indicates extreme contamination suggestion an ecotoxicological effect. The PLI value also suggests that the soils have undergone some form of deterioration, particularly with Cr and Ni. The ingestion seems to be the major pathway followed by dermal to children. The HQ and HI values for the children were > 1 indicating an adverse health effect for the children residing around the cultivated fields. The simulated results indicate that the percentage of the affected humans that may be consuming crop derived from the contaminated soil increases by a factor of 2 as the contamination factor increases. The transmission compartments can be used as an effective measure in which mitigation can be effectively used.

Effects of ambient particulate matter on vascular tissue: a review

Fine and ultra-fine particulate matter (PM) are major constituents of urban air pollution and recognized risk factors for cardiovascular diseases. This review examined the effects of PM exposure on vascular tissue. Specific mechanisms by which PM affects the vasculature include inflammation, oxidative stress, actions on vascular tone and vasomotor responses, as well as atherosclerotic plaque formation. Further, there appears to be a greater PM exposure effect on susceptible individuals with pre-existing cardiovascular conditions.

Performance of metal–organic frameworks for the adsorptive removal of potentially toxic elements in a water system: a critical review

Elevated levels of potentially toxic elements (PTEs) in aqueous environments have drawn attention recently due to their presence and toxicity to living beings. There have been numerous attempts to remove PTEs from aqueous media. The potential of metal–organic frameworks (MOFs) in removing PTEs from aqueous media has been recognized due to their distinctive advantages (e.g., increased removal capability, large surface area, adjustable porosity, and recyclability). Because of the poor stability of MOFs in water, pre and post synthetic modification and functionalization of MOFs have also been developed for water treatment investigations. This review addresses the performance and mechanisms of PTE removal in various modified MOFs in detail. In order to compare the performance of MOFs, here we used partition coefficient (PC) instead of maximum adsorption capacity, which is sensitively influenced by initial loading concentrations. Therefore, the PC of each material was used to evaluate the adsorption performance of different MOFs and to compare with other sorbents. Furthermore, it discusses the scale-up issues and forthcoming pathway for the research and development needs of MOFs for effective PTE removal. This review further elucidates the main removal mechanisms of PTEs by MOFs. Commercial or domestic water treatment systems or water filters can utilize engineered MOFs to treat water by adsorptive removal. However, marketable products have yet to be investigated thoroughly due to limitations of the large-scale synthesis of MOFs.

This review examines the performance of metal–organic frameworks based on partition coefficient data over the classic maximum adsorption capacities.