No abstract

No abstract

South Africa is prone to droughts and is heavily dependent on stored water resources. Few studies in South Africa have investigated the impact of drought on water quality when rainfall resumes and reservoir sediments are rewet. Other research has shown that several negative impacts may occur with rewetting, including eutrophication, and acidification with increased metal solubility. In this study, the impact of drying and rewetting sediments on the mobility of nutrients and metals is explored using sediments from Loskop Reservoir. Rarely exposed sediments were collected from three sites, dried at 35°C for 36 days, and then rewet under aerobic conditions. Filtered water samples were collected on Days 1, 2 ,4, 7, 11 and 16 following rewetting, and analysed for , and were compared to reference (non-drought) treatments that were maintained under saturated conditions. Acute toxicity tests were performed using Daphnia magna to establish if toxic effects were associated with changes in water quality following sediment rewetting. Following rewetting, elevated SO 4 2-indicated the mobilisation of acid from sulfide oxidation, with an associated reduction in pH. Nitrification was evident as high quantities of organic N and NH 4 + were initially released, followed by increases in NO 2 -+ NO 3 -. Total P increased, but PO 4 3-reduced. This was attributed to complexes formed between PO 4 3-and Fe (FePO 4 ) and Al (AlPO 4 ). Amounts of Fe and Al released were lower following rewetting due to the formation of relatively immobile (hydr)oxides. In contrast, Mn increased substantially reaching maximum values > 2 300 mg/m 2 (14 000 µg/L). There were no acute toxic effects observed to D. magna. This study highlights the potential for acidification, mobilisation of nutrients, SO 4 2-, and Mn following rewetting of reservoir sediments under aerobic conditions. This information may be incorporated into reservoir and catchment management plans in the form of revised water quality guidelines and a better ability to predict how drought impacts water quality in our stored water resources.

Background As one of the 40 driest countries in the world with an annual average rainfall of 497 mm, South Africa is a water-scarce country. Additionally, South Africa's rate of economic development is closely linked to its water security. Thus, increasing water stress, supply variability, flooding, and water pollution levels and inadequate access to safe drinking water and sanitation are slowing economic growth. Despite the high premium placed on South Africa's water resources, no commonly shared understanding of water security exists. The aim of this study was to research, using qualitative social scientific methods, how people in two South African localities understand water security. Interpretation How people perceive water security has policy implications at the local government level in SouthAfrica and further afield in other low-income and middle-income countries where data collection is unreliable. We established that people from diverse lifestyles hold various understandings and interpretations of water security relating mainly to the availability, access, and quality of water resources. Understanding how people perceive water security in specific localities could aid policy makers and health practitioners to develop more nuanced responses to ameliorate water insecurity and its negative effects on people's wellbeing.

This paper presents the levels of detection of selected agricultural pesticides in river and tap water in the Letsitele, Lomati and Vals–Renoster catchments, South Africa. Agriculture plays a major role in the development of communities through job creation and poverty eradication. However, exposure to agricultural pesticides can result in serious human health and environmental effects. This study, therefore, identified critical areas where specific pesticides might result in high environmental and human health risks. Three water catchment areas, namely, Letsitele, Lomati and Vals–Renoster, were identified for raw and tap water analysis. The results confirmed the presence of selected agricultural pesticides:  atrazine, terbuthylazine, imidacloprid, metolachlor, simazine and alachlor. Although low concentrations of most of these pesticides were detected, pesticides such as atrazine, alachlor and simazine are known for endocrine disruption. A critical finding of this study is the detection of these pesticides in tap water (drinking water) of a primary school in the Lomati catchment. This reveals a high exposure potential for human health. It is thus recommended that further research be conducted to determine the potential health risks associated with these pesticides among vulnerable communities, through epidemiological studies.

No abstract