Floods are among the natural hazards that have adverse effects on human lives, livelihoods, economies and infrastructure. Dry climates of southern Africa have, over the years, experienced an increase in the frequency of tropical cyclone induced floods. However, understanding the key factors that influence susceptibility to floods has remained largely unexplored in these dry climates. Therefore, this study sought to model flood hazards and determine key factors that significantly explain the probability of flood occurrence in the southern parts of Beitbridge District, Zimbabwe. To achieve these objectives, logistic regression was used to predict spatial variations in flood hazards following cyclone Dineo in 2017. Before spatial prediction of flood hazard, environmental variables were tested for multicollinearity using the Pearson correlation coefficient. Only two environmental variables, i.e., elevation and rainfall, were not significantly correlated and were thus used in the subsequent flood hazard modelling. Results demonstrate that two variables significantly (p < 0.05) predicted spatial variations in flood hazard in the southern parts of the Beitbridge District with relatively high accuracy defined by the area under the curve (AUC = 0.98). In addition, results indicate that ~56 % of the study area is regarded as highly susceptible to floods. Given the projected increase in extreme events such as intense rainfall as a result of climate change, floods will be expected to correspondingly increase in these semi-arid regions. Results presented in this study underscore the importance of geospatial techniques in flood-hazard modelling, which is the key input in sustainable land-use planning. It can thus be concluded that spatial analytical techniques play a key role in flood early warning systems aimed at supporting and building resilient communities in the face of climate change–induced floods.
{"title":"Modelling flood hazard in dry climates of southern Africa: a case of Beitbridge, Limpopo Basin, Zimbabwe","authors":"Lloyd Chikwiramakomo, Webster Gumindoga, Munyaradzi Davis Shekede, Tawanda Winmore Gara, Talent Chuma","doi":"10.17159/wsa/2021.v47.i4.3787","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3787","url":null,"abstract":"Floods are among the natural hazards that have adverse effects on human lives, livelihoods, economies and infrastructure. Dry climates of southern Africa have, over the years, experienced an increase in the frequency of tropical cyclone induced floods. However, understanding the key factors that influence susceptibility to floods has remained largely unexplored in these dry climates. Therefore, this study sought to model flood hazards and determine key factors that significantly explain the probability of flood occurrence in the southern parts of Beitbridge District, Zimbabwe. To achieve these objectives, logistic regression was used to predict spatial variations in flood hazards following cyclone Dineo in 2017. Before spatial prediction of flood hazard, environmental variables were tested for multicollinearity using the Pearson correlation coefficient. Only two environmental variables, i.e., elevation and rainfall, were not significantly correlated and were thus used in the subsequent flood hazard modelling. Results demonstrate that two variables significantly (p < 0.05) predicted spatial variations in flood hazard in the southern parts of the Beitbridge District with relatively high accuracy defined by the area under the curve (AUC = 0.98). In addition, results indicate that ~56 % of the study area is regarded as highly susceptible to floods. Given the projected increase in extreme events such as intense rainfall as a result of climate change, floods will be expected to correspondingly increase in these semi-arid regions. Results presented in this study underscore the importance of geospatial techniques in flood-hazard modelling, which is the key input in sustainable land-use planning. It can thus be concluded that spatial analytical techniques play a key role in flood early warning systems aimed at supporting and building resilient communities in the face of climate change–induced floods.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"7 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86129875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3873
Deeksha Ranjan, Moonis Ali Khan, Marta Otero, Masoom Raza Siddiqui, Shareefa Ahmed Alshaeef
This study was aimed at employing response surface methodology (RSM) for optimization of process variables and identifying optimal conditions for the adsorption of bromate (BrO3-) from contaminated water using multi-walled carbon nanotubes, based on iron hydr(oxide), Fe-CNTs nanocomposite. Fifteen experimental runs were conducted in batch mode to study the effect of individual as well as interactive process variables, i.e., pH, BrO3− initial concentration, and adsorbent dose, on the removal of BrO3− using Box–Behnken design (BBD) of RSM. The coefficient of determination (R2) at 98.34% indicated a good agreement between actual and predicted values. The main effect and contour plot were drawn to obtain the independent and interactive effect of operational variables on BrO3− uptake. A process optimization curve was drawn to determine the optimum operating conditions that lead to a desirable response. The optimum conditions for BrO3− adsorption using Fe-CNTs nanocomposite were found to be pH 2.0, initial BrO3− concentration of 10.0 mg/L, and adsorbent dose of 0.010 g per 50 mL solution.
{"title":"Optimization of bromate adsorption onto Fe-CNTs nanocomposite using response surface methodology","authors":"Deeksha Ranjan, Moonis Ali Khan, Marta Otero, Masoom Raza Siddiqui, Shareefa Ahmed Alshaeef","doi":"10.17159/wsa/2021.v47.i4.3873","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3873","url":null,"abstract":"This study was aimed at employing response surface methodology (RSM) for optimization of process variables and identifying optimal conditions for the adsorption of bromate (BrO3-) from contaminated water using multi-walled carbon nanotubes, based on iron hydr(oxide), Fe-CNTs nanocomposite. Fifteen experimental runs were conducted in batch mode to study the effect of individual as well as interactive process variables, i.e., pH, BrO3− initial concentration, and adsorbent dose, on the removal of BrO3− using Box–Behnken design (BBD) of RSM. The coefficient of determination (R2) at 98.34% indicated a good agreement between actual and predicted values. The main effect and contour plot were drawn to obtain the independent and interactive effect of operational variables on BrO3− uptake. A process optimization curve was drawn to determine the optimum operating conditions that lead to a desirable response. The optimum conditions for BrO3− adsorption using Fe-CNTs nanocomposite were found to be pH 2.0, initial BrO3− concentration of 10.0 mg/L, and adsorbent dose of 0.010 g per 50 mL solution. \u0000 ","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"35 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81674062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3817
Bruna Martins Vicentin, Raquel Dalla Costa da Rocha
This work aims to study the potential of expanded perlite (EP) for amoxicillin (AMX) removal in aqueous solution. For this purpose, chemical, morphological, and textural characteristics of the EP were evaluated, in addition to AMX removal by the adsorption process. The kinetic, isothermal, and thermodynamic parameters were also assessed. The EP presented an isoelectric point of 6.5 and a surface with hydroxyl bands, which favour the adsorption process. Air bubbles were sealed and randomly connected with each other, increasing the surface area relative to the adsorption sites. These non-porous or macro-porous sites demonstrate efficiency in the mechanisms of mass transfer. AMX removal was determined to be a pseudo-second-order process since the adsorption velocity was proportional to the square of the available adsorption sites and indicates heterogeneity in the surface interactions between the adsorbed molecules. Also, the interactions were considered multilayer for low concentrations and monolayer for high concentrations (Sips isotherm). The adsorption process was endothermic and utilised a physical adsorption mechanism. Considering that no modification treatment was applied to the EP, and due to its neutral isoelectric point, macropores, amorphous and dipole induction force (physical adsorption) characteristics, favourable affinity between EP and AMX was observed.
{"title":"Expanded perlite: potential for removing antibiotics from water","authors":"Bruna Martins Vicentin, Raquel Dalla Costa da Rocha","doi":"10.17159/wsa/2021.v47.i4.3817","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3817","url":null,"abstract":"This work aims to study the potential of expanded perlite (EP) for amoxicillin (AMX) removal in aqueous solution. For this purpose, chemical, morphological, and textural characteristics of the EP were evaluated, in addition to AMX removal by the adsorption process. The kinetic, isothermal, and thermodynamic parameters were also assessed. The EP presented an isoelectric point of 6.5 and a surface with hydroxyl bands, which favour the adsorption process. Air bubbles were sealed and randomly connected with each other, increasing the surface area relative to the adsorption sites. These non-porous or macro-porous sites demonstrate efficiency in the mechanisms of mass transfer. AMX removal was determined to be a pseudo-second-order process since the adsorption velocity was proportional to the square of the available adsorption sites and indicates heterogeneity in the surface interactions between the adsorbed molecules. Also, the interactions were considered multilayer for low concentrations and monolayer for high concentrations (Sips isotherm). The adsorption process was endothermic and utilised a physical adsorption mechanism. Considering that no modification treatment was applied to the EP, and due to its neutral isoelectric point, macropores, amorphous and dipole induction force (physical adsorption) characteristics, favourable affinity between EP and AMX was observed.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"10 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78434752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3882
L. Myeni, MJ Savage, AD Clulow
Accurate quantification of net irradiance of open water (Rn water) is of paramount importance for the estimation of open water evaporation, which is critical for the efficient management of water resources. Alternatively, model estimates of Rn water are often used when quality measurements of Rn water are not readily available for the water storage of interest. A Daily Penman, Monteith, Equilibrium Temperature Hargreaves-Samani (DPMETHS) model has been developed for the estimation of Rn water using land-based meteorological data. The DPMETHS model is a spreadsheet-based iterative procedure that computes Rn water using daily land-based meteorological measurements of solar irradiance (Rs land), minimum and maximum air temperatures (Tmin and Tmax), minimum and maximum relative humidity (RHmin and RHmax) and average wind speed (Uland). In this study, the DPMETHS model was evaluated using daily Rn water in-situ measurements acquired from 5 sites in both hemispheres, representing very different climatic conditions. Results showed reasonable model performance at all 5 sites, with the coefficient of determination (r2) values greater than 0.85 and root mean square error (RMSE) values ranging from 0.60 MJ∙m-2 for Stratus Ocean (East Pacific Ocean) to 1.89 MJ∙m-2 for Midmar Dam (South Africa). The results of this study suggested that the DPMETHS model can be reliably used to estimate Rn water for a wide range of climatic conditions. The performance of the DPMETHS model depends on the representativeness of the land-based meteorological data to the weather conditions above the open water surface. The DPMETHS model is user-friendly with minimal computational and data requirements that allows easy data handling and visual inspection.
{"title":"Modelling daily net radiation of open water surfaces using land-based meteorological data","authors":"L. Myeni, MJ Savage, AD Clulow","doi":"10.17159/wsa/2021.v47.i4.3882","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3882","url":null,"abstract":"Accurate quantification of net irradiance of open water (Rn water) is of paramount importance for the estimation of open water evaporation, which is critical for the efficient management of water resources. Alternatively, model estimates of Rn water are often used when quality measurements of Rn water are not readily available for the water storage of interest. A Daily Penman, Monteith, Equilibrium Temperature Hargreaves-Samani (DPMETHS) model has been developed for the estimation of Rn water using land-based meteorological data. The DPMETHS model is a spreadsheet-based iterative procedure that computes Rn water using daily land-based meteorological measurements of solar irradiance (Rs land), minimum and maximum air temperatures (Tmin and Tmax), minimum and maximum relative humidity (RHmin and RHmax) and average wind speed (Uland). In this study, the DPMETHS model was evaluated using daily Rn water in-situ measurements acquired from 5 sites in both hemispheres, representing very different climatic conditions. Results showed reasonable model performance at all 5 sites, with the coefficient of determination (r2) values greater than 0.85 and root mean square error (RMSE) values ranging from 0.60 MJ∙m-2 for Stratus Ocean (East Pacific Ocean) to 1.89 MJ∙m-2 for Midmar Dam (South Africa). The results of this study suggested that the DPMETHS model can be reliably used to estimate Rn water for a wide range of climatic conditions. The performance of the DPMETHS model depends on the representativeness of the land-based meteorological data to the weather conditions above the open water surface. The DPMETHS model is user-friendly with minimal computational and data requirements that allows easy data handling and visual inspection.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"10 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84816003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3844
W Mupangwa, R Makanza, L Chipindu, M Moeletsi, S Mkuhlani, F Liben, I Nyagumbo, M Mutenje
Rainfall is a major driver of food production in rainfed smallholder farming systems. This study was conducted to assess linear trends in (i) different daily rainfall amounts (<5, 5–10, 11–20, 21–40 and >40 mm∙day-1), and (ii) monthly and seasonal rainfall amounts. Drought was determined using the rainfall variability index. Daily rainfall data were derived from 18 meteorological stations in southern Africa. Daily rainfall was dominated by <5 mm∙day-1 followed by 5–10 mm∙day-1. Three locations experienced increasing linear trends of <5 mm∙day-1 amounts and two others in sub-humid region had increases in the >40 mm day-1 category. Semi-arid location experienced increasing trends in <5 and 5–10 mm∙day-1 events. A significant linear trend in seasonal rainfall occurred at two locations with decreasing rainfall (1.24 and 3 mm∙season-1). A 3 mm∙season-1 decrease in seasonal rainfall was experienced under semi-arid conditions. There were no apparent linear trends in monthly and seasonal rainfall at 15 of the 18 locations studied. Drought frequencies varied with location and were 50% or higher during the November–March growing season. Rainfall trends were location and agro-ecology specific, but most of the locations studied did not experience significant changes between the 1900s and 2000s.
在雨养小农农业系统中，降雨是粮食生产的主要驱动力。本研究旨在评估(i)不同日降雨量(40 mm∙day-1)和(ii)月度和季节性降雨量的线性趋势。干旱是用降雨变率指数来确定的。每日降雨量数据来自南部非洲的18个气象站。日降雨量以40 mm day-1类型为主。半干旱区<5和5 - 10 mm∙day-1事件呈增加趋势。在降雨量减少的两个地点(1.24和3 mm∙season-1)，季节降雨量呈显著的线性趋势。在半干旱条件下，季节性降雨量减少3 mm∙season-1。在研究的18个地点中，有15个地点的月和季降雨量没有明显的线性趋势。干旱频率因地而异，在11月至3月的生长期，干旱频率为50%或更高。降雨趋势与地点和农业生态有关，但大多数研究地点在1900年至2000年间没有发生显著变化。
{"title":"Temporal rainfall trend analysis in different agro-ecological regions of southern Africa","authors":"W Mupangwa, R Makanza, L Chipindu, M Moeletsi, S Mkuhlani, F Liben, I Nyagumbo, M Mutenje","doi":"10.17159/wsa/2021.v47.i4.3844","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3844","url":null,"abstract":"Rainfall is a major driver of food production in rainfed smallholder farming systems. This study was conducted to assess linear trends in (i) different daily rainfall amounts (<5, 5–10, 11–20, 21–40 and >40 mm∙day-1), and (ii) monthly and seasonal rainfall amounts. Drought was determined using the rainfall variability index. Daily rainfall data were derived from 18 meteorological stations in southern Africa. Daily rainfall was dominated by <5 mm∙day-1 followed by 5–10 mm∙day-1. Three locations experienced increasing linear trends of <5 mm∙day-1 amounts and two others in sub-humid region had increases in the >40 mm day-1 category. Semi-arid location experienced increasing trends in <5 and 5–10 mm∙day-1 events. A significant linear trend in seasonal rainfall occurred at two locations with decreasing rainfall (1.24 and 3 mm∙season-1). A 3 mm∙season-1 decrease in seasonal rainfall was experienced under semi-arid conditions. There were no apparent linear trends in monthly and seasonal rainfall at 15 of the 18 locations studied. Drought frequencies varied with location and were 50% or higher during the November–March growing season. Rainfall trends were location and agro-ecology specific, but most of the locations studied did not experience significant changes between the 1900s and 2000s.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"71 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88316188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3861
Jana Späth, Preyan Arumugam, Richard H Lindberg, Ovokeroye A Abafe, Stina Jansson, Jerker Fick, Chris A Buckley
The presence of micropollutants, such as pharmaceuticals and personal care products, in surface and ground water has escalated globally, leading to adverse effects on aquatic organisms in receiving waters. Untreated or inadequately treated wastewater is the main source of micropollutants entering the environment. In South Africa, the consumption of antibiotics and antiretroviral drugs is relatively higher than other nations; however, little data exists on the identification and remediation of micropollutants in domestic wastewater. In this study, a novel method to detect and measure 71 micropollutants using online solid phase extraction liquid chromatography coupled to tandem mass spectrometry was developed. To test the method in the South African context, grab samples of the influent and anaerobically treated effluent (AF effluent) from a demonstration-scale decentralised wastewater treatment system in eThekwini (Durban) were taken over 3 consecutive days at 2 time points. The presence of 24 micropollutants was detected in the raw wastewater, with analgesics/anti-inflammatory drugs, antiretrovirals, and antibiotics showing the highest concentrations and with the majority of compounds still present in the AF effluent. One antibiotic, ciprofloxacin, exceeded its predicted no-effect concentration in all influent and AF effluent samples. This suggests that the anaerobic treatment of the raw wastewater was not effective in removing micropollutants. Preliminary data from lab-scale adsorption experiments using biochar produced from a set of 4 feedstocks – olive residues, tomato residues, rice husks, and the African palm tree Raphia farinifera – showed average removal rates for 4 compounds of up to 62%. The application of biochar is thus recommended as a secondary treatment step in decentralised wastewater treatment for the removal of micropollutants in South Africa.
{"title":"Biochar for the removal of detected micropollutants in South African domestic wastewater: a case study from a demonstration-scale decentralised wastewater treatment system in eThekwini","authors":"Jana Späth, Preyan Arumugam, Richard H Lindberg, Ovokeroye A Abafe, Stina Jansson, Jerker Fick, Chris A Buckley","doi":"10.17159/wsa/2021.v47.i4.3861","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3861","url":null,"abstract":"The presence of micropollutants, such as pharmaceuticals and personal care products, in surface and ground water has escalated globally, leading to adverse effects on aquatic organisms in receiving waters. Untreated or inadequately treated wastewater is the main source of micropollutants entering the environment. In South Africa, the consumption of antibiotics and antiretroviral drugs is relatively higher than other nations; however, little data exists on the identification and remediation of micropollutants in domestic wastewater. In this study, a novel method to detect and measure 71 micropollutants using online solid phase extraction liquid chromatography coupled to tandem mass spectrometry was developed. To test the method in the South African context, grab samples of the influent and anaerobically treated effluent (AF effluent) from a demonstration-scale decentralised wastewater treatment system in eThekwini (Durban) were taken over 3 consecutive days at 2 time points. The presence of 24 micropollutants was detected in the raw wastewater, with analgesics/anti-inflammatory drugs, antiretrovirals, and antibiotics showing the highest concentrations and with the majority of compounds still present in the AF effluent. One antibiotic, ciprofloxacin, exceeded its predicted no-effect concentration in all influent and AF effluent samples. This suggests that the anaerobic treatment of the raw wastewater was not effective in removing micropollutants. Preliminary data from lab-scale adsorption experiments using biochar produced from a set of 4 feedstocks – olive residues, tomato residues, rice husks, and the African palm tree Raphia farinifera – showed average removal rates for 4 compounds of up to 62%. The application of biochar is thus recommended as a secondary treatment step in decentralised wastewater treatment for the removal of micropollutants in South Africa.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79126533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3863
Lis Tavares Ordones Lemos, Fábio Ponciano de Deus, Valter Carvalho de Andrade Júnior, Michael Silveira Thebaldi, Marcio Mesquita, Rodrigo César de Almeida
Irrigated agriculture has become a concern, given the scarcity of freshwater. To reduce its water consumption, new techniques and technologies have been proposed. Based on this, the objective of this work was to evaluate the influence of different soil water tensions at initiation of irrigation with magnetically treated water, on ‘iceberg’ lettuce Lucy Brown (Lactuca Sativa L.) development and production. The experiment was conducted in a greenhouse, using a completely randomized factorial design, to evaluate two water types (magnetically treated water – MW and ordinary water – OW) and four soil water tensions at initiation of irrigation (T1 – 15 kPa, T2 – 25 kPa, T3 – 40 kPa and T4 – 70 kPa), with three replicates. Tensiometers were used to estimate soil water tension. The evaluated parameters were: aerial part fresh and dry total mass; commercial head fresh and dry mass, root fresh and dry mass; stem fresh and dry mass; stem length and diameter; percentage of leaves with tip burn, total and commercial yield; water use efficiency related to total and commercial yield; plant exposed area; and dry matter content. Despite achieving greater water use efficiency, the magnetic treatment may have hindered the removal of water from the soil by the crop, especially at increased soil water tension at initiation of irrigation.
{"title":"Development and production of iceberg lettuce irrigated with magnetically treated water","authors":"Lis Tavares Ordones Lemos, Fábio Ponciano de Deus, Valter Carvalho de Andrade Júnior, Michael Silveira Thebaldi, Marcio Mesquita, Rodrigo César de Almeida","doi":"10.17159/wsa/2021.v47.i4.3863","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3863","url":null,"abstract":"Irrigated agriculture has become a concern, given the scarcity of freshwater. To reduce its water consumption, new techniques and technologies have been proposed. Based on this, the objective of this work was to evaluate the influence of different soil water tensions at initiation of irrigation with magnetically treated water, on ‘iceberg’ lettuce Lucy Brown (Lactuca Sativa L.) development and production. The experiment was conducted in a greenhouse, using a completely randomized factorial design, to evaluate two water types (magnetically treated water – MW and ordinary water – OW) and four soil water tensions at initiation of irrigation (T1 – 15 kPa, T2 – 25 kPa, T3 – 40 kPa and T4 – 70 kPa), with three replicates. Tensiometers were used to estimate soil water tension. The evaluated parameters were: aerial part fresh and dry total mass; commercial head fresh and dry mass, root fresh and dry mass; stem fresh and dry mass; stem length and diameter; percentage of leaves with tip burn, total and commercial yield; water use efficiency related to total and commercial yield; plant exposed area; and dry matter content. Despite achieving greater water use efficiency, the magnetic treatment may have hindered the removal of water from the soil by the crop, especially at increased soil water tension at initiation of irrigation.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"43 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77918043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3875
DM Jacklin, IC Brink, SM Jacobs
In South Africa, rapid environmental degeneration caused by anthropogenic pollution poses a major ecological engineering problem, demanding proper resource mitigation strategies. For the treatment of polluted water and degraded soil systems, green infrastructure (GI) offers an effective, sustainable and affordable nature-based alternative to grey infrastructure. An additive benefit within GI, plant species provide enormous potential to treatment; however, species vary substantially in their pollutant removal and hydrologic performance. South African civil engineers tasked with designing GI often lack expertise and knowledge of plant behaviour and ecosystem dynamics. Therefore, this paper proposes a decision framework to facilitate selection for designing local GI in the form of a phyto-guide, based on existing recommendations and knowledge of removal processes and plant behaviour. Interdisciplinarity at the core of the phyto-guide relies on continuous specialist collaboration with each selection criteria, whilst efficiency and sustainability are considered equally important contributors to successful GI functioning. The spread of invasive alien plants, whether accidental or deliberate, negatively impacts an ecosystem’s capacity to deliver goods and services. Thus, the desire to optimize GI by incorporating effective phytoremediators cannot be prioritised over conservation concerns. In addition, this paper seeks to advance the GI limitation of relying solely on previously identified phytoremediators, by including evaluation criteria of beneficial plant traits as well as plant distribution, behaviour and diversity into the decision-making process for optimized GI. It is recommended that future research engages in discovering less invasive, naturally occurring local species as potential phytoremediators, inspired by South Africa’s rich biodiversity and endemism, as well as conveying the importance of consultation with engineers and ecologists for optimized GI.
{"title":"A phyto-guide to species selection for optimized South African green infrastructure","authors":"DM Jacklin, IC Brink, SM Jacobs","doi":"10.17159/wsa/2021.v47.i4.3875","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3875","url":null,"abstract":"In South Africa, rapid environmental degeneration caused by anthropogenic pollution poses a major ecological engineering problem, demanding proper resource mitigation strategies. For the treatment of polluted water and degraded soil systems, green infrastructure (GI) offers an effective, sustainable and affordable nature-based alternative to grey infrastructure. An additive benefit within GI, plant species provide enormous potential to treatment; however, species vary substantially in their pollutant removal and hydrologic performance. South African civil engineers tasked with designing GI often lack expertise and knowledge of plant behaviour and ecosystem dynamics. Therefore, this paper proposes a decision framework to facilitate selection for designing local GI in the form of a phyto-guide, based on existing recommendations and knowledge of removal processes and plant behaviour. Interdisciplinarity at the core of the phyto-guide relies on continuous specialist collaboration with each selection criteria, whilst efficiency and sustainability are considered equally important contributors to successful GI functioning. The spread of invasive alien plants, whether accidental or deliberate, negatively impacts an ecosystem’s capacity to deliver goods and services. Thus, the desire to optimize GI by incorporating effective phytoremediators cannot be prioritised over conservation concerns. In addition, this paper seeks to advance the GI limitation of relying solely on previously identified phytoremediators, by including evaluation criteria of beneficial plant traits as well as plant distribution, behaviour and diversity into the decision-making process for optimized GI. It is recommended that future research engages in discovering less invasive, naturally occurring local species as potential phytoremediators, inspired by South Africa’s rich biodiversity and endemism, as well as conveying the importance of consultation with engineers and ecologists for optimized GI.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"17 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81175954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3796
O. Iji, E. Njoya, B. Madikizela, J. Myburgh, L. McGaw
Several potential genotoxins found in water samples arise from anthropogenic activities. Acid mine effluent resulting from coal mining poses serious environment concerns all over the world. The use of toxicity tests to evaluate the quality of streams add value by providing site-specific toxicological data. Treatment systems such as the use of natural wetlands (passive) or conventional physical and chemical pH-neutralised processes (active) are employed mainly to meet certain water quality guidelines. Nonetheless, potential genotoxins or residues remain which influence the quality of discharged effluents. The objective of this study was to evaluate the genotoxic potential of acid mine drainage (AMD) released into a natural stream following treatment by passive and active methods. This study aimed to identify the extent of AMD mutagenicity and genotoxicity to African Vero monkey kidney cell line and a fish gill cell line (RTgill-W1) using two assays, the Ames test, and the comet assay, as a rapid and effective screening tool. The Ames test performed without metabolic activation using Salmonella typhimurium TA98 and TA100 strains showed no indication of mutagenicity in the water samples tested. Differing results were however obtained for the comet assay using the African Vero monkey kidney cell line and a fish gill cell line (Rtgill-W1), which revealed DNA fragmentation and variations in morphologies indicative of genotoxicity in the water samples following the two treatment processes. A significant reduction in DNA damage was observed in water samples following active treatment of the AMD, evidenced by reduced damage frequency and a lowered comet score. This bioassay confirms the urgency of integrating high-throughput screening in aquatic toxicity assessment at genetic levels, giving further evidence that in-vitro bioassays can be incorporated for use in short-term genotoxicity assays. The result suggests that the comet assay proved sensitive at detecting genotoxicity, supporting the integration of this into environmental monitoring frameworks targeted at AMD-contaminated sites.
{"title":"Evaluation of the genotoxic potential of water impacted by acid mine drainage from a coal mine in Mpumalanga, South Africa, using the Ames test and Comet assay","authors":"O. Iji, E. Njoya, B. Madikizela, J. Myburgh, L. McGaw","doi":"10.17159/wsa/2021.v47.i4.3796","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3796","url":null,"abstract":"Several potential genotoxins found in water samples arise from anthropogenic activities. Acid mine effluent resulting from coal mining poses serious environment concerns all over the world. The use of toxicity tests to evaluate the quality of streams add value by providing site-specific toxicological data. Treatment systems such as the use of natural wetlands (passive) or conventional physical and chemical pH-neutralised processes (active) are employed mainly to meet certain water quality guidelines. Nonetheless, potential genotoxins or residues remain which influence the quality of discharged effluents. The objective of this study was to evaluate the genotoxic potential of acid mine drainage (AMD) released into a natural stream following treatment by passive and active methods. This study aimed to identify the extent of AMD mutagenicity and genotoxicity to African Vero monkey kidney cell line and a fish gill cell line (RTgill-W1) using two assays, the Ames test, and the comet assay, as a rapid and effective screening tool. The Ames test performed without metabolic activation using Salmonella typhimurium TA98 and TA100 strains showed no indication of mutagenicity in the water samples tested. Differing results were however obtained for the comet assay using the African Vero monkey kidney cell line and a fish gill cell line (Rtgill-W1), which revealed DNA fragmentation and variations in morphologies indicative of genotoxicity in the water samples following the two treatment processes. A significant reduction in DNA damage was observed in water samples following active treatment of the AMD, evidenced by reduced damage frequency and a lowered comet score. This bioassay confirms the urgency of integrating high-throughput screening in aquatic toxicity assessment at genetic levels, giving further evidence that in-vitro bioassays can be incorporated for use in short-term genotoxicity assays. The result suggests that the comet assay proved sensitive at detecting genotoxicity, supporting the integration of this into environmental monitoring frameworks targeted at AMD-contaminated sites.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"47 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90656396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-28DOI: 10.17159/wsa/2021.v47.i4.3801
B Mauck, K Winter
This paper discusses the potential use of ‘managed aquifer recharge’ (MAR) in Cape Town to provide additional water supplies to the city that are fit-for-purpose. The paper investigates the feasibility of implementing MAR by simulating the artificial recharge of winter stormwater into the Cape Flats Aquifer (CFA), an extensive sandy, unconfined aquifer that covers most of metropolitan Cape Town’s urban landscape. The objective is to assess the storage capacity and supply potential of two MAR sites by modelling various scenarios in order to determine the feasibility of MAR as a viable strategy for achieving improved water security by augmenting groundwater water supply. The selected scenarios demonstrated that MAR could be used to minimise the risk of seawater intrusion and maximise the amount of water available for abstraction from the CFA. Six MAR scenarios provided strong evidence to suggest that there is sufficient storage capacity within the CFA for using stormwater to improve the wellfield yield in two regions of the CFA and which can sustainably yield approximately 18 Mm3 per year. The study concluded that the use of stormwater or treated wastewater could be deliberately used to recharge the CFA and as a viable option in support of the City of Cape Town’s intention to establish a water-resilient city by 2030.
{"title":"Assessing the potential for managed aquifer recharge (MAR) of the Cape Flats Aquifer","authors":"B Mauck, K Winter","doi":"10.17159/wsa/2021.v47.i4.3801","DOIUrl":"https://doi.org/10.17159/wsa/2021.v47.i4.3801","url":null,"abstract":"This paper discusses the potential use of ‘managed aquifer recharge’ (MAR) in Cape Town to provide additional water supplies to the city that are fit-for-purpose. The paper investigates the feasibility of implementing MAR by simulating the artificial recharge of winter stormwater into the Cape Flats Aquifer (CFA), an extensive sandy, unconfined aquifer that covers most of metropolitan Cape Town’s urban landscape. The objective is to assess the storage capacity and supply potential of two MAR sites by modelling various scenarios in order to determine the feasibility of MAR as a viable strategy for achieving improved water security by augmenting groundwater water supply. The selected scenarios demonstrated that MAR could be used to minimise the risk of seawater intrusion and maximise the amount of water available for abstraction from the CFA. Six MAR scenarios provided strong evidence to suggest that there is sufficient storage capacity within the CFA for using stormwater to improve the wellfield yield in two regions of the CFA and which can sustainably yield approximately 18 Mm3 per year. The study concluded that the use of stormwater or treated wastewater could be deliberately used to recharge the CFA and as a viable option in support of the City of Cape Town’s intention to establish a water-resilient city by 2030.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"86 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73110201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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