A new method based on high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS) was validated for the determination of selected toxic and potentially toxic metals in wastewater resulting from mining activity. The results were compared with inductively coupled plasma optical emission spectrometry (ICP-OES). The HR-CS-FAAS method was characterized by detection limits in the range (µg L-1) 0.9(Mn)-33.6(Pb), better than ICP-OES for Cu, Fe, Ni, Co, Pb and Mn, and poorer for Cd, Zn and Cr. The Dunnett's and Tukey's statistical test showed that both methods were not affected by significant bias against certified value and between them. The recovery in HR-CS-FAAS method was in the range of 98-103% with relative extended uncertainty of 9-25%, and precision of 1.5-14.1%. The results indicated that the HR-CS-FAAS method is suitable for the determination of toxic and potentially toxic elements directly in filtered water samples without any chemical treatment.

Iron (Fe) is a micronutrient that can be toxic at elevated concentrations, prompting its significance in frequent environmental monitoring. Typically analyzed using methods such as FAAS, ICP-OES and ICP-MS, the challenge of expensive instrumentation operated only in the laboratory presents a barrier for rapid and frequent testing. This study aimed to develop a silica-based smartphone-assisted on-site method for rapid detection of Fe in water using ImageJ software. Suitable conditions, including reagents and a color intensity measurement tool, were optimized for this method. Figures of merit such as detection limit, accuracy and precision were determined. The results showed that adding polyacrylic acid to detection points for silica worsened the results, in contrast to results for paper devices. It was also found that, on ImageJ, it is best to use an integrated density tool to measure color intensity, contrary to the previously reported mean gray tool. Results showed a limit of detection of 0.2 ng, a limit of quantification of 0.6 ng, a linear range of 0.6 ng to 4.5 ng and RSD of <20%. This method is therefore an alternative in field pre-testing and screening. Future studies include application of this method in the field with real samples and in the analysis of other metals.

We investigated the spatial and temporal variations of the stable isotope composition of hydrogen (δD) and oxygen (δ18O) and the total dissolved ions (TDI) concentrations in the Okavango River in the middle Kalahari Desert. We aimed to elucidate the role of evaporation in controlling river solute enrichment from samples collected at a one- to two-month frequency from nine stations along a ∼460 km river transect for one year. We found that the δD and δ18O composition and the TDI concentrations increased downriver. Seasonal increases in the δD and δ18O composition and TDI concentrations during the hot, rainy season were subdued or decreased during the cool, dry season from pulse flooding. The δD and δ18O values of the samples plot along the Okavango Delta Evaporation Line consistent with evaporation. The effect of evaporation during river transit was related to the mean δD (δD = 0.07*River distance (km) − 37.9; R2 = 0.98) and mean d-excess (d-excess = −0.04*River distance (km) + 9.9; R2 = 0.94). The effect of evaporation on the river solute behavior is characterized by the mean d-excess and TDI concentrations (d-excess = −0.29*TDI (mg/L) + 15.0; R2 = 0.97). Some samples from this study and those compiled from published studies plot at greater than one sigma standard deviation above and below the mean TDI concentration vs. mean d-excess regression model line. We use these marked deviations from the mean TDI concentration vs. the mean d-excess regression model to suggest that additional solutes from river-floodplain-wetland-island interaction driven by pulse flooding are delivered into the river. While our findings support an evaporation-dominated solute enrichment during river transit at the seasonal scale, we conclude that intermittent hydrology (pulse flooding) plays an important role in the sub-seasonal spatiotemporal behavior of solutes in rivers in arid watersheds, which must be considered in solute cycling models.

Fish can be a key strategy in addressing the global food and nutrition insecurity challenges. Fish nutrient data are critical for policy development targeting to reduce these problems. Despite this, much of the published studies on nutritional characteristics of fish have focused on marine ecology and there is little information on natural freshwater fish habitats like inland delta areas. This study investigated the nutrient composition of Okavango Delta fishes and their potential contribution to the recommended nutrient intake. Fish species sampled were Clarias ngamensis, Oreochromis andersonii, Schilbe intermedius, Marcusenius altisambesi, Brycinus lateralis, Barbus poechii and Tilapia sparrmanii. The nutrients analyzed were moisture, ash, proteins, Na, K, Ca, Mg, P and Zn. The small fishes ( B. lateralis and B. poechii ) had higher mineral content; Ca (643–968 mg/100 g), Mg (47–49 mg/100 g) and Zn (2.8–3.6 mg/100 g) compared to the larger species with average mineral content; Ca (73–460 mg/100 g), Mg (23–35 mg/100 g), Zn (1.2–2.9 mg/100 g). The most nutrient-dense species recognized were B. poechii and B. lateralis followed by the large species, M. altisambesi. These species illustrated the potential to contribute 80–121% Ca, 32–47% Mg and 70–150% Zn of the recommended nutrient intake to children (1–9 years), pregnant women and the elderly (65 + years). The study recommends prioritizing small and some large species ( M. altisambesi and T. sparrmanii ) for polyculture systems, primarily for securing food and nutrition security for local communities.

Morula (Sclerocarya birrea) beer is a seasonal homemade alcoholic beverage made from morula fruits pulp.Unlike the commercial morula alcoholic beverage, the alcohol content of homemade morula beer is not known.The major challenges with homemade alcoholic beverages arise from batch-to-batch differences in product quality and safety due to the variability of raw materials and lack of quality control.Consequently, the alcohol content of alcoholic beverages made by the same individual may differ.In this study, a validated liquid-liquid extraction gas chromatography-mass spectrometry (GC-MS) method is used for the quantification of ethanol and identification of volatiles in homemade morula alcoholic beverage.The analysed samples contained ethanol with concentrations ranging from 0.5 to 5.8% v/v depending on the number of days the sample was fermented.Other volatile compounds that were identified were acetic acid, propanol, propanal, butanal, 3-methyl-1-butanol; 2-methyl-1-butanol, butanoic acid, iso-amyl acetate, butanoic acid ethyl ester, benzyl alcohol, phenyl ethyl alcohol, lactic acid, humulene, decanoic acid ethyl ester and 2methyl-1-hexadecanoic acid ethyl ester.The volatile compounds were found to decrease over time.These results provides a validated method for the characterisation of homemade alcoholic beverages and information on the quality of morula beer.

A method for the analysis of heavy metals in homemade alcoholic beverages using an Inductively Coupled Plasma-Mass spectrometry (ICP-MS) was developed and validated for accuracy, precision, linearity, limit of detection and quantification. Linearity was discovered to be in the concentration range of 10–50 (ppb) with correlation coefficient (R2) of above 0.99 for all the seven detected metals. The method is precise with %RSD values ≤ 5 %. Limits of detection and quantification were 0.01–0.16 and 0.10–1.6 (ppb), respectively. The accuracy ranged from 95.1 % to 105.3 %. Thirty-two samples of locally brewed homemade alcoholic beverages and five commercial samples were subsequently analysed using the method. The detected metals included manganese, cobalt, chromium, copper, zinc, aluminium, and lead. The concentrations of Aluminium and Lead in some homemade samples exceeded the set maximum allowable limits (MAL) of the World Health Organisation. The carcinogenic and non-carcinogenic human health risk assessments were also performed for the detected heavy metals. The carcinogenic risk analysis revealed that chromium and lead values were above the safety level of 10−4 set by the United States Environmental Protection Agency (USEPA) in some samples. This suggests that the two metals can pose potential cancer risks to consumers. There were no apparent non-carcinogenic health risks associated with the studied heavy metals. The results obtained from this study will contribute to the growing body of literature regarding the safety of homemade alcoholic beverages around the world.

(a) To use a gas chromatography-mass spectrometry (GC-MS) method for the analysis of drugs of abuse in wastewater in Botswana. (b) To explore the knowledge of the BIUST community on the use, disposal, and fate of medicinal and illegal drugs in wastewater using a survey. Wastewater-based epidemiology (WBE) is increasingly becoming an alternative method for estimating drug usage and consumption in a population. The data obtained through WBE on drug usage and consumption is near real-time and it allows analysts to monitor current patterns and trends in novel psychoactive substances, illicit drugs, and therapeutic compounds. WBE can be complemented with other conventional methods to obtain data on drug use and abuse such as survey questionnaires. The survey is administered in communities where wastewater samples are collected. The data obtained through the two means are compared and a correlation is established if any. Through survey responses, researchers can obtain the demographic information of participants, frequency of use, and mode of administration of drugs. Twenty-two influent wastewater samples were collected at five wastewater treatment plants (WWTP) in Botswana between July 2019 and October 2019 using the grab sampling method. Solid-Phase extraction with Strata-X Drug B SPE cartridges was used for sample extraction before analysis by GC-MS. Toxicology checkout mixture (TCM) with 28 analytes, caffeine and ibuprofen standards were used. The online survey questionnaire was administered to the BIUST community between March 2021 and May 2021 using convenient sampling. Data analysis was done using the Statistical Package for the Social Sciences. The GC-MS method was used as a screening method targeting pharmaceuticals and illicit drugs (opioids, sedatives, stimulants, and hallucinogens). Ibuprofen and caffeine were reliably identified in wastewater samples. The online survey respondents indicated the use of different pharmaceutical drugs such as ibuprofen and panado (acetaminophen). Survey respondents also indicated the use of different illicit drugs such as marijuana, cocaine, and methamphetamine. For the survey, 80.8% of the respondents used medicinal drugs compared to 15.8% who used illegal drugs. Of the respondents who indicated to have used medicinal drugs, 88.7% used painkillers, while 4.1% used antidepressants. Of the respondents who had used illicit drugs, 94.7% used hallucinogens while only 10.5% used stimulants such as cocaine. All the pharmaceutical and illicit drugs that participants indicated to have used were targeted in wastewater samples. A GC-MS method was successfully used for qualitative analysis of wastewater samples in which ibuprofen and caffeine were detected. The two compounds were also targeted. Illicit drugs which were targeted in wastewater when TCM was analyzed were not detected. The survey respondents indicated the use of medicinal and illicit drugs with the former being used more. The respondents also indicated that leftover/expired medicinal/illicit drugs are thrown in the litter bins or flushed down the drain. Most respondents are aware of the fate of the drugs in wastewater. The survey results do not correlate with the analytical results as the drugs in the survey answers were not detected in wastewater from BIUST, although ibuprofen was detected in other wastewater samples used for this research. Ibuprofen, a common pharmaceutical and caffeine, were detected in wastewater collected for this research using a screening method. With further refinement, this method can be used to monitor weekly, monthly, or seasonal variations in drug use in Botswana. The survey respondents indicated the use of different medicinal and illicit drugs, with medicinal drugs being used more. Results obtained from the research will assist stakeholders in Botswana in the fight against drug abuse as they provide information on commonly used drugs, frequency of use, and demographic information of participants.

Pristine aquatic environments are the preferred state for maintaining ecosystem integrity, supporting biodiversity and preserving human health. However, world ecosystems have been altered by anthropogenic activities which release chemical contaminants into the environment and threaten terrestrial and aquatic life. In order to protect water bodies from pollution, monitoring water quality indicators and levels of trace metals is critical. The Okavango Delta is regarded pristine, but concentrations of trace metals in the river have not been adequately studied. This study quantifies concentration of 10 trace metals, determines their spatiotemporal distribution and assesses associated health risks. Water samples were collected monthly between 2014 and 2017 from five sites and concentrations determined by ICP-OES. The results indicate that all metals studied were present at all study sites with a concentration in the order of Fe > Mn > Ni > V>Zn > Pb > Cd ≫ Cu > Cr > Co, a wide occurrence of metals reflecting a possible presence of mafic and ultramafic rocks in the catchment. Concentrations of trace metals were variable, but these were not statistically significant at p ≤ 0.05, indicating a relatively uniform water composition. However, Fe occurred in distinctively higher concentrations compared to other metals. When compared with US EPA guidelines for freshwater ecosystems and WHO drinking water standard, mean concentrations of all metals except Pb were below EPA guidelines for freshwater ecosystems and WHO drinking water standard. The risk assessment revealed that none of the metals posed health risks to the communities that use river water as a direct drinking source. Continuous monitoring is necessary for the protection of human health and sustainability of the delta.

Overuse of pesticides in vegetables and related fresh products raises serious public health concerns. However, the recognition and assessment of the magnitude of public health risk remains a low priority in low income African communities. Brassicas are a cosmopolitan crop in African horticulture, and equally so, is the major economic pest, the diamondback moth, Plutella xylostella (L.). In consequence, insecticide use on P. xylostella in brassica production systems presents persistent pesticide overuse on produce directly destined for public consumption. Using the quick easy cheap effective rugged and safe (QuEChERS) multi-residue analysis method, followed by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS), we investigated the occurrence and magnitude of pesticide residues at three vegetable market levels (farmgates, vendors and supermarkets) in Botswana. We detected pesticide residues in 74.1% of the samples while 33.4% had multiple compounds. Farmgates recorded higher pesticide residues than other markets. We multi-detected 10 low-highly hazardous pesticides [World Health Organisation (WHO)] (classes 1B & II), that included Organophosphates, Pyrethroids, Neonicotinoids and Carbamates. Fifty percent of the detected pesticides from farms and supermarkets had residue quantities exceeding the Codex Maximum Residue Limit thresholds; although estimated daily per capita consumption was lower than the WHO Average Daily Intake (ADI) and Acute Reference Doses (ARfDs). These results indicate presence of multiple and excessive pesticide residues in routinely consumed vegetables on the markets, and points to an imminent public health hazard. Urgent attention is needed to develop and enforce effective policies and regulations on pesticide use practices and investment in non-chemical pest management alternatives.

Introduction An area exclosure is the practice of land management that involves the exclusion of livestock and humans from openly accessing an area that is characterized by severe degradation. Area exclosures have been employed as cheap and convenient means of rehabilitating degraded forests/woodlands. A study was carried out to (i) assess the species richness, diversity and evenness; (ii) determine the densities, frequencies, dominance and importance value index; and (iii) assess the population structure and regeneration status of woody species inside and outside the fence (area exclosure) of Okavango Research Institute (ORI) located in Maun, northern Botswana. Results Thirty-five woody species were recorded inside (32 spp.) and outside (24 spp.) the ORI compound, and the population structure and regeneration status of the woody species were better inside than outside the ORI compound. The exclosure had seven times higher mean density of woody species than outside ORI, and an exceptional regeneration of seedlings was observed inside than outside the ORI compound, suggesting the process of recovery of the degraded woodland. The frequencies of more than half of the woody species also showed increment inside than outside the exclosure. The results suggest that the exclosed area is still in an initial recovery stage since it had been an open grazing area prior to the establishment of the exclosure. Most of the woody species encountered outside ORI showed hampered recruitment and regeneration, owing to different anthropogenic impacts and overgrazing by animals. Conclusions Despite the relatively short period (10 years) of exclosure establishment, results from the present study have further provided empirical evidences on the actual crucial roles played by area exclosures to increase woody species richness, diversity, evenness, density, frequency, dominance and important value index as well as enhance the population structure and regeneration of the woody species in northern Botswana. Future research is recommended focusing on comparative studies on herbaceous species richness, diversity and density, horizontal and vertical distribution of soil seed banks, species richness of soil microorganisms, plant and soil biomass, plant and soil carbon pools (above and below ground) as well as soil contents and properties inside and outside the ORI compound.

Wetland goods and services provide a means of survival for many riparian rural communities in developing countries, particularly in the Sub-Saharan Africa. To sustain the provision of goods and services for human use, spatial and temporal variations in the quantity and quality of water in a given wetland should be adequately understood and managed. In this study we monitored the quantity and quality of surface water through the Okavango Delta for 2 years, from June 2008 to June 2010. Specifically we monitored precipitation over the Delta and surface inflow and outflow (via the Okavango and Thamalakane Rivers respectively) for water quantity, nutrients, cation and anion levels in the surface water along a river transect from Mohembo through the Delta to Lake Ngami. The study revealed that the water balance during the study period was similar to earlier reports. Most of the water inflow was via the Okavango River while surface outflow via the Boro River accounted for about 2% of total inflow. Calcium (Ca) and bicarbonate (HCO3 -) were the most dominant cation and anion respectively across the river transect sampled except in Lake Ngami where sodium (Na) was the dominant cation. Total nitrogen (0.222±0.018 to 0.698±0.035 mg L-1) and total phosphorus (0.042±0.005 to 0.131±0.024 mg L-1) levels across the Delta were generally low. The N:P ratios suggest spatial and temporal P and N growth limitations in the Delta. N limitation seems to be ameliorated by biological nitrogen fixation. Since nutrient poor aquatic systems tend to be very sensitive to pollution, excessive P input into the Delta should be avoided to prevent eutrophication.

The Okavango Delta depends on water quantity and quality to sustain its ecosystem services. Whereas many studies have been carried out on its hydrology, few have been done on water quality in the delta. Water pH, electrical conductivity (EC), dissolved oxygen (DO), turbidity, total suspended solids (TSS) and dissolved organic carbon (DOC) were monitored at 10 sites along the Okavango-Boro-Thamalakane-Lake Ngami system almost fortnightly from June 2008 to June 2010. Water quality in the delta was generally good, despite high evapotranspiration rates which would normally produce very saline waters. Electrical conductivity and water temperature increased with distance from Mohembo to Lake Ngami, the former most likely due to evapoconcentration. In contrast, pH, DO, turbidity and TSS decreased with distance from Mohembo to Boro at the lower end of the seasonal floodplain, before increasing again to Lake Ngami. Dissolved oxygen and TSS most likely declined due to biological uptake and particle sedimentation, respectively. Strong and significant relationships were observed between TSS and turbidity and between DOC and EC, indicating that turbidity and EC could be useful proxies for routine estimations of TSS and DOC, respectively, in the delta.

Contamination of vegetables with toxic metals is one of the most important contributing factors to ill health throughout the world, more so because vegetables are considered essential for human health and their consumption is highly recommended by health authorities. The aim of this study was to determine the concentrations of selected essential elements (Fe, Cu, Mn, Mo, Zn) and toxic elements (As, Cd, Cr, Pb) in common vegetables sold for human consumption in supermarkets and open market of Maun village, Botswana. Five vegetables (cabbage, rape, tomatoes, onions and potatoes) were purchased from different selling points, washed with de-ionised water, cut into small pieces and digested with aqua regia on a block digester, following the US. EPA method 200 - 7 and analysed for metal content using Inductively Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES). The results showed that concentrations of essential and toxic metals varied with the type of vegetable and also with the market category (supermarket or street vendor). The highest concentration of essential elements was obtained from cabbage with a Zn concentration of 135.4mg/Kg and the lowest was from onion with a Mo concentration of 1.35mg/Kg. For toxic elements the highest concentration was obtained from rape vegetable with a Pb concentration of 4.73mg/Kg and the lowest from the same vegetable with Cr concentration below the detection limit. Also observed was that leafy vegetables, especially cabbage, had the highest concentrations of most trace metals. It was concluded that vegetables sold in Maun had sufficient levels of essential elements but also some had high concentrations of toxic metals. We thus recommend consumption of vegetables from the studied markets with reduced frequency to avoid metal poisoning.

The Okavango River runs through 3 countries; Angola, Namibia and Botswana and is a major source of water for drinking and other domestic uses for the basin communities in the riparian states. Developments in the 3 countries, e. g. agriculture, tourism, mining, power generation industries, etc., are putting pressure on the river's water quality which threatens both human and overall ecosystem health. Data is therefore needed to monitor changes of water quality as a result of both natural and anthropogenic sources. The objective of this study was to quantify the concentration levels of aluminium (Al) and beryllium (Be) at three sites (Mohembo East, Sepopa and Guma) of the Okavango Delta's panhandle, study the influence of water discharge and pH on concentration of these metals and evaluate the human health risks associated with their occurrence. Surface water samples were collected in triplicates every three weeks from 3 sampling sites between July 2014 and October 2015. Samples were preserved with nitric acid and stored in the laboratory before analysis. Direct analysis with ICP-OES was used to determine their concentrations. Al values ranged from 0.032 - 0.305mg/L at Mohembo East; 0.005 - 0.333 mg/L at Sepopa and 0 - 0.151mg/L for Guma. Be concentrations ranged between 0 - 0.008mg/L at all three sites. There were no significant differences (P> 0.05) between the three sites in concentrations of these metals. Seasonal variations in metal concentrations were observed for both metals, with the highest concentrations occurring around October, coinciding with lowest water levels. In accordance with the WHO regulatory limits for drinking water, the mean concentrations of both Al and Be, and the calculated hazard quotient(HQ) which was less than 1, do not pose any long term human health threats. However, both metals need to be monitored because concentrations above 200 mu g/L for Al and 4 mu g/L for Be (WHO acceptable limits) were exceeded at times at these sampling sites, which may cause acute toxicity to humans and aquatic organisms. From this study, we concluded that both aluminium and beryllium exist in the Okavango River at concentrations comparable to world river values. We recommend a more comprehensive monitoring programme for toxic metals in the Okavango River to ensure protection of both human and ecosystem health.

Ethnobotanical investigations were conducted at Xobe and Shorobe Villages in northwestern Botswana to identify woody plants used by the local people. A total of 90 households (35 in Xobe and 55 in Shorobe) were interviewed using a semi-structured questionnaire and personal interviews. A total of 38 woody species representing 16 families and 25 genera were recorded. Of these, 28 species representing 15 families and 22 genera were recorded from Shorobe, and 27 species representing 10 families and 15 genera were recorded from Xobe. The uses of woody plants were grouped into eight categories, namely construction, fuelwood, furniture, medicine, human food, fodder, farm implements, and shade. Several of the species are used for more than one purpose. At both study sites, the use category with the highest proportion of number of woody species and proportion among the use categories was human food. Thirteen of the families were represented by 23 woody species that are used for medicinal purposes, and the most commonly used plant parts were the roots, bark, leaves, and stems. Nine of the 28 woody species (28%) in Shorobe and nine of the 27 woody species (33.3%) in Xobe provide edible parts. Six (21%) and eight (30%) woody species recorded in Shorobe and Xobe, respectively, are used for construction purposes. Most plants are used as fuelwood for household energy generation. In spite of the scarcity of natural forests in the study areas, the local communities continue to depend on the indigenous woody species in their surroundings for their survival. Virtually all trees identified in the different families are useful in one way or another in the lives of the rural communities, with most of the species serving more than one function. There is, therefore, a need for cultivation, protection, and sustainable management of these valuable resources for sustaining rural livelihoods in the study sites.

Atmospheric methane (CH4) is one of the three key greenhouse gases (GHGs) driving global climate change. The atmospheric concentration of CH4 has increased by about 150 % above pre-industrial levels of 400–700 ppb due to anthropogenic activities. Although tropical wetlands account for 50–60 % of the global wetland CH4 emissions, the biogeochemistry of these wetlands, including controls of CH4 emissions from the systems, is poorly understood compared to temperate wetlands. This has resulted in large inter-model variations of the magnitude and distribution of CH4 emission estimates from these tropical wetlands. A recent study in the Okavango Delta, Botswana, estimated diffusive CH4 flux at 1.8 ± 0.2 Tg year−1, accounting for 2.8 ± 0.3 % of the total CH4 emission from tropical wetlands. In this paper we present an assessment of relationships between diffusive CH4 flux rates and physicochemical variables in the overlying water column to identify and understand regulatory variables for the diffusive CH4 fluxes in the Delta. The results show that diffusive CH4 flux rates from the Delta seem to be controlled by a combination of physicochemical variables. Although site specific fluxes seem to be controlled by different combinations of factors, temperature was the primary predictor of CH4 flux rates at almost all the sampled habitats and sites in the Delta. Most physicochemical variables, especially in the permanent swamps, were correlated with temperature implying that their regulatory effect on diffusive CH4 fluxes could be modified by climate change feedback as well.