Highveld Region Research Articles

The influence of rehydration on decomposition in the Highveld region of South Africa-Using a pig model.

Researchers have observed that rainfall may re-initiate decomposition in desiccated tissue; however, no conclusive research-based evidence exists on the specific effects of rehydration on decomposition. Therefore, this study aimed to assess the effects of artificial rehydration on the progression of decomposition following the advanced stage of decomposition. Twelve adult pig cadavers (8 experimental; 4 controls) were placed in the central Highveld of South Africa during cooler (April-July 2021) and warmer (August-November 2021) months. Decomposition was scored approximately biweekly to obtain the total body score, and accumulated degree days (ADD) were calculated for each pig. All pig cadavers were covered by chicken wire cages with transparent tarps to control for natural rehydration and scavenging. Once the experimental pig cadavers reached a three-visit stasis in the advanced phase of decomposition, they were artificially rehydrated, and changes in the progression of decomposition between the control and experimental groups were plotted (ADD against TBS) for observation. The rehydrated experimental pig cadavers showed re-initiation of decay and insect re-colonization, while the control cadavers mainly remained in a state of stasis with insect activity ceased altogether. Greater cadaver decomposition islands and a color change post-rehydration were also noted in some experimental cadavers. This supports the need for future research on the impact of rehydration, including associated soil moisture on decomposition rates, progression, and invertebrate colonization, which will enhance our understanding of the effects these environmental factors have on the accuracy of post-mortem interval estimation.

The Mpumalanga Highveld Air Pollution Crisis: A South African Reparations Framework for Environmental State–Corporate Harm

The Highveld region in South Africa’s Mpumalanga province has a dense concentration of coal mines and coal-fired power stations. As a result, the area experiences severe levels of air pollution. Despite the government's obligation, little has been done to remedy the harm experienced by the environment and people in the Highveld. The complexity of the relationship between the state and corporations contributes to the government's reluctance to hold mining companies accountable. Obtaining remedies through courts has also yielded limited success. We, therefore, make a case for the creation of African environmental reparations and submit that the Mpumalanga Highveld region evidences the need for such reparations. African environmental reparations must be guided by the principles of Ubuntu, bolstered by the African Charter on Human and Peoples' Rights, and employ restorative justice. Only in this way can air pollution be properly acknowledged as a multifarious harm, and the balance, harmony and unity between people and the environment repaired.

Emerging smallholder cattle farming from a One Health perspective: A system dynamics model of the highveld region of South Africa

BackgroundOne Health is built on the concept that "human health and animal health are interdependent and bound to the health of the ecosystems in which they exist" (OIE, 2021). The zoonotic origins of the COVID-19 pandemic elevated the importance of the One Health concept while highlighting the complexities of human-animal-environmental interfaces in public health management. The definition and purpose of One Health includes an applicability to cattle farming systems. One Health-awareness in livestock rearing is essential in ensuring animal, human, and environmental health and in limiting the spread and emergence of diseases that threaten the health of the three domains. OriginalityThis article identified a gap in One Health research in South Africa and its emerging smallholder cattle production systems. It presents the research problem of the impact of low on-farm productivity on One Health outputs in the emerging smallholder cattle farming sector, and addresses a gap in the academic literature to adopt modelling approaches as a comprehensive means of representing the dynamics of One Health with Systems Dynamic Modelling. MethodologyWe adopt a One Health approach in presenting a system dynamics simulation model of the weaner-rearing production system and the effect of nutrition and disease management on One Health production outputs. ResultsThe model is applied to the highveld region of South Africa and aims to identify the interventions that would most benefit the three One Health parameters of human, animal, and environmental health. The results suggest that increasing farmers' access to disease management training and on-farm infrastructure that aids in disease prevention activities (such as crushing pens) can improve One Health farming outputs (such as improving herd numbers, increasing income from weaner sales, and reducing the disease burden). However, these interventions do not have the desired significant positive impacts on cattle nutrition or feed density. Therefore, some well-intended interventions also have undesirable effects on One Health farming outputs. The results suggest One Health trade-offs within the production system and emphasizes that decision-makers across all levels must clearly define their individual and collective goals when adopting a One Health strategy.

The primary moult of adult Red-headed Finches Amadina erythrocephala

Little is known about the biology of the Red-headed Finch Amadina erythrocephala. This study investigates its primary moult, the first aspect of its life history to be looked at in depth. Additionally, we used a modified Cook’s distance algorithm to explore the influence of individual years on the moult parameter estimates. Lastly, the primary moult of Red-headed Finches is compared to that of other passerines resident in the Highveld region of South Africa. Red-headed Finches breed through the Highveld winter, and start moult on 22 August, on average. Moult extends through spring and most of the summer, reaching completion on 22 February, on average. However, the moult started unusually early in the years 1988, 2005, 2008 and 2019, whereas in 2017 moult started unusually late. The duration of moult was estimated to be 185 days. The majority of other passerines resident in the central Highveld breed through summer, undergo primary moult in autumn, and complete moult before the regular frosts start to occur during the Highveld winter. The moult duration of the Red-headed Finch is substantially longer than that of other resident passerines.

Site quality impacts tree form, heartwood content and veneer production of plantation-grown Pinus patula

Abstract Plantation forest species were introduced into South Africa due to limited availability of native forests for wood-derived products. Currently, the Mexican pine species, Pinus patula, is the most widely planted softwood species in the country. To study the effect of growth environment on wood and processing properties for the species, sample plots were established in a 20-year rotation covering a wide range of soil geologies and altitudes in Mpumalanga, South Africa. Temperature and seasonal rainfall were also determined for the sample plots. Randomly selected sample trees were harvested from the plots and processed at a plywood plant to determine veneer recovery and quality. Trees grown on sites composed of granite soils, with higher annual maximum temperatures and less rainfall, found in the Highveld region, displayed superior tree size, slenderness, and volume growth, compared to trees grown on dolomite and shale soils common to the Lowveld region. Veneer derived from Lowveld trees had more splits which were largely related to defects. Larger trees also had a greater percentage volumetric heartwood and a smaller live crown, compared to smaller trees. Highveld trees had greater net veneer recovery and produced better quality veneer than trees grown on the Lowveld. In the Mpumalanga forestry region, strong co-relatedness exists between soil geology, altitude, and climate. Although tree form and wood properties were found to differ with varying soil geology and altitude, these differences were primarily related to climate rather than soil properties. These findings highlight the pitfalls associated with neglecting either climate or soil properties when analysing site-specific growing conditions on tree growth and form.

Characterisation and pathogenicity of Verticillium dahliae isolates associated with Verticillium wilt of tomato in the Limpopo Province of South Africa

In the Limpopo Province of South Africa, the sustainable production of tomatoes is threatened by a soilborne disease known as Verticillium wilt. Limited information is available regarding the Verticillium species involved, their genetic diversity and aggressiveness. Therefore, a pathogen survey was conducted in the three major tomato production regions in Limpopo (six fields in the Lowveld and two fields each in the Highveld and Soutpansberg). Verticillium dahliae was identified as the only Verticillium species associated with Verticillium wilt of tomatoes. Conventional vegetative compatibility group (VCG) testing identified 38 isolates as VCG 4B and two isolates as VCG 2B. Pathotype-genotype specific PCR analysis indicated that all the isolates belonged to the non-defoliating pathotype, specifically genotype C. These characteristics allowed for the classification of almost all the isolates from the Lowveld, Highveld and Soutpansberg regions into clonal lineage 4B (38 isolates). The exception was for two isolates from the Lowveld that belonged to lineage 2B824. Based on a race-specific PCR analysis, all 40 isolates belonged to race 2. Sequencing of the race-specific PCR amplicon revealed the presence of two haplotypes namely I and II. Evaluation of seven inoculation methods (agar plug, millet, node-inoculation, root-dip, sand-bran, soil-drench and toothpick methods) using three isolates showed that the root-dip method was the only method that consistently identified all the isolates as pathogenic based on disease severity as well as an increase in plant height. Assessment of the aggressiveness of the 40 characterised V. dahliae isolates showed that the isolates varied in aggressiveness to the cv. Floradade.

Building a bridge: characterizing major anthropogenic point sources in the South African Highveld region using OCO-3 carbon dioxide snapshot area maps and Sentinel-5P/TROPOMI nitrogen dioxide columns

In this paper, we characterize major anthropogenic point sources in the South African Highveld region using Orbiting Carbon Observatory-3 (OCO-3) Snapshot Area Map (SAM) carbon dioxide (CO2) and Sentinel-5 Precursor (S5P) TROPOspheric Monitoring Instrument (TROPOMI) nitrogen dioxide (NO2) observations. Altogether we analyze six OCO-3 SAMs. We estimate the emissions of six power stations (Kendal, Kriel, Matla, Majuba, Tutuka and Grootvlei) and the largest single emitter of greenhouse gas (GHG) in the world, Secunda CTL synthetic fuel plant. We apply the cross-sectional flux method for the emission estimation and we extend the method to fit several plumes at the same time. Overall, the satellite-based emission estimates are in good agreement (within the uncertainties) as compared to emission inventories, even for the cases where several plumes are mixed. We also discuss the advantages and challenges of the current measurement systems for GHG emission monitoring and reporting, and the applicability of different emission estimation approaches to future satellite missions such as the Copernicus CO2 Monitoring Mission (CO2M) and the Global Observing SATellite for GHGs and Water cycle (GOSAT-GW), including the joint analysis of CO2 and NO2 observations.

Prevalence of asthma and asthma symptoms among rural and urban pre-school children in Mpumalanga Province, South Africa

Background and Aim: Asthma is the most common chronic illness in South African children and its prevalence is increasing in both urban and rural areas. Little is known about the prevalence of asthma amongst pre-school children living in Mpumalanga province, South Africa, which forms part of the Highveld region, a priority area in terms of air pollution. The area is known for poor air quality and elevated concentrations of criteria pollutants. The aim of the study was to investigate the prevalence of asthma and asthma symptoms among rural and urban pre-school children and the association with environmental risk factors. Methods: This analytical cross-sectional study that included 3145 pre-school children from Mpumalanga Province, South Africa. Parents of the children were requested to complete a modified ISAAC questionnaire. We analyzed the influence of potential risk factors on dependent variables using bivariate analysis. Significant risk factors identified in the bivariate analysis were included in a multiple logistic regression to develop a final model. Results: Self-reported prevalence of asthma was 2.3% (66/2810), with pre-school children in rural areas reporting a higher rate than pre-school children in urban areas (1.3% vs 1%), χ2=10.86, P <0.001). The prevalence of asthma symptoms was 15.1% (467/3084), with rural pre-school children reporting a higher prevalence of symptoms than urban pre-school children (10% vs 5%), χ2 = 24.45, P < 0.001). Risk factors for asthma and asthma symptoms were vigorous physical activity (odds ratio (OR) 2.31, 95% CI 1.14-4.66), home smoking exposure (OR 2.94, 95% CI 1.40-6.19) and male parent smoking (OR 1.46, 95% CI 1.01-2.12). Conclusions: Pre-school children in rural areas reported a higher prevalence of asthma compared to pre-school children in urban areas. Risk factors for asthma included physical activity and smoking exposure in the home. Key words: asthma, pre-school children, risk factors

A case study in the wintertime Vaal Triangle Air-Shed Priority Area on the utility of the nitrogen stable isotopic composition of aerosol nitrate to identify NOx sources

In South Africa, the Highveld region and the Johannesburg-Pretoria megacity are known as global NOx (NOx = NO + NO2) “hotspots” identified by satellite-based instruments. The ultimate sink for atmospheric NOx is conversion to aerosol nitrate. However, measurements of aerosol nitrate concentrations do not provide information on which NOx sources served as nitrate precursors at that location. This complicates efforts to reduce concentrations of particulate matter (PM) in these air quality priority areas. Here, we measured the nitrogen stable isotopic composition of nitrate from daily wintertime collections of coarse mode PM2.5-10 (PM ≤ 10 and >2.5 µm in diameter) at three air quality monitoring stations located in the Vaal Triangle Air-Shed Priority Area (VTAPA). The overall aim of this case study was to evaluate the use of the distinct stable isotopic signatures of various NOx sources to identify their relative contribution to aerosol nitrate across the Highveld. The nitrogen isotopic ratios of aerosol nitrate were similar across the three sites, with greater day-to-day variability than site to site variability. Air mass history was the main driver of the variability in the nitrogen isotopic ratios of aerosol nitrate, with significantly higher isotopic ratios observed for air masses originating from the southwest. Using an isotope mixing model we determined that NOx from coal-burning is the dominant contributor to aerosol nitrate (66%), followed by biomass burning (16%), vehicles (12%), and soil emissions (6%).

The effectiveness of a small-scale combination harvester/forwarder in industrial plantation first thinning operations

ABSTRACT An assessment of the feasibility of using a Malwa 560C combination harvester/forwarder in a selection type first thinning operation in the Highveld region of South Africa was conducted. Each of the machine components, harvesting and forwarding, were assessed separately with resulting machine productivities of 10.84 m3·PMH−1 and 5.03 m3·PMH−1 respectively. An interesting result was found indicating a discrepancy between standing volume, volume harvested and volume reaching roadside. These differences were related to felling and processing trees with no merchantable volume (i.e. felling to waste), other inevitable fiber losses during log assortment production and log assortments not forwarded to roadside. To determine system productivity and cost, calculations must be based on volume reaching roadside otherwise harvester actual productivity is inordinately inflated. Recalculating harvester productivity with volume to roadside productivity is reduced to 6.94 m3·PMH−1. The two functions of the machine cannot be viewed as independent activities. The machine productivity is limited by the least productive component, in this case, forwarding. The system performance productivity was found to be 2.92 m3·PMH−1. A system cost based on this productivity was USD 46.78·PMH−1 and USD 16.05·m−3. This study highlights the importance of accounting for fiber loss in harvester productivity calculations as well as balancing the system’s productivity to avoid overestimations and incorrect assumption in the supply chain. Furthermore, modeling productivity with data representing the adjusted volume demonstrates what is effectively being produced by the whole cut-to-length harvesting system, considering the effect of tree size and quality variability present on these sites.

Contribution of Soil Type to Quantity and Nutritional Value of Grass Species on the South African Highveld

The biggest threat to cattle production in most South African communal areas is poor management of grazing, which negatively affects vegetation and soil structures. This study was conducted to assess the spatial variation of grass species density, production potential and quality in Breyten (Hutton soil type), Davel (Avalon soil type), and Wesselton (Clovelly soil type) communal rangelands in the highveld region of Mpumalanga province. Three 100 m transects per grazing area, placed at 50 m intervals (0, 50, and 100 m) were used to collect soil samples at 200 mm depth. A 100 m permanent line point method, replicated three times (50 m apart) per site, was used to identify and collect grass species samples. Grass species were classified according to life form, palatability, ecological status, and abundance. Grasses species were also harvested for chemical composition and in vitro ruminal dry matter degradability determination. Soils from the study areas had an acidic pH range (3.5–4.5). Hutton soil had the highest (p < 0.05) nitrate (N-NO3) concentration (0.770 mg/kg) compared to Clovelly (0.030 mg/kg) and Avalon (0.533 mg/kg) soil types. Thirty-one grass species composed of 28 turf perennials, two weak perennials and one perennial creeping grass were identified across the study areas. About 16% of identified grass species were classified as highly palatable, 39% as moderately palatable, and 32% as unpalatable. Across all the soil types, Digitaria eriantha had the highest (p < 0.05) crude protein (CP) (106.5 g/kg DM) content when compared to other grass species. In the Avalon soil type, D. eriantha had the lowest (p < 0.05) neutral detergent fiber (NDF) (696.4 g/kg DM). Across all soils, D. eriantha, Aristida congesta, Eragrostis curvula, Eragrostis gummiflua, and Eragrostis plana grasses had the same (p > 0.05) 48-h in vitro ruminal dry matter degradability Hutton soil had a higher proportion of common and dominant grass species as well as more palatable species with higher crude protein content than Avalon and Clovelly soils. However, for all three rangelands, there is a need for supplementary feeding to enhance the production efficiency of livestock given that the nutritive value of grasses was low.

A machine learning model to estimate ambient PM2.5 concentrations in industrialized highveld region of South Africa

Exposure to fine particulate matter (PM2.5) has been linked to a substantial disease burden globally, yet little has been done to estimate the population health risks of PM2.5 in South Africa due to the lack of high-resolution PM2.5 exposure estimates. We developed a random forest model to estimate daily PM2.5 concentrations at 1 km2 resolution in and around industrialized Gauteng Province, South Africa, by combining satellite aerosol optical depth (AOD), meteorology, land use, and socioeconomic data. We then compared PM2.5 concentrations in the study domain before and after the implementation of the new national air quality standards. We aimed to test whether machine learning models are suitable for regions with sparse ground observations such as South Africa and which predictors played important roles in PM2.5 modeling. The cross-validation R2 and Root Mean Square Error of our model was 0.80 and 9.40 μg/m3, respectively. Satellite AOD, seasonal indicator, total precipitation, and population were among the most important predictors. Model-estimated PM2.5 levels successfully captured the temporal pattern recorded by ground observations. Spatially, the highest annual PM2.5 concentration appeared in central and northern Gauteng, including northern Johannesburg and the city of Tshwane. Since the 2016 changes in national PM2.5 standards, PM2.5 concentrations have decreased in most of our study region, although levels in Johannesburg and its surrounding areas have remained relatively constant. This is anadvanced PM2.5 model for South Africa with high prediction accuracy at the daily level and at a relatively high spatial resolution. Our study provided a reference for predictor selection, and our results can be used for a variety of purposes, including epidemiological research, burden of disease assessments, and policy evaluation.

Features of the mineral and chemical composition of the Northwest manganese ore occurrence in the Highveld region, South Africa

The Northwest manganese ore mineralisation is located at a relative distance from traditionally known manganese mining areas in a new manganese-bearing region (Highveld) in the Northwest Province, Republic of South Africa. The ore occurrence was studied on farms: Buchansvale 61 IQ, Weltevreden 517 JQ, Rhenosterhoek 343 JP and Kafferskraal 306 JP. The data obtained from studying the geology of the area pointed out to interests regarding the development criterias for search of similar ore mineralisations in the northwest region of South Africa. The ore occurs predominantly in the form of powdered manganese wad, manganese nodules and crusts, confined to the karstic structures of the upper section of the dolomites. X-ray powder diffraction (XRD), Scanning electron microscopy with energy dispersive link (SEM-EDS) and X-ray fluorescence were utilized to unveil the mineral and chemical composition of the ore samples. The present study therefore presents the results on both chemical and mineral composition of manganese ores, and their depth and longitudinal distribution. Karstic areas causing an increased local thickness of the ore body were identified. The geochemical and microspcopic study of the ores indicates their supergene nature. The main ore minerals includes cryptomelane, lithiophorite, purolusite, hollandite and romanechite associated with impurity components of Ba, Ce, Co, La, Cr, Zn and V.

A dynamic and thermodynamic analysis of the 11 December 2017 tornadic supercell in the Highveld of South Africa

Abstract. On 11 December 2017, a tornadic supercell initiated and moved through the northern Highveld region of South Africa for 7 h. A tornado from this supercell led to extensive damage to infrastructure and caused injury to and displacement of over 1000 people in Vaal Marina, a town located in the extreme south of the Gauteng Province. In this study we conducted an analysis in order to understand the conditions that led to the severity of this supercell, including the formation of a tornado. The dynamics and thermodynamics of two configurations of the Unified Model (UM) were also analysed to assess their performance in predicting this tornadic supercell. It was found that this supercell initiated as part of a cluster of multicellular thunderstorms over a dry line, with three ingredients being important in strengthening and maintaining it for 7 h: significant surface to mid-level vertical shear, an abundance of low-level warm moisture influx from the tropics and Mozambique Channel, and steep mid-level lapse rates. It was also found that the 4.4 km grid spacing configuration of the model (SA4.4) performed better than the 1.5 km grid spacing version. SA1.5 underestimated the low-level warm moisture advection and convergence, and missed the storm initiation. SA4.4 captured the supercell; however, the mid-level vorticity was found to be 1 order of magnitude smaller than that of a typical mesocyclone. A grid length of 4.4 km is too coarse to fully capture the details of a mesocyclone, which may also explain why the model underestimated the surface to mid-level wind shear and low-level horizontal mass and moisture flux convergence. Future investigations will involve experimental research over the Highveld region of South Africa to understand mesoscale and local dynamics processes responsible for tornadogenesis in some severe storms. Such a study, to the best of our knowledge, has never been conducted.

PREHARVEST ABIOTIC CONDITIONS ON THE ACCUMULATION OF BIOACTIVE COMPOUNDS AND ANTIOXIDANT CAPACITIES OF SWEET BELL PEPPER (Capsicum annum L) CULTIVARS IN THE LOW AND HIGH VELD REGIONS OF ZIMBABWE

Abiotic factors coupled with varietal differences have a special bearing on the synthesis of bioactive compounds and enhancement of antioxidant capacities of sweet bell pepper. The aim of the present study was to characterize the content of bioactive compounds (lycopene, vitamin C, β-carotenes, total phenols, and the antioxidant activity of sweet bell pepper (Capsicum annum L) grown under different Agro climatic regions with different environmental conditions, the Eastern Highlands (High veld region) and the Save Valley (low veld region). The results from the study showed statistical differences (p ≤ 0.05) between the different growing locations with regard to the bioactive compounds which were identified and quantified. Capsicum annum var. Lafayette presented the highest concentration of vitamin C content, lycopene content and total phenols as well as the greatest antioxidant activity in the high veld region. In addition, the results indicated that low temperatures favour in vivo biosynthesis of bioactive compounds and enhances antioxidant capacities of sweet bell pepper.

The sensitivity of simulated surface-level pollution concentrations to WRF-ARW-model PBL parameterisation schemes over the Highveld of South Africa

An understanding of the sensitivity of pollutant concentrations to planetary boundary layer (PBL) schemes in numerical weather prediction (NWP) models can provide insight into model results, and possibly advance the accuracy of air pollution modelling. Meteorological output from the Advanced Research Weather Research and Forecasting (WRF-ARW) model, with four frequently used PBL schemes, is used as input for an air quality model. The simulations resulting from the different schemes are compared with each other and evaluated making use of observational air pollution concentration data for a spring and a winter month of 2016 in South Africa. Sensitivity exists in surface-level pollution concentrations as simulated by the considered PBL schemes. No single PBL scheme consistently performed best across the five considered pollutants, five sites and two seasons. During analysis of the air quality simulations, it was found that the two local closure schemes – Mellor-Yamada-Janjić (MYJ) and Mellor-Yamada Nakanishi Niino (MYNN) – often performed well, while the non-local closure schemes – Yonsei University (YSU) and Asymmetric Convection Modelling (ACM) – featured as best-performing schemes the least number of times. Sensitivity also exists on a spatial scale between schemes when simulating sulphur dioxide (SO2) plumes from tall stacks, and the MYNN scheme frequently produced the highest concentrations of SO2. The results from this study should be considered when configuring NWP models for the simulation of air quality in the Highveld region.

Sensitivity of meteorological variables on planetary boundary layer parameterization schemes in the WRF-ARW model

The accuracy of meteorological fields produced by Numerical Weather Prediction (NWP) models are highly dependent on the physical parameterization schemes used. Any errors in simulations of meteorological fields will be passed on to subsequent processes (i.e. air quality models), and will have an effect on their outputs. Therefore, the realistic simulation of meteorological parameters is of utmost importance. The aim of the present research is to evaluate the performance of Planetary Boundary Layer (PBL) schemes contained in the non-hydrostatic Advanced Research Weather Research and Forecasting (WRF-ARW) model when simulating meteorological variables. Four frequently used PBL schemes were investigated by conducting sensitivity experiments during a month in spring and winter in the South African Highveld region for 2016. The simulations resulting from the different schemes were compared against one another, and statistically evaluated by making use of observational meteorological data at five sites. From these results, it is recommended that a local scheme be used for the Highveld region during winter. During spring, the clearly preferred scheme for the Highveld is Mellor–Yamada–Janjić (MYJ) scheme. Results from this study contributes to the establishment of a preferred PBL scheme in the WRF-ARW model, for use in South African Highveld region. Future planned research will considered the effect of the above-mentioned PBL schemes in the simulation of air quality over the same region.

Natural archives of long-range transported contamination at the remote lake Letšeng-la Letsie, Maloti Mountains, Lesotho

Naturally accumulating archives, such as lake sediments and wetland peats, in remote areas may be used to identify the scale and rates of atmospherically deposited pollutant inputs to natural ecosystems. Co-located lake sediment and wetland cores were collected from Letšeng-la Letsie, a remote lake in the Maloti Mountains of southern Lesotho. The cores were radiometrically dated and analysed for a suite of contaminants including trace metals and metalloids (Hg, Pb, Cu, Ni, Zn, As), fly-ash particles, stable nitrogen isotopes, polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants such as polychlorinated biphenyls (PCBs), polybrominated flame retardants (PBDEs) and hexachlorobenzene (HCB). While most trace metals showed no recent enrichment, mercury, fly-ash particles, high molecular weight PAHs and total PCBs showed low but increasing levels of contamination since c.1970, likely the result of long-range transport from coal combustion and other industrial sources in the Highveld region of South Africa. However, back-trajectory analysis revealed that atmospheric transport from this region to southern Lesotho is infrequent and the scale of contamination is low. To our knowledge, these data represent the first palaeolimnological records and the first trace contaminant data for Lesotho, and one of the first multi-pollutant historical records for southern Africa. They therefore provide a baseline for future regional assessments in the context of continued coal combustion in South Africa through to the mid-21st century.

Pedogenesis of bleached topsoils occurring on weakly structured, high chroma subsoils in South Africa

Topsoil bleaching is a common occurrence in South African soils. Bleaching is usually associated with the removal of soil pigmenting agents through redox stripping, clay eluviation and/or podzolisation. Thus topsoil bleaching above non-podzolic, high chroma red and yellow, supposedly well-drained subsoils is difficult to explain. These deep, weakly structured, red and yellow subsoils are some of the best agricultural soils in the country, and when climate allows, are farmed intensively. Bleached topsoils are known for their unfavourable physical characteristics, therefore understanding how these soils form is important to guide their taxonomic discrimination so that they can be managed sustainably.Profiles showing bleached and non-bleached (high chroma) topsoils were sampled from two different geographical regions; the summer rainfall eastern Highveld region and the winter rainfall, Western Cape Boland region. These samples were statistically compared to identify differences between bleached and non-bleached variants. Topsoil bleaching was shown to be hydrologically driven in catenal sequences in the summer rainfall region. In the red – yellow – grey topographic sequence, subsoil colour changes lag behind topsoil colour changes resulting in a zone where bleached topsoils overly high chroma yellow subsoils. The significantly higher (p = 0.05) acid oxalate/citrate dithionite bicarbonate Fe ratio (Far) in bleached topsoils adds further evidence to a redox driven system. Bleached profiles from the Highveld show indicators of increased subsoil clay accumulation, but it is proposed this is not a dominant process and is likely to be a result rather than the cause of bleaching.Bleaching mechanisms in the Western Cape are harder to establish. Only water dispersible clay differs significantly (p = 0.01) between bleached and non-bleached variants. Extractable Fe fractions do not provide significant evidence of redox pathways, although Far is slightly higher in bleached topsoils, despite a lower absolute oxalate extractable Fe concentration. Although not significant (p = 0.11), exchangeable Na, is higher in the bleached profiles and this may account for the more dispersible nature of the bleached profiles. These results suggest that topsoil bleaching in the Western Cape red apedal soils should be used as an indicator for poor structural stability and that these soils require more stringent management to prevent degradation.

Characteristics of Spherical Organic Particles Emitted from Fixed-Bed Residential Coal Combustion

Residential coal combustion is one of the most significant sources of carbonaceous aerosols in the Highveld region of South Africa, significantly affecting the local and regional climate. This study investigated single coal-burning particles emitted when using different fire-ignition techniques (top-lit up-draft versus bottom-lit up-draft) and air ventilation rates (defined by the number of air holes above and below the fire grate) in selected informal braziers. Aerosol samples were collected on nucleopore filters at the Sustainable Energy Technology and Research Centre Laboratory, University of Johannesburg. The individual particles (~700) were investigated using a scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (EDX). Two distinct forms of spherical organic particles (SOPs) were identified, one less oxidized than the other. The particles were further classified into electronically dark and bright. The EDX analysis showed that 70% of the dark spherical organic particles had higher (~60%) relative oxygen content than in the bright SOPs. The morphology of spherical organic particles were quantified and classified into four categories: ~50% were bare single particles; ~35% particles were aggregated and formed diffusion accretion chains; 10% had inclusions, and 5% were deformed due to impaction on filter material during sampling. This study concludes that there are two distinct kinds of coal burning spherical organic particles and that dark SOPs are less volatile than bright SOPs. The authors also show that these spherical organic particles are similar in nature and characteristics to tar balls observed in biomass combustion and that they have the potential to absorb sunlight thereby affecting the earth’s radiative budget and climate. This study provides insights into the mixing states, morphology, and possible formation mechanisms of these organic particles from residential coal combustion in informal stoves.