Trace metal enrichment observed in soils around a coal fired power plant in South Africa

A site assessment was conducted at a coal fired power plant in South Africa to determine whether surrounding soils were being enriched with trace metals resulting from activities at the power plant. It was found that deposition of fly ash from the flue stacks and the ash dump along with deposition of coal dust from the coal stock yard were the activities most likely to lead to such enrichment. Eighty topsoil samples were gathered and analysed for total metal content. Results were interpreted within the context of background values. It was found that concentrations of As, Cu, Mn, Ni and Pb exceeded local screening levels, but only As and Pb could be confidently attributed to anthropogenic intervention and actual enrichment.&nbsp

Characterizing light-absorbing aerosols in a low-income settlement in South Africa

Light‑absorbing aerosols, particularly black carbon (BC), have significant impacts on human health and the climate. They are also the least‑studied fraction of atmospheric particles, particularly in residential areas of southern Africa. The optical characteristics of ground‑based light‑absorbing aerosols from Kwadela Township in South Africa are investigated in this study. Daily averaged ambient PM2.5 highest levels were 51.39 µg m‑3 and 32.18 µg m‑3, whereas hourly averages peaked at 61.31 µg m‑3 and 34.69 µg m‑3 during winter and summer, respectively. Levels of daily averaged light–absorbing aerosols were 2.9 times higher (1.89 ± 0.5 μg m‑3) in winter 2014 than in summer 2015 (0.66 ± 0.2 μg m‑3). In both seasons, hourly averaged levels showed bimodal diurnal cycles, which correlated with the PM2.5 diurnal patterns that indicated distinct peaks in the morning and evening. These diurnal cycle peak periods corresponded with the times of increased solid domestic fuel usage, road traffic, and also shallower boundary layer. On average, light‑absorbing aerosols contributed a larger proportion of total ambient PM2.5 levels in winter (6.5 ± 1.0 %) than in summer (3.4 ± 1.0 %). The winter average Absorption Ångstrӧm exponent AAE(370/880 nm) (1.7± 0.5), indicated the dominance of brown carbon (BrC) from biofuel/biomass burning and/or low‑quality coal combustion emissions. In summer, the average AAE(370/950 nm) (1.3 ± 0.7), suggested the presence of BC and BrC in the mornings and evenings possibly from fossil fuel combustion sources. At midday and at night in summer, the AAE was close to 1, suggesting more BC contributions from sources such as diesel emissions during this time. A combination of BC and BrC particulates dominated on 50 % and 5 % of the summer days, respectively, whereas fresh BC were only measured in summer days (23 %). Residential solid‑fuel and/biomass combustion are important sources of light‑absorbing aerosols in this study region, with concomitant human health and environmental impact