Quantification of Emissions Generated from Domestic Burning Activities from Townships in Johannesburg

Domestic burning activities, specifically in informal settlements, contribute greatly to the air quality problems experienced by most developing urban centres. Low-income households that exist within townships in South Africa house a large portion of the South African population. These households burn vast quantities of coal, wood and other substances to provide for their energy needs. Pollutants emitted as a result of domestic burning are estimated to be one of the leading causes of respiratory illnesses in inhabitants of townships. To better understand the relationship that exists between domestic burning and the resultant pollutants, a method of quantifying these pollutants has been developed for a completely un-electrified settlement, near Johannesburg, using the quantities and type of fuel consumed. Seasonality, availability, price and cultural aspects all have a bearing on the fuel source choice and the quantity consumed. The most significant temporal observations identified for domestic burning are seasonal ones

SUBSURFACE GAS GENERATION AT A LANDFILL IN JOHANNESBURG

Landfill gas (LFG) consisting of 50-60 % v/v CH4 contributes to global greenhouse gas emissions as well as to local air pollution and nuisance odours; in addition, the uncontrolled subsurface migration of LFG can pose an explosion hazard. LFG is explosive mostly due to its CH4 content. CH4 is explosive at concentrations of 5-15 % in air. Venting of the gas to the atmosphere prevents any explosion risk; however, the concern lies with the lateral migration of CH4 through soil and along cracks and its subsequent accumulation. This highlights the importance of subsurface LFG monitoring. In this study, subsurface LFG generation is measured at a solid waste disposal site situated approximately 20 km west of Johannesburg. The results of three first-order kinetic models (to estimate LFG generation) for the site are compared. The three models are LandGEM, GasSim and the IPCC model contained in the 2006 UNFCCC 2006 National Inventory Guidelines for waste. High LFG concentrations are recorded along the northern boundary of the site (exceeding 60% v/v). Modelled LFG generation simulations are slightly higher from LandGEM whilst the IPCC Waste Model predicts the lowest concentrations

Aerosol-Radiation-Cloud Interactions in the South-East Atlantic: First Results from the ORACLES-2016 Deployment and Plans for Future Activities

Southern Africa produces almost a third of the Earths biomass burning (BB) aerosol particles. Particles lofted into the mid-troposphere are transported westward over the South-East (SE) Atlantic, home to one of the three permanent subtropical stratocumulus (Sc) cloud decks in the world. The SE Atlantic stratocumulus deck interacts with the dense layers of BB aerosols that initially overlay the cloud deck, but later subside and may mix into the clouds. These interactions include adjustments to aerosol-induced solar heating and microphysical effects, and their global representation in climate models remains one of the largest uncertainties in estimates of future climate. Hence, new observations over the SE Atlantic have significant implications for regional and global climate change predictions.Our understanding of aerosol-cloud interactions in the SE Atlantic is severely limited. Most notably, we are missing knowledge on the absorptive and cloud nucleating properties of aerosols, including their vertical distribution relative to clouds, on the locations and degree of aerosol mixing into clouds, on the processes that govern cloud property adjustments, and on the importance of aerosol effects on clouds relative to co-varying synoptic scale meteorology.We describe first results from various synergistic, international research activities aimed at studying aerosol-cloud interactions in the region:NASAs airborne ORACLES (ObseRvations of Aerosols Above Clouds and Their IntEractionS) deployment in AugustSeptember of 2016,the DoEs LASIC (Layered Atlantic Smoke Interactions with Clouds) deployment of the ARM Mobile Facility to Ascension Island (June 2016 October 2017), the ground-based components of CNRS AEROCLO-sA (Aerosols Clouds and Fog over the west coast of southern Africa), and ongoing regional-scale integrative, process-oriented science efforts as part of SEALS-sA (Sea Earth Atmosphere Linkages Study in southern Africa).We expect to describe experimental setups as well as showcase initial aerosol and cloud property distributions. Furthermore, we discuss the implementation of future activities in these programs in coordination with the UK Met Offices CLARIFY (CLoud-Aerosol-Radiation Interactions and Forcing) experiment in 2017

NITROGEN OXIDES ON THE SOUTH AFRICAN HIGHVELD

Satellite retrievals have highlighted the South African Highveld as a region with one of the highest nitrogen oxide (NOx) emission densities in the world. There are numerous sources of NOx on the Highveld, including coal-fired power stations, petrochemical and other industries, motor vehicles and lightning, but surface measurements of NOx have not indicated that there is any cause for concern. A number of research initiatives are being undertaken in an attempt to resolve the discrepancy between surface measurements and satellite retrievals of NOx. An assessment of ground-level concentrations in various environments, including industrial and urban regions, has shown that NOx levels recorded in the low-income urban area are significantly higher than those recorded downwind of industries or power stations. NO2 column densities have been remotely sensed over the Highveld using an airborne imaging DifferentialOptical Absorption Spectrometer (iDOAS), in order to validate the satellite retrievals and investigate individual sources of NOx. Results from the first campaign show high NO2 integrated column densities in the immediate vicinity of sources. Well defined plumes can be observed downwind of prominent sources

A review of South African research in atmospheric science and physical oceanography during 2000-2005

The purpose of this article is to review progress in the fields of atmospheric science and physical oceanography made by workers based at South African institutions over approximately the last 5 years. Research published by South African scientists working abroad is not included. Most published research in these fields falls within the broad areas of climate variability, climate change, aerosols and atmospheric pollution, seasonal forecasting, numerical modelling (both atmospheric and oceanic), and the physical oceanography of the Agulhas and Benguela current systems. Most but not all of the atmospheric science papers relate to South Africa or southern Africa; however, some work pertaining to the southern hemisphere as a whole or to other regions has been done. We note that funding and institutional support for atmospheric science and physical oceanography research in South Africa remains poor and this situation significantly hampers local efforts

Climate change and urban development in southern Africa : the case of Ekurhuleni Municipality (EMM) in South Africa

In this paper, outcomes from an investigation of plausible climate futures over the next century, and the potential impacts on water services including water resource management and disaster risk reduction, such as flash flooding in Ekurhuleni (EMM), are presented. Four key aspects are examined: (i) the extent to which the frequency of extreme rainfall events may change in South Africa as a result of climate change; (ii) the identification of some of the implications of extreme rainfall events for local government (iii) the identification of some of the challenges communities most at risk of flooding as a result of extreme rainfall events face, finally, (iv) the opportunities for future co-production of design methods and approaches to reduce current and future climate risks in EMM and elsewhere. Climate modelling conducted for this research indicates that it is plausible for an increase in the number of extreme rainfall events to occur over central and eastern South Africa over the next century. Over EMM, for example, an increase in extreme rainfall events is likely to be accompanied by flash flooding and a range of deleterious impacts, if planning and maintenance of the water services infrastructure is not improved – a result that is likely to be valid for all large metropolitan municipalities in the country. The paper provides some lessons learnt when trying to include a climate risk reduction approach into the planning of urban development.The Water Research Commissionhttp://www.wrc.org.zaam201

Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network

The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (~0.004–0.005), even for strong winds over 10 m s<sup>−1</sup>. The relationships show significant scatter (correlation coefficients typically in the range 0.3–0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network

The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (~0.004–0.005), even for strong winds over 10 m s−1. The relationships show significant scatter (correlation coefficients typically in the range 0.3–0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

Characterization of satellite-based proxies for estimating nucleation mode particles over South Africa

Proxies for estimating nucleation mode number concentrations and further simplification for their use with satellite data have been presented in Kulmala et al. (2011). In this paper we discuss the underlying assumptions for these simplifications and evaluate the resulting proxies over an area in South Africa based on a comparison with a suite of ground-based measurements available from four different stations. The proxies are formulated in terms of sources (concentrations of precursor gases (NO2 and SO2) and UVB radiation intensity near the surface) and a sink term related to removal of the precursor gases due to condensation on pre-existing aerosols. A-Train satellite data are used as input to compute proxies. Both the input data and the resulting proxies are compared with those obtained from ground-based measurements. In particular, a detailed study is presented on the substitution of the local condensation sink (CS) with satellite aerosol optical depth (AOD), which is a column-integrated parameter. One of the main factors affecting the disagreement between CS and AOD is the presence of elevated aerosol layers. Overall, the correlation between proxies calculated from the in situ data and observed nucleation mode particle number concentrations (Nnuc) remained low. At the time of the satellite overpass (13:00–14:00 LT) the highest correlation is observed for SO2/CS (R2 = 0.2). However, when the proxies are calculated using satellite data, only NO2/AOD showed some correlation with Nnuc (R2 = 0.2). This can be explained by the relatively high uncertainties related especially to the satellite SO2 columns and by the positive correlation that is observed between the ground-based SO2 and NO2 concentrations. In fact, results show that the satellite NO2 columns compare better with in situ SO2 concentration than the satellite SO2 column. Despite the high uncertainties related to the proxies calculated using satellite data, the proxies calculated from the in situ data did not better predict Nnuc. Hence, overall improvements in the formulation of the proxies are needed

Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study

This paper presents new laboratory measurements of the mass absorption efficiency (MAE) between 375 and 850 nm for 12 individual samples of mineral dust from different source areas worldwide and in two size classes: PM10:6 (mass fraction of particles of aerodynamic diameter lower than 10.6 \u3bcm) and PM2:5 (mass fraction of particles of aerodynamic diameter lower than 2.5 \u3bcm). The experiments were performed in the CESAM simulation chamber using mineral dust generated from natural parent soils and included optical and gravimetric analyses. The results show that the MAE values are lower for the PM10:6 mass fraction (range 37\u2013135x10-3 m2 g-1 at 375 nm) than for the PM2:5 (range 95\u2013711x10-3 m2 g-1 at 375 nm) and decrease with increasing wavelength as lambda-AAE, where the \uc5ngstr\uf6m absorption exponent (AAE) averages between 3.3 and 3.5, regardless of size. The size independence of AAE suggests that, for a given size distribution, the oxide fraction, which could ease the application and the validation of climate models that now start to include the representation of the dust composition, as well as for remote sensing of dust absorption in the UV\u2013vis spectral region