6 research outputs found
Summary of research paper published in atmospheric chemistry and physics titled: Spatial, temporal and source contribution assessments of black carbon over the northern interior of South Africa
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Spatial and temporal assessment of organic and black carbon at four sites in the interior of South Africa
Limited data currently exist for atmospheric organic carbon (OC) and black carbon (BC) in South Africa (SA). In this paper OC and BC measured in SA were explored in terms of spatial and temporal patterns, mass fractions of the total aerosol mass, as well as possible sources. PM10 and PM2.5 samples were collected at five sites in SA operated within the Deposition of Biogeochemical Important Trace Species-IGAC DEBITS in Africa (DEBITS-IDAF) network. OC were higher than BC concentrations at all sites in both size fractions, while most OC and BC occurred in the PM2.5 fraction. OC/BC ratios reflected the location of the different sites, as well as possible sources impacting these sites. The OC and BC mass fraction percentages of the total aerosol mass varied up to 24% and 12%, respectively. A relatively well defined seasonal pattern was observed, with higher OC and BC measured from May to October, which coincides with the dry season in the interior of SA. An inverse seasonal pattern was observed for the fractional mass contributions of OC and BC to the total aerosol mass, which indicates substantially higher aerosol load during this time of the year. The relationship between OC and BC concentrations with the distance that air mass back trajectories passed by biomass burning fires and large point sources proved that biomass burning fires contribute significantly to regional OC and BC during the burning season, while large point sources did not contribute that significantly to regional OC and BC. The results from a highly industrialised and populated site also indicated that household combustion for space heating contributed at least to local OC and BC concentrations
Spatial, temporal and source contribution assessments of black carbon over the northern interior of South Africa
After carbon dioxide (CO2), aerosol black carbon (BC) is considered to
be the second most important contributor to global warming. This paper
presents equivalent black carbon (eBC) (derived from an optical absorption
method) data collected from three sites in the interior of South Africa
where continuous measurements were conducted, i.e. Elandsfontein, Welgegund
and Marikana, as well elemental carbon (EC) (determined by evolved carbon
method) data at five sites where samples were collected once a month on a filter
and analysed offline, i.e. Louis Trichardt, Skukuza, Vaal Triangle,
Amersfoort and Botsalano.Analyses of eBC and EC spatial mass concentration patterns across the eight
sites indicate that the mass concentrations in the South African interior are
in general higher than what has been reported for the developed world and
that different sources are likely to influence different sites. The mean eBC
or EC mass concentrations for the background sites (Welgegund, Louis
Trichardt, Skukuza, Botsalano) and sites influenced by industrial activities
and/or nearby settlements (Elandsfontein, Marikana, Vaal Triangle and
Amersfoort) ranged between 0.7 and 1.1, and 1.3 and
1.4 µg m−3, respectively. Similar seasonal
patterns were observed at all three sites where continuous measurement data
were collected (Elandsfontein, Marikana and Welgegund), with the highest eBC
mass concentrations measured from June to October, indicating contributions
from household combustion in the cold winter months (June–August), as well
as savannah and grassland fires during the dry season (May to mid-October).
Diurnal patterns of eBC at Elandsfontein, Marikana and Welgegund indicated
maximum concentrations in the early mornings and late evenings, and minima
during daytime. From the patterns it could be deduced that for Marikana and
Welgegund, household combustion, as well as savannah and grassland fires,
were the most significant sources, respectively.Possible contributing sources were explored in greater detail for
Elandsfontein, with five main sources being identified as coal-fired power
stations, pyrometallurgical smelters, traffic, household combustion, as well
as savannah and grassland fires. Industries on the Mpumalanga Highveld are
often blamed for all forms of pollution, due to the NO2 hotspot over
this area that is attributed to NOx emissions from industries and vehicle
emissions from the Johannesburg–Pretoria megacity. However, a comparison of
source strengths indicated that household combustion as well as savannah and
grassland fires were the most significant sources of eBC, particularly
during winter and spring months, while coal-fired power stations,
pyrometallurgical smelters and traffic contribute to eBC mass concentration
levels year round
Atmospheric boundary layer top height in South Africa: Measurements with lidar and radiosonde compared to three atmospheric models
Atmospheric lidar measurements were carried out at Elandsfontein measurement station, on the eastern Highveld approximately 150 km east of Johannesburg in South Africa throughout 2010. The height of the planetary boundary layer (PBL) top was continuously measured using a Raman lidar, PollyXT (POrtabLe Lidar sYstem eXTended). High atmospheric variability together with a large surface temperature range and significant seasonal changes in precipitation were observed, which had an impact on the vertical mixing of particulate matter, and hence, on the PBL evolution. The results were compared to radiosondes, CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) space-borne lidar measurements and three atmospheric models that followed different approaches to determine the PBL top height. These models included two weather forecast models operated by ECMWF (European Centre for Medium-range Weather Forecasts) and SAWS (South African Weather Service), and one mesoscale prognostic meteorological and air pollution regulatory model TAPM (The Air Pollution Model). The ground-based lidar used in this study was operational for 4935 h during 2010 (49% of the time). The PBL top height was detected 86% of the total measurement time (42% of the total time). Large seasonal and diurnal variations were observed between the different methods utilised. High variation was found when lidar measurements were compared to radiosonde measurements. This could be partially due to the distance between the lidar measurements and the radiosondes, which were 120 km apart. Comparison of lidar measurements to the models indicated that the ECMWF model agreed the best with mean relative difference of 15.4%, while the second best correlation was with the SAWS model with corresponding difference of 20.1%. TAPM was found to have a tendency to underestimate the PBL top height. The wind speeds in the SAWS and TAPM models were strongly underestimated which probably led to underestimation of the vertical wind and turbulence and thus underestimation of the PBL top height. Comparison between ground-based and satellite lidar shows good agreement with a correlation coefficient of 0.88. On average, the daily maximum PBL top height in October (spring) and June (winter) was 2260 m and 1480 m, respectively. To our knowledge, this study is the first long-term study of PBL top heights and PBL growth rates in South Africa
Atmospheric boundary layer top height in South Africa: measurements with lidar and radiosonde compared to three atmospheric models
Atmospheric lidar measurements were carried out at Elandsfontein measurement
station, on the eastern Highveld approximately 150 km east of Johannesburg
in South Africa throughout 2010. The height of the planetary boundary layer
(PBL) top was continuously measured using a Raman lidar, PollyXT
(POrtabLe Lidar sYstem
eXTended). High atmospheric variability together with a large
surface temperature range and significant seasonal changes in precipitation
were observed, which had an impact on the vertical mixing of particulate
matter, and hence, on the PBL evolution. The results were compared to
radiosondes, CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization)
space-borne lidar measurements and three atmospheric models that followed
different approaches to determine the PBL top height. These models included
two weather forecast models operated by ECMWF (European Centre for
Medium-range Weather Forecasts) and SAWS (South African Weather Service), and
one mesoscale prognostic meteorological and air pollution regulatory model
TAPM (The Air Pollution Model). The ground-based lidar used in this study
was operational for 4935 h during 2010 (49% of the time). The PBL
top height was detected 86% of the total measurement time (42% of
the total time). Large seasonal and diurnal variations were observed between
the different methods utilised. High variation was found when lidar
measurements were compared to radiosonde measurements. This could be
partially due to the distance between the lidar measurements and the
radiosondes, which were 120 km apart. Comparison of lidar measurements to
the models indicated that the ECMWF model agreed the best with mean relative
difference of 15.4%, while the second best correlation was with the SAWS
model with corresponding difference of 20.1%. TAPM was found to have a
tendency to underestimate the PBL top height. The wind speeds in the SAWS
and TAPM models were strongly underestimated which probably led to
underestimation of the vertical wind and turbulence and thus underestimation
of the PBL top height. Comparison between ground-based and satellite lidar
shows good agreement with a correlation coefficient of 0.88. On average, the
daily maximum PBL top height in October (spring) and June (winter) was
2260 m and 1480 m, respectively. To our knowledge, this study is the first long-term study of PBL top heights and PBL growth rates in South Africa
Atmospheric boundary layer top height in South Africa: measurements with lidar and radiosonde compared to three atmospheric models
Atmospheric lidar measurements were carried out at Elandsfontein measurement
station, on the eastern Highveld approximately 150 km east of Johannesburg
in South Africa throughout 2010. The height of the planetary boundary layer
(PBL) top was continuously measured using a Raman lidar, PollyXT
(POrtabLe Lidar sYstem
eXTended). High atmospheric variability together with a large
surface temperature range and significant seasonal changes in precipitation
were observed, which had an impact on the vertical mixing of particulate
matter, and hence, on the PBL evolution. The results were compared to
radiosondes, CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization)
space-borne lidar measurements and three atmospheric models that followed
different approaches to determine the PBL top height. These models included
two weather forecast models operated by ECMWF (European Centre for
Medium-range Weather Forecasts) and SAWS (South African Weather Service), and
one mesoscale prognostic meteorological and air pollution regulatory model
TAPM (The Air Pollution Model). The ground-based lidar used in this study
was operational for 4935 h during 2010 (49% of the time). The PBL
top height was detected 86% of the total measurement time (42% of
the total time). Large seasonal and diurnal variations were observed between
the different methods utilised. High variation was found when lidar
measurements were compared to radiosonde measurements. This could be
partially due to the distance between the lidar measurements and the
radiosondes, which were 120 km apart. Comparison of lidar measurements to
the models indicated that the ECMWF model agreed the best with mean relative
difference of 15.4%, while the second best correlation was with the SAWS
model with corresponding difference of 20.1%. TAPM was found to have a
tendency to underestimate the PBL top height. The wind speeds in the SAWS
and TAPM models were strongly underestimated which probably led to
underestimation of the vertical wind and turbulence and thus underestimation
of the PBL top height. Comparison between ground-based and satellite lidar
shows good agreement with a correlation coefficient of 0.88. On average, the
daily maximum PBL top height in October (spring) and June (winter) was
2260 m and 1480 m, respectively. To our knowledge, this study is the first long-term study of PBL top heights and PBL growth rates in South Africa