INTRODUCTION
Air pollution in Greater Johannesburg differs according to area. In poor residential
areas like Soweto, Orange Farm and Alexandra, coal and wood burning for space heating and
cooking is the major source of smoke and SO2 pollution. In urban areas around
the CBD and higher income areas such as Sandton, Randburg, Melville and Southgate, vehicle
emissions and dust from mines (for the southern areas) cause pollution. In the inner city,
CO and hydrocarbon levels are especially high in winter. In urban areas and the inner
city, PM10 (particulate matter smaller than 10ug) and TSP (Total Suspended Particulates)
levels are also high due to exhaust emissions and re-suspended dust from vehicles. All
pollution levels rise in the winter because pollutants from vehicle emissions, coal fires,
industries and mining areas are trapped close to the surface by temperature inversion
layers. Circulation patterns over South Africa in the winter also do not disperse
pollutants in a wavelike fashion as in summer.
A selected measurement of
air pollution has been done in the former Johannesburg City Council area.
ANALYSIS OF AIR POLLUTION ACCORDING TO MAJOR SOURCES
- The worst affected area is around the Johannesburg CBD, which
includes the industrial areas from Heriotdale in the east to Industria North and Industria
West in the west. These industries also lie mostly along the main rail and road commuter
ways, which also experiences pollution from vehicle emissions. Traffic also converges in
the CBD from the rest of Greater Johannesburg during the daytime. Morning and afternoon
pollution levels along major roads coming into and leaving the CBD are consequently bad,
with high primary (NO, CO and hydrocarbons) and secondary (ozone and NO2)
pollutant levels.
The Newtown monitoring
station that covers the CBD shows an increase in average annual ozone levels from
0,012 to 0,013 ppm, as well as CO levels from 2,33 to 2,51 ppm during 1995/1996. A rise in
ozone levels of 2-3 ppb per annum is estimated in the inner city. Carbon monoxide (CO)
levels at Newtown is also much higher than at the other three monitoring
stations, mainly due to vehicle emissions, and may exceed the national guideline
during winter. Newtown further shows a decrease in NOx, NO2 and NO
annual averages from 1995-1996 (GJMC Photochemical Smog Monitoring Program, 1996). Hourly
averages of non-methane hydrocarbons at Newtown show an increase in winter. Levels rose
from 0,4 ppm (which equals the national average hourly guideline) in January 1999, to 0,7
ppm in February, then 0,21 ppm in March, 0,34 ppm in April, 0,46 ppm in May, 0,92 ppm in
June and 0,54 ppm in July. This is due to the increase in coal fires, as well as seasonal
circulation patterns and the temperature inversion level, which occur in autumn and
winter.
Pollution in the CBD is further affected by wind
blown dust from the mining belt, which increases TSP levels. Dust levels, measured as PM10
(particulate matter smaller than 10 ug/m3), exceeded the average daily
guideline at Newtown once in February 1999, twice in April, 15 times in May, 10 times in
June and 4 times in July 1999. This underlines the fact that winter circulation patterns
in South Africa do not disperse pollutants due, in addition, to the role of inversion
layers. The prevailing wind direction on the reef is north- northwest, especially in the
winter time. That is why mine dumps are often recycled from the southeast, eg Robinson
Deep Mine Dump in Booysens/Springfield, to protect the industries and people in the
Booysens area (Weather Bureau, 1997). The air pollution problems are also influences by
the large number of unrehabilitated mine dumps present in the area. This results in large
amounts of dust circulating in the atmosphere. The highveld climate further exacerbates
the problem, due to the temperature inversions experienced during winter, which
concentrate polluted air and keep it close to the ground (Walmsley, 1997).
- To the south of the CBD through to Southgate, pollution comes mainly
from the mining belt, as well as the large industrial areas such as City Deep, Booysens,
Electron, Tulisa Park and Aeroton. The City Deep (industrial) monitoring station shows the
second highest levels of CO after Newtown. Vehicle emissions and the burning of rubbish
also affects this area. At the South Hills (suburban / residential) monitoring station, ozone levels are much
higher than at the other stations, and exceeds the national hourly average of 0,12 ppm
during winter. The burning of petroleum gas, as well as other fossil fuels increases
primary and secondary (ozone) pollutants. The industries surrounding the area worsen the
situation.
Annual average ozone levels
decreased from 1984-1986 from 0,037 ppm to 0,016 ppm, then steadily increased to 0,033 ppm
in 1990, and has since decreased and levelled out around 0,028 ppm. Annual average NO2
levels at South Hills dropped from 0,056 ppm in 1984 to 0,028 ppm in 1985, and have
since mainly fluctuated around this level. Annual average SO2 levels have been
fluctuating around 0,006 ppm.
- Air quality in the whole area surrounding Soweto is bad, where
excessive amounts of coal is being burned. The worst affected areas are Diepkloof,
northwest of Soweto, the whole area from Devland to Nancefield southeast of Soweto, where
industries and informal settlements play a role, and the informal settlements from
Klipspruit to Protea South. Use of energy rises here from June to September, and
concentrations are only decreased after the spring rains and when summer wind circulation
patterns return. This explains why the national guideline for particulate matter (mostly
smoke) is exceeded 20-30% of the time (in the winter months) in these coal-burning
residential areas. In Soweto, measurements of 800 - 1 800 ug/m3 for particulate respirable matter have been taken
during winter months. An hourly average of 1.17 ppm of SO2 have also been
measured in this area during this season (Sithole et.al., 1991 in Walmsley,
1997). Dust from untarred
roads, refuse burning and bad odours from the Goudkoppies Landfill site and informal
industries also contribute to air pollution.
According to UNEP (1996) the coarse fraction of
particulate matter (15>PM<2,5um) is the highest at lowest elevation sites and
informal shanty areas in Soweto, where population densities are the highest and coal
burning is excessive. Levels are the highest at Dhlamini, Jabavu and Chiawelo, which are
at low to middle elevations, and low to middle socio-economic levels. Levels are the
lowest at Diepkloof and Meadowlands to the north, which have a middle-high elevation and
middle to high socio-economic status (Sithole et al, 1994, in UNEP, 1996). The particulate
matter is derived from coal burning, dust, burning of garbage (lead, nickel, copper,
zinc), vehicles (lead), biomass burning and secondary production of sulphates.
- In the formal residential areas of Lenasia and Ennerdale, and the
informal settlements of Zakariyya Park, Vlakfontein, Elandsfontein and Lawley, pollution
comes mainly from dust from untarred roads, rubbish and coal burning, and light
industries. The worst affected areas are the informal settlements of Zakariyya Park,
Thembelihle, Vlakfontein and Hospital Hill south of Lenasia, where excessive coal burning
takes place. The Grasmere, Finetown and Weilers Farm areas east of Ennerdale, also burn
excessive amounts of coal, and also lie next to the N1 and other major roads where vehicle
emissions play a role. In the southern most part of the metropolitan area pollution is bad
at the Poortjie settlement and to the east of Orange Farm. Excessive amounts of coal
burning, vehicle emissions and dust from gravel roads and open land or agricultural
activities are the causes.
In the areas to the north of Soweto, dust from gravel and mine dumps
(especially Doornkop), roads, smoke and CO from coal burning pollute the air. West of
Roodepoort the Roodepoort West industrial area, CBD activities, dust from mine dumps, and
excessive coal burning in informal settlements contribute to bad air pollution levels.
- In the Randburg area pollution levels in the formal residential areas
are much lower due to the minimal use of coal. Problem areas exist in the Randburg and
Sandton CBD’s mostly due to vehicle emissions, light industries and commercial
activities. The Wynberg / Kew industrial area west of Alexandra causes pollution together
with the informal settlements in the area, where moderate to excessive amounts of coal is
used, and thus increases SO2 levels especially in the winter months. In the
northern parts of the metropolitan area the informal settlements of Diepsloot, Rietvallei
and Zevenfontein use excessive amounts of coal which causes pollution. The Northern Works
(sub-rural) monitoring station at the Northern sewage works, shows a slight increase in
annual levels of NOx (0,015-0,024 ppm), NO2 (0,008-0,013 ppm) and NO
(0,002-0,012 ppm) from 1985-1989, whilst a decrease in ozone (0,033-0,015 ppm) and
hydrocarbons (0,329-0,283 ppm) were observed (GJMC Photochemical Smog Monitoring Program,
1996).
CONCLUSION AND RECOMMENDATIONS
- The major sources of air pollution over Greater Johannesburg are
vehicle emissions, dust from mine dumps and untarred roads, excessive burning of coal
especially in informal
settlements, industries and CBD activities.
- Very little and incomplete information exists on air pollution and
only limited monitoring is done.
- The 1950-dust pollution problem from sand and slimes dumps was only
partially solved due to the planting of surface covers like indigenous grasses and reeds.
New mine dumps and the reprocessing of slimes, are aggravating the problem.
- Pollution from combustion of fossil fuels in vehicles is a problem
that will only get worse due to the rising prices of new vehicles, and the increasing
amount of old and poorly maintained vehicles on roads. Increased use of private vehicles,
because of inadequate and inefficient public transport, will also increase air pollution.
REFERENCES
GJMC, 1996: Photochemical Smog Monitoring Program.
Greater Johannesburg Metropolitan Council : Johannesburg.
UNEP 1996: Air Quality Management and Assessment
Capabilities in 20 Major Cities. UNEP: London.
Walmsley Environmental Consultants 1997: GJTMC
Integrated Metropolitan Development Plan - Report No. W262. WEC: Rivonia.
Weather Bureau 1999: Johannesburg
Airport Data.Weather Bureau: Pretoria. |
