Air-quality performance is measured using indicators of standard releases to the environment considered to be pollutants. These indicators include different types of air pollutants, namely greenhouse gas and non-greenhouse gas emissions that are controlled via international conventions, national laws and local regulations, which can include the environmental authorisations of a reporting organisation’s operations.
Greenhouse gas emissions are believed to be the main cause of climate change and are governed by the United Nations Framework Convention on Climate Change and the Kyoto Protocol. The main greenhouse gas emissions from our operations are covered under the “Energy and climate change” section on page 102.
Other potentially significant air emissions that are relevant to our operations include ozone-depleting compounds, persistent organic compound, sulfur dioxide (SO 2 ), particulate matter and total dust fallout.
In accordance with the Montreal Protocol on substances that deplete the ozone layer, ozone-depleting compounds have been phased out at all major installations (for example, in ventilation units) across our operations. An assessment of minor installations (for instance, single air-conditioning units) has shown that there are only negligible quantities of ozone-depleting compounds present at these installations. All our mining refrigerants are ozone friendly, including small air-conditioning applications consisting of either ammonia or R134a, both of which are environmentally acceptable replacement compounds used
in existing medium- and low-temperature refrigeration.
The Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty that aims to eliminate or restrict the production and use of these pollutants. The convention requires that equipment containing polychlorinated biphenyls (PCBs) be phased out by 2025. The persistent organic pollutants that may pose a risk are PCBs that are present in some transformers and capacitors. This equipment is continually maintained and serviced to ensure that all reasonable steps are taken to prevent leaks and contain any spillages. Any PCBs recovered from such equipment in the interim is treated and will be eliminated by 2025 to ensure compliance with the convention.
Another potential risk is the emission of dioxins and furans from the Precious Metals Refinery (PMR) incinerator stack. The incinerator is fed with PMR general and process-specific wastes. The incineration is not a continuous process and control measures are
in place to keep the emission levels to a minimum.
Sulfur dioxide and particulate emissions
The direct sulfur dioxide (SO 2 ) emissions from the sources owned and controlled by Amplats are at the Waterval, Mortimer and Polokwane smelters, with minor contributions from the refineries.
Total SO 2 emissions (stack and fugitives) for the refineries and smelters were 20.08 kt in 2012, which is higher than the 18.78 kt emitted during 2011. The increase is attributed mainly to emissions from the Mortimer Smelter. The SO 2 emissions at the smelter in 2011 were 3.70 kt and increased to 8.18 kt in 2012. The 2012 emission rate is higher than in 2011, as the smelter was shut down for an extended period in 2011 for an upgrade to the furnace. An average of 22.3 t/d was emitted in 2012, against the target of 24 t/d.
Total SO 2 emissions from Waterval complex for 2012 was 5.44, which was lower than the 2011 result of 7.90 kt. An average of 14.9 kt was emitted in 2012, against the target of 20 t/d.
SO2 emissions at the Polokwane Smelter decreased, from 7.20 kt in 2011 to 6.46 kt in 2012, as the result of the blending of Merensky and UG2 concentrates, and stability of the furnace operation. On average, 17.23 t/d were emitted, against the target of 25 t/d.
SO2 emissions from RBMR and PMR remain low.
Monitoring of ambient air quality
Direct and indirect emissions result in ambient air pollution concentrations that vary spatially and temporarily depending on changes in meteorology and topography. Sources of ambient air emissions can include vehicle fumes, industrial gases and domestic coal burning. As a result, the South African Government has published a gazette to regulate national standards for ambient air quality. The standards set the limits for ambient concentrations of priority pollutants (sulfur dioxide, nitrogen dioxide, particulate matter, ozone, benzene and carbon monoxide). Ambient-air real-time monitoring is conducted in the Waterval, Mortimer and Polokwane smelter areas, owing to potential impact of sulfur dioxide and particulate matter.
The Rustenburg air-quality-monitoring network comprises eight stationary ambient monitoring stations, while the Polokwane Smelter has six stationary ambient monitoring stations and the Mortimer Smelter has one ambient monitoring station. The ambient monitoring stations are equipped to measure sulfur dioxide (SO 2 ), particulate matter (PM 10 ) and meteorological data from all sources in the region.
Comprehensive data sets are available for all ambient monitoring stations; the data sets for the eight stations in Rustenburg are shown below.
There were no exceedances of the SO 2 annual average standard of 50 µg/m3 at any station during 2012. There were no exceedances of the national SO 2 daily standard (125 µg/m3) and only 36 exceedances of the hourly standard (350 µg/m3). This represents a reduction against data from 2011 (when 83 exceedances of the hourly standard were recorded) and indicates a general reduction over the previous five years (with 189 measured exceedances of the hourly standard and six of the daily standard measured in 2008).
There was a significant reduction in the number of measured PM 10 exceedances over the last year. Only two stations measured exceedances of the PM 10 daily standard 120 µg/m3, namely Klipfontein (2) and Paardekraal (7) compared with a total of 42 exceedances measured over the same period in 2011. Two stations (Mfidikwe and Paardekraal) exceeded the DEAT annual average (50 µg/m3) owing to higher readings during the winter months, when weather conditions are especially dry and there are increases in coal burning and wind-blown dust.
SO 2 data captures for 2012 at the monitoring stations were lower than in 2011, as only three of the eight stations achieved data capture of above 85%. Overall, PM10 data
capture showed a slight decrease from 2011 percentages.
The main reason for the decrease in data capture for 2012 is the result of a number of PM 10 and SO 2 analysers that developed faults over the course of the year. Some PM 10 data was lost because of problems associated with analyser filter tapes. Loss of both SO 2 and PM 10 data was associated mainly with analyser malfunctions and power failure throughout the year. The focus on 2013 will be on replacing old equipment; increasing the maintenance frequencies on the stations; and improved collaboration and communication between contractors for the earlier detection and more rapid resolution of faults.
On 7 December 2012, Government Notice 1007 was published on the Draft National Dust Control Regulations for South Africa. The total dust deposition methodology that is being proposed aligns with the current practice at our operations. Currently, total dust fallout is determined at our operations in accordance with the ASTM D1739 standard test method for the collection and measurement of dust fallout. Dust fallout buckets are used and samples are analysed by external laboratories. The gravimetric results are compared with the proposed guidelines for dust deposition as described in the SANS 1929: 2005, Edition 1.1. These guidelines set four levels of dust fallout rates (measured in milligrams per cubic metre per day), namely: residential, industrial, action and alert rates.
The main sources of dust within mining operations are unpaved haul roads, opencast activities and tailings storage facilities. All sites showed a slight increase in dust levels at specific sampling points between 2011 and 2012. This is the result of localised sources of dust during increased transport activities on the unpaved roads; remining activities at tailings storage facilities; increased activities near crushers for waste rock crushing; and high wind speeds experienced in 2012. Dust suppression measures are implemented and maintained at sites with a high dust potential.