Review of data on heavy metals in ambient air in Australia

Technical Report No. 3
Environment Australia, May 2002
ISBN 0 6425 4781 5

2. Sources of heavy metals in Australia

Metals occur in air in different phases, as solids, gases or adsorbed to particles having aerodynamic sizes ranging from below 0.01 micrometres (µm) to 100 micrometres and larger. Two major categories of particulate matter are fine particles and coarse particles. Fine particulate matter (FPM) comprises particles with aerodynamic diameters of 2.5 µm or less. They are emitted from fossil fuel combustion, motor vehicle exhausts (including diesel) and wood burning. Several toxic metals, including arsenic, cadmium, lead, zinc, antimony and their compounds are associated with FPM in ambient air (US EPA, 1996). This is important from a public health perspective since these fine particles are respirable and can be transported over very long distances.

PM10 is the mass concentration of particulate matter having aerodynamic diameters less than 10 µm. In this report, particles with aerodynamic diameters between 2.5 µm to 10 µm will be referred to as 'coarse particles'. Coarse particles arise mainly from road dust, fugitive dust, sea spray, tyre and asphalt wear, and biological sources such as bacteria, pollens, fungal spores and plant/insect fragments. Total Suspended Particles (TSP) have diameters up to and above 50 µm. Standards for ambient levels of PM10 in Australia are set in the NEPM for Ambient Air Quality (NEPC, 1998).

Heavy metals such as iron (Fe), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), manganese (Mn), copper (Cu), selenium (Se), barium (Ba), gallium (Ga), caesium (Cs), europium (Eu), tungsten (W) and gold (Au) exist in both coarse and fine fractions in ambient air (VIC EPA, 1998a). Calcium (Ca), aluminium (Al), titanium (Ti), magnesium (Mg), scandium (Sc), lanthanum (La), hafnium (Hf) and thorium (Th) exist predominantly in the coarse fraction (Klee, 1984). Metals such as arsenic (As), cadmium (Cd), gallium (Ga), molybdenum (Mo), lead (Pb), antimony (Sb), selenium (Se), tungsten (W) and zinc (Zn) enrich the fine fraction of particulate matter (Finlayson-Pitts and Pitts, 1986).

The National Pollutant Inventory (NPI) is the best repository for data on estimated metals emissions and their sources in Australia (NPI, 1999 & 2001). The NPI was developed as a National Environment Protection Measure through the National Environment Protection Council (NEPC). The NPI aims to provide the community, industry and governments with information on the types and amounts of certain pollutant substances being emitted to the land, air and water in Australia. Emissions data for the first NPI reporting year, 1 July 1998–30 June 1999, which were available on the Internet, were used in this project for determining the sources of heavy metals emissions in Australia (NPI, 1999). The first year data have been replaced on the Internet with data for the second year of reporting, 1 July 1999 to 30 June 2000 (NPI, 2001).

NPI air emissions data for heavy metals have been presented here in two groups. The first group comprised emissions from larger facilities (reporting facilities), which were dealt with as individual emission sources (point sources). The reporting facilities were required to report the emissions of a substance if they exceeded any one of five stipulated threshold categories for that substance. A typical threshold category for metals was 10 tonnes per annum. The second group of heavy metals emissions reported here comprised emissions from specific smaller industrial and domestic sectors (sub-threshold reporting facilities) and mobile sources such as motor vehicles, aeroplanes and ships/boats. These diffuse emissions were grouped together as aggregated sources, called area-based emissions. Individually, they may only provide a small contribution to the emissions inventory, but the overall contribution of these emissions to the inventory can be significant (EA, 1999).

The following metals and their compounds have emissions data in the NPI database: antimony (Sb), arsenic (As), beryllium (Be), cadmium (Cd), chromium(III) (Cr(III)), chromium(VI) (Cr(VI)), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn). There are also emissions data specifically for magnesium oxide fume, nickel carbonyl and nickel subsulphide.

2.1. Emissions from NPI reporting facilities

The reporting facilities provided estimates of their emissions to their State or Territory environment authority, which compiled the emissions data before forwarding to Environment Australia. Environment Australia placed the emissions inventory data in the NPI database.

Table 1: Reporting facilities responsible for emissions of heavy metals and their compounds into the atmosphere
Alumina production Metal ore mining
Basic iron and steel manufacturing Mining
Basic non-ferrous metal manufacturing Nickel ore mining
Bauxite mining Non-ferrous metal casting
Beer and malt manufacturing Oil and gas extraction
Black coal mining Organic industrial chemical manufacturing
Bread manufacturing Paint manufacturing
Brown coal mining Paper product manufacturing
Ceramic product manufacturing Paper stationery manufacturing
Ceramic tile and pipe manufacturing Petroleum product wholesaling
Chemical product manufacturing Petroleum refining
Clay brick manufacturing Plywood and veneer manufacturing
Copper ore mining Port operators
Corrugated paperboard container manufacturing Pulp, paper and paperboard manufacturing
Electricity supply Rail transport
Food manufacturing Road and bridge construction
Glass and glass product manufacturing Sewerage and drainage services
Gold ore mining Silver-lead-zinc ore mining
Hospitals (except psychiatric hospitals) Steel pipe and tube manufacturing
Inorganic industrial chemical manufacturing Sugar manufacturing
Iron and steel casting and forging Waste disposal services
Iron ore mining Water transport terminals
Laundries and dry-cleaners  
Medicinal and pharmaceutical product manufacturing  

Each reporting facility type had an assigned Australian and New Zealand Standard Industrial Classification Code (ANZSIC). When annual metals emissions data in the NPI database were extracted against these codes, for each State or Territory, up to 46 types of facilities were found to be responsible for emitting one or more of the 19 heavy metals and their compounds into the atmosphere. The 46 facilities are listed in Table 1.

The total expected emissions in kilograms per annum of each metal from the different categories of reporting facilities is shown in Appendix A, for the period July 1998 to June 1999, which was the first year of reporting emissions to the NPI. Data for this first year of reporting could have considerable errors for the following reasons: several industries did not report all of their emissions, as there were no penalties for not reporting to the NPI during the first two years of reporting; some companies were learning the methods of estimating emissions during this period, and a few industries reported emissions for less than one year, sometimes for only 30 days. For this report, emissions data reported for less than one year were extrapolated to 365 days by using a simple ratio. Limitations to data accuracy due to partial or non-reporting of emissions should be noted: there is a disclaimer on the NPI Internet website on the accuracy of the data in the database (NPI, 2001).

The data in Appendix A show that electricity supply contributed substantially to the reported emissions of antimony (Sb), cadmium (Cd), cobalt (Co), lead (Pb) and mercury (Hg) and their compounds. Electricity supply contributed to 31% of the total Sb, 42% of the total Cd, 38% of the total Co and 43% of the total Hg and compounds emitted by all reporting facilities. Metal ore mining also contributed substantially to the reported emissions of beryllium (93%), chromium(VI) (26%), copper (60%), manganese (~100%), nickel (74%) and their compounds. Silver-lead-zinc ore mining was a major contributor to reported emissions of cadmium (20%), lead (49%), and zinc (91%) and their compounds. Other facilities that contributed to a large fraction of reported emissions of antimony and compounds were sewerage and drainage services (32%) and hospitals (36%). Organic industrial chemical manufacturing contributed to a large fraction of reported emissions of magnesium oxide fume (71%) and selenium compounds (40%); gold ore mining contributed to reported arsenic and compounds emissions (14%) and petroleum refining was a major contributor to reported chromium(III) compounds emissions (85%). Other contributors to reported emissions of chromium(VI) compounds were black coal mining (19%) and basic non-ferrous metal manufacturing (19%). Alumina production contributed to reported mercury and compounds emitted (31%). Clay brick manufacturing was a major contributor to reported nickel carbonyl emissions (94%). Finally, all the nickel subsulphide emissions reported were from glass and glass product manufacturing.

The total reported emissions of each metal in the jurisdictions were compared in the bar graphs in Figure 1. Only arsenic, lead and manganese and compounds had total reported emissions of 10,000 kg/year (10 tpa) or over, during 1998/1999, from any of the jurisdictions. South Australia had the largest estimated arsenic emissions from point sources in Australia, followed by WA. Most of the arsenic emissions were from mining operations and power generation. Queensland had the highest estimated lead emissions that were reported from point sources, followed by WA. A mining operation was responsible for most of the lead emissions from reporting facilities in Queensland. This facility reported emissions for only one month, thus an annual lead emission of 15 tonnes was estimated from 1.2 tonnes reported for June 1999. Major lead emissions in WA were from gold mining operations and power generation. In the 1999/2000 NPI reporting year, 28 tonnes of lead were reported from a single source in SA (NPI, 2001); this emission appears to have been omitted in the previous year.

Figure 1: Heavy metals emissions from NPI reporting facilities in Australian states and territories (total emissions are kg/year for 1998/99)

Figure 1a: Heavy metals emissions from NPI reporting facilities in Australian states and territories (total emissions are kg/year for 1998/99)
Figure 1b: Heavy metals emissions from NPI reporting facilities in Australian states and territories

A single mineral mining operation was responsible for most of the manganese emissions (320 tpa) in the Northern Territory (NT), accounting for about 75% of all metals emissions from reporting facilities in Australia. The total manganese emissions reported in the NT during the second year of reporting in 1999/2000 was only 5 tonnes (NPI, 2001); the large manganese emission from the previous year was not reported this time.

Metals with total reported emissions in the jurisdictions, of about 1,000 kg/year (1 tpa) or over in 1998/1999, were arsenic and compounds (NSW, Queensland, WA and SA), chromium(VI) compounds (NSW, Queensland, WA and NT), cobalt and compounds (Queensland and WA), copper and compounds (NT), lead and compounds (NSW, Queensland and WA), manganese compounds (NT), mercury and compounds (WA), nickel and compounds (VIC, WA and NT) and zinc and compounds (NT). Data for the total emissions of each metal and their compounds, for the various jurisdictions, are shown in the table in Appendix B. The highest reported metal emission from facilities in the ACT, Tasmania, NSW, and Queensland was lead and compounds. The highest in the Northern Territory was manganese, arsenic was the highest in SA and WA, and nickel the highest in Victoria.

The amount of metals emitted is not necessarily related to a greater health or environmental implication, as it is the substance's toxicity in conjunction with the amount that determines environmental and human health effects (NPI, 1999).

2.2. Emissions from NPI area-based sources

Area-based emissions into various airsheds were estimated and aggregated by the State and Territory environment authorities and sent to Environment Australia to be compiled into the NPI. Area-based emissions typically arise from domestic and other anthropogenic activities, such as domestic heating, lawn mowing, domestic solvent use, smoke from prescribed burning, service station vapour losses and mobile source activities (use of motor vehicles, aeroplanes and marine craft). Data from these sub-reporting facilities' emissions were compiled by the jurisdictions either directly from the facilities by questionnaire or estimated from reported US EPA emissions factors. For mobile sources such as motor vehicles, aggregated emissions were determined from motor vehicle activity (vehicle kilometres travelled), the road network (location of roads, road type, usage and congestion), fleet characteristics (age and composition) and typical emission factors. The emissions from the metropolitan transit rail, tourist railways and passenger and freight services, marine craft within the region were estimated on either a fuel consumption or activity basis (VIC EPA, 1998b).

The 1998/99 NPI database had area-based emissions data for Adelaide (SA), Hobart (Tasmania), Kalgoorlie (WA), Perth (WA), Port Phillip Region (Victoria), Sydney-Wollongong-Newcastle (NSW) and SE Queensland airsheds. At the time of compiling this data, Alice Springs and Darwin data were not in the NPI database. However, available data for these two airsheds (provided by the NT Government) have been included in this report.

Area-based emissions sources/activities, which were found to emit heavy metals into the airsheds are listed in Table 2. Up to 31 source/activity types were identified as heavy metals-emitters. The estimated amounts of metals emitted from these area-based sources in the nine airsheds during 1998–1999 are summarised in Appendix C. The major area-based emission sources were found to be motor vehicles, service stations, solid fuel burning (domestic) and burning/wildfires. Motor vehicles and service stations were predominantly responsible for the emissions of lead and compounds – the most emitted heavy metal (602 tpa) from the area-based sources. Other major lead emission sources were aeroplanes, fuel combustion, glass (manufacturing) and lawn mowing. Zinc and compounds emissions were the next dominant area-based metal emissions (347 tpa). A large emission of zinc and compounds from domestic solid fuel burning was estimated for Hobart. This reported zinc emission was much higher than emissions from similar sources estimated for the other airsheds. Burning/wildfires and glass (manufacturing) were also major zinc emissions sources.

Table 2: Area-based sources responsible for emissions of heavy metals and their compounds into the atmosphere
Aeroplanes Backyard incinerators
Bakeries Barbeques
Boating/shipping Burning/wildfires
Cement Cigarettes
Crematoria Dry cleaning
Electroplating Food, beverage and tobacco
Fuel combustion Gaseous fuel burning (domestic)
Glass Health services
Landfill Lawn mowing
Liquid fuel burning (domestic) Motor vehicle refinishing
Motor vehicles Non-ferrous foundries
Paved/unpaved roads Petroleum and coal product manufacturing
Pulp and paper Railways
Recreational boating Service stations
Solid fuel burning (domestic) Structural metal product manufacturing
Timber and wood  

Other dominant metals emitted from area-based sources were arsenic and compounds (1.7 tpa), chromium(VI) compounds (3.0 tpa), manganese and compounds (4.2 tpa), mercury and compounds (1.0 tpa) and nickel and compounds (8.2 tpa). The major sources of arsenic were aeroplanes and fuel combustion. Chromium(VI) was mainly emitted from aeroplanes, glass (manufacturing), motor vehicles and solid fuel burning (domestic). The major sources of manganese were backyard incinerators, burning/wildfires, motor vehicles, paved/unpaved roads, gaseous fuel burning (domestic), liquid fuel burning (domestic) and solid fuel burning (domestic). Major mercury sources were fuel combustion and glass (manufacturing), and major nickel sources were boating/shipping and fuel combustion.

The total of the estimated area-based emissions for each of the metals and their compounds, for the different airsheds, are compared in the bar graphs in Figure 2. Lead and compounds emissions were above 1 tpa for all the airsheds. Port Phillip Region, SE Queensland and Sydney-Wollongong-Newcastle airsheds had estimated lead emissions of over 100 tpa. Area-based zinc and compounds emissions from Darwin were over 10 tpa, and for Tasmania they were over 100 tpa. Emissions from domestic solid fuel burning were responsible for the high levels of zinc and compounds estimated in Tasmania. Emissions of arsenic and compounds, chromium(VI) compounds, manganese and compounds and nickel and compounds were estimated to be over 1 tpa in the Port Phillip Region airshed. Other emissions over 1 tpa were zinc and compounds from SE Queensland airshed, manganese and compounds from Darwin airshed and nickel and compounds from Perth airshed.

Figure 2: Heavy metals emissions from NPI area-based sources in Australian airsheds (emissions are in kg/year for 1998/99)

Figure 2a: Heavy metals emissions from NPI area-based sources in Australian airsheds (emissions are in kg/year for 1998/99)
Figure 2b: Heavy metals emissions from NPI area-based sources in Australian airsheds (emissions are in kg/year for 1998/99)
Figure 2c: Heavy metals emissions from NPI area-based sources in Australian airsheds (emissions are in kg/year for 1998/99)

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