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Appendix A: Air Pollution Emissions

An assessment of the amount of PM10 from different sources across the whole of New Zealand was carried out in 1998 (NIWA, 1998). Sources included in the national emission inventory were broken down into the following categories: area based emissions (predominantly domestic home heating, small scale boilers, lawn mowing, off-road vehicles, open burning), transport, industry and natural emissions. The methodology was less complex than the majority of the regional emissions assessments, with estimates based on broader assumptions. For example, emissions from domestic home heating were assessed based on the results from existing inventories (Auckland and Christchurch for the North and South Islands respectively) and scaled based on population for each area.

The transport emissions assessment in the Total Emission Inventory for New Zealand estimates annual PM10 motor vehicle emissions of 197, 694, 317, 71, 146, 225 and 368 t/year for North Shore City, Auckland City, Manukau City, Wellington and Christchurch respectively. Collectively, estimates for the Auckland area (excluding Rodney District and Franklin) total 1,425 t/year or around 3.9 t/day, compared to around two tonnes per day given in the 1996 Auckland Regional Emission Inventory (includes parts of Franklin and Rodney). Results from the national inventory assessment for Wellington (around 0.6 t/day) were relatively low compared to the regional estimates for 1997 of 1.2 tonnes. For Christchurch estimates were a bit closer with around 1 t/day for the 1996 national assessment compared to around 0.8 t/day for the 1996 motor vehicles assessment.

The comparability of the total PM10 emission estimates in the national emission inventory assessments to the regional assessments varies with area. In Wellington estimates of around 2,500 tonnes per year for the national emission inventory compare to around 1,500 tonnes in the Wellington region emission inventory.

In Hamilton annual estimates of around 590 tonnes of PM10 from the regional assessment compare to around 578 in the national emissions inventory. In Taupo, regional assessments indicate around 400 tonnes of PM10 are likely to compare to an estimated 249 tonnes in the national inventory assessment. In Auckland, the regional assessment for 1993 indicates annual emissions for TSP of less than 6,000 tonnes per year. This is similar to the national inventory assessment when the areas of Franklin and Rodney are excluded from the assessment. However, if these areas are included, the national assessment indicates around 9,000 tonnes of PM10 per year. The regional data includes parts of these areas.

For Christchurch, the national emissions inventory estimate of 3,086 tonnes of PM10 per year is greater than around 2000 estimated based on the Christchurch emission inventory 1996 back-cast. A better comparison is observed in Nelson with regional estimates of around 300 tonnes per year compared to 455 in the national emissions inventory.

The methodologies used to calculate these various inventories are different. The national inventory was completed using general information available from statistics, whereas the regional inventories are calculated using more specific tools such as local surveys. However it is not possible to use regional inventories here since (a) they are compiled using different categories in different regions (there is no standard), and (b) not all regions have inventories.

Table A1: Breakdown of PM emissions

PM

Domestic

Industry

Transport

Auckland – wintertime TSP 1995

67

24

9

Taupo – wintertime PM10 2000

30

64

6

Hamilton – wintertime PM10 2001

90

1

9

Bay of Plenty – annual particles 1997

52

31

17

Taranaki – annual PM10 1998

55

16

29

Wellington – wintertime PM10

57

18

25

Timaru – wintertime PM10 2001

91

3

6

Christchurch – wintertime PM10 1999

80

10

10

Waimate – wintertime PM10 1997

97

2

1

Nelson – wintertime PM10 2001

83

13

4

Dunedin – wintertime PM10 1999

61

37

2

Mosgiel – wintertime PM10 1999

53

47

0

Balclutha – wintertime PM10 1999

93

6

1

Northland – winter daytime PM10 1996–2000

55

34

11

Source: Emission Inventories in New Zealand.

Table A2: Comparison of PM10 emissions estimates for different regions of New Zealand

 

Domestic
kg/day

Mobile sources
kg/day

Industry
kg/day

Total
kg/day

Alexandra

264

4

114

382

Arrowtown

120

0.5

14

135

Balclutha

250

4

17

271

Clyde

63

0.5

8

72

Cromwell

127

1

48

176

Milton

174

2

43

219

Mosgiel

325

3

290

618

Oamaru

870

17

236

1,123

Queenstown

586

31

143

760

Wanaka

147

1

68

216

Dunedin

3,174

101

1,933

5,208

 

Domestic heating
kg/day

Motor vehicles
kg/day

Industry

kg/day

Other domestic
kg/day

Other mobile
kg/day

Total
kg/day

Christchurch

7,929

991

1,027

   

9,947

Rangiora

543

8

61

   

612

Kaiapoi

334

12

5

   

351

Ashburton

897

18

106

   

1,021

Waimate

285

1

6

   

292

Timaru

1,124

61

41

   

1,226

Hamilton

3,600

371

39

   

4,010

Taupo

409

77

866

   

1,352

Tokoroa

1,232

58

2,866

   

4,156

Nelson

1,486

78

264

85

 

1,912

Northland

3,028

633

1,915

103

 

5,679

Auckland

18,900

2,000

7,100

300

700

29,000

Wellington

6,160

1,200

2,000

180

490

10,030

 

Domestic
t/year

Mobile sources
t/year

Industry
t/year

Burn-offs
t/year

Total
t/year

Taranaki

490

251

138

 

879

BOP

1,110

455

849

323

2,737

Gisborne

151

58

340

210

759

Figure A1: Relative contribution of sources of particles within New Zealand

 See figure at its full size (including text description).