Sulphur dioxide levels in air

Waikato Regional Council has measured sulphur dioxide (SO₂) levels in Hamilton at the Ohaupo Road (Blood bank) monitoring station and in Tokoroa at the Billah Street reserve monitoring station.

Monitoring sites for this specific indicator are marked in blue below:

(Map source: LAWA).

Sulphur dioxide concentrations were measured continuously over a six month period and logged as 10 minute averages. Hourly and 24 hour average concentrations were derived from the 10 minute data.

Sulphur dioxide was monitored in Hamilton at Waikato Regional Council's Ohaupo Road (Waikato Hospital site adjacent to the Bloodbank Service) monitoring site from 1 March 2012 to 31 August 2012. This is classified as a combined Traffic/Industrial monitoring site.

Sulphur dioxide was monitored in Tokoroa at Waikato Regional Council's Billah Street reserve monitoring site from 1 December 2017 to 31 May 2018. This is classified as a residential monitoring site.

Concentrations of sulphur dioxide were measured using an Ecotech EC 9850 SO₂ analyser. This is a continuous analyser that measures sulphur dioxide using gas phase fluorescence. Operational aspects of the sulphur dioxide monitoring including maintenance, calibration and quality assurance were carried out by Watercare Ltd for Waikato Regional Council.

Monitoring results are reported in relation to the Waikato Regional Plan using the Ministry for the Environment air quality indicator reporting framework outlined in the table below. This framework is used to report on air quality across a range of contaminants relative to their respective guidelines.

Table 1: Ministry for the Environment categories for air quality

 *The 'excellent' category should not be applied to PM₁₀ because the level of detection of most monitoring methods is not accurate enough.

Table 2: 2012 one-hour sulphur dioxide levels at Hamilton

Table 3: 2012 24-hour sulphur dioxide levels at Hamilton

National and regional ambient air quality guidelines for sulphur dioxide are:

• 350 µg/m₃ – 1 hour average.
• 120 µg/m₃ – 24 hour average.

National Environmental Standards for Air Quality for sulphur dioxide are:

• 350 µg/m₃ – 1 hour average (9 allowable exceedances per year).
• 570 µg/m₃ – 1 hour average (not to be exceeded).

Waikato Regional Council has carried out sulphur dioxide monitoring in Hamilton and Tokoroa only and has no evidence to indicate that concentrations of sulphur dioxide in other areas are likely to be of concern.

The graph and table below shows the percentage of air samples with sulphur dioxide levels in the ‘excellent’, ‘good’, ‘acceptable’, ‘alert’ and ‘action’ categories relevant to the regional and national guidelines for the year 2012 as measured at the Ohaupo Road (Blood bank) monitoring station. Tokoroa results are measured at the Billah Street reserve monitoring station 2017 to 2018. All samples (100%) were within the ‘excellent’ category. Data for the 1 hour average are presented relative to the regional and national guideline of 350 µg/m₃.

Table one: comparison of one-hour average sulphur dioxide levels measured in Hamilton (2012) and Tokoroa (2017-2018) to air quality indicator categories. 

Percentage of air samples with sulphur dioxide levels in the excellent, good, acceptable, alert, or action categories

• The data were collected in Hamilton from 1 March 2012 to 31 August 2012 and averaged 1 hourly.
• The data were collected in Tokoroa from 1 December 2017 to 31 May 2018 and averaged 1 hourly.
• Find out more about air quality around the Waikato region.