Odour Threshold Investigation 2012 - Bay of Plenty Regional Council

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Figure 7.17 Scatterplot showing n-butanol and H 2 S relationship. . 50 Environmental Publication 2012/06–A review of odour properties of H 2 S Odour Threshold Investigation 2012
Part 8: Discussion and conclusion 8.1 Discussion The primary questions for this investigation were – (i) what was the H 2 S detection threshold for a non-laboratory type screening panel? and (ii) was there a difference in the results obtained for people living in an area with naturally high levels of H 2 S (Rotorua) and those living elsewhere? The concept of developing an odour threshold using local residents was to ensure that the scientific and planning decisions around H 2 S discharges are soundly based and directly relevant to the region. The threshold data calculations for this investigation have yielded a geometric mean concentration of 0.7 µg/m 3 when determined across the entire panel (n. = 59). The geometric means for the Rotorua and Whakatāne subgroups are 1.1 and 0.5 µg/m 3 respectively. These values are all well below the current NZAAQ guideline value of 7 µg/m 3 . The geometric means are at the lower end of international threshold data summarised in Figure 8.1 (which is a repeat of Figure 5.1 but with the current results added at the bottom). Discussion with olfactometry practitioners indicate that the results from this investigation are comparable with what they have recorded in laboratory type settings 79 . The current NZAAQ guideline value of 7 µg/m 3 which was first documented nationally nearly 20 years ago 67 and discussed even earlier in a New Zealand context in the early 1980’s 72 is still widely used as a starting point for odour assessments. For geothermal affected areas the common approach has been to use a value of 70 µg/m 3 , which was based on the historic New Zealand Health Department guideline. This value of 70 µg/m 3 meets the Good Practice Guide for Assessing Odour in New Zealand 61 recommendation whereby for low sensitivity receiving environments the ambient concentrations can be in the order of 5-10 odour units (equivalent to 5 -10 times the odour threshold). However, using the threshold determined in this investigation the acceptable low sensitivity receiving environment values would only be in the order of 3.5 to 7 µg/m 3 , which as stated above is the value for non-geothermal (i.e. high sensitivity) areas. A guideline of 3.5 to 7 µg/m 3 , is up to ten times lower than the value that is currently used for geothermal areas. However, based on community feedback and/or the lack of complaints about geothermal power plant emissions it appears these communities can tolerate 100 times the odour threshold determined in this study. This tolerance may well be due not to physiological changes in these people, but more so the acceptance of their location (which is often characterised by having a number of active geothermal surface features) and the economic and societal benefits associated with the use of the geothermal features/resource. In relation to the second question of this investigation the groups were spatially different, with one consisting of panellists from Whakatāne and Tauranga (non-geothermal areas) and one group from Rotorua, where the panellists are frequently exposed to concentrations well above the international literature odour thresholds. Other basic characteristics of the groups showed that they were generally similar in profiles when it came to the age and sex of the panellists. The residence time for the Rotorua panellists was also recorded. This was compared with threshold values for this group. The results showed no relationship with residence time and average measured threshold. 79 Pers comms with Terry Schulz during testing in Whakatāne, March 2012. Environmental Publication 2012/06–A review of odour properties of H 2 S Odour Threshold Investigation 2012 51
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A review of odour properties of H 2
Page 5:
Acknowledgements Dr Bruce Graham fo
Page 8 and 9:
In relation to the second question
Page 10 and 11:
6.5 Equipment 29 6.6 Requirements o
Page 12 and 13: Figure 7.10 Graphical summary of th
Page 14 and 15: The standardisation of DDO in Austr
Page 16 and 17: Figure 2.1 Odorant receptors and th
Page 18 and 19: Figure 2.3 Relative slope of odour
Page 21: Part 3: H 2 S health effects The pr
Page 24 and 25: such as composting can provide very
Page 26 and 27: Seigel et al 32 undertook measureme
Page 28 and 29: Rotorua District Council also under
Page 30 and 31: Kevern 56 undertook several surveys
Page 33 and 34: Part 5: H 2 S threshold information
Page 35 and 36: The American Industrial Hygiene Ass
Page 37: Earlier summaries of data in relati
Page 40 and 41: The results generated by the olfact
Page 42 and 43: At each round of the testing proces
Page 44 and 45: 6.7.2 n-Butanol vapour The standard
Page 46 and 47: 7.1.2 Ambient H 2 S levels No H 2 S
Page 48 and 49: Residence time for Rotorua panellis
Page 50 and 51: Figure 7.7 Example of incomplete ro
Page 52 and 53: A display of the “round” values
Page 54 and 55: Figure 7.11 Log 10 mean session dat
Page 56 and 57: Panellist means Figure 7.12 t-test
Page 58 and 59: The original concept behind the tes
Page 60 and 61: Figure 7.16 Frequency plots - perce
Page 64 and 65: Several types of analysis of the gr
Page 66 and 67: Figure 8.1 Updated H 2 S threshold
Page 69: Appendix 1 - Olfactometer calibrati
Page 73 and 74: Appendix 3 - Dr Ray Littler analysi
Page 75 and 76: Effect of elevated ambient H 2 S On
Page 77 and 78: Figure 4 Untransformed is non-norma
Page 79 and 80: 14 Histogram of MnH2S_Whakatāne 12
Page 81: Histogram of Mn butanol Lognormal R
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Odour Threshold Investigation 2012 - Bay of Plenty Regional Council

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