Stoichiometry in the neutral iodometric procedure for ozone by gas-phase titration with nitric oxide

Hodgeson, Jimmie A.; Baumgardner, Ralph E.; Martin, Boris E.; Rehme, Kenneth A.

doi:10.1021/ac60303a026

Cited by 40 publications

(16 citation statements)

References 8 publications

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“…Boyd et al, 1970;Pitts et al, 1976), most workers have found a stoichiometry of 1.0 within experimental error (Hodgeson et al, 1971;Kopczynski and Bufalini, 1971;Dietz et al, 1973), especially when potassium bromide is added (Lanting, 1979;Bergshoeff et al, 1980), as is the case in ozonesondes, and provided that slow side reactions with the phosphate buffer are excluded (Saltzman and Gilbert, 1959;Flamm, 1977;Johnson et al, 2002). We have allowed a modest (1 %) uncertainty for the reaction stoichiometry in both types of ozonesonde.…”

Section: Uncertainty Analysismentioning

confidence: 87%

A re-evaluated Canadian ozonesonde record: measurements of the vertical distribution of ozone over Canada from 1966 to 2013

et al. 2016

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Abstract. In Canada routine ozone soundings have been carried at Resolute Bay since 1966, making this record the longest in the world. Similar measurements started in the 1970s at three other sites, and the network was expanded in stages to 10 sites by 2003. This important record for understanding long-term changes in tropospheric and stratospheric ozone has been re-evaluated as part of the SPARC/IO 3 C/IGACO-O 3 /NDACC (SI 2 N) initiative. The Brewer-Mast sonde, used in the Canadian network until 1980, is different in construction from the electrochemical concentration cell (ECC) sonde, and the ECC sonde itself has also undergone a variety of minor design changes over the period 1980-2013. Corrections have been made for the estimated effects of these changes to produce a more homogeneous data set.The effect of the corrections is generally modest. However, the overall result is entirely positive: the comparison with co-located total ozone spectrometers is improved, in terms of both bias and standard deviation, and trends in the bias have been reduced or eliminated. An uncertainty analysis (including the additional uncertainty from the corrections, where appropriate) has also been conducted, and the altitudedependent estimated uncertainty is included with each revised profile.The resulting time series show negative trends in the lower stratosphere of up to 5 % decade −1 for the period 1966-2013. Most of this decline occurred before 1997, and linear trends for the more recent period are generally not significant. The time series also show large variations from year to year. Some of these anomalies can be related to cold winters (in the Arctic stratosphere) or changes in the Brewer-Dobson circulation, which may thereby be influencing trends.In the troposphere, trends for the 48-year period are small and for the most part not significant. This suggests that ozone levels in the free troposphere over Canada have not changed significantly in nearly 50 years.

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Section: Uncertainty Analysismentioning

confidence: 87%

A re-evaluated Canadian ozonesonde record: measurements of the vertical distribution of ozone over Canada from 1966 to 2013

et al. 2016

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“…The stoichiometry of the reaction is crucial, and has been studied extensively. Many studies, however, were made at ozone concentrations much higher than those in the troposphere, because of the difficulty of working with low concentrations of ozone at the time (Saltzman and Gilbert 1959a;Boyd et al, 1970;Hodgeson et al, 1971;Kopczynski and Bufalini, 1971;Dietz et al, 1973). Byers and Saltzman (1959) found using GPT a reaction stoichiometry of 1.00 (with unquantified uncertainty) at pH 7, and that the reaction stoichiometry varied with pH, being lower by 50% at pH 14.…”

Section: Potassium Iodide Measurement Techniquesmentioning

confidence: 99%

Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties

Tarasick

Galbally

Cooper

et al. 2019

Elementa: Science of the Anthropocene

164

168

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From the earliest observations of ozone in the lower atmosphere in the 19th century, both measurement methods and the portion of the globe observed have evolved and changed. These methods have different uncertainties and biases, and the data records differ with respect to coverage (space and time), information content, and representativeness. In this study, various ozone measurement methods and ozone datasets are reviewed and selected for inclusion in the historical record of background ozone levels, based on relationship of the measurement technique to the modern UV absorption standard, absence of interfering pollutants, representativeness of the well-mixed boundary layer and expert judgement of their credibility. There are significant uncertainties with the 19th and early 20th-century measurements related to interference of other gases. Spectroscopic methods applied before 1960 have likely underestimated ozone by as much as 11% at the surface and by about 24% in the free troposphere, due to the use of differing ozone absorption coefficients.There is no unambiguous evidence in the measurement record back to 1896 that typical mid-latitude background surface ozone values were below about 20 nmol mol -1 , but there is robust evidence for increases in the temperate and polar regions of the northern hemisphere of 30-70%, with large uncertainty, between the period of historic observations, 1896-1975, and the modern period (1990-2014). Independent historical observations from balloons and aircraft indicate similar changes in the free troposphere. Changes in the southern hemisphere are much less. Regional representativeness of the available observations remains a potential source of large errors, which are difficult to quantify.The great majority of validation and intercomparison studies of free tropospheric ozone measurement methods use ECC ozonesondes as reference. Compared to UV-absorption measurements they show a modest (~1-5% ±5%) high bias in the troposphere, but no evidence of a change with time. Umkehr, lidar, and FTIR methods all show modest low biases relative to ECCs, and so, using ECC sondes as a transfer standard, all appear to agree to within one standard deviation with the modern UV-absorption standard. Other sonde types show an increase of 5-20% in sensitivity to tropospheric ozone from 1970-1995. Biases and standard deviations of satellite retrieval comparisons are often 2-3 times larger than those of other free tropospheric measurements. The lack of information on temporal changes of bias for satellite measurements of tropospheric ozone is an area of concern for long-term trend studies.

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“…The stoichiometry of Reaction R1 has been studied extensively since its discovery in the 19th century. Many early studies were made for ozone concentrations much higher than those in the stratosphere, because of the difficulty of working with low concentrations of ozone at the time (A. W. Boyd et al., 1970; Dietz et al., 1973; Hodgeson et al., 1971; Kopczynski & Bufalini, 1971). Byers and Saltzman (1959) and Saltzman and Gilbert (1959) found that the reaction stoichiometry varied with pH, being 1.00 at pH = 7, and in general much lower at higher pH values and in unbuffered solution.…”

Section: Uncertainty Budget Analysismentioning

confidence: 99%

Improving ECC Ozonesonde Data Quality: Assessment of Current Methods and Outstanding Issues

Tarasick

Smit

Thompson

et al. 2021

Earth and Space Science

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Ozonesondes are the backbone of the global ozone observing network, making relatively inexpensive, accurate measurements of ozone from the ground to 30 km, with high vertical resolution (∼100 m), for more than 50 years. Ozonesonde data are used extensively for validation of satellite ozone data products, and are also part of merged satellite data sets and climatologies that are used for trend analyses and as a priori data for satellite retrievals. The importance of electrochemical concentration cell (ECC) sondes for trend

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Stoichiometry in the neutral iodometric procedure for ozone by gas-phase titration with nitric oxide

Cited by 40 publications

References 8 publications

A re-evaluated Canadian ozonesonde record: measurements of the vertical distribution of ozone over Canada from 1966 to 2013

A re-evaluated Canadian ozonesonde record: measurements of the vertical distribution of ozone over Canada from 1966 to 2013

Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties

Improving ECC Ozonesonde Data Quality: Assessment of Current Methods and Outstanding Issues

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