Effect of pH on the stoichiometry of the iodometric determination of ozone

Dietz, R.N.; Pruzansky, Jacob J.; Smith, Jason M.

doi:10.1021/ac60324a059

Cited by 28 publications

(24 citation statements)

References 2 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: 89%

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: 89%

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 early stoichiometric work on the yield of iodine from ozone showed varying results, with much of the uncertainty arising from the variety of KI sensing solutions, pH buffers, and sensors used (Saltzman and Gilbert, 1959;Boyd et al, 1970;Dietz et al, 1973;Pitts et al, 1976;Lanting, 1979). Common to many of the references was the suggestion of a secondary reaction producing additional iodine perhaps from reactions of iodide with the phosphate buffers.…”

Section: Chemistry Of the Ecc Ozonesondementioning

confidence: 99%

Methods to homogenize electrochemical concentration cell (ECC) ozonesonde measurements across changes in sensing solution concentration or ozonesonde manufacturer

et al. 2017

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Abstract. Ozone plays a significant role in the chemical and radiative state of the atmosphere. For this reason there are many instruments used to measure ozone from the ground, from space, and from balloons. Balloon-borne electrochemical cell ozonesondes provide some of the best measurements of the ozone profile up to the mid-stratosphere, providing high vertical resolution, high precision, and a wide geographic distribution. From the mid-1990s to the late 2000s the consistency of long-term records from balloon-borne ozonesondes has been compromised by differences in manufacturers, Science Pump (SP) and ENSCI (EN), and differences in recommended sensor solution concentrations, 1.0 % potassium iodide (KI) and the one-half dilution: 0.5 %. To investigate these differences, a number of organizations have independently undertaken comparisons of the various ozonesonde types and solution concentrations, resulting in 197 ozonesonde comparison profiles. The goal of this study is to derive transfer functions to allow measurements outside of standard recommendations, for sensor composition and ozonesonde type, to be converted to a standard measurement and thus homogenize the data to the expected accuracy of 5 % (10 %) in the stratosphere (troposphere). Subsets of these data have been analyzed previously and intermediate transfer functions derived. Here all the comparison data are analyzed to compare (1) differences in sensor solution composition for a single ozonesonde type, (2) differences in ozonesonde type for a single sensor solution composition, and (3) the World Meteorological Organization's (WMO) and manufacturers' recommendations of 1.0 % KI solution for Science Pump and 0.5 % KI for ENSCI. From the recommendations it is clear that ENSCI ozonesondes and 1.0 % KI solution result in higher amounts of ozone sensed. The results indicate that differences in solution composition and in ozonesonde type display little pressure dependence at pressures ≥ 30 hPa, and thus the transfer function can be characterized as a simple ratio of the less sensitive to the more sensitive method. This ratio is 0.96 for both solution concentration and ozonesonde type. The ratios differ at pressures < 30 hPa such that OZ 0.5% /OZ 1.0 % = 0.90 + 0.041 · log 10 (p) and OZ SciencePump /OZ ENSCI = 0.764 + 0.133 · log 10 (p) for p in units of hPa. For the manufacturer-recommended solution concentrations the dispersion of the ratio (SP-1.0 / EN-0.5 %), while significant, is generally within 3 % and centered near 1.0, such that no changes are recommended. For stations which have used multiple ozonesonde types with solution concentrations different from the WMO's and manufacturer's recommendations, this work suggests that a reasonably homogeneous data set can be created if the quantiPublished by Copernicus Publications on behalf of the European Geosciences Union. 2022T. Deshler et al.: Methods to homogenize ECC ozonesonde measurements tative relationships specified above are applied to the nonstandard measurements. This result is illustrated here ...

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“…(Davies et al, 2003) The conversion efficiency is assumed to be 1 after the ozone sensor efficiency has been applied. It was assumed that the conversion efficiency was dominated by the stoichiometry; the stoichiometry of the reaction is estimated to have an uncertainty of ±3% (Dietz et al, 1973). The estimate for the stoichiometry by Dietz et al (1973) was for a buffered potassium iodide solution.…”

Section: Uncertainty Of Ozone Sensor Efficiencymentioning

confidence: 99%

“…It was assumed that the conversion efficiency was dominated by the stoichiometry; the stoichiometry of the reaction is estimated to have an uncertainty of ±3% (Dietz et al, 1973). The estimate for the stoichiometry by Dietz et al (1973) was for a buffered potassium iodide solution. Due to the 2% 5 KI, No Buffer Solution not being buffered, the conversion efficiency uncertainty was increased to ±4.5%.…”

Section: Uncertainty Of Ozone Sensor Efficiencymentioning

confidence: 99%

Homogenizing and Estimating the Uncertainty in NOAA’s Long Term Vertical Ozone Profile Records Measured with the Electrochemical Concentration Cell Ozonesonde

Sterling¹,

Johnson²,

Oltmans³

et al. 2017

Preprint

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Abstract. NOAA's program of long term monitoring of the vertical distribution of ozone with Electrochemical ConcentrationCell (ECC) ozonesondes has undergone a number of changes over the 50 year record. In order to produce a homogenous data set, these changes must be documented and where necessary, appropriate corrections applied. This is the first comprehensive and consistent reprocessing of NOAA's ozonesonde data records that corrects for these changes using the rawest form of the 15 data (cell current and pump temperature) in native resolution as well as a point by point uncertainty calculation that is unique to each sounding. The reprocessing is carried out uniformly at all eight ozonesonde sites in NOAA's network with differences in sensing solution and ozonesonde types accounted for in the same way at all sites. The corrections used to homogenize the NOAA ozonesonde data records greatly improve the ozonesonde measurements with an average one sigma uncertainty of ±4-6% in the stratosphere and ±5-20% in the troposphere. A comparison of the integrated column ozone from the ozonesonde 20 profile with co-located Dobson spectrophotometers total column ozone measurements shows agreement within ±5% for >70% of the profiles. Very good agreement is also found in the stratosphere between ozonesonde profiles and profiles retrieved from the Solar Backscatter Ultraviolet Instruments (SBUV).

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Effect of pH on the stoichiometry of the iodometric determination of ozone

Cited by 28 publications

References 2 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

Methods to homogenize electrochemical concentration cell (ECC) ozonesonde measurements across changes in sensing solution concentration or ozonesonde manufacturer

Homogenizing and Estimating the Uncertainty in NOAA’s Long Term Vertical Ozone Profile Records Measured with the Electrochemical Concentration Cell Ozonesonde

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