Development of the NO2 sonde

Wesley Sluis Ankie Piters Marc Allaart

Requirements

• Range 1-100 ppb

• Fast (1 second)

• Lightweight (100 grams)

• Little power (1 watt)

• Cheap (disposable)

• Not dangerous to finder / environment

• Works at high altitude

Design of the instrument

Temperature dependence (1)

• The housing of the sonde is made of Polystyrene (PS), and is a good insulator.

• Typical temperature range during a balloon flight (CINDI): 20 – 40 oC.

• Temperature rising caused by Teflon air pump.

• What is the influence of the temperature on the emitted light signal?

Temperature dependence (2)

Set up:- Detector in PS box.- Constant NO2 concentrationintroduced to luminol solution.- CO2 scrubber is used to prevent acidification.-Temperature is monitored.

Result:The change in the scaling factor is within 2.0 % per degree Celsius for temperatures starting at 20 oC to 40 oC.

pH dependence

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pH

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Acidification caused by CO2:CO2 + KOH KHCO3

KHCO3 + KOH K2CO3 + H2O

It is also possible to estimate thepH as a function of time, and make a parameterization of the signal as a function of pH.This method makes it possible tocorrect the instrument’s responsefor any know initial pH.

Comparison of the NO2 sonde with an in situ monitor

• Special thanks to Lou Gast, RIVM

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Time (s)

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Conclusions

• Temperature is characterized, The change in the scaling factor is within 2.0 % per degree Celsius for temperatures starting at 20 oC to 40 oC.

• Good comparison with the photolytic analyzer. Measured the same dynamical range of changing NO2 concentrations.

• Small variations of 1ppbv NO2 are well captured by the NO2 sonde.

Outlook

• Finishing paper about “The development of the nitrogen dioxide sonde”.

• Complete the calibration of the NO2 sonde.

• Focus on launching some sondes this year.

• Promoting NO2 sonde, i.e. EGU 2010

We:•Wesley Sluis•Ankie Piters•Marc Allaart

Thanks:•Ruud Hoogeveen (SRON)•Jan Venema (RIVM)•Yipin.Zhou (EMPA)•Enno Peters (University of Bremen)•Andre van Londen•Richard Rothe•Rob Agterberg•Ed Worrell•Cor van Oort•Werkplaats

Photos:•Piet Stammes•Marc Allaart

•This project is partially financed by NIVR : Sciavisi project