Measurements of Halogen and Peroxy Radicals by Chemical Amplification Cristian M. Mihele A thesis submitted to the Faculty of Graduate Studies in partial fulfilment of the requirements for the degree of Doctor of Philosophy Graduate Programme in Chemistry York University Toronto, Ontario February 1999 National Library Bibliothèque nationale du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. rue Wellington Ottawa ON K1A ON4 Ottawa ON KIA ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de micro fi ch el^ de reproduction sur papier ou sur fomat électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la these ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Measurements of halogen and peroxy radicals by chernical amplification Cristian M. Mihele a dissertation submitted to the Faculty of Graduate Studies of York University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY 01999 Permission has been granted to the LlBRARY OF YORK UNIVERSITY to lend or seIl copies of this dissertation, to the NATIONAL LIBRARY OF CANADA to microfilm this dissertation and to lend or seIl copies of the film, and to UNIVERSITY MICROFILMS to publish an abstract of this dissertation. The author reserves other publication rights, and neither the dissertation nor extensive extracts from it may be printed or otherwise reproduced without the author's written permission. Abstract In this work, two halogen radical detectors were developed by modiQing the chernical amplifier for ROx radical measwements (ROx =HOz+ ROz + OH + RO). The halogen radical detectors are based on converting the halogen radicals into peroxy radicals, which are then measured with the ROx radical amplifier. The CIOx radical detector (CIOx = OC10 + Cl0 + CI) does not have the sensitivity required for ambient measurernents. Furthermore, the ROx radical amplifier is sensitive to CIO, radicals. The BrOx radical detector (BrOx = Br0 + Br) is capable of measuring very low concentrations of bromine radicals. Measurements of bromine radicals, in conjunction with measurements of photolysable halogens, were made during the Polar Sunrise Experiment 1997 at Alert, Canada. These measurements were used to bring new insights about the spring Arctic ozone depletion phenornenon. The performance of the ROx radical detector was fiirther improved and the water vapour effect on this instrument was studied. Ambient water vapour was found to have a major impact on the sensitivity of the ROx radical amplifier by decreasing the chah length. Since this instrument is usually calibrated in the presence of less than 1% of the ambient water vapour concentration, this study shows that the ROx radical ambient measurements made using this analytical technique have been severely underestimated. The main cause is due to increased wdl losses for HO2 radicaIs with increasing hurnidity. One possibility to minimise the humidity effect is to heat the walls of the reactor and to reduce the residence time in the reactor. Ambient ROx radical measurements, collected dunng an oxidant study in Northern Michigan (F'ROPHET 97),were corrected to take into account the humidity effect on the chah length. A box model was developed and constrained accordhg to the arnbient measurements of CO, 03,NO, NO2, PAN and isoprene. The output of this model for ROx radicds was compared with the radical measurements. The agreement between the model and measurements suggests that our current understanding about rural tropospheric chemistry is quite advanced. 1 would like to thank the following people: Dr. D.R. Hastie for his supervision, wonderfbl advice and his ability to find the time and the patience to discuss ideas, many of them not presented in this dissertation for obvious reasons. Dr. M. Mozurkewich and Dr. L.A.Bante, members of my supervisory cornmittee, for very useful discussions during my research evaluations. Dr. M.C. Arias, my lab partner, for very productive discussions and getting me started with the chernical amplifier. Dr. G.A. Impey for his help during Our collaborative for PSE 97 and for being a good fiiend and a challenging opponent on the tennis court. Dr. S-M. Li for an advance copy of the CREAMS modelling package. Dr. KG.Anlauf for the ozone data for PSE 97. Al1 the "PROPHETers" for support during the Michigan study and for allowing me to use their data. Al1 the CAC members for helping me 'see the lights' of atmospheric chemistry, which sometimes seemed covered by thick clouds. My parents who had the courage to immigrate to Canada. My wife Andreea for her warm love, help and support. Table of contents 1 Introduction 1.1 The importance of peroxy radicals measurements 1.2 The importance of tropospheric halogen radical measurements 1.2.1 Halogen radicals in the chemistry of marine boundary layer 1.2.2Haiogen radical during Arctic ozone depletion episode 1.3 Measurement techniques for tropospheric radical measurements 1.3.1 Chernical amplifier for ROx radical measurements 1.4 Objectives of this research 2 Description of the chernical amplifier for ROx radical measurements 2.1 NO2 detector 2.2 Reagents 2.3 HOz Calibrations 2.4 Instrument operation and data acquisition 2.5 Safety considerations 3 Analytical method development 3.1 Development of the chlorine radical detector 3.1.1 The principle of the chlorine radical detector 3.1.2Modelling the chemistry of the chlorine radical detector 3.1.3 Calibration source for chlorine radical detector 3.1.3.1 OC10 Preparation 3.1.3.2 Quantification of OClO in the gas phase 3.1.4 Instrument adaptation for chlorine radical measurements 3.1.5 Experimental evaluation of the chlorine radical detector 3.1.6New advances in understanding the chemistv related to the chlorine radical detector 3.1.7 OClO as a ROx radical source 3.1.8 Conclusions for the chlorine radical detector 3.2 Development of the bromine radical detector 3.2.1 The principle of the bromine radical detector 3.2.2Bromine radical source 3.2.3 Conversion agent for BrOx to HOx transformation 3.2.4 Linearity of the bromine amplifier 3.2.5 Calibrations of the bromine radical detector 3.2.6 Conclusions for the bromine radical detector vii 4 New improvements for the ROr radical detector 57 4.1 Measurement of the amdo~~,ozratio for the radical source based on water photolysis 4.1.1 The importance of measuring G~~o~~,~~ratio 4. t .2 Theoretical aspects for a~2&~f,()2 detennination 4.1.3 Experimentai for a~z&EF,~2determination 4.1.4 Results for CTH~~CTEF,OZdetennination 4.2 The effect of arnbient water vapour on the radical amplifier 4.2.1 Methods for studying the humidity effect on the ROx radical amplifier 4.2.2 Results for the humidity effect on the chah length of the radicai amplifier 4.2.3 Measurement of the heterogeneous wall losses for peroxy radicals 4.2.3.1 Experirnental set-up for measuring the wall losses for HO2 radicals 4.2.3.2 Sources for CH302and CH3CH302radicals 4.2.3.3 Wall loss rate coefficients for HO2, CH302and CH3CH302 radicals 4.2.4 The effect of increased NO concentrations on the radical amplifier's sensitivity to relative humidity 4.2.5 Modelling of the radical amplifier sensitivity to water vapour 4.3 Optimisation for the operation of the radical amplifier 4.3.1 Enhancement of the Signal to Noise Ratio 4.3.2 Minimisation of the water vapour interference 5 Polar Sunrise Experiment 1997 5.1 Site location 5.2 Instrumentation deployed 5.3 Field operation for the brornine radical detector 5.4 Results and Discussion 5.5 Conclusions for the BrOx measurements during PSE 97 6 PROPHET 97 field campaign 6.1 Site location 6.2 Instrumentation deployed 6.3 Configuration of the radical amplifier for PROPHET 97 6.4 Data analysis for ROx radical measurements made during PROPHET 97 6.4.1 ROx radical data for PROPHET 97 6.4.2 Theoretical considerations for ROx correlation with the square root of [O3]*UVB Radiation viii 6.4.3 Interpretation of the evening radical levels 6.5 Modelling the PROPHET 97 ROx data 6.5.1 Mode1 description 6.5.2Modehg the total radical concentration 6.5.3 Modelling studies for ROx sensitivity 6.5.3.1 Modelling studies for ROxsensitivity to isoprene 6.5.3.2Modelling studies for ROxsensitivity to ozone 6.5.3.3Modehg studies for ROxsensitivity to NOx 6.5.4 Modeliing studies on quantification the secondary radical sources 6.6 Radical levels estimated using Pseudo Steady State Approximation 6.7 Local ozone production for PROPHET 97 6.8. Conclusions for PROPHET 97 7,Conclusions and Future Directions 7.1 Conclusions 7.2 Future directions 7.2.1 Further testing of the brornine radical detector 7.2.2 Further development of the chlorine radical detector for measurernents in the Arctic troposphere 7.2.3 Further deveiopments of the radical detector for HO2 and ROz measurements 7.2.4Modelling studies for PROPHET 97 7.2.5Improvement of the ROx radical detector Appendix 14 References 15 List of Tables TabIe 1.1 Measurement