The work in this thesis describes measurements of peroxy radicals from a ground-based platform using a PERCA (Peroxy Radical Chemical amplifier) at two field campaigns, TORCH I and II (Tropospheric Organic Chemistry Experiment). TORCH I took place during July and August of 2003 in Writtle, Essex, 25 miles northeast of London. TORCH II took place one year later in April and May at the Weybourne Atmospheric Observatory, 120 miles northeast of London. Originally conceived to compare relatively fresh air masses from London with more processed air masses some distance from London, the two TORCH campaigns rarely experienced wind coming from the London direction. During TORCH I record temperatures hit much of the UK and Europe with ozone mixing ratios exceeding 150 ppbv at the measurement site and peroxy radicals having average midday mixing ratios during the heatwave over three times non-heatwave averages. The relationship between the high ozone and peroxy radical mixing ratios is explored. A comparison of measured, modelled and PSS (Photostationary state) peroxy radicals for the TORCH I campaign is presented. Although during TORCH II the desired air masses from London did not come and there was no such heatwave as in TORCH I, the measurement site did experience air masses with a variety of histories. A particular event from the TORCH II field campaign involved high concentrations of propene (3 orders of magnitude higher than the previous or subsequent hourly measurements) at 20:00 hours and concomitant five-fold increase in peroxy radical mixing ratio. Radical production is attributed to ozone-alkene reactions and although the importance of such reactions for radical production is well-known, the case study presented represents a clear example occurring in the planetary boundary layer. In order to enhance the capabilities of the PERCA instrument a further inlet was added to it with a view to the seperate measurement of HO2 from SRiO2 (the sum of organic peroxy radicals). A calibration source for generating HO2 radicals was built and tested. Laboratory tests showed that the system could measure either the sum of peroxy radicals or organic peroxy radicals only but results from deployment at TORCH I proved inconclusive.

This thesis investigates measurements of peroxy radicals using PERCA, photolysis frequencies of ozone (jO1D) and NO2 (jNO2 ) using filter radiometers (FR’s) and processes controlling atmospheric chemistry within the West African Monsoon (WAM). The chain length (CL) of the University of Leicester (UoL) ground and aircraft PERCA inlets are shown to decay exponentially with relative humidity, and a humidity interference is observed with the luminol chemiluminescence NO2 detection technique. The altitude dependence of the CL is derived using a chain chemistry model. The aircraft PERCA NO2 sensitivity is derived by calculating the background NO2 concentration from reaction of ambient ozone with reagent NO. Calibration of the UoL aircraft FR’s is described; temperature, solar zenith angle and ozone column bias in the jO1D measurement is estimated. A method is proposed for cross-calibration of FR’s spectral response using spectrally resolved measurements of actinic flux. An estimate for upwelling jO1D is assessed where the instrument failed during fieldwork. Atmospheric composition is dominated by surface emissions and transport within theWAM. A nocturnal flow transports reactive VOC’s and oxidation products north, anthropogenics from coastal cities and biogenics from forested regions. Significant night-time concentrations of RO2, HO2, and potentially OH are observed. The most photochemically active air masses observed are biomass burning (BB) plumes of Central African origin. Variations in radical composition, inferred from VOC reactivity to OH, follow the trends of the University of Leeds DSMACC box model. The ozone balance is NOx limited within air masses where biogenic soil NOx emissions are suggested. PERCA and FR measurements are assessed through comparison to model results. Daytime PERCA measurements compare well with DSMACC RO2 with differences explained through measurement bias – ambient aircraft measurements appear responsive to RO2 only, with no humidity dependence and complete HO2 loss. Median noontime concentrations of RO2 of 35 pptV are observed.

This thesis explores the atmospheric chemistry of peroxy radicals (HO2 + SigmaiRiO 2) via a series of new measurements. Peroxy radical measurement techniques are discussed, and the University of Leicester PERCA instrument is described in detail. Three field campaigns are described.;Peroxy radical concentrations during ITOP displayed an increase with altitude that is likely to have been impacted by the effects of long-range transport. Enhanced peroxy radical concentrations were observed within air-masses traversing the Atlantic indicating significant photochemical activity during transport. Net ozone production at clear sky limit is in general negative, and the summer mid-Atlantic troposphere is at limit net ozone destructive. There is evidence of positive ozone production within air masses undergoing long-range transport. Ozone production was NOx limited throughout the airmasses measured during ITOP.;Two contrasting periods of meteorology were encountered at Jungfraujoch -- days with and without heavy snowfall. Peroxy radicals were significantly suppressed during 'snowy' days, with neither increased NO x nor reduced j(O1D) accounting for the difference. To reconcile the difference a pseudo first order loss rate of kex = 0.0063 s-1 is required. Ozone production rates show that overall the Jungfraujoch was net neutral to marginally ozone destructive. Overall ozone production through the campaign was peroxy radical limited. The ozone compensation point for 'snow free' days was 28 pptv.;The formation of secondary organic aerosol was studied at a simulation chamber. High NOx, O3 and peroxy radical concentrations caused problems with peroxy radical measurements, but modelling studies showed that measurements under atmospheric conditions are only negligibly affected. Further experiments at low concentrations of NOx, O3 and peroxy radicals and constant HONO concentration showed peroxy radicals within the chamber began to build up prior to aerosol nucleation, indicating the potential role of organic hydroperoxides in the formation of secondary organic aerosol. Preliminary model results are also discussed.

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Road deposited sediments (RDS) are a unique aspect of the urban environment, a complex dynamic and mobile system that acts as both sink and source for a variety of potentially toxic inorganic metals, organics and nutrients. Instrumental to the understanding of the nature of RDS and how they cycle in and interact with the urban environments, is the oxidation state, binding form and binding partners of the associated metal contaminants. The aims of the research programme are (i) to provide a comprehensive geochemical and mineralogical analysis of RDS in the urban environment of Oxford Road. Manchester, UK; (ii) to define the physicochemical form and determine, for the metal contaminants Cu, Pb and Zn within the RDS matrix, their true chemical speciation in the solid state, and in so doing improve the understanding of how these contaminant metals cycle within the urban environment thus providing baseline information for determining their effects on human health. Physical and geochemical characterization using grain-fractionation techniques and conventional chemical methodologies show that the grain-size fractions of less than 63 11m account for the smallest percentage mass of the sediment but have the highest concentration of metal contaminants. In contrast, consideration of grain-size mass loading showed that the majority of the contaminant load was carried by grain-size fractions greater than 63 11m. Hazard assessment of the total metal concentrations using (i) adjusted Dutch Intervention and Target Values for RDS. reveal Cu, Pb and Zn to be above their target concentrations. Copper is of particular concern. with concentrations consistently above intervention values and in need of remediation; and (ii) enrichment factors, show that Pb is the most enriched in the Manchester RDS, suggesting that sources of Pb include historic deposits and achieving sustained remediation will require a long time. Scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS), show that quartz grains are the most numerous in the Oxford Road sediments. Iron oxide grains are observed in all grain fractions. The presence of Cu-, Pb- and Zn-bearing grains is also noted in a number of grain-size fractions. Grains of Cu and Pb in association with Cl were detected in the 250-125 11m and 1000-500 11m, respectively. whilst Pb- and Cr-bearing grains were noted in the <38 11m fraction. In addition, intermetallic compounds (e.g. Cu-Sn; Cu- Zn; Pb-Cu and Zn-Sn) were discerned in a number of grain-size samples. X-ray powder diffraction (XRD) traces show that quartz is the dominant crystalline phase all in grain-size fractions. Iron oxide (hematite or magnetite), calcite and felspathic minerals (albite and microcline) are a minor component in all size fractions, and the phyllosilicates kaolinite and chlorite are also minor phases in the 63-38 11m and <38 11m fractions. Trace amounts of Cu metal and Cu chromite are suggested by the XRD data for the heavy mineral separate for the coarsest fraction, whilst the presence of cometite (CuP04) is intimated in the analysis of the 125-63 11m sample. The occurrence of trace quantities of anglesite (PbS04), Pb-apatite, Pb basic carbonate and Pb oxide chloride are indicated also by the XRD data for the heavy mineral separate fractions from all grain fractions (with the exception of the <38 11m fraction). Analysis of XRD diffractograms for the 2000-1000 11m and 125- 63 11mfractions (heavy mineral separate) also suggest that low levels Zn metal and the silicate phase hodgkinsonite (Zn2Mn[Si04](OH)2), respectively. may be also present. XANES analysis and linear combination modelling indicate that 2CUO.Cr203 and Cu-sorbed goethite occur in 1000-500 11m, 250-125 11m, 63-38 11m, and <38 11m size fractions, collectively representing between 34-70% of the contributing Cu-phases, XANES analysis suggests that CuO, CU20, and Cu phosphates are also present. EXAFS modeling for the four grain-size fractions gives best fit models with a first shell of three oxygen atoms at 1.93-1.95 A, which substantiate the possible presence of Cu-sorbed goethite, and also suggest the presence of CuO, CU2(P04)(OH), Cu(C2H302)2.H20 and CuS04·5H20. Second shell Cu-Sn and second and third shell Cu-Cu and Cu- Pb suggests a clear association between and metalliferous phases in the Manchester RDS. Linear combination modelling of the XANES data for Pb phases suggest that PbCr04 and Pbsorbed goethite occur in 1000-500 urn, 250-125 11m, 63-38 11m, and <38 11m size fractions, collectively representing between 51-67% of the contributing Pb-phases, XANES analysis suggests that PbO, PbCl2, and Pb carbonates are also present. EXAFS modeling for all grain-size fractions gives best fit models with a first shell of two oxygen atoms at 2.29-2.32 A, which corroborate the possible occurrence of Pb-sorbed goethite, and also suggest the presence of Pb phosphates and Pb oxides. Second shell Pb-Fe and second and third shell Pb-Pb scattering distances confirm Pb-sorbed to Fe oxide, and PbCl2 and PbCr04, respectively. XANES analysis and linear combination modeling of Zn phases indicate that Zn(N03)2·6H20 is the dominant species all four grain-size fractions, representing between 42-48% of the contributing Zn-phases, XANES analysis suggests that ZnCl2 and Zn-sorbed goethite are also present. EXAFS modeling for all grain size fractions gives best fit models with a first shell of five to six oxygen atoms at 2.0 I-2.03 A. the possible presence of Zn(N03)2·6H20 and Zn-sorbed goethite is not corroborated. Second shell Zn-Fe and Zn-Al scattering distances suggest the presence of Zn-sorbed species on metal hydrous oxides and phyllosilicates, whilst second and third shell Zn-Si suggest that Zn-bearing silicates may contribute to the Zn speciation of the Oxford Road sediments. The identification of individual elemental species allows for the important discrimination of Cu, Pb and Zn phases. Epidemiological studies have shown that species such as CuO. PbCr04 and ZnCI2, identified by XAS analysis to be present in the Oxford Road sediments are of concern to human health.

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