The thesis investigates the inorganic aerosol concentrations and wood smoke tracer potassium and levoglucosan concentrations in Birmingham, UK. Also a multi-wavelength aethalometer was utilized as a carbonaceous aerosol detector to directly measure the local wood smoke PM mass and traffic PM mass. To achieve this, daily PM2.5 inorganic ions sodium, ammonium, potassium, magnesium, calcium, chloride, nitrate, sulphate, and organic compound levoglucosan were measured over a period of more than one and half years at four sampling locations. There were: (1) Elms road, University of Birmingham; (2) North Kilworth Mill Observatory Site; (3) Churchill Pumping Station Site; and (4) Budbrooke, Warwick Sampling Site. Correlation analysis, regression analysis, and seasonal variation were examined for those inorganic and organic elements and compounds. The results were used to provide comprehensive spatial and temporal distributions, intra-site and inter-site comparison differentiations. Wood smoke potassium and levoglucosan were used as wood smoke tracer to determine the local resident wood smoke PM mass concentrations in this thesis. Budbrooke, Warwick Sampling Site for example, a mean value of 62ng m-3 wood smoke potassium was measured at winter periods but the mean value of only 17ng m-3 was measured during summer periods. This significant difference demonstrated a frequent wood smoke activity in this area during winter periods. Also a multi-wavelength aethalometer was used as wood smoke mass detector to measure the local resident wood smoke PM mass and local traffic PM mass concentrations. These three methods have their unique processes of acquiring the wood smoke mass concentrations, thus the results from these method have considerable variations. Therefore these three methods have inter-compared with each other to achieve better wood smoke concentrations results in order to obtain the best method of measuring local wood smoke mass.

The gas-phase reactions of ozone with alkenes can be significant sources of free radicals (OH, HO2 and RO2) in the Earth’s atmosphere. While there are a number of quantitative indirect OH and HO2 yield measurements from ozonolysis in the literature, obtained, for example, through the use of radical tracer / scavenger species, few direct observations have been reported. This thesis presents the first direct measurements of OH and HO2 by Laser Induced Fluorescence for a homologous series of alkenes. The radical and stable products from ethene, propene, 1-butene, 2 methylpropene, cis-2-butene, trans-2-butene and 2,3-dimethyl-2-butene ozonolysis have been observed. The experiments were carried out in the EUPHORE atmospheric simulation chamber, utilising various instrumentation including Fourier Transform Infrared Spectroscopy and Peroxy Radical Chemical Amplification. The alkene-ozone reaction systems were investigated with and without an OH radical scavenger and as a function of humidity. The results were interpreted through detailed chemical chamber box modelling, incorporating the Master Chemical Mechanism degradation scheme for each specific alkene, supplemented with a more explicit representation of the alkene-ozone reaction mechanism. The observed yields are interpreted in terms of branching ratios for each channel within the postulated alkene ozonolysis mechanism, and their implications for atmospheric radical production were considered.

Phytoextraction in the UAE desert soil (sandy, calcareous, less than 0.5% humus, and pH 7.9) has been studied. Twelve suspected polluted sites were investigated for contamination with eight heavy metals and sixteen local plants from the UAE desert were evaluated for their ability to accumulate heavy metals. The soil of Ajman industrial zone demonstrated high amounts of total chromium (1800 mg/kg) and of hexavalent chromium (97 mg/kg) which is a significant environmental threat. Portulaca oleracea (Purslane) has been shown to be the best candidate for Cr(VI) accumulation. Total chromium concentration exceeded 4600 mg/kg in roots and 1400 mg/kg in stems confirming the role of P. oleracea as a Cr(VI) accumulator. More than 95% of the accumulated Cr(VI) was reduced to the less toxic Cr(III) within the plant. The uptake of Cr(VI) by this plant has been investigated. The uptake of Cr(VI) increased as its concentration in soil increased between 50 and 400 mg/kg. The highest Cr(VI) uptake was observed at the high pH and low organic matter content of soil confirming the phytoextraction efficiency of P. oleracea in soils found in the UAE. The uptake of Cr(VI) increased in the presence of sulfate anion (suggesting that chromate uses the same carriers of sulfate in root cells) while nitrate and phosphate retarded the uptake. Potassium and ammonium ions, but not sodium ions, enhanced the uptake of Cr(VI) confirming the effect of accompanying cations. EDTA enhanced the translocation factor of chromium from roots to shoots in plants irrigated with either Cr(III) or Cr(VI). HPLC-MS analysis showed that ascorbic acid is the main antioxidant that reduced Cr(VI) to Cr(III) which is then mostly translocated to shoots after chelation with organic acids such as oxalate since glutathione and phytochelatins were not observed at significant levels in the tissues of plants exposed to Cr(VI).

Over the past decade, the occurrence and removal of emerging contaminants in the environment has received much attention. Both natural and synthetic progestogens, which are hormones, and also benzotriazoles are two examples of such emerging contaminants. Sewage treatment works are recognised as one of the main routes of these compounds to the environment. Low concentrations (nanograms per litre) of biologically active chemicals may exhibit an impact on aquatic organisms and human health. This study was undertaken to determine the occurrence and removal of these two classes of chemicals at sewage treatment works, along with an evaluation of the performance of advanced treatment and also to investigate their fate in the aquatic environment. Therefore, field-based sampling campaigns were undertaken at a sewage treatment works, rivers and potable water to achieve these aims. Solid phase extraction and LC/MS/MS were used in order to analyse the samples from these different locations, along with catchment modelling and assessment of how the use of benzotriazoles may contribute to their presence in the environment. The results have demonstrated that progestogens and benzotriazoles are in the sewage system; the natural hormone (progesterone) was the most predominant compound entering the sewage treatment work (46.9 ng/l) among the progestogens while concentrations of the benzotriazoles were two orders of magnitude higher than the progestogens. The conventional sewage treatment works were, to some extent, able to remove these compounds from wastewaters. However, this may not be adequate to afford protection to the environment. The investigation of advanced treatments, ozone, granular activated carbon and chlorine dioxide, indicated no further significant removal of progestogens, probably as a result of concentrations being close to method detection limits. However, there were indications that benzotriazoles were removed. A degradation study demonstrated that the natural hormone (progesterone) was degraded rapidly while benzotriazoles were not degraded. Catchment modelling indicated that high (up to 2,000 ng/l) concentrations of benzotriazoles would be present in surface waters used for potable supply, and consequently benzotriazoles were found in the tap water with mean concentrations of 30.9 ng/l (benzotriazole) and 15.1 ng/l for tolyltriazole. It is therefore apparent that although conventional treatment may be seen as effective, achieving over 90% removal, this may not be good enough. However, before investing in tertiary treatment, a number of factors, such as the effectiveness at different sites, the presence of degradation products and costs, both financial and in relation to energy use, need to be considered.

CH3Br and CH3Cl (methyl halides) are the most abundant natural vectors of bromine and chlorine into the stratosphere and play an important role in stratospheric ozone destruction. The current knowledge of their respective natural sources is incomplete leading to large uncertainties in their global budgets. Beside the issue of quantification, characterisation of possible sources is needed to assist modelling of future environmental change impacts on these sources and hence the stratosphere. This study describes measurements conducted at two temperate salt marsh and three temperate forest sites in Scotland, and one tropical rainforest site in Malaysian Borneo to quantify and characterise natural methyl halide producing processes in these respective ecosystems. Measurements were conducted with static enclosure techniques, and methyl halide fluxes were calculated from the concentration difference between blank/background and afterenclosure samples. Methyl halide concentrations were determined via oxygen-doped GCECD with a custom-built pre-concentration unit. External factors such as photosyntheticallyactive radiation (PAR), total solar radiation, air temperature, soil temperature, internal chamber temperature and soil moisture were recorded in parallel to the enclosures to determine possible dependencies. Salt marsh studies were carried out at Heckie’s Hole in East Lothian, and Hollands Farmin East Dumfriesshire for 2 years. The study subjects were salt marsh plants that were enclosed during daylight hours in transparent enclosures for 10min each at 2–4 week intervals throughout the year. Parallel to this monitoring programme, systematic manipulation experiments and diurnal studies were carried out to learn more about the possible influence of potential drivers such as sunlight and temperature. Mean annual net fluxes ( standard deviation (sd)) were 300 44 ngm-2 h-1 for CH3Br and 660 270 ngm-2 h-1 for CH3Cl, with fluxes of both gases following a diurnal as well as an annual cycle, being lowest during winter nights and highest during summer days. A possible link between variations of daytime fluxes over the course of a year and changes in temperature was found. CH3Cl and CH3Br fluxes were positively correlated to each other and average fluxes of CH3Cl were linked to dry mass of certain species such as Puccinellia maritima, Aster tripolium, Juncus gerardi and Plantago maritima as found at the different measurement locations. No link between methyl halide fluxes and total halogen content or halogen concentration of the enclosed vegetation was found. Work in temperate forests was carried out for over one year at Fir Links, a mixed beech/ sycamore forest in East Lothian, and on one occasion each in Griffin Forest, a sitka spruce plantation in Perthshire, and finally the Hermitage of Braid, a mixed woodland park in Edinburgh. The study subject was leaf and needle litter which was enclosed in opaque 12 L containers for 10min–24h. During enclosure, internal chamber temperature was recorded, and leaf/needle litter water content was determined after enclosure. Combined average CH3Br and CH3Cl fluxes from temperate forest litter were 4.3 10-3 ngg-1 h-1 and 0.91 ngg-1 h-1, respectively. Average fluxes measured from leaf and needle litter were comparable in magnitude and CH3Br and CH3Cl were positively correlated. However no correlation of methyl halide fluxes to either temperature or litter water content was observed. Work at Danum Valley inMalaysian Borneo focused on flux measurements from both trees and leaf litter in a tropical dipterocarp forest. Fluxes from tropical trees were measured with transparent branch chambers at 20min enclosure times whilst methyl halide fluxes from leaf litter were measured with opaque 12 L containers at 24h enclosure times. Mean CH3Br and CH3Cl fluxes from branch enclosures were 0.53 ngg-1 h-1 and 27 ngg-1 h-1, respectively, and CH3Br and CH3Cl fluxes from tropical leaf litter were 1.4 10-3 ngg-1 h-1 and 2.3 ngg-1 h-1 respectively. Again fluxes of CH3Br and CH3Cl were positively correlated but no direct environmental driver for flux variations was found. The magnitude of methyl halide fluxes was species specific with individuals of the genus Shorea generally producing large amounts of methyl halide. Tropical rainforests were confirmed to be potentially the largest single natural source of CH3Cl. Global estimates were derived from extrapolating measured fluxes from the respective global land cover areas. These estimates suggest that the ecosystems examined in this study could account for over 1/3 of global CH3Cl production and up to 13%of global CH3Br production in nature. The ratio of CH3Br to CH3Cl emissions for these ecosystems is likely to be dependent on the abundance of bromine in the plant material with higher bromine content boosting CH3Br production and suppressing CH3Cl production. For this reason salt marshes are only a very minor source of CH3Cl.

Peatlands cover approximately 2-3% of the world’s land area yet represent approximately a third of the worlds estimated total soil carbon pool. They therefore play an important role in regulating global atmospheric CO2 and CH4 concentrations, and even minor changes in their ability to store carbon could potentially have significant effects on global climate change. Much previous research has focussed primarily on land-atmosphere fluxes. Where aquatic fluxes have been considered, they are often in isolation from the rest of the catchment and usually focus on downstream losses, ignoring evasion (degassing) from the water surface. However, as peatland streams have been repeatedly shown to be highly supersaturated in both CO2 and CH4 with respect to the atmosphere, they potentially represent an important pathway for catchment GHG losses. This study aimed to a) create a complete GHG and carbon budget for Auchencorth Moss catchment, Scotland, linking both terrestrial and aquatic fluxes, and b) understand what controls and drives individual fluxes within this budget. This understanding was further developed by a short study of C exchange at the peat-aquatic interface at Mer Bleue peatland, Canada. Significant variability in soil-atmosphere fluxes of both CH4 and N2O emissions was evident at Auchencorth Moss; coefficients of variation across 21 field chambers were 300% and 410% for CH4 and N2O, respectively. Both in situ chamber measurements and a separate mesocosm study illustrated the importance of vegetation in controlling CH4 emissions. In contrast to many previous studies, CH4 emissions were lower and uptake greater where aerenchymous vegetation was present. Water table depth was also an important driver of variability in CH4 emissions, although the effect was only evident during either periods of extreme drawdown or when the water table was consistently near or above the peat surface. Significant pulses in both CH4 and N2O emissions were observed in response to fluctuations in water table depth. Despite the variability in CH4 and N2O emissions and the uncertainty in up-scaled estimates, their contribution to the total GHG and carbon budgets was minor. Concentrations of dissolved CO2 in peatland drainage waters ranged from a mean of 2.88 ± 0.09 mg C L-1 in the Black Burn, Scotland, to a mean of 7.64 ± 0.80 mg C L-1 in water draining Mer Bleue, Canada. Using non-dispersive infra-red (NDIR) CO2 sensors with a 10-minute measurement frequency, significant temporal variability was observed in aquatic CO2 concentrations at the 2 contrasting field sites. However, the drivers of this variability differed significantly. At Mer Bleue, Canada, biological activity in the water column led to clear diurnal cycles, whereas in the Black Burn draining Auchencorth Moss, dilution due to discharge was the primary driver. The NDIR sensor data also showed differences in soil-stream connectivity both between the sites (connectivity was weak at Mer Bleue) and across the range of conditions measured at Auchencorth Moss i.e. connectivity increased during periods of stormflow. Compiling the results from both the terrestrial and aquatic systems at Auchencorth Moss indicated that the catchment was functioning as a net sink for GHGs (382 kg CO2-eq ha-1 yr-1) and a net source of carbon (143 kg C ha-1 yr-1). The greatest flux of GHGs was via net ecosystem exchange (NEE). Terrestrial emissions of CH4 and N2O combined returned only ~5% of CO2-equivalents captured by NEE to the atmosphere, whereas evasion of CO2, CH4 and N2O from the stream surface returned ~40%. The budgets clearly show the importance of aquatic fluxes at Auchencorth Moss and highlight the potential for significant error in source/sink strength calculations if they are omitted. Furthermore, the process based understanding of soil-stream connectivity suggests the aquatic flux pathway may play an increasingly important role in the source-sink function of peatlands under future management and climate change scenarios.

Rises in anthropogenic CO2 emissions are now widely acknowledged to be responsible for changes in the global climate, with potentially disastrous consequences if these rises continue unchecked. Although knowledge of ecosystem responses to climate change has improved, there are still large underlying uncertainties regarding their response to warming. Of all the ecosystems with the potential to mitigate rises in CO2, forests are arguably the most important because of their huge land area and store of carbon. A large proportion of the carbon stored in forests is found in the soil, and it is the response of this soil carbon to temperature that is the main determinant of a forest’s ability to act as a carbon sink, or indeed source. Understanding the response of soil carbon flux to temperature, as well as the contribution of soil carbon flux to the carbon balance of forests as a whole is crucial in helping to improve modelling approaches. In this thesis I first examined the temperature response of old and new soil organic carbon from a Sitka spruce plantation under controlled laboratory conditions. Both the old and new soil organic carbon showed similar temperature sensitivities after prolonged incubation at 20 °C, thus implying a similar response to increasing temperatures. Using a variety of different methods (root intensity, meshing and stable isotope analysis) I then studied the responses under field conditions. These methods showed that autotrophic respiration was responsible for up to 50 % of total soil respiration, and was more sensitive to temperature than heterotrophic respiration. Finally, I compared the contributions and determinants (particularly temperature and moisture) of soil respiration fluxes to ecosystem fluxes at a temperate (Sitka spruce) and Mediterranean (Maritime pine) forest. Temperature was found to be the dominant driver of soil respiration fluxes at the temperature forest, whilst soil respiration was limited by moisture at the Mediterranean forest. Statistically significant relationships between net ecosystem productivity and soil respiration (and the stable isotope signature of soil respiration) were found at both forests, indicating a close coupling between above-ground processes and soil respiration.

Carbon monoxide (CO) is present in the troposphere as a product of fossil fuel combustion, biomass burning and the oxidation of volatile hydrocarbons. It is the principal sink of the hydroxyl radical (OH), thereby affecting the concentrations of greenhouse gases such as CH4 and O3. Consequently, CO has an atmospheric lifetime of 1-3 months, making it a good tracer for studying the long range transport of pollution. Satellite observations present a valuable tool to investigate tropospheric CO. The Atmospheric InfraRed Sounder (AIRS), onboard the Aqua satellite, is sensitive to tropospheric CO in ~50 of its 2378 channels. This sensitivity to CO, combined with the daily global coverage provided by AIRS, makes AIRS a potentially useful instrument for observing CO sources and transport. An optimal estimation retrieval scheme has been developed for AIRS, to provide CO profiles from near-surface altitudes to 150 hPa. Through a validation study, using CO profiles from in-situ aircraft measurements, this retrieval scheme has been shown to provide CO observations with strong correlations to in situ measurements. Compared to the operational AIRS v4 CO product this retrieval scheme is shown to provide total column CO retrievals with a reduced bias relative to the in situ measurements (~ -10% to ~ -1%). In addition, the optimal estimation retrieval is shown to provide improved estimation and characterization of the retrieval errors. Further validation work has been carried out through comparison with the established CO observations from the MOPITT instrument, onboard the Terra satellite. Good agreement (correlation coefficient > 0.9, and bias < 1.0 ppbv) between the instruments is observed in the mid-troposphere. At this level, the optimal estimation scheme is shown to remove a positive bias of ~10 ppbv, relative to MOPITT, that is present in the AIRS v4 CO product. The AIRS instrument is also shown to be less sensitive to CO in the lower troposphere than MOPITT. AIRS is also demonstrated to provide fewer pieces of independent information about the vertical structure of CO at tropical latitudes, where higher thermal contrast increases the sensitivity of MOPITT. Through time series analysis, the capability of AIRS to detect seasonal trends in CO is demonstrated. The potential of AIRS to be used to track, both horizontal and vertical, CO transport is explored. AIRS is shown to be capable of tracking horizontal transport, and to have potential to track vertical transport when combined with another satellite sensor.

This thesis details the ACTIVE campaign in the tropics of northern Australia during 2005-2006 (based in Darwin). The focus of the campaign was to find the influence of tropical convection on the aerosol and chemical content of the Tropical Tropopause Layer [TTL] and the cirrus cloud cover in the area, which is important for the global energy budget. This study details the background climatology of the Darwin region with statistical categorisation of the trace gases and particles. The TTL had regions of extremely high aerosol number concentration, much higher than that of the PBL. The 10 to 1000 nm particle concentrations were as high as 25,000 cm-3 and 100 to 1000 nm were as high as 1000 cm-3. High aerosol concentrations were usually found in cloud-free conditions; cloudy regions were typically low in aerosol number. Wind data and trajectories (BADC) were used to find the origin of the high particle concentrations. Aerosols were found to be nucleating in outflow regions of convective anvils. SO2 oxidation to H2SO4 is a widely accepted mechanism for nucleation. A binary mechanism (H2O-H2SO4), with SO2 as the precursor, was found to be inadequate in explaining the nucleation and growth rates -- tested using an aerosol sectional model. However, it was found, via back trajectory analysis, that the climatology of Darwin was influenced by local and long-range sources, including advection from Indonesia and the Tropical Warm Pool. These distant sources could have introduced condensable matter, with aerosol precursor properties (certain organic compounds). The aerosol model found a condensable precursor concentration of at least 300 pptv was necessary to replicate the observations.

L’azote (N) est un élément indispensable pour les végétaux mais reste limitant dans la majorité des écosystèmes forestiers. La source principale de N pour les arbres provient de la décomposition des litières. Afin d’étudier le devenir du N des litières dans l’écosystème forestier, une expérience de marquage d’une cohorte de litière enrichie en azote 15 (15N) a été mise en place dans dix hêtraies européennes. Sur le moyen terme (une décennie), les profils 15N dans le sol montrent une faible incorporation du marqueur en profondeur (>10cm). Dans les feuilles, la dynamique d’incorporation du 15N par l’arbre témoigne de la mise à disposition du N des litières puis de sa stabilisation dans les agrégats du sol. L’utilisation du N dérivé des litières par l’arbre dépend des besoins en N des arbres mais aussi du type d’humus. Les arbres sous moder sont capable d’utiliser le N dérivé des litières directement depuis l’horizon organique. Environ 25 % des besoins totaux en N de l’arbre sont couverts par la réallocation du N, et 75 % sont issus du prélèvement du N dans le sol. / Nitrogen ( N) is an essential element for plants but is limited in most forest ecosystems. The main source of N for trees comes from the decomposition of litter. The fate of litter N on the long term (ten years) in beech forest was followed using one cohort of litter enriched in nitrogen-15 (15N) in ten sites in Europe. 15N in the soil profile showed a low incorporation of litter-derived N deeper than 10 cm. Leaf 15N dynamics illustrate the litter N availability and then its stabilization in the soil aggregates.The use of litter derived N in the tree depends on the needs of N by trees but also on the type of humus. At moder humus sites, trees are able to mine the litter-derived N directly from the organic horizon. Approximately 25 % of the total N requirement of the trees are covered by the N reallocation, and 75 % comes from soil N uptake.