The key aims of this project were: (i) investigation of atmospheric nitrogen deposition, focused on discrimination between bulk, wet and dry deposition, and between particulate matter and gas phase, (ii) accurate quantification of the contributions of dissolved organic and inorganic nitrogen to each type of deposition, and (iii) exploration of the origin and potential sources of atmospheric water soluble organic nitrogen (WSON). This project was particularly focused on the WSON fraction because, despite it being a potentially important source of bioavailable reactive nitrogen, a number of questions regarding its deposition mechanism (wet vs. dry), composition and origin (natural, anthropogenic or mixed) remain unanswered. There are two major difficulties in WSON determination: (i) the diversity of organic nitrogen compounds compared with the inorganic forms, and (ii) the lack of a direct determination method: the derivation of organic nitrogen concentrations in an aqueous sample involves the determination of the dissolved inorganic nitrogen (DIN) species concentration, comprising nitrate and ammonium, the determination of the total dissolved nitrogen (TDN) concentration, and the subtraction of the DIN concentrations from the TDN concentration. TDN determination requires a preparatory digestion step: high-temperature catalytic oxidation was the method used in this study. Ion chromatography (IC) was the method of choice for nitrate determination, whilst ammonium determination was by IC for rain samples, and by flow injection analysis for air samples collected into aqueous media. This thesis is structured in 3 main parts: the first part examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and “dry+wet” deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51′44″, W3°12′19″). Bulk deposition collectors were the standard rain gauges used in the UK national network for monitoring precipitation composition. “Dry+wet” deposition collectors were flushing rain gauges equipped with a rain detector, a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. A key objective in this part of the work was the accurate quantification of inorganic and organic water-soluble nitrogen species contribution to each type of deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, DON represented 23% of the TDN in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers. The second stage of this project was the investigation of in situ atmospheric concentrations of WSN species, both organic and inorganic. Simultaneous daily measurements of ammonium, nitrate and WSON were made between July and November 2008 at the same semi-rural site in south-east Scotland. Discrimination between material from the gas and particle phases was achieved by means of Cofer scrubbers and PTFE membrane filters, respectively. Average concentrations of NH3 (determined as NH4+), NO2/HNO3 (determined as NO3-) and WSON in the gas phase were 82 ± 54 nmol N m-3, 2.6 ± 2.5 nmol N m-3 and 18 ± 12 nmol N m-3 respectively, and in the particle phase were 20 ± 24 nmol N m-3, 10 ± 9 nmol N m-3 and 8 ± 7 nmol N m-3 respectively (± represent standard deviation across all valid daily samples, not error of triplicate samples). Except for oxidised inorganic N, average concentrations in the gas phase were larger than in the particle phase. No evidence of solely agricultural or solely combustion sources of WSON was found, as no correlation in either phase between WSON and either NH4+ or NO3- could be established. The final stage of this project was to gain a broader picture of nitrogen deposition across Europe. Rain samples were analysed for TDN and DIN from a network of 21 different sampling locations, from the south of Portugal to the north of Finland. The average DON contribution across the 21 sampling sites was ~ 19% and, according to the data gathered in this study, DON species appeared largely unrelated specifically to agricultural or to combustion nitrogen sources, although the results varied widely from site to site. Overall, this work has shown that ON and its deposition comprises a significant component of total atmospheric reactive nitrogen.

Experimental work at the 1982 Dry Deposition Intercomparison Experiment (DDIEx) involved the use of optical particle counters for covariance estimates of dry deposition velocities of accumulation mode aerosols. Meteorological and particle flux observations are presented. Deposition velocity estimates exhibit scatter about zero. A formulation of the standard error of the deposition velocity estimator is derived and examined. Using this formulation, the observed deposition velocities are shown to be marginally significant. Using a case study, the correlation coefficient is examined and presented as an important statistic to the work. Humidity effects on the measurements are briefly examined. Recommendations are made for improvements in the instrumentation. / Graduation date: 1985

Polycyclic aromatic hydrocarbons (PAHs) are one of major classes of organic pollutants. As semi-volatile organic compounds, PAHs can be transported in the atmosphere and scavenged according to various processes (dry and wet deposition). Atmospheric deposition is an important pathway for the transfer of pollutants from atmosphere to the terrestrial and water surfaces. The objective of this research is to quantify the dry and wet deposition of the atmospheric PAHs in the Kaohsiung coastal area. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also performed with diagnostic ratios to determine the potential sources of PAHs. The mean dry and wet deposition fluxes of atmospheric total suspended particles (TSP) during the study period (January-December 2010) were estimated to be 44.3 (6.60-384) and 211 (56.1-738) mg/m2d, respectively. The annual mean total PAH fluxes in dry and wet deposition were 1500 (749-3760) and 8470 (2280-46000) ng/m2d, respectively. Both concentrations and dry deposition fluxes of TSP were much higher during dust storm. During Ghost Month, however, they were comparable with other sampling events. By comparing with literatures, the total PAH concentrations of TSP were relatively low during Ghost Month, suggesting that wind direction and precipitation might be plausible. The ratio of PM2.5/PM10 had a relatively low value during dust storm, indicating that coarse particle might be predominant. In addition, during dust storm, both TSP dry deposition velocity and total PAH dry deposition velocity were higher than other sampling events. Our findings in this study showed that previous attempts in literature to estimate total PAH dry deposition fluxes by using TSP dry deposition velocity and PAH concentrations could lead to overestimate fluxes in the field. TSP dry deposition fluxes were positively correlated with atmospheric total TSP concentrations and TSP dry deposition velocity, but were correlated negatively with intensity of precipitation. In addition, TSP dry deposition velocity showed a positive correlation with TSP concentrations. Total PAH dry deposition fluxes were correlated positively with atmospheric total particulate concentrations and total PAH dry deposition velocity, but negatively with intensity of precipitation and temperature. However, TSP and total PAH fluxes in wet deposition were both correlated positively with intensity of precipitation. Diagnostic ratios showed that diesel exhaust was the main source of combustion-derived PAHs in the study. HCA and PCA analysis indicated that emissions from the ships and vehicles, and fuel used were the main sources of combustion-derived PAHs, while during special events, such as dust storm and Ghost Month, suggesting a different source of PAHs.

No description available.

Methylmercury (MeHg) is a potent vertebrate neurotoxin and a contaminant of global concern. Increased anthropogenic emissions of mercury (Hg) to the atmosphere have led to increased bioaccumulation of MeHg in top predatory organisms such as fish, the consumption of which is the main exposure pathway of this toxin to humans and other animals. Forest canopies significantly increase the deposition of Hg in general to watersheds, but sources and fates of MeHg deposition in particular remain poorly understood. In this study, wet and dry loadings of MeHg to a watershed were quantified, and the retention and (photo)reduction of MeHg on foliage were measured using unique stable isotope experiments. We found that traditional methods of quantifying net deposition underestimate incoming sources of MeHg, and that retention of MeHg on forest canopies results in delayed transport of a significant portion of newly deposited MeHg from terrestrial catchments into adjacent lakes. / Ecology

Les particules émises, dans l’atmosphère, lors de rejets chroniques ou accidentels par les installations peuvent être soumises après dispersion à des flux verticaux par temps sec : le dépôt sec et la remise en suspension. Les flux verticaux par temps sec sont caractérisés par la vitesse de transfert vertical, qui est le rapport entre le flux de particules et la concentration atmosphérique de l'aérosol au voisinage de la surface. Lorsque cette vitesse est positive, c‘est une vitesse de dépôt sec (Vd en m.s-1) et inversement, lorsqu’elle est négative, c’est une vitesse d’émission. Il est important d'étudier leur dépôt sec en milieu prairial. En effet, les produits issus de ce milieu sont une composante de la chaine alimentaire de l’homme via l’élevage. Pour les particules de moins de 1 μm, il y a un manque de données expérimentales, ce qui entraîne une incertitude sur les résultats des modèles, qui peuvent atteindre jusqu'à deux ordres de grandeur. En outre, il n'existe pas de données de mesure de la vitesse de dépôt in situ disponibles pour les particules inférieures à 10 nm. Ces particules sont issues de réaction gaz/particules (nucléation) et peuvent concerner certains radionucléides tels que l’iode (129,131I).Après leur dépôt, ces radionucléides peuvent être remis en suspension sous l’effet de la contrainte soumise par le vent sur le couvert. Un tel phénomène est soupçonné autour de la centrale nucléaire de Fukushima. Les processus de remise en suspension des aérosols, est caractérisée par la vitesse de transfert vertical (m.s-1) mais également par le coefficient de remise en suspension (Ks en m-1) qui est le rapport entre la concentration atmosphérique et la concentration surfacique de particules. Des incertitudes rémanentes de 2 à 3 ordres de grandeurs sur les coefficients de remise en suspension existent. La remise en suspension concerne l’ensemble des particules présentent sur le couvert qu’elles soient inertes ou vivantes (champignons, bactéries, levures…). Contrairement aux particules inertes, ces particules vivantes peuvent assimiler et concentrer les radionucléides. Cependant, il y a très peu de données concernant la remise en suspension des microorganismes et des bactéries en particulier. Dans ce contexte, les objectifs de la thèse sont de quantifier la vitesse de dépôt sec en fonction de la taille des particules et des principaux paramètres micrométéorologique dans la gamme 1,5 nm – 1,2 µm. Le second objectif est de documenter les processus d’émission des bactéries / The particles emitted into the atmosphere during chronic or accidental release by the nuclear plants can be subjected, after dispersion, to vertical flows by dry weather: dry deposition and resuspension. Vertical flows in dry weather are characterized by the vertical transfer rate, which is the ratio between the particle flux and the atmospheric concentration of the aerosol in the vicinity of the surface. When this speed is positive, it is a dry deposition rate (Vd in m.s-1) and conversely, when it is negative, it is a transmission rate. It is important to study their dry deposition in a prairial environment. Indeed, the products resulting from this environment are a component of the human food chain via livestock. For particles less than 1 μm, there is a lack of experimental data, which results in uncertainty about the results of the models, which can reach up to two orders of magnitude. In addition, there are no in situ deposition rate measurement data available for particles less than 10 nm. These particles are derived from the gas / particle conversion (nucleation) and may relate to certain radionuclides such as iodine (129, 131I).After their deposition, these radionuclides can be resuspended under the effect of the stress submitted by the wind on the canopy. Such a phenomenon is suspected around the Fukushima nuclear power plant. The aerosol resuspension processes are characterized by the vertical transfer rate (m.s-1) but also by the re-suspension coefficient (Ks in m-1) which is the ratio of atmospheric concentration to surface concentration of particles. Relative uncertainties of 2 to 3 orders of magnitude on the resuspension coefficients exist. The resuspension concerns all the particles present on the canopy, whether they are inert or living (fungi, bacteria, yeasts, etc.). Unlike inert particles, these living particles can assimilate and concentrate radionuclides. However, there is very little data on the resuspension of microorganisms and bacteria in particular. In this context, the objectives of the thesis are to quantify the dry deposition rate as a function of the particle size and the main micrometeorological parameters in the range 1.5 nm - 1.2 μm. The second objective is to document the processes of emission of the bacteria

<p>Ultrafine particles (UFP) emitted by traffic have been associated with health risks for people living and working near major roadways. Studies have shown that people living in near-roadway communities experience higher risk of aggravated asthma, respiratory diseases and even childhood leukemia. Sharp concentration gradients of UFP have been reported near major highways with the concentration decreasing rapidly away from the road. Dispersion of UFP downwind of a road depends on many parameters, such as the atmospheric stability and wind speed. Presence of different structures such as noise barriers and vegetation can greatly influence the dispersion and downwind concentrations of UFP. These structures can block the traffic emissions and increase vertical mixing. In addition, vegetation can reduce UFP by deposition processes. Two sets of experiments were conducted in this thesis to investigate the effect of barriers on UFP deposition and dispersion. </p><p>The first set of experiments was performed in a wind tunnel facility to address UFP deposition to vegetation barriers solely. Two analytical models were proposed to characterize UFP dry deposition to vegetation measured during the wind tunnel experiment. The first model was derived from the filtration theory to explain UFP dry deposition to pine and juniper branches. The model agrees well with the experimental data indicating that pine and juniper branches can be treated as fibrous filters. The fiber diameters of pine derived from the experimental data were also similar to the physical diameters of pine needles; thus, providing further evidence that vegetation can be regarded as fibers. The second model was derived from the continuity equation and can predict the branch-scale dry deposition of UFP using conventional canopy properties such as the drag coefficient and leaf area density. Both models agree with the measurement results to within 20%.</p><p>The second set of experiments was done in three near-roadway environments to investigate the effects of barriers on the dispersion and dry deposition of UFP. We used mobile and stationary measurements to obtain the spatial and temporal variability of UFP. Both mobile and stationary measurements indicated that vegetation and noise barriers can reduce downwind UFP concentrations through dispersion and dry deposition by 20-60 %. </p><p>In conclusion, the effect of barriers on UFP dispersion and deposition has been characterized in this thesis. Two analytical models were also proposed from the wind tunnel experiments to characterize dry deposition and agreed well with the measurement results. The analytical model could benefit future climate and air quality models.</p> / Dissertation

Polycyclic aromatic hydrocarbons(PAHs) are one of major classes of organic pollutants that transport through air-sea exchange in the environment. The objectives of this study were to quantify the PAHs concentrations in air and seawater and calcu-late the exchange fluxes by using Whitman¡¦s two-film mode. Spatial and temporal distributions were also determined through the sampling strategy of this study. In ad-dition, particulate concentrations in the ambient air were used to estimate the dry de-position fluxes of PAHs. Seasonal fluxes of PAHs in Gao-Ping coastal areas ranged from -2020 to +320 ng/m2day. The net gas exchange fluxes were negative (net absorption) in August, No-vember and March but positive (net volatilization) in May at Kaohsiung Harbor (KH), Off Shore (OFS) and Gao-ping River Estuary (GRE). Howerer negative exchange fluxes were found in each sampling month at Liu-Chiu Isle (LCI). In contrast, Lanyu Isle (LI) showed a different tend in exchange fluxes. It¡¦s exchange fluxes were all positive in each sampling month and ranged from the +121 to +1020 ng/m2day. Mostly the net fluxes of low molecular weight PAHs were volatile; while high molecular weight PAHs were absorptive. The compound with highest flux was mostly phenanthrene, therefore, it dominates the gas exchange fluxes in Gao-Ping coastal areas. The highest average net gas exchange fluxes among stations were observed at LCI (-1650 ng/m2day) and decreased in the following order: GRE (-932 ng/m2day), KH (-824 ng/m2day), OFS (-523 ng/m2day), LI (+358 ng/m2day). Dry particle deposi-tion fluxes were higher in November and March. The high molecular weight PAHs were found predominant in these particles. Even adding up with the wet deposition, the magnitude of total deposition fluxes(dry+wet) were still lower than those of gas exchange. Therefor, gas exchange is the main transport pathway for PAHs in Gao-Ping coastal areas. By identifying composition patterns of PAHs in each sample, source of PAHs in dissolved phase were mainly from traffic emission. However, KH is indicative of in-dustrial and petrogenic souces; while grass and wood combustion and petrogenic might be the dominant source of PAHs at LI. In gas phase, sources of PAHs were mostly from combustion, including traffic emission and diesel combustion. Finally, the transport pathway of the airflow was analyzed through back trajectory analysis. The results show that the PAH concentrations in gas phase might be affected by re-gional pollution in August and May, and long-rang atmospheric transport in March at Gao-Ping coastal areas and LI. Local origin was suggested for PAHs from Gao-Ping coastal areas in November and March.

In this work, wet deposition samples were collected at Middle East Technical University campus, Ankara, between December 2000 and May 2002. Snow samples were collected from 50 grids in January, 2001 in Ankara to investigate dry deposition of PAHs. The collected samples were preconcentrated by Solid Phase Extraction and ultrasonic extraction tecniques. Extraction methodologies were improved prior to analysis of samples. Extracted samples were analyzed by Gas Chromotography-Mass Spectrometry for 14 Polycyclic Aromatic Hydrocarbons. Selected Ion Monitoring mode was used throughout the analysis. Phenanthrene, fluoranthene, pyrene and benzo (b+k) fluoranthene were found to be dominant PAHs in wet deposition samples. Seasonal variation of PAHs were observed having higher concentrations in winter period. Meterological parameters were also examined together with PAH concentrations. Contribution of PAHs coming from North East and South West direction were found to be dominant. Wet deposition fluxes were calculated and compared with other urban sites. Wet deposition fluxes are lower than industrial sites and comparable with urban sites in Europe. PAH ratios and factor analysis results demostrated combustion and traffic emissions are major sources of pollutants in the city. Dry deposition of PAHs were invesigated using snow as a natural collecting surface. Dry deposition fluxes calculated using snow surface are compareble with other similar sites. Dry deposition pollution maps of PAHs were drawn by MapInfo software and it was observed that the major pollution regions are the localities where low income families live and low quality coal used for heating purpose. Ratio calculations showed that the central parts of the city is mostly affected from traffic emissions while coal emissions are dominating at the other parts of the city. Factor analysis applied to data set and 6 factors distinquished as coal, soil, traffic, oil combustion, mixed combustion and road dust.

In this work, dry deposition of metals is investigated in an urban area / city of Ankara using snow as a surrogate surface. Two sampling campaigns were conducted to determine dry deposited amount of 13 species namely / H+, Na, K, Al, Mg, Fe, V, Cd, Cr, Cu, Pb, Zn, Ni. First sampling was performed after a major snow fall in Ankara in January 2001, from 4 points according to a predetermined sampling procedure in order to assess background composition of snow. After 12 days, snow samples were collected from 54 points. All samples are filtered, digested and divided into two aliquots in order to investigate soluble and insoluble fractions separately. Temporal changes of snow showed that snow is a good surrogate surface for dry deposition of metals and provide multifunctional informative data. Pollution maps of the city are drawn using Mapinfo software to investigate spatial pollution distributions. Factor analysis are applied and five main factors for these elements are found, indicating three main sources as traffic, soil and combustion. Enrichment factor calculations showed that Ni, Ca, Pb, Zn, Ni, Cu and Cd are highly enriched pointing out the anthropogenic sources affecting the city atmosphere drastically.