Tropical cyclone (TC) intensity change is governed by internal dynamics (e.g. eyewall contraction, eyewall replacement cycles, interactions of the inner-core with the rainbands) and environmental conditions (e.g. vertical wind shear, moisture distribution, and surface properties). This study aims to gain a better understanding of the physical mechanisms responsible for TC intensity changes with a particular focus to those related to the vertical wind shear and surface properties by using high resolution, full physics numerical simulations. First, the effects of the vertical wind shear on a rapidly intensifying storm and its subsequent weakening are examined. Second, a fully coupled atmosphere-wave-ocean model with a sea spray parameterization is used to study the impact of sea spray on the hurricane boundary layer. The coupled model consists of three components: the high resolution, non-hydrostatic, fifth generation Pennsylvania State University-NCAR mesoscale model (MM5), the NOAA/NCEPWAVEWATCH III (WW3) ocean surface wave model, and theWHOI threedimensional upper ocean circulation model (3DPWP). Sea spray parameterizations were developed at NOAA/ESRL and modified by the author to be introduced in uncoupled and coupled simulations. The model simulations are conducted in both uncoupled and coupled modes to isolate various physical processes influencing TC intensity. The very high-resolutionMM5 simulation of Hurricane Lili (at 0.5 km grid resolution) showed a rapid intensification associated with a contracting eyewall. Changes in both the magnitude and the direction of the vertical wind shear associated with an approaching upper-tropospheric trough were responsible for the weakening of the storm before landfall. Hurricane Lili weakened in a 5-10 m/s vertical wind shear environment. The simulated storm experienced wind shear direction normal to the storm motion, which produced a strong wavenumber one rainfall asymmetry in the downshear-left quadrant of the storm. The rainfall asymmetry was confirmed by various observations from the TRMM satellite and the WSR-88D ground radar in the coastal region. The increasing vertical wind shear induced a vertical tilt of the vortex with a time lag of about 5-6 hours after the wavenumber one rainfall asymmetry was first observed in the model simulation. Other key factors controlling intensity and intensity change in tropical cyclones are the air-sea fluxes. Accurate measurement and parameterization of air-sea fluxes under hurricane conditions are challenging. Although recent studies have shown that the momentum exchange coefficient levels off at high wind speed, little is known about the high wind behavior of the exchange coefficient for enthalpy flux. One of the largest uncertainties is the potential impact of sea spray. The current sea spray parameterizations are closely tied to wind speed and tend to overestimate the mediated heat fluxes by sea spray in the hurricane boundary layer. The sea spray generation depends not only on the wind speed but also on the variable wave state. A new spray parameterization based on the surface wave energy dissipation is introduced in the coupled model. In the coupled simulations, the wave energy dissipation is used to quantify the amount of wave breaking related to the generation of sea spray. The spray parameterization coupled to the waves may be an improvement compared to sea spray parameterizations that depends on wind speed only.

No description available.

Particulate matter (PM) suspended in air varies in size from nanometers to micrometers and contains a wide range of chemical components, including organic compounds, black carbon (soot), inorganic minerals and metals. Atmospheric aerosols are generated from either primary sources like volcanic eruptions, re-suspended soil dust, sea spray, vegetative detritus, fossil fuel and biomass combustion emissions; or secondary atmospheric reactions via gas-to-particle conversion of atmospheric gases. Particle size, abundance, and chemical composition determine how a particle interacts with light and other atmospheric constituents (e.g. gases, water vapor) in addition to its impact on human health. While atmospheric scientists have been working on characterizing atmospheric aerosols for many years, major gaps persist in understanding the properties of many globally-important sources. This dissertation provides new understanding of the chemical composition of biomass burning and sea spray aerosols. PM emissions from biomass burning vary by fuel, and depend on fuel type and composition, moisture content, and combustion conditions. Although biomass smoke is critically important in global climate and local-regional health impacts, the physical and chemical composition of biomass burning aerosol is still not fully understood in the case of peat, agricultural residues and cooking fires. The Fire Laboratory at Missoula Experiments (FLAME) were designed to fulfill these gaps to improve our understanding in both historically undersampled and well-studied fuels while adding new instrumentation and experimental methods to provide previously unavailable information on chemical properties of biomass burning emissions. Globally-important biomass fuels were combusted in a controlled environment, and PM was chemically characterized to compute fuel based emission factors (EF) as the amount of chemical species released per unit mass of fuel burned. We showed that chemical composition of PM varies for different fuel types and certain fuels types (e.g., peat and ocote) emit considerably high concentrations of polycyclic aromatic compounds that are associated with negative health effects. We also showed that PM from biomass smoke contains fluoride for the first time, at approximately 0.1% by weight. With respect to the annual global emissions of PM due to biomass burning, this makes biomass burning an important source of fluoride to the atmosphere. Further, peatland fire emissions are one of the most understudied atmospheric aerosol sources but are a major source of greenhouse gases globally and cause severe air quality problems in Asia. This thesis provides the first field-based emissions characterization study, for samples collected at peat burning sites in Central Kalimantan, Indonesia. Using these EFs and estimates of the mass of fuel burned, it was estimated that 3.2 - 11 Tg of PM2.5 were emitted to atmosphere during 2015 El Niño peat fire episode which is ~10 % of estimated total annual PM flux for biomass burning. Overall, these studies computed more representative EFs for previously undersampled sources like peat, and previously unidentified chemical species like fluoride that can be used to update regional and global emission inventories. The concentration and composition of organic compounds in sea spray aerosol (SSA) alters its optical properties, hygroscopicity, cloud condensation, and ice nucleation properties and thus affects Earth’s radiative budget. In the past, SSA has been difficult to characterize, because of low concentrations relative to background pollutants. Nascent SSA was generated during a mesocosm, using a wave-flume at the University of California, San Diego and was characterized for saccharides and inorganic ions in order to assess their relative enrichment in fine (PM2.5) and coarse (PM10-2.5) SSA and sea surface microlayer (SSML) relative to seawater. For the first time, we showed that saccharides comprise a significant fraction of organic matter in fine and coarse SSA contributing 11 % and 27 %, respectively. Relative to sodium, saccharides were enriched 14-1314 times in fine SSA, 3-138 times in coarse SSA, but only up to 1.0-16.2 times in SSML. The saccharide and ion concentration in SSML and persistent whitecap foam was quantitatively assessed by another mesocosm study performed under controlled conditions. We demonstrated that relative to sodium, saccharides were enriched 1.7-6.4 times in SSML and 2.1-12 times in foam. Higher enrichment of saccharides in foam over the SSML indicates that surface active organic compounds become increasingly enriched on aged bubble film surfaces. Similarly, we showed that fine SSA contains saccharides characteristic of energy-related polysaccharides, while coarse SSA contains saccharides that are characteristic of structure-related polysaccharides. The ultrafiltration studies showed that structure-related polysaccharides effectively coagulate to form large particulate organic matter and size is likely the reason for their exclusion from small SSA. The enrichment of organic species in SSML, foam and SSA led to an enrichment of inorganic ions probably through chelation with organic molecules. Mean enrichment factors for major ions demonstrated the highest enrichment in fine SSA for potassium (1.3), magnesium (1.4), and calcium (1.7). Consequently, due to these organic and inorganic enrichments, SSA develops a significantly different chemical profile compared to seawater. These improved chemical profiles of SSA should be used to develop laboratory proxies to further study the transfer of organic matter across the ocean-air interface and the physical properties of SSA. . Overall, the results presented in this dissertation provide new chemical profiles for previously understudied emission sources like peatland fire emissions, and previously unquantified chemical species like F- in biomass burning emissions and enrichment of saccharides and ions in SSA. These data could be used in updating regional and global emission inventories, atmospheric modeling and human exposure studies.

Currently, there exists a great deal of uncertainty regarding atmospheric aerosols and the role that they play within the Earth’s atmosphere. It is known that atmospheric aerosols can play a role in the Earth’s climate by scattering and absorbing solar radiation or acting as a cloud condensation nuclei. The purpose of this work is to obtain an improved understanding of the chemistry of atmospheric aerosols to better determine their impacts the environment, air quality, and climate. This work revolves around one specific type of atmospheric aerosol, i.e. sea spray aerosol. Sea spray aerosol is generated via breaking waves, through wind-driven mechanisms. Ocean water covers roughly 71% of the Earth’s surface, and from this over 1300 Tg of sea spray aerosols is emitted into the atmosphere every year. However, until recently, the study of sea spray was very challenging and often inconclusive due to the inability to filter background particles out. In this work, the understanding of sea spray aerosol is progressed by taking a two-pronged approach. First, this work focuses on the study of model systems of simple ocean surfactants and NaCl and the change in chemistry that occurs when the two are in the presence of each other. Second, sea spray samples generated during a biological bloom are isolated and analyzed. Using this two pronged approach, it is shown that model systems can provide supporting evidence for hypotheses created from trends discovered in more complex samples. Finally, common aerosol generation, storage, and analysis techniques are studied in order to improve our understanding of their effects on aerosol particles.

Aerosols are important atmospheric constituents that impact the Earth's radiative balance and climate. The detailed knowledge of the aerosol optical properties is required for a comprehensive analysis of the impacts of aerosols on climate. Mie theory is often used in satellite and ground-based retrieval algorithms to account for atmospheric mineral dust. However, the approximations used in Mie theory are often not appropriate for mineral dust and can lead to errors in the optical properties modeling. Analytic models based on Rayleigh theory that account for particle shapes can offer significant advantages when used to model infrared (IR) extinction of mineral dust. Here, the IR optical properties of some components of mineral dust, authentic dust samples and minerals processed with organic acids were investigated. Detailed characterization of the particles through online and offline methods of analysis that include IR extinction spectroscopy, micro-Raman spectroscopy and scanning electron microscopy was performed. Analysis of the IR extinction spectra and spectral simulations showed that the positions of the peaks and the shapes of the bands of the IR characteristic features are not well simulated by Mie theory in any of the samples studied. The resonance peaks were consistently shifted relative to the experimental spectrum in the Mie simulation. Rayleigh model solutions derived for different particle shapes better predicted the peak positions and band shapes of experimental spectra. To fill the gaps in the refractive index data for atmospherically relevant organic compounds in the IR region optical properties of atmospherically relevant carboxylic acids and humic-like substances using the IR extinction spectra and size distributions measured in the laboratory were determined. In addition to properties of mineral dust this dissertation focuses on properties of sea spray aerosol. Chemical and elemental composition of individual sea spray aerosol particles were studies using micro-Raman spectroscopy, mass-spectrometry and X-ray spectroscopy to provide insights into the biochemical processes that give rise to classes of organic molecules that make up these aerosol particles. The results suggested that degradation of biota (bacteria and diatoms) present in sea water led to lipopolysaccharides and extracellular polymeric substances that further degraded down to carbohydrates and fatty acids. Solubility of the resulting organic species seemed to play a role in their transfer to the aerosol phase. Furthermore, water uptake and hygroscopic growth of multi-component particles were studied. Understanding the interactions of water with atmospheric aerosols is crucial for determining their size, physical state, reactivity, and therefore for aerosol interactions with electromagnetic radiation and clouds. It was determined that particles composed of ammonium sulfate with succinic acid and of mixture of chlorides typical for marine environment show size dependent hygroscopic behavior. Microscopic analysis of the distribution of components within the aerosol particles showed that the observed size dependence is due to the differences in the mixing state. The composition and water uptake properties of sea spray aerosol particles were also measured during a phytoplankton bloom. The results showed that water uptake properties were directly related to the chemical composition of the particles and hygroscopicity decreased with increase in the fraction of water insoluble organic matter emitted during phytoplankton bloom. Finally, multiple methods of particle size, phase and shape analysis were compared and the results showed that the techniques that operate under ambient conditions provide the most relevant and robust measurement of particle size. Additionally, several storage methods for substrate deposited aerosol particles were evaluated and it was determined that storing samples at low relative humidity led to irreversible changes due to sample dehydration while sample freezing and thawing leads to irreversible changes due to phase changes and water condensation. Therefore it is suggested that samples used for single-particles analysis should be stored at ambient laboratory conditions, or near conditions which they were collected, in order to preserve the sample phase and hydration state. The results presented in this dissertation provide insight into physicochemical properties of atmospheric aerosols and help us better understand the role of aerosol particles in the Earth's atmosphere.

No description available.

Perfluoroalkyl acids (PFAAs) are man-made chemicals which have been observed in the global environment, even in locations far away from where they are emitted. These persistent substances are taken up in humans and biota and may have toxic effects. Knowledge about how PFAAs are dispersed in the environment is needed to discern strategies to manage their sources and to evaluate the efficacy of adopted legislation. This thesis aimed to increase our understanding of the sources of PFAAs to the atmosphere and how PFAAs are transported in air. The results of Paper I demonstrated that gaseous perfluorooctanoic acid (PFOA) sorbs to typical glass fibre filters (GFFs) used in high-volume air sampling of PFAAs. As a consequence, the fraction of gaseous PFOA present in sampled air is underestimated, while the fraction of PFOA associated with aerosols is overestimated. Replacing GFFs with filters deactivated through silanisation and siliconisation did not eliminate this sampling artefact and is therefore not recommended as a means to determine the gas-particle partitioning of PFAAs. In Paper II, monitoring of the mass of PFOA transferred from water solutions of pH 0.2-5.5 demonstrated that the acid dissociation constant of linear PFOA and the four most ubiquitous branched PFOA isomers is around or below 1. Furthermore, the results demonstrated that the presence of counter ions and organic matter in water retarded, rather than enhanced, the volatilisation of PFOA. Therefore, volatilisation of all isomers of PFOA from environmental waters is expected to be negligible. To further study the transfer of PFAAs from environmental waters to air, Paper III simulated the process of sea spray generation in the laboratory. Strong enrichment of PFAAs was observed from bulk water to the surface microlayer and to aerosols. The enrichment increased with PFAA chain length, indicating that this process is of greater importance for more surface active substances. The highest enrichment was observed in aerosols &lt; 1.6 µm, which can travel over long distances if not rained out. Based on the measured aerosol enrichment factors we estimated that approximately 70 metric tonnes of PFAAs are aerosolised from the global oceans yearly and that 3% of this mass is deposited in terrestrial environments. Paper IV reported the occurrence of branched PFOA isomers in deposition sampled in five geographical locations. The presence of these isomers demonstrated that atmospheric transformation of fluorotelomer alcohols is not the only ongoing source of PFAAs to air. We hypothesised that, additionally, both sea spray aerosols and direct emissions from manufacturing sources contributed to the contamination of the precipitation on different spatial scales. Although further research is required to determine the relative importance of different sources to the atmosphere locally and globally, this thesis has substantially advanced the state-of-the-science by i) demonstrating the significance of an air sampling artefact discussed as an uncertainty in the scientific literature over the past decade, ii) definitively ruling out volatilisation from environmental waters as a source of PFOA to air, iii) demonstrating transfer of PFAAs from seawater to air via sea spray aerosols and thus quantifying the environmental importance of this process, and iv) ultimately demonstrating that several types of sources of PFAAs impact the global atmosphere and thus PFAA contamination patterns in precipitation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

La nucléation hétérogène de la glace est un processus, entre autres, qui concerne les phénomènes complexes de l'Atmosphère terrestre, cependant son impact est déterminant pour les propriétés et le temps de vie des nuages : ce processus affecte l'épaisseur optique et la durée de vie des nuages en phase mixte et froide et il est responsable d'une proportion significative des précipitations à l'échelle mondiale. La nucléation hétérogène de la glace est liée à la présence de particules d'aérosol spécifiques, nommées noyaux glaçogènes (acronyme INP depuis l’anglais), avec la propriété de réduire l’énergie de seuil exigée pour la formation des cristaux de glace, et dont le rôle est influent pour des températures de nuage >-38 °C. Dans les dernières décennies, des avancements significatifs ont été faits dans la description des noyaux glaçogènes, cependant leur compréhension reste incomplète et ceci influence les incertitudes sur les estimations de forçage radiatif dans les modèles climatiques. Il manque un grand nombre d’observations sur les distributions et propriété des 'INP' à l’échelle globale, spécialement en région éloignée. Dans la première partie de cette thèse, sont présentées des mesures de noyaux glaçogènes faites à l'Observatoire Climatique Italien "O. Vittori" sur la Montagne Cimone (2165 m au-dessus du niveau de la mer), pendant le printemps 2014 et l’automne 2015, sous les projets Bacchus et Air Sea Lab. Pour la première fois des mesures de INP hors ligne, reliés à un site de haute altitude du bassin méditerranéen sont présentées. Pendant la période du 19 au 29 mai 2014, une autre campagne a eu lieu en parallèle à la station San Pietro Capofiume, un site rural de basse altitude dans la Vallée du Po. Pendant quelques jours, les deux campagnes ont été concernées par un phénomène de Transport de Poussière Saharienne, qui a été enregistré simultanément dans la station de bas et de haute altitude. Nous avons examiné la concentration atmosphérique de INP activés à travers une congélation par condensation de vapeur (à -18°C et au-dessus de la pression de vapeur saturante). Dans la deuxième partie de cette thèse, sont présentées les observations qui ont été menées pendant la campagne arctique Parcs-Maca, dans la période de transition entre la nuit polaire et le jour polaire. Pour la première fois on reporte la caractérisation des propriétés glaçogènes et physiques/chimiques de l’aérosol marin primaire Arctique, dans une approche de génération contrôlée en laboratoire, qui a été combinée à une expérience de mesocosm. Le but de l'expérience de mesocosm était d'adopter une approche pluridisciplinaire afin d’étudier l'effet de la pollution marine sur les émissions marines. Nous avons trouvé une diminution modérée mais significative de la concentration de noyaux glaçogènes dans l'eau de mer polluée (par rapport à l'eau de mer du contrôle) pour des noyaux glaçogènes actives en congélation par immersion entre -8.5 et -19 °C. En ce qui concerne le spray marin, nos mesures indiquent une relation parmi les INP actifs à des températures chaudes (en congélation par immersion et au-dessus de -15 °C) et un enrichissement du Calcium détecté dans les filtres PM1 (suivi par un apparent épuisement du Chlorure). Sur la base de nos observations et des résultats publiés en littérature, quelque indication a été suggéré sur la nature de ces noyaux glaçogènes marins. En conclusion, les mesures effectuées dans cette thèse fournissent des nouvelles informations sur les concentrations de noyaux glaçogènes pour des particules d’aérosols en régions éloignées (un observatoire à haute altitude dans la région méditerranéenne centrale) et par rapport à une source spécifique (le spray marin Arctique). / Heterogeneous ice nucleation is one element inside the overall complexity of the Earth's atmosphere, however, it has a profound impact on our representation of cloud properties: this process affects the optical thickness and lifetime of mixed-phase clouds and cirrus clouds, and it is responsible for a significant proportion of precipitations formed globally. Heterogeneous ice nucleation is related to the presence of specific aerosol particles, named ice nuclei particles (INP), with the unique ability of lowering the energy barrier required for the formation of ice crystals, especially where cloud’s temperatures are >-38 °C. In the last decades, significant advancements have been made to the fundamental understanding of ice nucleation, however the lack of knowledge on the cloud ice phase still contributes to major uncertainties in climate model prediction of radiative forcing. This is partly due to limited observational data quantifying INP distributions and properties all over the world, especially in remote locations. In the first part of this thesis, field observations of ice nucleating particles have been performed at the Italian Climate Observatory “O. Vittori” on Mountain Cimone (2165 m above sea level), in the spring 2014 and autumn 2015, within the Bacchus and Air Sea Lab projects. For the first time we report the results of offline INP measurements, performed at a high altitude site within the Mediterranean basin. In the period 19-29 May 2014, a parallel campaign took place at the low-altitude station San Pietro Capofiume, a rural site in the Po Valley. The two campaigns were concerned, for a few days, by a Saharan Dust transport Event, which was recorded simultaneously at the high and the low-level station. We investigated the ambient number concentration of INP under condensation freezing activation mechanism (at -18 °C and above water saturation). In the second part of this thesis, we present the observations that were performed during the Arctic campaign Parcs-Maca, in the period of transition among the polar night and the polar day. We could characterise for the first time the ice nucleating and physical/chemical properties of the Arctic Primary Marine Aerosol, in a laboratory-controlled generation approach, that was combined to a mesocosm experiment. The aim of the mesocosm experiment was to adopt a multidisciplinary approach to study the effect of marine pollution on marine emissions. We found a moderate but significant decrease of the ice nuclei concentration in the polluted seawater (with respect to the control seawater) recorded in the freezing range between -8.5 and -19 °C and activated through immersion-freezing. Within the seaspray our measurements have indicated a relation among INP active at warm temperature (above -15 °C through immersion-freezing) and a calcium enrichment detected in PM1 filters (and followed by an apparent Chloride depletion). On the basis of our observations, and the results reported from other studies, a few suggestions on the nature of these marine ice nuclei have been suggested. In summary, the measurements made for this thesis provide new information on the concentrations of ice nuclei in ambient aerosol particles in remote regions (a high-altitude observatory in the central Mediterranean region) and in relation to a specific source (the Arctic sea spray).

Aerosol particles affect the Earth’s climate, although their impact is associated with large uncertainties. Primary marine aerosol represents a significant fraction of the global aerosol budget considering the Earth’s 70-percentage coverage by oceans. They are produced when bubbles burst at the ocean surface and can consist of sea salt, organic matter and bacteria. An experimental approach was here used to investigate the primary marine aerosol production from the bubble-bursting mechanism using water from four different geographical locations. The main findings include: Similar and stable aerosol number size distributions at all locations, centered close to 0.2 μm. Largely varying aerosol organic fractions, both with size and location. Clear tendency for increased water temperature to negatively influence the aerosol production. No covariance between surface water chlorophyll α and aerosol production on a 10-minute time scale, although decreased aerosol production was observed at times of elevated phytoplankton activity on longer time scales. Mainly external mixtures of sea salt and organics was observed. A high tendency for colony-forming marine bacteria to use bubble-bursting to reach the atmosphere. A clear diurnal cycle in aerosol production was found for both laboratory produced aerosol and in-situ aerosol fluxes, probably biologically driven. The first near coastal sea spray fluxes with limited fetch and low salinity. While the primary marine aerosol spectral shape is stable, emission concentration varies with environmental parameters. Above that, the organic fraction of the aerosol varies largely between locations. This shows that observations of primary marine aerosol emissions not necessarily can be applied to large time- or spatial scales. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: Manuscript. Paper 4: Manuscript.

252 f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-03-27T15:57:52Z No. of bitstreams: 1 Tese_Doutorado_Adriana_Moreno.pdf: 8730190 bytes, checksum: 56efa36bc67f97b073c9b56409edff28 (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-06-05T15:51:59Z (GMT) No. of bitstreams: 1 Tese_Doutorado_Adriana_Moreno.pdf: 8730190 bytes, checksum: 56efa36bc67f97b073c9b56409edff28 (MD5) / Made available in DSpace on 2013-06-05T15:52:00Z (GMT). No. of bitstreams: 1 Tese_Doutorado_Adriana_Moreno.pdf: 8730190 bytes, checksum: 56efa36bc67f97b073c9b56409edff28 (MD5) Previous issue date: 2012 / CAPES / O aporte de espécies químicas para a atmosfera representa importante mecanismo dos processos hidrogeoquímicos, tornando-se muito significativo na região semi-árida, que sofre continuamente com elevada frequência de períodos secos, além dos problemas socioeconômicos. Esta pesquisa objetivou estudar a influência do spray marinho na salinização das águas do Semi-Árido baiano. Amostragens de chuva e de material particulado atmosférico (MP) foram feitas em duas estações: Juazeiro, com águas subterrâneas salobras e Morro do Chapéu, com águas doces. Foram determinadas nas amostras de chuva concentrações de espécies inorgânicas, pH e condutividade. No MP foram avaliados os principais ions inorgânicos solúveis em partículas fracionadas por tamanho, utilizando um impactador em cascata, tipo Berner, de seis estágios: 0,06; 0,18; 0,55; 1,7; 4,9 e >14,9 μm. Isótopos estáveis do oxigênio-18 e deutério foram determinados na chuva como traçadores ambientais, analisados por espectrometria de massa, sendo avaliadas as razões Isotópicas (18O/16O e D/H). Ânions foram analisados por cromatografia iônica; NH3 por espectrofotometria molecular; Ca2+ e Mg2+ por espectrometria de absorção atômica com chama; Na+ e K+ por fotometria de chama. Os resultados obtidos mostraram na chuva de Juazeiro: pH entre 5,98 e 7,33, com média ponderada por volume (MPV) 6,80, sugerindo neutralização da acidez da chuva pela amônia ou por partículas básicas do solo, ou ainda, pelo spray marinho. A condutividade variou de 5,21 a 70,8 μS cm-1 e as concentrações molares médias iônicas, decresceram na seguinte ordem: Cl- > Ca2+ > NO3- > NH4+ > Na+ > K+ > Mg2+ > SO42- > H+. Em Morro do Chapéu o pH da chuva variou de 6,40 a 7,24, com MPV 6,75 e a condutividade de 4,58 a 19,1 μS cm-1. As concentrações molares médias iônicas decresceram na seguinte ordem: Cl- > NH4+ > Na+ > NO3- > Mg2+ > H+ > SO42- > K+ > Ca2+. Considerando as duas localidades, o nível de concentração das principais espécies inorgânicas no MP está na faixa de 13,6-26,9 nmol m-3 Cl-; 3,23-17,6 nmol m-3 NO3-; 2,87-11,0 nmol m-3 SO42- e 11,5-37,0 nmol m-3 Na+. O SO42- se distribui predominantemente na moda fina do MP atmosférico, indicando origem em transformações gás-partícula e/ou partícula-partícula. Cl- e Na+ se apresentam predominando na moda grossa, representando a contribuição do spray marinho. A técnica da análise de componentes principais (ACP) permitiu visualizar a influência marinha sobre as concentrações atmosféricas em ambas as estações, além de outras fontes (continentais naturais e antrópicas) exercendo controle sobre a atmosfera da região. Os resultados demonstram o potencial dos traçadores isotópicos determinados na chuva no entendimento do ciclo hidrológico na área de estudo: em Morro do Chapéu as águas de precipitação são na maior parte do tempo provenientes de locais mais distantes, enquanto que em Juazeiro, vem da própria região, embora frequentemente as massas de ar cheguem do litoral, mostradas pelas trajetórias reversas. A estimativa da contribuição do spray marinho na chuva é muito menor aí (56%) do que em Morro do Chapéu (92%). Apesar disso, em termos quantitativos pode-se concluir que a quantidade de spray marinho que chega à região é insuficiente para salinizar suas águas. Desta forma, a causa da salinização das águas em Juazeiro, deve ser atribuída à geologia local e aos processos de evaporação e concentração de sais. / Salvador