Cloud forming properties of ambient aerosol in the Netherlands and resultant shortwave radiative forcing of climate

This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second is indirect. Due to the scattering of solar light on aerosol particles the Earth surface receives less radiation and thus cools, which is called the direct aerosol effect.The indirect effect includes processes by which aerosols influence the radiation balance indirectly - via clouds. The indirect effect includes mechanisms by which anthropogenic aerosol particles enhance the reflectivity and prolong the life time of marine stratoform clouds by increasing their droplet number concentration. Anthropogenic aerosols were demonstrated to have a considerable cooling effect on climate, comparable in magnitude to that of the greenhouse gases, but opposite in sign. However, calculation of the aerosol radiative forcing is much more complex than that for the green house gases. This results in high uncertainties in the estimates of the effects of anthropogenic aerosols on climate.Both types of the aerosol radiative forcing and their magnitude, as estimated by the Intergovernmental Panel on Climate Change (IPCC), are discussed in Chapter 1. The aerosol radiative forcing is a regional phenomenon because of the limited life time of aerosols in the atmosphere. Thus, the aerosol effects should be assessed locally.In Chapter 2 chemical composition of local ambient aerosols in the size range relevant to the radiative forcing is discussed. It is shown that ammonium nitrate, which is omitted by the IPCC, is a major contributor to the direct, and perhaps to the indirect forcing. The contribution of this compound to the local direct forcing is equal to that of anthropogenic sulfate aerosols. Measurements of ammonium nitrate content in submicrometer aerosol are subject to artifacts due to the volatility of this compound. Automated techniques which were developed for artifact-free measurements of chemical composition of ambient aerosols are described.Aerosol particles composed of water-soluble salts increase their size at elevated relative humidities. The increase in size enhances light scattering by aerosol particles which in turn enhances the direct radiative forcing. Hygroscopic properties of aerosol particles also play a central role in cloud droplet formation and thus are also relevant for the indirect aerosol effect. Chapter 2 discusses the hygroscopic size changes and characteristic growth times. It is also demonstrated that hygroscopic growth may substantially enhance dry deposition of aerosol particles to forests.According to the IPCC the indirect aerosol effect is the most uncertain factor in the anthropogenic perturbation of the climate, with an uncertainty of the same magnitude as the total radiative effect by the greenhouse gases. One of the major uncertainties in the indirect effect is the unknown relation between the concentration of anthropogenic aerosol particles and the increase in droplet number concentration in clouds. In Europe only few measurements of the relation between the number of particles and the number of cloud droplets have been performed.It should be also noted that those measurements were performed with instruments that did not span the full range of aerosol sizes that is relevant for cloud formation. For this reason, the major part of the thesis was devoted to an experimental assessment of the cloud forming properties of ambient aerosol in the Netherlands. The indirect effect as well as factors controlling cloud droplet formation are discussed in Chapter 3.Chapter 4 describes the large flow-through cloud chamber in which cloud forming properties of ambient aerosol were studied. The advantage of a cloud chamber over in-situ measurements is the use of instrumentation which is too delicate for use in aircraft and the possibility to compare, simultaneously, the aerosol before and after cloud processing. The aerosol was characterized both in terms of its number concentration and size as well as its chemical composition with the emphasis on the amount of soluble material. The unique feature of the cloud chamber is its reproducible stable low supersaturations (around 0.1%) common for marine clouds.Aerosol monitors were used that measure the concentration of particles in the full range of sizes relevant for cloud formation. The unique large size and the high throughput flow of the chamber allowed unperturbed use of conventional cloud instrumentation for sizing and counting of droplets. Also high-flow cascade impactors for chemical analysis of aerosol were used. The cloud chamber was calibrated with artificially generated ammonium sulfate aerosol. This aerosol was selected because in anthropogenically influenced air in Western Europe most particles should consist of this compound. Experiments were done at different total aerosol number concentrations to check its influence on the number of resulting cloud droplets. A sub-linear relation between the aerosol and the droplet number concentrations was observed. The results of the tests with the reference aerosol were used for the interpretation of experiments with ambient aerosols.The cloud activation tests on ambient aerosol are discussed in Chapter 5. The cloud forming efficiency of the aerosols was assessed by comparing the number concentration of droplets formed in the cloud chamber with that found during the tests with the reference ammonium sulfate aerosol at the same number concentration. Similarly to the reference sulfate aerosol, a sub-linear relation between the aerosol and droplet number concentrations was observed. However, the deviation from a linear relation was stronger in the ambient aerosol. This suggested that about one third of the (anthropogenic) particles was water-insoluble. The measurements of the composition supported this hypothesis. This demonstrates the importance of hygroscopicity for cloud formation. It also shows that measurements of the solubility of (individual) particles should be done along with conventional measurements of aerosol size and number.The results of experiments discussed in Chapter 5 were used for an estimate of the local indirect aerosol radiative effect (Chapter 6). The difference between the droplet number concentration in clean marine air and the average droplet number concentration in polluted air was used to estimate the corresponding increase in cloud reflectivity which, in turn, was translated into local indirect aerosol effect. The data on the aerosol light scattering discussed in Chapter 2 are used to estimate the local direct radiative forcing. The estimated total (direct plus indirect) local aerosol radiative forcing is about 4 times higher than the forcing by the anthropogenic greenhouse gases but opposite in sign.</p

On transport phenomena and equilibration time scales in thermodenuders

This paper presents a theoretical and experimental investigation of thermodenuders that addresses two controversial issues: (1) equilibration time scales and (2) the need for an activated carbon (AC) denuder in the cooling section. We describe a plug flow model for transport phenomena in a TD, which can be used to simulate the rate of vapor build-up in the gas phase and the corresponding change in particle size distribution. Model simulations were found to have excellent agreement with experiments performed with pure and mixed dicarboxylic acid aerosols. Both simulations and experiments showed that the aerosols approached equilibrium within reasonable residence times (15 s–30 s) for aerosol concentrations and size distributions typical for laboratory measurements, and that volatility studies at sufficiently high aerosol loadings, therefore, need not resort to kinetic models for inference of thermodynamic properties. However, for size distributions relevant for ambient aerosols, equilibration time scales were much larger than residence times available with current TD designs. We have also performed dimensional analysis on the problem of equilibration in TDs, and derived a dimensionless equilibration parameter which can be used to determine the residence time needed for an aerosol of given size distribution and kinetic properties to approach equilibrium. It is also shown theoretically and empirically that aerosol volatility has no effect on the equilibration time scales. Model simulations and experiments showed that with aerosol size distributions relevant to both ambient and laboratory measurements re-condensation in the cooling section, with and without an AC denuder, was negligible. Thus, there is no significant benefit in using an AC denuder in the cooling section. Due to the risk of stripping volatile material from the aerosol, the use of AC denuders in the cooling section should be avoided. Finally, we present a rationale for why &amp;Delta;&lt;i&gt;C&lt;/i&gt; is the proper measure of volatility, while using mass fraction remaining (MFR) can be misleading

Light absorption by polar and non-polar aerosol compounds from laboratory biomass combustion

Fresh and atmospherically aged biomass-burning (BB) aerosol mass is mostly comprised of strongly light-absorbing black carbon (BC) and of organic carbon (OC) with its light-absorbing fraction – brown carbon (BrC). There is a lack of data on the physical and chemical properties of atmospheric BB aerosols, leading to high uncertainties in estimates of the BB impact on air quality and climate, especially for BrC. The polarity of chemical compounds influences their fate in the atmosphere including wet/dry deposition and chemical and physical processing. So far, most of the attention has been given to the water-soluble (polar) fraction of BrC, while the non-polar BrC fraction has been largely ignored. In the present study, the light absorption properties of polar and non-polar fractions of fresh and aged BB emissions were examined to estimate the contribution of different-polarity organic compounds to the light absorption properties of BB aerosols. In our experiments, four globally and regionally important fuels were burned under flaming and smoldering conditions in the Desert Research Institute (DRI) combustion chamber. To mimic atmospheric oxidation processes (5–7 days), BB emissions were aged using an oxidation flow reactor (OFR). Fresh and OFR-aged BB aerosols were collected on filters and extracted with water and hexane to study absorption properties of polar and non-polar organic species. Results of spectrophotometric measurements (absorption weighted by the solar spectrum and normalized to mass of fuel consumed) over the 190 to 900nm wavelength range showed that the non-polar (hexane-soluble) fraction is 2–3 times more absorbing than the polar (water-soluble) fraction. However, for emissions from fuels that undergo flaming combustion, an increased absorbance was observed for the water extracts of oxidized/aged emissions while the absorption of the hexane extracts was lower for the aged emissions for the same type of fuels. Absorption Ångström exponent (AAE) values, computed based on absorbance values from spectrophotometer measurements, were changed with aging and the nature of this change was fuel dependent. The light absorption by humic-like substances (HULIS) was found to be higher in fuels characteristic of the southwestern USA. The absorption of the HULIS fraction was lower for OFR-aged BB emissions. Comparison of the light absorption properties of different-polarity extracts (water, hexane, HULIS) provides insight into the chemical nature of BB BrC and its transformation during oxidation processes

Crystallization of authigenic carbonates in mud volcanoes at Lake Baikal

This paper presents data on authigenic siderite first found in surface sediments from mud volcanoes in the Central (K-2) and Southern (Malen’kii) basins of Lake Baikal. Ca is the predominant cation, which substitutes Fe in the crystalline lattice of siderite. The enrichment of the carbonates in the 13C isotope (from +3.3 to +6.8‰ for the Malen’kii volcano and from +17.7 to +21.9‰ for K-2) results from the crystallization of the carbonates during methane generation via the bacterial destruction of organic matter (acetate). The overall depletion of the carbonates in 18O is mainly inherited from the isotopic composition of Baikal water

Возраст грязевой брекчии грязев ых вулканов Академического хреб та озера Байка

Lake Baikal is the only freshwater reservoir on Earth with gas-hydrate accumulations in its bottom sediments, partly due to the activity of mud volcanoes. This paper describes a group of mud volcanoes recently discovered on the slope of the Academician Ridge between the northern and central Lake Baikal basins. Our analysis of diatom skeletons in the mud breccia sampled from the study area shows a high abundance of Cyclotella iris et var. These extinct species were also discovered in a core sample from BDP-98 borehole. Based on the biostratigraphic and seis-mostratigraphic correlations, the age of the mud breccia in the studied mud volcanoes ranges from the Late Miocene to the Early Pliocene (4.6 to 5.6 Ma). The correlations suggest that the material originated from a depth of less than 310 m below the lake bottom

Constraining Aerosol Optical Models Using Ground-Based, Collocated Particle Size and Mass Measurements in Variable Air Mass Regimes During the 7-SEAS/Dongsha Experiment

During the spring of 2010, NASA Goddard's COMMIT ground-based mobile laboratory was stationed on Dongsha Island off the southwest coast of Taiwan, in preparation for the upcoming 2012 7-SEAS field campaign. The measurement period offered a unique opportunity for conducting detailed investigations of the optical properties of aerosols associated with different air mass regimes including background maritime and those contaminated by anthropogenic air pollution and mineral dust. What appears to be the first time for this region, a shortwave optical closure experiment for both scattering and absorption was attempted over a 12-day period during which aerosols exhibited the most change. Constraints to the optical model included combined SMPS and APS number concentration data for a continuum of fine and coarse-mode particle sizes up to PM2.5. We also take advantage of an IMPROVE chemical sampler to help constrain aerosol composition and mass partitioning of key elemental species including sea-salt, particulate organic matter, soil, non sea-salt sulphate, nitrate, and elemental carbon. Our results demonstrate that the observed aerosol scattering and absorption for these diverse air masses are reasonably captured by the model, where peak aerosol events and transitions between key aerosols types are evident. Signatures of heavy polluted aerosol composed mostly of ammonium and non sea-salt sulphate mixed with some dust with transitions to background sea-salt conditions are apparent in the absorption data, which is particularly reassuring owing to the large variability in the imaginary component of the refractive indices. Extinctive features at significantly smaller time scales than the one-day sample period of IMPROVE are more difficult to reproduce, as this requires further knowledge concerning the source apportionment of major chemical components in the model. Consistency between the measured and modeled optical parameters serves as an important link for advancing remote sensing and climate research studies in dynamic aerosol-rich environments like Dongsha

Active destabilisation of gas hydrate accumulations in Lake Baikal by tectonically induced fluid-flow

Multi-channel seismic profiling and deep drilling have evidenced the presence of gas hydrates in Lake Baikal, Siberia. They occur in the deep basins around the large Selenga River Delta. The presence of the hydrates is evident on seismic records by virtue of a distinct high-amplitude, reversed-polarity, cross-cutting BSR. Locally, however, the BSR shows a very anomalous behaviour. In the vicinity of some of the main, active, intra-basin faults, its depth strongly fluctuates, with undulations (positive as well as negative compared to background positions) and vertical displacements of several hundreds of ms TWT. Locally, the BSR is even entirely disrupted by vertical ‘chimneys’ that reach up to the lake bottom.High-resolution deep-tow side-scan sonar mosaics over one of such areas of deformed and disrupted BSR show a cluster of morphological irregularities on the lake floor, in contrast to areas above a regular BSR where the lake floor is absolutely regular and flat. Four large irregularities - aligned parallel to the fault – were discovered, one of them coinciding with one of the ‘chimneys’. They were mapped in detail by bathymetric sounding and proved to be either elevations (mud volcanoes ?) or depressions (craters) at the lake floor. Echosounding has also shown venting associated with these features, which is evidenced by an acoustically non-transparent plume, reaching 10-25 m above the bottom (in other places in a similar context plumes were observed of > 200 m of height). CTD-profiling, which shows very little change in bottom-water temperature at the venting sites, suggests that the plumes represent cold seeps.Heat-flow values measured over the area show a good correlation with changes in BSR depth: values vary between 50-60 mW/m² to 80-90 mW/m². In the craters, heat-flow values are highest, but they do not exceed 165 mW/m². Our observations suggest that the Baikal hydrates are locally - along particular segments (about 15 km long) of active faults - destabilizing by tectonically controlled upward flow of fluid and heat, and that this results in active venting of gasses and/or fluids at the lake floor

Гиалуроновая кислота как предиктор обострений хронической обструктивной болезни легких профессиональной этиологии

The frequency of exacerbations of chronic obstructive pulmonary disease (COPD) is one of the main factors determining the outcome. The search for biomarkers which reflect the risk of exacerbations is one of the urgent scientific and practical objectives. Aim. The study aimed to analyze the relationship between the serum concentration of hyaluronic acid (HA) and the frequency of exacerbations of occupational COPD caused by exposure to silica dust and to substantiate the use of HA as a predictor of exacerbations of COPD. Methods. 78 individuals with a diagnosis of occupational COPD were examined. Respiratory function was assessed based on forced vital capacity of the lungs (FVC, %), the forced expiratory volume in 1 second (FEV1, %) and the calculated ratio of these parameters (FEV1/FVC, %), i.e., modified Tiffno index. The serum concentration of hyaluronic acid (ng/ml) was determined in all individuals using solid-phase enzyme-linked immunosorbent assay (ELISA). The absolute blood level of eosinophils (cell/μl) was determined by a unified method of morphological study of hemocytes with white blood cell differential count. Results. Serum HA concentration in patients with occupational COPD with frequent exacerbations was 25% higher than in the patients with rare exacerbations (the difference was statistically significant; р = 0,004). The analysis of the obtained data showed that the most significant moderate correlation was found between the level of HA and the frequency of COPD exacerbations (direct relationship, r = 0.32; p &lt; 0.05), and FEV1 and the frequency of COPD exacerbations (feedback, r = -0.32;p &lt; 0.05). A weak relationship was found between the relative number of eosinophils and the frequency of COPD exacerbations (direct relationship, r = 0.2; p &lt; 0.05). Weak correlations were also found between the level of HA and FEV1 (feedback, r = -0.23; p &lt; 0.05), between the level of HA and the relative number of eosinophils (direct relationship, r = 0.18; p &lt; 0.05). Conclusion. Quantitative analysis of serum HA in patients with occupational COPD can be used in clinical practice as a biochemical marker for assessing the risk of exacerbations and progression of bronchopulmonary pathology.Частота обострений хронической обструктивной болезни легких (ХОБЛ) является одним из главных факторов, определяющих исход данного заболевания. В связи с этим особую актуальность приобретает такая научно-практическая задача, как поиск биомаркеров, отражающих риск развития обострений. Целью исследования явилось изучение зависимости между концентрацией гиалуроновой кислоты (ГК) в сыворотке крови и частотой обострений ХОБЛ профессиональной этиологии (ПЭ), обусловленной воздействием кремнеземсодержащей пыли, а также обоснование применения ГК как предиктора обострений ХОБЛ. Материалы и методы. Обследованы пациенты (n = 78) с ХОБЛ ПЭ. Функция внешнего дыхания оценивалась по следующим параметрам: форсированная жизненная емкость легких (ФЖЕЛ, %долж.), объем форсированного выдоха за 1-ю секунду (ОФВ1, %долж.) и расчетное соотношение этих параметров (ОФВ1 / ФЖЕЛ, %) — модифицированный индекс Тиффно. У всех обследуемых при помощи метода твердофазного иммуноферментного анализа в сыворотке крови определялась концентрация ГК (нг / мл). Абсолютное количество эозинофилов в крови (клеток / мкл) определялось по унифицированному методу морфологического исследования форменных элементов крови с дифференциальным подсчетом лейкоцитарной формулы. Результаты. Концентрация ГК в сыворотке крови у больных ХОБЛ ПЭ с частыми обострениями была статистически значимо выше (на 25 %) такового показателя у пациентов с редкими обострениями (р = 0,004). Наиболее значимая корреляционная связь средней силы выявлена между уровнем ГК и частотой обострений ХОБЛ (прямая связь — при r = 0,32; р = &lt; 0,05), а также между ОФВ1 и частотой обострений ХОБЛ (обратная связь — при r = —0,32; р &lt; 0,05). Обнаружена слабая корреляция между относительным количеством эозинофилов в крови и частотой обострений ХОБЛ (прямая связь — при r = 0,2; р &lt; 0,05). Также установлена слабая корреляционная связь между уровнем ГК и ОФВ1 (обратная связь — при r = —0,23; р &lt; 0,05), а также между уровнем ГК и относительным количеством эозинофилов (прямая связь — при r = 0,18; р &lt; 0,05). Заключение. Определение количества ГК в сыворотке крови у пациентов с ХОБЛ ПЭ может использоваться в клинической практике в качестве биохимического маркера оценки риска обострений и прогрессирования бронхолегочной патологии

ВОЗРАСТ ГРЯЗЕВОЙ БРЕКЧИИ ГРЯЗЕВЫХ ВУЛКАНОВ АКАДЕМИЧЕСКОГО ХРЕБТА ОЗЕРА БАЙКАЛ

LakeBaikalis the only freshwater reservoir on Earth with gas-hydrate accumulations in its bottom sediments, partly due to the activity of mud volcanoes. This paper describes a group of mud volcanoes recently discovered on the slope of the Academician Ridge between the northern and central LakeBaikalbasins. Our analysis of diatom skeletons in the mud breccia sampled from the study area shows a high abundance of Cyclotella iris et var. These extinct species were also discovered in a core sample from BDP-98 borehole. Based on the biostratigraphic and seismostratigraphic correlations, the age of the mud breccia in the studied mud volcanoes ranges from the Late Miocene to the Early Pliocene (4.6 to 5.6 Ma). The correlations suggest that the material originated from a depth of less than310 m below the lake bottom.Озеро Байкал является единственным пресноводным водоемом, в донных отложениях которого обнаружены скопления газовых гидратов, часть из них связана с деятельностью грязевых вулканов. В настоящей работе представлена группа грязевых вулканов, обнаруженных с помощью съемки многолучевым эхолотом на склоне подводной возвышенности Академический хребет между средней и северной котловинами озера Байкал. Анализ скелетов диатомей в грязевой брекчии выявил в массе вымерший вид Cyclotella iris et var., который ранее был обнаружен в керне скважины BDP-98. При помощи биостратиграфической и сейсмостратиграфической корреляции было установлено, что материал, входящий в грязевую брекчию исследуемых грязевых вулканов, имеет возрастной интервал от позднего миоцена до раннего плиоцена (от 5.6 до 4.6 млн лет) и мог быть поднят с глубины не более310 м ниже дна.