Global Lagrangian Atmospheric Dispersion Model

The Global Lagrangian Atmospheric Dispersion Model (GLADIM) is described. GLADIM is based on the global trajectory model, which had been developed earlier and uses fields of weather parameters from different atmospheric reanalysis centers for calculations of trajectories of air mass that include trace gases. GLADIM includes the parameterization of turbulent diffusion and allows the forward calculation of concentrations of atmospheric tracers at nodes of a global regular grid when a source is specified. Thus, GLADIM can be used for the forward simulation of pollutant propagation (volcanic ash, radionuclides, and so on). Working in the reverse direction, GLADIM allows the detection of remote sources that mainly contribute to the tracer concentration at an observation point. This property of Lagrangian models is widely used for data analysis and the reverse modeling of emission sources of a pollutant specified. In this work we describe the model and some results of its validation through a comparison with results of a similar model and observation data.     

A Lagrangian biogeochemical study of an eddy in the Northeast Atlantic

We report the results of an experiment in the Northeast Atlantic in which sulphur hexafluoride (SF₆) was released within an eddy and the behaviour of trace gases, nutrients and productivity followed within a Lagrangian framework over a period of 24 days. Measurements were also made in the air above the eddy in order to estimate air-sea exchange rates for some components. The physical, biological and biogeochemical properties of the eddy resemble those of other eddies studied in this area, suggesting that the results we report may be applicable beyond the specific eddy studied. During a period of low wind speed at the start of the experiment, we are able to quantitatively describe and balance the nutrient and carbon budgets for the eddy. We also report concentrations of various trace gases in the region which are similar to those observed in other studies and we estimate exchange rates for several trace gases. We show that the importance of gas exchange over other loss terms varies with time and also varies for the different gases. We show that the various trace gases considered (CO₂, dimethyl sulphide (DMS), N₂O, CH₄, non-methane-hydrocarbons, methyl bromide, methyl iodide and volatile selenium species) are all influenced by physical and biological processes, but the overall distribution and temporal variability of individual gases are different to one another. A storm disrupted the stratification in the eddy during the experiment, resulting in enhanced nutrient supply to surface waters, enhanced gas exchange rates and a change in plankton community, which we quantify, although overall productivity was little changed. Emphasis is placed on the regularity of storms in the temperate ocean and the importance of these stochastic processes in such systems.     

Modeling the convective cloudiness and its impact on the atmospheric gaseous composition

A combined three-dimensional numerical model of convective cloudiness with detailed microphysics and a model of the transport of atmospheric trace gases with gas- and aqueous-phase chemistry were developed. We consider the main physical mechanisms responsible for the formation of midsized droplet clouds and the transport of gases with differing solubility therein. Test numerical calculations were performed to investigate the sensitivity of the cloud model to variations in input parameters, as well as the variability of the ion composition of cloud drops with regard to their size distribution. The results of numerical calculations are presented with a preliminary analysis.     

Dynamics of trace gases and aerosols in the atmosphere with consideration for heterogeneous processes

A combined mathematical model has been developed to reproduce space and time variations in the concentrations of multicomponent gas constituents and aerosols in the atmosphere on both regional and urban scales. This model contains blocks of transport of gas constituents and aerosols in the atmosphere with consideration for homogeneous binary nucleation, the kinetic processes of condensation/evaporation and coagulation, chemical processes occurring in both gas and liquid phases, and the processes of mass exchange during the gas-droplet (particle) interaction. A nonhydrostatic model of atmospheric mesoscale processes is used to calculate the fields of meteorological elements and turbulent characteristics. The generation of new-phase particles from precursor gases by the mechanism of homogeneous binary nucleation and their interaction with background aerosol are considered. The results of numerical experiments are compared with the data obtained from field observations of both space and time variations in the concentrations of gas constituents and aerosols and in the ionic content of aerosol particles over the Baikal region under the influence of emissions from powerful industrial sources.     

Dynamics of surface-air pollution during the passage of a cold front

The dynamics of meteorological parameters, of sodar data on the temperature stratification of the atmospheric boundary layer, and of surface contents of pollutants (nitrogen oxides, carbon monoxide, and ozone) during the passage over Moscow of a structurally complex prominent cold front are discussed. It is shown that the cold front passage is accompanied by stepwise increases in the NO, NO₂, and CO surface contents. A probable cause of this phenomenon is a quick entrainment of smoke plumes from high-altitude sources of pollution into the surface turbulent air near the frontal boundary. Intense advection of cold air at the rear of the cyclone can lead to the development of an unstable stratification in the atmospheric boundary layer even in the nighttime. Under these conditions, the minute-scale variability of contents of trace gases increases abruptly as compared to that occurring in the frontal zone of the cyclone prior to the passage of the front. This effect is statistically significant. The dynamics of surface ozone reflects an increase in its background concentrations in arctic air masses.     

Methane, carbon monoxide, and carbon dioxide concentrations measured in the atmospheric surface layer over continental Russia in the TROICA experiments

The principal statistical regularities typical of the behaviors of the CH₄, CO, and CO₂ concentrations in the atmospheric surface layer over the continental Russian territory are revealed from the measurements performed in 1997–2004 along the Trans-Siberian Railroad from Moscow to Khabarovsk with a mobile laboratory. The data obtained under the conditions of the atmosphere free of anthropogenic pollutants are analyzed. For near-background conditions, the typical continental methane, carbon monoxide, and carbon dioxide concentrations and characteristic features of their large-scale spatial distributions and daily variations, including those caused by surface inversions, are determined. Variations in the concentrations of these trace gases over industrial regions are analyzed. Our results are compared to the data obtained at background stations of the world network of atmospheric monitoring and to the data of a numerical simulation.     

Temporal variations in carbon dioxide and methane concentrations under urban conditions

Temporal variations in the surface concentrations of two greenhouse gases (carbon dioxide and methane) in the atmosphere over a large city are studied on the basis of the data obtained during the 2003–2005 observations at a Moscow station for environmental monitoring. This station is based on the TROICA mobile observatory and located at the meteorological station of the Faculty of Geography, Moscow State University, on Vorob’evy gory. The methods of isolating the background concentrations of greenhouse gases under urban conditions are proposed, and the excess concentrations of CO₂ and CH₄ over their background values are estimated for different seasons and times of day. The CO₂ and CH₄ concentrations are shown to have more pronounced diurnal cycles in summer than in winter. The main causes of temporal variations in the surface concentrations of CO₂ and CH₄ under urban conditions and the differences between the mean concentrations of these greenhouse gases in Moscow and other areas of Russia are analyzed. It is shown that variations in the surface concentrations of carbon dioxide and methane on different time scales are caused by different atmospheric processes (global circulation, mesoscale gravity waves, surface temperature inversions, etc.)     

Photochemical models of the atmosphere and their application in ozonosphere and climate studies: A review

This review is devoted to problems in the photochemical modeling of atmospheric processes. The physicochemical and mathematical foundations underlying the construction of photochemical models are described, a classification of the atmospheric reactions is presented, and the features of photochemical modeling are considered under various irradiance conditions for various atmospheric layers and geographical regions. Atmospheric processes that are important to photochemical models are discussed. Applications involving photochemical models are outlined. Some results are presented to illustrate the capabilities of photochemical models. Special attention is given to relatively recent directions in photochemical modeling, such as data assimilation and inverse problems. The review can be used by experts in areas related to atmospheric chemistry as a basic source of knowledge on the subject and for the development of photochemical modules for atmospheric models.     

Simulation of additive transport from the land surface on the basis of experimental data on heat transfer in the atmospheric surface layer

A method is proposed to study the transport of a passive additive in the atmospheric surface layer with the use of the atmospheric transfer function. This method makes it possible to estimate the spatial distribution of the concentration of a passive additive in the atmospheric surface layer from the additive’s surface source without experimentally determining the vertical profile of the transport coefficient or without resorting to various hypotheses for the character of its behavior. The transfer function, which contains the information on the wind-field structure, can be obtained from simple one-point measurements of surface-and air-temperature fluctuations and from subsequent spectral processing of the data. The effects of the wind-velocity profile and turbulence on the spatial distribution of additive concentration are assessed. This method allows one to simplify experiments during development and verification of the models of atmospheric diffusion. This method may also be useful in emergency situations to predict the propagation of hazardous additives.     

Bursting bubbles and their effect on the sea-to-air transport of Fe, Cu and Zn

The effects of the bubble breaking process on the atmospheric geochemical cycles of the elements Fe, Cu and Zn were investigated, in situ, in the estuarine waters of Narragansett Bay, Rhode Island. Enrichment, as defined by the metal-to-sodium ratios in the aerosols produced compared to their ratio in bulk water, occurred for the three metals investigated. The extent and potential geochemical importance of the process were different for each element. Iron enrichment was quite low (enrichment factor (EF) <100) and constant, and scavenging of iron from the water column and subsequent enrichment on the aerosols produced did not appear to occur. Copper enrichment on the aerosols was 200 and appeared to be influenced by both microlayer and scavenging effects. In addition, copper enrichment appears to be correlated to biological processes. Zinc enrichment was approximately the same as Cu; however, a strong scavening effect appeared to occur, suggesting scavenging of Zn by rising bubbles. Scavenging effects suggest that open-ocean enrichments for Cu may be slightly higher than observed here and a great deal higher for Zn.Geochemical implications of the data, together with other existing data, indicate that the sea is an insignificant source of Fe to the atmosphere. The sea may be a significant source (contributing on the order of 10% or more) of the total annual quantity of Cu and Zn to the atmosphere.     

Atmospheric inputs of trace metals to the northeast Atlantic Ocean: the importance of southeasterly flow

The study of aerosols and rainwater presented here demonstrates that episodic atmospheric deposition events associated with southeasterly flow are quantitatively significant for large areas of the North Atlantic Ocean. This paper considers aluminium and manganese, with predominantly crustal sources, and lead and zinc, which are mobilised into the atmosphere primarily through anthropogenic activity. High levels of all trace metals are associated with southeasterly flow from Europe as the air passes over heavily populated and industrialised regions before reaching the northeast Atlantic Ocean. Fluxes calculated using the 1% HNO₃ acid soluble metal concentration show that, although the climatological norm for this area is westerly flow, short-lived southeasterly transport events dominate the input of trace metals to this ocean region. This material may be toxic to phytoplankton or may be represent a new source of nutrients to the biological community. A significant decrease in atmospheric lead levels in polluted air is seen between June 1996 and May 1997, reflecting the decrease in use of leaded fuels in Europe. Comparing atmospheric flux values to sediment trap metal fluxes shows that the atmosphere represents the dominant source of zinc to the deep ocean, whereas an additional, non-atmospheric, manganese source this required, perhaps from mobilisation of sedimentary material from the continental shelf or long range advection of manganese rich Saharan material.     

Adsorption–desorption reactions and bioturbation transport of Ra in marine sediments: a one-dimensional model with applications

The distribution of trace metals in sediments and their exchange between sediments and overlying water is governed by multiple processes including molecular diffusion, bioturbation (porewater advection, porewater mixing, and particle mixing), chemical reactions and adsorption–desorption. To understand these processes and their relative contributions, a one-dimensional model was built, which includes bioturbation and adsorption–desorption processes, to describe the transport of ²²⁴Ra. Because ²²⁴Ra is adsorbed on MnO₂, ²²⁴Ra may serve as a proxy for trace metal transport. Three sites were sampled and both dissolved and adsorbed ²²⁴Ra were analyzed and modeled to understand the transport and exchange processes. It was found that particle transport of adsorbed ²²⁴Ra followed by desorption at the sediment/water interface typically represents the dominant flux. We have further been able to define conditions where the porewater transport for adsorption reactive metals like ²²⁴Ra (and other metals) may be out of the sediments whereas the active scavenging of ²²⁴Ra from the water column at the sediment water interface via adsorption reactions can result in a flux of ²²⁴Ra into the sediment. These processes are both predicted by the model and observed in sediment samples.     

Adsorption–desorption reactions and bioturbation transport of 224Ra in marine sediments: a one-dimensional model with applications

The distribution of trace metals in sediments and their exchange between sediments and overlying water is governed by multiple processes including molecular diffusion, bioturbation (porewater advection, porewater mixing, and particle mixing), chemical reactions and adsorption–desorption. To understand these processes and their relative contributions, a one-dimensional model was built, which includes bioturbation and adsorption–desorption processes, to describe the transport of ²²⁴Ra. Because ²²⁴Ra is adsorbed on MnO₂, ²²⁴Ra may serve as a proxy for trace metal transport. Three sites were sampled and both dissolved and adsorbed ²²⁴Ra were analyzed and modeled to understand the transport and exchange processes. It was found that particle transport of adsorbed ²²⁴Ra followed by desorption at the sediment/water interface typically represents the dominant flux. We have further been able to define conditions where the porewater transport for adsorption reactive metals like ²²⁴Ra (and other metals) may be out of the sediments whereas the active scavenging of ²²⁴Ra from the water column at the sediment water interface via adsorption reactions can result in a flux of ²²⁴Ra into the sediment. These processes are both predicted by the model and observed in sediment samples.     

Geochemical signature as paleoenvironmental markers in Holocene sediments of the Tinto River estuary (Southwestern Spain)

High absolute concentrations of metals associated to sulfide deposits located at the river source (Fe, Cu, Zn, Pb, Cd, and As) have been determined from the study of major and trace element concentrations in sediment samples obtained in two vibracores in the Tinto River estuary. In most cases, the enrichment factor (EF) for these metals is over 2. Cu, Zn and As have much higher EF, over 10 in surficial samples. Fe oxy-hydroxide precipitation in high-chlorinity zones and its scavenging effect on metals is the main control process on the chemical composition of sediment. Vertical evolution of the sedimentary and geochemical characteristics of the cores show that the estuary has undergone a process of progressive shallowness and a relative increase in acidic river water volume with respect to seawater. This effect has originated a downstream displacement of acid mixing processes affecting the estuary, which is reflected in higher metal concentrations in sediments of the outer zones of the system.     

Simulation of the indirect impact that the 11-year solar cycle has on the gas composition of the atmosphere

An interactive three-dimensional chemistry-climate model combining models of the gas composition and general circulation of the lower and middle atmosphere is used to study the impact of changes in extra-atmospheric solar radiative fluxes induced by solar activity on the stratospheric heating and subsequent temperature and ozone variations in the stratosphere and troposphere. The results have shown that a change in the atmospheric radiative heating resulting from variations in solar activity has a direct effect on the temperature and circulation of the atmosphere. Atmospheric temperature variations affect the rates of temperature-dependent chemical reactions, and this is considered the first type of indirect impact of solar activity on the atmospheric gas composition. On the other hand, as a result of the variation in atmospheric heating, its circulation changes, thus affecting the transport of minor gases into the atmosphere. This effect is considered the second type of indirect impact of solar activity on atmospheric gases. The results of our calculations have shown that both types of indirect impact of the variation in solar activity on the atmospheric gas composition are comparable in order of magnitude to the direct impact of solar activity on atmospheric gases.     

稳定同位素方法在海洋N_2O研究中应用展望

氧化亚氮(N2O)是大气中重要和微量的温室气体,且在平流层N2O形成NO自由基与O3发生反应破坏臭氧层.海洋是大气中N2O净源,但由于海洋中生物化学过程的复杂性,有关N2O形成机制至今是人们研究的重点和难点.应用稳定同位素分馏原理对海洋中N2O形成机制的研究,区分海洋中通过硝化和反硝化过程不同途径产生的N2O过程,为深入研究海洋中N2O循环、估算将来大气中N2O浓度变化提供有用工具.     

Rain water-aerosol trace metal relationships at cap ferrat: A coastal site in the Western Mediterranean

The factors controlling the distributions of the trace metals Al, Co, Ni, Cu and Pb in a series of 25 individual rain water samples collected at Cap Ferrat, a site on the Western Mediterranean coast, are interpreted in relation to aerosols taken simultaneously at the same site. The trace metal chemistry and pH of the rain waters are constrained by the scavenged aerosols, which are composed of a mixture of urban-dominated (European) and crust-dominated (Saharan) components. Thus, the pH values of the rain waters, which range between 3.95 to 6.77, reflect the type of aerosol scavenged from the air; urban-dominated aerosol components giving rise to acidic rains, and crust-dominated aerosol resulting in neutral to basic rains. The average solubilities of the trace metals in the rain waters increase in the order Al (17%), Co (36%), Ni (53%), Pb (65%) and Cu (76%). The paniculate ↔ dissolved speciation of the non-crust-dominated metals Cu and Pb varies with pH, being more soluble at lower pH values, and exhibits the classical pH ‘adsorption edge’. However, the pH of rain can vary during an individual rain event in response to the sequential scavenging of crust-dominated and urban-dominated aerosol components. As a result, the solubility of non-crust-dominated trace metals, such as Pb, can also vary sequentially during an individual rain event; the maximum solubility being related to a ‘dip’ in pH associated with the scavenging of urban-rich aerosol components, followed by a return to the initial pH as the pH-influencing components are exhausted. Data from the present study therefore indicate that the pH-controlled trace metal solubility relationship reported for individual rain events can also occur sequentially in the same event. The particulate material in the rain waters does not contain the relatively high concentrations of Ni, Cu and Pb found in the parent aerosols, and its composition approaches that of crust-dominated aerosols transported to the Mediterranean. Data from the present study, together with those for other Western European coastal locations, indicate that there is a Pb-Cu fractionation between aerosols and rainwaters which results in a significantly greater fraction of the aerosol Pb, relative to Cu, escaping precipitation scavenging in the coastal zone and so becoming available for long-range atmospheric transport.     

Variability of trace gases in the atmospheric surface layer from observations in the city of Moscow

The results of continuous minute measurements of the surface concentrations of ozone, nitric oxide, nitrogen dioxide, carbon monoxide, and sulfur dioxide during the 2002–2004 period at the environmental station of the Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP), and the Faculty of Geography, Moscow State University (MSU), are discussed. It is shown that the conditions of Moscow’s southwestern region remote from large local pollution sources reflect the general regularities of the variability of trace gases in an urban atmosphere. This is manifested in the mean annual value of the ratio NO/NO₂ (a little less than 1), decreased daylight values of O₃, increased values of the rest of the trace gases as compared to the background region, and the presence of a secondary nocturnal maximum in the diurnal cycle of O₃. The features of the annual and diurnal cycles of the concentrations of the substances under analysis are discussed. In the diurnal cycle of the primary products of combustion (NO and CO), an excess of the morning maximum (over the evening one) is observed during both warm and transition periods and higher values of the night maximum (as compared to the daylight one) are noted for summer. The temperature stratification properties determined from the MSU long-term acoustic sounding data serve as a possible cause for both of the effects revealed. The annual cycle of the concentration of surface ozone is characterized by the highest values for spring and summer. The annual cycles of NO, NO₂, CO, and SO₂ do not demonstrate any obvious seasonal regularities. A significant seasonal variation of the ratio NO/NO₂, which is associated with the oxidizing properties of the urban atmosphere, is revealed. The record high concentrations of trace gases in the atmosphere over Moscow are given, and the meteorological conditions for their accumulation are discussed.     

DMS and its oxidation products in the remote marine atmosphere: implications for climate and atmospheric chemistry

DMS emitted into the atmosphere over the global oceans has a range of effects upon atmospheric composition (mediated through various oxidation products) that may be significant with regard to issues as important as climate regulation, and the trace gas oxidation capacity of the marine atmospheric boundary layer. The roles played by DMS oxidation products within these contexts are diverse and complex, and in many instances are not well understood. Here we summarize what is known, and suspected, about the couplings between the marine atmospheric sulfur cycle, other atmospheric chemical cycles, and the dynamics and microphysics of the marine atmospheric boundary layer. This overview focuses heavily on measurements carried out in clean Southern Ocean air masses in association with the Australian Baseline Air Pollution Station located at Cape Grim (40° 40′ 56″S, 144° 41′ 18″ E), Tasmania. The data confirm that in the remote marine atmosphere, DMS is a central player in a variety of important atmospheric processes, reinforcing the need to understand quantitatively the factors that regulate DMS emissions from the ocean to the atmosphere.     

Alternative interpretations as to the origin of the hydrocarbons of the Guajira Basin,Colombia

The origins of the hydrocarbon gases recovered from the Chuchupa, Ballena, and Riohacha fields, located in the Guajira basin, northeast Colombia, are examined. These gases are composed of methane with trace amounts of wet gas components (C₂₊<0.5%). The methane is isotopically light (δ¹³C₁<−50‰), as are the other hydrocarbon components. The Ballena and Riohacha fields are considered to have a biogenic origin and the Chuchupa gas is thought to have a mixed biogenic-thermogenic origin. The presence of a thermogenic contribution at Chuchupa need not, however, indicate that the sedimentary sequence was exposed to elevated temperatures. The generative kitchen located to the northwest of the three gas fields would preferentially feed into the Chuchupa Field.The gases recovered at three onshore seep localities appear to include a thermogenic component. As a result of fractionation it is unclear whether they represent ‘pure’ thermogenic gases or a mixed thermogenic-biogenic origin similar to Chuchupa.An examination of oil microseepage observed in soil samples recovered from the onshore Guajira region point to another hydrocarbon system apparently not related to the three gas fields. Some of these microseeps include ‘fresh’ (nonbiodegraded) oils. These microseeps did not correlate with either of the Tertiary oil families from the Sinú Urabá basin located to the southwest of the study area or with Cretaceous oils from that basin. A better correlation was observed with the La Luna Formation, but significant differences remain implying that the source for the microseeps was less calcareous and deposited in a less restricted environment than associated with ‘classical’ La Luna facies. This could indicate either a facies change or that a different source unit is present within the region.