Environmental Chemistry Letters - Plants remove efficiently atmospheric pollution by soot particles, yet the mechanisms used by leaves to capture soot particles are unclear. Here, we studied the... 相似文献
Dust and Sand Storms (DSS) originating in deserts in arid and semi-arid regions are events raising global public concern. An important component of atmospheric aerosols, dust aerosols play a key role in climatic and environmental changes at the regional and the global scale. Deserts and semi-deserts are the main source of dust and sand, but regions that undergo vegetation deterioration and desertification due to climate change and human activities also contribute significantly to DSS. Dust aerosols are mainly composed of dust particles with an average diameter of 2 mm, which can be transported over thousands of kilometers. Dust aerosols influence the radiation budget of the earthatmosphere system by scattering solar short-wave radiation and absorbing surface long-wave radiation. They can also change albedo and rainfall patterns because they can act as cloud condensation nuclei (CCN) or ice nuclei (IN). Dust deposition is an important source of both marine nutrients and contaminants. Dust aerosols that enter marine ecosystems after long-distance transport influence phytoplankton biomass in the oceans, and thus global climate by altering the amount of CO2 absorbed by phytoplankton. In addition, the carbonates carried by dust aerosols are an important source of carbon for the alkaline carbon pool, which can buffer atmospheric acidity and increase the alkalinity of seawater. DSS have both positive and negative impacts on human society: they can exert adverse impacts on human’s living environment, but can also contribute to the mitigation of global warming and the reduction of atmospheric acidity.
The atmospheric chemical composition is affected by the interaction mechanisms among gases and particulate matter through
a wide range of chemical reactions that can occur with the aid of particulate matter (e.g. particles act as reacting or absorbing
surfaces) or be influenced by the presence of particulate matter in the atmosphere (photochemical reactions). Physical and
chemical processes are also bonded in an interactive way that often leads to the influence of the radiation budget, cloud
physics and the warming or cooling of the lower atmospheric levels. The Euro-Mediterranean region is a key-sensitive area
due to the unique climatic and air quality characteristics associated with the regional climatic patterns, geomorphology (land
and water contrast) and coexistence of pollutants from different origin. Focusing on this region, the gas-aerosol interactions
are studied using state-of-the-art atmospheric and chemical transport modeling tools following the necessary development in
the chemical transport model CAMx. Sensitivity and large-scale simulations have shown significant responses of the modeling
system to the inclusion of natural species emissions, the direct shading effect of dust particles on photochemical processes
and the formation of new types of aerosols through heterogeneous uptake of gases on dust particles. Including such interactions
in the chemical transport model often led to the improvement of the model performance compared with available measurements
in the region. 相似文献
Atmospheric particulate matter is altering climate. For instance marine biogenic particles are cooling climate. Organic markers are major tools to elucidate the sources of atmospheric particulate matter. Formate is commonly used as a marker of continental aerosols, whereas methanesulphonate is used as tracer of biogenic marine aerosols. However, transformation processes during aerosol transport may modify their relative concentrations and, in turn, introduce a bias in the assessment of particle sources. Actually very little is known about the transformation of formate and methanesulphonate in aerosols. Therefore, we irradiated formate and methanesulphonate in the presence of nitrate and haematite. Nitrate and haematite are aerosol photosensitisers, producing reactive species that degrade organic compounds. The time evolution of formate and methanesulphonate was monitored by ion chromatography. Our results show that formate is transformed from 1.6 to 4.1 times faster than methanesulphonate. This trend is partly due to higher reactivity with the hydroxyl radical and partly due to additional reaction with other transients such as nitrogen dioxide. Such results strongly suggest faster formate transformation during particle transport. Therefore, when formate and methanesulphonate are used as particle tracers, an overestimation of marine biogenic versus continental particle sources is expected. This bias has major implications for climate prediction models, because marine biogenic particles have a cooling effect on climate. 相似文献
A mechanism of formation of small-scale inhomogeneities in spatial distributions of aerosols and droplets associated with
clustering instability in the atmospheric turbulent flow is discussed. The particle clustering is a consequence of a spontaneous
breakdown of their homogeneous space distribution due to the clustering instability, and is caused by a combined effect of
the particle inertia and a finite correlation time of the turbulent velocity field. In this paper a theoretical approach proposed
in Elperin et al. (2002) Phys Rev E 66:036302 is further developed and applied to investigate the mechanisms of formation
of small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The theory of the particle clustering instability
is extended to the case when the particle Stokes time is larger than the Kolmogorov time scale, but is much smaller than the
correlation time at the integral scale of turbulence. We determined the criterion of the clustering instability for the Stokes
number larger than 1. We discussed applications of the analyzed effects to the dynamics of aerosols and droplets in the atmospheric
turbulent flow. 相似文献
Bags of S. auriculatum and a low‐volume aerosol sampler with filters were exposed, in parallel, to the urban atmosphere of Oporto at four sampling points and for about two months periods, between 1991 and 1994. The levels of lead in the moss (weekly samples) and in the filters (daily samples) were determined by atomic absorption spectrophotometry and the results were compared. In dry weather periods (relative humidity ≤ 76%) the rate of lead uptake by moss was approximately constant and proportional to the levels of the metal in atmospheric aerosols. A converting factor (CF = lPbmoss l (μg/g.day)/ l Pbair l (μg/m3)) allowed conversion of the lead levels in S. auriculatum to those in the atmospheric aerosols. Because the moss fixed lead from gas, aerosol and particulated matter, the rate of sorption depends markedly on the distance to the lead sources (traffic) and on surrounding obstacles which retain particles. Therefore, specific calibration by mechanic monitoring at each point of sampling is required when moss bag samplers are used to provide quantitative information about lead levels in the atmosphere. In wet weather periods, higher but irregular rate of lead uptake was observed. In contrast, the lead levels in atmospheric aerosols decreased when the humidity increased due to wet deposition. Therefore, no proportionality between the lead levels in the moss and in the air were found. 相似文献
