Suspended particles

Xem 1-16 trên 16 kết quả Suspended particles
  • Humidity is one of the main causes of decay in buildings, particularly rising damp, caused by the migration of moisture from the ground through the materials of the walls and floors via capillary action. This water comes from groundwater and surface water. The height that moisture will reach through capillary action depends upon factors such as the quantity of water in contact with the particular part of the building, surface evaporation conditions, wall thickness, building orientation and the presence of salts....

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  • After its emission or secondary formation, the length of time airborne matter will remain suspended in the air will depend upon its density, shape and size and meteorological conditions. Suspended particles are deposited by dry deposition, either by sedimentation and gravitational settling or impaction due to atmospheric turbulence and diffusion. This latter process is characteristic of particles which undergo Brownian movement and sizes below 0.1µm.

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  • Particulate pollution is a term that covers a broad spectrum of specific pollutant types that permeate the atmosphere, where sources can be both natural and anthropogenic. Within urban areas, exhaust fumes from road traffic have been the most significant source (Watkins, 1991). PM10 is commonly classified into two further size groupings: coarse and fine. The coarse fraction includes all suspended particles in the PM10 size range above 2.5m in aerodynamic diameter, whilst the fine fraction contains the remaining.

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  • As in many large cities, and especially in ones located in valleys with limited ventilation, Mexico City experiences air pollution problems, especially ozone and suspended particles. Stringent controls since 1990 have resulted in major reductions of sulfur dioxide emissions. Sulfur in diesel fuel has been reduced from 0.5% to 0.05%. Only one industrial complex still uses residual oil, and it is slated to soon change to gas. Gasoline-powered vehicles were required to have catalytic converters after 1990, and unleaded fuel was introduced at that time to provide cleaner emissions.

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  • These efforts have attenuated the emissions engendered by growth, but 24-hour PM10 (particulate matter with aerodynamic diameter less than 10 m) concentrations exceeding several hundred µg/m3 are still measured at many monitoring sites. 1,2 A persistent haze blankets the city, especially during winter, and there is great concern among residents and visitors about the effects of suspended particles on health. Aerosols that contribute to this visibility degradation are usually a combination of primary and secondary particles.

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  • A final reason to believe a connection between pollution and asthma might exist is that studies with more convincing empirical designs have found consistent effects of pollution on children’s health. Chay and Greenstone (2001) use declines in pollution that resulted from the 1980-82 recession and find a strong link between total suspended particles and infant mortality. Since most infant mortality is due to respiratory failure, it is reasonable to suspect that pollution could be related to other respiratory illnesses, such as asthma.

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  • Over 98 per cent of sprayed insecticides and 95 per cent of herbicides reach a destination other than their target species, including non-target species, air, water and soil. Pesticide drift occurs when pesticides suspended in the air as particles are carried by wind to other areas, potentially contaminating them. Pesticides are one of the causes of water pollution and some pesticides are persistent organic pollutants and contribute to soil contamination. Detection of pesticide molecules in the food items from plant and animal origin become imperative for safe consumption of food.

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  • Jones et al. Nanoscale Research Letters 2011, 6:246 http://www.nanoscalereslett.com/content/6/1/246 NANO EXPRESS Open Access Experimental study of combustion characteristics of nanoscale metal and metal oxide additives in biofuel (ethanol) Matthew Jones1, Calvin H Li1,2*, Abdollah Afjeh1, GP Peterson3 Abstract An experimental investigation of the combustion behavior of nano-aluminum (n-Al) and nano-aluminum oxide (nAl2O3) particles stably suspended in biofuel (ethanol) as a secondary energy carrier was conducted.

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  • Fang et al. Nanoscale Research Letters 2011, 6:237 http://www.nanoscalereslett.com/content/6/1/237 NANO REVIEW Open Access Measurement of the extinction coefficients of magnetic fluids Xiaopeng Fang, Yimin Xuan*, Qiang Li Abstract A novel spectral transmittance approach for measuring the extinction coefficient of magnetic fluids is proposed. The measuring principle and accuracy of the approach are analysed. Experiments are conducted to measure the extinction coefficient of magnetic fluids with different particle volume fractions.

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  • The removal of suspended matter from water is one of the major goals of water treatment. Only disinfection is used more often or considered more important. In fact, effective clarification is really necessary for completely reliable disinfection because microorganisms are shielded by particles in the water. Clarification usually involves: • coagulation • flocculation • settling • filtration This guide focuses on coagulation and flocculation: the two key steps which often determine finished water quality....

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  • Airborne suspended particulate matter can be of primary origin, i.e. emitted directly into the atmosphere or of secondary origin, i.e. formed in the atmosphere from gaseous species by either homogeneous or heterogeneous chemical reactions. Due to these different emission sources, particles have different chemical composition and size distributions. Depending on their size, particles have a different potential to be transported over either long or short distances [1]. Primary particles can be produced from either natural or anthropogenic sources.

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  • Airborne suspended particulate matter (PM) can be either primary or secondary in nature. Primary particles are emitted directly into the atmosphere either by natural or anthropogenic processes, whereas secondary particles have a predominantly man made origin and are formed in the atmosphere from the oxidation and subsequent reactions of sulphur dioxide, nitrogen oxides and VOCs.

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  • The infectiousness of a TB patient is directly related to the number of droplet nuclei carrying M. tuberculosis (tubercle bacilli) that are expelled into the air. Depending on the environment, these tiny particles can remain suspended in the air for several hours. M. tuberculosis is transmitted through the air, not by surface contact. Infection occurs when a person inhales droplet nuclei containing M. tuberculosis, and the droplet nuclei traverse the mouth or nasal passages, upper respiratory tract, and bronchi to reach the alveoli of the lungs.

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  • Breaking waves on the sea cause the ejection of many tiny droplets of seawater into the atmosphere. These droplets dry by evaporation leaving sea salt particles suspended in the air. Particles are also directly emitted by the bursting of air bubbles on sea surface Such particles are generally in the size range between 1 to 20µm. [19]. Whilst these particles are, in the main, rather coarse in size, a minor part of their mass is in particles small enough to have an appreciable atmospheric lifetime, which has been estimated as three days [20].

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  • Some particles may be absorbed into the tree but most are retained on the plant surface. Some particles will be re-suspended, but others will be washed off (particularly soluble particulates) or fall with leaves or twig fall. This may lead to pollution within the soil, however, Beckett et al. (2000a) argues that this will only be a major problem in countries using a high proportion of lead fuel. Re-suspension of fine particulates is less likely as they are easier embedded1 within the leaf boundary layer (Beckett et al., 2000b).

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  • M. tuberculosis is carried in airborne particles, called droplet nuclei, of 1–5 microns in diameter. Infectious droplet nuclei are generated when persons who have pulmonary or laryngeal TB disease cough, sneeze, shout, or sing. Depending on the environment, these tiny particles can remain suspended in the air for several hours. M. tuberculosis is transmitted through the air, not by surface contact. Transmission occurs when a person inhales droplet nuclei containing M.

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