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45-583: Dust is made of fine particles of solid matter . On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process ), volcanic eruptions , and pollution . Dust in homes is composed of about 20–50% dead skin cells . The rest, and in offices and other built environments , is composed of small amounts of plant pollen , human hairs , animal fur , textile fibers, paper fibers, minerals from outdoor soil, burnt meteorite particles, and many other materials which may be found in

90-509: A cuboid (when minimum bounding box is used), where the size parameter (ex. diameter of sphere) makes sense. Exception is the mathematical morphology approach , where no shape hypothesis is necessary. Definition of the particle size for an ensemble (collection) of particles presents another problem. Real systems are practically always polydisperse , which means that the particles in an ensemble have different sizes. The notion of particle size distribution reflects this polydispersity. There

135-446: A standstill, which has resulted in the abandonment of many villages as people migrate in search of water. Combination of drought and the massive irrigation proved to be a shock to the wetlands . Within five years period (1998-2002) once fertile wetlands rapidly deteriorated. We could reasonably presume that transformation of Hamoun into arid country, like their surrounding areas, was mainly caused by irrigated agriculture expansion since

180-548: A wasteland. Winds that were once cooled by the waters of the wetlands now drifting dust, sand, and salt from the dried lakebeds onto the surrounding villages, and these sand drifts have submerged nearly 100 villages beneath dunes in a landscape reminiscent of the Aral Sea disaster. Most of the crops have been reduced to dust bowl conditions, livestock herds have been decimated, and thriving fishery with an annual catch of around 12,000 tons has been wiped out. Many who had lived around

225-548: Is a common measurement technique, however this process can be more susceptible to human error and is time consuming. Technology such as dynamic image analysis (DIA) can make particle size distribution analyses much easier. This approach can be seen in instruments like Retsch Technology's CAMSIZER or the Sympatec QICPIC series of instruments. They still lack the capability of inline measurements for real time monitoring in production environments. Therefore, inline imaging devices like

270-452: Is a generic term which refers to shallow lakes (or lagoons), usually seasonal, that occur in the deserts of southeast Iran and adjacent areas of Afghanistan and Pakistan as a product of snowmelt in nearby mountains in spring. The term Hāmūn Lake (or Lake Hāmūn) equally applies to Hāmūn-e Helmand (entirely in Iran), as well to the shallow lakes Hāmūn-e Sabari and Hāmūn-e Puzak, which extend into

315-780: Is a significant source of harmful air pollution. Road dust consists of deposits of vehicle and industrial exhaust gas , particles from tire and brake wear, dust from paved roads or potholes , and dust from construction sites. Road dust is a significant contributor to the generation and release of particulates into the atmosphere. Control of road dust is a significant challenge in urban areas , and also in other locations with high levels of vehicular traffic upon unsealed roads, such as mines and landfills . Road dust may be suppressed by mechanical methods like street sweeper , vehicles equipped with vacuum cleaners , vegetable oil sprays, or with water sprayers. Calcium chloride can be used. Improvements in automotive engineering have reduced

360-462: Is a state of prevention against dust contamination or damage, by a design or treatment of materials and items in manufacturing or through a repair process . A reduced tacticity of a synthetic layer or covering can protect surfaces and release small molecules that could have remained attached. A panel, container or enclosure with seams may feature types of strengthened structural rigidity or sealant to vulnerable edges and joins . Cosmic dust

405-471: Is an international standard on presenting various characteristic particle sizes, the ISO 9276 (Representation of results of particle size analysis). This set of various average sizes includes median size , geometric mean size , average size . In the selection of specific small-size particles is common the use of ISO 565 and ISO 3310-1 to the choice of mesh size . In materials science and colloidal chemistry ,

450-408: Is dead human skin cells, but they do not live on living people. They and their feces and other allergens are major constituents of house dust, but because they are so heavy they are not suspended for long in the air. They are generally found on the floor and other surfaces until disturbed (by walking, for example). It could take between twenty minutes and two hours for dust mites to settle back out of

495-779: Is dispersed within the air in a given area, in very rare circumstances, it can cause a dust explosion . These circumstances are typically within confined spaces. Most governmental Environmental Protection Agencies, including the United States Environmental Protection Agency (EPA) mandate that facilities that generate fugitive dust, minimize or mitigate the production of dust in their operation. The most frequent dust control violations occur at new residential housing developments in urban areas. United States federal law requires that construction sites obtain planning permissions to conduct earth moving and clearing of areas, so that plans to control dust emissions while

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540-485: Is drawn down by other natural or human-induced reasons, the result is a dry lake bed in Iran. In addition, when the lake is dry, seasonal winds blow fine sands off the exposed lake bed. The sand is swirled into huge dunes that may cover a hundred or more fishing villages along the former lakeshore. Wildlife around the lake is negatively impacted and fisheries are brought to a halt. Changes in water policies and substantial rains in

585-635: Is known as Tyndall effect . 8.ISO Standard 14644-1 Classification Airborne Particles Cleanliness Hamun Lake Lake Hāmūn ( Persian : دریاچه هامون , Daryāche-ye Hāmūn ; Pashto : هامون ډنډ ), or the Hamoun Oasis , is a seasonal lake and wetlands in the endorheic Sīstān Basin in the Sistan region on the Afghanistan–Iran border . In Iran, it is also known as Hāmūn-e Helmand , Hāmūn-e Hīrmand , or Daryāche-ye Sīstān ("Lake Sīstān"). Hāmūn

630-565: Is located about 35km southwest of Dahan-e Gholaman. In 1975 the Hāmūn-e Helmand , together with Hāmūn-e Sabari , was designated a Ramsar site . In the past five millennia, people have lived around Hamoun Oasis and its wetlands and their wildlife. Specific culture formed around the Hamoun with a way of life suited to the desert wetlands. They fashioned long reed boats to navigate the shallow waters and erected squat, red clay houses to withstand

675-677: Is located in Afghanistan on the Sīstān marshes west of the Dasht-e Mārgō desert where the Helmand River forms a dendritic delta . Water flows in a circular fashion through a string of lakes starting with Hāmūn-e Puzak in the northeast, sweeping into Hāmūn-e Sabari and finally overflows into Hāmūn-e Helmand in the southwest. It used to cover an area of about 4,000 km (1,500 sq mi) with dense reed beds and tamarisk thicket fringing on

720-419: Is often a need for a certain average particle size for the ensemble of particles. The particle size of a spherical object can be unambiguously and quantitatively defined by its diameter . However, a typical material object is likely to be irregular in shape and non-spherical. The above quantitative definition of particle size cannot be applied to non-spherical particles. There are several ways of extending

765-578: Is required when removing dust to avoid causing the dust to become airborne. A feather duster tends to agitate the dust so it lands elsewhere. Certified HEPA (tested to MIL STD 282) can effectively trap 99.97% of dust at 0.3 micrometers. Not all HEPA filters can effectively stop dust; while vacuum cleaners with HEPA filters, water, or cyclones may filter more effectively than without, they may still exhaust millions of particles per cubic foot of air circulated. Central vacuum cleaners can be effective in removing dust, especially if they are exhausted directly to

810-498: Is widely present in outer space , where gas and dust clouds are the primary precursors for planetary systems . The zodiacal light , as seen in a dark night sky, is produced by sunlight reflected from particles of dust in orbit around the Sun . The tails of comets are produced by emissions of dust and ionized gas from the body of the comet. Dust also covers solid planetary bodies, and vast dust storms can occur on Mars which cover almost

855-564: The Caribbean and the Amazon basin and may affect air temperature , cause ocean cooling, and alter rainfall amounts. Dust in the Middle East has been a historic phenomenon. Recently, because of climate change and the escalating process of desertification , the problem has worsened dramatically. As a multi-factor phenomenon, there is not yet a clear consensus on the sources or potential solutions to

900-490: The Farah Province of Afghanistan. The Harut River flows into the lake on the Afghanistan side of the border. In 1976, when rivers in Afghanistan were flowing regularly, the amount of water in the lake was relatively high. Between 1999 and 2001, however, the lake all but dried up and disappeared, as can be seen in the 2001 satellite image. When droughts occur in Afghanistan, or the water in watersheds that support Lake Hāmūn

945-591: The Sīstān flatlands. Hamun Lake is sometimes categorized as three sibling shallow lakes, that is, Hamun-e Helmand, Hāmūn-e Sabari and Hāmūn-e Puzak , the latter extending into the Lash Wa Juwayn District of Farah Province in Afghanistan. Lake Hāmūn is fed primarily by water catchments on the Afghan side, including the Harut River . It is in the Sistan region and it is in the Lash Wa Juwayn District of

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990-458: The 1970s (represent as bright red patches on satellite images, mainly wheat and barley), coupled with one of the worst droughts ever witnessed in Central Asia in 1999-2001 period. The wetlands have been replaced mostly by lifeless salt flats and decaying reed stands . The wildlife, the towns, the fisheries, and the agriculture that once surrounded the Hamoun have all fallen away, giving rise to

1035-448: The Office of Desert Affairs of Iran's Natural Resources and Watershed Organization stated that according to the data of the 2018 studies, 30 million hectares of land in the country are affected by wind erosion, and 14 million hectares of this area are considered to be the focal points of wind erosion, which causes serious damage to infrastructure. Dust kicked up by vehicles traveling on roads

1080-575: The Qom salt lake and its surroundings can be mentioned, as well as the Urmia lake , which due to strong winds and due to the dryness of the lake and the reduction of its size, some areas of its bed which were underwater in the past are subject to wind erosion. In Iran, the dust directly affects more than 5 million people and has become a serious government issue recently. In the Khuzestan Province , it has led to

1125-467: The SOPAT system are most efficient. Machine learning algorithms are used to increase the performance of particle size measurement. This line of research can yield low-cost and real time particle size analysis . In all methods the size is an indirect measure, obtained by a model that transforms, in abstract way, the real particle shape into a simple and standardized shape, like a sphere (the most usual) or

1170-420: The above quantitative definition to apply to non-spherical particles. Existing definitions are based on replacing a given particle with an imaginary sphere that has one of the properties identical with the particle. In some measures the size (a length dimension in the expression) can't be obtained, only calculated as a function of another dimensions and parameters. Illustrating below by the main cases. There

1215-728: The air. Dust mites are a nesting species that prefer a dark, warm, and humid climate . They flourish in mattresses , bedding , upholstered furniture, and carpets . Their feces include enzymes that are released upon contact with a moist surface, which can happen when a person inhales, and these enzymes can kill cells within the human body . House dust mites did not become a problem until humans began to use textiles, such as western style blankets and clothing . Particle size There are several methods for measuring particle size and particle size distribution . Some of them are based on light , other on ultrasound , or electric field , or gravity , or centrifugation . The use of sieves

1260-458: The amount of PM 10 s produced by road traffic; the proportion representing re-suspension of existing particulates has increased as a result. Coal dust is responsible for the respiratory disease known as pneumoconiosis , including coal worker's pneumoconiosis disease that occurs among coal miners . The danger of coal dust resulted in environmental law regulating workplace air quality in some jurisdictions. In addition, if enough coal dust

1305-504: The basin. Farther west, revolving Afghan governments constructed large dams (Arghandab Dam, Kajaki Dam ) that diverted water from the upper reaches of the river. Precipitation variability in the Hindu Kush results in alternating periods of flooding in the Helmand and droughts, which may cause entire lagoons to dry up. This occurred several times in the 20th century when only the uppermost of

1350-605: The early solar system . Several spacecraft have sought to gather samples of dust and other materials. Among these craft was Stardust , which flew past 81P/Wild in 2004, and returned a capsule of the comet's remains to Earth. In 2010 the Japanese Hayabusa spacecraft returned samples of dust from the surface of an asteroid . House dust mites are present indoors wherever humans live. Positive tests for dust mite allergies are extremely common among people with asthma. Dust mites are microscopic arachnids whose primary food

1395-431: The edges of the upper lakes. The area was thriving with wildlife animals and migratory birds. A trapezoid-shaped basalt outcropping, known as Mount Khajeh , rises up as an island in the middle of which used to be Hāmūn Lake and the northeastern edge of Hāmūn-e Helmand . Its flat-topped peak rises up 609 meters above sea level with a diameter of 2–2.5 km (1.2–1.6 mi), being the only remaining natural uplift in

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1440-548: The entire planet. Interstellar dust is found between the stars , and high concentrations produce diffuse nebulae and reflection nebulae . Dust is widely present in the galaxy . Ambient radiation heats dust and re-emits radiation into the microwave band, which may distort the cosmic microwave background power spectrum. Dust in this regime has a complicated emission spectrum and includes both thermal dust emission and spinning dust emission. Dust samples returned from outer space have provided information about conditions of

1485-563: The global land area. These are made up of hyper-arid regions like the Sahara , which covers 0.9 billion hectares, and drylands , which occupy 5.2 billion hectares. Dust in the atmosphere is produced by saltation and abrasive sandblasting of sand-sized grains, and it is transported through the troposphere . This airborne dust is considered an aerosol , and once in the atmosphere, it can produce strong local radiative forcing . Saharan dust, in particular, can be transported and deposited as far as

1530-454: The heat of the desert. Their livelihood was based almost entirely on hunting, fishing, and farming. Until the late 20th century, irrigation waxed and waned in the Sīstān Basin for over 4,000 years without destroying the wetlands, but then population rapidly increased and new water management technologies were brought to the region. Soon irrigation schemes began to snake their way throughout

1575-612: The lakes remained flooded. Landsat satellite imagery show how dramatic decrease in precipitation resulted in decrease of snow-covered area in the Helmand Basin, from 41,000 km in 1998 to 26,000 km in 2000. By 2001, Iran and Afghanistan were experienced for the third consecutive year an extreme drought that was so severe that the Hamoun dried out completely. Sīstān 's population, swelled by refugees from war-torn Afghanistan, has been severely affected by water shortages. Irrigation channels have run dry and agriculture has come to

1620-470: The local environment. Atmospheric or wind-borne fugitive dust , also known as aeolian dust , comes from dry regions where high-speed winds can remove mostly silt-sized material, abrading susceptible surfaces. This includes areas where grazing , ploughing , vehicle use, and other human behaviors have further destabilized the land , though not all source areas have been largely affected by anthropogenic impacts . Dust-producing surfaces cover one-third of

1665-506: The outdoors. Air filters differ greatly in their effectiveness . Laser particle counters are an effective way to measure filter effectiveness; medical grade instruments can test for particles as small as 0.3 micrometers. In order to test for dust in the air, there are several options available. Pre-weighed filter and matched weight filters made from polyvinyl chloride or mixed cellulose ester are suitable for respirable dust (less than 10 micrometers in diameter). A dust resistant surface

1710-466: The problem. The dust in Iraq and Iran are migratory systems that move from west to east or east to west in the spring and have the highest intensity, concentration, and extent until mid-summer. The causes of their occurrence are the lack of humidity, dry environment, low rainfall, and annual droughts. Due to the decrease of rainfall in areas such as Iraq and Syria, most of the dust in Iran also originates from

1755-566: The region hope to effect a return of much of the water in Lake Hamoun by 2003. In 1975 the Hāmūn, together with Hāmūn-e Sabari , was designated a Ramsar site . The area has important archeological remains. The giant prehistoric city of Shahr-e Sukhteh is located in the area. Also the ruins of an ancient Achaemenid city Dahan-e Gholaman (“Gate of Slaves”) are near the Hāmūn Lake. Shahr-i-Sokhta

1800-552: The regions of Iraq, Syria, and Jordan. In addition to the foreign foci, there are areas inside the country that have either formed new dust foci in recent years or were from the past and their extent has increased. Among these areas, parts of southern Tehran , south of Alborz province - which in the past were plains, riverbeds, seasonal lakes, and seasonal reservoirs - and Gavkhoni wetland of Isfahan province can be mentioned because they have become dry and prone to dust. Among other areas that have become dust centers, Qom province ,

1845-455: The severe increase of air pollution . The amount of pollutants in the air has surpassed more than 50 times the normal level several times in a year. Recently, initiatives such as Project-Dust have been established to study dust in the Middle East directly. The continuation of drought has caused water scarcity or drying up of some wetlands and lakes such as Hamon and Urmia Lake . This has turned them into centers of dust. Director General of

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1890-401: The surface with water, vegetable oils or other dust suppressants , or by using water misters to suppress dust that is already airborne. Dust control is the suppression of solid particles with diameters less than 500   micrometers ( i.e. half a millimeter). Dust poses a health risk to children, older people, and those with respiratory diseases. House dust can become airborne easily. Care

1935-416: The term colloidal particle refers to a small amount of matter having a size typical for colloids and with a clear phase boundary. The dispersed-phase particles have a diameter between approximately 1 and 1000 nanometers . Colloids are heterogeneous in nature, invisible to the naked eye, and always move in a random zig-zag-like motion known as Brownian motion . The scattering of light by colloidal particles

1980-420: The territory of present-day Afghanistan with the latter almost entirely inside Afghanistan. The Hamun is fed by numerous seasonal water tributaries; the main tributary is the perennial Helmand River , which originates in the Hindu Kush mountains in Afghanistan. In modern times, and prior to the existence of the dams for agricultural irrigation, spring floods would bring into existence much larger lakes. It

2025-469: The work is being carried out are specified. Control measures include such simple practices as spraying construction and demolition sites with water, and preventing the tracking of dust onto adjacent roads. Some of the issues include: US federal laws require dust control on sources such as vacant lots, unpaved parking lots , and dirt roads . Dust in such places may be suppressed by mechanical methods, including paving or laying down gravel , or stabilizing

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