جستجوی مقالات مرتبط با کلیدواژه "ریزگردها" در نشریات گروه "محیط زیست"

Dust phenomenon happens due to various reasons such as human intervention in overuse of surface and groundwater resources, vegetation degradation, improper dams and soil weakening due to agricultural processes and some natural factors such as drought and climate change. The main aim of this research is codification of effective environmental law to combat dust storm.  The present research is descriptive and analytical and applied studies. The method of this research is qualitative and based on documentary and library studies and data collection from valid scientific sites. The results of studies show that this phenomenon, in addition to disrupting the normal life of people, is a serious threat to the environment and leads to the reaction of public opinion. Recent drought, lack of international diplomacy and attention to laws and regulations are among the factors affecting the dust phenomenon. From the principles extracted based on the studies, we can mention the principle of creating environmental security, the principle of sustainable development in international law, the principle of necessity of environmental protection, the precautionary principle, the principle of prevention, the principle of information and the principle of non-harmful use of land.

For more than a decade, the southwestern provinces of Iran have encountered with the phenomenon of sand and dust storms. This phenomenon has become the most common cause of air and environmental pollution in those areas. The present research aims to examine the challenges and risks posed by this phenomenon against sustainable development.

This research has investigated the social, political and economic dimensions of the dust problem using a qualitative method (thematic analysis). The techniques used were semi-structured interviews and observations. In this study, 60 local people were interviewed.

The findings show that dust particles not only have caused the loss of biological balance of plant species in the environment, but also they have had devastating effects on the local businesses and have caused socio-psychological and health problems and increased the cost of life for the people and the government. The phenomenon of dust can be considered as the most important factor that has reduced the objective and subjective quality of life of locals.

This research shows that this phenomenon has created an undesirable collection of issues in the economic, social and health fields that reproduces a polysemantic structure of poverty. In such undesirable environment, dissatisfaction with the current situation has paved the way for the collapse of the balance of the social system of the society. This kind of climate change has had a great impact on the quality of life of the people, which, on the one hand, provides a platform for distrust to the involved institutions and, on the other hand, threatens the sustainability of development in the social, economic and political dimensions.

The right to enjoy a healthy weather is one of the aspects of enjoying a clean and stable environment which is both individual and collective in nature. According to this right, every human being should have access to adequate clean water and breathe healthy and clean air. This right is directly related to human beings’ physical and mental well being and without it our life would face very serious dangers. Local, national and international documents of human rights support the right of enjoying a healthy weather. This article uses the Islamic point of view on enjoying a healthy weather, tries to apply this subject to Khuzestan dusty weather and its effects on basic human rights like, the right to be healthy. The right to have education and children and the right of seniors are discussed and some guidelines are introduced to avoid deprivation of these rights. This article consists of three parts. The first part discusses the right to enjoy healthy weather in international human rights and environmental documents. In the second part we discuss the importance of weather in Islamic teachings and environmental laws of Iran and in the last part we apply the right of enjoying healthy weather to Khuzestan weather condition.

One of the natural phenomena that cause disastrous damages every year especially in arid and desert regions of the world is sandy storms. About two third of Iran is located in arid and semi arid regions. Studies show that 14 provinces in Iran are affected by wind erosion. The province of Sistan and Baluchistan has more than 5 million hectares of desert area, which its 800000 hectares (about 16 percent of the mentioned area) are among active dust areas. Dust is one of the unfavorable climatic and environmental phenomena, which is getting far away from its regular cycle in recent years and happens frequently in the Sistan area. Existing dust particles in the air are a group of solid or liquid particles whose size is between 0/002 and 500 micron. One of most important causes of this phenomenon is the lack of suitable vegetation. Green belt acts as a complete cover surrounding the city and it will help avoiding the entrance of pollution and dust into cities. In recent years, dust pollution happens frequently in Zahedan city. In fact, as Zahedan has a dominantly arid climate, it wont be a new event but the extensive amount of dust entering the city through every wind has made living more difficult. The direction of most winds blowing toward Zahedan is usually south-west and north-east and they usually carry dust particles with them. The location of the two studied areas which are at the entrance of Zahedan-Khash road( Khalij Fars boulevard),the importance of considering visual beauty at the entrance of the city( the lack of sufficient vegetation at the moment effects its visual beauty),being in neighbor with populous places like universities such as medical science university, Quran sciences university and Payam Noor university and also being in neighbor with some important organizations are the most important reasons which make this area the most qualified for pre-required necessities for applying a precise investigation.
This study was fulfilled to present procedures to decrease dust level in Zahedan city and to bring air quality close to a range of 0-54 mg/m^3. In this study, existing 〖PM〗_10 particles in the air was measured. After defining air density index, air quality index (AQI) was determined by the use of T-test. Then the required width and length of green belt in order to lessen dust level up to clean air standards where determined.

The applied method in this study is a descriptive- analytical method. Its objectives are as following:• To study the effect of mixed planting on the reduction of existing dust particle in the air in comparison to the existing vegetation.
• Determining the required width and length for the green belt in order to lessen dust level up to clean air standards(A: By using the statistical tests B: By considering city’s population)
• Selecting suitable plant species to be planted in green belt and recreational places considering the regions climate.
This research was fulfilled from April 2015 to March 2016 in order to study the density of the existing dust particles in air in two studied areas in Zahedan city. The first studied region consists of one hectare area in the southwestern part of Zahedan. This region has the poorest vegetation with limited number of Pine and Eucalyptus trees. The Distribution of trees and the dominant planting method especially in southwestern part is the same as the existing planting method in the first studied area. The second studied area has the exact area of the first region (approximately about 1 hectare) which is not located far from the first region. The second region is also located in the southwestern part of the city. This mentioned region dominantly has more different species in comparison to the first region which the total tree number is more than the first region.
The density of dust particles in the air was measured by using Grimm sample gathering – analyzing device in regular intervals with predefined periods (annual basis) for both studied areas. Samples gathered in order to evaluate the density of the existing dust particles in the air for both regions was performed once in every five minutes. But the data applied every three days based on the instructions of the U.S environment organization.

To measure the effects of mixed planting (in the second studied area) on reducing the volume of the existing dust particles in the air in comparison to the existing planting in the first studied area based on T-test, the following results are achieved: To determine the length and width of the green belt in order to reduce the dust particles, two following methods are used: 1:By using statistical tests 2: By considering city’s population
The following equation was applied by the use of Excel Software:(A1-A2)÷ A1×100= (137/77-128/44) ÷ 137/77×100 Based on the first equation, pollutant reduction level in the second studied region was estimated about 6/76 percent. As table 1 and equation 1 show, pollutant reduction level to approach this standard is evaluated as 80/40%.
137/77-27=110/77÷137/77=0/4080×100%=80/40%
Therefore, through adopting evaluated levels of clean air (80/40%) and pollutant reduction percentage which is 6/76, it is clear that suggested green belt area should be increased to 12 times of its existing area which is 1 hectare so that the green belt can have its most effect on the dust reduction.
X= 80/40÷6/76=12 To evaluate the green belt area, the second equation is applied.
Green belt area: 2A× A= 120000M2 A2 = 60000 A=244/948M 2 A= 489/88M
B: determination of green belt area depends on various factors like the main purpose to establish the green belt, the climate in the studied area, water sources, provided land to establish green belt, resided population, etc. Based on Table 3, to establish a green belt which its main action is to reduce dust particles in the air, about 〖3m〗^3 of green area per person is necessary for everyone living in Zahedan city.
Considering the population based on 2011 census, the total capital is obtained as follow: 660575×3=1981725 Therefore, based on the second equation, green belt width and length was evaluated: Green belt area (m^2) =2A× A= 1981725M2 A2 = 990862/5 A=995/420M 2 A= 1990/84M Because the statistical method is an exact method to measure the green belt area, the estimated area by statistical method is used and applied in the process of designing the green belt in Zahedan city.

Based on the present study, data gathering in an annual period (From April 2015 to March 2016) was performed in the two regions located in southwestern part of Zahedan city, one with existing planting and the other one with mixed planting (second studied area). Using the mixed planting method can cause 6/77 % reduction in the amount of existing dust particles in the air. Therefore, through applying T-test and considering population, the suitable area was estimated. In the T-test method, the suitable area to establish green belt was estimated about 120000m^2. In addition, considering population and required capita for green space to decrease dust, the suitable amount of area to establish green space was measured about 1971725m^2, by using presented tables for expectations from green space. To identify local and resistant plant species to dust, plants with the following characteristics were selected: downy leaves, speared leaves, low water requirement and adaptable in every soil especially weak soils. Some suitable cases are Tehran pine, Tamarisk, Shiraz cedar, Silver cedar, Eucalyptus, Ailanthus, Pomegranate, Buckthorn, and Berry.

Atmospheric aerosol plays a significant role in the Earth's radiation budget through radiative forcing and chemical perturbations. Aerosols are intricately linked to the climate system and the hydrologic cycle. The net effect of aerosols is to cool the climate system by reflecting sunlight. Quantifying the net effect requires accurate information on the global distribution of aerosol properties that have to be estimated from satellite observations. Estimating aerosol properties is also one of the first steps in generating high-level land surface products from satellite observations. Effective aerosol retrieval information is also essential to satellite imagery atmospheric correction. Satellite remote sensing has been employed to supplement the prediction of ground-level dust concentration. Satellites are able to cover vast spaces at a relatively low cost. For aerosol studies, the launch of the Moderate Resolution Imaging Spectro-radiometer (MODIS) has enabled the retrieval of aerosol optical depth (AOD) data globally from the satellite's spectral observation. MODIS AOD is a measure of light transmittal by aerosols in an atmospheric column during the satellite overpass. With the evolution of the retrieval algorithm, MODIS AOD has become increasingly important in the role of producing more accurate estimation for the aerosol. Estimation of aerosol loadings is of great importance to the studies on global climate changes. Meteorological numerical models and ground stations are not able to tracking and detection of dust storms and in many cases have significant errors. This issue show necessitates use of reconstruction ways dust according to remote sensing techniques. The purpose of this study, use of remote sensing technology and MODIS images to estimate dust concentration on the Persian Gulf surface and estimating the linear correlation relationship between the dust measurements in ground and atmospheric. In this study, we develop a new algorithm for estimating the aerosol optical depths using MODIS data over Persian Gulf surfaces. This algorithm is validated using AERONET measurements.
In the current study we analyze atmospheric aerosol optical properties over Persian Gulf. Annually, Dust storms are imported into Persian Gulf from the West and North West and South West. Data corresponding to the station was extracted for channels of 0.644, 0.855, 0.466, 0.553, 1.243 and 1.643 µm of satellite image. The ocean algorithm was designed to retrieve only over Dark Ocean, (i.e. away from glint). There is a special case when we retrieve over glint, and that is described below. The algorithm calculates the glint angle, which denotes the angle of reflection, compared with the specular reflection angle. The glint angle is defined as:Θ_glint=〖cos〗^(-1) ((cosθ_s cosθ_v )(sinθ_s sinθ_v cosϕ)) (1)
Where θ_s, θ_v and ϕ are the solar zenith, the satellite zenith and the relative azimuth angles (between the sun and satellite), respectively. The retrieval requires a single fine mode and a single coarse mode. The trick, however, is to determine which of the (4 x 5) twenty combinations of fine and coarse modes and their relative optical contributions that best mimics the MODIS-observed spectral reflectance. The reflectance from each mode is combined using η as the weighting parameter:ρ_λ^LUT (τ_0.55^tot )=ηρ_λ^f (τ_0.55^tot )(1-η)ρ_λ^c (τ_0.55^tot) (2)
Where ρ_λ^LUT(τ_0.55^tot) is a weighted average reflectance of an atmosphere with a pure fine mode 'f' and optical thickness τ_0.55^tot and the reflectance of an atmosphere with a pure coarse mode 'c' also with the same τ_0.55^tot. Before the final results are output, additional consistency checks are employed. Our primary means of true ‘validation’ is comparison with ocean-based sunphotometer measurements, specifically, those of AERONET. The AERONET measured AOD is easily interpolated to the exact MODIS wavelengths (for example 0.55 µm) by quadratic interpolation in log reflectance/log AOD space. The AERONET ‘sun-measured’ definition of FW differs from either of the MODIS (land or ocean) definitions, but should be correlated with either. AOD images were compared with values obtained in AERONET stations, in finally AOD values were evaluated using statistical indexes of Average, standard deviation, correlation, Mean Squared Error (RMSE) and Mean Difference Square Error (RMSD). In the following validation, we use AERONET Level 1.5 data of the Dalma, Bahrain, Abu Al Bukhoosh, Sir Bu Nuair, Umm Al Quwain, MAARCO and Mussafa station when available.
Discussion of Results & The evaluation results showed that good correlation exists between the AOD simulation and AERONET data, with the correlation coefficient exceeding 0.90. The best and most suitable mode demonstrated for 1.243 and 1.643 bonds with the correlation coefficient equal to 0.94 and 0.99 and RMSE and RMSD index equal to 0. 2 and 0.02 for band of 1.243 and 0.1 and 0.01 for band of 1.643, respectively. We conclude that significant limitations exist for aerosol retrieval using marine AERONET stations. The number of matching points between the two datasets may become sufficient toattempt the reduction of the current uncertainties. Given the identified uncertainties, the results of this study do not contradict these previous validation efforts. Future research may reduce these uncertainties and require modifications to the retrieval algorithm. We used AOT data from a comprehensive set of Persian Gulf AERONET stations to evaluate the dust retrieval algorithm. Data evaluation was performed by using the Pearson correlation coefficient, root mean square error index (RMSE) and root mean square deviation index(RMSD). The evaluation results showed that good correlation exists between the AOD simulation and AERONET data, with the correlation coefficient exceeding 0.90. The regression analysis of AOD data revealed similar limitations. We found that the AOD simulation are on average 5%–25% more than the corresponding AERONET values, depending on the regression weighting assumptions for the comparison dataset. To further evaluate the performance of the algorithm in comparison with the AERONET measurements, we used the RGB image from MODIS. Overall, the comparison with the AERONET data has revealed similar performance of the two satellite datasets with a tendency of the simulation AOTs to underestimate and the MODIS over-ocean AOTs to overestimate the AERONET values. The range of these discrepancies is comparable to the uncertainties associated with the limited number of ocean stations and natural aerosol variability. The comparison of AOTs in the Persian Gulf AERONET stations showed that AOD values in AERONET stations are, on average, 5%–25% lower than the corresponding simulation ones. While the biases in ocean retrieval algorithms and cloud screening procedures may not be excluded, these results indicate that aerosol loading in marine locations may differ significantly from that in adjacent land areas, thereby limiting the achievable validation accuracy. We conclude that significant limitations exist for aerosol retrieval using marine AERONET stations. These limitations can be linked to the extreme sparsity of the marine AERONET data, uncertainties associatedwith local conditions at the marine stations, and regression accuracy limits imposed by natural aerosol variability. The number of matching points between the two datasets may become sufficient toattempt the reduction of the current uncertainties. Given the identified uncertainties, the results of this study do not contradict these previous validation efforts. Future research may reduce these uncertainties and require modifications to the retrieval algorithm.

As extreme weather events, dust storms are a recurrent feature of the climate that has contributed to severe damage to farmers. The date palm growing sector in Khuzestan province is one of the dust- prone areas that had been severely affected during recent dust storms in the region. This study aims at investigating the factors contributing to date palm orchardists’ resilience to coping with dust stress. The population for this study comprised 157 date palm orchardists residing in Ahwaz County. This study is based on primary sources of data collected from 100 orchardists, following a structured questionnaire survey design. The questionnaire’s validity was confirmed by a panel of experts. The reliability of different scales was measured by the Alpha Cronbach coefficient which ranged between 0.59-0.84. Results revealed that washing dates, using protecting nets, spraying toxins, cultivating other crops between the palm trees and searching for other sources of income were all known as resilience behaviours among orchardists. Path analysis results showed that date palm growers’ perception of resilience (β=0.43) and social motives (β=0.21) contributed positively and significantly to the date orchardists’ resilience behaviour. There was also a significant positive indirect impact between social dialogue and the resilience of date orchardists towards dusty conditions.

Wind erosion and associated dust emissions play fundamental roles in many ecological processes and provide important biogeochemical connectivity at scales ranging from individual plants up to the entire globe. Yet, most ecological studies do not explicitly consider dust-driven processes, perhaps because most relevant research on aeolian (wind-driven) processes has been presented in a geosciences rather than an ecological context. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the scale of plants and surrounding space to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. It is likely that changes in climate and intensification of land use will lead to increased dust production from many drylands. To address these issues, environmental scientists, land managers, and policy makers need to consider wind erosion and dust emissions more explicitly in resource management decisions.