جستجوی مقالات مرتبط با کلیدواژه « پراکنش مکانی » در نشریات گروه « آب و خاک »

Wind erosion is one of the environmental problems worldwide, particularly in arid and semi-arid areas of Iran. Different methods and models have been proposed to measure and monitor wind erosion in the recent years. One of the accurate models for measuring f wind erosion is the USEPA model. The purpose of this study was to evaluate the quantification of wind erosion with the USEPA model and the comparison of different interpolation methods for drowsing high-precision soil erosion mapping. For this purpose, 50 samples from 0-30 depth were taken from the study area. Based on the analysis of the physical properties of the soil, including the distribution of the primary and secondary particle sizes, climatic parameters such as evaporation and transpiration, rainfall, wind speed and also, the vegetation and topography characteristics of the area, the erosion rates of Q, Q30 and Q50 were measured. Interpolation methods including general kriging, IDW, LPI and RBF were compared. The results showed that the highest erosion emission rate of Q50 was 39 ton ha-1. The highest and lowest erosion rates for the Q30 index were 0.060 and 2.694 ton ha-1, respectively; for the Q index, the highest and lowest erosion rates were 0.009 and 0.055 ton ha-1, respectively. The results also showed that the IDW method for the Q50 index with the minimum error rate (RMSE) values of 3.94 and the mean absolute error (MAE) with the valueof 1.89 had the best performance among the studied models. The LPI model Q had the best performance with the lowest error (0.0086) and absolute absolute error (0.0021).

Knowledge of the spatial variability of soil properties is vital for improving productivity and sustainable management of agricultural practices, as it is directly contributing to variability in crop yields. This study was conducted to investigate the spatial variability of some soil properties and their relationships with spatial variability of tea yield in the Fouman region of Guilan province. Soil samples were collected from 0 to 40 cm depth in 70 observation points. The green tea leaves were harvested at a 4 m2 plot at each site. Physicochemical soil properties and tea yield were determined according to standard methods. In order to address the cumulative impact of soil properties on tea yield, some soil physicochemical layers were subjected to delineate the study area into management zones. Soil parameters varied throughout the study area and their coefficients of variation ranged from 5.1% to 37.2% for pH and available potassium, respectively. Experimental semivariograms indicated moderate to strong spatial dependencies for all selected parameters. Spatial distribution maps, derived by kriging interpolation, showed that the spatial trend of the yield was approximately similar to pH, organic carbon and available potassium, which expresses the spatial correlation of these soil properties with the tea yield in the region. Correlation analysis revealed that tea yield was significantly positively correlated with organic carbon and available potassium (0.53 and 0.37, respectively) while negatively correlated with pH (-0.45). The results suggested the significant effect of soil properties, especially pH, organic carbon and available potassium on the tea productivity. The results indicated that the study area was successfully delineated into four distinct management zones based on spatial variability of soil properties. The spatial variations of soil properties can be used to identify the major sources of variability in crop yields and also to delineate the management zones. Therefore, the spatial variability of soil properties provides a basis of information for sustainable production in the tea gardens in the study area.

The spatial variability of soil properties and its importance in production is a matter-of-debate. Insight about the variability of soil properties as well as the yield of orchards is necessary to achieve higher productivity and better management. Orange is one of the most important export products in our country and to sustainable production of this product, it is necessary to identify the factors affecting its growth. This study was performed to examine the statistical and geo-statistical relationship of some soil properties with the quantitative, qualitative and vegetative properties of Valencia orange in Kazerun area, Fars province.
The study area contained 1 hectare (Valencia orange crop) of 205-hectare orchards of Rashnabad on the west of Kazerun, Fars province which is 860 meters above the sea level. 120 soil samples were collected from two depths of 0-40 cm and 40-80 cm (according to the root distribution) in order to investigate the statistical and geo-statistical relationship of some soil properties with the properties of Valencia orange. The sampling in the shade and with a minimum distance of one meter from the trunk of the tested tree was performed (It should be noted that orange trees have been planted as row planting with a distance of 5 meters from each other). In addition to the soil samples were collected for statistical studies from the depths 0-40 and 40-80 cm, the combined sampling of two trees that had less distance to the selected points was performed to measure the performance and quality of orange. It should be noted that all the Valencia trees, their age (about eight years) and management approach were similar. Soil samples were then transferred to the laboratory and air dried, the separately packed and passed through 2 mm sieve.Then, different soil and orange properties including soil texture, pH, EC, %OM, %CaCO3, solution potassium and available phosphorous, iron, zinc and manganese, branch length and branch diameter, trunk perimeter, trunk diameter and tree height, total soluble solids, acid percentage, Vitamin C, number of fruits,orange yield,average fruit weight and average fruit size were determined and the data set were analyzed using Statistica 6.0 software.Variograms of the data were drawn using variowin 2.2 and after determining the best fitted model, kriging maps of soil and fruit were prepared using Surfer9 software.
The results of correlation coefficient showed the significant and positive relationship between organic matter and available manganese of topsoil with total yield and number of fruits. According to the results of fitness of standard models to the empirical exponent change, all the properties had spatial structure. Soil properties including the percentage of clay, the percentage of organic matter, soluble potassium, phosphorous, available zinc and manganese in both depths in the eastern and south-eastern direction of the study area were higher than that of the others. These maps had the same spatial distribution pattern in terms of orange properties including the diameter and length of the current year branch, performance, number of fruits, average fruit size, acid percentage and total soluble solids.
The variability coefficient of soil and fruit properties did not show a consistent trend in the study. According to the correlation coefficients, in a few cases, a positive significance correlation was observed as an example, it can be referred to the positive significant correlation of orange yield with the organic matter and manganese in the depth of 0-40 cm. All the studied variables have spatial structure. Among the studied variables, the percentage of organic matter, clay particles percentage, soluble potassium, phosphorous, and available manganese in both depths showed the same spatial distribution pattern as that of the vegetative, qualitative and yield properties of orange including the total performance, fruit number, fruit size, the diameter and length of the current year branch. The proximity of the ranges of soil and fruit properties supports this result and is in line with the results of correlation coefficient. The results also showed that the spatial distribution and pattern of soil and crop variables may be different in a short distance with the same management. The study of the effect of NPK fertilizers on vegetative, qualitative and quantitative properties of orange in the region orchards is recommended. It is also suggested to study the effect of climatic factors on the orange qualitative properties.

Considering progressive growth of industry and technology, the accumulation of environmental contaminants, especially heavy metals (HMs) in the soil is of increasing worldwide concern about the probable soil pollution risks. The perception of pollutants spatial distribution pattern and recognition of factors which control this pattern and identification of probable sources of pollution, are the most important purposes in the environmental pollution studies. The present study was conducted to achieve to useful information to distinguish the role of natural sources from the human ones, using modeling the spatial variability pattern of heavy metals pollution load index in the Zanjan Zinc Industrial Town area.
In the present study, 85 topsoil samples (0-20 cm) using a regular grid sampling pattern were collected. The total (Nitric-acid extractable) contents of Zn, Pb, Cd, Ni and Cu were measured for each soil sample using atomic absorption spectroscopy. Assessing the soil pollution risk with selected HMs, contamination factor was calculated. Accordingly, sampling locations were classified into the different soil contamination classes. In order to simultaneous assessment of the status of overall soil pollution by the pollutant elements, pollution load index (PLI) of studied heavy metals was calculated. Afterwards, PLI was considered as an environmental variable which its values at un-sampled locations were interpolated using ordinary kriging method.
Comparing the measured HMs contents with their maximum permissible limits in the soil showed that the studied soils are polluted with Zn, Pb and Cd, but non-polluted with Ni and Cu. The total concentration of Zn, Pb and Cd in the soil showed a great degree of variability, indicated by large coefficients of variation (CV) from 140.5 % of Cd to 185.6 % of Pb. These elevated CVs may indicate that these elements’ distribution in the studied area is influenced by an anthropogenic source. In contrast, the relatively low calculated CVs for Ni (78.1 %) and Cu (80.3 %) may imply that natural sources are responsible for these elements’ distribution in the studied soils. Classification of observations according to the contamination factor of studied heavy metals showed that most of sampling points occurred in the very high contamination class regarding Zn and Pb (65.9 % and 68.2 %, respectively) and in the medium contamination class regarding Cd, Cu and Ni (57.7, 51.8 and 68.2 %, respectively). Mapping the spatial variability of heavy metals pollution load index showed that areas with highest pollution contents occurred in the contiguity of Zinc Town.
Totally, industrial activities related to Zn production caused to simultaneous entrance of several heavy metals to the adjacent soils and lead to degradation of the lands in studied area. Considering the low efficiency of single-element maps for HMs to reflect the overall soil quality in relation to environmental contaminants, modeling of the spatial variability of PLI may provide the good perception of the contaminant's spatial distribution and their effects on soil quality.

Spatial and temporal distribution of dust deposition rate (DDR) in Isfahan city and the influencing climatic parameters were studied. Dust samples were collected using glass trays placed on the roof of one-story buildings from 20 sites in Isfahan city for 12 months. Climatic data were obtained from Meteorological Organization and analyzed. The highest and the lowest amount of DDR in agreement with the direction of prevailing wind were observed for dry months with eastern and northeastern wind directions and wet periods with western and southwestern wind directions, respectively. This can indicate dust emission from the desert located in eastern part of Isfahan city. Statistically significant inverse correlation between DDR and precipitation and relative humidity, and significant and positive correlation of DDR with Min and Max temperatures in all the studied months and also with Max and average wind speed for dry sampling months may well justify the temporal distribution of DDR in the city. In dry months, finer particles from eastern desert can be transported a longer distance and deposited in the western part of the city, far from the source area. In wet seasons, however, soil aggregates become coarser as a result of particle adhesion. This, in turn, results in the deposition of dust near the source area as the transporting power of dust reduces.

One of the most important soil contaminants are heavy metals. Chemical analysis of the samples can be used to evaluate the contamination but these methods are expensive and time consuming. Thus, for rapid evaluation, other techniques such as magnetic susceptibility are considered. The aim of this study was to compare the spatial distribution of magnetic susceptibilityand cadmium, lead, nickel and copper in soil series of Isfahan, Khomeinishahr and Zayanderood in Lenjan at region, Isfahan province. Estimation of heavy metals via pedotransfer functions using magnetic susceptibility was also investigated. Total concentration of Cd, Pb, Ni and Cu in soil samples was determines and the magnetic susceptibility of the samples was also measured. Results showed magnetic susceptibility does not have high accuracy for estimation of heavy metals contents in the soils of this region. On the other hand, similar trends of continuous maps for heavy metals and magnetic susceptibility suggest that magnetic susceptibility can be a good indicator for trend of soil contamination in this area.

Groundwater is the most important source of water supply for agricultural purposes in arid and semi-arid areas. In many areas, excessive use of high quality water resources leads to reducing the available water resources and turning to the use of low quality water resources. Thus, knowing the temporal and spatial variation of groundwater quality is a necessary factor for implementation of sound water resource management and establishment of the suitability between water quality and its usage. In order to investigate water quality changes, this study was divided into two phases. In the first phase, for evaluation of the quality of groundwater for irrigation 76 wells were sampled in Bahadoran plain, in the year 2006. The SAR, EC, ions B3+ and Cl- were analyzed as the evaluation indexes. Then, using geostatistical methods the maps of each parameter were prepared. Finally, considering FAO criteria, these maps were overlaid and separate water quality maps were derived. The EC map indicated that in 48 and 52 percent of the groundwater lies in severe and slight to moderate restriction class for irrigation purposes. Moreover, the thematic map of infiltration restrictions indicates that the groundwater has no restriction in 66 percent of the area while 11% of groundwater causes low to moderate and 23 percent causes severe limitation. In the next phase, to examine changes in groundwater salinity during a 5-year period, 38 wells were sampled and the groundwater salinity map for the year 2011 was prepared. Finally, using subtraction of the salinity maps of given years, the salinity changes map was derived. The results of thematic map showed that groundwater salinity increased in 26.47 percent of the study area. In contrast, there was a decrease of about 31.14 percent in groundwater salinity over the 5-year period while 42.39 percent of the region’s groundwater remained unchanged. Since the study area is under cultivation of pistachios and salt threshold of this tree is 8 ds/m so the area of about 8 percent of the area was added to the previous limited areas. Therefore, irrigation management and planting development plan in Eastern and Southeastern areas should be revised.

Reasonable estimation of soil physical properties is very important for optimal management of soil and water resources. Estimation of soil physical properties is usually time consuming and expensive. Geostatistical methods can be used as suitable tools to estimate such properties. In order to analyze spatial variability of soil properties in Dareh Viseh rangelands, a number of 78 soil samples from 0-30cm soil depth were taken and transferred to laboratory. Some soil properties including clay, silt, sand and bulk density were measured in laboratory. After normalizing the data, the semivariograms were obtained and evaluated. The Kriging, inverse distant weighting and radial basis function methods were then evaluated for the obtained data. To compare these methods, the cross validation method was used by statistical parameters of Mean Absolute Error (MAE) and Mean Bias Error (MBE). The results showed that the Kriging method can provide more reseanable predictions for silt, sand and bulk density, while the radial basis function provides better estimate to predict clay content in the study area.