JWSS - Journal of Water and Soil Science

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To estimate the biomass and secondary production of macrobenthos in Khore-e-Mousa creeks, 216 sediment samples were taken. The sampling period started in 1996 and terminated in 1997. A bimonthly sampling strategy was adopted. The samples were taken by Van-Veen grab (0.1 m²) from the beginning, middle and end of each creek (Khor). To estimate the biomass of the macrobenthos, the Crisp method (1984) was employed. The standing crop was expressed as dry weight and ash free dry weight. For the measurement of secondary production, a dominant crustacean species Apseudes sp. was used.

The results indicated a low biomass per unit area in Khore-e-Mousa creeks. Maximum and minimum amounts of the standing crop were found to be in June (33.5 g DW/m²) and December (2.19 g DW/m²), respectively. Amongst all creeks, Douragh creek displayed the highest (24.93 g DW/m²) and Beehad the lowest (2.24 g DW/m²) standing crops. During the study period, 1483 individuals of Apseudes sp. were collected and grouped into 5 age classes according to Bhattacharya (Sparre, 1989) method. The secondary production was estimated to be 0.08 g/m² ash free dry weight (AFDW). The production/biomass ratio (P/B), therefore, is calculated as 0.08÷0.18=0.44. Considering the ecological efficiency, (transfer efficiency) of different trophic levels which is about 10%, the fish production is estimated to be 2430 tons in Khore-e-Mousa area.

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Probable Maximum Precipitation (PMP) is the maximum possible amount of precipitation which could occur in a gauging station, a region, or in a watershed. Probable maximum precipitation is usually estimated by two general methods: the first is synoptic method in which short period (hourly) meteorological parameters such as dew point, wind speed and air pressure are used. The second is statistical method which is based on the statistical analysis of the 24-h maximum precipitations. In this study, the amount of 24-h PMP was estimated by Hershfield, Bethlahmy and modified Bethlahmy methods using date obtained from meteorological and Ministry of Energy over 15 or more years.

 The results showed that there exist large differences between statistical and synoptic methods however, there are rather smaller differences between Bethlahmy and synoptic methods. For modified Bethlahmy method, the results were multiplied by a coefficient of relative humidity. Then the calibrated 24-h PMP values were estimated for all meteorological stations of Iran and a contour map of 24-h PMP for the country was developed.

Results showed that a minimum value of 24-h PMP (110 mm) occurred in the central part of country and a maximum amount (260 mm) was found in both south and north parts of Iran.

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Proline as a key osmoregulating solute in plants plays an overriding role in osmotic pressure adjustment of the cell under water stress conditions. In plant, a bifunctional enzyme delta-1-pyrroline-5-carboxylate synthetase (p5cs) promotes and directs proline synthesis during drought stress conditions. The activity of this enzyme is strongly induced to increase proline concentration within the cell to prevent the impact of water deficit. In this study, the sequence coded for p5cs enzyme under the control of the cauliflower mosaic virus 35S promoter was cloned into a plasmid containing gus and nptII genes. The construct pBI121-p5cs was then transferred into Agrobacterium tumefaciens C58 (pGV3101) and used for producing transgenic tobacco(Nicotiana tabacum cv. Xanthi) plants. The amplification of a 765 bp band within p5cs gene from transferred plants and forming deep blue color in leaf tissues of the explants indicated the successful introduction of p5cs construct into nuclear genome of tobacco plants through Agrobacterium-mediated transformation. The two-month old plants growing under normal condition besides the five-day seedlings under drought stress were subjected to determination of proline concentration. Comparison of P5cs product levels between control and water tolerated plants indicated an increase of proline of about 96.91 to 1330.891 mg/g and of 204.454 to 2039.77 mg/g in plants under normal irrigation and under drought stress, conditions respectively. The significant difference between the levels of proline product in control and transgenic plants under different growing conditions demonstrated the expression of targeted gene (p5cs) in engineered tobacco plants that may pave the way to overcome the water stress problem in agronomically useful crops.

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Application of sewage sludge on the farmland as a source of crop nutrient had recently received considerable attention. Some management practices may be required to control the accumulation of toxic elements including Pb, Ni and Cd. Sequential extraction gives useful information on plant bioavailability of the elements. The objective of this study was to investigate the cumulative and residual effects of sewage sludge application on the chemical forms and mobility factor of Pb, Ni and Cd. Zero, 25, 50 and 100 Mg ha-1 of sewage sludge were applied for 1, 2 and 3 consecutive years in a split plot design, with three replications. Soil samples were taken from 0-20 cm at the end of the third year of application. Different chemical forms of Pb, Ni and Cd were measured. Results revealed that the soluble form (SOL) of Ni and Cd increased whereas Pb soluble form decreased with increasing levels and years of application. Exchangeable (EXC), carbonate (CAR) and organic (ORG) forms of the three elements increased as levels and years of application increased. Occluded (OCC) form decreased for Pb, Ni and increased for Cd. Residual form (RES) of Pb increased while that of Ni and Cd decreased. A gereral increase was observed for available (DTPA-extractable) concentration of Pb, Ni and Cd. Relative distributions of different chemical forms were in the following order: Pb: OCC > RES> ORG> CAR> EXC> SOL, Ni: RES> ORG> OCC> CAR>EXC> SOL and Cd: OCC> CAR> RES> ORG> EXC> SOL. The comparison of different forms of the metals showed the following orders: soluble Ni>Pb>Cd, exchangeable, carbonate and occluded Pb>Ni> Cd, organic and residual Ni> Pb>cd. Increasing the available (DTPA-extractable) concentration of the elements in such a calcareous soil showed that consecutive application of sewage sludge may increase the available (DTPA-extractable) concentration beyond critical levels. A significant corretation was observed between organic form and available (DTPA-extractable) concentration of the elements.

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  Phytoremediation is a new technology that employs plants to remediate contaminated soils. This method compared to those that involve the use of large scale energy consuming equipments is an inexpensive method. Phytoremediation models are useful tools to further understanding the governing processes and also to manage the contaminated soils. A thorough literature review indicates that very few models have been developed for phytoremediation due to the complexity of the phenomena. The objective of this study was to develop a simple model for phytoremediation of lead and cadmium. A new formulation of phytoremediation was established based on soil and plant responses to heavy metal pollution. A large quantity of a sandy loam soil was thoroughly mixed to ensure homogeneous different concentration levels by lead and cadmium. These contaminated soils were transferred to some plastic pots. Land Cress (Barbarea verna) and Spinach (Spinacia oleracea L.) seeds were germinated in pots containing 8 kg of contaminated soil. Plants were harvested at five time intervals. The concentrations of Pb and Cd in the plant and soil samples were digested by wet oxidation and 4 M Nitric acid digestion methods, respectively, and were determined by flame and graphite furnace atomic absorption spectrometry methods. Proposed models then were calibrated using the collected data and validated quantitatively. The results indicated that the soil adsorption isotherms followed a linear form for both Pb and Cd concentrations. The results also indicated that the phytoremediation rate of Pb by Land Cress and Spinach are first-order function of Pb concentration in soil. In contrast, a zero-order function of soil Cd contaminations was obtained. Combining these two results of soil and plant responses to Pb and Cd pollution, a simple model with reasonable performance was derived to predict the time needed for remediation of soil Pb (R² > 0.98). However, in the case of Cd, the derived models appeared to be useful to make only some overall estimations of the remediation (R²≈^�0.70).

 

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Soil water characteristic curve shows the relationship between soil water content and matric suction, which has an important role in water movement in the soil. The measurement of this curve is expensive and time-consuming in laboratory therefore, many methods have been proposed for its estimation including pedotransfer functions. By using the pedotransfer functions, soil water characteristic curve can be estimated based on other easily measured soil physicochemical properties. Parametric pedotransfer functions have been offered for parameters of the existing soil water characteristic curve models. In this study, 12 internal and external parametric pedotransfer functions of Brooks and Corey, Campbell and van Genuchten models were used and evaluated for 30 top soil samples in Fars province. To this end, the soil water characteristic curve and other necessary soil properties were measured, and then all soils according to the texture were divided into three groups of fine, medium and course textures. The results showed that the parametric pedotransfer functions of van Genuchten model were better than the other models, beacause of the better fit of this model to the measured data. Also, the results demonstrated that the parametric pedotransfer functions of Wosten et al. were the most appropriate method for estimating the soil water characteristic curve for the selected soils in Fars province, and that internal pedotransfer functions were not appropriate

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Soil contamination with heavy metals, including Cd and Pb, is of serious concern. The aim of this study was to investigate the efficiency of Atriplex verucifera, Salicornia europaea and Chenopodium album for simultaneous remediation of soil exchangeable sodium percentage and Cd and Pb contamination in two soils with different properties. Two soils, including a saline-sodic-calcareous (S1) and calcareous (S2) soil, were selected. Different concentrations of Pb and Cd were then added to the soils. The contaminated soils were incubated under a wetting-drying cycle for nearly seven months. The plants, seeds were grown in pots containing different treatments of polluted soils and in control treatment (no Cd and Pb contaminations). The plant yields and concentrations of Pb, Cd and Na in the soil and plant samples were measured. A considerable accumulation of soil Cd by Salicornia and Pb accumulation by Atriplex and Salicornia was observed under unsuitable conditions of the saline-sodic soil, whereas Atriplex and Chenopodium had high capability for Cd in the soil S2. Also these plants caused the reduction of ESP in soil S1. The results revealed that these plants could be used for remediation of Pb and Cd contaminated soils. In this study, Salicornia with lower rate of yield reduction had the highest tolerance to Cd-stress. Understanding the complex plant and soil (salinity-sodicity and soil metal concentration) factors controlling the metals concentrations in the plants will help to design phytoextraction technology for arid, salt-affected regions.

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In recent years, due to the increased population, urbanization and changes in human consumption patterns, urban, industrial and agricultural soils have been exposed to various pollutants such as heavy metals. The objective of this research was to identify hotspots of Pb by using global and local Moran Indices in urban and suburban soils of Kashafrood catchment. A total of 261 surface soil samples (0-15 cm deep) were taken using irregular girding network method and their total Pb concentrations were measured. The positive Moran index at confidence level of more than 99 percent showed the spatial clusters between observations. On the basis of local Moran index results, 15 samples were introduced as hotspots (high-high value) located southeast of Mashhad plain. Exclusion of extreme values resulted in the addition of high-high cluster (hotspots) leading to the extension of these areas to the West of the Mashhad city. These areas are introduced as hotspots due to the urban land use, the direction of prevailing wind, and the area being close to Mashhad airport.

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Pollutants are considered the disturbing factors of environment, and among them the heavy metals are more important considering their non-degradability and physiological effects on organisms in low concentrations. The goal of this research was to investigate the effect of industrial landuse on Cd and Pb concentrations in surface soils of the southwest Isfahan. According to satellite images and topographic maps (1:50000) of the study area, soil samples (depth: 0–20 cm) were collected using random sampling. A total of 38 surface soil samples were obtained from industrial areas (lowest distance = 1480 m) in the area of 73481 ha. Total concentrations of Cd and Pb in the digested solution were measured by Atomic Absorption Spectrophotometry (AAS). Using Arc GIS, the spatial distribution patterns and Cd and Pb variography of samples were analysed and finally the best models of spatial distribution of heavy metals were achieved. The primary results showed that the mean concentrations of Cd, and Pb of surface soil samples in industrial areas were 1.8 to 31.5 mg Kg^-1 higher than the world’s mean values, respectively. Although the mean concentrations of Cd and Pb were respectively 8 to 700 mg Kg^-1 lower than the standard of Iranian Department of Environment for industrial landuse.

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