JWSS - Journal of Water and Soil Science

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A field experiment was conducted to investigate the effects of sewage sludge and of time lapse after sludge application on soil physical properties. Four sewage sludge treatments (0, 25, 50, and 100 ton/ha) in a complete randomized block design with three replications were applied and mixed to a depth of 20 cm. Wheat was planted and soil physical properties were measured 23, 85, 148, and 221 days after sewage sludge application. Sewage sludge application significantly increased MWD, hydraulic conductivity, final infiltration rate, moisture percentage at 1/3 and 15 bars, and plant available soil moisture, while it significantly decreased soil bulk density. In general, the best results obtained with the 100 ton/ha sewage sludge treatment. Time lapse after sewage sludge application caused soil physical properties to approach the values of the control. However, even 221 days after sludge application, the 50 and 100 ton/ha treatments had significantly different values compared with the control treatment. The results in this research show that sewage sludge can help to improve soil physical conditions and this effect persists over long periods. This effect is specially important with plant available soil moisture and infiltration.

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The objective of this research was to evaluate bromide leaching in a field under corn, wheat and alfalfa. Potassium bromide (300 kg/ha) was uniformly applied and 15 mm of water was sprinkled over the plots in the first and second years. Plots were leached 8 times during the first year and 9 times in the second year (each time with 100 mm of water). Soil samples were collected at 0-30, 30-60, 60-90 and 90-120 cm depths two days after each leaching practice. Bromide concentration in soil samples was measured using an ion selective electrode. Moisture content in each plot was measured using a neutron meter to a depth of 120 cm and after calculation of evaporation from soil surface, the net water applied was determined. CXTFIT software and Regional Stochastic Model (RSM) were used to simulate leaching under field conditions. The results showed that flow velocity and dispersivity of treatmens were not significantly different from the control in the first year, indicating that treatments had no effect on preferential flow. Control treatments were not significantly different in the first and second years. In the second year, flow velocity in wheat, corn and alfalfa treatments were 1.54, 1.86 and 2.21 times higher than flow velocity in the control, respectively. Dispersivity in alfalfa and corn treatments were 4.30 and 5.30 times higher as compared to the control. The increase in flow velocity and dispersivity is caused by an increase of preferential flow in the second year. The root channels remaining in soil at the end of the first year may also have increased preferential flow. After adding 25 cm of water, 30% of bromide leached from the top 50 cm soil in all plots in the first year and control plots in the second year but the values in the second year were 47, 67 and 70% of bromide leaching from the top 50 cm soil in wheat, corn and alfalfa plots, respectively.

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Excessive application of sewage sludge leads to the accumulation of potentially toxic elements in soils. The objective of this greenhouse study was to examine the DTPA–extractability of Fe, Zn, Cu, Mn, Pb, Cd, Ni, and Co in relation to soil pH and to investigate the concentrations of these metals in corn (Zea mayz). The study was conducted using a factorial experiment in a completely randomized design with three replications. Sewage sludge was applied at 0, 50, 100, and 200 t/ha on four soils [Langaroud (pH= 4.8), Lahijan (pH= 5.7), Rasht (pH= 6.8), and Isfahan (pH= 7.9)]. Application of sewage sludge significantly increased DTPA-extractable Fe, Zn, Cu, Pb, Cd, and Ni in all soils. The increasing effect was in accordance with sludge level. Langaroud soil had the highest and Isfahan soil the lowest levels of DTPA-extractable metals. Application of sewage sludge increased plant growth and metals in the foliage of corn plants. The metal concentration in corn tissues also increased with decreasing soil pH. Overall, the application of sewage sludge as an organic material, particularly in acid soils, may increase availability of heavy metals, which may, in turn, result in soil pollution. Therefore, addition of sewage sludge to soils should be managed on the basis of the changes in soil heavy metal concentration.

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In recent decades, the use of nitrogen fertilizers has increased irrespective of their effects on soil properties, agricultural products and, particularly, on environmental pollution. Nitrate easily leaches from soils into groundwater. The objective of this study was to determine temporal and spatial nitrate concentrations in groundwater in agricultural, industrial and urban regions in some parts of Isfahan Province. Water samples were collected monthly from 75 agricultural, industrial, and urban wells of Isfahan, Najaf-abad, Shahreza, Natanz and Kashan during January-May 2001. The results indicated that NO₃-N concentrations in most of the regions studied were higher than the standard level (10 mg/l) and nitrate pollution must be reckoned among the most serious problems of sustainable agriculture and exploitation of groundwater resources. Average NO₃-N concentration in different wells ranged from 1.03 to 50.78 mg/l (4.64 to 228.5 mg/l as nitrate). The average NO₃-N concentration in groundwater of Najaf-abad, Shahreza, Isfahan and Natanz-Kashan was 17.56, 14.6, 16.04, and 8.24 mg/l and 95.5, 100, 84 and 33.3 % of total wells in these regions had nitrate concentrations above the standard level, respectively. Maximum NO₃-N concentration was detected in the agricultural region south of Najaf-abad (64.6 mg/l). Nitrate pollution in most of the sampling areas was mainly linked to agricultural activities. The average NO₃-N concentration in groundwater of all agricultural, industrial, and urban regions, except for urban regions of Natanz and Kashan, were above the standard level. Generally, nitrate concentration level in groundwater increased with time and was maximum in March and April.

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The objective of this study was to evaluate effects of cow manure on soil hydraulic properties and bromide leaching in a sandy loam soil (coarse loamy mixed, Typic Torrifluvents). Manure was applied at 0, 30, and 60 tha^-1 at three replications in a completely random design. Three months after manure application potassium bromide (KBr) at rate of 300 Kg ha^-1 Br was uniformly applied on the surface. Soil bulk density, porosity, organic matter, and soil moisture at18 levels of matric potentials were determined. Soil samples to the depth of 105 cm at 15-cm increments were collected after 100, 200 and 400 mm of irrigation. Soil bulk density, porosity, organic matter content, and soil moisture at different levels of matric potential increased significantly with manure application. Manure application also significantly affected the hydraulic parameters. Bromide leaching was significantly lower in plots with manure application and the greatest leaching occurred at the zero manure application treatment. The center of mass evaluation indicated a relatively similar result with measured values.

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Sewage sludge and effluents, as cheap sources of irrigation water and fertilizer, can supply plants with water and nutrients however, contamination of these sources with heavy metals and the possibility of human food chain contamination using these sources should be considered. In this research, the effects of industrial sewage sludge and effluents on concentration of some nurtients, heavy metals and sodium and dry matter yield of wheat (Triticum aestivum), barley (Hordeum vulgare) and corn (Zea mays) were investigated. The experiment was carried out in a greenhouse using a complete randomized design with four replication. The treatments comprised well water, well water + sewage sludge(50 tons/ha), and three industrial effluents from Iran Polyacryl factory including the cooling tower, the over flow and the factory outlet effluents. Chemical analysis showed the following results: The concentration of the elements in the sludge and the effluents were below the critical contaminating levels. The application of the treatments did not supply enough nitrogen for corn the cooling tower effluent could not supply enough nitrogen for wheat and barley all the treatments supplied enough P for wheat. None of the treatments could supply enough P for corn. The cooling tower, over flow and the factory outlet effluents could not supply enough P for barley, the micronutrient and heavy metal concentrations in the plant tissues using the effluents and the sewage sludge were higher than those for well water the dry matter yield of plants’roots and shoots was highest using well water + sludge and in comparison with the well water, effluents could increase the shoot dry matter yield.

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Heavy metals including cadmium (Cd) and lead (Pb) are entering agricultural soils from different routes and mainly due to human activities. Accumulated Cd and Pb in the soil would eventually enter the human and animal food chains and pose threat to their health. Therefore, evaluating heavy metal accumulation is necessary to prevent soil and environmental pollutions and should be considered by researchers as well as policy makers. This study was conducted to model the accumulation rates of Cd and Pb in the agro-ecosystems of Isfahan, Mobarakeh, Lenjan, Borkhar, Najafabad, Khomeinishahr and Felavarjan. Cadmium and lead accumulation rates in the agro-ecosystems were computed using a stochastic mass balance model which uses Latin Hypercube sampling in combination with Monte-Carlo simulation procedure. Agricultural information including crop types, crop area and yield, the type and the number of livestock, application rate of mineral fertilizers, compost and sewage sludge and also metal concentration in plant and amendments were used to quantify Cd and Pb accumulation rates. Modeling Cd and Pb accumulation rates indicated that the metals are accumulating in the agricultural lands in the studied townships. The largest Cd (18 g ha^-1 yr^-1) and Pb (260 g ha^-1 yr^-1) accumulation rates were found in the township of Isfahan but the minimum accumulation rates were found in township of Lenjan for Cd (3 g ha^-1 yr^-1) and Mobarakeh for Pb (10 g ha^-1 yr^-1). The major input route to agricultural soils is phosphate fertilizers for Cd but for Pb is manure on the regional scale. High application rates of sewage sludge and compost in agricultural lands in the township of Isfahan could result in considerable amounts of Cd and Pb entering the soils of this region.

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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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Accumulation of heavy metals (HMs) in cultivated soils is an important environmental problem in many parts of the world. In recent years, HM leaching through preferential paths and also in the form of metal-organic acids complexes has received much attention. For this reason, the effects of plants on creating preferential flow through the soil is important. The objective of this study was to assess the mobility of Cd, Cu, Pb and Zn in a calcareous soil (Typic Haplocalcids) planted with safflower (Carthamus tinctorious). The study was conducted on 12 undisturbed soil columns (22.5 cm in diameter and 50 cm in depth) in greenhouse. The top 10 cm of soil in half of the columns were contaminated with Cd, Cu, Pb, and Zn at the rates of 19.5, 750, 150 and 1400 kg ha^-1, respectively. Half of the contaminated and uncontaminated columns were planted with safflower at a rate of 20 seeds m^-2. Leachate was collected continuously and analyzed for these four heavy metals. After the crop harvest, soil samples were taken at 10 cm intervals and analyzed for DTPA-extractable and water-soluble HMs concentration. Results showed that heavy metal concentrations (DTPA and soluble) of the subsoil in planted columns were more than in fallow columns. The DTPA-extractable Cd, Cu and Zn concentrations in contaminated planted columns were 3.3-, 1.5- and 1.5-times more than in contaminated fallow columns, respectively. The water-soluble Cd, Cu and Zn in planted treatments increased 2.4, 1.2- and 1.1 times more than the fallow treatment. Lead concentrations in both planted and fallow treatments were similar. Metal uptake by safflower increased such that Cd and Zn uptake was more than Cu and Pb. Cd, Cu, Pb and Zn concentrations in the leachate of planted columns increased 32.0-, 2.5-, 6.0- and 2.7- time more than the uncontaminated planted columns. In summary, although topsoil contamination increased metal uptake by safflower, however the presence of safflower increased DTPA-extractable and also soluble metal concentrations in the soil profile and therefore enhanced metal mobility. The order of metal mobility was Cd > Zn >Cu >Pb.

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Sewage sludge application on farmland as fertilizer is commonly practiced in many countries. Sewage sludge is rich in macro- and micro- nutrients. However, high concentration of heavy metals in sludge may cause pollution of soil, groundwater and human food chain because of uptake of toxic metals by crops. The objective of this study was to determine residual and cumulative effects of sewage sludge on concentration of Pb and Cd in soil and wheat. Different levels of 0, 25, 50 and 100 Mg ha^-1 of sewage sludge were applied to the soil for four years. To study the cumulative and residual effects of the sewage sludge, applications were repeated on three fourth of each plot in the second year, on one half of plots in the third year and in one fourth of plots in the fourth year. Wheat grown in the plots, after the fourth year, soil samples from the 0-20 cm depth of the different parts of the plots were taken and analyzed. Wheat was also harvested roots, stems and grains were separately analyzed for the heavy metal concentritons. Cumulative sewage sludge application increased OM, CEC, ECe, total and DTPA-extractable concentration of Pb and Cd in soil significantly (P≤ 0.05). Residual sewage sludge in the soil also increased CEC, total and DTPA-extractable concentration of Pb and Cd significantly. Single sludge applications at different rates increased the DTPA-extractable concentrations of heavy metals. In subsequent years with no further sludge application, DTPA–extractable metal concentrations in soil decreased continuously approaching the levels in the control. However, even after four years, DTPA-extractable concentration of Pb and Cd, were still significantly higher in plots which received more than 50 Mg ha^-1 sludge than control. DTPA-extractable concentrations of Pb was closely correlated with total concentrations. Sewage sludge increased concentration of Cd in roots and stems and Pb in grains significantly. Cumulative effects on concentrations of Pb in grains, and Cd in stems were more than residual effects. The results of this study show that cumulative and residual effects of sewage sludge application increased concentrations of heavy metals in soil and wheat.

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The management and application of organic wastes in agricultural lands decreases environmental risks and increases utilization of these matters. The objective of this research was to investigate and compare the effect of polyacryl factory sewage sludge (PSS), municipal compost (MC) and cow manure (CM) on soil properties and on yield and growth of maize (single cross 704, Zea mays L.). The treatments were control (without any organic waste) and application of PSS, MC, and CM at two rates (15 and 45 t ha-1). This research was done in the research farm of Isfahan University of Technology (Lavark-Najafabad). The experimental design was a randomized, complete block with three replications. Treatments were incorporated into the soil before the maize planting (on 23 June 2008) and soil sampling was performed after 132 days (Simultaneously with maize harvesting). Application of the organic wastes resulted in significant increase soil organic matter (SOM), total nitrogen (TN) and saturated hydraulic conductivity (Ks) and significantly decreased bulk density. However, saturated hydraulic conductivity was decreased by application of PSS. Application of 15 and 45 t ha-1 of PSS reduced Ks more than 14% and 42%, respectively, compared with control however, the reduction was significant only in the plots which received 45 t ha-1 of PSS compared with control. The results of plant yield and growth showed that leaf area index (LAI), plant length, biological yield, 1000 seed weight and seed yield increase due to the application of organic wastes.

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Organic matters are the most important factors that affect soil compactability and physical characteristics. In order to study the effect of pistachio waste on physical characteristics of two soils, a factorial experiment was conducted in a completely randomized design with three replications in a greenhouse. The treatments included pistachio waste at 4 levels (0, 3, 6 and 9 w/w %) and two types of soil texture (silty clay loam and sand).The results showed that the bulk density of sandy soil was decreased at high levels of waste application before compaction but had no significant effect on the bulk density of clay soil. The penetration resistance of both soil types was decreased by pistachio waste application. Soil water holding capacity increased and moisture curves shifted up for higher levels of organic matter application, while compaction curve reciprocally shifted into the lower levels by incorporation of wastes into the soils. At higher levels of organic matters, maximum bulk density was decreased and critical moisture was increased specially in fine texture soil. After compaction, the application of pistachio waste significantly reduced penetration resistance in silty clay loam soil relative to control but in sandy soil its effect on penetration resistance was only significant at maximum level (9 %).

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Micronutrients such as Fe and Zn in adequate level are essential for plant growth cycle and impose a vital role in increasing yields of most agricultural crops. Using organic wastes such as sewage sludge, compost and manure is a proper practice for returning organic matter and some nutrients into the soil, particularly in arid and semi-arid regions. The objective of this study was to determine the effects of sewage sludge, compost and cow manure on availability of Fe and Zn in soil and their uptakes by corn, alfalfa and targetes flower. A completely randomized design with three treatments (sewage sludge, compost and cow manure at 25 Mg/ha) was used. Application of sewage sludge, compost and cow manure significantly increased availabile Fe and Zn of the soil. The application of organic wastes increased the dry matter yield of the plants. Fe and Zn concentration of plants shoots in organic amendments treatments were significantly greater than blank. The highest mean concentration of Fe in plant tissues was obtained in the cow manure and the highest mean concentration of Zn in plant tissues was obtained in the compost treatment.

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The petroleum refinery sludge is an important source of environmental pollution. Burning and burying of the sludge may have adverse effects on environment and human health. Thus, other mechanisms for decreasing the toxic effects of hydrocarbon substances in the sludge must be used. In this study, Isfahan refinery sludge was dewatered, air dried and mixed by 0, 10, 20, 30 and 40% w/w ratio with two calcareous soils, viz., Mahmoud Abad (Typic Haplocalcids with clay texture) and Bagh Parandegan (Anthropic Torrifluvents with silty loam texture). Different mixtures of soil and sludge were farmed for 21 days and irrigated on a daily basis to field capacity. Then, 100 seeds of Tallfescue (Festuca arundinacea) and Agropyron were planted in polluted soils with 3 replicates in 3 kg pots for 5 months. Result showed that Tallfescue and Agropyron yields decreased in sludge contaminated treatments. In the 40% sludge treatment, Tallfescue decreased the total petroleum hydrocarbons content by 65 percent. The highest degradation for agropyron was in the 30% sludge treatment which showed about 55% reduction in total petroleum hydrocarbons. The 40% sludge treatment resulted in the minimum yields of root and shoot plants. The highest degradation of TPHs occurred in the Tallfescue rhizospher of 40% sludge. Maximum degradation of TPHs on the Agropyron rhizospher was in 30% sludge mixed with Bage parandegan soil, but maximum yield of plant was in 20% sludge. Our study shows that Tallfescue rhizospher is most effective for decreasing TPHs, and that the phytoremediation in soils with more clay can adsorb and fix the toxic components and then at higher levels of pollutions can let the plants grow.

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Among the environmental pollutants, heavy metals according to their irresolvable and physiological effects on living organisms at low concentrations, are of special importance These elements due to low mobility are gradually accumulated in soil Being accumulated in soil, they eventually enter the food chains and threaten human health and other creatures Therefore, studying concentration distribution of heavy metals for soil pollution monitoring and maintaining environmental quality is essential In this study we investigated the effect of agricultural land use and geology on the concentration of heavy metals contamination of soil and spatial distribution map, using collected data, GIS and GeostatisticsUsing systematic stratified random sampling, 135 surface soil samples( 0-20 cm) from an area of 7262 sq km area and we measured total concentration of elements Nickel, Chromium and Cobalt and soil characteristics including pH, organic matter and texture. The mean value of elements concentrations turned out to be Cr: 88.9+22.7 Co: 17.6+3.5 Ni 63.1+17.7 mg per kg and the mean acidity is 7.8 which in the area is an indication …… property. Formetal concentrations interpolation procedures, Geostatistics was used. By the aid of spatial correlation analysis, appropriate interpolation method using functions mean absolute error and bias average error were selected. Interpolation map concentrations of heavy metals Chromium, Cobalt and Nickel with ordinary kriging method and the exponential model were developed Interpolation map analysis of heavy metals by the aid of geological and land use maps show that the distribution of the elements Chromium, Cobalt and Nickel are consistent with the geology classes However, they did not match the agriculture pattern Findings of this study in the area give us appropriate information about the concentration distribution of heavy metals Chromium, Cobalt and Nickel which can be used in monitoring and evaluation processes of heavy metals pollution in agricultural lands area. But on the other hand sampling in the areas far away from human effects, showed that the heavy metals concentration is naturally high.

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This study was carried out to investigate zinc (Zn) and cadmium (Cd) concentration in paddy soil and rice grain produced in central and southwest Iran in relation to soil and plant factors, and their intake in peoples diet was also assessed. Rice crops and associated surface soils (0-30 cm) were collected from 136 fields in Isfahan, Fars and Khuzestan provinces. The result, showed the DTPA-Zn concentration in more than 50% of paddy soils was less than its critical deficiency concentration (2 mg kg-1). The grain Zn concentration in more than 54% of the rice samples was less than 20 mg kg-1. The measured Cd concentrations in paddy soils and edible part of rice exceeded the world health organization (WHO) value in more than 12% of the samples. By considering the average daily rice consumption of 110 g per capita, the Zn intake from rice consumption was estimated about 10% needed for female and male adult. Diet intake analysis did not indicate any excessive dietary intake of Cd when Cd mean of concentrations in rice grain was 0.04 mg/kg, but based on the results of risk analysis, it is more than safely level for contaminated rice.

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Cow manure and sewage sludge add heavy metals to soil. Organic and inorganic fractions in these compounds can immobilize heavy metals such as lead (Pb) and affect their bio-availability. This investigation was conducted to compare the effects of organic and inorganic fractions of sewage sludge and cow manure on distribution of lead chemical forms in soil as a completely randomized design. Treatments consisted of application of 10% (w/w) enriched sewage sludge and cow manure (6 g Pb kg-1 organic amendments). Another treatment was also used in which soil Pb concentration was increased to 600 mg kg-1 soil using Pb(NO3)2 salt. To compare the effects of organic and inorganic fractions, organic carbon, iron oxide and easily reducible iron and manganese were removed from cow manure and sewage sludge, and were added to the soil by 10% (w/w). The samples were incubated at 23-25ºC for 111 days and their moisture was maintained at 80% water field capacity. More than 50% Pb in Pb(NO3)2 treatment was in exchangeable fraction, while for cow manure and sewage sludge treatments more than 40% Pb was found to be in oxide fraction. Application of cow manure and sewage sludge increased the Pb in oxide fraction by 14.8 and 17.5%, respectively. Removing organic carbon fraction of cow manure and sewage sludge increased the Pb bound to residual fraction by 12% and 14% respectively. Removing iron oxide fraction of sewage sludge and cow manure decreased the Pb bound to oxide fraction by 8% and 13%, respectively. Removing easily reducible iron and manganese decreased the oxide fraction of Pb by 16% and 14%, respectively. It is concluded that, despite relatively high amounts of organic carbon in the sludge and manure, inorganic fractions of these materials have more significant effects on availability of Pb in soil.

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The task of modern agriculture is to safeguard the production of high quality food, in a sustainable natural environment under the precondition of pollution not exceeding accepted norms. The sustainability of current land use in agro-ecosystems can be assessed with respect to heavy metal accumulation in soils by balancing the input/ output fluxes. The objectives of this study were to model accumulation rate and the associated uncertainty of Zn in the agro-ecosystems of 3 arid and semi-arid provinces (Fars, Isfahan and Qom). Zinc accumulation rates in the agro-ecosystems were computed using a stochastic mass flux assessment (MFA) model with using Latin Hypercube sampling in combination with Monte-Carlo simulation procedures. Agricultural information including crop types, crop area and yield, kind and number of livestock, application rates of mineral fertilizers, compost and sewage sludge and also metal concentration in plants and soil amendments were used to quantify Zn fluxes and Zn accumulation rates. The results indicated that Zn accumulates considerably in agricultural lands of the studied townships especially in Najafabad (3009 g ha-1yr-1). The major Zn input routes to the agricultural soils (and due to agricultural activities) were manure and mineral fertilizers and the major part of the uncertainty in the Zn accumulation rate resulted from manure source.

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Models are helpful tools to predict runoff, sediment and soil erosion in watershed conservation practices. The objectives of this research were to investigate sensitivity analysis, calibration and validation of EUROSEM model in estimation of runoff in Tangh-e-Ravagh sub-basin of Karoun watershed. The model was tested in a one hectare experimental test site. The area was divided into nine elements according to EUROSEM user's manual. A triangular weir was installed at the outlet of the area to collect runoff in specified time periods for six rainfall events. Sensitivity analysis of the model was performed by a ±10% change in the dynamic parameters of the model and examining the outputs for a rainstorm. Sensitivity analysis showed that total runoff was sensitive to saturated hydraulic conductivity and insensitive to soil cohesion. Sensitivity analysis indicated that the model sensitivity depends on evaluation conditions and it is site-specific in nature. Calibration and validation of the model was performed on input parameters. Calibration of hydrographs was performed by decreasing saturated hydraulic conductivity and capillary drive and increasing initial soil moisture. Validation results showed that EUROSEM model simulated well the total runoff and peak of runoff discharge, but it could not simulate well the time of runoff, time to peak discharge

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Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate contamination in surface and groundwater and increases N applications to crops. This is because negatively charged nitrate normally does not have much affinity to soil particles. To retard the movement of nitrate, materials should have high affinity for anions, which most naturally occurring minerals do not have. The cation-exchange properties of natural zeolites can be exploited to modify their surface chemistries so that other classes of compounds, particularly anions and non-polar organics are retained. In this study, the ability to remove nitrate from aqueous solutions with different Cl- concentrations using Iranian zeolite (Semnan) modified by hexadecyltrimethylammonium bromide in millimeter and nanometer particle sizes was determined and the equilibrium isotherms were characterized. The nitrate release as affected by time and ionic strength was also evaluated. It was demonstrated that SMZ is capable of adsorbing more than 60 mmol kg-1 and 80 mmol kg-1 nitrate in millimeter and nanometer sizes, respectively, and adsorbed nitrate can be easily released under different ionic strengths. The millimeter and nanometer-sized SMZ showed 26.7% to 82.3% and 37.8% to 85.5% nitrate removal efficiency, respectively. The average of nitrate released by millimeter-sized SMZ was 6.92 mmol kg-1 in deionized water while it was 14.68, 22.71, and 34.91 mmol kg-1 in releasing solutions with ionic strengths of 0.03, 0.1, and 0.3 M, respectively