H. Neisi; A. Khademalrasoul; H. Amerikhah
Abstract
Introduction: Soil erosion is one of the most important forms of soil degradation which topographical characteristics are effective on its occurrence and spatial distribution. Actually, soil erosion is one form of soil degradation that includes on-site and off-site effects and the off-site effect is ...
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Introduction: Soil erosion is one of the most important forms of soil degradation which topographical characteristics are effective on its occurrence and spatial distribution. Actually, soil erosion is one form of soil degradation that includes on-site and off-site effects and the off-site effect is deposition and sedimentation. In recent decades, the potential of soil erosion has been recognized as a serious threat against soil sustainability. Topographical attributes such as slope gradient (S) and slope length (L) are considered as the most important land surface properties which control energy fluxes, overland and intra-soil transport of water and sediment, and vegetation cover distribution within a landscape. The L and S are two main factors in the USLE equation which are meaningfully effective on soil erosion. The development of modern techniques such as geomorphometry has made it possible to quantify these attributes in GIS environments. Geomorphometry or terrain analysis is a computer technology-based science in which morphometric and hydrological attributes are calculated by a series of mathematical algorithms from a digital elevation model (DEM). WaTEM/SEDEM is water and tillage erosion model/sedimentation which is possible to estimate water erosion and also different forms of sediments in the watershed and hydrographical network. The accuracy of DEM in this model is really important and effective on the quality of model outputs.
Material and Methods: Landscape planning tools might help simplify the complexity of soil erosional processes. Furthermore, using predictive tools open up for the possibilities to investigate the effectiveness of different management scenarios on soil erosional responses to make a decision for improving soil properties by application of BMPs. Soil erosion modelling as a landscape planning tool is an efficient way to investigate the on-site and off-site effects of erosion. At the same time this tool opens up for an opportunity to perform scenario analysis with the respect to the placement of structural BMPs such as buffer zones. The soil erosion model WaTEM has been used as a landscape planning tool. WaTEM is a spatially distributed empirical model to simulate both erosion and deposition by water explicitly in a two dimensional landscape. This soil erosion model has been used as a landscape planning tool. The Universal Soil Loss Equation (USLE) has been developed to predict sheet and rill erosion. Desmet and Govers (1996) showed that using the 2D-calculation of the LS-factor in WaTEM made it possible to predict rill, interrill, and ephemeral gully erosions. In this study the spatial distribution of soil erosion and deposition affected by different LS-factors were investigated using WaTEM/SEDEM model that including rainfall erosivity (R-factor), soil erodibility (K-factor), topography (LS-factor), crop cover (C-factor) and management (P-factor) as GIS layers (.rst format) in Zoji watershed located in Shush (Khuzestan province). The WaTEM/SEDEM includs three main input parts, the first part consist of DEM, parcel map and stream network. The second part is CP factor and the third part consist of LS algorithms. The variations of LS algorithms are a milestone of this model and provide the possibility to define different LS situations in the watershed. In order to evaluate the effectiveness of LS algorithms, in the simulation process Govers, McCool, Nearing and Wishmeier-Smith algorithms were defined for WaTEM/SEDEM model.
Results and Discussion: Results of correlation (R=0.78) showed that topography had the highest effect on soil erosion distribution. Also our results illustrated that the amount of deposition in forms of total sediment production (TSP), total sediment deposition (TSD) and total sediment export (TSE) between different LS algorithms were disparate. Based on prediction of rill and interrill erosion, Nearing algorithm was the best LS algorithm and Govers algorithm was convenient in order to monitor and evaluate gully erosion. This study results showed that Govers algorithm estimated the highest amount of TSP because the Govers algorithm basically estimate the sheet, rill, interrill and gully erosion, therefore the amount of sediment in this algorithms is the highest one. For Govers algorithm the estimated TRE was the highest because the Gully erosion also was in the calculations and mostly the volume discharge originated from Gully was significantly higher than sheet and rill erosion. Therefore, regarding the types of prevailing erosion in each case the type of selected LS algorithm to simulate soil erosion and deposition distribution should be different.
Conclusion: In general, WaTEM/SEDEM and its LS algorithms is a suitable tool to select and apply best management practices (BMPs) to control soil erosion at critical areas and hotspots. Our results confirmed that regarding the selection of each LS algorithm, the amount of sediment components and their distribution could be different.
M. Biria; Abdulamir Moezzi; H. AmeriKhah
Abstract
Introduction: Among wide variety of soil pollutants including heavy metals, acidic precipitation and other toxicants, the importance of heavy metals due to their pollution capacity has received growing attention in recent years. These metals enters into soil through municipal and industrial sewage as ...
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Introduction: Among wide variety of soil pollutants including heavy metals, acidic precipitation and other toxicants, the importance of heavy metals due to their pollution capacity has received growing attention in recent years. These metals enters into soil through municipal and industrial sewage as well as direct application of fertilizer and pesticides. High cadmium and lead concentration in soil lead to severe environmental pollution. Such pollution not only has a destructive effect on crop yield but also endangers human being and other creatures’ health after entering in their food chain. Several physical, chemical and biological methods used to reduce the adverse effect of high concentration of heavy metals in soil. In spite of the hight cost, these methods are not always suitable for reclamation of small area and mostly have side effect on physico-chemical and biological characters of soil, after application. Biochar produced by thermal decomposition of biomass in the absence or presence of low oxygen. These material due to their high spacific surface area and high cation exchange capacity may have great ability to absorb charged material including heavy metals. Therefore in this study attempt is made to evaluate the effect of sugarcane bagasse –derived biochar in improving maize plant growth in cadmium and lead contaminated soils.
Material and methods: This study was carried out during the year 2014 in two separate experiments in Shahid Chamran university. The treatments in each case consisted of two levels of sugarcane bagasse made biochar (0 and 4 percent by weight) in combination with each soil, properly contaminated with 50 and 100 mg cadmium per kg soil in first experiment and 500 and 1000 mg lead per kg soil in the second. The treated soils were applied to pot and arranged in a complete randomized block designe and replicated 3 times. Prior to introduction of soil to pots, the heavy metal contaminated soils with moisture content around 70 percent of F.C. were incubated for 30 days. During incubation period sugarcane bagasse was dried, milled, sieved, compacted and subjected to traditional furnace at 550 oc for 3 hours on low pyrolysis. The furnace temperature was controlled manually using lesser thermometer. The furnace cooled down and the collected sugarcane bagasse made biochar sieved again. The incubated soil mixed with proper amount of sugarcane bagasse made biochar and incubated under previous condition for 45 days. The treated soils were poured to the labeled pots and 3 maize seeds were sown in each pot and two weeks after emergence thinned to one plant per pot. Nineteen days after sowing, the height of the plants and chlorophyll index were recorded and plants were harvested and leaf area of each plant was recorded, maize root content of each pot were carefully separated from soil and along with shoot property washed, dried, weighed and after milling subjected to chemical analysis. Prior to sowing maize seeds some of physic- chemical properties of untreated soil were estimated. Furthermore few charactoristics of sugarcane bagasse made biochar including pH and EC in 1 : 10 solution of biochar to water recorded. N, C, H, O concentration were estimated by elementary analyzer. Cation exchange capacity of sugarcane bagasse made biochar was measured by ammonium acetate method. Moreover its functional group determined by FT-IR method. Specific surface area estimated as per Branuar Emmet Teller (BET) method. Sugarcane bagasse made biochar image was obtained from scanning electron microscope. Cadmium and lead concentration in root and shoots were estimated by atomic absorption spectrometer after wet digestion. SAS software was used for statistical analysis data which fallowed by Duncan test to compare the mean values.
Results and discussion: The results showed that implementation of cadmium and lead led to decrease in chlorophyll index, leaf area, height of plant and root and shoot dry weight significantly. But the sharp decline in the concentration of cadmium and lead in root and shoot after sugarcane bagasse made biochar application improved chlorophyll index, leaf area, height of plant, root and shoot dry weight. Application of 4% Sugarcane bagasse made biochar, decreased transfer factor (TF) and bioaccumulation factor (BF) of these elements compared to control. The results showed high capability of sugarcane bagasse made biochar to absorb cadmuim and lead and reduce their availability to plant respectively. In fact application of sugarcane bagasse made biochar dwindled cadmium and lead absorption as well as their transfer factor and bioaccumulation factor, and hence improved plant growth.
Conclusion: The results obtained after sugarcane bagasse made biochar application mainly initiated due to high cation exchange capacity of which eventually was created by large number of functional groups in its high specific surface area (table 2) to stabilize cadmium and lead and render them unavailable to plant and hence improve its growth.
