Showing 6 results for Tracer
K. Nosrati, H. Ahmadi, F. Sharifi,
Volume 16, Issue 60 (7-2012)
Abstract
Sediment sources fingerprinting is needed as an autonomous tool for erosion prediction, validation of soil erosion models, monitoring of sediment budget and consequently for selecting soil conservation practices and sediment control methods at the catchment scale. Apportioning of eroded-soil into multiple sources using natural tracers is an integrated approach in soil erosion and sediment studies. The objectives of this study, as a first work, are to assess spatial variations of biochemical tracers and theirs validation in discriminating sediment sources under different land uses and water erosions at catchment scale and to apply them as fingerprints to determine relative contributions of sediment sources in Zidasht catchment, Iran. In view of this, 4 enzyme activities as biochemical tracers were measured in 42 different sampling sites from four sediment sources and 14 sediment samples. The results of discriminant function analysis (DFA) provided an optimum composite of two tracers, i.e. urease and dehydrogenase that afforded more than 92% correct assignations in discriminating between the sediment sources in the study area. Sediment source fingerprinting model was used based on optimum composite of two tracers resulting from DFA to explore the contributions of sediment from the four sources. The results showed that the relative contributions from rangeland/surface erosion, crop field/surface erosion, stream bank and dry-land farming/surface erosion sources were 11.3±5.3, 8.1±3.8, 75±8.5 and 3.6±2.5, respectively. Therefore, we can conclude that fingerprinting using biochemical tracers may help develop sediment fingerprinting models and as a first step facilitate a more complete tool for fingerprinting approach in the future.
G. Yousefi, A. Safadoust, M. Mosaddeghi, A. Mahboubi,
Volume 17, Issue 65 (12-2013)
Abstract
This study was conducted to assess the long-term effects of soil texture and crop management on transport of lithium (Li+) and bromide (Br-) under unsaturated flow conditions. Treatments were two different soil textures of clay loam and sandy loam to be cropped with either wheat or alfalfa for 4 years. Undisturbed soil columns were taken for the steady-state flow condition using tap water prior to applying a pulse of 0.005 M (C0) LiBr solution as the influent. Four pore volumes (4PV) leaching for each column was obtained. Bromide and lithium concentrations of the effluent (C) were measured in 0.2PV intervals using bromide selective electrode and flame photometer, respectively. Relative concentrations (C/C0) of Br- and Li+ in the effluent were drawn vs. pore volumes. The results showed that the effluent concentrations were significantly affected by crop type and soil texture (in combination by soil structure). The breakthrough curves illustrated the early appearance of Br- in the effluent due to anion repulsion and retarded movement of Li+ because of surface adsorption through the soil columns. Both Br- and Li+ concentrations decreased with time and converged at low levels justifying the minor effect of macropores on continuation of leaching and final transport via soil matrix. The Br- and Li+ concentrations were higher in the effluent of clay loam soil under alfalfa due to higher structural stability compared with sandy loam soil under the same crop. It was also shown that in both soil textures the concentrations of Br- and Li+ appeared to be higher under alfalfa than under wheat, indicating the importance of crop management in contaminant transport compared with soil texture. The trends of breakthrough curves of Li+ were similar to Br- with lower concentration in effluent as a result of its adsorbtion on active surfaces.
S. S. Okhravi, S. S. Eslamian, N. Fathianpour, M. Heidarpour,
Volume 19, Issue 74 (1-2016)
Abstract
In addition to kinematic description of biological reaction, flow pattern plays an important role in designing constructed wetlands. This study investigates the effects of flow distribution on constructed sub-surface horizontal flow wetland with a length of 26 m, width of 4 m and 1% bed slope in order to understand internal hydraulic functioning patterns. Inlet configuration is selected as a variable parameter. Three different cases of inlet and outlet configurations were 1) midpoint, 2) corner, and 3) uniform. Outlet has been fixed in all configurations. Uranine tracer was used to determine the influences of flow distribution by drawing hydraulic retention time curve in different cases. Results showed that mean residence times for each configuration were equal to 4.53, 3.24 and 4.65 days, respectively. Retention time distribution curve provided conditions, not only for showing dispersion patterns throughout system but also for interpreting hydraulic parameters like hydraulic efficiency and effective volume. According to the retention time curve, effective volume was 87.5% in configurations 1 and 3, and 62.1% in configuration 2 following numerous short-circuiting ratios. Finally, the best configuration of inlet-outlet layout to improve the performance of effluent treatment and use the geometry effectively was found to be the uniform-midpoint based on physical experiments followed by midpoint–midpoint as the second best.
M. Zarea Khormizi, A. Kavian, K. Soleimani, K. Nosrati,
Volume 21, Issue 2 (8-2017)
Abstract
Obtaining information about relative importance of sediment sources and their contributions on sediment production and thus identification of on-site critical areas is required for implementing soil and water conservations and sediment control programs. For this reason, in this study 35 geochemical tracers and organic carbon were measured in 45 samples of sediment sources and in 11 watershed sediment samples to determine the sediment deposit contribution of each land use as sediment resources in Kond watershed of Tehran province. Based on the results of Kruskal-Wallis test, from among 35 measured traces, 10 tracers including Al, As, Be, Ca, Mo, P, Pb, S, Zn and OC had ability to discriminate sediment sources with less than 1% confidence level. Then, 5 tracers: OC, S, P, Zn and As were selected as optimum composite using Discriminant Function Analysis (DFA) with 0.000 confidence coefficient that had distinguishing capability of sediment sources by 97.8% correct assignation. Finally, the results of multivariate mixing model showed that contribution means of orchard, range and residential were 1.54, 14.27 and 84.18% in sediment production, respectively. Also, the sum of squares of the error was 0.33. The results of this study can be used in selecting an appropriate method for sediment control in studied area.
A. Safadoust, S. Ghanizadeh, M. Nael,
Volume 26, Issue 1 (5-2022)
Abstract
This study was conducted to investigate the effects of vegetation type (Alfalfa and Wheat) and slope (5% and 20%) on runoff and drainage pollution in clay loam soil. Sampled soils were repacked in the box with one soil drainage outlet and one surface flow outlet and were cultivated by wheat or alfalfa. A solution containing 0.05 M KCl was poured quickly and uniformly, over the surface of each box, after plant growth. Simulated rainfall was applied to the soil box with the intensity of a constant rate of 64 mm h-1 for 2 hours immediately. Then the concentration of Cl- and K+ were measured in the collected samples of runoff and the drainage outlet. Results showed that the measured concentration of K+ was lower than the Cl- concentration as a result of its absorbable property. The breakthrough curves (BTCs) of Cl- and K+ showed that slope and vegetation type affected the transport of Cl- and K+. The peak of the BTCs for Cl- and K+ in runoff ranked in the order of wheat and 20% slope> alfalfa and 20% slope> wheat and 5% slope> alfalfa and 5% slope, and in the drainage changed to alfalfa and 5% slope> wheat and 5% slope> alfalfa and 20% slope> wheat and 20% slope. For each slope, the intensive vegetation cover of alfalfa than wheat considerably reduces Cl- or K+ pollution in runoff; whereas drainage development of larger and deeper root systems was the cause of higher leached concentrations for both tracers. Based on our research changes in soil surface vegetation cover from wheat to alfalfa are suggested in slope land to prevent surface water pollution; although other factors such as the climate, soil texture, and structure should also be considered.
D. Khatibi Roudbarsara, A. Khaledi Darvishan, J. Alavi,
Volume 27, Issue 2 (9-2023)
Abstract
Soil erosion followed by sediment production is the most important phenomenon that causes soil and environment degradation in many areas and is increasing. Sediment fingerprinting is a method to identify sediment sources and determine the contribution of each source to sediment production. The present research was carried out to evaluate the relative erosion sensitivity of lithological units and to determine the contribution of each unit in bed sediment production using geochemical properties in the Vaz River located in Mazandaran province. The 33 soil samples were taken from the whole watershed and one sediment sample at the outlet of the watershed. Then, five tracers of B, Al, Sc, Mo, and Sn were selected as the optimal combination using three statistical tests range tests, Kruskal-Wallis, and discriminant function analysis. Finally, using optimal tracers and a combined multivariate model, the contribution of lithological units with very high (A), high (B), medium to high (C), and medium (D) sensitivity in bed sediment production were obtained using FingerPro statistical package and R software. The results showed that the contribution of lithological units with very high (A), high (B), medium to high (C), and medium (D) sensitivity in bed sediment production were 24.23, 50.77, 15.62, and 9.36%, respectively. Then, the specific contribution of each sensitivity class was also calculated to remove the effect of area on the results. The Qal lithological unit including the Quaternary sediments in the river bed and banks with very high sensitivity to erosion (A) and a specific contribution of 0.0807 % per hectare had the maximum contribution in bed sediment production in Vaz River.
