Flocculation of Cu, Mn, Ni, Pb, and Zn during estuarine mixing [Caspian Sea]

During estuarine mixing of fresh water with saline water and due to the flocculation process, a portion of dissolved metals come into particulate phase, and the dissolved load decreases. This process plays an important role in self-purification of heavy metals in rivers. In this study, flocculation of Cu, Mn, Ni, Pb and Zn during mixing of Cheshme-Kileh River water with Caspian Sea water has been investigated. Salinity and electrical conductivity are the governing factors for the flocculation of Mn and Cu. Zn and Ni are governed by pH. Dissolved oxygen is a governing factor for the flocculation of Pb. Rapid flocculation occurs in the earlier stages of mixing. The final flocculation rates of metals are in the following order: Mn [68.79%] > Pb [45.45%] > Ni [26.32%] > Cu [23.08%] > Zn [21.21%]. In addition, electro-flocculation [EF] is investigated. The results reveal that EF had adverse effect on flocculation rates of heavy metals. General pattern of EF of metals is like the following: Mn [57.89%] > Pb [40.9%] > Cu [23.08% > Ni [22.37%] > Zn [15.15%]. Furthermore, the effect of decreasing pH level on flocculation of heavy metals is studied. Except for Mn, decreasing the pH increased the flocculation rates of heavy metals. Maximum flocculation of Ni, Cu, Pb, and Zn occur at pH about 7.5. Due to the flocculation of trace metals during the estuarine mixing about 51.6, 7.8, 5.5, 3.9, and 3.6 ton/year of Mn, Ni, Zn, Pb, and Cu, respectively, are removed from the river water

Association of trace metals with various sedimentary phases in dam reservoirs

In the present study sediment and water samples collected from Kowsar Dam reservoir in Kohkiluye and Boyerahmad Province, southwest of Iran, are subjected to bulk digestion and chemical partitioning. The concentrations of nickel, lead, zinc, copper, cobalt, cadmium, manganese and iron in water and bed sediment were determined by atomic absorption spectrometry. The concentrations of metals bounded to five sedimentary phases were estimated. On this basis, the proportions of natural and anthropogenic elements were calculated.The anthropogenic portion of elements are as follows: zinc [96%]> cobalt [88%]> iron [78%]> magnesium [78%]> nickel [78%]> copper [66%]> lead [63%]> cadmium [59%]. The results show sediment contamination by nickel, cadmium and lead, according to the world aquatic sediments and mean earth crust values. Manganese and copper have strong association with organic matter and are of high portion of sulfide bounded ions. Finally, The degree of sediment contamination was evaluated using enrichment factor, geo-accumulation index [Igeo] and pollution index [IPoll]. The sediments were identified to be of high cadmium and lead pollution index. The pattern of pollution intensity according to enrichment factor is as follows; manganese [1.25] < copper [1.63] < zinc [1.93] < cobalt [2.35] < nickel [3.83] < lead [12.63] < cadmium [78.32]. Cluster analysis was performed in order to assess heavy metal interactions between water and sediment. Accordingly, nickel, cadmium and copper are earth originated. Zinc, copper and manganese are dominated by pH. All the elemental concentrations in water and sediment are correlated except for sedimental copper

3D open channel flow modeling by applying 1D adjustment

A three-dimensional [3D] finite volume model with a novel adjustment scheme was developed to solve shallow water equations in open channels. An explicit finite volume method was used to discretize the governing equations in a boundary-fitted structured and collocated grid system. Because a simple second-order central scheme was used for spatial discretization and due to the occurrence of high Peclet numbers in open channel flows, some treatments were needed to reduce oscillation. Thus, a special adjustment scheme designed to minimize differences in the averaged free surface elevation and flow discharge in a 3D model and 1D flow data was applied to some cross-sections. The model was applied to simulate shallow water flow in a backward-facing step, a meandering channel with 90 [degree sign] bends and 180 [degree sign] bend channel. A comparison of the model results with available experimental and numerical data illustrated that the proposed numerical procedure decreases the numerical oscillations and increases the stability of the 3D numerical model in open channel flow modeling

Determination of air pollution monitoring stations

Swelling urban populations and increasing number of industry and especially automobiles in and around cities have resulted in adverse effect on human health. One of the most important things regarding air pollution in these days is that the number of motor vehicles has increased, and the resulting problems of new types of air pollution on large scale need to be emphasized in large cities. The groundwork for this study is based on collecte d data, specific studies regarding to use passive tube sampling techniques and geo-statistic mapping tools. The low cost and easy operation of the diffusive sampling technique makes it an ideal tool for large scale air pollution surveys with a high spatial resolution. Finally, we used Kriging method to draw air pollutions maps related to NO2 and SO2 measurements in Shiraz city. These maps conducted us to find number of air pollution monitoring stations. Results show that we need 2 traffic, 3 urban, 1 suburban and 1 industrial station in Shiraz area. In fact, the proposed method in this study provides a useful tool that can be easily applied to other polluted cities. Meanwhile, it would become effective as well as the actual time required to implement them

effect of using patency file on apical transportation in canals prepared with passive step back technique

Background: the purpose of this study was to assess the effect of patency file on apical transportation in curved canals prepared with passive step back [P.S.B] technique

Methods: this is an interceptive experimental, Invitro, study. Human extracted first permanent molars with 19-23mm length and curvature of 15-35 degrees [Schneider method] were considered for use in this study. Simple sampling was done and 35 teeth for each group was selected. In experimental group A canal preparation was done with P.S.B technique and usage of a # 10 file [as Patency file] between successive files. In experimental group B preparation was done in the same way except for usage of patency file. Pre and post-operative radiographs were taken with similar condition. Radiographs were scanned and changes in canal curvature was determined using four different methods [Schneider, Weine, Long - Axis techniques [L. A.T], and Digital image overlay technique [overlay. T]], using Idrisi for windows and AutoCAD softwares

Results: the mean of canal transportation angle in experimental group A with Schneider, Weine, LAT, and Over Lay techniques was: 7.006 +/- 3.478, 12. 285 +/- 6.032, 4.376 +/- 3.516, 3.147 +/- 2.744 respectively. Mean of canal transportation angle in experimental group B with the same methods was also determined: 8.009 +/- 4.178, 13.55 +/- 7.602, 9.464 +/- 5.384, and 9.641 +/- 5.382 respectively. T- test statistical analysis shows that there are no significant differences between the mean of canal transportation angles in two groups as measured by Schneider and Weine method [P>0.05]. Mann- Whitney test shows that there are statistically significant differences between two groups as measured by LAT and Over Lay techniques [P<0.001]

Conclusions: results of this study shows that patency file in conjunction with P.S.B techniques causes significant reduction in apical transportation angle. Shortcomings of Schneider method in determination of canal curvature and specially assessment of apical transportation after instrumentation is mentioned in several studies. Our study shows that both Schneider and Weine techniques are not reliable methods for transportation assessment when compared with Image Over Lay technique. The result of LAT Shows close proximity with Over Lay technique and can be used for evaluation of apical transportation as a simple and reliable technique