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Introduction: Rivers are considered as a vital resource for mankind from the past to the present day.Considering the ever-increasing population, industrial developments and the expansion of modern urban societies, it is expected that the rivers located near densely populated urban and rural areas to be in danger of destruction due to a large part of urban, rural, domestic, industrial and agricultural pollutants to the sources of surface and groundwater in the riparian and riverside more than any other water ecosystems. On the other hand, regarding Iran's arid and semi-arid climate, the use of sediment qualitative indicators in research and investigation is crucial in order to predict, evaluate and provide a sustainable solution for controlling the amount of pollutants and also improving the quality of river water. The Karaj River is one of the main freshwater and energy production resources in the region, which plays a vital part in creating an ecological balance in parameters affecting the quality of this water ecosystem. The purpose of this research is to measure the concentration of heavy metals in the sediments of the river bed and to evaluate and analyze it using Geoaccumulation index and Enrichment Factor, which led to the suggested solutions in order to avert and control the further spreading of pollution.Material and Methods: In this research, nine stations were selected based on the land use of the area. The sediments of the river bed in each station were sampled. Sediment samples were prepared and later transferred to the laboratory and the total concentration of heavy metals was measured by Inductively Coupled Plasma Mass Spectroscopy (ICP) device.Results and Discussion: The results obtained from the measurements using the mentioned indices assessed that the level of heavy element pollution is relatively low in the Karaj River. Nevertheless, part of this slight pollution is related to human activities such as road construction, tourism and the leakage of local runoff and sewage into the river and its riparian zone, which led to the increase of the Geoaccumulation of elements including copper and chromium to the numbers of 1.01 and 1.96 in downstream stations P8 and P9, respectively. Also, the highest average amount of Geoaccumulation for copper in 9 sampling stations was 0.23. On the other hand, these anthropogenic activities have significantly increased the arsenic Enrichment up to 17.81 in station P4 and the average Enrichment Factor of Arsenic in 9 sampling stations up to 13.12. But since each heavy element has its own unique nature, part of the quantity of the pollution present in the sedimentary environment of the river is related to natural factors, geology, soil erosion and weathering of riverbed rocks.Conclusion: The process of changes in the amount and distribution of elements in the sediments were compared and the factors affecting their alignment or mismatch were discussed and researched. Generally, the results of this research show that the Karaj River, taking into account the Geoaccumulation index and Enrichment Factor, has negligible contamination of heavy metals in the riverbed sediment. However, the trend of index changes along the river route shows the direct effects of destructive human activities in the region.

Background and Objective: It is of utmost importance to analyze the causes of accidents to control and prevent their recurrences.This study aimed at analyzing the causes of amputation-leading accidents in a dam construction project using a Tripod beta and SCAT Combined Method. Materials and Methods: This study analyzed the data related to amputation-leading accidents using a Tripod beta and SCAT Combined Method. Initially, the interface and root causes were obtained by the Tripod beta Method and were subsequently placed in SCAT cause and effect table along with the suggested control provisions. In addition, the data were collected using questionnaires, and the effect of the causes of accidents and their ranks were evaluated using the Chi-Square and Friedman tests, respectively. Accordingly, appropriate control measures and necessary suggestions were provided in this study. Results: According to the results, the underlying causes were classified into 6 categories. Maintenance management (25%) and training (20%) obtained the first and second ranks. On the other hand, the executive instructions (5%) obtained the lowest rank. Moreover, 13 preconditions were determined in this study. The most important indirect and root causes were "inappropriate machine lifting (rank: 2.69)" and "the erosion and excessive deterioration of the mechanical excavator (rank: 4.55)", respectively. Furthermore, the most important control measure was "the inspection and control of the operation (the mean rank: 5.05)". There was also a significant relationship between indirect and root causes. A P-value less than 0.001 was considered statistically significant. Conclusion: The combined method presented in this study has met the needs of different organizations in many cases and is currently one of the most important methods to analyze the accident causes. Therefore, it is suggested to combine the SCAT with other methods to analyze the causes of accidents in dam and construction projects.