فهرست مطالب آرزو خلیجیان

The study of sediments as one of the reservoirs for absorbing environmental pollutants and especially heavy metals is of particular importance. Therefore, this research was conducted with the aim of identifying and evaluating the contamination of arsenic, cadmium, nickel, and vanadium elements in the sediments of Farahabad coast of the Caspian Sea in 2018. In this study, after collecting 36 sediment samples from 12 selected stations, the values ​​of pH, EC, organic matter, and texture of sediments were determined. The concentrations of elements were determined by inductively coupled plasma optical spectroscopy. In addition, in order to evaluate the pollution of sediments, environmental toxicology criteria were calculated, including indicators of pollution coefficient, enrichment, and pollution load. In order to identify the potential sources of elements and their grouping in the sediment samples, multivariate statistical methods were used, namely principal component analysis and hierarchical clustering. For statistical processing of the results, one-way analysis of variance, one-sample t-test, and Pearson's correlation coefficient were used in the SPSS software. The average concentration of arsenic, cadmium, nickel, and vanadium was 12.7, 0.191, 35.0, and 31.9 mg/kg, respectively. The output results of PCA, HCA models, EF index values, ​​and coefficient of variation, as well as Pearson's correlation matrix, showed that arsenic probably originates from man-made sources and cadmium, nickel, and vanadium elements have natural sources.

Soils and sediments contamination with trace and toxic elements lead to potential ecological risk and adverse effects on human health and so have been the cause of increasing concern worldwide. Therefore, this study was carried out to potential ecological risk assessment of As, Cd, Ni and V in surface sediments of Khazar Abad, southern parts of Caspian Sea in 2019.

In this descriptive cross-sectional study, a total of 36 surface sediment samples were collected from 12 sampling sites. After samples preparation, the elemental contents were determined using ICP-OES. Also, potential ecological risk factor (Eir) and cumulative potential ecological risk index (RI) were calculated. All statistical analyses were performed by SPSS software.

Based on the results obtained, the mean contents of As, Cd, Ni and V in analyzed samples were found to be 12.7, 0.191, 35.0, and 31.9 mg/kg, respectively. The computed values of Eir  showed that factor values were decreased in the order Cd > As > Ni > V. Additionally, the mean values of RI with 53.7 indicated that all the examined elements have the "low potential ecological risk".

Accordingly, although the examined elements have shown a low potential ecological risk, cadmium with 46.4% and arsenic with 45.4% mean values of RI can cause for concern. Therefore, source identification and management of organic and inorganic pollutants and also periodic monitoring of water and sediments as the sink of environmental pollution are recommended.

Increasing population growth¡ and therefore¡ increasing requirements for development of the agricultural productions¡ lead to be overused the pesticides. So¡ their residues in environment¡ particularly surface and groundwater resources¡ create human health risks. Therefore due to the serious risk to human health¡ this study was carried out for assessing the diazinon residues in groundwater samples of Hamedan-Bahar Plain in 2014.
Material and Water samples were collected from 20 stations along the Hamedan-Bahar Plain in summer 2014. After preparation and processing the samples in the laboratory according to liquid phase extraction¡ diazinon residues in samples were determined using a spectrophotometric method in three replications. All statistical analyses were performed by SPSS 20 software using Kolmogrov-Smirnov¡ one-way ANOVA¡ One Sample T Test and Pearson''s Correlation Coefficient.
The results showed that the mean concentration of diazinon residues in samples was 0.23±0.06 µg/mL-1¡ being upper than the Maximum Contaminant Levels (MCLs) provided by the WHO.
Since based on WHO guideline the mean concentrations of diazinon residues in groundwater resources of Hamedan-Bahar Plain were upper than MCLs¡ therefore; exploitation of water for drinking has adverse effect on consumers'' health. In this regards¡ concerning increased use of agricultural inputs especially pesticides¡ regular periodic monitoring of chemical pollutants content in groundwater resources of study area is recommended.