جستجوی مقالات مرتبط با کلیدواژه « ژئوشیمی » در نشریات گروه « محیط زیست »

Distribution of heavy metals in rock units and their pollutants are necessary environmental issues which have high importance.

Because of not performed environmental geochemical studies of heavy metals in Iran based on chemostratigraphic studies, for this purpose, this study on chemofacies of Gachsaran formation in Kermanshah with the aim of assessing environmental heavy metal pollution was carried out. For determine the concentrations of heavy metals, XRF and ICP mass techniques were used and the amount of metal contamination was investigated using statistical softwares and pollution indices.

The results indicated high concentration of cadmium in sediments of Gachsaran Formation (3.3) ppm which is higher than (0.3) ppm in crust. All three used indices (Igeo, EF ANF CF) showed cadmium contamination in studied sediments but molybdenum, aluminum, cobalt and iron did not showpollution in sediments. Furthermore the values of CF and EF indices showed a similar trend about element contamination in sediments.

Significant amounts of cadmium in the Gachsaran Formation can be further affected by the dissolution process of rocks and sediments by surface and groundwater, as well as by biological (agricultural and mining) activities and can has non optimal environmental impacts. Therefore, it is necessary to anticipate and make the necessary arrangements in this case. High levels of cadmium in the sequences of the Gachsaran Formation can effected by dissolution, as well as biological activities (agriculture and mining).

The case study of present project is located in northeast of Qazvin sheet 1:100000 and south of Javaherdeh 1:100000 sheet, in the Hir region. The present study aims to geochemically explorethe Hir region in scale of 1:25000 using stream sediments and heavy minerals exploration method. for this purpose, all data and information of the case study were collected and then, the proper data such as geological map, topography, alteration map, airborne geophysical map and satellite image of digital elevation model, sampling network of the best potential streams as well as heavy mines from potential areas, such as contacts and adjacent intrusions and alterations, was prepared. Then, sampling was carried out and the specimens were transferred to the laboratory for the element analysis. After data analysis, an analysis was performed on them and the errors were resolved by removing the censored data and then, they were normalized by statistical method. Then, the data were statistically analyzed in order to find the areas with mineral potential.

Heavy metals can be present at low concentrations in the soil and contaminate it. Since the study area is ophiolite in terms of lithology, it can increase the concentration of heavy metals in soil and water resources. In this study, the concentration of heavy metals has been investigated and the pollution in sediments of Almejogh region (Fariman ophiolite) is evaluation. To study the concentration of heavy metals and sediment pollution in the study area, 9 samples of sediment were taken from depth of 30 to 20 cm. The samples were transferred the environmental laboratories of Islamic Azad University of Mashhad and the amounts of pH and EC in soil were measured. 10 grams of soil (material passing through a 200-mesh sieve) was transferred to the ACME Laboratories of Canada in order to be analyzed for determining the amount of heavy metals by the induction plasma-mass spectrometry (ICP-OES) method. Study of the correlation of heavy metals by Pearson coefficient, cluster analysis and principal components analysis showed that there are two different origins for geochemical distribution of heavy metals in sediment of the region. Ophiolite set of distribution of Cobalt, Nickel, Chromium and Pyroclastic and volcanic set as well as distribution of Iron elements, Molybdenum, Vanadium, Copper, Arsenic, Lead, Potassium and Cadmium were controlled. The pH of the soil in the study area fell within the pretty alkaline limit based on the classification of American soil science society. Evaluation of enrichment factor showed that Nickel has a very high enrichment and Arsenic and Chromium were in a high enrichment region. The above enrichment is indicative of anthropogenic origin. The pollution coefficient also showed that Nickel has the highest pollution in the region. The index of accumulation (of earth) also indicates t contamination of the sediment with Nickel in the region.

Iodine is an essential micronutrient for human health, hence iodine deficiency causes various damages such as thyroid disorders. Climate and geological settings are the causes of the incidence and prevalence of the mentioned disorder. A bibliographic survey showed that no studies have been undertaken so far in this area with regard to geological setting, so in this research we focused on geological reason(s) with investigation on soil and water. In response to reports on the high incidence of iodine disorders in Dehdasht area, 16 ground water samples were taken from agricultural wells, drinking water and springs in the area to analyze anions, cations and iodine. The results showed that iodine levels were high in some water samples. To study the effect of soil on iodine, 20 soil samples were taken from various formations and pH, iodine as well as organic matter were measured. iodine can exist in several species. In different environments, the mobility of iodine depends on the type of iodine.The results showed that due to the presence of calcareous formations, high pH and calcium can lead to low mobility of iodine Also the alkaline and reduction conditions, can cause high mobility and enrichment of iodine in groundwater.

The objective of this study was to assess the extent and severity of heavy metal contamination in surface soils in the surrounding of the industrial town of Ahvaz 2. Sixteen topsoil samples were collected at 0-5 cm depth and were analyzed by ICP-OES for Co. Cr, Cu, Ni, Pb and Zn. One sample was also investigated for mineralogy using X-ray. The abundance of heavy metals measured in these topsoil decreases as follows: Cr>Ni>Zn>Pb>Cu>Co. The minerals in the analyzed sample are composed of quartz, calcite, and halite as major minerals with dolomite and alunite as minor minerals. Results indicate that concentration of heavy metal in surface soil is due to fine grain texture of soil, clay content, alkaline pH, CaCO3 content, Na+ and aluminum oxide content. According to geochemical criteria such as enrichment factor (EF), index of geo-accumulation (Igeo) and pollution index (PI), the soils of the study area are considered to be moderately contaminated with respect to Cr, Ni and Pb, and uncontaminated with respect to Co, Cu and Zn. The calculated results of EF, Igeo and PI of heavy metals are as the following: Ni>Pb>Cr>Zn>Cu>Co.

Anzali wetland in north of Guilan provience is an international important wetland that is recorded in Ramsar convension. Pollution is one of the major problems facing this wetland. In order to investigate the pollution situation, sediment core samples were taken in 7 stations in 4 districts within the wetland, namely Abkenar, Siakishom, Hendekhale and Shijan). Elements were determined in 0,5 10, 20 and 50 cm depths in each core. Major elements including Al, Ca, Fe, K, Mg, Na, Mn, P, Ti and trace element such as Li, Ba, S, Sr, As, Cd, Cr, Co, Cu, Mo, Ni, Pb, V, Zn, Bi concentrations were determained using ICP-MS. Temporal variability showed that most of the heavy metals decreased in concentartions from surface to depth. The statistical correlations among elemental pairs were performed by Pearson correlation. In Abkenar part of the wetland except Cr, Ni, Zn and Co, other heavy metals have anthropogenic source. Elemets such as Bi, Zn, V, and Pb in Siakishom part, Cu and Ni in Hendekhale, V, Cr and Co In the Shijan part have natural source. When comparing heavy metal concentrations in wetland sediments with Caspian Sea sediments and river sediments, it is apparent that the concentrations of heavy metals in wetland sediments are higher. Furthermore, considering the EF (Enrichment Factor) using Al normalization as the best method, the elements such as Zn, in all parts and Pb, Bi, Cd and Ni in most of wetland have low enrichment.

Sediment core samples can provide useful information about aquatic environment. Sedimentation rate, climate changes and heavy metal concentration are among the most important studies that are carried out on sediment cores. In this study, a sediment core of 70cm with aim of metal concentration investigation is collected from central part of the Zarivar lake in the vicinity of the Marivan city in Kurdistan province. After sub sectioning the bulk concentration of metals was obtained using HF- HCl- HNO3. The share of lithogenous and anthropogenic concentration of metals was brought out by chemical partitioning technique. The results of chemical partitioning studies revealed that a considerable part of metals are present in anthropogenic fraction as follows Pb (76.2%)>Mn(53.3%)>Co(50.6%)>Cu(47.4%)>Zn(27.5%)>Ni(18%)>Fe(7.9%) Results of the present investigation showed that statistical studies such as cluster analysis are not sufficient to identify existence of pollution. The results of chemical partitioning studies indicate that Zarivar lake is polluted but cluster analysis illustrates an unpolluted environment. Except for Cu, a significant portion of other metals are present as loosely bonded ions that can be easily released into the overlying waters due to slight changes in physico-chemical characteristics of water column. Presence of small amount of Fe and Mn as sulfides is indicative of prevailing redox conditions over the anoxic ones. Based on the obtained data, the existing condition of Zarivar lake in terms of contamination is not suitable and with increasing of red ox condition, the possibility of increase in contamination is probable