جستجوی مقالات مرتبط با کلیدواژه « speciation » در نشریات گروه « زمین شناسی »

The present study aims to investigate the speciation, bioaccessibility, and health risk of Pb in the soils around the Irankuh mine. For this purpose, 20 soil samples were collected and the physicochemical parameters of the samples were determined. The total and bioaccessible concentrations of Pb were determined using the total digestion and in vitro methods, respectively. The speciation of Pb in selected soil samples was investigated using a sequential extraction approach. The values of pH, organic matter, carbonate and cation exchange capacity of the studied soil samples vary between 6.7 to 8.2, 0.2 to 4.8 %, 6 to 48.5%, and 18 to 11.2 meq/100 g, respectively. The total concentration of Pb changes between 18.4 and 2869 mg/kg (average value of 273.4 mg/kg). Pb is dominantly present in reducible fraction, confirming the anthropogenic source of Pb and its potential mobility. Based on the in vitro test results, the bioaccessibility of Pb is very variable (between 0.2 to 45.4% of the total concentration), which is due to the difference in the physico-chemical characteristics of the samples and the source of the element. The hazard coefficient values for ingestion, dermal contact and inhalation routes are higher for children than adults, and for the ingestion route than other exposure pathways. The carcinogenic risk (CR) values indicate that there is no risk through dermal contact and inhalation routes; however, CR values for the ingestion route using both bioavailable and total concentrations confirm the probability of cancer risks for residents living near the mining site.

This study aims to investigate the content, geochemical speciation and mobility of heavy metals as well as mineralogical characteristics of wastes in a coal washing plant (Alborz-e-Sharghi Company). The obtained results revealed that coal wastes as compared to world coal mean are normal to enriched in terms of Pb, Cu, Ni, Cr and As while are depleted with respect to Cd and Zn. XRD analysis indicated that quartz, kaolinite, illite, calcite, calcite, siderite, gypsum and pyrite are present in the studied samples. The results obtained from speciation analysis showed that Pb, As, Cu, Ni and Cr were mainly associated with phases 6 and 5 (sulfide and silicate bound fractions) while Zn and Cd were mostly retrieved from phase 1 (water soluble fraction). The mobility factors also confirms that Zn and Cd with 53.32 and 44.12 % are the most mobilizable elements. This is particularly prominent for 30 years aged coal wastes. This study generally concludes that most mobilized metals such as Zn and Cd have the high potential to find their ways into the surrounding environments and this should be considered in future assessments and management of coal waste produced in the study area.

Heavy metal concentration and speciation in soils and native plants around the Ijo copper mine (Kerman province) are investigated in the present study. For this purpose, 34 soil samples (0-40 cm in depth) and 8 native plants (Artemisia sp.) are collected and analyzed by means of standard methods. In addition, chemical forms of heavy metals are determined by Tessier five-stage extraction procedure. The results obtained indicated that Cu (457.25 mg/kg on average) in potassic alteration zone and As, Pb and Zn in argillic (47.06, 137 and 580 mg/kg on average, respectively) have the highest concentrations. The calculated enrichment factor (EF) and geo accumulation indices (Igeo) also confirmed this distribution pattern. The results of sequential extraction method indicated that all the metal studied have relatively low proportion in the exchangeable fraction (F1, 1/89 % of their total contents) and high contribution in the residual fraction (79/70 % of total contents) implicating their main geogenic sources in the soils. Levels of heavy metal in Artemisia and based upon the calculated biogeochemical indices (Transfer factor-TF and Bioconcentration factor-BCF), it was revealed that Zn and Cr (Mn as well) have the highest and lowest transfer factors, respectively. Also, the highest BCF are calculated for Mo, Cd and Cu. This study generally concludes that although the metals in soils are inherited mainly from the natural or lithogenic source in the study area, intensive exploitation and mining activities might enhance the soil metal contamination rate and make metals more available that it should be considered in future assessments.

The main objective of the present study is to evaluate variation, contamination and speciation of heavy metals in bed sediments of the Siahrood River in Mazandaran Province. For this purpose, fifteen sediment samples were collected along the main channel of the river. In addition to total content of heavy metals and selected physiochemical properties of the sediments, geochemical species of heavy metals were determined operationally using the modified BCR method. The obtained results generally showed that there is a wide variation in heavy metal concentrations in the sediments, probably due to anthropogenic inputs into the river and effect of physicochemical properties of the sediments (organic matter and clay content) on the heavy metals variability. The calculated Igeo (Geo-accumulation index) for each metal also revealed that sediments are moderately or strongly contaminated in terms of Pb and Cd whereas not or slightly contaminated with respect to other heavy metals, suggesting an anthropogenic source for Pb and Cd and a mostly geogenic origin for Ni, Zn, and Cr (Arsenic is probably of a mixed source). The results of BCR method indicated that Pb and Cd are predominately incorporated into the first fraction (F1, acid-soluble fraction) while Zn and Ni are mainly associated with residual fraction (F4) confirming the concluded remarks on discrimination of heavy metals origins in the sediments.