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Microplastic (MPs) pollution in the aquatic and terrestrial environments has caught many attentions in the scientific literatures. Currently, no information is available about MPs pollution in Caspian Sea, the largest lake in the world. This study indicates the first report on the MPs pollution in the sediments of the southern Caspian coastal zones, northern Iran. Density separation method was conducted on 17 surficial sediments. The combination of observation techniques including SEM-EDS analysis, polarized light microscopy and Raman micro-spectroscopy were used to identify MPs. The abundance and size of microplastics in the samples ranged between 25 and 330 items/kg and 250-500 μm, respectively. Fibers constituted the most common MPs shape and polystyrene (PS) and polyethylene (PE) were major polymer types in the samples. The distribution of MPs in the study area reflected a patchy and irregular spatial pattern implying that the higher MPs concentration are near mouth of permanent rivers and in the regions with higher level of the fishing and tourism activities. The results showed the wide occurrence of MPs in the sediments of the world's largest lake which extend the knowledge on MPs pollution in the marine system. We also recommend further research on microplastics in different compartments of Caspian Sea to inform policy discussions and the development of appropriate management responses., Competing Interests: Declaration of competing interest The authors have no conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Magnetically N-doped Carbon quantum dots has been synthesized via a simple chemical method and applied as a sorbent for the preconcentration and extraction of trace amounts of Pb 2+ from water and vegetable samples followed by flame atomic absorption spectrometric detection. The nanoparticles were characterized by X-ray diffraction, UV-vis spectra, Fourier transform infrared spectroscopy, vibrating sample magnetometer analysis and transmission electron microscopy. A central-composite design was used to find the optimum conditions for the preconcentration procedure through response surface methodology. The effects of various parameters such as the pH value, adsorption time, amount of adsorbent, desorption conditions (type, concentration and volume of the eluent and desorption time), sample volume and interfering ions have been studied. Under the optimized conditions, the calibration graph was linear in the range of 0.3-300μgL -1 (R 2 =9992). The detection limit and pre-concentration factor were found to be 0.082μgL -1 and 265, respectively., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The separation and pre-concentration of pb 2+ ions from mollusk and fish samples were performed by nanocomposite of magnetic graphene oxide-polyimide, as an efficient solid-phase extraction sorbent. The nanocomposite was characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy. The parameters affecting the extraction processes including: amount of adsorbent, adsorption and desorption times, type and volume of the eluent solvent and interfering ions of the sample were investigated and optimized. The calibration curve was linear in the concentration ranges of 0.8-400μgL -1 (R 2 =0.998). The limit of detection and quantification were obtained as 0.25μgL -1 and 0.80μgL -1 , respectively. The relative standard deviation was 7.3% and the pre-concentration factor was 141. A gastropod, Trochus erithreus, and a muscle tissue of fish, Otolithes ruber, were analyzed as real samples and good relative spiked recoveries (95-106%) were obtained., (Copyright © 2017 Elsevier Ltd. All rights reserved.)