Distribution of hydrogen sulfide, nitrogen and phosphorous species in inshore and offshore sediments of the south Caspian Sea.

This study aimed to geochemically investigate the sediments of the south Caspian Sea at different depths in summer and winter 2020. Sampling was conducted in 5 transects along the south coastline of the Caspian Sea and sediment grain size, hydrogen sulfide, Oxidation-reduction potential (Eh), total nitrogen, nitrite, nitrate, ammonium, total phosphorus, organic and inorganic phosphorous were measured. Eh values showed significant differences between seasons and between different transects (p < 0.05). Hydrogen sulfide ranged from 1.87 to 307.00 ppm. No significant difference was observed in hydrogen sulfide between seasons and among depths (p > 0.05). Total, inorganic and organic phosphorus contents were 782.96-1335.79 ppm, 639.66-1183.60 ppm, and 42.58-205.46 ppm, respectively. Total nitrogen revealed significant differences among transects (p < 0.05). Based on sediment quality guidelines, most sampling sites had alerting conditions for organic matter, and phosphorous contamination was detected at all stations. Anoxic condition was seen at most sites according to sedimentary Eh.

Basin scale monitoring of microplastics and phthalates in sediments from the Persian Gulf and the Gulf of Makran using GIS-based algorithms: Insights towards spatial variation and potential risk assessment.

Information on sedimentary microplastics and phthalates has been restricted to the coastal regions of the Persian Gulf and the Gulf of Makran. Our basin-wide study monitored their levels, spatial behaviors, and potential risks using GIS-based techniques. Microplastics and phthalates ranged from 5 to 75 particles/kg d.w and 0.004-1.219 µg g-1 d.w, respectively. Microplastics were in the size category of 100 µm to 3 mm, and black microfibers (< 1 mm) and high-density polymers were dominant. The total number of microplastics was between 356.333 × 1012 and 469.075 × 1012 particles in the surface sediments of the studied regions (confidence interval = 99 %). Diethylhexyl phthalate (DEHP) and Di-isobutyl phthalate contributed 88 % of detected phthalates. Significant correlations among microplastic abundance, total phthalates, and DEHP were distinguished (p < 0.05). Overall, the findings reiterated the widespread presence of microplastics and a potential link between phthalates and microplastics. Semi-variogram, cluster Voronoi polygons, and Trend analysis identified spatial outliers and major deposition sites of microplastics and phthalates and consequently outlined the localities where upcoming studies should be concentrated. A hotspot of potential risks was marked using Fuzzy logic and GIS-based algorithms in the Sea of Makran, covering an area equal to 342. 99 km2.

Distribution of microplastics in upstream and downstream surface waters of the Iranian rivers discharging to the southern Caspian Sea.

Microplastic pollution in the riverine ecosystems has caught many attentions in the scientific literatures. However, little information is available about the abundance and distribution of microplastics of the rivers discharging to the Caspian Sea. The aim of this study was to assess the spatial and seasonal distribution of microplastics in the surface waters of thirteen rivers discharging to the southern Caspian Sea. Microplastics were found in all stations with uneven distributions. The average concentrations of microplastics in the stations during snowmelt and dry seasons were 1.406 ± 0.1380 microplastics/m3 and 0.4070 ± 0.01500 microplastics/m3, respectively. Positive gradients of the rivers microplastics concentration from upstream to downstream were found. White/transparent polyethylene (PE) particles with the shape of fragment/film and the length (L) of ≤ 1 mm were the most common microplastics in the surface waters of the rivers discharging to the southern Caspian Sea. Also, the mean concentration of microplastics in spring snowmelt and runoff period was 3.45 times higher than in dry period. Factors such as sewage and household wastes; landfills; and recreational-tourism, fishing and agricultural activities along the rivers may contribute to microplastic contamination in downstream stations. Our data provide baseline information of microplastics in surface waters of rivers discharging to the southern Caspian Sea.

Sources and hotspots of microplastics of the rivers ending to the southern Caspian Sea.

The occurrence of microplastics (MPs) in beach sediments of the southern Caspian Sea was well documented, however, there are still many unknowns about the abundances and distributions of MPs in the rivers ending to the Caspian Sea. Here, bank sediments of 26 sites in the thirteen rivers were surveyed in two seasons. However, there was not any significant difference (p > 0.05) between the concentrations of MPs during the two seasons. MPs were detected in all samples with mean concentrations of 214.08 ± 14.35 MPs/kg. The most common size, shape, color, and polymer types of MPs were L < 300 µm, fragment/film, white/transparent, and polystyrene (PS), respectively. In all rivers, positive MP gradients from upstream to downstream were observed. Maximum concentrations of MPs were found in the downstream parts of Chalus, Haraz, and Safarud rivers. Recreational-tourism and fishing activities had significant positive relationships (p < 0.05) with concentration of MPs in the rivers.

Effect of zinc nanoparticles on the growth and biofortification capability of mungbean (Vigna radiata) seedlings.

Zinc insufficiency is a nutritional trouble worldwide, especially in developing countries. In the current study, an experiment was conducted to evaluate the effect of supplementation of MS media culture with different concentrations of ZnO nanoparticles (NPs) (0, 10, 20, 40, 80, and 160 ppm) on growth, nutrient uptake, and some physiological parameters of 7-days-old mung bean seedlings. ZnO NPs enhanced the Zn concentration of mung bean from 106.41 in control to more than 4600 µg/g dry weight in 80 and 160 ppm ZnO NPs treated seedlings. Our results showed that ZnO NPs in the concentration range from 10 to 20 ppm had a positive influence on growth parameters and photosynthetic pigments. Higher levels of ZnO NPs negatively affected seedling's growth by triggering oxidative stress which in turn caused enhancing antioxidative response in seedlings including polyphenol oxidase and peroxidase activity as well as phenolic compounds and anthocyanine contents. Considering the positive effects of ZnO NPs treatment on mungbean seedlings growth, micronutrents, protein and shoot phenolics content, 20 ppm is recommended as the optimal concentration for biofortification. Our findings confirm the capability of ZnO NPs in the remarkable increase of Zn content of mungbean seedlings which can be an efficient way for plant biofortification and dealing with environmental stress. Supplementary information: The online version contains supplementary material available at 10.1007/s11756-022-01269-3.

Curcumin-Melamine For Solid-Phase Microextraction of Volatile Organic Compounds from Aqueous Samples.

The hybrid coating of curcumin and melamine was prepared by a simple electrochemical method. Some physical and chemical properties of the fiber were studied by several methods such as FT-IR, scanning electron microscopy and X-ray fluorescence spectroscopy. The fiber was stable at the inlet of a gas chromatograph at temperatures up to 280°C. The fiber has been used for the extraction of ethylbenzene, toluene and xylenes (ETX). Some parameters of headspace solid-phase microextraction, including extraction time, temperature and salt amount, were optimized. Under the optimized situation, the detection limits were 0.15-0.21 µg L -1 and the linear ranges were within the range of 0.5-1,000 µg L-1 (r2 ≥ 0.99). The intra-day and inter-day relative standard deviations were 10.2-13.7 and 13.0-15.6%, respectively, at a concentration level of 10 µg L-1 from each compound by applying a single fiber. The method was used to successfully analyze wastewater and pool water samples.

Combining theoretical concepts and Geographic Information System (GIS) to highlight source, risk, and hotspots of sedimentary PAHs: A case study of Chabahar Bay.

Sedimentary PAHs are regionalized variables and their levels, source, and ecological hazards must be discussed in relation to their spatial locations. Our research targeted GIS and Chabahar Bay-Iran to trace spatial variability of PAHs, improve the diagnostic ratios and receptor models in source identification, and determine hotspot of PAH-originated hazards. The entropy Voronoi map distinguished an "entropy strip" in which ∑22PAHs levels increased sharply. Different molecular signatures were individually interpolated and the indicative ratios of distinctive sources were extracted and summed by GIS. The resulting code map reduced potential disagreement among molecular signatures and highlighted the areas where petroleum inputs are prevalent. PCA-MLR analysis extracted three potential sources including fossil fuel combustion (54.36%), petrogenic inputs (29.03%), and vehicle exhaust emissions (16.61%). Interpolated risk layers were re-arranged and overlaid via Fuzzy Membership Functions. The obtained ''Fuzzy AND" map showed the hotspot of the study area in the vicinity of a seasonal estuary.

Catalytic nanozyme Zn/Cl-doped carbon quantum dots as ratiometric fluorescent probe for sequential on-off-on detection of riboflavin, Cu2+ and thiamine.

A novel metal-doped Zn/Cl carbon quantum dots (Zn/Cl-CQDs) was developed successfully as ratiometric fluorescent probes for the sequential on-off-on detection of riboflavin, Cu2+ ion and thiamine. The excellent catalytic performance of the Zn/Cl-CQDs nanozyme serves as an ideal platform for sensitive detection of thiamine. Due to the addition of riboflavin to the Zn/Cl-CQDs, the blue emission peak of Zn/Cl-CQDs at 440 nm remains unaffected and used as an internal reference approach, while the green emission peak of riboflavin at 520 nm appeared and increased remarkably. Following the presence of Cu2+, a quenching blue fluorescence signal of Zn/Cl-CQDs was observed which resulted in consequent fluorescent 'turn-off' response toward Cu2+ ion. Finally, upon the addition of thiamine to the above solution under alkaline condition, the blue emission of Zn/Cl-CQDs was gradually recovered. The prepared Zn/Cl-CQDs could act as a nanozyme catalyst for directly catalyzing the oxidation of non-fluorescent substrate of thiamine to produce highly fluorescent substrate of thiochrome. As a result, the blue fluorescence emission peak at 440 nm was recovered. Eventually, the sequential detection properties of ratiometric probes for riboflavin, Cu2+ ion and thiamine were successfully applied in VB2 tablets, drinking water and VB1 tablet with good recoveries of 96.21%, 98.25% and 98.44%, respectively.

Distribution, source and ecological risk assessment of polycyclic aromatic hydrocarbons in the sediments of northern part of the Persian Gulf.

Distribution, sources, and ecological risk of 43 compounds of polycyclic aromatic hydrocarbons (PAHs) in surficial sediments of the Persian Gulf were investigated. The sediments were sampled from 60 offshore stations during an oceanographic cruise in the winter of 2012. Gas chromatography high-resolution mass spectrometry was used for the PAHs determinations in sediment samples. The concentrations of 21 parent PAHs, 7 methylated PAHs, 11 oxygenated PAHs and 4 nitrated PAHs were 9.0-201.5 ng g-1 dw, 3.3-60.3 ng g-1 dw, 15.2-172.7 ng g-1 dw and 0.1-8.3 ng g-1 dw, respectively. Among 21 parental PAHs, naphthalene (29.35 ng g-1 dw), phenanthrene (4.6 ng g-1 dw), and pyrene (3.18 ng g-1 dw) were the most abundant compound. 1-acenaphthenone (43.41 ng g-1 dw) and 2-methylnaphthalene (7.15 ng g-1 dw) showed the highest concentration in the oxy- and methyl-PAHs, respectively. The concentrations of nitro-PAHs were between not detected to 4 ng g-1 dw. According to the ecological risk assessment, the calculated total toxicity of PAHs was at below the lethal level on benthic organisms in all stations in the Persian Gulf, but there is risk of toxicity for the benthic organism in the Gulf of Oman (from the Strait of Hormuz to Jask). In general, nitrogenated and oxygenated derivatives did not show a significant risk in the study area. Based on the diagnostic ratios, the mixed sources (both petrogenic and pyrogenic) and pyrogenic sources have been identified for PAHs. Biomass combustion source has been identified for the stations near flares and gas fields. Principle component analysis-multivariate linear regression analysis for source identification shows that maritime traffic, abundant flares that burn the gas in oil, gas fields and dust storms have a major impact on the production of PAHs in this area.

Nicotinamide-Functionalized Carbon Quantum Dot as New Sensing Platform for Portable Quantification of Vitamin B12 in Fluorescence, UV-Vis and Smartphone Triple Mode.

Development of an efficient, portable and simple nanosensor-based systems with reliable analytical performance for on-site monitoring of vitamin B12 (VB12) are still major problems and a challenging work for quality control of manufacturers. Herein, a new fluorescence, UV-Vis and smartphone triple mode nanosensors were designed for the simultaneous detection of VB12 with high sensitivity and accuracy. A novel nanosensor was synthesized through nicotinamide-functionalizing of carbon quantum dot (NA-CQDs) by an one-step microwave-assisted method with green approach. The NA-CQDs sensor showed excellent fluorescence properties and wide linear ranges from 0.1-60 µM with the detection limits of 31.7 nM. Moreover, color changes of NA-CQDs induced by the VB12 could also be detected by UV-Vis spectrophotometer and inhouse-developed application installed on smartphone as a signal reader, simultanusly. The Red, Green and Blue (RGB) intensities of the colorimetric images of NA-CQDs/VB12 system which taken by smartphone's camera converted into quantitative values by the application. A smartphone-integrated with NA-CQDs as colorimetric sensing platform displays good linear ranges (4.16 to 66.6 µM) for on-site determination of VB12 with detection limit of 1.40 µM. The method was successfully applied in the determination of VB12 in complex pharmaceutical supplement formulations without any sample pre-treatment and matrix interfering effects. The recovery results (96.52% to 105.10%) which were in agreement with the reference methods, demonstrating the capability of the smartphone-assisted colorimetric sensing platform in many on-site practical applications of quality controls.

Spatial distribution of microplastics in sandy beach and inshore-offshore sediments of the southern Caspian Sea.

The occurrence of microplastics (MPs) in nearshore zones of the southern Caspian coasts is well documented; however, no data are available on MP occurrence in offshore sediments. In this study, six sandy beach stations and 18 inshore-offshore stations (six transects) were surveyed. MPs were detected in all sediment samples. The mean abundances of MPs in the beach and inshore-offshore stations were 196.67 ± 11.58 and 103.15 ± 7.21 MPs/kg, respectively. Fibers constituted the most common shape of MPs. Polystyrene (PS) and polyethylene terephthalate (PET) were the major polymer types found in the beach and inshore-offshore sediments, respectively. In most transects, negative MP gradients were observed from nearshore to offshore, which showed that coastal fishing, tourism, and rivers were the main sources of MPs in this area. These results will improve our understanding on MPs pollution in the marine ecosystem. We recommend further MP studies in different parts of the Caspian Sea to develop appropriate management programs.

Normal alkanes in sediments from the Persian Gulf: spatial pattern and implications for autochthonous, allochthonous, and petroleum-originated contaminants.

Surface sediments (n = 124) were gathered to evaluate spatial pattern and source apportionment of ∑24n-alkanes in the Persian Gulf. Moran's I indices revealed that ∑24n-alkanes were randomly distributed in sampling space in general. One noticeable exception was a significant spatial high-high cluster (Z-score = 8.6). Profile of n-alkanes observed for this cluster maximized at n-C20, n-C18, n-C16, and n-C22. Detection of very low carbon preference indices and strong even carbon-numbered predominance suggested that bacterial inputs were the process making this cluster. Based on diagnostic ratios and GIS techniques, in situ production of organic materials was widespread in the studied space. Allochthonous and petroleum-based inputs were not traceable for 73.8% and 24.7% of the area, respectively. Petrogenic source apportionment map proposed that petroleum-originated contaminants were probably limited to 6.32 km2 of the sampling matrix. The biogenic inputs (autochthonous and allochthonous inputs) and not the petroleum contaminants were the main source of n-alkanes deposited.

Microplastic pollution in inshore and offshore surface waters of the southern Caspian Sea.

In this study, as the first comprehensive monitoring, the occurrence of microplastics (MPs) in inshore and offshore surface waters of the southern Caspian Sea was investigated. Our data indicated that MPs, which were detected in all the samples, were widely distributed in the thirteen studied stations. Non-normally distribution of the MPs was observed among the studied stations (p<0.05). The average concentration of microplastics in the selected stations was 0.246 ± 0.020 MP/m3. In most of the transects, negative gradients of MPs from coastal waters to deeper waters were observed. The dominant size and color of MPs in the inshore and offshore water samples was 1000-5000 µm and white-transparent, respectively. Films and fibers constituted about 50% and 40% of the total number of MPs of the water samples, respectively. Also, polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) were the three main polymer types of microplastics in the inshore and offshore surface waters. Our data provide valuable evidence for the comparative assessing of future data regarding decreases or increases of MPs in the southern Caspian Sea.

Occurrence of polychlorinated biphenyl congeners in marine sediment of Makran region, Chabahr bay, Iran.

In this study, selected PCB congeners (IUPAC numbers 28, 52, 101, 138, 153, and 180) were quantified in 34 stations of Chabahr bay and around it in the Makran region of Iran. The sum of total PCB concentrations varied from below the detection limit to 485 ng kg-1 dry weight of sediment. Based on the Canadian Sediment Quality Guidelines, the effect of detected PCBs was negligible for aquatic organisms. According to the dominance of PCB 28 and 52 with average range of 62 to 100% of total PCBs, maritime transportation and atmospheric deposition appear to be the important source of PCBs in this region. Further, the presence of components of commercial products such as ClophenA50 appears to be one of the probable sources.

Rapid and sensitive fluorescence and smartphone dual-mode detection of dopamine based on nitrogen-boron co-doped carbon quantum dots.

A dual-mode fluorescence and colorimetric biosensor based on nitrogen-boron co-doped carbon quantum dot (N-B CQDs) for rapid and sensitive detection of dopamine (DA) was developed. The quantum dot luminescent materials, N-B CQDs, were prepared by a one-step microwave-assisted method. The N-B CQDs were characterized using SEM, HR-TEM, XRD, FT-IR, Raman, fluorescence, and UV-Vis techniques. The dual-mode assays of fluorescence and colorimetric methods were used for detection of DA. The high fluorescent N-B CQDs mediated turn-off assay for the facile room temperature detection of dopamine via inner filter effect (IFE) and Forster resonance energy transfer (FRET) processes at basic pH. The colorimetric detection of DA was also developed via in-house android application using a smartphone and N-B CQD solution-based nanosensor. The smartphone-based colorimetric biosensors generated more reliable information for quantitative analysis of color changes than the naked eye. Furthermore, a smartphone application with N-B CQD solution-based nanosensor was integrated to monitor the color changes through the DA addition. Wide linear ranges were achieved for DA in the ranges 0.25-50 µM and 5-500 µM with fluorescence and smartphone-based method, respectively. The satisfactory results of the dual-mode detection of DA, not only in aqueous solution, but also in human urine and serum biological sample demonstrated its potential application in biosensing, as a point of care diagnostic tool. Graphical abstract.

Intrinsic peroxidase-like activity of graphene nanoribbons for label-free colorimetric detection of dopamine.

Graphene nanoribbons (GNR) with intrinsic peroxidase mimic activity were introduced as a nanozyme with catalytic activity in oxidation of a typical chromogenic peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), in the presence of H2O2. The proposed artificial enzyme was used as a label-free biosensor for rapid and sensitive colorimetric detection of dopamine (DA) according to a blue color fading which occurred due to the inhibition of TMB oxidation. Attractively, GNR exhibited an excellent catalytic activity over other carbon-based nanostructures due to its unique and extraordinary structural properties. Considering the changes of A653 versus DA concentration, a good linear dependency was achieved in the concentration range of 0.1-50 µM (0.1-1 and 2.5-50 µM) with a detection limit of 0.035 µM. The present peroxidase mimetic as a simple and rapid label-free sensor was successfully applied for detection of DA in serum samples, suggesting a promising sensitive sensing platform with great potential for biological and diagnostic applications.

Enhanced LSPR performance of graphene nanoribbons-silver nanoparticles hybrid as a colorimetric sensor for sequential detection of dopamine and glutathione.

In the present study, a novel plasmonic sensing platform was proposed for sequential colorimetric detection of dopamine (DA) and glutathione (GSH) in human serum sample by taking advantage of plasmon hybridization in graphene nanoribbons/sliver nanoparticles (GNR/Ag NPs) hybrid. DA was detected based on etching strategy and morphology transition of label-free Ag NPs hybridized with GNR. As a result of the etching process, hexagonal Ag NPs were changed to smaller corner-truncated nanoparticles and a blue shift was observed in its plasmonic band, accompanied by the color change from green to red. Sequentially, GSH induced aggregation of Ag NPs which resulted in a decrease in absorption intensity of Ag NPs plasmonic band and a color change from red to gray. By employing GNR/Ag NPs hybrid as a sensitive colorimetric sensor, DA and GSH were successfully detected in low concentrations of 0.04 µM and 0.23 µM, respectively. The same experiment was carried out in the absence of GNR and the detection limits were obtained 0.46 and 1.2 µM for DA and GSH, respectively. These results confirmed the effective role of GNR on the sensitivity improvement of GNR/Ag NPs hybrid. The proposed simple and sensitive sensing approach offered a beneficial and promising platform for sequential detection of DA and GSH in the biological samples.

Preparation of a magnetic polystyrene nanocomposite for dispersive solid-phase extraction of copper ions in environmental samples.

The core shell nanostructure of magnetic polystyrene (PS@Fe3O4) was prepared and its physic-chemical properties were studied FT-IR, SEM, TEM, VSM and BET + BJH. The new adsorbent was applied in the dispersive solid phase extraction technique for measuring copper ions in water, Soil and Oyster samples. Analysis is carried out using a flame atomic absorption spectrometry system. Effective parameters on extraction efficiency, such as pH of extraction solution, sorbent dosage, contact time, concentration and volume of desorption eluent and desorption time were optimized using one at a time method. N2 adsorption-desorption experiment resulted in high BET surface area (32.002 m2 g-1) and large pore volume (0.1794 cm3 g-1) for PS@ Fe3O4 nanocomposite. Under the optimum conditions, a calibration curve within the range of 5-40 ng mL-1 with an appropriate coefficient of determination (R2) of 0.9946 was obtained. Preconcentration factor (PF) and limit of detection (LOD) were found to be 55 and 1.6 ng mL-1, respectively. The repeatability and reproducibility for three replicate measurements at the concentration of 25 ng mL-1 were 2.5%-1.4%, respectively. The Freundlich adsorption isotherm and pseudo-second-order kinetic model were consistent to experimental data in adsorption mechanism study. The maximum adsorption capacity was 19.56 mg g-1 for Cu (II). Finally, the efficiency of the method was investigated for analysis of the copper in environmental samples and good relative recoveries (RR%) were obtained within the range of 99.2% to 101.2%.

Neustonic microplastic pollution in the Persian Gulf.

Currently, microplastics are a major challenge threatening marine environment. Given little information on their prevalence in the Persian Gulf, the present study as the first comprehensive study was conducted to evaluate microplastics abundance in surface waters. Neustonic samples were collected from 15 stations along the Persian Gulf. Visually separated microplastics were categorized according to their size, shape, and color. ATR-FTIR method was used to identify the composition of polymers. Microplastics were found in all sampling stations and their density varied from 1.5 × 103 to 4.6 × 104 particle.km-2 with a mean density of 1.8 × 104 particle.km-2. Fibers were the most dominant shape of microplastics (44.1%). Approximately 76% of the analyzed microplastics were polyethylene and polypropylene and the predominant colors of the microplastics were white and blue. Results of the study confirmed prevalence of microplastics in the Persian Gulf, and findings suggested a pressing need to investigate their effects on marine life and human health.

Identification of microplastics in the sediments of southern coasts of the Caspian Sea, north of Iran.

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.