Combined toxic effects of polystyrene nanoplastics and lead on Chlorella vulgaris growth, membrane lipid peroxidation, antioxidant capacity, and morphological alterations.

In recent years, there has been a significant rise in the utilization of amino-functionalized polystyrene nanoplastics (PS-NH2). This surge in usage can be attributed to their exceptional characteristics, including a substantial specific surface area, high energy, and strong reactivity. These properties make them highly suitable for a wide range of industrial and medical applications. Nevertheless, there is a growing apprehension regarding their potential toxicity to aquatic organisms, particularly when considering the potential impact of heavy metals like lead (Pb) on the toxicity of PS-NH2. Herein, we examined the toxic effects of sole PS-NH2 (90 nm) at five concentrations (e.g., 0, 0.125, 0.25, 0.5, and 1 mg/L), as well as the simultaneous exposure of PS-NH2 and Pb2+ (using two environmental concentrations, e.g., 20 µg/L for Pb low (PbL) and 80 µg/L for Pb higher (PbH)) to the microalga Chlorella vulgaris. After a 96-h exposure, significant differences in chlorophyll a content and algal growth (biomass) were observed between the control group and other treatments (ANOVA, p < 0.05). The algae exposed to PS-NH2, PS-NH2 + PbL, and PS-NH2 + PbH treatment groups exhibited dose-dependent toxicity responses to chlorophyll a content and biomass. According to the Abbott toxicity model, the combined toxicity of treatment groups of PS-NH2 and PbL,H showed synergistic effects. The largest morphological changes such as C. vulgaris' size reduction and cellular aggregation were evident in the medium treated with elevated concentrations of both PS-NH2 and Pb2+. The toxicity of the treatment groups followed the sequence PS-NH2 < PS-NH2 + PbL < PS-NH2 + PbH. These results contribute novel insights into co-exposure toxicity to PS-NH2 and Pb2+ in algae communities.

Microplastics as carriers of iron and copper nanoparticles in aqueous solution.

In recent years, microplastics have attracted a lot of attention due to their excessive spread in the environment, especially in aquatic ecosystems. By sorbing metal nanoparticles on their surface, microplastics can act as carriers of these pollutants in aquatic environments and thus cause adverse effects on the health of living organisms and humans. This study, investigated the adsorption of iron and copper nanoparticles on three different microplastics i.e. polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS). In this regard, the effects of parameters such as; pH, duration of contact and initial concentration of nanoparticle solution were investigated. By using atomic absorption spectroscopic analysis, the amount of adsorption of metal nanoparticles by microplastics was measured. The maximum amount of adsorption occurred at pH = 11, after a duration time of 60 min and at the initial concentration of 50 mg L-1. Scanning electron microscope (SEM) images showed that microplastics have different surface characteristics. The spectra obtained from Fourier transform infrared analysis (FTIR) before and after the adsorption of iron and copper nanoparticles on microplastics were not different, which showed that the adsorption of iron and copper nanoparticles on microplastics was physically and no new functional group was formed. X-ray energy diffraction spectroscopy (EDS) showed the adsorption of iron and copper nanoparticles on microplastics. By examining Langmuir and Freundlich adsorption isotherms and adsorption kinetics, it was found that the adsorption of iron and copper nanoparticles on microplastics is more consistent with the Freundlich adsorption isotherm. Also, pseudo-second-order kinetics is more suitable than pseudo-first-order kinetics. The adsorption ability of microplastics was as follows: PVC > PP > PS, and in general copper nanoparticles were adsorbed more than iron nanoparticles on microplastics.

Comparative assessment of human health risk associated with heavy metals bioaccumulation in fish species (Barbus grypus and Tenualosa ilisha) from the Karoon River, Iran: Elucidating the role of habitat and feeding habits.

Concentrations of Cd, Ni, and Pb were measured in the liver and muscle tissues of benthic omnivorous (Barbus grypus) and pelagic herbivorous (Tenualosa ilisha) fish collected from two sampling sites along the Karoon River, Khuzestan Province, southwest of Iran. Potential human health risks were evaluated by measuring the estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and target cancer risk (TR). The results highlight the important role of habitat and feeding habits in the uptake of HMs by the two species. The EDI for all HMs exceeded the oral reference doses (RfDo) provided by the USEPA, indicating the two fish species are not entirely safe for human consumption. The THQ values were within the permissible limit (< 1), while HI values (> 1) showed there was non-carcinogenic risk for consumers. The TR values for Pb were within the acceptable range (1.00E-06-1.00E-04) for both species.

Occurrence and distribution of microplastics in wetlands.

Presence of microplastic particles has been reported in all over the world, even in remote areas with no human activities. Wetlands are important transitional areas between terrestrial and aquatic systems. However, microplastic pollution in wetlands is less studied than other aquatic ecosystems. In this review, documented researches about microplastic occurrence and distribution in different components of wetland systems (except constructed wetlands) were investigated. In this regard, all available articles from different science databases with the keywords microplastic, wetland and lagoon in title were examined and results were proposed by text, table and diagram, after standardization of data express units. Based on results, wetland ecosystems are prone to microplastic pollution. Based on particle properties, PE/PP and fiber/fragment were the most dominant reported chemical composition and particle shapes, respectively.

Nano-sized polystyrene plastics toxicity to microalgae Chlorella vulgaris: Toxicity mitigation using humic acid.

Polystyrene nanoplastics (PS-NPs) can cause toxicity in aquatic organisms, but presence of natural organic matter (NOM) may alter toxicity of PS-NPs. To better understand effects of NOM on acute toxicity of PS-NPs, humic acid (HA) as a model of NOM was added to green microalga Chlorella vulgaris medium in the presence of amino-functionalized polystyrene nanoplastics (PS-NH2). Acute toxicity tests of PS-NH2 to C. vulgaris biomass and chlorophyll a content showed statistical differences between media treated with different concentrations of PS-NH2 and control groups (p<0.05). HA significantly mitigated PS-NH2 toxicity to C. vulgaris biomass and chlorophyll a end-points (p<0.05). Additionally, high HA concentration was more effective than low concentration (10 vs 5 mg/L), showing a greater ameliorative effect on PS-NH2 acute toxicity (p<0.05). Algae exposed to higher PS-NH2 concentrations showed greater morphological changes (i.e., diminution of photosynthetic pigments, reduction of algal size and formation of more cellular aggregates). Formation of high amounts of algal aggregates under influence of PS-NH2 was presumably related to the high electrostatic tendency of these particles (with positively charged surfaces) to C. vulgaris polysaccharide walls (having negative charge). Formation of aggregates was significantly reduced in the presence of HA. HA with dominant negatively charged functional groups (following sorption by PS-NH2 via reduction of PS-NH2 zeta potential), could decrease electrostatic attraction between PS-NH2 and algae, thereby substantially ameliorating cellular aggregation and cell size reduction.

The effectiveness of urban trees in reducing airborne particulate matter by dry deposition in Tehran, Iran.

Deposition of atmospheric pollution as particulate matter (PM) has become a serious issue in many urban areas. This study measured and estimated the amount of atmospheric PM deposition onto oriental plane (Platanus orientalis L.) trees located in Tehran Megapolis, Iran. PM deposited on the leaves of urban trees during spring and summer was estimated using leaf wash measurements. In addition to direct measurements, the dry deposition velocity and the yearly whole-tree PM deposition were estimated using both field measurements and a theoretical model of deposition flux. We estimated air quality improvement as a result of the trees at respiratory height (1.5 m), tree height (10 m), and boundary layer height (1719 m). Foliar PM deposition during spring and summer was estimated to average 0.05 g/leaf and 41.39 g/tree using direct measurements. The annual PM deposited on the leaves, trunk, and branches of an average urban tree was calculated to be 78.60 g/tree. Trees were estimated to improve air quality at 1.5 m, 10 m, and 1719 m from ground level by 25.8%, 5.8%, and 0.1%, respectively. Hence, oriental plane trees substantially reduce PM at respiratory height.

Microplastic sampling techniques in freshwaters and sediments: a review.

Pollution by microplastics is of increasing concern due to their ubiquitous presence in most biological and environmental media, their potential toxicity and their ability to carry other contaminants. Knowledge on microplastics in freshwaters is still in its infancy. Here we reviewed 150 investigations to identify the common methods and tools for sampling microplastics, waters and sediments in freshwater ecosystems. Manta trawls are the main sampling tool for microplastic separation from surface water, whereas shovel, trowel, spade, scoop and spatula are the most frequently used devices in microplastic studies of sediments. Van Veen grab is common for deep sediment sampling. There is a need to develop optimal methods for reducing identification time and effort and to detect smaller-sized plastic particles.

Bioaccumulation of heavy metals in fish species of Iran: a review.

Accumulation of heavy metals (HMs) in fish tissues is an important factor in monitoring the health and safety of aquatic ecosystems. Furthermore, fish are important parts of aquatic food chains and play a significant role in human health. Considering the significant role of fish in the diet of humans and their ability to transfer and biomagnify HMs, it is necessary to determine and study these contaminants in fish tissues, especially in the edible parts of the fish. In addition to the other ecological and economic services of aquatic ecosystems, water bodies, especially the Persian Gulf in the south and the Caspian Sea in the north of Iran, are the main sources of seafood for people in nearby areas, as well as people living farther away who have gained access to seafood due to the extensive trade of aquatic organisms. This study provides an overview of the health conditions of the aquatic ecosystems in Iran by monitoring HM bioaccumulation in fish species. For this purpose, we reviewed, summarized, and evaluated papers published on HM concentrations in fish species from different aquatic ecosystems, including the Persian Gulf, the Caspian Sea, wetlands, rivers, qanats, water reservoirs, lakes, and dams, with emphasis on species habitats, feeding habits, and target organs in accumulation of HMs. Generally, the highest concentrations of HMs were observed in fishes collected from the Persian Gulf, followed by species from the Caspian Sea. Species inhabiting the lower zone of the water column and carnivorous and/or omnivorous species showed the highest levels of HMs. Moreover, liver was the main accumulator organ for HMs.

Understanding plastic degradation and microplastic formation in the environment: A review.

Plastic waste are introduced into the environment inevitably and their exposure in the environment causes deterioration in mechanical and physicochemical properties and leads to the formation of plastic fragments, which are considered as microplastics when their size is < 5 mm. In recent years, microplastic pollution has been reported in all kinds of environments worldwide and is considered a potential threat to the health of ecosystems and humans. However, knowledge on the environmental degradation of plastics and the formation of microplastics is still limited. In this review, potential hotspots for the accumulation of plastic waste were identified, major mechanisms and characterization methods of plastic degradation were summarized, and studies on the environmental degradation of plastics were evaluated. Future research works should further identify the key environmental parameters and properties of plastics affecting the degradation in order to predict the fate of plastics in different environments and facilitate the development of technologies for reducing plastic pollution. Formation and degradation of microplastics, including nanoplastics, should receive more research attention to assess their fate and ecological risks in the environment more comprehensively.

Scientific studies on microplastics pollution in Iran: An in-depth review of the published articles.

This literature review was conducted to collect present data on microplastics pollution in Iran's ecosystems. Most of the studies performed in aquatic environment were conducted in Persian Gulf & Oman Sea (70%). The Persian Gulf, along with the beaches of Bushehr and Hormozgan Provinces, are the most studied areas. Moreover, most of the studies were conducted in aquatic environments and only four studies were conducted in terrestrial environment (4/42). One study has assessed microplastics in commercial salt and another study has reported the microplastics presence in Iranian bottled mineral water brands. The investigation of microplastics associated with biota was highlighted, customarily for fish species. Microplastics were also present in urban wastewater samples in Sari and Bandar Abbas cities. Three studies were performed in freshwater ecosystems until now (Haraz River, Anzali wetland, and Taleqan dam). The need for further studies in this field still exists, especially in terrestrial and freshwater compartments.

Use of 13C and 15N for the determination of the metal flux in the Caspian Sea fishes.

Biomagnification of metals (Cd, Cr, Cu, Mn, Ni, Zn, Fe) was investigated in 14 species of Caspian Sea commercial fishes using 13C and 15N analyses to decode their trophic position (TP). The stable nitrogen isotope ratios varied among the Caspian Sea fish species from 8.7 to 13.8‰ while the stable carbon isotope ratios varied from -23.7 to -17.6‰. The TPs varied between 2.2 and 4.9. Clupeonella caspia had the lowest average TP, and Acipenseridae species (except Acipenser persicus) and Sander lucioperca had higher average TPs. Wide intra- and inter-specific differences were observed in metal concentrations. The stable isotope results were relatively coordinated with feeding behaviour of species. However, some exceptions were observed particularly in Alburnus chalcoides and S. lucioperca. By comparing logarithmic concentration of metals vs. TPs, no metal biomagnification was observed. The estimated daily intakes of metals were lower than the provisional tolerable daily intakes and, thus, these amounts do not pose any threat on human health.

Biodegradation of low molecular weight polyacrylamide under aerobic and anaerobic conditions: effect of the molecular weight.

The biodegradation of polyacrylamide (PAM) includes the hydrolysis of amino groups and cleavage of the carbon chain; however, the effect of molecular weight on the biodegradation needs further investigations. In this study, biodegradation of low molecular weight PAM (1.6 × 106 Da) was evaluated in two aerobic (25 °C and 40 °C) and two anaerobic (35 °C and 55 °C) reactors over 100 days. The removal of the low molecular weight PAM (52.0-52.6%) through the hydrolysis of amino groups by anaerobic treatment (35 °C and 55 °C) was much higher than that of the high molecular weight (2.2 × 107 Da, 11.2-17.0%) observed under the same conditions. The molecular weight was reduced from 1.6 × 106 to 6.45-7.42 × 105 Da for the low molecular weight PAM, while the high molecular weight PAM declined from 2.2 × 107 to 3.76-5.87 × 106 Da. The results showed that the amino hydrolysis of low molecular weight PAM is easier than that of the high molecular weight one, while the cleavage of its carbon chain is still difficult. The molecular weights of PAM in the effluents from the two aerobic reactors (25 °C and 40 °C) were further reduced to 4.31 × 105 and 5.68 × 105 Da by the biofilm treatment, respectively. The results would be useful for the management of wastewater containing PAM.

Physicochemical properties of antibiotics: A review with an emphasis on detection in the aquatic environment.

Antibiotics have extensively been applied to rescue a great number of lives through prevention and treatment of contagious diseases and infections. They are either natural or human-made substances, which are broadly employed for promoting the health condition of human, plant, and animal. However, antibiotics are known to exert detrimental impacts on useful and nontarget microbiota of the biological system due to the overuse, continuous discharge into the environment, and subsequently aggregation in various environmental matrices. Physical and chemical properties help to evaluate whether a substance is more likely to concentrate on the terrestrial, aquatic, or atmospheric environmental matrix as well as its fate. Therefore, appropriate characterization and proper understanding of physicochemical attributes of antibiotics are indispensable to protect ecosystem health. In this paper, the antibiotic classifications and their physicochemical properties were reviewed with emphasis on detection in the aqueous environment. PRACTITIONER POINTS: Antibiotic compounds were classified in main classes, groups, and their main use. Tetracyclines, sulfonamides, aminoglycosides, macrolides, ß-lactams, quinolones, polyether ionophores, and glycopeptides are the most commonly detected antibiotics in the aquatic environment. Physical-chemical properties of the main antimicrobial classes were mentioned. Physicochemical properties can change under different environmental conditions such as pH and temperature.

Synthesis and evaluation of activated carbon/nanoclay/ thiolated graphene oxide nanocomposite for lead(II) removal from aqueous solution.

Novel porous nanocomposite (AC/NC/TGO) was successfully synthesized through the composition of activated carbon, nanoclay and graphene oxide as a Pb(II) adsorbent for the treatment of contaminated aqueous environment. The physicochemical properties and morphology of AC/NC/TGO were examined by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption techniques. Results showed Pb(II) adsorption on the AC/NC/TGO was rapid in the first 20 min and reached equilibrium in 40 min. Kinetic studies showed significant fit to the pseudo second order kinetic model (R2 ≥ 0.9965) giving an equilibrium rate constant (K2) of 0.0017 g mg-1 min-1 for Pb(II) loaded. The experimental adsorption data were better fitted with the Langmuir isotherm model than with the Freundlich isotherm model. Prepared nanocomposite exhibited high values of Brunauer-Emmett-Teller (BET) surface area of 1,296 m2 g-1 and total pore volume of 1.01 cm3 g-1. Maximum adsorption capacity (Qmax = 208 mg g-1) and a relatively high adsorption rate was achieved at pH 5.0 using an adsorbent dose of 0.5 g L-1 and an initial lead concentration of 50 mg L-1. High adsorption capacity, reusability, fast kinetics and simple synthesis method indicate that prepared nanocomposite can be suggested as a high-performance adsorbent for Pb(II) removal from polluted water.

Accumulation of heavy metals and As in liver, hair, femur, and lung of Persian jird (Meriones persicus) in Darreh Zereshk copper mine, Iran.

Rodents frequently serve as bioindicator to monitor the quality of the environment. Concentrations of 11 elements (Cd, Co, Ti, Fe, Mn, Cu, Sb, As, Sr, Ni, and Cr) were investigated and compared in liver, hair, femur, and lung of the Persian jird (Meriones persicus) from Darreh Zereshk copper mine, Iran. Metals were determined in different tissues of 39 individuals of Persian jird, collected by snap trap in 2014 from five areas of Darreh Zereshk copper mine. Samples were prepared by wet digestion method, and the contents of elements were analyzed with ICP-OES (VARIAN, 725-ES) instrument. Cadmium, Sb, and Co were below the limit of detection, and Mn and As were found only in hair and liver tissues. We detected the highest concentration of Cu, As, Ti, Fe, Mn, Cr, and Ni in hair in comparison with other tissues. Significant higher levels of Ti in femur and hair; Fe in liver and hair; Mn in liver; As in hair; Sr in lung; Cr in lung, hair, femur, and liver; Cu in femur; and Ni in liver and lung tissues were observed in females. Nearly all element concentrations in the tissues of Persian jird from flotation site, Darreh Zereshk and Hasan Abad villages and leaching site (mining areas) were higher than those from tailing dump site (reference site). We found the highest concentrations of As in liver and hair; Ni and Cr in liver, hair, and lung; and Sr in lung and hair tissues of Persian jird in leaching site. We tried to specify the status of elements before fully exploitation of Darreh Zereshk copper mine by using bioindicator species. Based on our achievements, initial activities did not strongly pollute the surrounded environment of the mine. The high abundance of Persian jird as well as their several proper features makes them a suitable species for biomonitoring programs especially for further studies will be performed after full exploitation of Darreh Zereshk copper mine.

Heavy metal bioaccumulation in sediment, common reed, algae, and blood worm from the Shoor river, Iran.

Concentrations of 11 metals (cadmium, zinc, copper (Cu), vanadium (V), lead, magnesium (Mg), manganese, aluminum, iron (Fe), chromium (Cr), and nickel), and one metalloid (arsenic (As)) were measured in sediment, common reed (Phragmites australis), algae (Spirogyra sp.), and blood worm (Chironomus sp.) tissues of samples collected from the Shoor river. Samples were dried, acid digested, and the concentrations of metals were measured using inductively coupled plasma-optical emission spectrometer. A higher concentration of heavy metals was accumulated in Spirogyra and Chironomids than sediment and common reed. The highest rate of accumulation was found for Mg, V, Fe, As, Cu, and Cr. Spirogyra and Chironomids are capable of accumulating and thereby removing metals from polluted water bodies and are suitable for biomonitoring purposes.

Metal concentrations in tissues of two fish species from Qeshm Island, Iran.

The purpose of this study was to determine the concentrations of metals, cadmium, chromium, lead and nickel in Liza vaigiensis and Johnius carutta, in order to: compare metal concentrations between two species with different gender, and to determine the significance between metal concentrations in the gill, liver and muscle. The highest mean concentrations of cadmium, chromium, lead and nickel in different tissues of these two fish species were found in the liver of L. vaigiensis at 0.68, 0.83, 0.37 and 1.42 µg g(-1), respectively; while the lowest mean concentrations of cadmium, chromium, lead and nickel were observed in the muscle of J. carutta at 0.16, 0.16, 0.03 and 0.29 µg g(-1), respectively. The results showed that the metal concentrations in both species were higher in the females than in the males (except chromium in gill and cadmium in muscle of J. carutta). Also, the results indicated that the metal concentrations were different among fish tissues (one-way ANOVA, p < 0.001), but there was no difference (except lead in gills of J. carutta) between sex (male vs. female).

Comparison of the metal concentrations in the feathers of three bird species from southern Iran.

This study was conducted to determine the concentration of metals, namely cadmium, lead, cobalt and copper, in the feathers of chukar (Alectoris chukar), see-see partridge (Ammoperdix griseogularis) and rock dove (Columba livia) in order to: examine the species, gender and age related variations in trace metal accumulation, and identify any relationships between species. Bird samples were collected in February 2012 from the Hormod protected area, southern Iran and the concentration of metals were measured using a Shimadzu AA 660 flame atomic absorption spectrophotometer. The concentrations in all three species were copper > lead > cadmium > cobalt. The average cadmium concentrations were 2.0, 1.9, and 1.9 µg/g for A. chukar, A. griseogularis, and C. livia, respectively. The average lead concentrations were 8.0, 5.4, and 7.7 µg/g for A. chukar, A. griseogularis, and C. livia, respectively. The results showed that in all three species, the highest metal concentrations were observed in female/adult birds and the lowest concentrations were found in female/juvenile birds (except lead in A. chukar and copper in C. livia).

Metal concentrations in the water of Chah nimeh reservoirs in Zabol, Iran.

The main objectives of this article were to monitor the metal concentrations of Fe, Cu, Pb, B, Ni, V, Cd, Se, As, and Cr in the water of Chah nimeh reservoirs in Zabol, south-eastern Iran; and to identify any relationships between metals. Metal concentrations in the water samples were analyzed using ICP-OES. The results indicated that there were a highly positive correlation between Cr and Se, Ni (p < 0.01), and, between As and Ni (p < 0.01). Also, there were significant differences between Cr, Ni, Pb, and Se in the water of Chah nimeh reservoirs.