Towards advanced removal of organics in persulfate solution by heterogeneous iron-based catalyst: A review.

Heterogeneous iron-based catalysts have drawn increasing attention in the advanced oxidation of persulfates due to their abundance in nature, the lack of secondary pollution to the environment, and their low cost over the last a few years. In this paper, the latest progress in the research on the activation of persulfate by heterogeneous iron-based catalysts is reviewed from two aspects, in terms of synthesized catalysts (Fe0, Fe2O3, Fe3O4, FeOOH) and natural iron ore catalysts (pyrite, magnetite, hematite, siderite, goethite, ferrohydrite, ilmenite and lepidocrocite) focusing on efforts made to improve the performance of catalysts. The advantages and disadvantages of the synthesized catalysts and natural iron ore were summarized. Particular interests were paid to the activation mechanisms in the catalyst/PS/pollutant system for removal of organic pollutants. Future research challenges in the context of field application were also discussed.

Microplastics and nanoplastics released from injection syringe, solid and liquid dimethylpolysiloxane (PDMS).

For a plastic syringe, a stopper at the end of plunger is usually made of polydimethylsiloxane (PDMS, and co-ingredients). To reduce friction and prevent leakage between the stopper and barrel, short chain polymer of liquid PDMS is also used as lubricant. Consequently, an injection process can release solid PDMS debris from the stopper and barrel, and liquid PDMS droplets from the lubricant, both of which are confirmed herein as solid and liquid micro(nano)plastics. From molecular spectrum perspective to directly visualise those micro(nano)plastics, Raman imaging was employed to analyse hundreds-to-thousands of spectra (hyper spectrum or hyperspectral matrix) and significantly enhance signal-to-noise ratio. From morphology perspective to provide high resolution of image, scanning electron microscopy (SEM) was engaged to cross-check with Raman images and increase assignment / quantification certainty. The weak Raman imaging signal of nanoplastics was extracted using image deconvolution algorithm to remove the background noise and average the signal variation. To increase the result's representativeness and avoid quantification bias, multiple syringes were tested and multiple areas were randomly scanned toward statistical results. It was estimated that thousands of microplastics and millions of nanoplastics of solid/liquid PDMS might be injected when using a plastic syringe of 1 mL. Overall, Raman imaging (along with algorithm and SEM) can be helpful for further research on micro(nano)plastics, and it should be cautious to use plastic syringe due to the increasing concern on the emerging contamination of not only solid but also liquid micro(nano)plastics.

Ultrasonic degradation of per-and polyfluoroalkyl substances (PFAS), aqueous film-forming foam (AFFF) and foam fractionate (FF).

The ubiquitousness of per- and polyfluoroalkyl substances (PFAS) is a big concern and PFAS remediation is urgently needed such as via degradation. While previous studies have explored ultrasonic degradation of PFAS, work evaluating the operational parameters is rare, especially concerning real wastes such as aqueous film-forming foam (AFFF) and foam fractionate (FF). This study investigates the key operational parameters affecting the degradation efficiency of PFAS, encompassing ultrasonication frequency (580-1144 kHz), power intensity (125-187.5 W), initial concentration (0.08-40 ppm), treatment duration (0.5-3 h), sample volume (100-500 mL), and PFAS structure (perfluorooctanoic acid or PFOA; perfluorooctane sulfonate or PFOS; 6:2 fluorotelomer sulfonate or 6:2 FTS). The defluorination kinetics is different from the removal/degradation kinetics due to the generation of degradation intermediates, suggesting the complex degradation mechanism, which should be evaluated to close the mass balance effectively. Notably, the optimised ultrasonic system achieves ∼125%/∼115% defluorination in AFFF/FF example wastes (compared to ∼65%/∼97% removal) despite their complex composition and the involvement of total oxidizable precursor (TOP) assay. In the meantime, a few new PFAS are detected in the post-treatments, including perfluorohexane sulfonic acid (PFHxS) and 10:2 fluorotelomer sulfonate (10:2 FTS) in the AFFF, and perfluorooctane sulfonamide (FOSA) and 8:2 fluorotelomer sulfonate (8:2 FTS) in the FF, again suggesting the complex degradation mechanism. Overall, ultrasonication is effective to degrade PFAS real example wastes, advancing its potential for scale-up applications.

Synthesised and modified zeolite for effective management of beryllium contaminants in aqueous media under different conditions.

The effective management of beryllium (Be) in solution is not well established. In this study, zeolite was synthesised from coal fly ash (CFA) and further modified to enhance Be sorption. Results indicated zeolite NaP1 was effectively synthesised, and cross-linked chitosan was grafted in/on the zeolite structure during modification. The Brunauer, Emmett, and Teller (BET) surface area substantially increased from 1.05 m2/g in CFA to 94.0 m2/g in the synthesised zeolite (SZ). Furthermore, the modified zeolite (MZ) showed improved functionality as a reactive site for Be sorption. A comparative sorption study revealed inferior sorption (11.3 %) and higher desorption (56.1 %) of Be using CFA than the sorption using SZ (93.0 % sorption, 2.9 % desorption) and MZ (93.0 % sorption, 1.5 % desorption). Consequently, SZ and MZ exhibited higher sorption efficacy than commercial zeolite (57.4 %) and other commercial sorbents. At an experimental pH of 5.5 [relevant to the pH of Little Forest Legacy Waste Site (LFLS) soil, a representative site for potential Be contamination], MZ showed higher sorption than SZ. The higher sorption in MZ resulted from its elevated ligand complexation [with nitrogen (N), phosphorous (P), and oxygen (O)] and some ion exchange (with Na+, -NH3+, and H+ ions) mechanisms. Moreover, increased sorption (up to 99 %) was observed using colloidal soil solution (CSS) collected from LFLS soil to simulate field conditions after extensive rainfall. Different environmental factors (e.g. pH, temperature, time, CSS, concentrations of sorbate, and sorbent) regulated Be sorption. The sorption mechanism was best described by the Langmuir model, and the pseudo-second-order kinetic model (R2 = 0.999). Moreover, the sorption reaction was spontaneous (ΔG = -Ve), enthalpically, and entropically influenced. Desorption hysteresis (ndesorption/nsorption < 1) suggested irreversible sorption, and the chemisorption mechanism of Be was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis.

Effects of source materials on desorption kinetics of carcinogenic PAHs from contaminated soils.

Research investigating the desorptive behaviour of PAHs from contaminated soils often overlooked the effects of source materials, especially coal tar and coal tar pitch and materials alike. In this study, a refined experimental approach was adopted to establish a simple-to-complex continuum of systems that allow the investigation of desorption kinetics of benzo(a)pyrene (BaP) and 3 other carcinogenic PAHs (cPAHs) over an incubation period of 48 d. By comparing the modelled desorption parameters, elucidation of the effects of PAH source materials on their desorptive behaviour was achieved. Desorption of cPAHs from coal tar and pitch was enhanced when they were added to soils, with rapidly desorbing fraction (Frap) of BaP increased from 0.68% for pitch to 1.10% and 2.66% for pitch treated soils, and from 2.57% for coal tar to 6.24% for coal tar treated soil G and 8.76% for coal tar treated sand (1 d). At 1 d, desorption of target cPAHs from solvent and source material spiked soils generally followed the order of solvent > coal tar > pitch. Increases in Frap of cPAHs were observed in coal tar-treated soils after 48 d soil incubation (0.33%-1.16% for soil M, p ≥ 0.05, 6.24%-9.21% for soil G, p < 0.05) and was attributed to the continuous migration of coal tar as a non-aqueous phase liquid (NAPL) into soil pore structures. Slow desorption was dominated by source materials, whereas the extents and rates of rapid desorption (Frap and krap) were more controlled by the quantity of soil organic matter (SOM), rather than quality of SOM (as in solvent-spiked soils). The results of this study challenged the role of PAH source materials as 'sinks' and led to the proposed roles of coal tar and pitch and source materials alike as 'reservoirs' with a risk-driven perspective.

Review and Perspective: Gas Separation and Discrimination Technologies for Current Gas Sensors in Environmental Applications.

Presently, numerous state-of-the-art approaches are being adapted for gas sensing and monitoring. These include hazardous gas leak detection as well as ambient air monitoring. Photoionization detectors, electrochemical sensors, and optical infrared sensors are a few of the commonly widely used technologies. Extensive reviews on the current state of gas sensors have been summarized. These sensors, which are either nonselective or semiselective, are affected by unwanted analytes. On the other hand, volatile organic compounds (VOCs) can be heavily mixed in many vapor intrusion situations. To determine the individual VOCs in a highly mixed gas sample using nonselective or semiselective gas sensors, gas separation and discrimination technologies are highly warranted. These technologies include gas permeable membranes, metal-organic frameworks, microfluidics and IR bandpass filters for different sensors, respectively. The majority of these gas separation and discrimination technologies are currently being developed and evaluated in laboratory-controlled environments and have not yet been extensively utilized in the field for vapor intrusion monitoring. These technologies show promise for continued development and application in the field for more complex gas mixtures. Hence, the present review focuses on the perspectives and a summary of the existing gas separation and discrimination technologies for the currently popular reported gas sensors in environmental applications.

Rapid on-site detection of underground petroleum pipeline leaks and risk assessment using portable gas chromatography-mass spectrometry and solid phase microextraction.

Locating underground pipeline leaks can be challenging due to their hidden nature and variable terrain conditions. To sample soil gas, solid-phase microextraction (SPME) was employed, and a portable gas chromatography/mass spectrometry (GC/MS) was used to detect the presence and concentrations of petroleum hydrocarbon volatile organic compounds (pH-VOCs), including benzene, toluene, ethylbenzene, and xylene (BTEX). We optimized the extraction method through benchtop studies using SPME. The appropriate fibre materials and exposure time were selected for each BTEX compound. Before applying SPME, we preconditioned the soil vapour samples by keeping the temperature at around 4 °C and using ethanol as a desorbing agent and moisture filters to minimize the impact of moisture. To conduct this optimisation, airbags were applied to condition the soil vapour samples and SPME sampling. By conditioning the samples using this method, we were able to improve analytical efficiency and accuracy while minimizing environmental impacts, resulting in more reliable research data in the field. The study employed portable GC/MS data to assess the concentration distribution of BTEX in soil vapour samples obtained from 1.5 m below the ground surface at 10 subsurface vapour monitoring locations at the leak site. After optimization, the detection limits of BTEX were almost 100 µg/m3, and the measurement repeatabilities were approximately 5% and 15% for BTEX standards in the laboratory and soil vapour samples in the field, respectively. The soil vapour samples showed a hotspot region with high BTEX concentrations, reaching 30 mg/m3, indicating a diesel return pipeline leak caused by a gasket failure in a flange. The prompt detection of the leak source was critical in minimizing environmental impact and worker safety hazards.

A Comprehensive Review of the Current Progress of Chromium Removal Methods from Aqueous Solution.

Chromium (Cr) exists in aqueous solution as trivalent (Cr3+) and hexavalent (Cr6+) forms. Cr3+ is an essential trace element while Cr6+ is a dangerous and carcinogenic element, which is of great concern globally due to its extensive applications in various industrial processes such as textiles, manufacturing of inks, dyes, paints, and pigments, electroplating, stainless steel, leather, tanning, and wood preservation, among others. Cr3+ in wastewater can be transformed into Cr6+ when it enters the environment. Therefore, research on Cr remediation from water has attracted much attention recently. A number of methods such as adsorption, electrochemical treatment, physico-chemical methods, biological removal, and membrane filtration have been devised for efficient Cr removal from water. This review comprehensively demonstrated the Cr removal technologies in the literature to date. The advantages and disadvantages of Cr removal methods were also described. Future research directions are suggested and provide the application of adsorbents for Cr removal from waters.

Understanding Iron Impurities in Australian Kaolin and Their Effect on Acid and Heat Activation Processes of Clay.

Iron impurities present in the crystal structure of kaolin minerals or in accessory species are frequently encountered in clay deposits. As knowledge of the location and states of the iron is crucial when modifying the properties of clays by activation, it is important that new deposits are well characterized in terms of the amount and location of this metal. The Western Australia Noombenberry deposit has been identified as a large resource of kaolin composed largely of halloysite and kaolinite. We sampled six from one hundred drill holes and grouped them according to major mineral and iron impurities. First, we characterized them to understand the source of iron impurities. Then, we performed three physicochemical activation processes of samples involving acid treatment (by 3 M HCl), heating at 600 °C, and a combination of both. State-of-the-art tools, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and nuclear magnetic resonance, revealed the properties of kaolin, iron impurities, and the changes incurred after activation. The iron impurities were found to be linked to non-kaolin minerals, i.e., in mica or illite. Once the iron was removed mainly by acid activation, the surface area, pore volume, and negative surface charges increased, and that was significant for halloysite-rich samples. These properties helped adsorb N2 gas compared to the raw kaolin. Therefore, knowing the iron's location and states in associated mineral species and their dissolution/retention may expand the scope of material development for gas adsorption. They are also useful in other applications like clay purification and adsorbent or additive formulations.

Accelerated transformation of plastic furniture into microplastics and nanoplastics by fire.

Numerous plastic items are known to gradually degrade and release microplastics and nanoplastics under certain conditions, which can be significantly accelerated by fire combustion. Unfortunately there is a limited knowledge about this burning process because the characterisation on microplastics and nanoplastics is still a challenge. In this study, an outdoor plastic chair is subjected to a combustion process, the change in the surface functional groups (due to different degree of burning) and the release of microplastics and nanoplastics are investigated. During the combustion process, the plastic is molten, burned and deposited on solid surfaces including concrete, stone and glass. Scanning electron microscopy (SEM) results show that the peeling off the deposited plastic generates a large number of fragments. Through Raman imaging, these fragments are characterised as polypropylene (PP) microplastics and nanoplastics due to appearance of characteristic peaks. To further increase the sensitivity, several algorithms are tested and optimised, including logic-based, non-supervised principal component analysis (PCA)-based, algebra-based and their hybrids (to intentionally correct the non-supervised PCA) to enable the effective extraction of the key information towards plastics characterisation, particularly by distinguishing the signal from the background noise towards the visualisation of the different degrees of burning. Based on the findings from Raman imaging and SEM, it is estimated that tens of microplastics and nanoplastics are created per µm2. Overall Raman imaging can be a suitable approach to characterise the microplastics and nanoplastics in a complex background, such as the fire-burned plastic items.

Environmental chemistry response of beryllium to diverse soil-solution conditions at a waste disposal site.

This study evaluated how the variation in different sorption conditions of beryllium (Be) in soil-water systems (electrolytes; ionic strengths; competing, counter, and co-existing ions; concentrations of Be and soil; and temperature) affected Be's environmental behaviour. For this reason, potentially contaminated soil was collected from a legacy waste site near Sydney, Australia. The sorption-desorption plateau for Be was found at >12.5 g L-1 (soil/solution), considering higher sorption and limited desorption. Variable surface charges developed by different added ions (competing ions, counter ions, and co-existence of all ions) were not always correlated with Be sorption. However, effects of added ions in Be sorption (increased by counter ions and decreased by competing ions) primarily occurred at low pH, with no noticeable changes at pH > 6 due to the hydration and precipitation behaviour of Be at higher pH. Both laboratory data and modelling indicated the substantial effect of counter ions on increased sorption of Be. Relatively higher amounts of sorption under the co-existence of all added ions were suggested from synergistic actions. Sorption was favourable (KL > 0, and 0 < RL < 1) across all concentrations and temperatures at pH 5.5, and high retention (84-97%) occurred after four desorption cycles indicated specific sorption. The sorption process was exothermic (ΔH > -43 kJ mole-1), while desorption was endothermic (ΔH > +78.4 kJ mole-1). All sorption-desorption reactions were spontaneous (ΔG = -Ve), and executed without any structural deformation (ΔS = nearly zero) of soil particles. However, the effect of temperature on desorption was influenced by the concentrations of Be. Higher retention and different sorption-desorption parameters (Kd-desorption > Kd-sorption; Kf-desorption > Kf-sorption; ndesorption/nsorption < 1) indicate limited mobility of Be and the presence of desorption hysteresis in the studied soil under the experimental conditions.

Predicting the bioremediation potential of earthworms of different ecotypes through a multi-biomarker approach.

Earthworms are attracting the attention of bioremediation research because of their short-term impact on pollutant fate. However, earthworm-assisted bioremediation largely depends on the earthworm sensitivity to target pollutants and its metabolic capacity to break down contaminants. The most studied species in soil bioremediation has been Eisenia fetida, which inhabits the soil surface feeding on decomposing organic residues. Therefore, its bioremediation potential may be limited to organic matter-rich topsoil. We compared the detoxification potential against organophosphate (OP) pesticides of three earthworm species representative of the main ecotypes: epigeic, anecic, and endogeic. Selected biomarkers of pesticide detoxification (esterases, cytochrome P450-dependent monooxygenase, and glutathione S-transferase) and oxidative homeostasis (total antioxidant capacity, glutathione levels, and glutathione reductase [GR] and catalase activities) were measured in the muscle wall and gastrointestinal tract of E. fetida (epigeic), Lumbricus terrestris (anecic) and Aporrectodea caliginosa (endogeic). Our results show that L. terrestris was the most suitable species to bioremediate OP-contaminated soil for the following reasons: 1) Gut carboxylesterase (CbE) activity of L. terrestris was higher than that of E. fetida, whereas muscle CbE activity was more sensitivity to OP inhibition than that of E. fetida, which means a high capacity to inactivate the toxic oxon metabolites of OPs. 2) Muscle and gut phosphotriesterase activities were significantly higher in L. terrestris than in the other species. 3) Enzymatic (catalase and GR) and molecular mechanisms of free radical inactivation (glutathione) were 3- to 4-fold higher in L. terrestris concerning E. fetida and A. caliginosa, which reveals a higher potential to keep the cellular oxidative homeostasis against reactive metabolites formed during OP metabolism. Together with biological and ecological traits, these toxicological traits suggest L. terrestris a better candidate for soil bioremediation than epigeic earthworms.

Iron-modified biochar derived from sugarcane bagasse for adequate removal of aqueous imidacloprid: sorption mechanism study.

Adsorption has been considered as a promising remediation technology to separate organic and inorganic agrochemicals from contaminated soil and water. Low-cost adsorbents, including waste derived materials, clay composites, biochar, and biochar modified materials, have attracted enormous attention for the removal of organic contaminants, including pesticides. In this study, iron-modified base-activated biochar (FeBBC) was prepared by pyrolysis (at 400 °C for 1 h) of iron-doped base (KOH) activated sugarcane bagasse for the removal of a widely used insecticide, namely imidacloprid (IMI) from water. The maximum adsorption capacity of the adsorbent (FeBBC) was calculated as 10.33 (± 1.57) mg/g from Langmuir isotherm model. The adsorbents could remove up to ~ 92% of IMI from aqueous solution at 23.8 mg/L IMI. Experimental data fitted well with the Freundlich model and pseudo-second-order model, demonstrating physisorption, as well as chemosorption, contributed to the sorption process. Even at highly acidic/basic solution pH, the FeBBC could remove substantial amount of IMI demonstrating hydrophobic interaction and pore diffusion play vital role for removal of IMI. The slight improving of IMI sorption with increasing solution pH indicated the sorption was also facilitated through ionic interaction alongside physical sorption. However, physical sorption including hydrophobic interaction and pore-filling interaction plays a vital role in the sorption of IMI.

Zinc Biofortification through Basal Zinc Supply Reduces Grain Cadmium in Mung Beans: Metal Partitioning and Health Risks Assessment.

Grain zinc (Zn) biofortification with less cadmium (Cd) accumulation is of paramount importance from human health and environmental point of view. A pot experiment was carried out to determine the influence of Zn and Cd on their accumulations in Mung bean tissues (Vigna radiata) in two contrast soil types (Dermosol and Tenosol). The soil types with added Zn and Cd exerted a significant effect on translocation and accumulation of metals in different tissues. The accumulation of Zn and Cd was higher for Tenosol than that for Dermosol. At control, the concentration of Cd followed a pattern, e.g., root > stem > petiole > pod > leaflet > grain for both soils. A basal Zn supply (5 mg kg−1) increased the grain Zn concentration to a significant amount (up to 67%). It also reduced Cd accumulation in tissues, including grains (up to 34%). No non-carcinogenic effect was observed for either the children or the adults as the EDI and PTDI values were below the safety limit; however, the ILCR values exceeded the safety limit, indicating the possibility of some carcinogenic effects. Added Zn helped to reduce the carcinogenic and non-carcinogenic health risks on humans.

Microplastics and nanoplastics released from a PPE mask under a simulated bushfire condition.

Due to COVID-19, large amounts of personal protective equipment (PPE) have been used, and many PPE units are made of plastics, such as face masks. The masks can be burned naturally in a bushfire or artificially at the incineration plants, and release microplastics and nanoplastics from the mask plastic fibres. A fire can cause the plastic, such as polypropylene (PP) fibres, to be molten and stick to the solid surface, such as glass, soil, concrete or plant, as films or islands, due to the binding property of the molten plastic material. Once the films or islands are peeled off in the processes such as weathering, ageing, or treatment and clean-up, there are residuals leftover, which are identified as nanoplastics and microplastics via Raman imaging, with the significant release amount of ~1100 nanoplastics / 10 µm2 or ~11 billion / cm2, and ~50 microplastics / 420 µm2 or ~12 million / cm2. Moreover, surface group is deviated on the plastic surface, which can also be distinguished and visualised as well via Raman imaging, down to nano size. This test validates the Raman imaging approach to capture microplastics and nanoplastics, and also provides important information about the fate and transportation of PPE mask in the environment, particularly when subjected to a fire. Overall, Raman imaging can be an effective option to characterise the microplastics and nanoplastics, along with the deviated surface group.

Role of beryllium in the environment: Insights from specific sorption and precipitation studies under different conditions.

In this study, we examined factors influencing the environmental behaviour of Be, specifically considering soils collected from a legacy radioactive waste disposal site near Sydney (Australia). The precipitation study showed the formation of Be(OH)2 (amorphous) from ICP standard solution, but a mixture of Be(OH)2 (alpha), Be(OH)2 (beta) and ternary Na/S-Be (ΙΙ)-OH(s) solid phase were formed from BeSO4 solutions. The precipitation of Be started at relatively lower pH at higher concentrations than at the lower Be concentration as indicated by both laboratory data and simulation. Across the pH range, the Be sorption curve was divided into three phases, these being pH 3-6, pH 6-10, and pH > 10, within which sorption of Be with soil was 9-97%, 90-97%, and 66-90%, respectively. Beryllium solubility was limited at pH > 7, but a sorption study with soil showed chemisorption under both acidic and alkaline pH (pH 5.5 and 8) conditions, which was confirmed by FTIR and XPS analysis. At pH 5.5 (specifically relevant to the study site), sorption of Be was 72-95%, in which 77% and 46% Be was respectively sorbed by separated fulvic and humic acid fractions. The irreversible chemisorption mechanism was controlled by SOM at higher pH, and by metal oxyhydroxides at lower pH. Both organic and inorganic components synergistically influence the specific chemisorption of Be at the intermediate pH 5.5 of field soil.

Arsenic concentrations in soil, water, and rice grains of rice-growing areas of Punjab, Pakistan: multivariate statistical analysis.

Arsenic (As), a class-A human carcinogen, is ubiquitously present in the earth's crust and soil and may enter the air, water, and surface environments through different natural and anthropogenic sources. In this experiment, soil, irrigation water, and rice grains were sampled from conventional rice-growing areas of Punjab, Pakistan. Soil samples were collected from 0 to 15 cm surface soil of rice growing fields, and rice grains were collected from the same field at crop maturity. Irrigation water samples were collected from the source used to irrigate the respective rice fields. Coordinates of sampling locations were noted using a global positioning system, and a locations map was made using ArcGIS. Soil samples were digested in a microwave digester using aqua regia, and plant samples were block digested using nitric acid. Arsenic concentration was determined using an inductively coupled plasma mass spectrometer coupled with an auto-sampler and integrated samples introduction system. The mean concentration of As in rice grains, soil, and water samples was found within the safe limit set by WHO except for a sample from Narowal (148.54 µg l-1) that exceeded the irrigation water standard limit, i.e., 100 µg l-1 for irrigation water. Principal component analysis was performed to reduce the multidimensional space of variables and samples. Through the calculations of estimated daily intake, it has been revealed that the As levels measured in this study would only contribute a small amount (less than 5%) of the total recommended daily intake allowance.

Air pollution from gas refinery through contamination with various elements disrupts semiarid Zagros oak (Quercus brantii Lindl.) forests, Iran.

Soils and oak trees (Quercus brantii Lindl.) in Zagros forests are suffering from the air pollution caused by the Ilam Gas Refinery. Thus, for the first time, we investigated the contamination level of sulfur and trace elements in these ecosystems. Sampling of soil and tree leaves was carried out in different seasons of 2019 and at different distances from the gas refinery. The results showed that soils and leaves at the various distances compared with control distance (10,000 m) were more affected by the gas refinery. Distance from the pollution source and physicochemical properties of soils were the main factors affecting contamination of soil elements contents. The soils with pollution load indices (PLI) of 4.54 were in the highly polluted category. Sulfur was at highly polluted category in soils and were highly enriched in trees. The trees mainly absorbed studied elements via their aerial organs. Our findings indicated that oak trees with the highest value of metal accumulation index are influence tools for monitoring various elements in the polluted air produced by the gas refinery. It is recommended that the ecosystem components near the refinery be studied to accurately evaluate disorders in the food chain.

Photodegradation of modified petroleum impregnated bentonite mulch under the effects of solar radiation simulating the outdoor condition.

The objectives of this study were investigating the photodegradation of the polycyclic aromatic hydrocarbons (PAHs) in modified petroleum impregnated bentonite mulch through solar radiation, determining PAHs' translocation in the soils that underlay the mulch and finding a solution to prevent the uncontrolled release of petroleum into the environment. For this research, various formulated mulches were prepared: mulch no. 1 was a mixture of 5:1 sandy soil: natural bentonite + petroleum; mulch no. 2 composed a mixture of 5:1 sandy soil: modified bentonite + natural bentonite + petroleum; and mulch no. 3 composed a mixture of 5:1:0.5 ratio of sandy soil: natural bentonite: modified bentonite mixed with petroleum at a ratio of 1:1. PAHs in surface mulches and subsurface sandy soil were monitored over 5, 20, 40 and 80 days. The results demonstrated that PAHs undergo numerous changes over time because of sunlight. Photodegradation is the most dominant process for low molecular weight (LMW) PAHs (≤ 3 fused aromatic rings) and high molecular weight (HMW) PAHs (≥ 4 fused aromatic rings). HMW PAHs could be sequestrated strongly within the soil particles because of their higher aromaticity and lower polarity; they were more resilient in the soil matrices than LMW PAHs. Mulch no. 2 retained more PAHs compounds (p > 95%) than mulch nos. 1 and 3, which could be attributed to the retention of numerous PAHs in its interlayers, preventing its movement into the underlying soil, environment and atmosphere.

Beryllium in contaminated soils: Implication of beryllium bioaccessibility by different exposure pathways.

Inhalation exposure and beryllium (Be) toxicity are well-known, but research on bioaccessibility from soils via different exposure pathways is limited. This study examined soils from a legacy radioactive waste disposal site using in vitro ingestion (Solubility Bioaccessibility Research Consortium [SBRC], physiologically based extraction test [PBET], in vitro gastrointestinal [IVG]), inhalation (simulated epithelial lung fluid [SELF]) and dynamic two-stage bioaccessibility (TBAc) methods, as well as 0.43 M HNO3 extraction. The results showed, 70 ±â€¯4.8%, 56 ±â€¯16.8% and 58 ±â€¯5.7% of total Be were extracted (gastric phase [GP] + intestinal phase [IP]) in the SBRC, PBET, and IVG methods, respectively. Similar bioaccessibility of Be (~18%) in PBET-IP and SELF was due to chelating agents in the extractant. Moreover, TBAc-IP showed higher extraction (20.8 ±â€¯2.0%) in comparison with the single-phase (SBRC-IP) result (4.8 ±â€¯0.23%), suggesting increased Be bioaccessibility and toxicity in the gastrointestinal tract when the contamination derives from the inhalation route. The results suggested Be bioaccessibility depends on solution pH; time of extraction; soil reactive fractions (organic-inorganic); particle size, and the presence of chelating agents in the fluid. This study has significance for understanding Be bioaccessibility via different exposure routes and the application of risk-based management of Be-contaminated sites.