Release Of Contaminants Research Articles

Use of 3-Dimensional Printers in Educational Settings: The Need for Awareness of the Effects of Printer Temperature and Filament Type on Contaminant Releases.

Material extrusion-type fused filament fabrication (FFF) 3-D printing is a valuable tool for education. During FFF 3-D printing, thermal degradation of the polymer releases small particles and chemicals, many of which are hazardous to human health. In this study, particle and chemical emissions from 10 different filaments made from virgin (never printed) and recycled polymers were used to print the same object at the polymer manufacturer's recommended nozzle temperature ("normal") and at a temperature higher than recommended ("hot") to simulate the real-world scenarios of a person intentionally or unknowingly printing on a machine with a changed setting. Emissions were evaluated in a college teaching laboratory using standard sampling and analytical methods. From mobility sizer measurements, particle number-based emission rates were 81 times higher; the proportion of ultrafine particles (diameter <100 nm) were 4% higher, and median particle sizes were a factor of 2 smaller for hot-temperature prints compared with normal-temperature prints (all p-values <0.05). There was no difference in emission characteristics between recycled and virgin acrylonitrile butadiene styrene and polylactic acid polymer filaments. Reducing contaminant release from FFF 3-D printers in educational settings can be achieved using the hierarchy of controls: (1) elimination/substitution (e.g., training students on principles of prevention-through-design, limiting the use of higher emitting polymer when possible); (2) engineering controls (e.g., using local exhaust ventilation to directly remove contaminants at the printer or isolating the printer from students); (3) administrative controls such as password protecting printer settings and establishing and enforcing adherence to a standard operating procedure based on a proper risk assessment for the setup and use (e.g., limiting the use of temperatures higher than those specified for the filaments used); and (4) maintenance of printers.

Sediment Remediation with New Composite Sorbent Amendments to Sequester Phosphorus, Organic Contaminants, and Metals.

This study tested two sediment amendments with active sorbents: injection of aluminum (Al) into sediments and thin-layer capping with Polonite (calcium–silicate), with and without the addition of activated carbon (AC), for their simultaneous sequestration of sediment phosphorus (P), hydrophobic organic contaminants (HOCs), and metals. Sediment cores were collected from a eutrophic and polluted brackish water bay in Sweden and incubated in the laboratory to measure sediment-to-water contaminant release and effects on biogeochemical processes. We used diffusive gradients in thin-film passive samplers for metals and semi-permeable membrane devices for the HOC polychlorinated biphenyls and polycyclic aromatic hydrocarbons. Al injection into anoxic sediments completely stopped the release of P and reduced the release of cadmium (Cd, −97%) and zinc (Zn, −95%) but increased the sediment fluxes of PAH (+49%), compared to the untreated sediment. Polonite mixed with AC reduced the release of P (−70%), Cd (−67%), and Zn (−89%) but increased methane (CH4) release. Adding AC to the Al or Polonite reduced the release of HOCs by 40% in both treatments. These results not only demonstrate the potential of innovative remediation techniques using composite sorbent amendments but also highlight the need to assess possible ecological side effects on, for example, sedimentary microbial processes.

Plant and Plant Associated Microflora: Potential Bioremediation Option of Indoor Air Pollutants

Indoor air pollution is a significant problem today because the release of various contaminants into the indoor air has created a major health threat for humans occupying indoors. Volatile Organic Compounds (VOCs) are pollutants released into the environment and persist in the atmosphere due to its low boiling point values. Various types of indoor activities, sources, and exposure to outdoor environments enhance indoor VOCs. This poor indoor air quality leads to adverse negative impacts on the people in the indoor environment. Many physical and chemical methods have been developed to remove or decompose these compounds from indoors. However, those methods are interrupted by many environmental and other factors in the indoor atmosphere, thus limit the applications. Therefore, there is a global need to develop an effective, promising, economical, and environmentally friendly alternatives to the problem. The use of the plant and associated microflora significantly impact reducing the environmental VOC gases, inorganic gases, particulate matter, and other pollutants contained in the air. Placing potted plants in indoor environments not only helps to remove indoor air pollutants but also to boost the mood, productivity, concentration, and creativity of the occupants and reduces stress, fatigue, sore throat, and cold. Plants normally uptake air pollutants through the roots and leaves, then metabolize, sequestrate, and excrete them. Plant-associated microorganisms help to degrade, detoxify, or sequestrate the pollutants, the air remediation, and promote plant growth. Further studies on the plant varieties and microorganisms help develop eco-friendly and environmentally friendly indoor air purifying sources.

Vertical and Lateral Distribution of Heavy Metals in the Euphrates River Sediments between Heet and Fallujah, Western Iraq

In recent decades, significant attention has been paid to heavy metal contamination as a dangerous environmental problem because of the toxicity, abundance, persistence and bioaccumulation of these elements (Chen et al., 2016,) (Islam et al., 2017 and ) (Jin et al., 2019). In general, the contamination state of the environment is evaluated by the total concentration of heavy metals (Kanda et al., 2018). The riverine sediments are considered as the main basins for various pollutants following the largely uncontrolled discharge of contamination resulting from human activities and geogenic processes (Liu et al., 2018). The sediment contamination is an important indicator of environmental variation as a result of anthropogenic influence (Gao et al., 2019). River sediments serve as not only a major sink and carrier of heavy metals but also as potential sources of secondary pollution, which can reflect their contamination level (Tang et al., 2014 and ) (Hsu et al., 2016). The heavy metals are released into the aquatic environments from geogenic and anthropogenic sources. The geogenic sources include chemical leaching of bedrock, water drainage basins and runoff from banks (Raj et al., 2017). The anthropogenic sources of heavy metals pollution in aquatic systems include mining activities, industrial wastes disposal and pesticides use, (Chakravarty &amp; Patgiri, 2009). The heavy metals pollution of sediments is an indicator of the aquatic systems water quality (Zhao et al., 2012). The heavy metal distribution in sediments and pollution levels supplies a base for consideration of sediments treatment methods and evaluation of the potential releasing of heavy metals into water and transport downstream (Nawrot et al., 2020). The vertical and spatial distribution of heavy metals and pollution levels have been evaluated in sediments of many world rivers, such as the Yinma River, China (Guan et al., 2018), the Voghji River, Armenia (Gabrielyan et al., 2018), the Barigui River, Brazil (Machado et al., 2017), the Harazdan River, Armenia (Petrosyan et al., 2019), the Thames River, the UK (Vane et al., 2020), the Yang River, China (Tang et al., 2020), and the Lu Lu River, China (Ye et al., 2020). The spatial distribution of heavy metals in sediments of the Euphrates River in Iraq has been investigated by many authors (Issa &amp; Qanbar, 2016); (Al-Taher et al., 2020); and (Hussain &amp; Al-Jaberi, 2020). The spatial variation of heavy metal concentrations in sediments of the Euphrates River along the studied area between Heet and Ramadi Cities has been studied by (Al-Bassam &amp; Al-Mukhtar, 2008) and (Salah et al., 2012). The aim of the study is to investigate how heavy metals are laterally and vertically distributed in sediments of the given study area of Euphrates River between Heet and Fallujah Cities. This study represents the first attempt to investigate the vertical distribution of heavy metals in the Euphrates River sediments.

Unraveling the Underlying Heavy Metal Detoxification Mechanisms of Bacillus Species.

The rise of anthropogenic activities has resulted in the increasing release of various contaminants into the environment, jeopardizing fragile ecosystems in the process. Heavy metals are one of the major pollutants that contribute to the escalating problem of environmental pollution, being primarily introduced in sensitive ecological habitats through industrial effluents, wastewater, as well as sewage of various industries. Where heavy metals like zinc, copper, manganese, and nickel serve key roles in regulating different biological processes in living systems, many heavy metals can be toxic even at low concentrations, such as mercury, arsenic, cadmium, chromium, and lead, and can accumulate in intricate food chains resulting in health concerns. Over the years, many physical and chemical methods of heavy metal removal have essentially been investigated, but their disadvantages like the generation of chemical waste, complex downstream processing, and the uneconomical cost of both methods, have rendered them inefficient,. Since then, microbial bioremediation, particularly the use of bacteria, has gained attention due to the feasibility and efficiency of using them in removing heavy metals from contaminated environments. Bacteria have several methods of processing heavy metals through general resistance mechanisms, biosorption, adsorption, and efflux mechanisms. Bacillus spp. are model Gram-positive bacteria that have been studied extensively for their biosorption abilities and molecular mechanisms that enable their survival as well as their ability to remove and detoxify heavy metals. This review aims to highlight the molecular methods of Bacillus spp. in removing various heavy metals ions from contaminated environments.

Pyrolysis Solves the Issue of Organic Contaminants in Sewage Sludge while Retaining Carbon—Making the Case for Sewage Sludge Treatment via Pyrolysis

Contaminants of emerging concern are a growing burden for sewage sludge recycling. Pyrolysis of sewage sludge could be a solution. Yet, the product of sewage sludge pyrolysis (biochar) is currently not included on the list of eligible fertilizers in the new EU Fertilising Products Regulation. This was justified by insufficient evidence for organic contaminant removal through pyrolysis. Here I summarize the current evidence on this topic covering 20 studies and more than 100 different organic pollutants. The studies demonstrate that pyrolysis reduces the concentration of well-established contaminants, such as PAHs, PCBs, and dioxins, but also emerging ones, i.e., pharmaceuticals, hormones, antibiotics, antibiotic resistance genes, antimicrobials, microplastics, and per- and polyfluoroalkyl substances (PFAS) with very high efficacy (>95 to >99% in most cases). After pyrolysis, the levels of organic contaminant in biochar were typically below the limit of detection. Furthermore, modern pyrolysis units prevent environmental release of contaminants that are only vaporized and not decomposed during pyrolysis by internal combustion of pyrolysis liquids and gases. The evidence for effective organic contaminant removal through pyrolysis is comprehensive, covering all relevant groups of compounds. This and its potential as negative emission technology makes pyrolysis of sewage sludge a great opportunity for sustainable and safe nutrient recycling.

Novel nanoporous membranes of bio-based cellulose acetate, poly(lactic acid) and biodegradable polyurethane in-situ impregnated with catalytic cobalt nanoparticles for the removal of Methylene Blue and Congo Red dyes from wastewater

The discharge of contaminants of emerging concern (CECs) into water streams is becoming a major global issue. Herein, novel nanoporous membranes of bio-based cellulose acetate, poly(lactic acid) and biodegradable polyurethane in-situ impregnated with catalytic cobalt nanoparticles were synthesized and tested for the removal of Methylene Blue (MB) and Congo Red (CR) dyes from water. The bio-based polymers supported the formation of a network hydrogen bonding among different functional groups as confirmed using FTIR, which improved the membrane stability. Porogen was used to create nanopores within the film bulk, which were used to impregnate the membranes with cobalt nanoparticles that ensured the adsorption, degradation and removal of the hazardous contaminants from polluted water. Up to almost 60% of each of MB and CR were removed under UV irradiation, while adsorption was well described by the Linear and Langmuir isotherms, respectively. The thermodynamic study showed that the adsorption process is dissociative and, thus, involves photocatalytic dye degradation. Both dyes exhibited the same overall rate of adsorption, but CR showed a faster diffusion rate as predicted by the intra-particle diffusion model. Loading the nanoparticles into a biopolymeric matrix could potentially reduce the risks of their environmental release as free particles in water effluents.

Leaching Behaviour of Construction and Demolition Wastes and Recycled Aggregates: Statistical Analysis Applied to the Release of Contaminants

Construction and demolition wastes represent a primary source of new alternative materials which, if properly recovered, can be used to replace virgin raw materials partially or totally. The distrust of end-users in the use of recycled aggregates is mainly due to the environmental performance of these materials. In particular, the release of pollutants into the surrounding environment appears to be the aspect of greatest concern. This is because these materials are characterized by a strong heterogeneity which can sometimes lead to contaminant releases above the legal limits for recovery. In this context, an analysis of the leaching behaviour of both CDWs and RAs was conducted by applying a statistical analysis methodology. Subsequently, to evaluate the influence of the particle size and the volumetric reduction of the material on the release of contaminants, several experimental leaching tests were carried out according to the UNI EN 12457-2 and UNI EN 12457-4 standards. The results obtained show that chromium, mercury, and COD are the most critical parameters for both CDWs and RAs. Moreover, the material particle size generally affects the release of contaminants (i.e., finer particles showed higher releases), while the crushing process does not always involve higher releases than the sieving process.

Pollution Biomarkers in the Framework of Marine Biodiversity Conservation: State of Art and Perspectives

Marine biodiversity is threatened by several anthropogenic pressures. Pollution deriving from the discharge of chemical contaminants in the sea represents one of the main threats to the marine environment, influencing the health of organisms, their ability to recover their homeostatic status, and in turn endangering biodiversity. Molecular and cellular responses to chemical pollutants, known as biomarkers, are effect-based methodologies useful for detecting exposure and for assessing the effects of pollutants on biota in environmental monitoring. The present review analyzes and discusses the recent literature on the use of biomarkers in the framework of biodiversity conservation. The study shows that pollution biomarkers can be useful tools for monitoring and assessment of pollution threat to marine biodiversity, both in the environmental quality monitoring of protected areas and the assessment of the health status of species at risk. Moreover, key areas of the research that need further development are suggested, such as the development of omics-based biomarkers specifically addressed to conservation purposes and their validation in the field, the extension of the biomarker study to a wider number of endangered species, and the development of organic guidelines for the application of the biomarker approach in support to conservation policies and management.

Bioaccumulation of Zn and 137Cs in Glauconomya virens (Linnaeus, 176) Upon Exposure to Sigle and Mixture of Zn or 137Cs and Salinity

This study aims to determine the effect of concentrations and salinity of seawater on the bioaccumulation of zinc and cesium in the Glauconomya virens. Salinity conditions and contaminant concentrations in the marine environment can change due to weather and other inputs. A biokinetic experiment was carried out using a single compartment approach that used radiotracer 65Zn and 137Cs. The experiments conducted were biota collection, acclimatization, bioaccumulation, and elimination. Acclimatization aims for the adaptation of biota in an experimental environment. Bioaccumulation was by placing the biota in an aquarium containing seawater media spiked by 65Zn, Zn, and 137Cs radiotracer contaminants. The elimination process was the release of contaminants from the body of the biota by placing them in clean and flowing seawater. The experimental results show that the uptake and elimination of Zn and Cs were influenced by these two parameters (water concentration and salinity). The highest value of Concentration Factor (CF) for Zn was 11.14 ml.g-1 under influences its concentration of 0.7 ppm in water. In the depuration process, Zn maintained by G virens were 39.44; 31.17; 23.62; and 23.92% after these organisms accumulate this element from seawater containing 0.1; 0.3, 0.5, and 0.7 ppm, respectively. The highest of 137Cs under influences its concentration of 3 Bg.ml-1 reached 2.65 mL.g-1. The effect of salinity is directly proportional to the factor value of Zn and 137Cs concentration.

Investigation of Coatings, Corrosion and Wear Characteristics of Machined Biomaterials through Hydroxyapatite Mixed-EDM Process: A Review.

Together, 316L steel, magnesium-alloy, Ni-Ti, titanium-alloy, and cobalt-alloy are commonly employed biomaterials for biomedical applications due to their excellent mechanical characteristics and resistance to corrosion, even though at times they can be incompatible with the body. This is attributed to their poor biofunction, whereby they tend to release contaminants from their attenuated surfaces. Coating of the surface is therefore required to mitigate the release of contaminants. The coating of biomaterials can be achieved through either physical or chemical deposition techniques. However, a newly developed manufacturing process, known as powder mixed-electro discharge machining (PM-EDM), is enabling these biomaterials to be concurrently machined and coated. Thermoelectrical processes allow the migration and removal of the materials from the machined surface caused by melting and chemical reactions during the machining. Hydroxyapatite powder (HAp), yielding Ca, P, and O, is widely used to form biocompatible coatings. The HAp added-EDM process has been reported to significantly improve the coating properties, corrosion, and wear resistance, and biofunctions of biomaterials. This article extensively explores the current development of bio-coatings and the wear and corrosion characteristics of biomaterials through the HAp mixed-EDM process, including the importance of these for biomaterial performance. This review presents a comparative analysis of machined surface properties using the existing deposition methods and the EDM technique employing HAp. The dominance of the process factors over the performance is discussed thoroughly. This study also discusses challenges and areas for future research.

Biological responses in pesticide exposed lizards (Podarcis siculus)

The release of contaminants as herbicides, fungicides and insecticides into the environment has been listed as one of the six major contributors to the global decline of reptiles. Although reptiles may face severe risk from contaminants due to their ecology and physiology, they are currently less studied than other vertebrate groups. In the present work, we investigated if and how different types of field treatment (conventional and organic) affected the health status of Italian wall lizard (Podarcis siculus) individuals in central Italy. We chose a multi-biomarker approach that evaluated the biological responses of lizards to the treatment by means of AChE activity in the nervous system, biotransformation enzymes activities and oxidative stress in the liver, micronuclei frequency measured in the erythrocytes, and rate of intestinal parasitic infection. Our findings showed evidence of effects of treatment in conventional areas and between sexes with significant oxidative stress due to hydroxyl radicals, that caused DNA damage. No difference of intestinal parasite infections was found among treatments. Podarcis siculus seems to be a good bioindicator in ecotoxicological studies and potentially in risk assessment of pesticides, although further analyses in laboratory and in the field are needed to achieve more accurate quantification of specific pesticide effects in relation to known exposure history and to understand if other mechanisms were involved in the toxicity and detoxification process of pesticides for this species.

Impact assessment of ephemeral discharge of contamination downstream of two legacy base metal mines using environmental DNA

Mining and processing metalliferous ores can degrade the environment well beyond the footprint of the mine, particularly where on-site containment and post-mining remediation has been insufficient to prevent releases of solid and aqueous mine wastes. In this study, we investigated the potential of sediment and water chemistry coupled with environmental (e)DNA metabarcoding to evaluate discrete and cumulative ecological impacts of two legacy base metal (copper (Cu), zinc (Zn), lead (Pb)) mines (Peelwood and Cordillera) which discharge metals via ephemeral tributaries into perennial Peelwood Creek. Although the two mine streams exceeded Australian guidelines for sediment and freshwater quality for Cu, Zn and Pb, Peelwood Creek had relatively low sediment and water metal concentrations, suggesting a low potential for environmental toxicity. Although sediment and water chemistry defined the extent of biological impacts, metabarcoding showed that Peelwood and Cordillera mines had discrete impacts and Peelwood mine was the main source of contamination of Peelwood Creek. Metabarcoding showed that prokaryotes can be good indicators of metal contamination whereas eukaryotes did not reflect contamination impacts in Peelwood Creek. Metabarcoding results showed that benthic communities downstream of Cordillera mine were less impacted than those below Peelwood mine, suggesting that Peelwood mine should be considered for further remediation.

High salinity enhances the adsorption of 17α-ethinyl estradiol by polyethersulfone membrane: isotherm modelling and molecular simulation

The increasing occurrence of steroidal hormone micropollutant in the aquatic environment and their associated consequences have caused serious environmental concerns globally. Adsorptive removal of hormonal pollutants using polymeric membranes has been suggested but information on their performance in various environmental conditions is lacking. In this study, we examined the effect of salinity on the performance of polyethersulfone (PES) membrane to remove synthetic hormone 17α-ethinyl estradiol (EE2) from water. Our results show that an increase of salinity from 0 to 3% results in higher retention of EE2 onto PES membrane from 79.3 to 98.7%. The experimental results fit the Freundlich isotherm model better as compared to the Langmuir model. The Freundlich parameters n and Kf yielded the highest values at 3% salinity. The molecular simulation results suggest that a high salinity increases the binding energy between EE2 and PES membranes, promoting the PES-EE2 interaction through π–π interaction, hydrogen bonding and hydrophobic interaction. This study provides valuable information for improving design of specialised treatment facilities (in farming, pharmaceutical industries, etc.) to allow better removal of EE2 and other low-polar organic contaminants from water via a membrane-based sorption-elution method, and we recommend the inclusion of salinity as a factor in modelling the adsorption capacity of membranes to prevent the oversaturation of membrane and minimise the release of contaminants into the environment.

Synthesis of 2D NiFe2O4 nanoplates/2D Bi2WO6 nanoflakes heterostructure: An enhanced Z-scheme charge transfer and separation for visible-light-driven photocatalytic degradation of toxic pollutants

Water pollution is a worldwide concern due to excessive discharge of toxic contaminants to water streams. Effective treatment of organic pollutants in wastewater by utilizing visible-light is a promising method to resolve environmental problems. In the present work, we have demonstrated a facile one-step hydrothermal strategy for the synthesis of a binary NiFe2O4/Bi2WO6 heterostructured nanocomposite. Further, the utility towards photocatalytic degradation of tetracycline (TC) and methylene blue (MB) has been evaluated. The characterization results revealed that the two-dimensional (2D) Bi2WO6 nanoflakes were inserted upon 2D NiFe2O4 nanoplates, which enhanced the interfacial contact and improved visible-light absorption efficiency, resulting in excellent photogenerated charges separation and transfer. The NiFe2O4/Bi2WO6 heterostructured nanocomposite exhibited higher TC degradation (96.81%) in 96 min and MB degradation (99.16%) in 60 min than the pure samples and remained stable for four successive cycles. The apparent reaction rate constant (k) of 20 mg loading of Bi2WO6 over NiFe2O4 (NFBW-20) exhibited the best photocatalytic performance among the all prepared materials, which was 7.15 (TC) and 9.19 (MB) times that of pristine Bi2WO6, and 6.02 (TC) and 6.41 (MB) times that of pure NiFe2O4. Radical trapping experiments confirmed •O2−, and •OH radicals were critical active species in the degradation mechanism, which supports the Z-scheme photocatalytic mechanism. Mott–Schottky measurements were used determine the positions of the conduction and valence bands of the samples, and a possible photocatalytic mechanism for TC and MB degradation was proposed according to experimental results. This study offers a novel effective avenue to design efficient binary heterostructured nanocomposites with superior visible-light response for environmental remediations.

Inverse identification of pollution source release information for surface river chemical spills using a hybrid optimization model

To evaluate the liability of the spilled contaminant and to design comprehensive emergency response schemes, it is essential to estimate the contaminant source characteristic and identify where, when and how much the spilled contaminant is injected into a surface river. In this study, an effective pollution source inverse method is developed to reconstruct the release history of the injection location, time, and quantity, and provide appropriate emergency response schemes for dealing with surface river environmental pollution. The pollution source inverse method IGSAA is developed by an integration of genetic algorithm (IGA) and simulated annealing algorithm (SAA) in order to guarantee both the global searching ability and convergence speed. The pollution source inverse method IGSAA is then applied to a hypothetical study, comparing with the traditional GA-based and SAA-based methods, to verify the accuracy and efficiency of the contaminant source inverse, and to a trace study of Truckee River in west America to identify the contaminant source release history and characteristic under different scenarios. The pollution source inversion results can help decision-makers (DMs) to identify the contaminant source characteristics of a chemical spill, and carry out emergency disposal scheme for an emergency rescue in a quick response, and enhance the supervision and management ability for a real surface river system.

Assessment and sensitive analysis of biological water risks in water resources with application of classical mass transfer computations

Due to the urgent need for water in all parts of industrial or developing societies, water supply, and transmission facilities are suitable targets for biological risks. Given that even a short interruption in water supply and water supply operations has a great impact on daily activities in the community, the deliberate contamination of urban water resources has irreparable consequences in the field of public health, and the economy of society will follow. Unfortunately, most officials in the public health control departments in our country have received limited training in detecting accidental or intentional contamination of water resources and dealing with the spread of waterborne diseases both naturally and intentionally. For this reason, there is low preparedness in the responsible agencies to deal with waterborne diseases during biological risks. In the first step of this research, a review study has been conducted on water biological risks and operational strategies to deal with them. In the following, it has studied how Escherichia coli (E. coli) bacteria spread in aqueous media. In this regard, the kinetic model of the studied microorganism was analyzed based on the implementation of (Fick Law) in polar coordinates and the combination of (Dirac Distribution) with (Legendre polynomial) distribution. Finally, after studying the factors affecting the microbial pollutant emission coefficient, the effects of all three factors of linear velocity, linear motion time period, and angle of motion on the pollutant emission flux and biofilm diffusion time in the water supply network environment were investigated. Studies have shown that the linear velocity parameter of Escherichia coli with a nonlinear relationship has the greatest effects on the release of microbial contaminants.

Leachate composition of lead and cadmium ions from solidified mortar mixed with Nanosilica

Soils contaminated with Cd and Pb ions are a great problem that affects human health and the environment. Intending to decrease the environmental risk. Solidification/ stabilization (S/S) is one of the commonly used and economic remediation technologies to treat contamination by heavy metals in soils compared with other remediation technology. To understand the leaching mechanism from the (S/S) process, the EPA Semi-dynamic Tank Leaching method 1315 and unconfined compressive strength test was carried out to test the effectiveness and performance of the solidification process of contaminated sands with Pb and Cd ions by using ordinary Portland Cement locally produced and nanomaterial. Tow mix designs were performed on the contaminated sands at three different pollution concentrations and three ratios of synthesized Nanosilica from rice husk as additive replacement of cement. The Nanosilica as-prepared has amorphas form, average diameter equal to 52.83 nm and surface area around 618 m2/g. This paper discusses the effects of Nanosilica on leaching contamination from solidifying samples and compressive strength. The leaching rate of lead and cadmium ions from the test specimens demonstrated the effectiveness of nanoparticles in reducing the release of contaminant. Diffusion studies from the S/S matrixes indicated low and very low mobility of lead and cadmium ions respectively. For all test specimens, the mean leachability index was found to be higher than 9.

Comparing objects for human movement simulation regarding its air flow disturbance at local exhaust ventilation

The movement of people and other objects indoors may affect airflow patterns and velocities near local exhaust ventilation hoods, and consequently has influence on the hoods’ ability to remove locally emitted contaminants and on ventilation energy requirements. In this study, such disturbance effects have been studied experimentally and numerically, with the movements consisting of a human-sized plate, cylinder and detailed manikin, respectively, making back-and-forth movements near an exhaust hood. In the experimental part of the study, a 3-D sonic anemometer was used to measure air velocity in front of the hood opening. The numerical simulations used dynamic mesh to handle object movements. The numerical results were validated against the experimental ones and yielded supplementary results on the air flow field. The results show that the turbulence produced by the objects movements included marked air velocity peaks – both assisting and impeding the suction flow – in the near field of the exhaust hood. The generated turbulence, and particularly those peaks, proved substantially larger in the case of plate movement than with cylinder and manikin movement. Overall the results indicate that a moving cylinder represents human movement better than a moving plate, and thus that it’s better to use a cylinder in some test standards that now stipulate a plate as moving object. A Percentage of Negative Velocity (PNV) parameter was introduced for assessing the capture efficiency of the local exhaust system. The PNV represents the percentage of time that the air flow is directed away from the exhaust hood in an imagined point of contaminant release. The study includes test cases where the PNV values were significantly above zero, suggesting a strong effect on the capture efficiency of the exhaust hood. Human induced turbulence that cause such reverse air flows and overall impedes hood suction may be counteracted by enhanced exhaust flow rate, but then at higher energy consumption.

Negligible microbial heterotrophic quantitative contribution onto trace metals remobilization during marine sediment resuspension - insights from a Mediterranean urbanized bay

Marine sediments are a sink for trace metals but also a potential source during sediment resuspension events. Understanding the factor that regulates this uptake or release of contaminant is of prime importance. While the impact of abiotic processes has been widely studied, the quantitative influence of microbial activities on metal cycling during sediment resuspension events is still largely unknown. This study was designed to quantify such microbial contributions on the cycling of a suite of metals (Al, As, Ba, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Sb, Sr, Ti, Tl, U, V and Zn) and evaluate the specific contributions of heterotrophic micro-organisms originating from either the seawater or the sediment. For that purpose, the sediment and seawater were selectively sterilized using either autoclave (sediment) or filtration under 0.2 μm (seawater) prior to be mixed for 5 days in darkness. Dissolved concentration in trace elements were measured over time, along with physical-chemical parameters. The pH in the different conditions decreased all along the experiments while the redox potential decreased during up to 4 days before increasing back to its initial value. Three groups of trace metals were identified: metals whose dissolved concentrations (1) increased (Al, Ba, Co, Cs, Cu, Mn, Mo, Ni, Pb, Sb, Tl, U and Zn) as a consequence of the transfer from sediment, (2) decreased (Cr, Fe and Ti) as a consequence of transfer onto sediment, and (3) remained unchanged over time (As, Li, Rb, Sr and V). The sterilization of either sediment and/or seawater did not have a statistically significant impact onto the dynamics of the physical-chemical parameters, nor onto the metals' behavior (except Mn). Our results demonstrate (i) that marine sediment autoclaving prior to mixing with seawater did not disrupt the behavior of metals in the seawater / sediment mixing over the 5 days of experiments and (ii) that the microbial activity had a negligible influence on the variation of physical-chemical parameters or metals' transfers over the mixing time.