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Influence of plant beneficial Stenotrophomonas rhizophila strain CASB3 on the degradation of diuron-contaminated saline soil and improvement of Lactuca sativa growth
2020
Silambarasan, Sivagnanam | Logeswari, Peter | Ruiz, Antonieta | Cornejo, Pablo | Rajesh Kannan, Velu
Diuron is one of the major hazardous pollutants which posses severe risk to the environment and human healthiness. On the other hand, salinity is the most severe environmental stressor that limits crop productivity. Therefore, it is required to address this co-existing abiotic stresses in agricultural soil. Plant growth–promoting rhizobacteria have gained an engaging role in the degradation of pesticides in agricultural soil. However, their role against the restoration of diuron-contaminated saline soil is still not known. Thus, in this study, diuron-degrading, salinity-tolerant Stenotrophomonas rhizophila strain CASB3 was isolated and characterized. Strain CASB3 showed important PGP traits under normal and diuron or salt stresses. Complete degradation of 10–50 mg L⁻¹ diuron in the aqueous medium under normal and salinity stress conditions was achieved within 48–120 h and 48–192 h, respectively. A unique pathway for diuron biodegradation was proposed based on GC-MS analysis. In a greenhouse study, CASB3 inoculated into diuron-contaminated saline soil efficiently degraded diuron (50 mg kg⁻¹) by 94% in 42 days and simultaneously resulted in an enhancement of root-shoot length (47.22–63.41%), fresh-dry biomass (136.36–156.66%), and photosynthetic pigments (36.93–92.28%) in Lactuca sativa plants. These results suggest the strain CASB3 could be used as a bioresource for the reclamation of diuron-contaminated saline soils.
Afficher plus [+] Moins [-]Sulfur dioxide removal: An overview of regenerative flue gas desulfurization and factors affecting desulfurization capacity and sorbent regeneration
2020
Hanif, Muhammad Adli | Ibrahim, Naimah | Abdul Jalil, Aishah
Numerous mitigation techniques have been incorporated to capture or remove SO₂ with flue gas desulfurization (FGD) being the most common method. Regenerative FGD method is advantageous over other methods due to high desulfurization efficiency, sorbent regenerability, and reduction in waste handling. The capital costs of regenerative methods are higher than those of commonly used once-through methods simply due to the inclusion of sorbent regeneration while operational and management costs depend on the operating hours and fuel composition. Regenerable sorbents like ionic liquids, deep eutectic solvents, ammonium halide solutions, alkyl-aniline solutions, amino acid solutions, activated carbons, mesoporous silica, zeolite, and metal-organic frameworks have been reported to successfully achieve high SO₂ removal. The presence of other gases in flue gas, e.g., O₂, CO₂, NOx, and water vapor, and the reaction temperature critically affect the sorption capacity and sorbent regenerability. To obtain optimal SO₂ removal performance, other parameters such as pH, inlet SO₂ concentration, and additives need to be adequately governed. Due to its high removal capacity, easy preparation, non-toxicity, and low regeneration temperature, the use of deep eutectic solvents is highly feasible for upscale utilization. Metal-organic frameworks demonstrated highest reported SO₂ removal capacity; however, it is not yet applicable at industrial level due to its high price, weak stability, and robust formulation.
Afficher plus [+] Moins [-]Physical Foam Stability of Loose Sandy-Clay: a Porosity Role in the Conditioned Soil
2020
Selmi, Moez | Kacem, Mariem | Jamei, Mehrez | Dubujet, Philippe
To prevent the collapse and settlement of fine granular soil during earth pressure balance (EPB) tunneling or tunneling balance machine (TBM) operations, foaming agent mixing is one of the most efficient techniques. This work focuses on the stability of loose sandy-clay soil conditioned with the foaming agent. Four reconstituted loose sandy-clay soils were conditioned with the foaming agent CLB F5/AC. Using optical observation, Turbiscan analysis, and foam volume determination, the stability of foam mixed with fine soils was studied based on drainage coalescence and coarsening phenomena that occurred over time. Additionally, foam stability under gravity drainage was analyzed through a (one-dimensional) 1D column experiment. Variation in the FIR (foam injection ratio) shows that there is a limit FIR value from which the foam begins to be observed in the soil sample, involving a discontinuous porosity increase to the detriment of the continuous porosity decrease. An approach that considered this discontinuous porosity generated by the inclusion of gas bubbles was used to describe foam bubble degradation. Tests carried out on foam alone showed its rapid degradation compared with that of the foam added and mixed in the soil. Fine particles of clay allow foam stability even in the soil mixture. The foam volume in the soil decreases according to constant volume stages separated by a fast volume decrease. Both drainage and coalescence phenomena have occurred significantly for high values of FIRs. From the 1D column experience, foam bubbles modify the drainage kinetics by accelerating the drainage velocity compared with that of unconditioned soil. The foam behavior evolution over time when mixed with the soil can be analyzed using the same theory of the behavior of the foam alone.
Afficher plus [+] Moins [-]How Effective Are Nanomaterials for the Removal of Heavy Metals from Water and Wastewater?
2020
Borji, Hadil | Ayoub, George M. | Bilbeisi, Rana | Nassar, Nashaat | Malaeb, Lilian
Efficient removal of heavy metals from water and wastewater is a necessity for human and environmental well-being. Agricultural, domestic, and industrial waste discharges increase with the increase in the global population. Discharges are loaded with toxic metallic substances that inevitably reach water sources. Conventional treatment methods are in many cases inadequate in their removal efficiencies. Alternatively, recently developed advanced treatment approaches, such as nanotechnologies, offer advantages in water treatment. Nanotechnology brought about materials with high specific surface areas and adsorption capacities for the removal of undesirable heavy metals present in water. A detailed review of the use of nanotechnologies and nanomaterials for the removal of heavy metals from aqueous solutions is presented in this study. Limitations, research gaps, and suitability of nanotechnology in water treatment for the removal of heavy metals at a large scale are discussed, and relevant conclusions are accordingly deduced.
Afficher plus [+] Moins [-]Modelling of multi-minerals kinetic evolution in hyper-alkaline leachate for a 15-year experiment
2020
Baqer, Yousef | Chen, Xiaohui | Rochelle, Christopher | Thornton, Steven
Cement has been widely used for low- to intermediate-level radioactive waste management; however, the long-term modelling of multiple mineral transfer between the cement leachate and the host rock of a geological disposal facility remains a challenge due to the strong physical-chemical interactions within the chemically disturbed zone. This paper presents a modelling study for a 15-year experiment simulating the reaction of crystalline basement rock with evolved near-field groundwater (pH = 10.8). A mixed kinetic equilibrium (MKE) modelling approach was employed to study the dolomite-rich fracture-filling assemblage reacting with intermediate cement leachate. The study found that the mineralogical and geochemical transformation of the system was driven by the kinetically controlled dissolution of the primary minerals (dolomite, calcite, quartz, k-feldspar and muscovite). The initial high concentration of calcium ions appeared to be the main driving force initiating the dedolomitization process, which played a significant role in the precipitation of secondary talc, brucite and Mg-aluminosilicate minerals. The modelling study also showed that most of the initially precipitated calcium silicon hydrate phases redissolved and formed more stable calcium silicon aluminium hydrate phases. The findings highlight the importance of a deep and insightful understanding of the geochemical transformations based on the type and characteristics of the host rock, where the system is under out of equilibrium conditions, and the rates of mineral reactions.
Afficher plus [+] Moins [-]Radiation-related health hazards to uranium miners
2020
Semenova, Yuliya | Pivina, Lyudmila | Zhunussov, Yersin | Zhanaspayev, Marat | Chirumbolo, Salvatore | Muzdubayeva, Zhanna | Bjørklund, Geir
Concerns on health effects from uranium (U) mining still represent a major issue of debate. Any typology of active job in U mines is associated with exposure to U and its decay products, such as radon (Rn), thorium (Th), and radium (Ra) and its decay products with alpha-emission and gamma radiation. Health effects in U miners have been investigated in several cohort studies in the USA, Canada, Germany, the Czech Republic, and France. While public opinion is particularly addressed to pay attention to the safety of nuclear facilities, health hazard associated with mining is poorly debated. According to the many findings from cohort studies, the most significant positive dose-response relationship was found between occupational U exposure and lung cancer. Other types of tumors associated with occupational U exposure are leukemia and lymphoid cancers. Furthermore, it was found increased but not statistically significant death risk in U miners due to cancers in the liver, stomach, and kidneys. So far, there has not been found a significant association between U exposure and increased cardiovascular mortality in U miners. This review tries to address the current state of the art of these studies.
Afficher plus [+] Moins [-]Identifying environmental pollution recorded in street dust using the magnetic method: a case study from central eastern China
2020
Zhao, Guoyong | Zhang, Ronglei | Han, Yan | Lü, Bin | Meng, Yuanhang | Wang, Shijie | Wang, Ningning
Urban street dust constitutes important intermediate products for the transmission of solid organic and inorganic pollutants in the urban environment. In this study, 133 street dust samples were collected from Xinyang to explore their magnetic characteristics, spatial distribution, and environmental implications using magnetic measurements. The results are as follows. (1) There were ferrimagnetic, antiferrimagnetic, and paramagnetic (e.g., lepidocrocite) minerals in the dust. Among these, the dominant magnetic carriers were ferrimagnetic minerals. Furthermore, magnetite was a first-order ferrimagnetic carrier. (2) The magnetic domains of the dust were pseudo single-domain to multi-domain. (3) The magnetic concentration (χ and SIRM) of dust were 2.6 and 4.1 times higher than those of background samples that were not polluted by urban and anthropogenic activities, respectively. Therefore, we conclude that the dust consisted of high concentration of ferrimagnetic minerals and coarse magnetic particles. (4) The magnetic distribution was spatially different. The industrial area, which was the most polluted sampling area, had the highest magnetic concentration and the coarsest magnetic particles. This was attributable to industrial emissions, fossil fuel combustion, and exhaust emissions from heavy-laden trucks. Residential and commercial areas, which were the second most polluted areas, had higher concentration and coarser particles. This was primarily due to the high population density and traffic activities of mini-cars (i.e., high flux and exhaust emissions). Hence, the conclusion is that the magnetic characteristics, spatial distribution, and the sources of dust are dictated by anthropogenic activities. Our results indicate that the magnetic method is a highly effective tool to monitor urban environmental pollution.
Afficher plus [+] Moins [-]Acute toxicity of fluazinam to aquatic organisms and its bioaccumulation in Brachydanio rerio
2020
Wu, Wenzhu | Kong, Deyang | Zhang, Weidong | Bu, Yuanqing | Li, Juying | Shan, Zhengjun
Fluazinam (FZN) is a dinitroaniline fungicide. To evaluate the environmental risk of FZN in aquatic environments and ascertain the potential danger to typical aquatic organisms in China, the acute toxicity of FZN to representative aquatic organisms, including Brachydanio rerio, Chlorella vulgaris Beij., Daphnia magna Straus, and Xenopus laevis, was measured, and its bioaccumulation properties in Brachydanio rerio were further investigated. The results showed that the acute toxicity of FZN to Brachydanio rerio and Xenopus laevis is extremely high, and the bioaccumulation factor BCF₈d of FZN in Brachydanio rerio ranges between 2287 and 3570, implying that it has high bioaccumulation properties. FZN poses a strong environmental risk for aquatic organisms and possesses great bioaccumulation properties, which may cause pollution to aquatic environments.
Afficher plus [+] Moins [-]Remote sensing-based water quality assessment for urban rivers: a study in linyi development area
2020
Miao, Sheng | Liu, Chao | Qian, Binjie | Miao, Qun
Nowadays, urban rivers play an important role in city development and make great contributions to urban ecology. Most urban rivers are the drinking water sources and water quality is extremely critical. The current assessment method in national standard of China has multiple limitations; therefore, this paper introduces an advanced assessment, that is, Canadian Water Quality Index (CWQI). This method can help to provide comprehensive and objective water quality assessment for the urban rivers. Moreover, CWQI can prevent waste of the water resource, since current assessment is pessimistic and tent to underestimate water samples to a lower grade. Linyi development area is selected as study region and CWQI method is applied to assess two major urban rivers within the area. The water monitoring data from 2014 to 2017 is acquired in 24 parameters. Since the CWQI calculation is still based on traditional water quality measurement in parameters, there will be a huge cost when increasing research scale and accuracy. In this paper, remote sensing technique is employed to develop models of CWQI scores from satellite data. By utilizing 23 selected monitoring instances and matching satellite data, linear regression analysis shows that red band data has highest correlation with CWQI in both two urban rivers in the study region. In addition, two testing datasets with five instances for each river are used to validate the RS-based CWQI models and the results show that testing datasets can be fitted well. With the models, CWQI distribution diagrams are generated and assist both spatial and temporal analysis. Experimental results show that the proposed approach can indicate actual water quality pattern which is validated by field visit. The proposed approach in this paper has satisfying effectiveness and robustness.
Afficher plus [+] Moins [-]Diesel Impacts on Functional Bacterial Groups and Collembolans During Phytoremediation in a Mesocosm System
2020
Guerrero-Chávez, Ana Carolina | Alarcón, Alejandro | Ferrera-Cerrato, Ronald | Díaz-Aguilar, Irma | Mendoza-López, Ma Remedios | Rios-Galicia, Bibiana | Arteaga-Garibay, Ramón Ignacio | Larsen, John
Phytoremediation of contaminated soils relies on the ability of plants to stimulate microbial rhizosphere diversity, by releasing root exudates. This work assessed the impact of diesel contamination on soil populations of culturable bacterial groups (fast growing, N₂-fixing, phosphate (P) solubilizing, and lipolytic bacteria), and collembolans under mesocosm conditions with and without the influence Medicago sativa. We set up six treatments sampled initially within 24 h and examined at 4, 8, and 12 months. Bacterial groups were isolated and identified with 16S rRNA sequencing, while collembolans were classified using taxonomic keys. The populations of P-solubilizing and fast-growing bacteria were stimulated after 4 months in the polluted treatments in absence of M. sativa. On the M. sativa treatments, P-solubilizing and lipolytic bacteria increased after 8 months. Stenotrophomonas and Achromobacter were the most predominant bacterial genera. Collembolans mainly belonging to Poduromorpha and Entomobryomorpha orders, were observed in contaminated treatments on the 12th month, while in the uncontaminated control were found at the 4th month. Hydrocarbon degradation was higher than 80% in all treatments after 12 months. Diesel contamination and soil management reduced significantly the collembolan abundance; these organisms may be considered as biological indicators of soil quality and recovery after an event of diesel contamination.
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