خيارات البحث
النتائج 2211 - 2220 من 4,929
Application of the Langmuir Technique to Study the Response of C-dec-9-en-1-ylcalix[4]resorcinarene and C-undecylcalix[4]resorcinarene Ultra-thin Films' Interactions with Cd2+, Hg2+, Pb2+, and Cu2+ Cations Present in the Subphase
2019
Eddaif, Larbi | Shaban, Abdul | Telegdi, Judit
The calix[4]resorcinarene macrocycles are excellent oligomers for the design of amphiphilic derivatives; they can form self-assemblies and stable sensing networks. Owing to their favorable properties, they are the focus of many exploitations and studies ranging from biological controls to heavy metal ion sensing. In this perspective, two calix[4]resorcinarene derivatives, namely: C-dec-9-en-1-ylcalix[4]resorcinarene (ionophore I) and C-undecylcalix[4]resorcinarene (ionophore II) were used to form stable ultra-thin Langmuir monolayer films at the air/water interface; their interactions with different harmful metal cations (Cd²⁺, Pb²⁺, Hg²⁺, and Cu²⁺) were studied and highlighted via the pressure-area (Π-A) isotherms. The obtained results in the current investigation showed a dependence of both macrocycle interactions on the metal cation concentration in the subphase, confirming their complexation. In addition, the ionophore (I) exhibited high selectivity towards Pb²⁺ and Cu²⁺ cations, whereas the ionophore (II) showed tendency to bind with Cu²⁺ cations over others, approving the potential applicability of these macrocycles as ion selective chemical sensors.
اظهر المزيد [+] اقل [-]Analyses of Influencing Factors for Radon Emanation and Exhalation in Soil
2019
Zhang, Wei Qiang | Zhang, Yuliang | Sun, Qiang
The study on radon emanation and exhalation in soil is more and more important for environmental protection, and many influencing factors on radon emanation coefficient and exhalation in soil have been well documented. In order to evaluate the radon change and key influencing factors, this paper made an overall summary based on these studies. The main results show that the change laws of emanation coefficient with elevated temperature of radon can be divided into three types and they relate to the moisture state and content of soil. The normalized radon exhalation has a negative linear correlation with temperature, and the maximum emanation coefficient has a positive linear correlation with heating rate and specific surface. The pores with different size have different effects on the emanation coefficient of radon in the soil, e.g., the micro-pores increase emanation coefficient, and the mezzo-pores decrease emanation coefficient. Taken together, our results offered guiding significance for the evaluation of radon in soil and in air when soil state changes. Lastly, the existing problems and research directions were also given.
اظهر المزيد [+] اقل [-]Effects of Calcium Phosphates on the (Im)Mobilization of Metals and Nutrients, on the Biological Activity and on the Plant Health from Multi-contaminated Urban Soils
2019
Hechelski, Marie | Louvel, Brice | Dufrénoy, Pierrick | Ghinet, Alina | Waterlot, Christophe
Two smelters in the North of France emitted potentially toxic metals for more than a century and today, the resulting contamination represents a risk to human health and affects also the biodiversity. To limit health risks and to improve the soil quality, a study using calcium phosphates (monocalcium phosphate, dicalcium phosphate and a mixture of both salts) and Lolium perenne L was conducted. Through this preliminary investigation, we will try to shed some light about (i) the effects of a sustainable amount of calcium phosphates on the agronomic, biological (microbial and fungi communities) and physiological parameters (chlorophyll a and b, antocyanins, carotenoids) as well as the phytoavailability of potentially toxic metals and nutrients in time, and (ii) the potential use of contaminated biomass from ryegrass as a source of new valorisation ways instead of using it as contaminated compost by gardeners. Although slight variations in pH and significant increases of assimilable phosphorus after adding calcium phosphates were registered, the physiology of plants and the biological parameters were statistically unchanged. The germination of the ryegrass seeds was favoured with calcium phosphates regardless the contamination level of the studied soils. No clear effects of calcium phosphates on the microbial and fungi communities were detected. In contrast, results indicated relationships between the physicochemical parameters of soils, their contamination level and the composition of fungal communities. Indeed, for one of the soils studied, calcium could limit the transport of nutrients, causing an increase in fungi to promote again the transfer of nutrients. Surprisingly, the phytoavailability of Pb increased in the most contaminated soil after adding dicalcium phosphate and the mixture of phosphates whereas a slight decrease was highlighted for Cd and Mn. Although minor changes in the phytoavailability of potentially toxic metals were obtained using calcium phosphates, the ability of ryegrass to accumulate Zn and Ca (up to 600 and 20,000 mg kg⁻¹, respectively) make possible to qualify this plant as a bio ‘ore’ resource.
اظهر المزيد [+] اقل [-]Pentachlorophenol Removal from Water by Soybean Peroxidase and Iron(II) Salts Concerted Action
2019
Tolardo, Valentina | García-Ballesteros, Sara | Santos-Juanes, Lucas | Vercher, Rosa | Amat, Ana M. | Arques, Antonio | Laurenti, Enzo
Soybean peroxidase (SBP) has been employed for the treatment of aqueous solutions containing pentachlorophenol (PCP) in the presence of hydrogen peroxide at pH range 5–7. Reaction carried out with 1 mg/L of PCP, 4 mg/L of H₂O₂, and 1.3 × 10⁻⁹ M of SBP showed a fast initial elimination of PCP (ca. 30% in 20 min), but the reaction does not go beyond the removal of 50% of the initial concentration of PCP. Modification in SBP and PCP amounts did not change the reaction profile and higher amounts of H₂O₂ were detrimental for the reaction. Addition of Fe(II) to the system resulted in an acceleration of the process to reach nearly complete PCP removal at pH 5 or 6; this is more probably due to a synergetic effect of the enzymatic process and Fenton reaction. However, experiments developed in tap water resulted in a lower PCP elimination, but this inconvenience can be partly overcome by leaving the tap water overnight in an open vessel before reaction.
اظهر المزيد [+] اقل [-]Dietary exposure and risk assessment of organochlorine pesticide residues in rural communities living within catchment areas of iSimangaliso World Heritage Site, South Africa
2019
Buah-Kwofie, Archibold | Humphries, Marc S. | Pillay, Letitia
Dietary intake of contaminated food is a major route of human exposure to organochlorine pesticides (OCPs). Despite the prevalence of OCP usage in southern Africa for several decades, their impact on socioeconomically vulnerable communities remains largely overlooked. We investigated the accumulation of OCPs in crops commonly cultivated by rural communities surrounding iSimangaliso Wetland Park, South Africa. All samples analysed were found to be contaminated, with total OCP concentrations ranging between 190 and 240 ng g⁻¹ ww. Elevated levels of OCP residues were detected in all products, with the majority of samples exceeding European Commission’s maximum residue limits (MRLs). We combine these results with local OCP fish tissue estimates to assess potential dietary risks. Cumulative risk assessment indicated potential non-cancer risks associated with heptachlor epoxide, while a cancer risk as high as 1 in 10 was found to be associated with aldrin and dieldrin. This far exceeds USEPA guidelines and indicates that OCP residues in crops and fish from the study area pose a high risk to human health. The results of this study call for further attention to be given to the health implications of continued OCP use not only within the study area but also in Southern Africa in general.
اظهر المزيد [+] اقل [-]Enhanced Bioremediation of Heavy Metal Contaminated Landfill Soil Using Filamentous Fungi Consortia: a Demonstration of Bioaugmentation Potential
2019
Hassan, Auwalu | Pariatamby, Agamuthu | Ahmed, Aziz | Auta, Helen Shnada | Hamid, Fauziah Shahul
This study aimed to determine the mycoremediative capacity of filamentous fungi consortia in landfill heavy metal contaminated soil. Streak plate method was utilized for the isolation of fungi from the landfill soil. Isolates were identified using morphological and molecular techniques. Heavy metal tolerance of the fungi was determined using radial growth diameter technique. Twelve species of landfill indigenous fungi were used for the bioremediation process. Two categories of fungi consortia namely highly tolerant fungi (Perenniporia subtephropora, Daldinia starbaeckii, Phanerochaete concrescens, Cerrena aurantiopora, Fusarium equiseti, Polyporales sp., Aspergillus niger, Aspergillus fumigatus, and Trametes versicolor) and moderately tolerant fungi (Paecilomyces lilacinus, Antrodia serialis, and Penicillium cataractum) were used to amend the contaminated soil; meanwhile, the unamended soil served as control. Maximum tolerance index of 1.0 was reported in Cr-, Cu-, and Fe-amended PDA medium. Meanwhile, the maximum heavy metal bioremoval efficiencies were for highly tolerant fungal consortium treated soil and were recorded as As (62%) > Mn (59%) > Cu (49%) > Cr (42%) > Fe (38%). Likewise, the maximum metal removal rate constant (K) and the half-lives (t₁/₂) were 0.0097/day 71 days, 0.0088/day 79 days, 0.0067/day 103 days, 0.0054/day 128 days, and 0.0048/day 144 days for As, Mn, Cu, Cr, and Fe, respectively, which were all for soil treated with consortium of highly tolerant fungi (P. subtephropora, D. starbaeckii, P. concrescens, C. aurantiopora, F. equiseti, Polyporales sp., A. niger, A. fumigatus, and T. versicolor). Spectra analysis revealed a clear distinction in the functional groups between the fungal treated and the untreated soils. Peaks at 874 ± 2 cm⁻¹ and 1425 ± 2 cm⁻¹ were only found in fungi amended soil. Physicochemical parameters mainly pH and redox potential played a key role in the bioremediation process, and bioaccumulation was believed to be the favored mechanism for the metal bioremoval. The data are suitable for assessing the contribution of bioaugmentation with consortia of fungi. It is equally important for assessing the synergistic effect of fungi on the reduction of extractable heavy metals in contaminated soil.
اظهر المزيد [+] اقل [-]Vulnerability, well-being, and livelihood adaptation under changing environmental conditions: a case from mountainous region of Pakistan
2019
Shahzad, Laila | Tahir, Arifa | Sharif, Faiza | Khan, Waqas Ud Din | Farooq, Muhammad Ansar | Abbas, Azhar | Saqib, Zulfiqar Ahmad
Climatic changes pose serious risks to the rural community’s livelihoods of many developing countries whereas people in mountainous regions are exposed to multiple hazards with limited livelihood resources and heavy dependence on natural resources. The objective of the current study is to assess the livelihood practices and adaptive capacity of a mountainous region of Pakistan, the Balakot, where people are highly vulnerable to climatic changes. The study uses a triangulation method to explore various issues and options of climate change risks sand adaptation and impact of well-being on resilience capacity and livelihood strategies. For this purpose, ten focus group discussions (FGDs) with carefully selected key informants and structured interviews with randomly selected 200 local households are conducted to evaluate different hazards and their associated livelihood effects. It is observed that the changing climate has significantly influenced livelihoods of the local community in the recent past through resource degradation, gradual unavailability of sufficient basic services (quantity and quality of drinking water, crop food diversity, fuel wood, and non-timber forest products), low agricultural productivity, and social inequity viz. income distribution, health, education, and food storage. Such a brunt is felt disproportionately more by poor households due to their low adaptive capacity to climate change with constrained livelihood resources. The study emphasizes the need for targeted efforts to move from coping strategies to adaptations among people considering their social inequalities. Timely information sharing, livelihood diversification and preservation of livelihood resources such as crop and forest production, livestock grazing, creating awareness on the pace, and pattern of climate change in the region and subsequent role of adaptation options are major interventions that should be emphasized by the public bodies.
اظهر المزيد [+] اقل [-]Effects of different scrap iron as anode in Fe-C micro-electrolysis system for textile wastewater degradation
2019
Sun, Zhenhua | Xu, Zhihua | Zhou, Yuwei | Zhang, Daofang | Chen, Weifang
The degradation of organic contaminants in actual textile wastewater was carried out by iron carbon (Fe-C) micro-electrolysis. Different Fe-C micro-electrolysis systems (SIPA and SISA) were established by using scrap iron particle (SIP) and scrap iron shaving (SIS) as anode materials. The optimal condition of both systems was obtained at the initial pH of 3.0, dosage of 30 g/L and Fe/C mass ratio of 1:1. Commercial spherical Fe-C micro-electrolysis material (SFC) was used for comparison under the same condition. The results indicated that total organic carbon (TOC) and chroma removal efficiencies of SIPA and SISA were superior to that of SFC. Total iron concentration in solution and XRD analysis of electrode materials revealed that the former showed relatively high iron corrosion intensity and the physicochemical properties of scrap iron indeed affected the treatment capability. The UV-vis and 3DEEM analysis suggested that the pollutants degradation was mainly attributed to the combination of reduction and oxidation. Furthermore, the potential degradation pathways of actual textile wastewater were illustrated through the GC-MS analysis. Massive dyes, aliphatic acids, and textile auxiliaries were effectively degraded, and the SIPA and SISA exhibited higher performance on the degradation of benzene ring and dechlorination than that by SFC. In addition, SIPA and SISA exhibited high stability and excellent reusability at low cost. Graphical abstract
اظهر المزيد [+] اقل [-]Economic value of traffic noise reduction depending on residents’ annoyance level
2019
Kim, Kyungah | Shin, Jungwoo | Oh, Myoungjin | Jung, Jung-Kyu
Noise is the most frequently encountered type of environmental pollution in everyday life and has a direct negative effect on humans. Individuals who are constantly exposed to noise tend to have a high incidence of cardiovascular disease and hypertension. Noise sources range from construction sites to political rallies and assemblies, but traffic is one of the most long-lasting and chronic sources of noise. Previously, researchers have conducted valuations of road traffic noise reduction, but they did not consider residents’ annoyance levels in response to traffic noise. However, individuals’ annoyance levels affect the economic value of noise reduction policies and thus must be considered to obtain an accurate estimate. Therefore, this study investigated residents’ willingness to pay for traffic noise reduction depending on their annoyance level. We used the contingent valuation method and a survey to analyze how much 1022 respondents in Korea were willing to pay for noise reduction. We found that people who were annoyed and extremely annoyed by noise had a willingness to pay KRW 8422 (US $7.55) and KRW 9848 (US $8.83) annually per household, respectively, to reduce their annoyance level to zero. In addition, we determined the economic benefits of noise reduction policies using the respondents’ willingness to pay to reduce noise by 1 dB(A), which totaled KRW 3.28 billion (US $2.91 million) per year. The results of this study provide estimates of the annual benefits of traffic noise reduction considering residents’ annoyance level.
اظهر المزيد [+] اقل [-]Citric Acid Functionalized Bougainvillea spectabilis: a Novel, Sustainable, and Cost-effective Biosorbent for Removal of Heavy Metal (Pb2+) from Waste Water
2019
Nazir, Huma | Salmān, Muḥammad | Athar, Makshoof | Farooq, Umar | Wahab, Abdul | Akram, Momal
With increasing concern related to sustainable chemistry, we investigated the biosorption of Pb²⁺ ions from aqueous medium using an environmental friendly and economic biosorbent Bougainvillea spectabilis (BS). The BS was modified effectively using citric acid by hydrothermal method. The biosorbent(s) was characterized by scanning electron microscope (SEM), energy dispersion X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and point of zero charge (pHₚzc). Various process parameters including biosorbent dosage, time of contact, temperature, solution pH, and initial Pb²⁺ ions concentration were studied in batch mode. Kinetic modeling was performed to evaluate the kinetic data and results showed that the studied process followed the pseudo second order (PSO) kinetics. Equilibrium modeling was done using famous equilibrium models, i.e., Langmuir, Freundlich, Dubinin-Kaganer-Radushkevish, and Temkin in non-linear fashion to evaluate equilibrium data by varying initial Pb²⁺ ions concentration from 20 to 180 mg/L. Based on RMSE values, Langmuir model fits best. This paper also discusses thermodynamic parameters (i.e., enthalpy, entropy, and free energy) showing that the process was spontaneous and endothermic in nature. In comparison with BS (B. spectabilis), an appreciable increase in uptake capacity of CABS (citric acid modified B. spectabilis) was observed in sequestration of Pb²⁺ ions from aqueous medium showing advantage of citric acid modification making it industrially favorable and socially acceptable biosorbent for efficient removal of lead from water.
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