خيارات البحث
النتائج 4171 - 4180 من 4,924
Perceived outcomes of Good Agricultural Practices (GAPs) technologies adoption in citrus farms of Iran (reflection of environment-friendly technologies)
2019
Razzaghi Borkhani, Fatemeh | Mohammadi, Yaser
The main purpose of this study was to analyze the perceived outcomes of Good Agricultural Practices (GAPs) technologies adoption in order to sustain citrus farms in Mazandaran province, Iran. Study population consisted of all citrus growers in the villages of 12 counties of Mazandaran province, which a sample of 290 orchardmen were selected through a proportional random sampling technique. A questionnaire was designed to collect data which was both valid and reliable according to expert opinion and Cronbach’s alpha coefficient respectively. The results of the factor analysis showed that “market access and safe product exports,” “consumer’ health and environment-friendly behavior,” “safe production and public demand,” and “information sharing and strengthening local associations” were the four perceived outcomes of GAPs technologies adoption in citrus farms of Iran. These factors explained 65.02% of the total variance. These four perceived outputs of GAPs support economic, environmental, and social sustainability dimensions respectively.
اظهر المزيد [+] اقل [-]Effect of electrolytes on the simultaneous electrochemical oxidation of sulfamethoxazole, propranolol and carbamazepine: behaviors, by-products and acute toxicity
2019
García-Espinoza, Josué Daniel | Mijaylova Nacheva, Petia
In this work, the effect of supporting electrolytes on the simultaneous electrochemical oxidation of the pharmaceuticals sulfamethoxazole (SMX), propranolol (PRO), and carbamazepine (CBZ) in aqueous solutions has been studied. Based on the identified by-products, the degradation mechanisms were proposed and the acute toxicity was evaluated for each electrolyte. Assays were carried out in batch mode in a 2 L undivided reactor using a niobium coated with boron-doped diamond (Nb/BDD) mesh anode and Ti cathode at 2.5 A in presence of different supporting electrolytes (Na₂SO₄, NaCl, or NaBr) at the same concentration of 7 mM. The degradation rates were higher in the assays with NaCl and NaBr. Reaction by-products were identified by gas chromatography–mass spectrometry. Indirect oxidation by electrogenerated reactive halogen species (RHS) was the main mechanism when halide ions were used as electrolytes. Ten by-products were detected using Na₂SO₄ as electrolyte, while 19 (12 non-halogenated and 7 halogenated) and 20 (10 non-halogenated and 10 halogenated) using NaCl and NaBr respectively. The proposed degradation pathways involve transformation (hydroxylation, deamination, desulfonation, and halogenation) and bond rupture to produce less molecular weight compounds and their further transformation until total degradation. Chlorinated and brominated by-products confirm halogenation reactions. The electrogenerated RHS presented a significant inhibition effect on Vibrio fischeri; nevertheless, acute toxicity was not presented using Na₂SO₄ as electrolyte and a pharmaceutical concentration of 5 μg/L. In this view, the role of the supporting electrolyte in electrochemical oxidation process is crucial since it strongly influence degradation rate, by-products, and acute toxicity.
اظهر المزيد [+] اقل [-]Gallic acid degradation by electron beam irradiation under various conditions
2019
Alkhuraiji, Turki S. | Boukari, Sahidou O. B. | Leitner, Nathalie Karpel Vel
In this study, aqueous solutions of gallic acid (GA) were irradiated in an electron beam (EB) accelerator under different experimental conditions (various initial GA concentrations, presence or absence of oxidant and oxygen). For an initial GA concentration of 50 μM, complete GA degradation was achieved with an absorbed dose of 850 Gy in the presence of dissolved oxygen. Both GA removal and mineralization are favored when oxygen is present. The addition of persulfate anions (S₂O₈²⁻) or hydrogen peroxide (H₂O₂) also increased the efficiency of GA degradation and mineralization. For an absorbed dose of 14 kGy, GA mineralization reached approximately 45%, 55%, and 72% for the EB, EB/H₂O₂, and EB/S₂O₈²⁻systems, respectively. Three transformation products were tentatively identified in the presence of oxygen, these are the result of hydroxylation and ring opening reactions. No specific transformation product was found for the sulfate radical anion (SO₄–●) reaction. Four additional compounds, including a dimer, were identified in oxygen-free solutions. These findings demonstrate that water radiolysis based on EB irradiation is an efficient process to activate H₂O₂ and S₂O₈²⁻ anions and is an advanced oxidation process (AOP).
اظهر المزيد [+] اقل [-]Insecticidal efficacy of six new pyrrole derivatives against four stored-product pests
2019
Boukouvala, Maria C. | Kavallieratos, Nickolas G. | Athanassiou, Christos G. | Benelli, Giovanni | Hadjiarapoglou, Lazaros P.
Several pyrrole derivatives exhibit insecticidal activity and can be effective as grain protectants. In the present study, we evaluate the insecticidal efficacy of six novel pyrrole derivatives, namely methyl 3-(methylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1 carboxylate (compound syn) (2a-syn), methyl 3-(methylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1-carboxylate (compound anti) (2a-anti), methyl 3-(benzylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1-carboxylate (compound syn) (2f-syn), methyl 3-(benzylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1-carboxylate (compound anti) (2f-anti), methyl 3-(butylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1-carboxylate (3e), and methyl 2-benzyl-3-(methylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1-carboxylate (0665), against four important species infesting stored products, the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), the lesser grain borer, Rhyzopertha dominica (Coleoptera: Bostrychidae), the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae), and the Mediterranean flour moth, Ephestia kuehniella (Lepidoptera: Pyralidae). The six pyrrole derivatives were evaluated on wheat at different doses (0.1, 1, and 10 ppm) and exposure intervals (7, 14, and 21 days). For S. oryzae adults, the highest mortality was recorded at 10 ppm of 2a-syn (36.7%) followed by 2f-syn (32.2%) and 2f-anti (27.8%) after 21 days of exposure. Regarding progeny production, the application of the six pyrrole derivatives significantly reduced offspring emergence if compared with the controls. After 21 days, mortality of R. dominica reached 50% testing 10 ppm of 2f-syn, followed by 2a-syn (46.7%), 2f-anti (41.1%), and 2a-anti (33.3%), while for 3e and 0665, mortality remained low, not exceeding 17.8%. Mortality of T. confusum adults was very low, ranging from 0 to 16.7% after 21 days of exposure. Progeny production was low (< 1.7 individuals per vial) for all doses of the tested pyrrole derivatives, including control vials. For 2a-syn, 2a-anti, 2f-anti, and 0665, no progeny production was recorded testing 1 and 10 ppm, while for 2f-syn and 3e, no offspring emergence was noted testing 10 ppm. For T. confusum larvae, after 21 days of exposure, mortality reached 62.2% testing 10 ppm of 3e followed by 0665 (55.6%) and 2a-anti (42.2%). For E. kuehniella larvae, mortality reached 57.8% at 10 ppm of 2a-syn, followed by the pyrrole derivative 2f-anti (43.3%) after 21 days of exposure. Overall, these results show that the efficacy of pyrrole derivatives strongly varied according to the exposure interval, tested dose, treated insect species and developmental instar. The tested pyrrole derivatives, with special reference to 2a-syn, 2a-anti, 2f-syn, 2f-anti and 0665, are slow-acting compounds exerting relevant toxicity on key stored-product pests over time. They can be considered further for assays with selected blends aiming to develop novel control tools against stored-product pests in real-world conditions.
اظهر المزيد [+] اقل [-]Leaching of metals from end-of-life solar cells
2019
Chakankar, Mital | Su, Junhui | Hocheng, Hong
The issue of recycling waste solar cells is critical with regard to the expanded use of these cells, which increases waste production. Technology establishment for this recycling process is essential with respect to the valuable and hazardous metals present therein. In the present study, the leaching potentials of Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans, Penicillium chrysogenum, and Penicillium simplicissimum were assessed for the recovery of metals from spent solar cells, with a focus on retrieval of the valuable metal Te. Batch experiments were performed to explore and compare the metal removal efficiencies of the aforementioned microorganisms using spent media. P. chrysogenum spent medium was found to be most effective, recovering 100% of B, Mg, Si, V, Ni, Zn, and Sr along with 93% of Te at 30 °C, 150 rpm and 1% (w/v) pulp density. Further optimization of the process parameters increased the leaching efficiency, and 100% of Te was recovered at the optimum conditions of 20 °C, 200 rpm shaking speed and 1% (w/v) pulp density. In addition, the recovery of aluminum increased from 31 to 89% upon process optimization. Thus, the process has considerable potential for metal recovery and is environmentally beneficial.
اظهر المزيد [+] اقل [-]Elucidation of contamination sources for poly- and perfluoroalkyl substances (PFASs) on Svalbard (Norwegian Arctic)
2019
Skaar, Jøran Solnes | Ræder, Erik Magnus | Lyche, Jan Ludvig | Ahrens, Lutz | Kallenborn, Roland
A combination of local (i.e. firefighting training facilities) and remote sources (i.e. long-range transport) is assumed to be responsible for the occurrence of per- and polyfluoroalkyl substances (PFASs) in Svalbard (Norwegian Arctic). However, no systematic elucidation of local PFASs sources has been conducted yet. Therefore, a survey was performed aiming at identifying local PFAS pollution sources on the island of Spitsbergen (Svalbard, Norway). Soil, freshwater (lake, draining rivers), seawater, meltwater run-off, surface snow and coastal sediment samples were collected from Longyearbyen (Norwegian mining town), Ny-Ålesund (research facility) and the Lake Linnévatnet area (background site) during several campaigns (2014–2016) and analysed for 14 individual target PFASs. For background site (Linnévatnet area, sampling during April to June 2015), ΣPFAS levels ranged from 0.4 to 4 ng/L in surface lake water (n = 20). PFAS in meltwater from the contributing glaciers showed similar concentrations (~ 4 ng/L, n = 2). The short-chain perfluorobutanoate (PFBA) was predominant in lake water (60–80% of the ΣPFASs), meltwater (20–30%) and run-off water (40%). Long-range transport is assumed to be the major PFAS source. In Longyearbyen, five water samples (i.e. 2 seawater, 3 run-off) were collected near the local firefighting training site (FFTS) in November 2014 and June 2015, respectively. The highest PFAS levels were found in FFTS meltwater run-off (118 ng/L). Perfluorooctane sulfonic acid (PFOS) was the most abundant compound in the FFTS meltwater run-off (53–58% PFASs). At the research station Ny-Ålesund, seawater (n = 6), soil (n = 9) and freshwater (n = 10) were collected in June 2016. Low ΣPFAS concentrations were determined for seawater (5–6 ng/L), whereas high ΣPFAS concentrations were found in run-off water (113–119 ng/L) and soil (211–800 ng/g dry weight (dw)) collected close to the local FFTS. In addition, high ΣPFAS levels (127 ng/L) were also found in freshwater from lake Solvatnet close to former sewage treatment facility. Overall, at both FFTS-affected sites (soil, water), PFOS was the most abundant compound (60–69% of ΣPFASs). FFTS and landfill locations were identified as major PFAS sources for Svalbard settlements.
اظهر المزيد [+] اقل [-]Calcium amendment improved the performance of fragrant rice and reduced metal uptake under cadmium toxicity
2019
Kanu, Adam Sheka | Ashraf, Umair | Mo, Zhaowen | Sabir, Sabeeh-ur-Rasool | Baggie, Idris | Charley, Christen Shaka | Tang, Xiangru
Cadmium (Cd) toxicity has detrimental effects on plant metabolism and yield formation. This study examined the effects of Cd stress in rice and the possible role of calcium (Ca) in mitigating oxidative damage caused by Cd in two fragrant rice cultivars, i.e., Guixiangzhan and Meixiangzhan 2. The experimental treatments were composed of various Ca and Cd levels as individual, i.e., Ca at 2.5 and 5.0 mg/kg soil (Ca1 and Ca2, respectively), Cd at 50 and 100 mg/kg soil (Cd50 and Cd100, respectively), and combined, i.e., Ca1+Cd50, Ca1+Cd100, Ca2+Cd50, and Ca2+Cd100. Plants without Ca and Cd application were taken as control (CK). Results showed that Cd stress led to a substantial decline in the photosynthetic pigments, i.e., Chl a, Chl b, and carotenoids, while enhanced oxidative damage in terms of increased levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) and electrolyte leakage (EL) in both rice cultivars. Moreover, Cd stress hampered the activities of enzymatic antioxidants, i.e., superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), with lowest antioxidant activities were recorded at Cd100. The overall trend (lowest to highest) for antioxidant activities across treatments was recorded as Cd100 < Ca2+Cd100 < Cd50 < Ca1+Cd100 < CK < Ca1 < Ca1+Cd50 < Ca2+Cd50 < Ca2. Similarly, Ca amendment improved the proline, soluble protein, and soluble sugar contents in both rice cultivars under Cd stress condition. Comparing Ca2 with CK, the yield and related components, i.e., number of panicles, spikelets per panicle, seed setting rate, 1000 grain weight, and grain yield, were found to increase by 13.08, 2.39, 4.03, 5.86, and 27.53% for Guixiangzhan and 16.48, 5.19, 6.87, 15.44, and 51.16% for Meixiangzhan, respectively. Furthermore, Cd contents in roots, stems, leaves, and grains increased with increased Cd concentration applied and reduced with Ca amendment. The Cd contents in grains for all Ca+Cd levels are statistically at par with each other and significantly lower (P < 0.05) than those for individual Cd application. Hence, Ca amendment can be an appropriate approach to ameliorate the toxic effects of Cd in crops grown under Cd-contaminated soils.
اظهر المزيد [+] اقل [-]Difference of trace element exposed routes and their health risks between agriculture and pastoral areas in Bay County Xinjiang, China
2019
Tudi, Muyesaier | Phung, Dung Tri | Ruan, Huada Daniel | Yang, Lin-sheng | Guo, Hai-Jun | Connell, Des | Sadler, Ross | Chu, Cordia
The concentration level related to toxicities of trace elements in drinking water, rice, wheat flour, and their associated negative impacts on human health have become an emergent issue in China. Because Xinjiang is the largest province in China with the majority of arable pasture land available for cultivation, it is important to analyze the concentrations of trace elements in relation to their toxicities in water, rice, and wheat flour and to investigate the health risk differences between agricultural and pastoral areas in Bay County, Xinjiang. The study results showed that (1) metal concentrations from drinking water, rice, and wheat flour were within the permissible limits; (2) concentration levels of trace elements and their total risk from drinking water and rice were higher in the agricultural areas than those in the pastoral areas, whereas concentration levels of trace elements and their total risk from wheat flour were higher in the pastoral areas than those in the agricultural areas; (3) the concentration level of the trace elements in rice were higher than in the wheat flour, but the risk from the wheat flour was higher than the risk from rice; (4) total non-cancer risk from the flour (HIf) in both areas exceeded the respective safe reference doses; (5) total cancer risk from the wheat flour, rice, and water exceeded the safety limit (1 × 10⁻⁴); (6) for the exposed population, arsenic was suggested as the most evident pollutant leading to carcinogenic concerns regarding the water, rice, and wheat flour; (7) the risk index from the wheat flour made up the highest percentage both in the total cancer risk and the non-cancer risk, followed by rice and then water; and (8) the human health risk was attributed to influence from the local environment in the agriculture areas, while it was attributed to the external environment in the pastoral areas. Graphical abstract
اظهر المزيد [+] اقل [-]No evidence of the role of early chemical exposure in the development of β-cell autoimmunity
2019
Salo, Harri M. | Koponen, Jani | Kiviranta, Hannu | Rantakokko, Panu | Honkanen, Jarno | Härkönen, Taina | Ilonen, Jorma | Virtanen, Suvi M. | Tillmann, Vallo | Knip, Mikael | Vaarala, Outi
Exposure to environmental chemicals can modulate the developing immune system, but its role in the pathogenesis of type 1 diabetes is largely unexplored. Our objective was to study the levels of circulating concentrations of environmental pollutants during the first years of life and their associations with the later risk of diabetes-predictive autoantibodies. From two birth-cohort studies including newborn infants with HLA-conferred susceptibility to type 1 diabetes (FINDIA and DIABIMMUNE), we identified case children with at least one biochemical diabetes-associated autoantibody (n = 30–40) and from one to four autoantibody-negative controls per each case child matched for age, gender, diabetes-related HLA-risk, delivery hospital, and, in FINDIA, also dietary intervention group. Plasma levels of 13 persistent organic pollutants and 14 per- and polyfluorinated substances were analyzed in cord blood and plasma samples taken at the age of 12 and 48 months. Both breastfeeding and the geographical living environment showed association with circulating concentrations of some of the chemicals. Breastfeeding-adjusted conditional logistic regression model showed association between decreased plasma HBC concentration at 12-month-old children and the appearance of diabetes-associated autoantibodies (HR, 0.989; 95% Cl, 0.978–1.000; P = 0.048). No association was found between the plasma chemical levels and the development of clinical type 1 diabetes. Our results do not support the view that exposure to the studied environmental chemicals during fetal life or early childhood is a significant risk factor for later development of β-cell autoimmunity and type 1 diabetes.
اظهر المزيد [+] اقل [-]Effect of diesel-methanol-nitromethane blends combustion on VCR stationary CI engine performance and exhaust emissions
2019
Kumar, Chandan | Rana, Kunj Bihari | Tripathi, Brajesh
The continuous rise in cost of fossil fuels and environmental pollution has attracted research in the area of clean alternative fuels for improving the performance and emission of internal combustion engines. In the present work, methanol and nitromethane were treated as a biofuel and investigations have been made to evaluate the feasibility of replacing diesel with a suitable diesel-methanol-nitromethane blend. For this, experimental investigations were carried out on a VCR diesel engine using diesel-methanol-nitromethane blends to determine the most favorable blending ratio and engine operating parameters for enhancing performance and reduce emissions. The best results of performance and emissions were observed with D-M5-NM2.5 blend (diesel 92.5%, methanol 5%, nitromethane 2.5%) at standard engine parameters. The improvement in engine performance (13% increment in BTE and 19.5% decrement in BSFC) and reduction in emission (smoke 26.47%, NOx 21.66%, and CO 14.28%) was found using D-M5-NM2.5 blend as compared to pure diesel at full load condition; however, HC emission was slightly increased by 10.71%. To find out the best suitable value of CR for D-M5-NM2.5 blend, experiments were further performed on different compression ratios by which higher compression ratio of 19.5 was found better under similar operating conditions. By increasing CR from 18.5 (standard) to 19.5, improvement in engine performance (BTE increased 3.8% and BSFC decreased 3.4%) and reduction in emission (smoke 10%, CO 16.67%, and HC 61.29%) were observed using D-M5-NM2.5 blend; however, NOx was found to be on slightly higher side with tolerable increment of 6.38%.
اظهر المزيد [+] اقل [-]