خيارات البحث
النتائج 2761 - 2770 من 4,936
Influence of fungi and bag mesh size on litter decomposition and water quality النص الكامل
2019
Zhai, Jiexiu | Cong, Ling | Yan, Guoxin | Wu, Yanan | Liu, Jiakai | Wang, Yu | Zhang, Zhenming | Zhang, Mingxiang
Litter decomposition is a complex process that is influenced by many different physical, chemical, and biological processes. Environmental variables and leaf litter quality (e.g., nutrient content) are important factors that play a significant role in regulating litter decomposition. In this study, the effects of adding fungi and using different mesh size litter bags on litter (Populus tomentosa Carr. and Salix matsudana Koidz.) decomposition rates and water quality were investigated, and investigate the combination of these factors influences leaf litter decomposition. Dissolved oxygen (DO), chemical oxygen demand (COD), total phosphorus (TP), and ammonia-nitrogen (NH₃-N) were measured during the 112-day experiment. The salix leaf litter (k = 0.045) displayed faster decomposition rates than those of populous leaf litter (k = 0.026). Litter decomposition was initially slow and then accelerated; and by the end of the experiment, the decomposition rate was significantly higher (p = 0.012, p < 0.05) when fungi were added to the treatment process compared to the blank, and litter bags with different mesh sizes did not influence the decomposition rate. The variations in the decomposition rates and nutrient content were influenced by litter quality and a number of environmental factors. The decomposition rate was most influenced by internal factors related to litter quality, including the N/P and C/P ratios of the litter. By quantifying the interact effect of environment and litter nutrient dynamic, to figure out the revetment plant litter decomposition process in a wetland system in biological physical and chemical aspects, which can help us in making the variables that determine decomposition rates important for assessing wetland function.
اظهر المزيد [+] اقل [-]Using crop modeling to evaluate the impacts of climate change on wheat in southeastern turkey النص الكامل
2019
Vanli, Ömer | Ustundag, Burak Berk | Ahmad, Ishfaq | Hernandez-Ochoa, Ixchel M. | Hoogenboom, Gerrit
The extreme temperatures and uneven distribution of rainfall associated with climate change are expected to affect agricultural productivity and food security. A study was conducted to evaluate the impact of climate change on wheat in southeastern regions of Turkey. The CERES-wheat crop simulation model was calibrated and evaluated with data from eight surveyed farms. The four farms were used for calibration and four for evaluation. Climate change scenarios were developed for the middle (2036–2065) and late 21st century (2066–2095) under representative concentration pathways (RCPs 4.5 and 8.5) for study sites in Islahiye and Nurdagi. Model calibration results showed a good agreement between observed and simulated yield with only a 1 to 11% range of error. The model evaluation results showed good fit between observed and simulated values of all parameters with % error ranged from 0.51 to 13.3%. Future climate change projections showed that maximum temperature (Tmax) will increase between 1.6 °C (RCP4.5) and 2.3 °C (RCP8.5), while minimum temperature (Tmin) will increase between 1.0 °C (RCP4.5) and 1.5 °C (RCP8.5) for mid-century. At the end of the century, Tmax is projected to increase from 2 °C (RCP4.5) to 4 °C (RCP8.5) and Tmin from 1.3 °C (RCP4.5) to 3.1 °C (RCP8.5). Climate change impacts results showed that future rise in temperature will reduce wheat yield by 16.3% in mid-century and 16.8% at the end of the century at Islahiye and for Nurdagi, while 13.0% in mid and 14.4% end of the century. The use of climate and crop modeling technique provides useful information in evaluating the climate change impacts and may assist stakeholders to make decisions to overcome the negative impacts in the near and long term.
اظهر المزيد [+] اقل [-]A novel superparamagnetic micro-nano-bio-adsorbent PDA/Fe3O4/BC for removal of hexavalent chromium ions from simulated and electroplating wastewater النص الكامل
2019
In order to improve the adsorption efficiency of the adsorbent and solve the problem of separation difficulty, a novel superparamagnetic micro-nano-bio-adsorbent (PDA/Fe₃O₄/BC) was prepared by in situ self-assembly of polydopamine (PDA). The results of scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and vibrating sample magnetometer (VSM) characterization showed that the size of bio-adsorbent was about 200 nm. PDA and Fe₃O₄ modifications increased the specific surface area of adsorbent, changed the surface functional group of biochar (BC), and made the adsorbent have super-high magnetization (294.76 emu g⁻¹). PDA/Fe₃O₄/BC was applied to treat Cr wastewater. The results show that the adsorption of Cr by PDA/Fe₃O₄/BC includes single-layer and multilayer adsorption. The adsorption follows the pseudo-second-order kinetic model. The adsorption is spontaneous and endothermic, and its maximum adsorption capacity and activation energy are 25.25 mg g⁻¹ at 318 K and 23.108 kJ mol⁻¹, respectively. After adsorption treatment, PDA/Fe₃O₄/BC still possesses high magnetization (233.04 emu g⁻¹). PDA/Fe₃O₄/BC can treat actual electroplating wastewater with Cr(VI) concentration from 20 mg L⁻¹ to less than 0.2 mg L⁻¹, which met the PRC discharge standard (GB/21900-2008) of electroplating pollutants. Graphical abstract
اظهر المزيد [+] اقل [-]Characteristics and performance of Cd, Ni, and Pb bio-adsorption using Callinectes sapidus biomass: real wastewater treatment النص الكامل
2019
Foroutan, Rauf | Muḥammadī, Riz̤ā | Farjadfard, Sima | Esmaeili, Hossein | Saberi, Maryam | Sahebi, Soleyman | Dobaradaran, Sina | Ramavandi, Bahman
In the current study, the bio-adsorption potential of Callinectes sapidus biomass for control of cadmium, nickel, and lead from the aqueous stream was assessed. Spectrum analysis of FTIR, AFM, EDAX, mapping, SEM, TEM, and XRF was used to study the properties of the C. sapidus biomass. The XRF analysis revealed that C. sapidus bio-adsorbent has various effective metal oxides that can be useful to adsorb pollutants. The best model to describe the equilibrium data was Freundlich isotherm. The Langmuir bio-adsorption capacity was reported at 31.44 mg g⁻¹, 29.23 mg g⁻¹, and 29.15 mg g⁻¹ for lead, cadmium, and nickel ions, respectively. Pseudo-first-order and pseudo-second-order kinetic models were studied to test the kinetic behavior of the process. An intra-particle diffusion model was used to determine the effective mechanisms involved in the bio-adsorption. Based on t₁/₂, it can be concluded that the equilibrium speed of the bio-adsorption process is high. The thermodynamic study showed that the metal bio-adsorption process using C. sapidus biomass is exothermic and spontaneous. The field applicability of the crab bio-adsorbent for eliminating concurrently several contaminants (metal ions, antibiotics, sulfate, nitrate, and ammonium) from an actual wastewater was successfully examined.
اظهر المزيد [+] اقل [-]A critical review on the effects of zinc at toxic levels of cadmium in plants النص الكامل
2019
Rizwan, Muhammad | Ali, Shafaqat | Rehman, Muhammad Zia ur | Maqbool, Arosha
Increasing cadmium (Cd) pollution in agricultural soils has raised serious concerns worldwide. Several exogenous substances can be used to mitigate the toxic effects of Cd in plants. Zinc (Zn) is one of the essential plant micronutrients and is involved in several physiological functions in plants. Zn may alleviate Cd toxicity in plants owing to the chemical similarity of Zn with Cd. Published reports demonstrated that Zn can alleviate toxic effects of Cd in plants by increasing plant growth, regulating Cd uptake, increasing photosynthesis, and reducing oxidative stress. Literature demonstrated that the role of Zn on Cd accumulation by plants is very controversial and depends upon several factors including concentrations of Cd and Zn in the medium, exposure duration, plant species and genotypes, and growth conditions. This review highlights the role of Zn in reducing Cd toxicity in plants and provides new insight that proper level of Zn in plants may enhance plant resistance to excess Cd.
اظهر المزيد [+] اقل [-]The impact of particulate matter on allergy risk among adults: integrated exposure assessment النص الكامل
2019
Dėdelė, Audrius | Miškinytė, Auksė | Gražulevičienė, Regina
Exposure assessment is an important part in environmental epidemiology for determining the associations of environmental factors with health effects. One of the greatest challenges for personal exposure assessment is associated with peoples’ mobility during the day and spatial and temporal dynamics of air pollution. In this study, the impact of PM₁₀ (particulate matter less than 10 μm) on allergy risk among adults was assessed using objective methods of exposure assessment. The primary objective of the present study was to estimate personal exposure to PM₁₀ based on individual daily movement patterns. Significant differences between the concentration of PM₁₀ in different microenvironments (MEs) and personal exposure to PM₁₀ were determined. Home exposure accounted for the largest part of PM₁₀ exposure. Thirty-five percent of PM₁₀ exposure was received in other non-home MEs. Allergy risk increased significantly with increasing exposure to PM₁₀. Adults exposed to the highest levels of PM₁₀ exposure had a twice-higher risk of allergies than adults exposed to the lowest levels of PM₁₀ exposure. The study results have practical relevance for exposure assessment to environmental factors and its impact on health effects.
اظهر المزيد [+] اقل [-]How can the natural radiation background affect DNA integrity in angiosperm plant species at different altitudes in Rila Mountain (Southwest Bulgaria)? النص الكامل
2019
Climate changes and anthropogenic factors are the main factors contributing to the destruction of natural ecosystems. The aim of this study was to investigate the extent to which wild plants adapt to UV, gamma background, and gross beta activity, as well as the possible damage that can be recorded in plants growing at different altitudes in Rila Mountain. We used physicochemical, cytogenetic, and molecular methods. Our investigations were done on the nine plant species characteristic of the ecosystems in Rila Mountain at three altitudes: 1500 m, 1782 m, and 2925 m. The registered beta activity in the plants did not depend on the altitude of the habitats. Our results showed that wild plant species differ in their tolerance to the combined effect of UV and IR radiation as well as climate factors. The genotype plays a more important role than the difference in the habitat altitude. The comet assay adapted by us for these plant species showed that the DNA of Epilobium angustifolium L. (Onagraceae) growing at 1500 m was more susceptible to damage than that of Dactylis glomerata L. (Poaceae). Both these species growing at 1782 m did not show any increase in DNA damage evaluated as the level of DNA migration. The level of DNA damage in Pedicularis orthantha Griseb. (Orobanchaceae) at 2925 m was comparable to that at a lower altitude. Regarding the formation of micronuclei, grass species were more sensitive to UV- and IR-induced DNA damage than cereals. Our data imply the existence of specific protective mechanisms developed by plants to overcome DNA damage induced by stress factors.
اظهر المزيد [+] اقل [-]Induction of nuclear abnormalities in herring (Clupea harengus membras), flounder (Platichthys flesus), and Atlantic cod (Gadus morhua) collected from the southern part of the Gotland Basin—the Baltic Sea (2010–2017) النص الكامل
2019
Eight nuclear abnormalities of genotoxicity and cytotoxicity were studied in peripheral blood erythrocytes of herring (Clupea harengus membras), flounder (Platichthys flesus), and Atlantic cod (Gadus morhua) sampled (2010–2017) from the Polish and the Lithuanian Exclusive Economic Zones (EEZ) in the Baltic Sea. At all study stations, total genotoxicity (∑Gentox) was found to be higher than total cytotoxicity (∑Cytox). A significant time-related decrease in genotoxicity was detected in the Lithuanian EEZ (2015–2017), while in the Polish EEZ (2014–2016), the opposite tendency was revealed. The highest ∑Gentox and ∑Cytox values recorded in fish sampled at the study stations located relatively close to each other clearly indicate an increased environmental genotoxicity and cytotoxicity pressure for fish in these areas. Exceptionally high and high-level genotoxicity risks to herring followed by those to flounder and cod were determined at a higher percentage of the stations studied.
اظهر المزيد [+] اقل [-]Impacts of climate change on cereal farming in Tunisia: a panel ARDL–PMG approach النص الكامل
2019
We used an autoregressive distributed lag (ARDL) modeling to investigate the short- and long-term effects of climate change on Tunisian cereal farming. The Pooled Mean Group (PMG) estimation as well as Granger causality tests conducted on a regional panel of the country, covering a time horizon from 1975 to 2014, showed that climate change issues still persist in Tunisia, affecting negatively and increasingly the cereal output. This study proves that negative effects of climate are rather felt when there is a shortage of rainfall, whereas the current temperature levels are still in favor of cereal crop. The findings indicate that cereal farming requires a continuous technology pack deployment and a favorable climate. However, an unanticipated long-run relationship has been observed between cereal production and labor. As a result of this research, recommendations were built around two major strategies, namely yield improvement and farmers’ income stabilization to mitigate the unpredictable effects of climate change and hazardous events. The implementation of a production and regional specialization map and the adoption of an anti-drought insurance system in addition to compensation payment would be a suitable adaptation policy to climate change effects and for the sustainability of Tunisian agriculture.
اظهر المزيد [+] اقل [-]The detoxification of heavy metals from aqueous environment using nano-photocatalysis approach: a review النص الكامل
2019
Heavy metals are discharged into aquatic environment and causes serious problems to the environment, human’s health, and other organisms. The industrial effluents contain high concentration of heavy metals that should be treated by different technologies. Numerous technologies have been widely used for the remediation of heavy metals such as chemical precipitation, ion exchange, membrane filtration, adsorption, coagulation-flocculation, floatation, electrochemical treatment, bioremediation, and photocatalysis. Among these technologies, photocatalysis has gained much attention due to chemical, physical, and electrical properties of heterogeneous semiconductor nano-photocatalysis. Bismuth vanadate is an n-type semiconductor photocatalyst having 2.4 eV band gap that was widely used from several decades having three monoclinic, tetragonal, and tetragonal zircon structures, but it also have some limitation that can be overcome by modification with metals or non-metals to gain high removal efficiency of heavy metals. This modification can tune its photocatalytic properties like band gap, absorption capacity, and surface area resulting in high photocatalytic performance towards heavy metals detoxification.
اظهر المزيد [+] اقل [-]