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961.
Romário J. da Silv Lizeth Carolina Mojica-Sánchez Filipe D.S. Gorz Graciela C. Pedro Bruna G. Maciel Gabriela P. Ratkovski Hérica D. da Roch Kamila T.O. do Nascimento Juan C. Medina-Llamas Alicia E. Chávez-Guajardo José J. Alcaraz-Espinoz Celso P. de Melo 《环境科学学报(英文版)》2021,33(2):62-73
We report the preparation of poly(3,4-ethylene dioxythiophene) (PEDOT)-modified polyvinylidene fluoride electrospun fibers and their use as a novel adsorbent material for the removal of the anionic dye Methyl Orange (MO) from aqueous media. This novel adsorbent material can be used to selectively remove MO on a wide pH range (3.0–10.0), with a maximum capacity of 143.8 mg/g at pH 3.0. When used in a recirculating filtration system, the maximum absorption capacity was reached in a shorter time (20 min) than that observed for batch mode experiments (360 min). Based on the analyses of the kinetics and adsorption isotherm data, one can conclude that the predominant mechanism of interaction between the membrane and the dissolved dye molecules is electrostatic. Besides, considering the estimated values for the Gibbs energy, and entropy and enthalpy changes, it was established that the adsorption process is spontaneous and occurs in an endothermic manner. The good mechanical and environmental stability of these membranes allowed their use in at least 20 consecutive adsorption/desorption cycles, without significant loss of their characteristics. We suggest that the physical-chemical characteristics of PEDOT make these hybrid mats a promising adsorbent material for use in water remediation protocols and effluent treatment systems. 相似文献
962.
Hill J Harris AW Manning M Chambers A Swanton SW 《Waste management (New York, N.Y.)》2006,26(7):758-768
The use of cement based materials will be widespread in the long-term management of radioactive materials in the United Kingdom. One of the applications could be the Nirex reference vault backfill (NRVB) as an engineered barrier within a deep geological repository. NRVB confers alkaline conditions, which would provide a robust chemical barrier through the control of the solubility of some key radionuclides, enhanced sorption and minimised corrosion of steel containers. An understanding of the dissolution of C-S-H gels in cement under the appropriate conditions (e.g., saline groundwaters) is necessary to demonstrate the expected evolution of the chemistry over time and to provide sufficient cement to buffer the porewater conditions for the required time. A programme of experimental work has been undertaken to investigate C-S-H gel dissolution behaviour in sodium chloride solutions and the effect of calcium/silicon ratio (C/S), temperature and cation type on this behaviour. Reductions in calcium concentration and pH values were observed with samples equilibrated at 45 degrees C compared to those prepared at 25 degrees C. The effect of salt cation type on salt-concentration dependence of the dissolution of C-S-H gels was investigated by the addition of lithium or potassium chloride in place of sodium chloride for gels with a C/S of 1.0 and 1.8. With a C/S of 1.0, similar increases in dissolved calcium concentration with increasing ionic strength were recorded for the different salts. However, at a C/S of 1.8, anomalously high calcium concentrations were observed in the presence of lithium. 相似文献
963.
Effects of the forced ventilation on composting of a solid olive-mill by-product ("alperujo") managed by mechanical turning 总被引:1,自引:0,他引:1
Cegarra J Alburquerque JA Gonzálvez J Tortosa G Chaw D 《Waste management (New York, N.Y.)》2006,26(12):1377-1383
The evaluation of the most suitable aeration technology for olive-mill by-product "alperujo" (AL) composting was carried out by using two identical piles prepared by mixing AL with a bulking agent (fresh cow bedding) and a mature compost (as inoculant). Forced ventilation was employed in conjunction with mechanical turning in one of the piles, whereas only mechanical turning was used in the other pile. These two treatment methods were evaluated by assessing process efficiency and end-product quality. The results show that the composting process was completed in less time when forced ventilation was coupled with mechanical turning. A slight delay in the evolution of pH, C/N ratio, and biodegradation of fats and organic matter was observed when only turning was employed. However, the recommended method for composting AL was mechanical turning without forced ventilation since the composition of the end-product in this case was comparable to the composted AL using forced ventilation coupled with mechanical turning. Furthermore, there were substantial economic savings by selecting mechanical turning alone, which included capital costs for equipment. 相似文献
964.
Blenkharn JI 《Waste management (New York, N.Y.)》2006,26(3):315-317
Medical (clinical) wastes are costly in disposal and carry risks of infection, or physical injury, and of exposure to potentially harmful pharmaceuticals, as well as being aesthetically unacceptable. Technological advances in disposal, together with the introduction of rigorous emission standards for incinerators and similarly stringent control standards for non-burn “alternate” disposal technologies, continue to drive improvements in waste management. Are these improvements attainable in developing countries?Where adequate resources and a robust infrastructure are lacking, investment in advanced disposal technologies may be counterproductive. Developments must be appropriate to and manageable by the communities served; sustainable low-technology approaches may be preferable. There remains a need for affordable technical innovation, as well as underlying political support and international financial and technical assistance, to sustain meaningful improvements in waste management in remote and isolated regions and more generally in developing countries. 相似文献
965.
The monitoring of the odor annoyance generated by a landfill area is difficult, since it is a multi-area-sources problem, with a discontinuous odor emission. This paper proposes an adaptation of the method of sniffing team campaigns to the particular case of fresh waste odors. The method is based on the field determination of odor perception points, followed by data processing with a bi-Gaussian-type model, adapted to handle the odors. In a first step, field observers delineate the region in which odor impact is experienced and then the emission rate is manipulated in a dispersion model until the predicted size of the impact zone matches that observed in the field. In a second step the adjusted emission rate is entered into the model to calculate the percentiles corresponding to the average annoyance zone. The originality of the proposed method is the introduction of all observation points and of all recorded meteorological data into the model. The paper discusses the method limitations and the errors induced on the results, i.e. the odor emission rate and the percentile lines (or iso-concentration lines) which are used to describe the odor concentrations on a map of the surroundings of the plant. The proposed method proves to be reliable for diffuse sources, such as landfill areas. The obtained results are coherent with other results found in the literature with other techniques. 相似文献
966.
Frede Ø. Andersen Michael Jørgensen Henning S. Jensen 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):465-474
One of the methods to diminish the internal phosphorus (P) loading is inactivation of P by aluminum (Al). After addition of
Al to lake water an Al(OH)3 floc is formed, which settles to the bottom and initially form a lid on the sediment surface. The effects of Chironomus
plumosus larvae on sediment nutrient fluxes and P binding-sites in the sediment after addition of Al were tested. C.
plumosus larvae were added to sediment cores in which sediment–water fluxes of nutrients were measured four times. After one month,
the sediment was sectioned with depth and P fractions were measured by sequential chemical extraction. The chironomids created
burrows through the Al layer which caused a significantly increased efflux of P from the Al treated sediment, because the
P had only limited contact to the added Al. The chironomids also affected the P fractions in the sediment by their bioturbating
activity. Thus, they caused increased Al concentrations in the upper part of the Al treated sediment. This created an enhanced
contact between Al and P in the upper 7 cm of the sediment and, as a result, an increased binding of P to Al and a lowered
porewater P. The DIP efflux is therefore expected to be lowered after the initial phase. Al had no effects on the nitrogen
fluxes, but the chironomids enhanced the release, and decreased the release or increased the uptake by the sediments. 相似文献
967.
J. Hejzlar K. Šámalová P. Boers B. Kronvang 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):487-494
Steady-state models for the prediction of P retention coefficient (R) in lakes were evaluated using data from 93 natural lakes and 119 reservoirs situated in the temperate zone. Most of the
already existing models predicted R relatively successfully in lakes while it was seriously under-estimated in reservoirs. A statistical analysis indicated the
main causes of differences in R between lakes and reservoirs: (a) distinct relationships between P sedimentation coefficient, depth, and water residence
time; (b) existence of significant inflow–outflow P concentration gradients in reservoirs. Two new models of different complexity
were developed for estimating R in reservoirs: , where τ is water residence time (year), was derived from the Vollenweider/Larsen and Mercier model by adding a calibrated parameter
accounting for spatial P non-homogeneity in the water body, and is applicable for reservoirs but not lakes, and , where [Pin] is volume-weighted P concentration in all inputs to the water body (μg l−1), was obtained by re-calibrating the OECD general equation, and is generally applicable for both lakes and reservoirs. These
optimised models yield unbiased estimates over a large range of reservoir types. 相似文献
968.
William J Long Ronald E Majors 《环境化学》2006,25(3):381-383
大气中的挥发性羰基化合物可以通过2,4-二硝基苯肼(DNPH)原位衍生化而被捕集.采用反相HPLC 可以洗脱和分析这些羰基衍生物.本文采用该方法监测了美国佛蒙特州大气样品中的痕量甲醛、乙醛和丙酮. 相似文献
969.
Environmental assessment of mercury dispersion, transformation and bioavailability in the Lake Victoria Goldfields, Tanzania 总被引:2,自引:0,他引:2
Environmental dispersion and transformation of mercury discharged from gold mining operations has been investigated in field and laboratory studies in order to provide better understanding of the degree of mercury (Hg) pollution and bioavailability in the Lake Victoria goldfields (LVGF) ecosystems. This paper reviews results already published elsewhere and presents additional data on Hg dynamics in the LVGF. Studies conducted at the Mugusu and Rwamagaza artisanal mines indicated different degrees of Hg contamination and dispersion in environmental matrices. Mercury concentration in contaminated river sediments near the Mugusu mine varied from 6.0 to 0.5 mg/kg on a dry weight basis. The highest Hg contamination levels (165-232 mg/kg) were associated with mine tailings at the Rwamagaza mine. Mercury concentrations in fish representing different dietary habits on the southwestern shore of Lake Victoria at the Nungwe Bay were very low (2-35 microg/kg) and thought to represent background levels. These and other results suggested that the use of Hg in gold extraction in the LVGF has not caused high Hg levels in lake fish. The study of Hg in lichens showed Parmelia lichen to be an effective bioindicator for atmospheric Hg contamination due to Hg emissions from gold-amalgam firing and purification operations. The Hg levels in the lichens around the Mugusu mine ranged from 3.1 to 0.1 microg/g; the highest levels were recorded in the lichens sampled close to gold-amalgam processing sites. The regional background level in the Parmelia lichen was 0.05-0.10 microg/g, with a mean level of 0.07 microg/g. Studies of Hg transformation in the mine tailings revealed unexpectedly high methylmercury (MeHg) levels in the tailings (629-710 ng/g), which indicated that oxidation and methylation of metallic Hg in the tailings occurred at significant levels under tropical conditions. Re-equilibration of the tailings with freshwater (FW) indicated the MeHg was firmly bound in the tailings and therefore very little MeHg was released to the water column (0.2-1.5 ng/L). The methylation of Hg in tropical loamy clay soil contaminated with HgCl(2) (5 mg Hg/kg) yielded MeHg concentrations of 11 and 14 ng/g when inundated with seawater and FW, respectively, for 4 weeks. Little MeHg was transferred from the soil to the equilibrated water (< or = 0.4 ng/L). Atmospheric exposure of the soil pre-inundated with FW resulted in net degradation of MeHg during the 1st week of exposure, followed by net production and accumulation of MeHg in the soil (up to 15.5 ng/g) during atmospheric desiccation. Mercury uptake by fish from the Hg(0)-contaminated aquatic sediment-tailings system in the aquarium experiment was found to be low, suggesting the low availability of MeHg for bioaccumulation in the system. These and other results provide useful insights into Hg transformation, mobility and bioavailability in tropical aquatic systems affected by Hg pollution from gold mining operations. 相似文献
970.
Fish mercury increase in Lago Manso, a new hydroelectric reservoir in tropical Brazil 总被引:3,自引:0,他引:3
Hylander LD Gröhn J Tropp M Vikström A Wolpher H de Castro E Silva E Meili M Oliveira LJ 《Journal of environmental management》2006,81(2):155-166
It has been frequently demonstrated that mercury (Hg) concentrations in fish rise in newly constructed hydroelectric reservoirs in the Northern Hemisphere. In the present work, we studied whether similar effects take place also in a tropical upland reservoir during impoundment and discuss possible causes and implications. Total Hg concentrations in fish and several soil and water parameters were determined before and after flooding at Rio Manso hydroelectric power plant in western Brazil. The Hg concentrations in soil and sediment were within the background levels in the region (22-35 ng g(-1) dry weight). There was a strong positive correlation between Hg and carbon and sulphur in sediment. Predatory fish had total Hg concentrations ranging between 70 and 210 ng g(-1) f.w. 7 years before flooding and between 72 and 755 ng g(-1) f.w. during flooding, but increased to between 216 and 938 ng g(-1) f.w. in the piscivorous and carnivorous species Pseudoplatystoma fasciatum, cachara, and Salminus brasiliensis, dourado, 3 years after flooding. At the same time, concentrations of organic carbon in the water increased and oxygen concentrations decreased, indicating increased decomposition and anoxia as contributing to the increased Hg concentrations in fish. The present fish Hg concentrations in commonly consumed piscivorous species are a threat to the health of the population dependent on fishing in the dam and downstream river for sustenance. Mercury exposure can be reduced by following fish consumption recommendations until fish Hg concentrations decrease to a safe level. 相似文献