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排序方式: 共有236条查询结果,搜索用时 46 毫秒
171.
172.
The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were investigated under varying aerobic solids retention time (SRTa) and in the presence/absence of anoxic (alternating) conditions. Two bench SBRs, reactor R1 and R2, were run in parallel for 150 d. Reactor R1 was operated in aerobic conditions while R2 operated in alternating anoxic/aerobic conditions. The feed (synthetic wastewater), temperature, hydraulic retention time and mixing were identical in both reactors. The SRTa in both reactors was, sequentially, set at four values: 5, 4, 3 and 2 d.Kinetic tests with the biomasses from both reactors were carried out to estimate the maximum specific growth rates (μmax) at each tested SRTa and decay rates, in both aerobic and anoxic conditions. The kinetic parameters of nitrifier were estimated through the calibration of a two step nitrification-denitrification activated sludge model.The results point to a slightly higher μmax,AOB and μmax,NOB in alternating conditions, while both μmax,AOB and μmax,NOB were shown not to vary in the tested range of SRTa (from 2 to 5 d) at 20 °C. They were relatively high when compared to literature data: 1.05 d−1 < μmax,AOB < 1.4 d−1 and 0.91 d−1 < μmax,NOB < 1.31 d−1. The decay coefficients of both AOB and NOB were much higher in aerobic (from 0.22 d−1 to 0.28 d−1) than in anoxic (0.04 d−1 to 0.16 d−1) conditions both in R1 and R2, which explained the higher nitrification rates observed in the alternating reactor. 相似文献
173.
Cocozza C Parente A Zaccone C Mininni C Santamaria P Miano T 《Waste management (New York, N.Y.)》2011,31(1):78-84
Residues of the marine plant posidonia (Posidonia oceanica, PO) beached in tourist zones represent a great environmental, economical, social and hygienic problem in the Mediterranean Basin, in general, and in the Apulia Region in particular, because of the great disturb to the bathers and population, and the high costs that the administrations have to bear for their removal and disposal.In the present paper, Authors determined the heating values of leaves and fibres of PO, the main offshore residues found on beaches, and, meantime, composted those residues with mowing and olive pruning wood. The final composts were characterized for pH, electrical conductivity, elemental composition, dynamic respiration index, phytotoxicity, fluorescence and infrared spectroscopic fingerprints.The aim of the paper was to investigate the composting and energy recovery of PO leaves and fibres in order to suggest alternative solutions to the landfill when offshore residues have to be removed from recreational beaches.The fibrous portion of PO residues showed heating values close to those of other biofuels, thus suggesting a possible utilization as source of energy.At the same time, compost obtained from both PO wastes showed high quality features on condition that the electrical conductivity and Na content are lowered by a correct management of wetting during the composting. 相似文献
174.
A new method of determining the composition of sediment/soil gases and their volatile organic compound (VOC) content is described. VOCs were collected in situ from intertidal sediments in the Menai Strait and surrounding areas. The sampling was performed using a portable sampler comprising a funnel coupled to a SPME fibre. Gases were extracted from the sediments using a small vacuum pump pulling 100 mL min(-1) at atmospheric pressure. Sixty one different compounds were detected in the samples, and their fluxes and concentrations were determined. The compounds were classified into groups: halogenated, sulfur containing compounds, aldehydes, BTEXs (benzene, toluene, ethyl benzene and xylene) and aliphatic hydrocarbons. Results of principal component analysis (PCA) showed that the chemical composition of extracted gas was influenced primarily by sediment type. Muddy anoxic sediments were dominated by halogenated and sulfur containing compounds and sandy sediments had more aldehydes and BTEXs. 相似文献
175.
Air pollutants and the characterization of the organic content of aerosol particles in a mixed industrial/semi-rural area in central Italy 总被引:1,自引:0,他引:1
Di Filippo P Riccardi C Gariazzo C Incoronato F Pomata D Spicaglia S Cecinato A 《Journal of environmental monitoring : JEM》2007,9(3):275-282
Both regulated and unregulated air pollutants were detected during an intensive seasonal sampling campaign in a mixed industrial/semi-rural area on the outskirts of Rome, Italy, at two sites located opposite a hospital waste incinerator, downwind according to the direction of the prevailing local winds. Concentrations of pollutants were significantly lower than in urban atmospheres. The composition of particulate organic material indicated a heavy biogenic impact, accompanied by a lower contribution from petroleum-related processes. Both PAH and nitro-PAH group compositions of particulates were used to assess the nature and relative importance of sources. Both sites showed that different and diffuse sources contributed to local pollution with a significant contribution from traffic, proving that the hospital waste incinerator was not the main pollution source in this area. Among unregulated compounds, a series of positional isomers of nitro-PAHs and other organic compounds associated with particulate matter were investigated. In particular, 1- and 3-nitrophenanthrene identification was carried out, and they proved to be the most abundant nitro-PAHs. 相似文献
176.
Minero C Bono F Rubertelli F Pavino D Maurino V Pelizzetti E Vione D 《Chemosphere》2007,66(4):650-656
This paper studies the pH effect on the photonitration of catechol, 1-naphthol, naphthalene, and benzene. The pH trend is influenced by the generation of HNO(2) and peroxynitrous acid (HOONO) upon nitrate photolysis. HNO(2) can be involved in a direct and an indirect nitration process. Direct nitration follows the pH distribution of HNO(2) (flexus around 3). Indirect nitration, possibly involving nitrosation+oxidation, would be highest around pH3. HOONO can be involved in electrophilic nitration, where the initial formation rate of the nitroderivatives is proportional to [H(+)], or take part in nitration directly, in which case a less important pH effect in photonitration is observed. The relative importance of the various nitration pathways for each substrate determines the resulting pH effect in photonitration upon nitrate photolysis. 相似文献
177.
Alpha-male paternity in elephant seals 总被引:3,自引:0,他引:3
A. Rus Hoelzel Burney J. Le Boeuf Joanne Reiter Claudio Campagna 《Behavioral ecology and sociobiology》1999,46(5):298-306
The aim of this study was to assess paternity of males that dominated mating in harems at northern (Mirounga angustirostris) and southern (M. leonina) elephant seal rookeries using DNA fingerprinting and microsatellite DNA analysis. Southern alpha males had greater reproductive
success than most northern alphas at similar-sized harems. Comparison of the relatedness between pups within harems also suggested
that fewer males achieved matings in the southern elephant seal population. This was consistent with behavioral observations
that suggest greater competition for mates in northern elephant seal harems. Reproductive success was consistent with estimates
of mating success in some cases, but lower than expected for some northern elephant seal alpha males. A lower reproductive
success than predicted from mating behavior may arise from a variety of factors including sperm competition, male sperm depletion
from frequent mating, or reduced fertility. The alternatives are discussed in the context of environmental and historical
factors.
Received: 17 August 1998 / Received in revised form: 28 March 1999 / Accepted: 30 May 1999 相似文献
178.
179.
Alberto MANNUCCI Giulio MUNZ Gualtiero MORI Claudio LUBELLO Jan A. OLESZKIEWICZ 《Frontiers of Environmental Science & Engineering》2015,9(6):988-994
The aim of this work is to identify the range of applicability of Arrhenius type temperature dependence for Ammonia Oxidizing Bacteria (AOB) subjected to temperature time gradients through continuous titrimetric tests. An innovative online differential titrimetric technique was used to continuously monitor the maximum biologic ammonia oxidation rate of the biomass selected in a pilot scale membrane bioreactor, as a function of temperature time gradients. The monitoring technique is based on the measurement of alkalinity and hydrogen peroxide consumption rates in two parallel reactors operated in non-limiting substrate conditions for AOB; both reactors were continuously fed with mixed liquor and in one of them AOB were inhibited with allylthiourea. The effects of temperature decrease rates in the range 1 to 4°C·h−1 were evaluated by controlling the titrimetric reactor in the temperature range 10°C–20°C. The dependence of growth kinetics on temperature time gradients and the range of applicability of Arrhenius model for temperature dependency of AOB growth kinetics were assessed. The Arrhenius model was found to be accurate only with temperature gradients lower than 2°C·h−1. The estimated Arrhenius coefficients (θ) were shown to increase from 1.07 to 1.6 when the temperature decrease rate reached 4°C·h−1. 相似文献
180.
Monti Flavio Bianchi Nicola Sforzi Andrea Leonzio Claudio Ancora Stefania 《Environmental science and pollution research international》2020,27(10):10236-10248
Environmental Science and Pollution Research - Due to its peculiarity to accumulate environmental contaminants, the osprey Pandion haliaetus is a sentinel species for the biomonitoring of... 相似文献