Use of thermal analysis techniques (TG-DSC) for the characterization of diverse organic municipal waste streams to predict biological stability prior to land application

The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO₂ respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts.     

Combined photo-Fenton and biological oxidation for pesticide degradation: effect of photo-treated intermediates on biodegradation kinetics

Biodegradability of a partially photo-oxidized pesticide mixture is demonstrated and the effect of photo-Fenton treatment time on growth and substrate consumption of the bacteria Pseudomonas putida CECT 324 is shown. Four commercial pesticides, laition, metasystox, sevnol and ultracid, usually employed in citric orchards in eastern Spain, were chosen for these experiments. The active ingredients are, respectively, dimethoate, oxydemeton-methyl, carbaryl and methidathion. Judging by biomass measurements, dissolved organic carbon measurements and biodegradation efficiency, it may be concluded that 90min相似文献   

Physiological responses to atmospheric fluorine pollution in transplants of Pseudoscleropodium purum

Transplants of the moss Pseudoscleropodium purum were placed under shade, and with an auto irrigation system, at five sites in the surroundings of an aluminium smelter to enable study of the possible effects of F on different physiological parameters after exposure periods of 28 and 56 days. Reference thresholds for the content of Chl a+b and for the pigment indexes of Chl a/b and D665/D665a were established with the data corresponding to 22 transplants of each duration of exposure, at seven sites where there was little or no contamination by F. The highest determination coefficients for the levels of F in moss were those obtained for chlorophyll content (Chl a+b) and the D665/D665a pigment index, with the effects being most evident in the transplants exposed to the contamination for 56 days.     

Long-term geochemical evolution of the near field repository: insights from reactive transport modelling and experimental evidences

The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept.In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral content. Results from the simulations indicate that pore water chemistry is controlled by the equilibrium with the accessory minerals, especially carbonates. pH is buffered by precipitation/dissolution of calcite and dolomite, when present. The equilibrium of these minerals is deeply influenced by gypsum dissolution and cation exchange reactions in the smectite interlayer. If carbonate minerals are initially absent in bentonite, pH is then controlled by surface acidity reactions in the hydroxyl groups at the edge sites of the clay fraction, although its buffering capacity is not as strong as the equilibrium with carbonate minerals. The redox capacity of the bentonite pore water system is mainly controlled by Fe(II)-bearing minerals (pyrite and siderite). Changes in the groundwater composition lead to variations in the cation exchange occupancy, and dissolution–precipitation of carbonate minerals and gypsum. The most significant changes in the evolution of the system are predicted when ice-melting water, which is highly diluted and alkaline, enters into the system. In this case, the dissolution of carbonate minerals is enhanced, increasing pH in the bentonite pore water. Moreover, a rapid change in the population of exchange sites in the smectite is expected due to the replacement of Na for Ca.     

Phylogeny and biogeographic history of hake (genus Merluccius), inferred from mitochondrial DNA control-region sequences

 Phylogenetic analyses of the left domain of the mitochondrial DNA control-region sequence have been used to examine the relationships among species of the genus Merluccius (Rafinesque, 1810), and to compare these with hypotheses based on morphological, meristic and allozyme characters. Analysis of aligned sequences revealed that transition bias was much lower than in mammalian mtDNA, and that nucleotide composition of control-region sequences was biased toward A and T. We have roughly calibrated a molecular clock for the genus, based on the rise of the Isthmus of Panamá, which is believed to have created a barrier to dispersal between marine species of the Atlantic and Pacific Oceans. Our mtDNA-based phylogeny was highly congruent with allozyme-based phylogenies, but poorly so with a previously described phylogeny based on morphology. Specifically, our phylogeny resolved two well-supported principal clades, one of American (west Atlantic and east Pacific) species and the other of Euro–African (east Atlantic) species. This suggests an evolutionary history during which the ancestral lineage of Merluccius was divided between two geographic regions, with subsequent dispersal and vicariant events resulting in the evolution and distribution of extant taxa. However, the relationships between some taxa within the American clade could not be resolved. We suggest that this is consistent with an hypothesis of a rapid origin and radiation of these taxa. Received: 12 December 1998 / Accepted: 15 October 1999     

Evaluation and comparison of advanced oxidation processes for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D): a review

Environmental Science and Pollution Research - Organochlorine pesticides have generated public concern worldwide because of their toxicity to human health and the environment, even at low...     

Uranium transfer phenomena in rock matrix: petrophysical and geochemical study of El Berrocal experimental site, Spain

The role played by the petrophysical characteristics of the rock matrix in the radioelement transfer phenomena through the geosphere is considered. The aim of this paper is to correlate information provided by the microcrack network, mineralogy and U-micromapping studies which can be used to quantify the extent of radioelement migration/retention in the granite. This study is part of an interdisciplinary research project on the El Berrocal site (Spain), which forms part of the R & D Programme “Management and Disposal of Radioactive Waste” of the Commission of the European Communities.The experimental procedure combines complementary microscopic techniques: polarizing light, fluorescence, confocal laser scanning, acoustic, scanning electron microscopy and uranium-induced fission-track micromapping. All of these techniques are applied for quantifying the rock matrix characteristics.Data on preferential fissure zones in relation to mineralogy, and the correlation between these data and uranium microdistribution are obtained. These results are discussed in terms of radionuclide mobility and can be used, with other information, for evaluating the retardation capacity of the crystalline rock matrix around a high-level radioactive waste repository.     

Phytoplankton and pigment distributions in an anticyclonic slope water oceanic eddy (SWODDY) in the southern Bay of Biscay

An anticyclonic slope water oceanic eddy (SWODDY), named AE6, was sampled in the southern Bay of Biscay from 12 to 31 August 1998 to assess changes in the abundance and composition of phytoplankton assemblages related to the mesoscale feature. SWODDY AE6 showed characteristic biological signatures. A twofold increase in chlorophyll a concentration was found at the eddy centre relative to surrounding waters. Picoplankton cells accounted for a lower fraction of total chlorophyll a values at the eddy centre (44–50%) than outside the eddy (54–61%). Microscopic cell counts and HPLC pigment analysis showed that diatoms were almost entirely confined to the eddy centre, but both techniques yielded different results when studying other phytoplankton groups. Microscopic cell counts indicated that the spatial distribution of diatoms, dinoflagellates and unidentified flagellates was significantly influenced by SWODDY AE6, showing maximum abundance inside the mesoscale feature. HPLC pigment analysis provided more detailed information about the composition of pico–nanoplanktonic organisms. Pigment data processed by means of the CHEMTAX program showed "chlorophytes", "haptophytes" and "dinoflagellates II" (having haptophyte-like pigments and gyroxanthin-diester) as the more abundant "pigment classes" at the eddy centre, whereas dominance of "chlorophytes" and higher contribution of "cyanobacteria" (type Synechococcus) were estimated in the surrounding waters.Communicated by S.A. Poulet, Roscoff     

Feeding ecology of the three juvenile phases of the spiny lobster<Emphasis Type="Italic"> Panulirus argus</Emphasis> in a tropical reef lagoon

The three juvenile phases of the spiny lobster Panulirus argus (algal phase: 5-15 mm carapace length, CL; postalgal phase: 15-45 mm CL, and subadults: 45-80 mm CL) occur in the reef lagoon at Puerto Morelos, Mexico. The algal phase abounds in this lagoon, which is covered by extensive seagrass-algal meadows, but the density of postalgal and subadult juveniles is low, owing to the scarcity of crevice-type shelters suitable for these phases. The feeding ecology of the three juvenile phases was investigated to examine whether spatial or temporal differences in food intake, diet composition, or nutritional condition occurred among phases and could partially account for the low abundance of the larger juveniles. Juveniles were collected by divers at night, from January to November 1995, throughout the mid-lagoon and back-reef zones. Percent stomach fullness, relative weight of the digestive gland (RWDG, an index of nutritional condition), percent frequency of occurrence and percent volume of food categories in the diet were compared between sexes, juvenile phases, molt stages (postmolt, intermolt, premolt), seasons, and sampling zones (mid-lagoon and back-reef zones). Significant differences in stomach fullness occurred only among molt stages, mainly because postmolt individuals had emptier stomachs. The main food categories in all juvenile phases were crustaceans (mostly hermit crabs and brachyurans) and gastropods, but the food spectrum was wide, including many other animal taxa as well as plant matter. In June 1995, the epibenthic macrofauna was sampled in five sites in the lagoon that differed in their amount of vegetation. The most abundant taxa in all sites were decapods and gastropods, but density and diversity measures showed that the distribution of these potential prey taxa for juvenile P. argus was rather patchy. Diet overlap in juvenile lobsters was high between sexes, juvenile phases, sampling zones, seasons, and molting stages, indicating that all juveniles fed on the same general food categories throughout time. The only factor that affected the RWDG was the juvenile phase. RWDG was significantly lower in subadults than in algal and postalgal phases, suggesting a poorer nutritional condition in the largest juveniles. This may be related to the scarcity of suitable shelters for large juveniles throughout the lagoon, which may preclude subadults from exploiting food resources in areas of the lagoon where shelter is limited.     

Patterns of seagrass (Posidonia oceanica) flowering in the Western Mediterranean

The intensive reconstructive sampling (1957–2004, 39 localities), a systematic direct observation (1992–2004, 1 locality) and particular direct observations (66 localities) of Posidonia oceanica meadows were analysed together with temporal series of flowering available in the literature (19 localities). This allowed the examination of temporal and spatial variability in annual flowering prevalence (FP, the fraction of meadows flowering in a given year) and of annual meadow flowering intensity (FI, number of inflorescences per shoot) for the period 1979–2004 across the Western Mediterranean, as well as spatial variability of flowering frequency (FF, the fraction of years that a given meadow has flowered) and shoot flowering probability (Pf, fraction of flowering stalks appeared per annual segment). Each year, on an average 17% of the investigated meadows flowered, ranging from 3 to 86% of meadows among the years. The highest annual FP and FI values were obtained in 2003 (FP=0.86 and mean FI=0.23±0.03 inflorescences shoot⁻¹). A secondary peak of FP and mean FI occurred 9 years earlier, in 1994 (FP=0.44 and mean FI=0.08±0.02). Both peaks of flowering occurred after hot summers. Flowering synchrony in particular years across the Western Mediterranean and clines of increased meadow flowering frequency towards the North and East, suggests the existence of large-scale environmental mechanisms controlling the floral induction. On the other hand, meadow FF and Pf were highly heterogeneous among and within the meadows, indicating that local factors also may play a significant role in flowering induction. When flowering, the Western Mediterranean meadows showed an average 0.11±0.02 inflorescences shoot⁻¹, but FI greatly varied among and along the series (from 0.002 to 0.54 inflorescences shoot⁻¹) and decreased significantly with depth but was independent of meadow shoot density and meadow latitude or longitude. The shoot flowering probability was quite low (0.007±0.002 inflorescences shoot⁻¹ year⁻¹) and exponentially increased with shoot age.