Search results for "ORGANIC MATTER"
showing 10 items of 577 documents
Carbon decomposition of the topsoils and soil fractions under forest and pasture in the western Brazilian Amazon basin, Rondonia
2000
The topsoils of two sites, comprising natural forest and 4- and 20-year-old pastures, respectively, were selected in Rondonia to evaluate the changes of soil organic matter due to pasture establishment. These changes were evaluated by measuring the proportions of the C and N associated with clay and silt fractions, and by the C decomposition (CD) rate of the whole topsoils and their size fractions. The topsoils studied had large proportions of C and N associated with fine fractions, especially with clay fractions. The CD rate of the silt fractions was higher than that of the clay fractions under the two forest topsoils and under the 20-year-old pasture. The CD rate of the silt fractions und…
DESASS: A software tool for designing, simulating and optimising WWTPs
2008
This paper presents a very useful software tool to design, simulate and optimise wastewater treatment plants. The program is called DESASS (DEsign and Simulation of Activated Sludge Systems) and has been developed by CALAGUA research group. The mathematical model implemented is the Biological Nutrient Removal Model No.1 (BNRM1) which allows simulating the most important physical, chemical and biological processes taking place in treatment plants. DESASS calculates the performance under steady or transient state of whole treatment schemes including primary settlers, volatile fatty acid generation systems by primary sludge fermentation, activated sludge systems for biological organic matter a…
Experimental organic matter maturation at 2kbar: Heat-up effect to low temperatures on vitrinite reflectance
2012
Abstract An experimental study was performed to evaluate the effect of heat-up to various low temperatures on vitrinite reflectance ( VR ) at 2 kbar employing the same previously used heat-up procedures, starting material and apparatus. Heat-up is the isobaric experimental procedure consisting of the increase in temperature of the laboratory vitrinite maturation from room temperature to the desired run temperature T end of heat-up at which the isobaric-isothermal maturation starts. Experiments employed cold-seal pressure vessels with classical heat-up devices and were carried out on wet (water added) xylite of swamp cypress. Confined system maturation experiments were conducted at 2 kbar an…
Screening pretreatment methods to enhance thermophilic anaerobic digestion of pulp and paper mill wastewater treatment secondary sludge
2013
Abstract The effect of hydrothermal (150 °C for 10 min and 70 °C for 40 min), enzymatic (Accelerase 1500, 0.07 g/g volatile solids (VS)), ultrasound (45 kHz for 30 min) and chemical pretreatments (HNO3 at pH 3 and NaOH at pH 12) alone or in combination on the chemical composition and methane yield of the pulp and paper mill secondary sludge was studied in batch assays at 55 °C. In total, 12 different pretreatment combinations were compared. Chemical analyses showed that all pretreatments except for HNO3 and ultrasound pretreatments improved the organic matter solubilization. Among the studied pretreatments, hydrothermal (150 °C, 10 min) pretreatment alone or in combination with enzymatic an…
Wastewater modification processes in a stabilization reservoir: a new mathematical model
2018
The paper presents a mathematical model for the simulation of the ecology of a wastewater stabilization reservoir (WSR). WSRs are hypertrophic aquatic systems devoted to water storage in warm countries where shortage conditions are often encountered. Several factors that affect the stabilization reservoir’s effluent quality were taken into account: hydraulics and hydrology, solar radiation, reaeration, algae, zooplankton, organic matter, pathogens, and sediment-water interactions. The model quantifies the specific influence of each factor on effluent quality, and evaluating the correlation between the different factors. State variables included in the model were: algae, dissolved oxygen, or…
Influence of anthropogenic activity on the lead isotope signature of Thau Lake sediments (southern France): origin and temporal evolution
2000
Lead concentrations and isotopic compositions were determined on both bulk sediments deposited in the Thau lake in southern France during the last 200 years, and leachates derived from a series of sequential leachings of the sediments, making it possible to identify the sources, natural (i.e. indigenous lithologic) or anthropogenic, and to quantify the different inputs of Pb. Two distinct inputs of Pb could be distinguished. One of these corresponds to the terrigenous material entering the basin, representative of the local natural Pb ‘background’. Its supply remained steady most of the time with 206Pb/207Pb ratios of 1.200±0.003, except at the time of heavy storms producing voluminous and …
Sur la présence de matières organiques mésocénozoïques dans des humus actuels (bassin de Chaillexon, Doubs, France)
1998
Abstract The optical analysis in the Chaillexon watershed (Doubs, France), of the present soils' humus layers' organic matter points out the contribution of Meso-Cenozoic organic matter in addition to the one produced by vegetal cover. Their relative occurrence varies in each layer: in the reverse of that of vegetal organic matter, the relative amount of Meso-Cenozoic organic matter increases according to the depth. That result shows that the total organic matter amounts in soils (and its evaluation) do not only depend on the net primary production and that geological formations have to be taken into account. Moreover, it suggests that present and past detrital supplies are concerned with ‘…
The influence of weathering processes on labile and stable organic matter in Mediterranean volcanic soils
2008
The relationship and mechanisms among weathering processes, cation fluxes, clay mineralogy, organic matter composition and stability were studied in soils developing on basaltic material in southern Italy (Sicily). The soils were transitions between Phaeozems and Vertisols. Intense losses of the elements Na, Ca and Mg were measured indicating that weathering has occurred over a long period of time. The main weathering processes followed the sequence: amphibole, mica, volcanic glass or if ash was the primary source→smectite→interstratified smectite–kaolinite→kaolinite. Kaolinite formation was strongly related to high Al, Mg and Na losses. The good correlation between oxyhydroxides and kaolin…
Non-hydrolysable macromolecular constituents from outer walls of Chlorella fusca and Nanochlorum eucaryotum
1992
Abstract Many green microalgae possess a thin trilaminar outer wall (TLS) with a very high resistance to chemical degradation. TLS are known to play an important protective role in living cells. They are also selectively preserved during fossilization and thus provide a major contribution to the fossil organic matter of a number of sedimentary rocks. However, little information is available on TLS chemical structure. Examination of the TLS of Chlorella fusca (a lacustrine Chlorophycea) and of Nanochlorum eucaryotum (a recently discovered marine Chlorophycea) indicated that (i) they exhibit morphological features commonly observed in other green microalgae, (ii) their non-hydrolysable macrom…
Microfungal community structure in anthropogenic birch stands in central Finland
2002
We describe the soil microfungal communities in 30-year-old birch (Betula pendula Roth) stands planted either on former spruce forest soil (BS) or on former arable soil (BF) and compare these with the soil microfungal communities in spruce forests (S), arable fields (F) and old deciduous forests (D). Fungi were isolated from 0- to 3-cm and 3- to 6-cm samples collected in September 1997 and May 1998. Principal components analysis differentiated fungal communities in the S and BS sites from those in the other site types. The Morisita-Horn index of similarity indicated that fungal communities in the F and BF sites were less similar to those in the other site types. Fungal communities of the BS…