Spéciation du Carbone, de l'Azote et du Phosphore de différentes boues de stations d’épuration au cours de leurs incubations contrôlées dans deux types de sol

La caractérisation des particularités des boues de station d'épuration des eaux et la problématique agro - économique et environnementale liée à leur élimination, ont constitué les motivations principales de ce travail. La première partie de ce travail est destinée à mesurer la qualité du carbone des boues, à évaluer sa vitesse de dégradation et à établir des relations entre la qualité de la matière organique et sa dégradation afin d'expliquer et de prévoir le comportement du carbone des boues dans deux sols fréquemment répandus dans la région du Midi-Pyrénées. Dans une seconde partie, la vitesse de minéralisation de l'azote des boues a été déterminée, ainsi que son potentiel de volatilisation. Afin de conclure l'étude sur le carbone et l'azote, l'effet de la taille des particules sur la dynamique de dégradation a été évalué. Finalement, l'évolution des phosphates provenant des boues a été étudiée durant une expérience d'incubation et leur analyse a été effectuée. La spéciation chimique, l'extraction séquentielle, les analyses de routine (Olsen, Bray 1, Mehlich 3) et l'extraction par la plante ont été choisies comme méthodes de caractérisation du P. La composition densimétrique de la matière organique a permis d'expliquer les différences observées dans le dégagement de CO2. L'émission du CO2 a montré une relation étroite avec la quantité de carbone dans la fraction de densité intermédiaire du carbone exogène. La mineralisation de l'azote des boues est conditionnée par la proportion d'azote ammoniacal, la relation C:N de la boue et par la proportion de carbone dans la fraction intermédiaire. La volatilisation est en relation directe avec la proportion d'azote ammoniacal et inversement proportionnelle à la relation C : N de la boue. Les expériences réalisées afin de déterminer l'effet de la taille des particules ont montré l'efficacité de ce paramètre en tant qu'outil pour determiner la vitesse de décomposition d'une boue. Les sources de P testées ont montré des différences principalement en relation aux fractions de P du sol enrichi. Le phosphate et la boue chaulée sont les deux sources qui ont le plus enrichi la fraction la plus mobile. Parmi les analyses de routine, la méthode Mehlich-3 a été confirmée comme la plus adaptée à la détermination de changements dans la bio-disponibilité du phosphore dans des sols recevant des boues. ABSTRACT : Behaviour of Carbon, Nitrogen and Phosphorus present in different biosolids in the soil. The aim of this work was the characterization of the biosolids and of the agricultural, economical and environmental problematic derived from their elimination. The first part of this work is focused in measuring the quality of the organic carbon present in the biosolids, its degradation speed, as well as to establish the relationships between both of them in order to explain and predict the behaviour of the carbon of the biosolids in the two soils most frequent in the region. In the second part, the mineralization speed and the potential volatilization of the nitrogen of the biosolids were determined. In order to finish the study on carbon and nitrogen, the effect of particle size on the degradation dynamics was evaluated. Finally, the evolution of phosphates of the biosolids was determined by means of an incubation experiment and the corresponding analyses. To characterize the P, the methods chosen were the chemical fractionation, sequential extraction, routine analyses (Olsen, Bray 1, Mehlich 3), and vegetal extractions. Organic matter densitometric composition explained the differences that were observed in the emission of C-CO2. This last aspect was tightly related to the quantity of carbon in the intermediate density fraction of exogenous carbon. The availability of the nitrogen in biosolids depends on the proportion of nitrogen in ammonium form, the ratio C:N of the biosolids and by the proportion of carbon in the intermediate fraction. The volatilization is directly proportional to the fraction of ammonia nitrogen and inversely proportional to the ratio C:N in the biosolids The experiments carried out to ascertain the effect of the particle size showed the efficiency of this parameter to control the decomposition speed of a biosolid. The different sources of P that were tested showed differences, mainly in relation to how the different fractions of P in the soil increased. Phosphate and limed biosolids were the two sources that most augmented the most labile fraction. Among the different routine analyses, the Mehlich-3 method was confirmed as the best fit to ascertain the changes in the bioavailability of phosphorus in the soils receiving biosolids

Agronomic and environmental impacts of a single application of heat-dried sludge on an Alfisol

A field experiment was conducted on Alfisols in South-West France to assess the agronomic and environmental impacts of a single application of heat-dried sludge pellets at 11.1 Mg dry matter ha-1. The sludge pellets, with a moisture level of 9.5%, were spread on an irrigated crop of maize (Zea mays L.). This treatment was compared with inorganic fertilization (urea and diammonium phosphate mixed with KCl). Soil properties, yield and the composition of maize and the quality of drained water were monitored over 1 year to detect any changes resulting from sludge application. Amongst several determined soil properties, only two were significantly modified by the sludge application: The nitric nitrogen stock of the soil was higher in the inorganic fertilized plot, whereas Olsen-P soil content was higher in the sludge-amended plot. Agronomic recovery rates of N and P added by sludge were high: For the first crop following application, total amounts of N and P supplied by the sludge had the same efficiency as approximately 45% of the N and P amounts supplied by inorganic fertilizer. This ratio was 7% for the N uptake by the second maize crop. The quality and quantity of maize were equally good with both types of fertilization. During the 2 years following sludge spreading, N leaching remained as low in the sludged plot as in the inorganically fertilized one. The Cu, Zn, Cr, Cd, Pb and Ni composition of the drainage water was affected by neither of the types of amendment. From the heavy-metal contents of the soil, water and maize monitored over 1 year in the field experiment and from literature data for cow manure and atmospheric emissions, a theoretical balance between crop soil heavy-metal input and output over one century was drawn up. The long-term impact of cow manure on Zn, Ni and Cr in soil is higher than that of the studied heat-dried sludge. Obviously, sludge tended to cause a strong increase in soil Cu storage, valued for these soils, which are otherwise very Cu deficient

Spéciation du carbone, de l'azote et du phosphore de différentes boues de stations d'épuration au cours de leurs incubations contrölées dans deux types de sol

La caractérisation des particularités des boues de station d'épuration des eaux et la problématique agro-économique et environnementale liée à leur élimination, ont constitué les motivations principales de ce travail. la première partie de ce travail est destinée à mesurer la qualité du carbone des boues, à évaluer sa vitesse de dégradation et à établir des relations entre la qualité de la matière organique et sa dégradation afin d'expliquer et de prévoir le comportement du carbone des boues dans deux sols fréquemment répandus dans la région du Midi-Pyrénées. Dans une seconde partie, la vitesse de minéralisation de l'azote des boues a été déterminée, ainsi que son potentiel de volatilisation. Afin de conclure l'étude sur le carbone et l'azote, l'effet de la taille des particules sur la dynamique de dégradation a été évalué. [...]TOULOUSE-ENSAT-Documentation (315552324) / SudocSudocFranceF

Evolution of humic fraction in a redoxi-luvisol after application of granular sewage sludge.

Agricultural use of biosolids is a way of returning carbon and nutrients to soils and a rational disposal of sewage sludge. Its use in rural environments faces some problems related to its high water content and readily fermentable status. An alternative procedure is to heat-dry the biosolids, which result in a granular product that can be handled with the same equipment used to spread granular fertilisers. A field experiment was carried out on a redoxi-luvisol in Toulouse (France) to evaluate the effects of the application of heat-dried biosolids on the amount of soil organic carbon and on the characteristics of humic and fulvic acid fractions of soil organic matter. It also sought to compare the effects of heat-dried biosolids and inorganic fertilisers on corn growth and yield. Three treatments were established by addition of granular biosolid, inorganic fertilisers and a non-fertilised control. Maize was cropped and soil organic matter content and some humic substance characteristics were monitored during a year after biosolid application. Even though the amount of carbon added as biosolid represented 28% of initial soil carbon content, biosolid application had no relevant effects either on soil organic matter content or on soil humic substance characteristics. Humic acid composition, molecular size and structure were not affected. Biosolid carbon seems to have been readily mineralised during crop cycle, so it functioned as a nutrient source without affecting soil organic matter qualit

A comparative framework for broad-scale plot-based vegetation classification

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