Source et dynamique du transfert des sédiments en suspension et des éléments biogènes (C, N, P) dans les bassins versants anthropisés

Sources et dynamique du transfert des sédiments en suspension et des éléments biogènes (C, N, P) dans les bassins versants anthropisé

Influence of the hyporheic zone on the phosphorus dynamics of a large gravel-bed river, Garonne River, France

Phosphorus (P) concentrations in sediments and in surface and interstitial water from three gravel bars in a large river (Garonne River, southern France) were measured daily, downstream of a wastewater treatment plant for a city of 740 000 inhabitants (Toulouse). Measurements were made of vertical hydraulic gradient (VHG), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) and total phosphorus (TP) in water and of three extractable forms of phosphorus (water extractable, NaOH extractable and H2SO4 extractable) in hyporheic sediments from the gravel bars. Dissolved phosphorus was the major contributor to TP (74–79%) in both interstitial and surface waters on all sampling dates, and in most cases surface water P concentrations were significantly higher than interstitial concentrations. Hyporheic sediment TP concentrations ranged between 269 and 465 μg g -1 and were highest in fine sediment fractions. Acid-extractable P, a non-bioavailable form, represented at least 95% of sediment TP. A positive relationship was observed between VHG and TP in two of the gravel bars, with wells that were strongly downwelling having lower TP concentrations. These results suggest that in downwelling zones, hyporheic sediments can trap surface-derived dissolved P, and that much of this P becomes stored in refractory particulate forms. Bioavailable P is mainly present in dissolved form and only occupies a small fraction of total P, with particulate P comprising the majority of total P

Apportioning sources of organic matter in streambed sediments: An integrated molecular and compound-specific stable isotope approach

We present a novel application for quantitatively apportioning sources of organic matter in streambed sediments via a coupled molecular and compound-specific isotope analysis (CSIA) of long-chain leaf wax n-alkane biomarkers using a Bayesian mixing model. Leaf wax extracts of 13 plant species were collected from across two environments (aquatic and terrestrial) and four plant functional types (trees, herbaceous perennials, and C3 and C4 graminoids) from the agricultural River Wensum catchment, UK. Seven isotopic (δ13C27, δ13C29, δ13C31, δ13C27–31, δ2H27, δ2H29, and δ2H27–29) and two n-alkane ratio (average chain length (ACL), carbon preference index (CPI)) fingerprints were derived, which successfully differentiated 93% of individual plant specimens by plant functional type. The δ2H values were the strongest discriminators of plants originating from different functional groups, with trees (δ2H27–29 = − 208‰ to − 164‰) and C3 graminoids (δ2H27–29 = − 259‰ to − 221‰) providing the largest contrasts. The δ13C values provided strong discrimination between C3 (δ13C27–31 = − 37.5‰ to − 33.8‰) and C4 (δ13C27–31 = − 23.5‰ to − 23.1‰) plants, but neither δ13C nor δ2H values could uniquely differentiate aquatic and terrestrial species, emphasizing a stronger plant physiological/biochemical rather than environmental control over isotopic differences. ACL and CPI complemented isotopic discrimination, with significantly longer chain lengths recorded for trees and terrestrial plants compared with herbaceous perennials and aquatic species, respectively. Application of a comprehensive Bayesian mixing model for 18 streambed sediments collected between September 2013 and March 2014 revealed considerable temporal variability in the apportionment of organic matter sources. Median organic matter contributions ranged from 22% to 52% for trees, 29% to 50% for herbaceous perennials, 17% to 34% for C3 graminoids and 3% to 7% for C4 graminoids. The results presented here clearly demonstrate the effectiveness of an integrated molecular and stable isotope analysis for quantitatively apportioning, with uncertainty, plant-specific organic matter contributions to streambed sediments via a Bayesian mixing model approach

Раціональність як реляційність: синтетична єдність відмінностей в трансцендентальному просторі границі

У статті висвітлюються проблеми «постсучасної» раціональності, визначальною характеристикою котрої покладається іманентна пограничність. Відношення та Іншість розглядаються як визначальні предикати раціональності, які в класичній парадигмі імплікують принципи рефлексійності, конструктивності, співмірності. Корелятами означених принципів у постструктуралістській раціональності визначаються повторність (ітеративність), фрагментарність, подвоєння, розрізняння. Конгруентність класичної та постсучасної раціональності зумовлена еквівалентністю понять трансцендентальності та пограничності. Синтетична єдність (розбіжність та зв'язок) з її специфікацією принципами пов’язання та розрізняння, визначається через медіативну функцію судження, структура якого фундується параметрами реляційності.В статье освещаются проблемы «постсовременной» рациональности, определяющей характеристикой которой полагается имманентная пограничность. Отношение и Другость рассматриваются как определяющие предикаты рациональности, которые имплицируют принципы рефлексивности, конструктивности, соразмерности в классической парадигме. Коррелятами обозначенных принципов в постструктуралистской рациональности являются повторность (итеративность), фрагментарность, удвоение, различание. Конгруэнтность классической и постсоврменной рациональности обусловлена эквивалентностью понятий трансцендентальности и пограничности. Синтетическое единств (различие и связь) с его спецификацией в позициях увязывания и различания, определяется через медиативную функцию суждения, структура которого фундируется параметрами реляционности.The paper illuminates some problems of the post-contemporary rationality that possesses the immanent borderness as its distinctive feature. The Relationality and the Anotherness are investigaled as the common predicates of rationality that implicate the “classical” principles of reflexity, constructiveness, proportionality. The main principles of the poststructuralistic rationality correlating with the classical ones are recurrence (iterativity), doubleness, fragmentariness, differance. The congruence of the classical rationality and the post-contemporary one is caused by the equivalency of the concepts “transcendentality” and “borderness”. The synthetical unity (relation between deviation and connection) with its specification by the linking and the differance principles is determined by the mediative function of the assertion that is structured by the relationality parameters

The stocks and flows of nitrogen, phosphorus and potassium across a 30-year time series for agriculture in Huantai county, China

In order to improve the efficiency of nutrient use whilst also meeting projected changes in the demand for food within China, new nutrient management frameworks comprised of policy, practice and the means of delivering change are required. These frameworks should be underpinned by systemic analyses of the stocks and flows of nutrients within agricultural production. In this paper, a 30-year time series of the stocks and flows of nitrogen (N), phosphorus (P) and potassium (K) are reported for Huantai county, an exemplar area of intensive agricultural production in the North China Plain. Substance flow analyses were constructed for the major crop systems in the county across the period 1983–2014. On average across all production systems between 2010 and 2014, total annual nutrient inputs to agricultural land in Huantai county remained high at 18.1 kt N, 2.7 kt P and 7.8 kt K (696 kg N ha− 1; 104 kg P ha− 1; 300 kg K ha− 1). Whilst the application of inorganic fertiliser dominated these inputs, crop residues, atmospheric deposition and livestock manure represented significant, yet largely unrecognised, sources of nutrients, depending on the individual production system and the period of time. Whilst nutrient use efficiency (NUE) increased for N and P between 1983 and 2014, future improvements in NUE will require better alignment of nutrient inputs and crop demand. This is particularly true for high-value fruit and vegetable production, in which appropriate recognition of nutrient supply from sources such as manure and from soil reserves will be required to enhance NUE. Aligned with the structural organisation of the public agricultural extension service at county-scale in China, our analyses highlight key areas for the development of future agricultural policy and farm advice in order to rebalance the management of natural resources from a focus on production and growth towards the aims of efficiency and sustainability

La constitution d'une agglomération et d'un conseil de développement autour de la ville sont-ils des facteurs d'intégration urbaine et de cohésion sociale ?

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Origine et devenir du phosphore dans le continuum aquatique de la Seine des petits bassins amont à l'Estuaire : rôle du phosphore échangeable sur l'eutrophisation

This study estimates the phosphorus (P) budget of the Seine basin (74 000 km2). In 2000, fertilizers represent 60 % of total P inputs to agricultural soils (20-25 kgP/ha). P stocks in cultivated soils appear very high (1800-5000 kgP/ha). Losses by runoff (0.18-0.59 kgP/ha) and by drainage (0.12 kgP/ha) contribute to 40-50 % of P inputs in upstream agricultural basins and 20 % for the entire basin. P content in suspended sediments (SS) increases 1 to 4 times from headwaters to the fluvial outlet. We use the 32P isotopic method to estimate the P exchangeability. The mathematical formulation of P ion transfer between SS and water is inserted into the Riverstrahler model and tested in the most eutrophicated sub-basin. 8000 tP (44 % as particulate P) are delivered to the Seine estuary. P content in SS decreases 2 times from the entry of the estuary to the mouth. Finally, we establish a mathematical formulation for the transfer of P between SS and water in the turbidity maximum of the estuary.Ce travail établit les bilans de phosphore (P) à l’échelle du bassin de la Seine (74 000 km2). En 2000, les engrais représentent 60 % des apports aux sols agricoles (20-25 kgP/ha). Les stocks y apparaissent énormes (1800-5000 kgP/ha). Les pertes par érosion (0.18-0.59 kgP/ha) et par drainage (0.12 kgP/ha), contribuent pour 40-50 % des apports de P dans les bassins agricoles amont et 20 % sur l’ensemble du bassin. Les matières en suspension (MES) s’enrichissent en P d’un facteur 4 entre l’amont et l’aval. La forte réactivité du P y est mis en évidence par une méthode isotopique au 32P. Le transfert des ions P entre les MES et l’eau, mis en équation et introduit dans le modèle Riverstrahler, est testé sur le sous-bassin le plus eutrophisé. 8 000 tP (44 % particulaire) sont apportées à l’estuaire. Les MES s’appauvrissent d’un facteur 2 entre l’entrée et la sortie de l’estuaire. Dans le bouchon vaseux, une équation du transfert des ions P entre les MES et l’eau est également formulée

Origine et devenir du phosphore dans le continuum aquatique de la Seine des petits bassins amont à l'Estuaire : rôle du phosphore échangeable sur l'eutrophisation

This study estimates the phosphorus (P) budget of the Seine basin (74 000 km2). In 2000, fertilizers represent 60 % of total P inputs to agricultural soils (20-25 kgP/ha). P stocks in cultivated soils appear very high (1800-5000 kgP/ha). Losses by runoff (0.18-0.59 kgP/ha) and by drainage (0.12 kgP/ha) contribute to 40-50 % of P inputs in upstream agricultural basins and 20 % for the entire basin. P content in suspended sediments (SS) increases 1 to 4 times from headwaters to the fluvial outlet. We use the 32P isotopic method to estimate the P exchangeability. The mathematical formulation of P ion transfer between SS and water is inserted into the Riverstrahler model and tested in the most eutrophicated sub-basin. 8000 tP (44 % as particulate P) are delivered to the Seine estuary. P content in SS decreases 2 times from the entry of the estuary to the mouth. Finally, we establish a mathematical formulation for the transfer of P between SS and water in the turbidity maximum of the estuary.Ce travail établit les bilans de phosphore (P) à l’échelle du bassin de la Seine (74 000 km2). En 2000, les engrais représentent 60 % des apports aux sols agricoles (20-25 kgP/ha). Les stocks y apparaissent énormes (1800-5000 kgP/ha). Les pertes par érosion (0.18-0.59 kgP/ha) et par drainage (0.12 kgP/ha), contribuent pour 40-50 % des apports de P dans les bassins agricoles amont et 20 % sur l’ensemble du bassin. Les matières en suspension (MES) s’enrichissent en P d’un facteur 4 entre l’amont et l’aval. La forte réactivité du P y est mis en évidence par une méthode isotopique au 32P. Le transfert des ions P entre les MES et l’eau, mis en équation et introduit dans le modèle Riverstrahler, est testé sur le sous-bassin le plus eutrophisé. 8 000 tP (44 % particulaire) sont apportées à l’estuaire. Les MES s’appauvrissent d’un facteur 2 entre l’entrée et la sortie de l’estuaire. Dans le bouchon vaseux, une équation du transfert des ions P entre les MES et l’eau est également formulée