Nitrate contamination in groundwater originates mainly from excessive use of fertilizers and uncontrolled discharge to land of incompletely-treated wastewater associated with agricultural activities. A systematic field investigation was carried out in a sub-catchment of Dianchi Lake, Kunming, Yunnan, China, into the hydrological, biological and geological processes of nitrogen transport and transformation in the aeration zone and aquifer system. In situ experiments showed that the quantity of NO 3 -N recharged into groundwater was related to fertilization. Nitrification and denitrification behaved quite differently but were affected by moisture content and Eh value. The vertical infiltration rate was controlled by the groundwater table and hydraulic conductivity of the soil. The existence of a zero-flux plane reflected the dynamics of water fluxes in the soil profile and Eh was measured in the aeration zone. In response to these factors, the nitrification rate was greatest in the top soil and reduced with the depth of soil; it was 6.53 mg/(kg·h) in the vegetated plot and 0.2-0.3 mg/(kg·h) in the unvegetated one. The denitrification rate in the unvegetated plot was 6.36 mg/(kg·h), and it was 2.79 mg/(kg·h) in the vegetated one.Key words nitrogen; groundwater; nitrate; nitrification; denitrification Processus bio-géologiques du transport et de la transformation de l'azote en zone non saturée et au sein de l'aquifère Résumé La contamination des eaux souterraines par les nitrates provient essentiellement d'une utilisation excessive de fertilisants et d'un rejet incontrôlé vers le milieu d'eaux usées incomplètement traitées en lien avec les activités agricoles. Une étude de terrain systématique a été menée dans un sous-bassin du bassin versant du Lac Dianchi, Kunming, Yunnan, en Chine, afin de comprendre les processus hydrologiques, biologiques et géologiques déterminants dans le transport et la transformation de l'azote dans la zone non saturée et dans le système aquifère. Des expériences in situ ont montré que la quantité de NO 3 -N apportée par recharge des eaux souterraines est liée à la fertilisation. La nitrification et la dénitrification se comportent très différemment mais sont liées à la teneur en eau et à la valeur de Eh. Le taux d'infiltration verticale est contrôlé par le niveau de la nappe et par la conductivité hydraulique du sol. L'existence d'un plan de flux nul reflète la dynamique des flux hydriques dans le profil de sol et la distribution de Eh dans la zone non saturée, au niveau des sites de mesure. En réponse à ces facteurs, le taux de nitrification est plus fort dans les horizons superficiels et diminue avec la profondeur dans le sol; il s'élève à 6.53 mg/(kg·h) dans la zone végétalisée et à 0.2-0.3 mg/(kg·h) dans la zone non végétalisée. Le taux de dénitrification dans la zone non végétalisée s'élève à 6.36 mg/(kg·h), et à 2.79 mg/(kg·h) dans la zone végétalisée.
see paper for full list of authorsInternational audienceThe results of R&D of radiopure zinc molybdate (ZnMoO4) based scintillating bolometers for the LUMINEU (Luminescent Underground Molybdenum Investigation for NEUtrino mass and nature) double-beta decay experiment are presented. A dedicated two-stage molybdenum purification technique (sublimation in vacuum and recrystallization from aqueous solutions) and an advanced directional solidification method (the low-thermal-gradient Czochralski technique) were utilized to produce high optical quality large mass (∼1 kg) ZnMoO4 crystal boules and first 100 Mo (99.5%) enriched Zn 100MoO4 crystal scintillator (mass of ∼0.2 kg). Scintillating bolometers based on ZnMoO4 (≈ 0.33 kg) and Zn 100MoO4 (≈ 0.06 kg) scintillation elements and high purity Ge wafers were tested in the EDELWEISS set-up at the Modane Underground Laboratory (France). Long term low temperature tests demonstrate excellent detectors’ performance and effectiveness of the purification and solidification procedures for the achievement of high radiopurity of the material, in particular with a bulk activity of 228Th and 226Ra below 4 µBq/kg. The adopted protocol was used to produce for the first time a large volume Zn 100MoO4 crystal scintillator (mass of ∼1.4 kg, 100 Mo enrichment is 99.5%) to search for neutrinoless double-beta decay of 100 Mo in the framework of the LUMINEU project
Plain low carbon steel produced by compact strip production (CSP) process was analyzed using TEM, EELS and XEDS. Nano-sized oxides and sulfides were observed in the steel. The nano-oxides are mainly ferrospinel of <20nm in size, and the nano-sulfides are MnS and FeS particles with size of 20-100 nm. They distributed both in grains and at grain boundaries. These nano precipitates could form in cast slab before heavy deformation by rolling process. It is proposed that besides the grain refinement, the nano-pricipitation plays an important role in yield strength enhancement. This mechanism may provide a new approach to strengthen plain low carbon steels.
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