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371.
Acetylene, dimethyl ether (DME) and 2-chloro-6-trichloromethyl pyridine (nitrapyrin) were used as inhibitors to study the
contributions of nitrification and denitrification to the production of N2O and nitric oxide (NO) in samples taken from the soil profile of a peatland drained for forestry. Acetylene and DME inhibited
60–100% of the nitrification activity in field-moist samples from the 0–5 cm and 5–10 cm peat layers, whereas nitrapyrin had
no inhibitory effect. In the 0–5 cm peat layer the N2O production could be reduced by up to 90% with inhibitors of nitrification, but in the 5–10 cm peat layer this proportion
was 20–30%. All the inhibitors removed 96–100% of the nitrification potential in peat-water slurries from the 0–5 cm peat
layer, but the 5–10 cm layer had a much lower nitrification activity, and here the efficiency of the inhibitors was more variable.
Litter was the main net source of NO in the peat profile. NO3
– production was lower in the litter layer than in the peat, whereas N2O production was much higher in the litter than in the peat. Denitrification was the most probable source of N2O and NO in the litter, which had a high availability of organic substrates.
Received: 14 July 1997 相似文献
372.
Osnan Lennon Lameira Silva Antnia Rafaela Gonalves Macedo Emília do Socorro Conceio de Lima Nunes Keila Diniz Campos Leiliane Cristina Cardoso Araújo Xenna Tiburo Anne Suellen Oliveira Pinto Maria Regina Sarkis Peixoto Joele Micheli da Silva Ferreira Ana Carolina Ramos da Silva Renata Santana Lorenzo Raices Adriano Gomes da Cruz Leandro Juen Rossineide Martins da Rocha 《Aquaculture Research》2020,51(6):2336-2348
The objective of this study was to evaluate the effect of environmental factors on the fatty acid profiles and physicochemical composition of Crassostrea gasar cultured in two locations with differences in salinity and precipitation gradients. The study period was divided into four seasonal divisions—the rainy–dry transition period, the dry season, dry–rainy transition and the rainy season. The salinity, pH and temperature were measured at each site during specimen collection. A total of 712 oyster samples were used for fatty acid profiling and physicochemical analysis. Salinity and precipitation were the environmental parameters that influenced the fatty acid profile and physicochemical characteristics of oysters. C. gasar exhibited excellent values of n3 polyunsaturated fatty acids (DHA, EPA and eicosatrienoic), with a predominance of these acids during periods of higher precipitation. Variations in precipitation and salinity resulted in significant differences in oyster nutritional characteristics. Oysters grown in Amazonian estuaries can be considered nutritious throughout the year, with better conditions during the rainy season. 相似文献
373.
A comparison between water exchange and settling tank as a method for suspended solids management in intensive biofloc technology systems: effects on shrimp (Litopenaeus vannamei) performance,water quality and water use 下载免费PDF全文
Rafael Arantes Rodrigo Schveitzer Caio Magnotti Katt Regina Lapa Luis Vinatea 《Aquaculture Research》2017,48(4):1478-1490
Biofloc systems rely on microbial processes in the water column to recycle animal waste products, reducing the need for water exchange. These increases biofloc concentration in the water and some form of removal is needed. An experiment was carried out to evaluate two management practices to control biofloc in Litopenaeus vannamei culture. Six tanks (48 m3) were divided into two treatments: water exchange and solid settler. Shrimp were stocked at 164 shrimp m?2 and with 0.67 g of weight. After 61 days, shrimp under solid settler treatment demonstrated mean weight of 12.7 ± 0.5 g with survival of 73.8 ± 1.4%, and those under water exchange had a final weight of 10.1 ± 0.2 g and survival rate of 57.8 ± 11.1%. Total suspended solids did not differ between the treatments: 326.8 ± 24.9 mg L?1 for water exchange and 310.9 ± 25.3 mg L?1 for solid settlers. Settleable solids and productivity/respiration ratio was higher (P < 0.05) in water exchange treatment, indicating differences in physical and biological characteristics of bioflocs. Solids removal method influenced the water use, in which 1150 ± 249 L of water was necessary to produce one kilogram of shrimp using water exchange strategy, and 631 ± 25 L kg?1 with the use of settlers. Our results indicate that continuous operation of settlers can reduce variability in solids characteristics and water quality variables such as ammonia. Both strategies are efficient in controlling biofloc concentrations of the water; however, settlers can reduce water use and improve shrimp production. 相似文献
374.
375.
Keihan Mani Lindborg Christian Trgrdh Ann-Charlotte Eliasson Petr Dejmek 《Cereal Chemistry》1997,74(1):49-55
The shear viscosity of three doughs of different wheat cultivars mixed to a farinograph level of 500 BU was measured at low shear rates as a function of the shear deformation using a cone-and-plate viscometer. Cyanoacrylate adhesive was used to attach the dough samples to the instrument surfaces to eliminate wall slip. Flours used were Dragon, Kosack, and a fodder wheat. A distinct difference was observed between the viscosities of the different flour cultivars. The strongest dough (Dragon), with the highest protein content and a good resistance in the farinograph, had the highest maximum viscosity. The doughs showed distinct strain hardening, more pronounced for the strong doughs. Maximum viscosity was obtained at a strain of ≈4, almost independent of the shear rate, but at higher values for stronger doughs (5 for Dragon, 4 for Kosack, and 3.5 for fodder wheat). The maximum was most pronounced for well-mixed doughs after resting. The viscosity and its variation with strain may be used as a measure of quality; a higher viscosity and a maximum occurring at high strains indicating good quality (related to the farinogram). The viscosity gradually decreased at higher strains. Apparent viscosity increases with strain and reaches a maximum value at a common strain, which suggests the presence of entangled molecules. The increase of maximum viscosity with increase in mixing also supports this theory. Resting the dough increases the maximum viscosity, which suggests the formation of new cross-links in the nonequilibrium entangled network during resting. 相似文献