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991.
Phosphorus flows and use efficiencies in production and consumption of wheat, rice, and maize in China 总被引:5,自引:0,他引:5
Increasing fertilizer phosphorus (P) application in agriculture has greatly contributed to the increase of crop yields during the last decades in China but it has also increased P flows in food production and consumption. The relationship between P use efficiency and P flow is not well quantified at national level. In present paper we report on P flows and P use efficiencies in rice, wheat, and maize production in China using the NUFER model. Conservation strategies for P utilization and the impact of these strategies on P use efficiency have been evaluated. Total amounts of P input to wheat, rice, and maize fields were 1095, 1240, and 1128 Gg, respectively, in China, approximately 80% of which was in chemical fertilizers. The accumulation of P annually in the fields of wheat, rice, and maize was 29.4, 13.6, and 21.3 kg ha−1, respectively. Phosphorus recovered in the food products of wheat, rice, and maize accounted for only 12.5%, 13.5%, and 3.8% of the total P input, or 3.2%, 2.6%, and 0.9% of the applied fertilizer P, respectively. The present study shows that optimizing phosphorus flows and decreasing phosphorus losses in crop production and utilization through improved nutrient management must be considered as an important issue in the development of agriculture in China. 相似文献
992.
Short and long term dispersion patterns of radionuclides in the atmosphere around the Fukushima Nuclear Power Plant 总被引:1,自引:0,他引:1
The Chernobyl accident and unfortunately the recent accident at the Fukushima 1 Nuclear Power Plant are the most serious accidents in the history of the nuclear technology and industry. Both of them have a huge and prolonged impact on environment as well as human health. Therefore, any technological developments and strategies that could diminish the consequences of such unfortunate events are undisputedly the most important issues of research. Numerical simulations of dispersion of radionuclides in the atmosphere after an accidental release can provide with a reliable prediction of the path of the plume. In this study we present a short (one month) and a long (11 years) term statistical study for the Fukushima 1 Nuclear Power Plant to estimate the most probable dispersion directions and plume structures of radionuclides on local scale using a Gaussian dispersion model. We analyzed the differences in plume directions and structures in case of typical weather/circulation pattern and provided a statistical-climatological method for a “first-guess” approximation of the dispersion of toxic substances. The results and the described method can support and used by decision makers in such important cases like the Fukushima accident. 相似文献
993.
Climatic drivers of potential hazards in Mediterranean coasts 总被引:1,自引:1,他引:0
Agustín Sánchez-Arcilla Cesar Mösso Joan Pau Sierra Marc Mestres Ali Harzallah Mohamed Senouci Mohamed El Raey 《Regional Environmental Change》2011,11(3):617-636
This paper studies climatic drivers (air and water temperature, precipitation rates, river discharge, sea level and storm
patterns) in four Mediterranean regions: the Catalan-Valencia Coast (Spain), the Oran (Algeria) and Gabès (Tunisia) Gulfs
and the western Nile Delta (Egypt). The paper also considers the potential hazards that these drivers can induce. It first
analyses climatic trends in the drivers, taking into account the available time series of recorded and simulated meteo-oceanographic
data from different sources. Next, it presents the general framework to assess biogeophysical hazards (flooding, erosion,
droughts and water quality), followed by a simple and yet robust evaluation of those hazards for the four studied coastal
sites. Assuming climate change projections under different scenarios and considering the observed trends in drivers, the resulting
erosion rates due to sea-level rise and wave storm effects have been estimated. The Nile and Ebro Deltas, together with the
Oran Gulf, are more vulnerable than the Gulfs of Valencia and Gabès. Regarding water quality in terms of (a) precipitation
and dissolved oxygen in the water column and (b) sea surface temperature, the results show that the most vulnerable zones
for the projected conditions (a) are the Gulfs of Oran, Valencia and Gabès, while the Nile Delta is the region where the decrease
in water quality will be less pronounced. For the projected conditions (b), the most vulnerable zone is the Ebro Delta, while
the impact in the other three cases will be smaller and of comparable magnitude. Finally, the overall future impact of these
hazards (associated to climatic change) in the four sites is discussed in comparative terms, deriving some conclusions. 相似文献
994.
Liquid-chromatography interfaced with time-of-flight mass spectrometry (LC-TOF/MS) was used to separate and characterize the transformation products arising from TiO2-photocatalytic degradation of the fungicide Fenhexamid (FEX) in aqueous solution under simulated solar irradiation. Prior to identification, irradiated solutions of FEX (10 mg L−1) were concentrated by solid-phase extraction. Assignments of the mass spectra ions were aided by elemental composition calculations, comparison of structural analogues and available literature, and acquired knowledge regarding mass spectrometry of related heterocyclic compounds. The primary transformation intermediates identified were hydroxyl and/or keto-derivatives. Several positional isomers are typically produced as a consequence of the non-selectivity of the OH radical attack. Moreover, products resulted from the cleavage of the amide and NHdichlorophenol bonds were formed. Finally, cyclic - benzo[d]oxazole intermediates are also formed through an intramolecular photocyclization process and cleavage of halogen - carbon bond. In the case of the hydroxy and/or keto-derivatives, the generic fragmentation scheme obtained from the interpretation of the ESI-TOF-MS data cannot be diagnostic to precisely localize the position of the entering substituent on the FEX molecule, and thus to characterize all its possible oxygenated derivatives by assigning a plausible structure with confidence. On the basis of identified products different pathways of photocatalytic degradation of FEX were proposed and discussed. 相似文献
995.
Kukutschová J Moravec P Tomášek V Matějka V Smolík J Schwarz J Seidlerová J Safářová K Filip P 《Environmental pollution (Barking, Essex : 1987)》2011,159(4):998-1006
The paper addresses the wear particles released from commercially available “low-metallic” automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 μm were released into the air. The numbers of nanoparticles (<100 nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300 °C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles. 相似文献
996.
In Portuguese waters, thornback ray Raja clavata spawns mainly between May and January, although females and males in spawning condition are found throughout the year. The
maturation process can be divided into three main phases by using information on gonad weight, oviducal gland and uterus width
in females and on gonad weight, clasper length and sperm duct width in males. Females attain length-at-first-maturity at 784 mm
and males at 676 mm, at ages of 7.5 and 5.8 years, respectively. In females larger than length-at-first-maturity, a resting
stage was identified characterized by low gonadosomatic index and well-developed oviducal glands and uteri. These results
along with the low proportion of adult females that are effectively reproducing per month demonstrated that the thornback
ray cannot be considered a continuous spawner as described in other studies. Fecundity was determinate with about 35 eggs
released per batch. During the spawning season, a total of four batch episodes occur indicating that the total fecundity was
approximately 136 eggs per female. Regional differences may exist in the reproductive strategy of the species, namely on the
duration of the spawning season, length-at-first-maturity, and fecundity, which can be related to a more intense fishing pressure
in northern European waters. 相似文献
997.
Teresa Rocha-Santos Filipe Ferreira Lurdes Silva Ana Cristina Freitas Ruth Pereira Mário Diniz Luísa Castro Isabel Peres Armando Costa Duarte 《Environmental science and pollution research international》2010,17(4):866-874
Background, aim and scope
Pulp and paper mills generate a plethora of pollutants depending upon the type of pulping process. Efforts to mitigate the environmental impact of such effluents have been made by developing more effective biological treatment systems in terms of biochemical oxygen demand, chemical oxygen demand, colour and lignin content. This study is the first that reports an evaluation of the effects of a tertiary treatment by fungi (Pleurotus sajor caju, Trametes versicolor and Phanerochaete chrysosporium and Rhizopus oryzae) on individual organic compounds of a Eucalyptus globulus bleached kraft pulp and paper mill final effluent after secondary treatment (final effluent). 相似文献998.
Concentrations and sources of Dechlorane Plus in sewage sludge 总被引:1,自引:0,他引:1
Sewage sludge from 31 urban Spanish wastewater treatment plants (WWTP) was analyzed for the emerging halogenated flame retardant Dechlorane Plus (DP). Concentrations of the two major isomers in the technical mixture, syn and anti, ranged between 0.903-19.2 and 1.55-75.1 ng g−1 dry weight, respectively. Overall, concentrations of DP were lower than those of polybrominated diphenyl ethers (PBDEs) (9.10-995 ng g−1 dry weight) and this is likely related to the higher usage of brominated flame retardants. The average ratio of the syn isomer to total DP (fsyn) was 0.28 ± 0.05, which is similar to that of the commercial mixture. Comparing different wastewater treatment methods, we found lower concentrations in those using biological nitrogen and phosphorous elimination, suggesting that DP is susceptible to microbial degradation and that anti-DP is more so, given the enrichment of syn-DP in the sewage sludge. Principal components analysis revealed significant positive correlation (r = 0.619, p < 0.05) between total DP concentrations with the contribution of industrial input to waste streams. This implies release of DP is related to industrial activity, likely stemming from the use of the technical product during manufacture of consumer goods. However, use and disposal of products containing DP could not be dismissed. According to our knowledge, this is the first report on DP in WWTP sludge. 相似文献
999.
Arsenic (As) and mercury (Hg) are among the most toxic metals/metalloids. The overall goal of this study was to investigate the bioaccumulation of these trace elements in Vallisneria neotropicalis, a key trophic species in aquatic environments. For this purpose, As and Hg concentrations were determined in sediments and natural populations of V. neotropicalis in sub-estuaries of Mobile Bay (Alabama, USA), differing with respect to past and present anthropogenic impact. Analyses indicate that the Fish River is the most contaminated among the sub-estuaries investigated; levels of As found in Fish River sediments fall within a range that could potentially cause adverse effects in biota. Sediment As concentrations were only moderately correlated with those in V. neotropicalis; no correlation was found between sediment and plant Hg levels. However, several parameters could have masked such potential relationships (e.g., differences in sediment characteristics and “biological dilution” phenomena). Results presented herein highlight the numerous parameters that can influence metal/metalloids accumulation in aquatic plants as well as species-specific responses to trace element contamination. Finally, this study underscores the need for further investigation into contaminant bioaccumulation in ecologically and economically important coastal environments. 相似文献
1000.
It is well established that an optimal aerobic and anaerobic microbial metabolism is achieved with a C/N ratio between 20 and 30. Most studies are currently based on chemically-measured carbon and nitrogen contents. However, some organic wastes can be composed of recalcitrant carbon fractions that are not bioavailable. To know the biodegradable C/N ratio, two different methods to determine the aerobic and anaerobic biodegradable organic carbon (BOCAE and BOCAN) are proposed and used to analyze a wide variety of different organic samples. In general, raw wastes and digested products have more amount of BOCAE. On the contrast, the samples collected after an aerobic treatment have higher content of BOCAN. In any case, all the BOC fractions are lower than the total organic carbon (TOC). Therefore, the C/N ratios based on BOC are always lower than the total C/N ratio based on the TOC measure. The knowledge of the real bioavailable C/N ratio is crucial for the biological treatments of organic materials. To reduce the test time necessary for BOC determination, the values of BOC for all the samples obtained at different times were compared and correlated with the final BOC. A method that allows for the determination of BOCAE in 4 d is proposed. In relation to the anaerobic assay, the biogas potential calculated after 21 and 50 d was positively correlated with the final potential defined after 100 d of assay. 相似文献