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921.
Giovanni Galietta Eduardo Egaña Fernando Gemelli Diego Maeso Noelia Casco Paula Conde 《Journal of environmental science and health. Part. B》2013,48(1):35-40
Dissipation curves of azoxystrobin and of the neonicotinoids acetamiprid and thiacloprid in peach; azinphos-methyl and carbaryl in pear and azoxystrobin, chlorfenapyr and chlorpyrifos in high-tunnel tomato crops were studied in the Southern region of Uruguay. An analytical methodology based on solid phase extraction (SPE) and detection by High Performance Liquid Chromatography with Diode Array Detector (HPLC/DAD) was used for acetamiprid and thiacloprid. Coupled SPE and detection by Gas Chromatography with Mass Selective Detector (GC/MSD) was used for the detection of azinphos-methyl, azoxystrobin, carbaryl, chlorfenapyr and chlorpyrifos residues. Curves were modeled mathematically with Solver program of Microsoft Excel®. The best fit for acetamiprid and thiacloprid in peach was achieved with the exponential model (r2=0.961 and 0.944, respectively). In the case of peach fruits there is not a Maximum Residue Limit (MRL) for acetamiprid in the Codex Alimentarius, while 0.5 mg/kg is the value rated for thiacloprid. The MRLs accepted by the European Union (EU) are 0.1 mg/kg for acetamiprid and 0.3 mg/kg for thiacloprid. According to the curves determined in these experiments, thiacloprid residues 10 to 12 days after application (daa) were below the MRLs established by both sources. In the case of acetamiprid, 25 daa would be required, according to the exponential mathematical model, to get residues levels below the MRL values established by the EU. For azinphos methyl in pear, the residues detected were mathematically fitted to an exponential model (r2=0.999). According to it, residue levels under the MRL established by the EU (0.05 mg/kg) are gotten in our conditions in 20 daa. In plastic tunnel tomato chlorfenapyr residues were not detected from 16 daa, having the dissipation curve an exponential trend. In the same condition, there was not a decay of the azoxystrobin concentration during a 24-day trial, being it around 0.40 ± 0.05 mg/kg. 相似文献
922.
923.
Primary production in the eutrophic Baltic Sea is limited by nitrogen availability; hence denitrification (natural transformation
of nitrate to gaseous N2) in the sediments is crucial in mitigating the effects of eutrophication. This study shows that dissimilatory nitrate reduction
to ammonium (DNRA) process, where nitrogen is not removed but instead recycled in the system, dominates nitrate reduction
in low oxygen conditions (O2 <110 μM), which have been persistent in the central Gulf of Finland during the past decade. The nitrogen removal rates measured
in this study show that nitrogen removal has decreased in the Gulf of Finland compared to rates measured in mid-1990s and
the decrease is most likely caused by the increased bottom water hypoxia. 相似文献
924.
Interacting forces of climate change and globalization are transforming the Arctic. Triggered by a non-linear shift in sea
ice, this transformation has unleashed mounting interest in opportunities to exploit the region’s natural resources as well
as growing concern about environmental, economic, and political issues associated with such efforts. This article addresses
the implications of this transformation for governance, identifies limitations of existing arrangements, and explores changes
needed to meet new demands. It advocates the development of an Arctic regime complex featuring flexibility across issues and
adaptability over time along with an enhanced role for the Arctic Council both in conducting policy-relevant assessments and
in promoting synergy in interactions among the elements of the emerging Arctic regime complex. The emphasis throughout is
on maximizing the fit between the socioecological features of the Arctic and the character of the governance arrangements
needed to steer the Arctic toward a sustainable future. 相似文献
925.
926.
Global climate issues and a looming energy crisis put agriculture under pressure in Sub-Saharan Africa. Climate adaptation measures must entail sustainable development benefits, and growing crops for food as well as energy may be a solution, removing people from hunger and poverty without compromising the environment. The present study investigated the feasibility of using non-food parts of cassava for energy production and the promising results revealed that at least 28% of peels and stems comprise dry matter, and 10 g feedstock yields >8.5 g sugar, which in turn produced >60% ethanol, with pH ≈ 2.85, 74-84% light transmittance and a conductivity of 368 mV, indicating a potential use of cassava feedstock for ethanol production. Thus, harnessing cassava for food as well as ethanol production is deemed feasible. Such a system would, however, require supportive policies to acquire a balance between food security and fuel. 相似文献
927.
Yutaka Tamaura 《Ambio》2012,41(2):108-111
When a concentrated solar beam is irradiated to the ceramics such as Ni-ferrite, the high-energy flux in the range of 1500–2500 kW/m2 is absorbed by an excess Frenkel defect formation. This non-equilibrium state defect is generated not by heating at a low heating-rate (30 K/min), but by irradiating high flux energy of concentrated solar beam rapidly at a high heating rate (200 K/min). The defect can be spontaneously converted to chemical energy of a cation-excess spinel structure (reduced-oxide form) at the temperature around 1773 K. Thus, the O2 releasing reaction (α-O2 releasing reaction) proceeds in two-steps; (1) high flux energy of concentrated solar beam absorption by formation of the non-equilibrium Frenkel defect and (2) the O2 gas formation from the O2? in the Frenkel defect even in air atmosphere. The 2nd step proceeds without the solar radiation. We may say that the 1st step is light reaction, and 2nd step, dark reaction, just like in photosynthesis process. 相似文献
928.
The photovoltaic conversion efficiency for near-infrared (NIR) sunlight is improved successfully by dye sensitization of bulk heterojunction polymer solar cells, in which the active layer was prepared by a ternary blend of poly(3-hexylthiophene), a fullerene derivative (1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene), and an NIR dye, silicon phthalocyanine bis(trihexylsilyl oxide). The mechanism of the NIR-dye sensitization is studied by femtosecond transient absorption spectroscopy. 相似文献
929.
Torben R. Christensen Marcin Jackowicz-Korczyński Mika Aurela Patrick Crill Michal Heliasz Mikhail Mastepanov Thomas Friborg 《Ambio》2012,41(3):207-217
This article reports a dataset on 8 years of monitoring carbon fluxes in a subarctic palsa mire based on micrometeorological eddy covariance measurements. The mire is a complex with wet minerotrophic areas and elevated dry palsa as well as intermediate sub-ecosystems. The measurements document primarily the emission originating from the wet parts of the mire dominated by a rather homogenous cover of Eriophorum angustifolium. The CO2/CH4 flux measurements performed during the years 2001–2008 showed that the areas represented in the measurements were a relatively stable sink of carbon with an average annual rate of uptake amounting to on average ?46 g C m?2 y?1 including an equally stable loss through CH4 emissions (18–22 g CH4–C m?2 y?1). This consistent carbon sink combined with substantial CH4 emissions is most likely what is to be expected as the permafrost under palsa mires degrades in response to climate warming. 相似文献
930.
Bacterial community profiles from sediments of the Anacostia River using metabolic and molecular analyses 总被引:1,自引:0,他引:1
Bushaw-Newton KL Ewers EC Velinsky DJ Ashley JT Macavoy SE 《Environmental science and pollution research international》2012,19(4):1271-1279