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141.
Luis Lassaletta Eduardo Aguilera Alberto Sanz-Cobena Guillermo Pardo Gilles Billen Josette Garnier Bruna Grizzetti 《Mitigation and Adaptation Strategies for Global Change》2016,21(7):975-994
In this paper we examine the trends of nitrous oxide (N2O) emissions of the Spanish agricultural sector related to national production and consumption in the 1961–2009 period. The comparison between production- and consumption-based emissions at the national level provides a complete overview of the actual impact resulting from the dietary choices of a given country and allows the evaluation of potential emission leakages. On average, 1.5 % of the new reactive nitrogen that enters Spain every year is emitted as N2O. Production- and consumption-based emissions have both significantly increased in the period studied and nowadays consumption-based emissions are 45 % higher than production-based emissions. A large proportion of the net N2O emissions associated with imported agricultural goods comes from countries that are not committers for the United Nations Framework Convention on Climate Change Kyoto Protocol Annex I. An increase in feed consumption is the main driver of the changes observed, leading to a remarkable emission leakage in the Spanish agricultural sector. The complementary approach used here is essential to achieve an effective mitigation of Spanish greenhouse gas emissions. 相似文献
142.
143.
When reproduction competes with the amount of resources available for survival during an unpredictable nonbreeding season, individuals should adopt a risk-sensitive regulation of their reproductive allocation. We tested this hypothesis on female reindeer (Rangifer tarandus), which face a trade-off between reproduction and acquisition of body reserves during spring and summer, with autumn body mass functioning as insurance against stochastic winter climatic severity. The study was conducted in a population consisting of two herds: one that received supplementary winter feeding for four years while the other utilized natural pastures. The females receiving additional forage allocated more to their calves. Experimental translocation of females between the herds was conducted to simulate two contrasting rapid alterations of winter conditions. When females receiving supplementary feeding were moved to natural pastures, they promptly reduced their reproductive allocation the following summer. However, when winter conditions were improved, females were reluctant to increase their reproductive allocation. This asymmetric response to improved vs. reduced winter conditions is consistent with a risk-averse adjustment in reproductive allocation. The ability of individuals to track their environment and the concordant risk-sensitive adjustment of reproductive allocation may render subarctic reindeer more resilient to climate change than previously supposed. 相似文献
144.
The sorption of Cd and Pb by extracellular polymeric substances (EPS) extracted from activated sludges originated from wastewater treatment plants (WWTPs) or Lab-scale bioreactors was investigated as a function of pH. The study was carried out using a polarographic method in the SMDE (stripping mercury dropping electrode) mode which is suited to determine labile metals in solution containing soluble ligands such as EPS. The results obtained provide evidence of the presence of a pH-sorption/desorption edge for Cd and Pb by EPS. The use of Kurbatov’s model gives information on the mechanisms involved through the determination of “relative complexation constants” (operationally defined) and the number of protons exchanged. The use of this model demonstrates that proton exchange with metals is not the only mechanism involved in metal biosorption by EPS. Other mechanisms such as cation exchange with Ca or Mg, global electric field surrounding the ligand or micro-precipitation of metals could be involved in metal sorption by EPS. The position of the pH-sorption edge curves and the “relative complexation constants” show that Pb displays a greater affinity for EPS than Cd. The studied EPS have large differences regarding binding strength of Cd and Pb. These differences are not correlated with the organic parameters measured to characterize the EPS, however the mineral fraction of the EPS could be involved to a large extent in the sorption of metal. 相似文献
145.
Basic principles and ecological consequences of changing water regimes on nitrogen cycling in fluvial systems 总被引:8,自引:0,他引:8
Understanding the environmental consequences of changing water regimes is a daunting challenge for both resource managers
and ecologists. Balancing human demands for fresh water with the needs of the environment for water in appropriate amounts
and at the appropriate times are shaping the ways by which this natural resource will be used in the future. Based on past
decisions that have rendered many freshwater resources unsuitable for use, we argue that river systems have a fundamental
need for appropriate amounts and timing of water to maintain their biophysical integrity. Biophysical integrity is fundamental
for the formulation of future sustainable management strategies. This article addresses three basic ecological principles
driving the biogeochemical cycle of nitrogen in river systems. These are (1) how the mode of nitrogen delivery affects river
ecosystem functioning, (2) how increasing contact between water and soil or sediment increases nitrogen retention and processing,
and (3) the role of floods and droughts as important natural events that strongly influence pathways of nitrogen cycling in
fluvial systems. New challenges related to the cumulative impact of water regime change, the scale of appraisal of these impacts,
and the determination of the impacts due to natural and human changes are discussed. It is suggested that cost of long-term
and long-distance cumulative impacts of hydrological changes should be evaluated against short-term economic benefits to determine
the real environmental costs. 相似文献
146.
Using knowledge-based computational structure-activity relationship models, it is hypothesized that the aurone responsible
for the uniquely red nectar of several Mauritian bird-pollinated plants functions as a repellant of nectar-robbing or herbivorous
mammalian species.
Received: 30 November 1998 / Accepted: 18 March 1999 相似文献
147.
148.
Enzymatic hydrolysis was used to determine some binding locations of cadmium on the cell wall of a sensitive marine pseudomonad. Metal was mainly bound to ionic material such as polygalacturonic acids, and to a lesser extent, to non ionic polymers such as cellulose and dextrans. 相似文献
149.
Workers never mate in the large majority of ants, and they have usually lost the spermatheca, an organ specialized for long-term
storage of sperm. Such ‘non-sexual’ workers are restricted to laying unfertilized eggs that give rise to males, and they cannot
compete with the queens for the production of female offspring. In sharp contrast, workers in 200–300 species from phylogenetically
basal subfamilies can reproduce sexually (‘gamergates’) because they retain a functional spermatheca like the queens. Importantly,
‘non-sexual’ workers in closely related species have a vestigial spermatheca. In this study, we compared the reservoir epithelium
of ‘sexual’ workers to that of congeneric queens and ‘non-sexual’ workers using 21 species of Amblyoponinae, Ponerinae and
Ectatomminae. We show that a pronounced thickening of the epithelium near the opening of the sperm duct is strictly associated
with sexual reproduction in both castes. This is unlike ‘non-sexual’ workers in which this epithelium is always very thin,
with few organelles; but all other structures remain intact. We discuss this evolutionary degeneration of the spermatheca
and how it relates to behavioural or physiological modifications linked to mating. Our results help understand the loss of
sexual reproduction by ant workers, a critical step in the extreme specialization of their phenotype. 相似文献
150.
Metal speciation in landfill leachates with a focus on the influence of organic matter 总被引:2,自引:0,他引:2
Claret F Tournassat C Crouzet C Gaucher EC Schäfer T Braibant G Guyonnet D 《Waste management (New York, N.Y.)》2011,31(9-10):2036-2045
This study characterises the heavy-metal content in leachates collected from eight landfills in France. In order to identify heavy metal occurrence in the different size fractions of leachates, a cascade filtration protocol was applied directly in the field, under a nitrogen gas atmosphere to avoid metal oxidation. The results of analyses performed on the leachates suggest that most of the metals are concentrated in the <30 kDa fraction, while lead, copper and cadmium show an association with larger particles. Initial speciation calculations, without considering metal association with organic matter, suggest that leachate concentrations in lead, copper, nickel and zinc are super-saturated with respect to sulphur phases. Speciation calculations that account for metal complexation with organic matter, considered as fulvic acids based on C1(s) NEXAFS spectroscopy, show that this mechanism is not sufficient to explain such deviation from equilibrium conditions. It is therefore hypothesized that the deviation results also from the influence of biological activity on the kinetics of mineral phase precipitation and dissolution, thus providing a dynamic system. The results of chemical analyses of sampled fluids are compared with speciation calculations and some implications for the assessment of metal mobility and natural attenuation in a context of landfill risk assessment are discussed. 相似文献