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71.
72.
Tatiana Klompenhouwer Henk van den Belt 《Journal of Agricultural and Environmental Ethics》2003,16(6):545-556
Due to the rise of functional foods,the distinction between foods and medicines hasbecome increasingly blurred. A new EUregulation covering health claims and otherclaims on food and drink products is on thedocks. A basic motive of legal regulation oflabeling and advertising is to inform andprotect the consumer. Promotion of informedchoice and consumer protection may, however, beconflicting objectives. A further problemsprings from the fact that choice, likeconsent, is a propositional attitude andtherefore opaque. Thus it is extremelydifficult for regulators to fasten onparticular formulations of claims. Despite theprofessed respect for the autonomy of theconsumer, paternalism is never far away andeasily enters in various guises. 相似文献
73.
Henk Breman 《Agriculture, ecosystems & environment》1984,11(3):272-273
74.
Joana F. M. F. Cardoso Johannes IJ. Witte Henk W. van der Veer 《Marine Biology》2007,152(6):1271-1282
In estuarine areas, bivalve species can be found in a variety of environments, where they experience large differences in
environmental conditions. In the present paper, the importance of different habitats (intertidal, subtidal and adjacent coastal
waters) for the persistence of the population was evaluated for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea estuary. Intra-specific variation in growth and reproductive output were followed during
the year and related to local abiotic conditions. Significant differences in growth and reproductive investment were found
between locations. Young individuals were mostly found in the intertidal area, where growth in terms of somatic mass was good.
These areas were not favourable for adult individuals, since growth in shell length was low and many individuals did not reproduce.
In the subtidal, where the highest densities were found, somatic and gonadal mass indices were low. Coastal areas had the
lowest densities and showed high growth in terms of shell length and body mass. The habitat with the highest reproductive
effort per individual was not the most important habitat in terms of reproductive output due to differences in density and
in size of the habitat type. For M. balthica, the subtidal habitat contributed the most to the reproductive output of the western Dutch Wadden Sea population although
the highest reproductive output per individual was in the coastal area. 相似文献
75.
Adaptive superparasitism and patch time allocation in solitary parasitoids : the influence of pre-patch experience 总被引:3,自引:0,他引:3
Marcel E. Visser Jacques J. M. van Alphen Henk W. Nell 《Behavioral ecology and sociobiology》1992,31(3):163-171
Summary Dynamic optimal diet models predict that host selection decisions and patch time allocation are influenced by the resource value of the habitat. We tested these predictions using the solitary' parasitoid Leptopilina heterotoma. Assuming that travel times between patches, the quality of previously visited patches and parasitoid density affect the parasitoids' estimation of the resource value of the habitat, different treatments were given before introducing parasitoids singly to a patch containing 5 unparasitized and 15 parasitized hosts. The decision to superparasitize is only slightly influenced by the rate of patch encounter. The quality of the previously visited patch has a strong influence. When a poor patch has been visited on the previous day, more superparasitism is observed in the partly depleted patch than when a rich patch has been searched. More superparasitism is also observed when the parasitoids are kept with conspecifics before the experiment than when they are kept alone. Increasing patch residence times are observed as the quality of the previously presented patch decreases. Host selection decisions and patch time allocation are thus clearly influenced by the pre-patch experience of the parasitoid, as predicted by dynamic optimal diet models. This can also explain why females that have never oviposited in unparasitized hosts will superparasitize readily.
Correspondence to: M.E. Visser 相似文献
76.
77.
van Breukelen BM Griffioen J Röling WF van Verseveld HW 《Journal of contaminant hydrology》2004,70(3-4):249-269
The biogeochemical processes governing leachate attenuation inside a landfill leachate plume (Banisveld, the Netherlands) were revealed and quantified using the 1D reactive transport model PHREEQC-2. Biodegradation of dissolved organic carbon (DOC) was simulated assuming first-order oxidation of two DOC fractions with different reactivity, and was coupled to reductive dissolution of iron oxide. The following secondary geochemical processes were required in the model to match observations: kinetic precipitation of calcite and siderite, cation exchange, proton buffering and degassing. Rate constants for DOC oxidation and carbonate mineral precipitation were determined, and other model parameters were optimized using the nonlinear optimization program PEST by means of matching hydrochemical observations closely (pH, DIC, DOC, Na, K, Ca, Mg, NH4, Fe(II), SO4, Cl, CH4, saturation index of calcite and siderite). The modelling demonstrated the relevance and impact of various secondary geochemical processes on leachate plume evolution. Concomitant precipitation of siderite masked the act of iron reduction. Cation exchange resulted in release of Fe(II) from the pristine anaerobic aquifer to the leachate. Degassing, triggered by elevated CO2 pressures caused by carbonate precipitation and proton buffering at the front of the plume, explained the observed downstream decrease in methane concentration. Simulation of the carbon isotope geochemistry independently supported the proposed reaction network. 相似文献
78.
van Breukelen BM Röling WF Groen J Griffioen J van Verseveld HW 《Journal of contaminant hydrology》2003,65(3-4):245-268
The biogeochemical processes were identified which improved the leachate composition in the flow direction of a landfill leachate plume (Banisveld, The Netherlands). Groundwater observation wells were placed at specific locations after delineating the leachate plume using geophysical tests to map subsurface conductivity. Redox processes were determined using the distribution of solid and soluble redox species, hydrogen concentrations, concentration of dissolved gases (N(2), Ar, and CH(4)), and stable isotopes (delta15N-NO(3), delta34S-SO(4), delta13C-CH(4), delta2H-CH(4), and delta13C of dissolved organic and inorganic carbon (DOC and DIC, respectively)). The combined application of these techniques improved the redox interpretation considerably. Dissolved organic carbon (DOC) decreased downstream in association with increasing delta13C-DOC values confirming the occurrence of degradation. Degradation of DOC was coupled to iron reduction inside the plume, while denitrification could be an important redox process at the top fringe of the plume. Stable carbon and hydrogen isotope signatures of methane indicated that methane was formed inside the landfill and not in the plume. Total gas pressure exceeded hydrostatic pressure in the plume, and methane seems subject to degassing. Quantitative proof for DOC degradation under iron-reducing conditions could only be obtained if the geochemical processes cation exchange and precipitation of carbonate minerals (siderite and calcite) were considered and incorporated in an inverse geochemical model of the plume. Simulation of delta13C-DIC confirmed that precipitation of carbonate minerals happened. 相似文献
79.
Dico Fraters Gerard J. F. L. Boom Leo J. M. Boumans Henk de Weerd Monique Wolters 《Environmental monitoring and assessment》2017,189(2):83
The solute concentration in the subsoil beneath the root zone is an important parameter for leaching assessment. Drainage centrifugation is considered a simple and straightforward method of determining soil solution chemistry. Although several studies have been carried out to determine whether this method is robust, hardly any results are available for loess subsoils. To study the effect of centrifugation conditions on soil moisture recovery and solute concentration, we sampled the subsoil (1.5–3.0 m depth) at commercial farms in the loess region of the Netherlands. The effect of time (20, 35, 60, 120 and 240 min) on recovery was studied at two levels of the relative centrifugal force (733 and 6597g). The effect of force on recovery was studied by centrifugation for 35 min at 117, 264, 733, 2932, 6597 and 14,191g. All soil moisture samples were chemically analysed. This study shows that drainage centrifugation offers a robust, reproducible and standardised way for determining solute concentrations in mobile soil moisture in silt loam subsoils. The centrifugal force, rather than centrifugation time, has a major effect on recovery. The maximum recovery for silt loams at field capacity is about 40%. Concentrations of most solutes are fairly constant with an increasing recovery, as most solutes, including nitrate, did not show a change in concentration with an increasing recovery. 相似文献
80.
Kees Koffijberg Hans Schekkerman Henk van der Jeugd Menno Hornman Erik van Winden 《Ambio》2017,46(2):241-250
The Netherlands is important for wintering migratory herbivorous geese, numbers of which have rapidly increased, leading to conflict with agriculture. In 2005/2006, a new goose management policy aimed to limit compensation payments to farmers by concentrating foraging geese in 80 000 ha of designated ‘go’ areas—where farmers received payment to accommodate them—and scaring geese from ‘no go’ areas elsewhere. Monthly national counts of four abundant goose species during 10 years prior to the new policy and in 8 years following implementation found that 57% of all goose days were spent within ‘go’ areas under the new management, the same as prior to implementation. Such lack of response suggests no predicted learning effects, perhaps because of (i) increases in abundance outside of ‘go’ areas, (ii) irregularly shaped boundaries and enclaves of ‘no go’ farmland within ‘go’ areas and/or (iii) insufficient differences in disturbance levels within and outside designated areas. 相似文献