Emissions by aerial routes from protected crop systems (greenhouses and crops grown under cover) : a position paper

This report describes the processes that may lead to emission of Plant Protection Products (PPP) from protected cultivation, through aerial routes. The introduction gives the background for this work and the limitations, outlining in particular why receptors other than air are not explicitly addressed here. Chapters 2 discusses the physical background of greenhouse air exchanges and the factors that affect it. Existing models for estimating ventilation of the different types of greenhouses are reviewed there. Chapter 3 gives a scientific argument about the processes and the factors that may affect aerial emissions of PPP from protected cultivations. The parameters that may have an high impact on the emission are identified there as well. A review of the knowledge needed and of the models that may be available for scoring each emission route is given in Chapter 4. In Chapter 5 a strategy is proposed to reduce/group the number of factors that are important (and to score their relevance) through some model calculations. An outline of the calculations that would be needed for ranking and eventually scoring the emissions and, possibly, highlight groupings of combinations that are similar with respect to emissions, is given

Steering of fogging: control of humidity: temperature or transpiration

Fogging systems are increasingly used to cool greenhouses and prevent water stress. More recently, fogging systems are applied also in relatively low radiation environments (such as The Netherlands), for a better control of product quality than whitewashing and to reduce need for natural ventilation ¿ thus allowing for higher CO2 concentrations to be maintained in the greenhouse. Most commonly the steering of such systems is done by setting an upper limit to the deficit of specific humidity that, whenever exceeded, triggers the fogging system. In both cases, however, one may wonder whether static and pre-fixed set points are the most effective choice. In the experiment presented in this paper, fogging and venting were controlled with the purpose of steering crop transpiration. The desired transpiration rate was the input of an algorithm that calculated on-line the required humidity and air temperature set points in view of the current weather factors. The set points were then the input of a standard P-controller that calculated vent opening and time of operation of the fogging system. In this paper, the resulting climate and actuator control operations are discussed and compared with a similar greenhouse controlled in a traditional fashion. The study concluded that a desired crop transpiration rate (an all-round indicator of crop well-being) could be used to select dynamic set points for the climate control in a greenhouse equipped with a fogging system

Transverse motions in CSOs?

The measurement of proper motions in CSOs is a powerful tool to determine the dynamical evolution of the newly born extragalactic radio sources. We observed 3 CSOs with the VLBA in 2004 and in 2006 to monitor changes in their structure and measure the separation velocity of the hot spots. It is important to increase the size of the samples of CSOs with measured expansion velocity to test the existance of frustrated objects, and put stringent constraints on the current models. We found for all the three objects observed a transverse motion of the hotspots, and we suggest as the more likey explanation a precession in the jet axis. This behaviour likely inhibits or at least slows down the radio source growth because the head of the hotspot continuously hits new regions of the ISM. Therefore these radio sources may represent an old population of GPS/CSOs.Comment: 4 pages, 3 figures. Accepted for publication in Astronomische Nachrichte

High temperature control in mediterranean greenhouse production: The constraints and the options

In the open field, the environment is a critical determinant of crop yield and produce quality and it affects the geographical distribution of most crop species. In contrast, in protected cultivation, environmental control allows the fulfillment of the actual needs depending on the technological level. The economic optimum, however, depends on the trade-off between the costs of increased greenhouse control and increase in return, dictated by yield quantity, yield quality and production timing. Additional constraints are increasingly applied for achieving environmental targets. However, the diverse facets of greenhouse technology in different areas of the world will necessarily require different approaches to achieve an improved utilization of the available resources. Although advanced technologies to improve resource use efficiency can be developed as a joint effort between different players involved in greenhouse technology, some specific requirements may clearly hinder the development of common “European” resource management models that, conversely should be calibrated for different environments. For instance, the quantification and control of resource fluxes can be better accomplished in a relatively closed and fully automated system, such as those utilized in the glasshouse of Northern-Central Europe, compared to Southern Europe, where different typologies of semi-open/semi-closed greenhouse systems generally co-exist. Based on these considerations, innovations aimed at improving resource use efficiency in greenhouse agriculture should implement these aspects and should reinforce and integrate information obtained from different research areas concerning the greenhouse production. Advancing knowledge on the physiology of high temperature adaptation, for instance, may support the development and validation of models for optimizing the greenhouse system and climate management in the Mediterranean. Overall, a successful approach will see horticulturists, plant physiologists, engineers and economists working together toward the definition of a sustainable greenhouse system

The Galactic structure and chemical evolution traced by the population of planetary nebulae

We use an extended and homogeneous data set of Galactic planetary nebulae (PNe) to study the metallicity gradients and the Galactic structure and evolution. The most up-to-date abundances, distances (calibrated with Magellanic Cloud PNe) have been employed, together with a novel homogeneous morphological classification, to characterize the different PN populations. We confirm that morphological classes have a strong correlation with PN Peimbert's Type, and also with their distribution on the Galactic landscape. We studied the alpha-element distribution within the Galactic disk, and found that the best selected disk population, together with the most reliable PN distance scale yields to a radial oxygen gradient of d[log(O/H)]/dR=-0.023 +- 0.006 dex/ kpc for the whole disk sample, and of d[log(O/H)]/dR= -0.035+-0.024, -0.023+-0.005, and -0.011+-0.013 dex/kpc respectively for Type I, II, and III PNe. Neon gradients for the same PN types confirm the trend. Accurate statistical analysis show moderately high uncertainties in the slopes, but also confirm the trend of steeper gradient for PNe with more massive progenitors, indicating a possible steepening with time of the Galactic disk metallicity gradient. The PN metallicity gradients presented here are consistent with the local metallicity distribution; furthermore, oxygen gradients determined with young and intermediate age PNe show good consistency with oxygen gradients derived respectively from other young (OB stars, HII regions) and intermediate (open cluster) Galactic populations. We also extend the Galactic metallicity gradient comparison by revisiting the open cluster [Fe/H] data from high resolution spectroscopy. The analysis suggests that they could be compliant with the same general picture of a steepening of gradient with time.Comment: ApJ, in pres