Heavy metals in the irrigation water, soils and vegetables in the Philippi horticultural area in the Western Cape Province of South Africa

The aims of this study were to investigate the extent of heavy metal contamination in the Philippi horticultural area in the Western Cape Province, South Africa. Concentrations of Cd, Cr, Cu, Mn, Ni, Pb and Zn were determined in the irrigation water, soils and vegetables in both winter and summer cropping seasons with an ICP-AES and tested against certified standards. Differences were found in heavy metal concentrations between the winter and summer cropping seasons in the irrigation water, soils and vegetables. Certain heavy metals exceeded the maximum permissible concentrations in the irrigation water, soils and vegetables produced in South Africa. These toxic concentrations were predominantly found in the summer cropping season for the soils and in the crops produced in winter. It is thus suggested that further studies are carried out in the Philippi horticultural area to determine the sources of the heavy metals to try and mitigate the inputs thereof and therefore reduce the amount of heavy metals entering the human food chain.ISI & Scopu

Non-stomatal ozone deposition to vegetation: new insights and models

Tropospheric ozone is a natural constituent of the troposphere but man-made emissions of NOx and VOCs have led to an increase in concentrations globally. Ozone plays an important role in the Earth System, e.g. damaging vegetation, modifying the oxidation potential of the atmosphere and by acting as a greenhouse gas. Dry deposition of ozone to terrestrial surfaces governs its potential to cause damage and provides an important atmospheric sink. Ozone is very reactive so readily deposits on most surfaces. It is also taken in through stomata as the plant respires and this stomatal uptake can cause damage to the plant. Stomatal uptake is estimated using existing stomatal conductance models that have been well characterized and evaluated. However non-stomatal deposition has not been well described in land-atmosphere exchange models to date. Several sets of ozone flux measurements have been collated to examine the non-stomatal deposition process. The data showed ozone deposition increased to dry canopies as temperature or solar radiation increased, consistent with the thermal decomposition of ozone on leaf cuticles or reactions with emitted biogenic VOCs. It was also found that the presence of surface water increased ozone deposition, probably due to aqueous chemical reactions with compounds in the water; therefore this may depend on the composition of cuticular waxes or the presence of other deposited compounds. A new parameterisation for non-stomatal ozone deposition to grassland and coniferous forests is derived and incorporated into a standard resistance type deposition model. This new model is evaluated using data reserved from the parameterization process and compared to other existing models

Auswirkungen dynamischer Veraenderungen der Luftzusammensetzung und des Klimas auf terrestrische Oekosysteme in Hessen. T. 1 Wirkungen ausgewaehlter Kohlenwasserstoffe und ihrer Folgeprodukte (insbesondere Ozon) auf Pflanzen

Der vorliegende Bericht ''Wirkung ausgewaehlter Kohlenwasserstoffe und ihrer Folgeprodukte auf Pflanzen'' enthaelt drei Beitraege zum Thema ''Wirkungen von Luftschadstoffen auf die Vegetation''. Der Beitrag ''Abschaetzung des Schaedigungspotentials von fluechtigen organischen Verbindungen bei direkter Einwirkung ueber den Luftpfad'' diskutiert die moeglichen Belastungspfade fuer den Schadstofftransfer Luft/Pflanze und geht dann die Hauptkomponentengruppen der fluechtigen organischen Verbindungen durch, um herauszuarbeiten, bei welchen Komponenten bzw. Komponentengruppen Schaedigungspotentiale fuer die Pflanzen bestehen. Die Reaktionen, mit denen gasfoermige organische Verbindungen in der Atmosphaere abgebaut werden, wurden in dem Uebersichtsartikel ''Luftchemische Reaktionen von fluechtigen organischen Verbindungen und ihrer Produkte'' zusammengestellt; Ozon hat an dem Abbau der meisten leichtfluechtigen Verbindungen einen wesentlichen Anteil. Der dritte Beitrag ''Ozon als Stressor fuer Pflanzen im Freiland - neue Erkenntnisse'' stellt dar, durch welche Einflussgroessen der Ozonfluss aus der Luft in die Pflanze bestimmt wird. (orig./MG)The report ''Impact of selected hydrocarbons and their daughter products on plants'' consists of three papers studying the effect of air pollutants on vegetation. The paper ''Assessment of the damage potential of volatile organic compounds acting directly via the atmospheric pathway'' discusses possible exposure pathways for pollutant transfer from the atmosphere to plants and looks one by one at the main component groups of volatile organic compounds in order to find out what components or component groups have damage potential for plants. Reactions by which gaseous organic compounds are degraded in the atmosphere are indicated in the contribution ''Air-chemical reactions of volatile organic compounds and their products''; ozone accounts essentially for the degradation of most light-volatile compounds. The third paper ''ozone as a stressor of plants in the field - new findings'' points out the factors of influence determining ozone flow from the atmosphere to plants. (orig./MG)SIGLEAvailable from TIB Hannover: RO 1602(179) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Challenges in understanding the risks to natural and semi-natural vegetation from ozone exposure

The effects of tropospheric ozone on crops and forests have been studied intensively, but effects on natural and semi- natural plant communities are poorly understood. This lack of understanding arises partly from a lack of experimental studies of whole mature communities, and the effects of ozone on competition and interactions with climate, nutrition etc., and partly from a lack of knowledge of the factors which predispose individual plant species to ozone damage. A recent review of the effects of ozone on grasslands (Bassin et al., 2007a) has drawn attention to the problems involved; this paper seeks to identify the practical issues that must be addressed in improving our knowledge and thereby identifying the risks associated with ozone exposure. This is a necessary first step before mitigation strategies can be developed

Auswirkungen von Ozon auf Pflanzen Bewertung hessischer Ozonprofile

Ziel der Studie ist es, die Ozon-Messdaten ausgewaehlter hessischer Luftmessstationen unter dem Gesichtspunkt einer moeglichen Gefaehrdung der Vegetation zu bewerten. Ein Modell, das nicht nur die O_3-Konzentrationen in der Umgebungsluft beschreibt, sondern auch die Austauscheigenschaften der Atmosphaere und die Senkeigenschaften der Pflanzen beruecksichtigt, und dessen Kenngroesse mit O_3-bedingten Schadauspraegungen bei Pflanzen in eindeutiger Weise in Beziehung steht, konnte fuer Nicotiana tabacum erstellt werden. Dabei koennen die Messgroessen von den lufthygienischen Messstationen des Bundes und der Laender zur Verfuegung gestellt werden: O_3-Konzentration in der Umgebungsluft, Lufttemperatur, Luftfeuchtigkeit, horizontale Windgeschwindigkeit, Globalstrahlung. Die Beurteilung der O_3-Belastung der Vegetation mit den neuen Kenngroessen RISK(1) und RISK(2) fuehrt zu einem aus oekotoxikologischer Sicht sinnvollerem Ergebnis als bei Verwendung der ueblichen Groessen. Zur Berechnung von Risikoparametern fuer verschiedene Agrarkulturen wurden Expositions-Wirkungs-Funktionen aus der Literatur herangezogen. Danach sind lediglich Gerste und Mais als O_3-tolerant anzusehen. Fuer alle anderen Kulturen sind grosse Toleranzunterschiede zwischen den Sorten und von Jahr zu Jahr zu verzeichnen. Auffaellig sind die hohen potentiellen Ertragsverluste bei Sommerweizen. In bisherigen Untersuchungen bleibt eine moegliche Kompensation der Ertragsverluste durch Ozon infolge der Erhoehung der CO_2-Konzentration von ca. 290 ppm auf derzeit ca. 360 ppm unberuecksichtigt: Bei gleichzeitiger Beruecksichtigung des CO_2-Duengeeffektes und des potentiellen O_3-bedingten Ertragsausfalles kompensieren sich die Effekte bei Annahme einer additiven Kombinationswirkung. Entsprechend liegen Prognosen fuer Ertragssteigerungen infolge ansteigender CO_2-Konzentrationen bei O_3-sensitiven Kulturen zu hoch. (orig./UWA)The study had the aim to evaluate ozone measuring data from selected air pollution measuring stations in Hessen with a view to possible hazards to the vegetation. A model which describes not only O_3 concentrations in the ambient air but takes also the exchange properties of the atmosphere and sink properties of plants into account and whose key parameter is related to O_3-induced disease symptoms in plants in an unequivocal manner could be evolved for Nicotiana tabacum. The following data for making use of this model can be provided by federal and laender air hygiene measuring stations: O_3 concentration in the ambient air, air temperature, air humidity, horizontal wind speed, global radiation. Assessing the O_3 exposure of the vegetation using the new parameters RISK(1) and RISK(2) leads to a more precise result in ecological terms than employing the quantities commonly used. - The calculation of risk parameters for different farm crops relies on exposure-and-effect functions mentioned in literature. According to these, only barley and maize are to be considered as O_3-tolerant. For all other crops great differences in tolerance from one species to another and between the different years are reported. The substantial potential drop in summer wheat yield is particularly striking. Previous investigations have not taken into account a possible compensation of lower yield through ozone by the increase of the CO_2 concentration from approximately 290 ppm to, currently, about 360 ppm: where the CO_2 fertilization effect and potential O_3-induced yield loss are simultaneously considered the two cancel each other out due, probably, to an additive combination effect. Accordingly, prognostications for higher yields because of the increase of the CO_2 concentration are incorrect where O_3 sensitive crops are concerned. (orig./UWA)Available from TIB Hannover: RO 1602(143) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Auswirkungen von Depositionen saurer Luftverunreinigungen auf Gruenlandoekosysteme Schlussbericht

TIB: FR 724+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman