C. Haidouti

Variations in plant and soil lead and cadmium content in urban parks in Athens, Greece

The concentrations of Pb and Cd were studied in the plant species Pittosporum sinensis (Mock-orange) and Nerium oleander (Oleander) and in the soil of two major parks of Athens. The composition and the density of vegetation differs remarkably in the two parks. The concentrations of both metals were considerably higher at the peripheral zones and decreased towards the interior of the parks. At a distance of 60 m from the periphery to central zones the values almost reached background levels. The degree of plant and soil contamination was well correlated to the density and the structure of vegetation, the traffic volumes, the nature of the leaf surface of the two plants and the wind velocity.

Inactivation of mercury in contaminated soils using natural zeolites.

The application of zeoliferous rocks, from Metaxades region (Thrace, Greece) to soils contaminated with mercury significantly reduced the concentrations of mercury in the shoots and roots of alfalfa (Medicago sativa L.) and ryegrass (Lolium perenne). Use of natural zeolites at application rates of 1%, 2% and 5% by soil weight caused reductions in mercury concentrations of up to 86.0% in shoots and 58.2% in roots, compared with controls with no added zeolites. The reductions are more pronounced in above-ground plant material than in roots of the two plant species. The use of natural zeolites, as soil additives, to reduce the uptake of mercury by plants and the restriction of the entry of mercury into the food chain, is noted.

A comparison of wet oxidation methods for determination of total phosphorus in soils

For 15 soils with widely different extractability of phosphorus (P) two newly introduced digestion techniques for determining total P (Pt) were compared with the standard perchloric acid digestion procedure. The two digestion techniques were: (1) concentrated H2SO4 plus 30 % H2O2 at 360 °C, (2) concentrated HCl plus concentrated HNO3 in the ratio 3:1 (aqua regia) at 140 °C. Almost equal amounts of Pt were extracted by the two methods (mean = 188.7 mg kg—1 for H2SO4/H2O2 and 188.4 mg kg—1 for aqua regia) which were slightly higher than the standard method (mean = 183.8 mg kg—1). However, there is no statistical difference among the three digestion methods, suggesting that the tested methods should be useful for estimating Pt in soils with high content of organic C, eliminating the danger of explosion when hot concentrated HClO4 is used. Ein Vergleich verschiedener Aufschlussverfahren zur Bestimmung des Gesamt-Phosphors in Boden. An 15 Bodenproben mit unterschiedlichen physikalisch-chemischen Eigenschaften wurde die Eignung von zwei Nassoxidationsverfahren zur Bestimmung des Gesamt-Phosphor-Gehaltes (Pt) im Vergleich zur Standard-Methode, Aufschluss mit HClO4, gepruft. Bei den beiden neuen Nassoxidationsverfahren wird der Boden (1) mit konzentrierter H2SO4 und 30%igem H2O2 auf 360 °C erhitzt bzw. (2) mit konzentrierter HCl und konzentrierter HNO3 im Verhaltnis 3:1 („Konigswasser“) auf 140 °C erhitzt. Mit beiden angewandten Test-Verfahren wurden gleiche Mengen P extrahiert. Im Durchschnitt wurden 188,7 mg kg—1 mit H2SO4/H2O2-Extraktion und 188,4 mg kg—1 mit HCl/HNO3-Extraktion bestimmt. Diese Werte liegen hoher im Vergleich zu den Ergebnissen der Standard-Methode. Es ergeben sich keine gravierenden statistischen Unterschiede zwischen den drei angewandten Verfahren. Der Vorteil der untersuchten Test-Verfahren liegt darin, dass bei der Durchfuhrung des Aufschlusses keine Explosionsgefahr, wie bei der Standard-Methode mit konzentrierter und erwarmter HClO4, besteht.

Comparative effects of organic and conventional apple orchard management on soil chemical properties and plant mineral content under Mediterranean climate conditions

The effects of conventional and organic management systems on soil chemical properties and leaf nutrients under Mediterranean conditions were studied over a 2-year period on adjacent commercial apple orchards in Southern Greece. The soil in both orchards was characterised as a clay loam–clay and was uniform in morphological and physical properties. The results indicated no significant differences in soil chemical properties between the different management systems, including soil organic matter (SOM), pH, cation exchange capacity (CEC) and C/N ratio. However, soil samples from the conventional orchard exhibited significantly higher values (p< 0.01) of electrical conductivity (EC) and higher concentrations of K, Ca, Na, Cu and Zn, which were likely the result of chemical fertiliser application. Despite the fact that organic systems promote the accumulation of soil organic matter and fertility over time through the use of organic sources, in our study, the SOM values declined, suggesting that the type and the rate of organic matter input in the organic orchard were insufficient. The leaf nutrients, with the exception of P and Ca, were within the sufficiency range in both management systems. The present findings did not provide evidence of major differences in the leaf macronutrient content between conventionally and organically grown apple trees. Nevertheless, our leaf analysis revealed higher concentrations of Zn in the conventionally grown trees and opposite results for Cu, probably due to the extensive use of copper-containing fungicides in organic orchards in Greece.

Plant uptake of 134Cs in relation to soil properties and time.

134Cs uptake by sunflower and soybean plants grown on seven different soils and its relation to soil properties were studied in a greenhouse pot experiment. Soil in each pot was contaminated by dripping the 134Cs in layers, and sunflower and soybean plants were grown for three and two successive periods, respectively. 134Cs plant uptake was expressed as the transfer factor (TF) (Bq kg(-1) plant/Bq kg(-1) soil) and as the daily plant uptake (flux) (Bq pot(-1) day(-1)) taking into account biomass production and growth time. For the studied soils and for both plants, no consistent trend of TFs with time was observed. The use of fluxes, in general, provided less variable results than TFs and stronger functional relationships. A negative power functional relationship between exchangeable potassium plus ammonium cations expressed as a percentage of cation exchange capacity of each soil and 134Cs fluxes was found for the sunflower plants. A similar but weaker relationship was observed for soybean plants. The significant correlation between sunflower and soybean TFs and fluxes, as well as the almost identical highest/lowest 134Cs flux ratios, in the studied soils, indicated a similar effect of soil characteristics on 134Cs uptake by both plants. In all the studied soils, sunflower 134Cs TFs and fluxes were significantly higher than the respective soybean values, while no significant difference was observed in potassium content and daily potassium plant uptake (flux) of the two plants.

Characterization of iron oxides in Fe-rich concretions from an imperfectly-drained Greek soil: a study by selective-dissolution techniques and X-ray diffraction

Fe-rich concretions commonly occur in Greek soils with alternating drying and waterlogging periods. This study was conducted to characterize the iron oxides in Fe-rich concretions from the upper solum of an Alfisol with seasonal perched water table by the combination of selective dissolution and X-ray diffraction (XRD) techniques. The results showed that more than 75% of the total iron (Fet) was associated with the crystalline and the amorphous Fe oxides, indicating a strong accumulation of free iron oxides (Fed) in concretions. Amorphous iron compounds (Feo) was present at high concentrations and fluctuated with profile depth. The active Fe ratio (Feo/Fed) values that ranged from 0.35 to 0.41 reflected an association of poorly crystalline goethite with some ferrihydrite. The XRD data showed that the Fe-rich concretions consisted of quartz, feldspars, illite and gypsum. The mineralogy of iron oxides in concretions was determined by comparison of XRD patterns for dithionite-citrate-bicarbonate (DCB) treated (deferrated) and untreated (non-deferrated) samples. Poorly crystalline goethite as demonstrated by broad lines in the diffraction patterns and ferrihydrite were the iron oxides detected in the concretions. This mineral assemblage appears to be related to the pedoenvironmental conditions in which the concretions were formed and indicates that the mechanisms governing the formation of crystalline Fe oxides from ferrihydrite are retarded by the presence of crystallization inhibitors.

134Cs uptake by four plant species and Cs-K relations in the soil-plant system as affected by Ca(OH)2 application to an acid soil.

Three rates of Ca(OH)(2) were applied to an acid soil and the (134)Cs uptake by radish, cucumber, soybean and sunflower plants was studied. The (134)Cs concentration in all plant species was reduced from 1.6-fold in the sunflower seeds to 6-fold in the soybean vegetative parts at the higher Ca(OH)(2) rate. Potassium (K) concentration in plants was also reduced, but less effectively. The significantly decreased (134)Cs-K soil to plant distribution factors (D.F.) clearly suggest a stronger effect of soil liming on (134)Cs than on K plant uptake. This observation was discussed in terms of ionic interactions in the soil matrix and within the plants. The results also indicated that the increased Ca(2+) concentration in the exchange phase and in the soil solution along with the improved root activity, due to the soil liming, enhanced the immobilization of (134)Cs in the soil matrix and consequently lowered the (134)Cs availability for plant uptake.

Effects of fluoride pollution on the mobilization and leaching of aluminum in soils

Abstract The objective of this study is to demonstrate the effects of fluoride pollution on the mobilization and leaching of aluminum in soils. For this reason different soil samples were percolated under laboratory conditions with solutions containing F, such as NaF, KF and Na 3 AlF 6 , which are known to be constituents of aerosols emitted from Al smelters. The leaching effects of these F solutions were compared with those of distilled H 2 O, KCl and NaCl solutions, respectively. For all soil samples Al was leached more effectively when the percolating solution contained F instead of Cl. Fluoride-containing solutions induce substantial losses of Al. The leaching losses from the contaminated soil were higher than those from the uncontaminated soils. In the uncontaminated soils the losses from the acid soil were higher than those from the calcareous soil.

Sorption Behavior of Cesium in Two Greek Soils: Effects of Cs Initial Concentration, Clay Mineralogy, and Particle-size Fraction

The characteristics of Cs sorption behavior in two soils (soil 1 and soil 2) with nearly the same clay content and exhangeable K concentration, but with different clay mineralogy, were studied by the quantification of the distribution coefficient (kd). It was observed that as the initial Cs concentration increased from 4 to 50 mg L−1, the kd values decreased in both soils, suggesting a progressive saturation of Cs available sorption sites. However, the presence of expansible 2:1 phyllosilicates minerals in the clay fraction of soil 2 maintained a high Cs sorption ability for this soil, even at high Cs concentrations. The experimental data were also fitted to the Freundlich isotherm and the results showed that parameters of the Freundlich equation could be used to estimate the degree of Cs sorption and the nature of the available sorption sites. For the studied soils, the kf and the kd values followed a similar trend and the n Freundlich constant values provided a reliable indicator for the soils’ clay mineralogy. The removal of the sand fraction enhanced Cs sorption in both soils and the absence of sorbed Cs ions on the quartz minerals, as observed by the SEM analysis, additionally supported the effect of particle-size fraction on Cs sorption.

Growth, Nutrient Status, and Biochemical Changes of Sour Orange Plants Subjected to Sodium Chloride Stress

Sour orange is a valuable citrus rootstock. It is characterized as salt tolerant, based mainly on the mineral content of the leaves and roots under saline environment and to a lesser extent based on any biochemical indices. Therefore, the aim of the present experiment was to study both nutrient content and biochemical changes involved in this rootstocks tolerance. One-year-old sour orange (Citrus aurantium L.) trees growing in 5-L pots were subjected to four levels of sodium chloride salinity stress (control, 40 mM, 80 mM, and 120 mM sodium chloride) for 60 days. At the end of the stress period, plant growth was evaluated by measuring leaf, shoot, and root dry weights. Carbohydrates, chlorophylls, lipid peroxidation, and electrolyte leakage were also determined in leaves. Plant nutrient status was evaluated in leaf, shoot, and root samples, and the soil was also analyzed for nutrient content. Leaf sclerophylly indexes were determined to assess water stress induced by salinity. Leaf dry weight was not significantly affected, whereas shoot and root dry weights decreased with salt stress. Soil electrical conductivity and sodium and chloride concentrations increased with increasing salt concentration, whereas available potassium concentration decreased. Salt stress induced a significant accumulation of sodium and chloride in leaves, shoots, and roots. Potassium and phosphorus concentrations in leaves were enhanced under salt stress, whereas inconsistent changes were detected concerning magnesium, zinc, manganese, and copper concentrations. Sucrose and glucose concentrations were significantly reduced under salt stress while fructose concentration did not exhibit significant changes. Chlorophyll concentration was also reduced under stress. Based on lipid peroxidation and electrolyte leakage indexes, cell membrane integrity was maintained. According to leaf characteristics indexes, leaves’ water stress was negligible, even after 2 months under salt stress. Based on the present results, sour orange accumulated significant amounts of sodium and chloride ions, inducing a reduction of growth, possibly through a reduction of carbon assimilation rate under low chlorophyll content, resulting in reduced carbohydrate concentration in the leaves.