Samples were taken of soils formed on volcanic material, primarily composed of rhyodacitic pumice, on the island of Thera, Greece (South Aegean Sea, Southeastern Mediterranean), and analyses for ...physical and chemical properties carried out. These soils are characterised as having a coarse texture, low organic matter content, low cation exchange capacity (CEC) and soil moisture retention, but a high pH despite the acidic nature of the parent material. Extraction with sodium dithionite–citrate, acid ammonium oxalate, sodium pyrophosphate and hot 0.5 M NaOH showed that, in contrast to soils usually forming on volcanic material worldwide, soils lack noncrystalline minerals like allophane, imogolite, ferrihydrite and iron and aluminium humus complexes. The only noncrystalline mineral present and, in great quantities, is amorphous silica. Winds, prevailing practically all year round, transfer droplets of seawater to these soils which in combination with the great porosity, relatively high sodium content of the parent material and low rainfall are the primary factors in the poor development of these soils and high pH. No andic properties are apparent and, hence, these soils cannot be classified as Andisols. The major factors determining soil genesis on the island of Thera would appear to be the nature of the parent material and the climate.
The effect of land use and precipitation on annual runoff and sediment loss was investigated in eight different sites along the northern Mediterranean region and the Atlantic coastline located in ...Portugal, Spain, France, Italy and Greece. These sites represent a variety of landscapes and are under a number of land-uses representative of the Mediterranean region, such as agricultural land with rainfed cereals, vines, olives, eucalyptus plantation or natural vegetation (shrubland). It was found that land use can greatly affect runoff and soil erosion. The greatest rates of runoff and sediment loss were measured in hilly areas under vines (average sediment loss 142.8 t km
−2 yr
−1). Areas cultivated with wheat are sensitive to erosion, especially during winter, generating intermediate amounts of runoff and sediment loss (17.6 t km
−2 yr
−1) especially under rainfalls higher than 280 mm per year. Olives grown under semi-natural conditions, as for example with an understory of vegetation of annual plants greatly restrict soil loss to nil values (0.8 t km
−2 yr
−1). Erosion in shrublands increased with decreasing annual rainfall to values in the range 280–300 mm and then it decreased with decreasing rainfall (average sediment loss 6.7 t km
−2 yr
−1).
Four pedons from the alluvial plain of Drama (NE Greece) were investigated in order to provide detailed information on their morphology, chemical, physical and mineralogical properties, ...classification and genesis. The clay content of all the samples is relatively high (>35%). Soil reaction with HCl ranges from slightly alkaline (7.2) to alkaline (pH 8.3). The organic matter content ranges from 0.53 to 1.03% in the surface horizons, while the other horizons contain considerably less. The CaCO3-equivalent content ranges between 0.1% and 18.1%. Due to ploughing, gilgai microrelief is absent, but slickenside was apparent in all of the soils studied. Smectite (montmorillonite) is the dominant clay mineral and was mainly inherited from the parent sediments and by neoformation. High smectite content, in combination with alternating wet–dry periods (xeric soil moisture regime), results in the formation of the morphological characteristics that are typical for Vertisols. The pedons located in the highest points of the alluvial plain were classified as Chromic Haploxererts and those in the lowest landscape were classified as Typic Haploxererts. Free iron oxides range between 1.3 and 1.9% for the Chromic Haploxererts to only 0.4–0.9% for the Typic Haploxererts. The properties of these Vertisols reflect the impact of climate (alternating wet–dry periods), landscape position (alluvial plain; seasonally water saturated), and parent material (clayey, smectite-dominated fluvio-lacustrine, highly calcareous sediments).
► Soils were characterized from four profiles of the alluvial plain of Drama, Greece. ► Parent material is clayey, smectite-rich fluvio-lacustrine, highly calcareous. ► Slickensides are frequent. Montmorillonite is the dominant clay mineral present. ► Soils were classified as Chromic Haploxerert, and as Typic Haploxerert. ► The parent material, landscape and climate favour the formation of Vertisols.
•Visible light active ultrafiltration (UF) membranes coated with modified nanostructured titania.•Modified membranes evaluated in a continuous flow photocatalytic reactor for water ...purification.•Efficient photocatalytic degradation of azo-dye model compounds under ambient operating temperature and low pressure.•Water permeability increased by photoinduced hydrophilicity effect.•Clean water with low installation and operating costs.
Visible light active ultrafiltration (UF) membranes coated with modified nanostructured titania (m-TiO2) were for the first time developed using a sol–gel preparation technique combined with a dip-coating deposition procedure. It has been confirmed that the structural, morphological and physicochemical properties of the modified titania membranes strongly depend on the dip-coating and calcination rates. The modified membranes were incorporated in a water purification photocatalytic reactor in continuous flow filtration conditions and tested for the photocatalytic degradation of azo-dye model compounds (namely methyl orange – MO and methylene blue – MB) with very promising results. The photocatalytic experiments took place under ambient operating temperature and low pressure without any compromise on the efficiency of the membrane's permeate flux. Without irradiation, the permeability drops with increasing flow rates of the solution that is forced to penetrate through their pore structure. The photocatalytic efficiency depends on the effluent flow rate however, under both UV and visible light, the permeability was continuously increasing due to the photoinduced hydrophilicity effect. Compared to MO, the MB pollutant was degraded at much higher rate due to its better adsorption, independently of the type of the membrane. The permeability of the membranes increases with the volume treated due to the wettability of the m-TiO2 treated membrane, rendering the need for regeneration or anti-fouling procedures unnecessary and making the process more energy efficient. Due to the low temperature function and the photoinduced hydrophilic effect of the modified TiO2 photocatalytic UF membranes, the photocatalytic reactor can efficiently work without any extra device, fact that leads to low installation and operating costs and provides an energy efficient procedure of cleaning polluted aqueous solutions.
In a two-year field experiment using flue-cured tobacco, carried out in Agrinio (western Greece), dry matter accumulation (DMA) was studied in addition to the uptake of the nutrients nitrogen (N), ...potassium (K), phosphorous (P), calcium (Ca), and magnesium (Mg) on a weekly basis during the period from transplant to harvest over two cultivation seasons. Whole plants were sampled and divided into leaves, stalks and roots. These were dried, weighed and DMA and the nutrient uptake determined. Both DMA and nutrient uptake in plant parts as well as in whole plants follows a sigmoidal curve, accurately described by a logistic equation. During growth there is a period when DMA and nutrient uptake in plant parts occurs at an intense rate. The time of onset of this period and its duration varies with different plant parts. Maximum daily DMA occurs when 50% of the maximum plant DMA has been achieved. Maximum daily nutrient uptake in aerial parts of the plant occurs approximately 1 week prior to the maximum daily DMA. The period of rapid DMA and nutrient uptake in flue-cured tobacco coincides with the knee-high and budding (rapid qrowth and elongation) stage (41–75 DAT). Consequently during this period, the soil must have sufficient nutrients available to supply the needs of the plant.
Experiments were conducted on pot marigold (Calendula officinalis L.) plants grown under glasshouse conditions to study interactions between Cd and Zn and the effects of these on the respective ...concentrations of these metals in plant tissues (leaves and petals). A factorial experiment with two factors (Cd and Zn) at five concentrations (0, 1, 5, 10, 15 mg kg-1) was carried out. Cadmium was applied as CdSO4•8/3H2O and Zn as ZnSO4•7H2O. Increasing Cd and Zn additions to the soil resulted in an increase in the concentration of Cd and Zn in plant tissues, as well as in the amounts of Cd and Zn extracted by diethylene triamine penta-acetic acid–triethanol amine (DTPA–TEA). Significant inhibitory effects of Zn on Cd concentration in the leaves occurred at levels above 5 mg Zn kg-1 soil. Zinc concentrations in the leaves decreased, while those in the petals increased with increasing rates of applied Cd. Cd application increased the Cd/Zn ratio and Zn application reduced the Cd/Zn ratio of plant tissue. DTPA-TEA-extractable Cd and Zn significantly correlated with the Cd and Zn concentrations within the leaves and petals, indicating that such determinations could be used to predict Cd and Zn concentrations in the plant tissues of pot marigold.
In west Crete, Greece we studied the effect of land management practices, tillage and no tillage, on physical and chemical properties of autochthonous soils that were formed in marls, conglomerates ...or schists in slopes higher than 10%. Soil organic matter content was higher in the case of no tillage in soils formed on conglomerates. The conglomerates soil content in available P was 8.27 mg kg-1 in the case of no-tillage and 2.87 mg kg-1 in tillage while in soils formed on marls it was 26.65 and 16.83 mg kg-1, respectively. No statistically significant differences were recorded between the treatments in exchangeable K, pH, equivalent CaCO3 and CEC. The effects of alternative land management practices such as conservation tillage or no tillage on soil properties, natural resources conservation and the productivity of olive groves are discussed in the light of the presented results.
The effect of nitrogen application on biomass accumulation and nutrient uptake by okra (Abelmoschus esculentus (L.) Moench.) grown in an unheated greenhouse was determined. Nitrogen (N) was applied ...in the form of a liquid feed at 0 (N-0), 150 (N-150) and 300 (N-300) ppm while other nutrients were maintained at a constant level. The accumulation of dry matter in the aerial plant parts (DMAe) and nutrient uptake (N, P, K, Ca, Mg) by the aerial plant parts (NUe) were recorded throughout the growth period. The data were analysed with the aid of logistic equations to determine the maximum daily DMAe and total NUe in relation to DMAe. Both DMAe and NUe follow a sigmoid curve, accurately described by a logistic equation. From the results it was found that during growth there was a period when DMAe occurred at an intense rate. The time of onset of this period and its duration varied with N application. Maximum daily DMAe (RDMAe) as well as maximum daily NUe (RNUe) occurred when 50% of the maximum DMAe and NUe had been achieved, irrespective of N application. The maximum daily uptake of N (RN-NUe) and K (RK-NUe) by the plant occurred about 2-6 days earlier than the RDMAe, irrespective of N-level. In addition, although the uptake of P (P-NUe) was low, maximum daily P-NUe also occurred prior to the maximum daily DMAe. However, the maximum daily uptake of the other ions that were measured (Ca and Mg) was less clearly defined.
We investigated the correlation between systolic and diastolic nocturnal blood pressure (BP) values and office BP values, as well as parameters of 24-hour ambulatory BP monitoring, in patients with ...hypertension. In addition, we compared nocturnal hypertensives with nocturnal normotensives regarding their demographic, clinical, and laboratory characteristics, as well as other data from 24-hour BP monitoring.
The study included 182 consecutive patients who had newly diagnosed, never treated, uncomplicated arterial hypertension. Blood samples were obtained from all patients for the determination of glycaemic and lipidaemic profiles. All underwent a complete echocardiographic examination, including tissue Doppler imaging, measurement of carotid intima-media thickness, measurement of carotid-femoral pulse wave velocity, and determination of the augmentation index of reflected waves (Aix@75), as well as 24-hour ambulatory BP monitoring. The population was divided into nocturnal normotensives (NN, n=77) and nocturnal hypertensives (NH, n=105, nocturnal BP >120/70 mmHg).
Although the NH did not differ from the NN as regards the classical cardiovascular risk factors, they showed an excessive inotropic response to exercise (61.9% vs. 22.7%, p=0.028), higher levels of serum uric acid (5.5 ± 1.56 mg/dl vs. 4.7 ± 1.36 mg/dl, p=0.003), as well as greater arterial stiffness, as expressed by a higher carotid-femoral pulse wave velocity (8.6 ± 1.6 m/s vs. 7.9 ± 1.4 m/s, p=0.009), and a greater carotid intima-media thickness (0.74 ± 0.17 mm vs. 0.68 ± 0.15 mm, p=0.007). In addition, although the two groups did not differ significantly as regards office BP values and did not show strong correlations between nocturnal and office BP, both nocturnal diastolic and, especially, systolic BP showed strong correlations with levels of serum uric acid and with subclinical lesions in the heart, central aorta, peripheral vessels, and renal vasculature.
Nocturnal BP is poorly correlated with office BP values. However, the presence of nocturnal hypertension is associated with morphological and functional disturbances of the cardiovascular net. 24-hour ambulatory BP monitoring is an essential tool for revealing this subgroup of hypertensive patients who are at increased cardiovascular risk.
