Greek Soils Research Articles

Preliminary investigation of the use of Silybum marianum (L.) Gaertn. as a Cd accumulator in contaminated Mediterranean soils: the relationships among cadmium (Cd) soil fractions and plant Cd content

The plant Silybum marianum (L.) Gaertn. has been used in a preliminary study to investigate its phytoremediation potential in moderately and heavily Cd-polluted Greek soils. For this purpose, a pot experiment was carried out using four soil treatments, two from agricultural and two from urban areas, contaminated with 3 and 30 mg of Cd per kg of soil. The modified Bureau of Community Reference (BCR) fractionation method was used to determine Cd levels in the soil fractions. The water-soluble, available-DTPA extractable, total and pseudo-total concentrations of Cd were also evaluated and attempts to find relationships between Cd soil fractions and Cd levels in the parts of the cultivated plants were made. Significant correlations among Cd soil fractions, Cd plant parts, and soil physicochemical parameters were obtained and discussed. High Cd translocation and accumulation rates were observed mainly in the root and the lower part of the stems, while in flowers and seeds no Cd was detected, leading to the conclusion that the high-value product contained in the seeds maintains its quality and is free of contaminants. The results are satisfactory indicating Silybum marianum (L.) Gaertn. as a promising plant for remediation practices in Cd-contaminated Mediterranean soils, promoting the principles of circular economy.

Se(IV)/Se(VI) adsorption mechanisms on natural and on Ca-modified zeolite for Mediterranean soils amended with the modified zeolite: prospects for agronomic applications

In the present study, the ability of a modified CaCl2 zeolite (Ca-Z) to both increase Se(IV) availability and restrict Se(VI) mobility in soils is examined. As it was resulted from batch experiments and verified by X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies, higher amounts of both Se species adsorbed on Ca-Z compared to natural zeolite (Z-N) forming outer-sphere complexes while the oxidation state did not alter during agitation of samples. Thereafter, Ca-Z was incorporated in six Greek soils, divided into acid and alkaline, at a 20% (w/w) rate and a series of equilibrium batch experiments were performed with soils alone and soils-Ca-Z mixtures to investigate sorption and desorption processes and mechanisms. The acid soils, either treated with Ca-Z or not, adsorbed higher amounts of Se(IV) than alkaline ones, whereas soils alone did not adsorb Se(VI) but impressively high adsorption of Se(VI) occurred in the Ca-Z-treated soils. Desorption of Se(IV) was higher from the Ca-Z-treated soils and especially from the acid soils. Higher distribution coefficients of desorption than the distribution coefficients of sorption were observed, clearly pointing to a hysteresis mechanism. The experimental data fitted with Langmuir and Freundlich isotherms. In the presence of Ca-Z, the Langmuir qm values increased indicating higher Se(IV) retention while Langmuir bL values decreased suggesting lower bonding strength and higher Se(IV) mobility. Overall, treating the soils with Ca-Z increased Se(IV) adsorption and mobility whereas it provided sites for Se(VI) adsorption that did not exist in the studied soils.

Genetic diversity and phylogeny of indigenous rhizobia nodulating faba bean (Vicia faba L.) in Greece

The genetic diversity and phylogeny of fast-growing rhizobia isolated from root nodules of Vicia faba grown in different geographical regions of Greece were assessed. Although Rhizobium leguminosarum sv. viciae is the most common symbiont of Vicia spp. in European soils, there is no available information on native rhizobia nodulating faba bean in Greece. Seventy bacterial strains were isolated and grouped into sixteen distinct profiles based on BOX-PCR fingerprinting. The phylogenetic affiliation was further defined by sequence analysis of the rrs and multilocus sequence analysis (MLSA) of three housekeeping genes (recA, atpD and gyrB). Fifty-eight isolates were affiliated with recently described genospecies gsF-2, represented by R. laguerreae FB206T, whereas six isolates were closely related to gsB and two isolates might belong to gsA. Two isolates assigned to R. hidalgonense and another two non-nodulating strains could not be assigned to any validly defined species and possibly belong to a new rhizobial lineage. Interestingly, R. laguerreae strains were commonly found at all sampling sites, suggesting that they could be the main symbionts of faba beans in Greek soils. According to the phylogenies of two symbiosis-related genes (nodC and nifH), all nodulating isolates belonged to symbiovar (sv.) viciae harboring four distinct nodC gene haplotypes and they were grouped into two clades together with strains assigned to R. laguerreae and genospecies of R. leguminosarum isolated from other countries and continents. This is the first report that R. hidalgonense strains belong to sv. viciae. No correlation was observed between the nodC haplotypes, geographic origin and chromosomal background of the isolates in the study.

Investigation of the presence of glyphosate and its major metabolite AMPA in Greek soils.

Glyphosate is a broad-spectrum, non-selective, post-emergence herbicide that controls weeds by inhibiting their ability to synthesize amino acids. It is characterized by high persistence and adsorption to soil, with its dissipation to be highly correlated to the climatic conditions. After its degradationin soil, aminomethylphosphonic acid (AMPA) is the sole and major metabolite produced, characterized also by high persistence and adsorption. Both substances have the potential to remain in soil rather than move to other environmental compartments. Considering the recent intense debate during the EU renewal of glyphosate along with its wide use, it is apparent that both glyphosate and AMPA require further attention and information on their occurrence and distribution in EU soils. The present study does constitute the first extended soil monitoring survey of glyphosate and AMPA with samples derived during the years 2013-2015, from the highest extent of the Greek territory. Specific attention was given to areas of high agricultural production as well as to urban areas, since glyphosate-containing products are also registered for non-professional uses. The positive samples represented the 36.7% for glyphosate and 44.9% for AMPA, while the detected residues fluctuated from 0.026 to 40.6μgg-1 and from 0.01 to 2.5μgg-1 for glyphosate and AMPA, respectively. Our findings can constitute a basis for the determination of the background concentration levels of glyphosate and its metabolite in the Greek territory. As such, apart from being the first study for glyphosate monitoring in Greece, the most significant highlights recognized in the present work are the following:The high levels of glyphosate and AMPA residues in urban areas that indicate possible misuse of pesticidesThe generally low detection in the main agricultural basins and particularly near water recipientsThe fact that a potential for misuse of herbicides cannot be excluded even in the case of agricultural areas (considering that the maximum detection was in an olive grove and exceeded the model-predicted concentrations by 13 times).

Peak Friction Angle of Soils as a Function of Grain Size

Numerous studies have attempted to correlate geotechnical properties and to produce semi-empirical methods for estimating geotechnical parameters when sufficient field or laboratory measurements are not available. In the case of Greek soil formations, several studies have been presented that relate in situ tests (standard penetration test, cross-hole, seismocone) and laboratory tests for cohesive soils. Statistical analysis of the data resulted in the formulation of empirical correlations between various soil parameters, often with reasonably high correlation coefficients. However, these relationships refer mainly to cohesive soils, because the majority of tests were carried out in such formations. In this paper, the correlation of the particle size and the peak friction angle for a wide range of Greek soil formations is investigated. A simple, but rational approach for estimating the friction angle is presented, which allows prediction of the shear strength of soil formations. Since this investigation covered a wide range of soils and the number of test results is significant, the obtained empirical correlations can be considered as reliable for Greek soils.

Determination of Soil-Available Micronutrients using the DTPA and Mehlich 3 Methods for Greek Soils Having Variable Amounts of Calcium Carbonate

The Mehlich 3 method for the extraction of available micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), is more advantageous compared to the diethylene triamine pentaacetic acid (DTPA) method, because it can also be used for the extraction of macronutrients. The aim of this study was to compare the Mehlich 3 and DTPA methods for 172 soils in Greece having different levels of pH and calcium carbonate. Single and multiple regression analyses were employed to evaluate the relationship between Mehlich 3 and DTPA tests. Mehlich 3 results correlated well with DTPA-extractable Cu and Zn, but the correlation was poor for DTPA-extractable Mn. Also, a high correlation was found between Mehlich 3 and DTPA-extractable Fe for calcareous soils (R2 = 0.89), while a moderate relationship was found for noncalcareous soils (R2 = 0.65), which was improved to 0.78 when the pH was taken into account in multiple regression analysis.

Geochemistry of serpentine agricultural soil and associated groundwater chemistry and vegetation in the area of Atalanti, Greece

The soil geochemistry was studied in the area of Atalanti, Greece, an area characterized by presence of mafic and ultramafic rock members of an ophiolite complex. The objectives of the study were to evaluate their impact on soil chemistry and to establish the geochemical baseline of soil with respect to elements derived from the ophiolite rocks. A total of 118 agricultural soil samples were collected and found to be enriched in Ca (7.6%), Co (31mg/kg), Cr (230mg/kg), Cu (37mg/kg), Mg (2.9%) and Ni (330mg/kg) relative to the median values of both European and Greek soils. Soil baseline concentrations of the ophiolite derived elements (Cr, Ni, Co) were estimated within two sub-areas and the variation in their concentration was assessed along two toposequences characterized by different intensities of weathering of parent rock. Differences in groundwater chemistry were also demonstrated for the aquifers developing within the two subareas. The results of this study can be utilized in future studies on serpentine soil in temperate climate by providing an objective basis for setting realistic threshold values for pollution assessment and remediation.

Determination of Soil Available Phosphorus using the Olsen and Mehlich 3 Methods for Greek Soils Having Variable Amounts of Calcium Carbonate

The Mehlich 3 method for the determination of available phosphorus (P) is less laborious compared to the Olsen method and provides the advantage of multielement analysis. However, in Greece the Olsen P method is currently used because of its suitability for calcareous soils. The aims of this study were to compare (a) the Mehlich 3 and Olsen methods for 200 soils having different levels of pH and calcium carbonate and (b) Mehlich 3 colorimetric and Mehlich 3 inductively coupled plasma (ICP) analysis for 17 acidic and 23 alkaline soils. The correlation of Mehlich 3 P and Olsen P methods, excluding soils with pH less than 5 and soils with calcium carbonate levels from 10.3 to 48.3%, resulted in a linear slope of 0.24 and r2 of 0.82, and thus for this range of soils the Mehlich 3 test provided a more reliable measurement of P compared to the Olsen method. This study confirms also previous results that show that Mehlich 3 ICP test measures more P compared to Mehlich 3 colorimetry.

Environmental radioactivity measurements of Greek soils

Environmental radioactivity measurements of Greek soils

Fractionation of Cd, Cu, Ni, Pb, and Zn in floodplain soils from Egypt, Germany and Greece

Trace elements are potentially toxic to human life and the environment. Element toxicity depends on chemical associations in soils. Therefore, determining the chemical form of an element in soils is important to evaluate its mobility and bioavailability. Initial soil development in river floodplains influences soil properties, processes and therefore behavior of trace elements. In this study, three different floodplain soils sampled at three rivers (Nile/Egypt, Elbe/Germany and Penios/Greece) were used to link soil development and properties to the geochemical fractions and mobility of some trace elements. Sequential extraction was used to fractionate five trace elements (Cd, Cu, Ni, Pb and Zn) into five operationally defined groups: water soluble + exchangeable, carbonate, Fe-Mn oxide, organic, and residual. German soil showed the highest total concentration of the studied elements (except Ni). The Greek soil had the greatest amount of Ni. The residual fraction was the abundant pool for the studied elements examined in the Egyptian and Greek soils while the non-residual fraction was the dominant pool for all elements in the German soil. A significant amount (71- 94%) of all elements was present in German soil in the potentially available fraction: non-residual fraction, while the amount of this fraction ranged between 9 and 39 % in Greek soil and between 9 and 34 % in Egyptian soil. These suggest that the potential availability of the studied trace elements was extremely high in German soil compared to the Egyptian and Greek soil. In the German soil, most of the non-residual Cd, Ni and Zn were bounded with the Fe-Mn oxide fraction, while Cu and Pb distributed in the organic fraction. While in the Egyptian and Greek soils Fe-Mn oxide fraction was the abundant pool for the studied elements except for Cd, in which the exchangeable and the carbonate fractions had the greatest amount of Cd. Assuming that mobility and bioavailability of these elements are related to their solubility and geochemical forms, and that they decrease in the order of extraction sequence, the apparent mobility and potential bioavailability for the studied elements in the soils were: Cu > Cd > Ni ≥ Pb = Zn in Egyptian soil, Cd > Cu > Pb> Ni = Zn in Greek soil and Cd > Zn> Pb> Cu > Ni in German soil.

Phosphorus Removal from Aqueous Solutions and Greek Soils using Modified Natural Minerals and Its Impact on the Morphological Characteristics of Crops

In the present article, adsorption experiments of phosphate ions from their aqueous solutions were conducted with the use of five different materials (zeolite, bentonite, goethite, and systems I and II). The adsorption of phosphate ions were examined after mixing 2 g of each of these materials with 10 different phosphate concentrations (1.6, 3.2, 4.8, 6.5, 32.3, 193.5, 322.6, 483.9, 645.2, and 871.0 μmol L−1). The experimental equilibrium adsorption data were analyzed using the Langmuir, Freundlich, and Temkin equations. Results indicate the following order to fit the isotherms equations: Freundlich > Temkin > Langmuir. Moreover, the five materials were used as soil amendments to soils that were cultivated with wheat, maize, and cotton. Forty days after germination, the plants were collected, the morphological characteristics were identified, and the available phosphorus in soil and the total phosphorus in plants were determined. Comparing the experimental results, goethite and system I present the best impact in the root length, leaf area index, and dry weight of each plant. The adsorbed amount of phosphorus per g of dry weight of plants increases as follows: bentonite < system I < zeolite < system II < goethite (for wheat), goethite < system II < zeolite < bentonite < system I (for cotton), and system I < system II < bentonite < zeolite < goethite (for maize). Maize can be cultivated to soils contaminated with phosphorus with the simultaneous use of system I or II as soil amendments. Wheat can be used as phytoaccumulator crop for the phytoremediation of soils contaminated with phosphorus.

Microbial arsenic reduction in polluted and unpolluted soils from Attica, Greece

Indigenous soil microorganisms often affect the mobility of heavy metals and metalloids by altering their oxidation state. Under anaerobic conditions, the microbial transformation is usually reduction and may cause the mobilization of contaminants, as happens in the case of arsenic, which is much more stable in the pentavalent state compared to the reduced trivalent form. The aim of this work was to investigate the occurrence of such a microbial activity in representative Greek soils. Five soil samples, with As levels varying between 14 and 259mg/kg, were examined. The samples were artificially contaminated, by adding 750mg of As(V) per kg of soil. Initial sorption of As(V) ranged between 70 and 85%. Microbial reduction of arsenic was observed in three of the examined soils, without any obvious correlation with pre-existing levels of contamination. Reduction reached high percentages, i.e. up to 99%, and was accompanied by the corresponding release of reduced As in the aqueous solution. A simultaneous iron reducing activity was also observed in four of the five soil samples.

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.

Sorption of the antiparasitic drug eprinomectin in three soils

Batch equilibrium studies were conducted to determine eprinomectin partitioning behavior in three Greek soils (agricultural, pastoral and riparian soil). An analytical method was developed to quantify eprinomectin in aqueous 0.01 M CaCl 2. Recovery was 95% and limits of detection and quantification were both 0.005 mg L −1. An existing method for its quantification in soil was successfully tested in this study. Mass balance determinations showed that we accounted for 89–98% of the eprinomectin spiked in 5 g soil/25 mL 0.01 M CaCl 2. The concentration specific adsorption distribution coefficient ( K d ads ) ranged from 6.4 to 21.4 L kg −1 while concentration specific desorption distribution coefficient ( K d des ) ranged from 23.2 to 124.6 L kg −1. The Freundlich model adequately described adsorption and desorption with n values from 0.6 to 1.07. Hysteresis between adsorption and desorption was observed in two (agricultural and pastoral) soils. Moreover, eprinomectin binding to the clay mineral vermiculite and natural peat was tested. The drug binds to both materials. Hydroxyl groups and the nitrogen group present in eprinomectin are probably responsible for the binding to vermiculite. Coefficient K d ads significantly correlated with cation exchange capacity (CEC), Fe and Cu content of the soils when data for eprinomectin and data for ivermectin and abamectin were combined. These could be evidence that eprinomectin fate is related not only to organic matter (lipophilic binding) but also to clay content and other charged inorganic groups typically present in the soil environment.

Distribution of Total and Ammonium Bicarbonate-DTPA-Extractable Soil Vanadium From Greece and Egypt and Their Correlation To Soil Properties

Vanadium (V) is a trace element involved in soil pollution, originating from either soil parent material or anthropogenic sources. The aim of this study was to investigate the distribution of total and ammonium bicarbonateYDTPAYextractable (AB-DTPA) V in soil pro- files of representative Greek and Egyptian soils and their relationships to soil properties. Twenty-one soil profiles from Egypt and Greece (re- presenting the main soil orders, that is, Entisols (developed on fluvial, lacustrine, and marine deposits) and Aridisols for Egyptian soils and to the soil orders Entisols, Alfisols, Inceptisols, Vertisols, Mollisols, and Histosols for Greek soils) were sampled and analyzed for total and AB- DTPAYextractable V, and the relationship of V levels to soil properties were examined. Total V concentrations ranged from 23 mg kg j1 in the marine de- posits to 179 mg kg j1 in the lacustrine deposits. Total V levels signifi- cantly positively correlated to clay and silt content, cation exchange capacity, and free iron and manganese oxides and were negatively cor- related to sand, organic matter, and calcium carbonate content. The AB-DTPAYextractable V varied from 0.55 mg kg j1 in the Greek Entisol to 4.4 mg kg Y1 in the Egyptian lacustrine deposits and were signifi- cantly positively correlated with total V concentration, soil pH, clay and silt content, and cation exchange capacity (positively) and nega- tively correlated with sand content. Distribution of total and AB-DTPAY extractable V related mainly to particle size distribution, sesquioxides content, and soil pH. These results suggest that V could be a concern for many of the soils studied because in a large number of samples, V concentration values exceeded the international regulatory standards for remediation.

Adsorption-desorption study of bromophos methyl and quinalphos in Greek soils

The adsorption and desorption of bromophos methyl [O, O-dimethyl–O-(2, 5-dichloro-4 bromophenyl) phosphorothioate] and quinalphos [O, O-diethyl O-2-quinoxalinyl phosphorothioate] on five soils from different Greek locations with varying physical and chemical properties was studied by batch equilibration method. Adsorption isotherms fitted well to the Freundlich equation. The adsorption capacity of the soils for bromophos methyl was higher than quinalphos. Freundlich adsorption coefficient (Kfads ), showed significant correlation with soil organic matter, indicating that soil organic matter content was the main controlling factor for the adsorption of these pesticides on the soils. Desorption isotherms also conformed well to the Freundlich equation and there was a hysteresis effect in all the soils. The Freundlich Kfdes values were also higher for the soils with the highest organic matter per cent.

Adsorption and desorption processes of the organophosphorus pesticides, dimethoate and fenthion, onto three Greek agricultural soils

Laboratory studies were conducted to determine the sorption and desorption behaviour of two commonly used organophosphorus pesticides dimethoate and fenthion, which are widely used in the studied area to treat the olivetrees. Three Greek soils from the region of Mytilene island (denoted M, KT and P) which differed with respect to pH (pH 5.45–6.90), clay content (6–26%), organic matter content (1.0–4.2%), cation exchange capacity (4.8–24.4 meq/100 g) and specific surface (10.79–109.22 m2 g−1) were selected for the experimental section that was conducted using the batch equilibrium technique. The sorption isotherms could be described by Freundlich and Langmuir equations for both compounds with correlation regression coefficients for fit of the isotherms to that models R 2 ≥ 0.9666 and R 2 ≥ 0.8117, respectively. Freundlich sorption coefficients Kf were normalised to soil organic matter content and KOM estimated values for M, KT and P soils respectively were 60.19, 163.58 and 663.43 for dimethoate and 1365.84, 820.73 and 2902.52 for fenthion. Desorption studies revealed that dimethoate was adsorbed very weakly on soils tested and easily desorbed with water, while on the contrary fenthion was adsorbed very strongly on studied matrices with acetone extractable amounts.

Effect of Dissolved Organic Carbon on Zinc Solubility in Incubated Biosolids‐Amended Soils

Soil organic carbon (SOC) and dissolved organic carbon (DOC) affect long-term heavy metal solubility in biosolids-amended soils, but their role needs to be further studied under Mediterranean climatic conditions. We investigated Zn solubility, as assessed by water extraction, in two typical Greek soils amended with biosolids at 0, 20, and 100 Mg ha(-1) during a 310-d incubation period. It was found that SOC decreased by nearly 30% over time in the 100 Mg ha(-1) treatment. There was evidence that DOC affected Zn solubility, because DOC increased significantly on Day 23, probably due to a flush in microbial activity, and water-extractable Zn followed the same trend. After that, both DOC and water-extractable Zn decreased back to values similar to those of the unamended soils. Although Zn solubility did not increase overall even at high biosolids application rates, this study shows that time-limited fluctuations in Zn solubility due to sudden DOC flushes, can be significant, and need to be further investigated.

Influence of Different Cultivation Practices on the Properties of Volcanic Soils on Santorini Island, Greece

The influence of cultivation practice on the fertility of volcanic soils on Santorini, an important wine‐producing area of Greece, has been examined. In conventional agriculture, weed control, typically of N‐fixing species, is carried out using herbicides, whereas in organic practice it is achieved though plowing, leaving the soil vulnerable to erosion. Soil samples were taken from conventionally and organically cultivated vines and tomatoes and from abandoned vineyards at five locations. Biological indicators of soil quality were measured in addition to physicochemical properties. The loam sandy soils had an acid to slightly alkaline pH reaction, with low organic matter. Earthworms (Lumbricidae) were not found. Enchytreids were absent from conventional soils but were found in low abundance in organic and abandoned vineyard systems. Enzyme activity showed no dependence on cultivation systems but was low compared with other Greek soils. Organic practices adopted on Santorini have maintained soil fertility in the short term.

Interrill erosion on cultivated Greek soils: modelling sediment delivery

AbstractFor interrill erosion, raindrop‐induced detachment and transport of sediment by rainfall‐disturbed sheet flow are the predominant processes, while detachment by sheet flow and transport by raindrop impact are negligible. In general, interrill subprocesses are inter‐actively affected by rainfall, soil and surface properties. The objective of this work was to study the relationships among interrill runoff and sediment loss and some selected para‐meters, for cultivated soils in central Greece, and also the development of a formula for predicting single storm sediment delivery. Runoff and soil loss measurement field experiments have been conducted for a 3·5‐year period, under natural storms. The soils studied were developed on Tertiary calcareous materials and Quaternary alluvial deposits and were textured from sandy loam to clay. The second group of soils showed greater susceptibility to sealing and erosion than the first group. Single storm sediment loss was mainly affected by rain and runoff erosivity, being significantly correlated with rain kinetic energy (r = 0·64***), its maximum 30‐minute intensity (r = 0·64***) and runoff amount (r = 0·56***). Runoff had the greatest correlation with rain kinetic energy (r = 0·64***). A complementary effect on soil loss was detected between rain kinetic energy and its maximum 30‐minute intensity. The same was true for rain kinetic energy and topsoil aggregate instability, on surface seal formation and thus on infiltration characteristics and overland flow rate. Empirical analysis showed that the following formula can be used for the successful prediction of sediment delivery (Di): Di = 0·638βEI30tan(θ) (R2 = 0·893***), where β is a topsoil aggregate instability index, E the rain kinetic energy, I30 the maximum 30‐minute rain intensity and θ the slope angle. It describes soil erodibility using a topsoil aggregate instability index, which can be determined easily by a simple laboratory technique, and runoff through the product of this index and rain kinetic energy. Copyright © 2006 John Wiley &amp; Sons, Ltd.