Production of male neonates in Daphnia magna (Cladocera, Crustacea) exposed to juvenile hormones and their analogs

We exposed the water flea Daphnia magna (Cladocera, Crustacea) to either juvenile hormone I (JH I), juvenile hormone II (JH II), or the juvenile hormone-mimicking insecticides kinoprene, hydroprene, epofenonane, or fenoxycarb. By 21-day reproduction tests, we investigated the effects on the number of neonates born per female and the offspring sex ratio. All six chemicals induced D. magna to produce male neonates; the male sex ratio of the offspring increased as the chemical concentration increased. EC50 values for production of male neonates were estimated as 400 (JH I), 410 (JH II), 190 (kinoprene), 2.9 (hydroprene), 64 (epofenonane), and 0.92 (fenoxycarb) microg/l. The number of neonates produced was reduced with all chemicals at the concentrations investigated. At the EC50 for male production, five of the six chemicals reduced the reproductive rate to less than 50%; the exception was epofenonane, which caused only a slight reduction in reproductive rate. These results were similar to those obtained for five juvenoids studied previously, one of which was studied here again. There are now 10 chemical substances--all juvenile hormones or their analogs-that are known to induce D. magna to produce male neonates. This suggests that juvenile hormone is involved in initiating male production followed by sexual reproduction in D. magna, and probably in most cladocerans that exhibit cyclic parthenogenesis.     

A study on As, Cu, Pb and Zn (bio)availability in an abandoned mine area (São Domingos, Portugal) using chemical and ecotoxicological tools

The aim of this study was to relate the results obtained by chemical methods, used to assess environmental (bio)availability, with the ecotoxic response and bioaccumulation of trace elements (TE) by the earthworm Eisenia fetida exposed to field-contaminated, metal-polluted soils from a sulphide mine. The extracting solution 0.5 M NH₄CH₃COO, 0.5 M CH₃COOH and 0.02 M EDTA (pH 4.7), was able to predict environmental bioavailability of TE to E. fetida. However, the toxicological bioavailability could not be predicted from the results of the chemical extractions or from the bioaccumulation results: E. fetida reproduction was higher in soils where environmental bioavailability of TE and bioaccumulation values were also higher. In this study, the toxic response of the organism seemed to be more influenced by the overall nutritional status of the soil (e.g. pH, organic matter, plant nutrient availability and cation exchange capacity) than by its TE contamination. In the case of anthropogenic multi-contaminated sites, the different soil characteristics exert an important and confounding influence in the toxic response and the relationship between different bioavailable fractions cannot be easily established, emphasising the need to combine results from chemical methods with those from bioassays when evaluating the bioavailability of TE in these soils.     

Ecotoxicological evaluation of in situ bioremediation of soils contaminated by the explosive 2,4,6-trinitrotoluene (TNT)

To evaluate the environmental relevance of in situ bioremediation of contaminated soils, effective and reliable monitoring approaches are of special importance. The presented study was conducted as part of a research project investigating in situ bioremediation of topsoils contaminated by the explosive 2,4,6-trinitrotoluene (TNT). Changes in soil toxicity within different experimental fields at a former ordnance factory were evaluated using a battery of five bioassays (plant growth, Collembola reproduction, soil respiration, luminescent bacteria acute toxicity and mutagenicity test) in combination to chemical contaminant analysis. Resulting data reveal clear differences in sensitivities between methods with the luminescent bacteria assay performed with soil leachates as most sensitive toxicity indicator. Complete test battery results are presented in so-called soil toxicity profiles to visualise and facilitate the interpretation of data. Both biological and chemical monitoring results indicate a reduction of soil toxicity within 17 months of remediation.     

Evaluation of the toxicity of two soils from Jales Mine (Portugal) using aquatic bioassays

Soil contamination can be one path for streams and groundwater contamination. As a complement of chemical analysis and total contaminants determination, bioassays can provide information on the bioavailable fraction of chemical compounds, focusing on the retention and habitat function of soils. In this study the evaluation of the toxicity of two soils from the abandoned Jales Mine (Portugal) regarded both functions. The buffer capacity of soils was tested with bioassays carried out using the cladoceran Daphnia magna and the marine bacteria Vibrio fischeri. The habitat function of soils was evaluated with the reproduction bioassay with the collembolan Folsomia candida. The Microtox solid-phase test was performed with V. fischeri using soil as test medium, and soil elutriates were extracted to perform the Microtox basic test, and an immobilization and reproduction bioassay with D. magna. The marine bacteria showed high sensitivity to the soil with low heavy metal content (JNC soil) and to JNC soil elutriates, while the soil with highest heavy metal content (JC soil) or soil elutriates exposure did not cause any toxic effect. In the bioassays with D. magna, organisms showed sensitivity to JNC and also to JC soil elutriates. Both mobilization and reproduction features were inhibited. The bioassay with F. candida did not reflect any influence of the contaminants on their reproduction. Although JNC soil presented lower heavy metal contents, elutriates showed different patterns of contamination when compared to JC soil and elutriates, which indicates different retention and buffer capacities between soils. Results obtained in this study underlined the sensitivity and importance of soil elutriate bioassays with aquatic organisms in the evaluation strategy in soil ERA processes.     

Reproduction and biochemical responses in Enchytraeus albidus (Oligochaeta) to zinc or cadmium exposures

To better understand chemical modes of action, emphasis has been given to stress responses at lower levels of biological organization. Cholinesterases and antioxidant defenses are among the most used biomarkers due to their crucial role in the neurocholinergic transmission and in cell homeostasis preventing DNA damage, enzymatic inactivation and lipid peroxidation. The main goal of this study was to investigate the effects of zinc and cadmium on survival and reproduction of E. albidus and to assess metals oxidative stress potential and neurotoxic effects at concentrations that affected reproduction. Both metals affected the enchytraeids’ survival and reproduction and induced significant changes in the antioxidant defenses as well as increased lipid peroxidation, indicating oxidative damage. This study demonstrates that determining effects at different levels of biological organization can give better information on the physiological responses of enchytraeids in metal contamination events and further unravel the mechanistic processes dealing with metal stress.     

Seasonal variability of total and easily leachable element contents in topsoils (0-5 cm) from eight catchments in the European Arctic (Finland, Norway and Russia)

Frozen topsoil samples (0-5 cm) were collected during March/April 1994 in eight Arctic catchments in northern Europe (4 in Russia, 3 in Finland, 1 in Norway) at varying distances and wind directions from the emissions of the Russian nickel ore mining, roasting and smelting industry on the Kola Peninsula. Between 14 and 25 sites were sampled in catchment basins ranging in size from 12 to 35 km(2). Sampling was repeated in spring immediately after the snow melted, in summer and in autumn to study seasonal variability and the fate of elements when the snow melts. The <2 mm fraction of air-dried topsoils was analysed for total (aqua regia extraction) and easily leachable (in 1 m ammonium acetate, buffered at pH 4.5) element concentrations using ICP-AES and GFAAS for up to 35 elements. Results for selected elements are presented here. Soil organic matter can be shown to be the controlling factor determining element contents and fate. In catchments close to the Russian nickel industry, the topsoils have low carbon and nitrogen contents. Using both extraction methods most elements reach maximum concentrations in winter; lowest concentrations are observed in midsummer. Soil organic matter and elements associated with it are thus leached out of the soils together with soluble elements when the snow melts. This process continues in summer. Elements will enrich surface waters, the lower layers of podzol profiles, or reach the groundwater. The use of the two extractions described provides a simple method to study the mobilities and pathways of elements in the topsoils during the arctic year. Using the proportions of easily leachable to total concentration, a good estimation of the status of the topsoil in the study area can be given.     

Estimating K(oc) for persistent organic pollutants: limitations of correlations with K(ow)

The n-octanol/water partition coefficient (K(ow)) is commonly used to predict the soil or aquatic particle water partition coefficient normalized to organic carbon (K(oc)). Many correlations are available covering several chemical classes and ranges of hydrophobicity. This work indicates the K(ow) may not be a strong predictor for persistent organic pollutants (POPs) which are defined here as chemicals with logK(ow) > 5.0. In addition, the correlation developed in this work for POPs will still result in a predicted value which is of by a factor of 15. Accordingly, care must be taken when applying K(oc) estimations using K(ow) for POPs until more suitable correlations are developed.     

有机化合物动态定量结构——生物降解关系(QSBR)模型研究

本文通过分析一般ＱＳＢＲ模型应用的特点、不足和影响有机物生物降解的基本因素，指出ＱＳＢＲ模型应综合反映影响有机物生物降解的四个方面（以氯代芳香化合物为例）：氯代苯系物的摄入、氯代苯系物的诱导作用、毒性物质的形成和基础酶的缺乏。在此基础之上给出了动态ＱＳＢＲ的概念模式及方法学基础。     

Sulphur in the Arctic environment (3): environmental impact

Long term, high level airborne emissions of pollutants from nickel industries on the Kola Peninsula (NW Russia) have resulted in widespread ecosystem injury up to almost complete vegetation eradication within nearest surroundings of the smelters. Although SO2 is the prevailing component of the emissions, it is only part of a much more complex chemical emission spectrum in the region. In addition to acidic gases, industry also emits potentially toxic elements (e.g. metals) which being less volatile than SO2, are deposited within the immediate region in significant concentrations. Additionally, it appears that sources of base cations (co-emission by smelters, sea aerosols, other industries) are adequate to prevent environmental acidification on the regional scale. Acidification of soils and waters appeared only as single cases in the immediate vicinity of the smelters and is not believed to be a major mechanism of environmental deterioration. Proposed critical concentrations (5 microg/m(3)) of SO2 for the northern ecosystems are exceeded over a large area and direct exposure to SO2 is believed to be the possible mechanism of vegetation damage.     

Sense or no-sense of the sum parameter for water soluble "adsorbable organic halogens" (AOX) and "absorbed organic halogens" (AOX-S18) for the assessment of organohalogens in sludges and sediments

"AOX" is the abbreviation of the sum parameter for water soluble "adsorbable organic halogens" in which 'A' stands for adsorbable, 'O' for organic and 'X' for the halogens chlorine, bromine and iodine.After the introduction of the AOX in 1976, this parameter has been correctly used for "real" AOX constituents (DDT and its metabolites, PCBs, etc.) but also misused for non-adsorbable adsorbed OX-compounds, mostly high molecular organohalogens in plants and even to inorganic compounds being neither organic nor adsorbable.The question of natural "Adsorbable Organic Halogens" (AOX) formed by living organisms and/or during natural abiogenic processes has been definitively solved by the known existence of already more than 3650 organohalogen compounds, amongst them the highly reactive, cancerogenic vinyl chloride (VC).The extension of the AOX to AOX-S18 for Sludges and Sediments, in which A stands for adsorbed (not for adsorbable) is questionable. It includes the most important water insoluble technical organochlorine product: polyvinyl chloride, PVC.In addition to organic halogens it also includes inorganic, mineralogenic halides, incorporated mainly in the crystal lattice of fine grained phyllosilicates, the typical clay minerals (kaolinite, montmorillonite, illite and chlorite) which are main constituents of sediments and sedimentary rocks representing the major part of the sedimentary cover of the earth.Other phyllosilicates, biotite and muscovite, major constituents of granites and many metamorphic rocks (gneiss and mica schist) will also contribute to the AOX-S18 especially in soils as result of weathering processes.Since chlorine is incorporated into the mineral structure and, as a consequence, not soluble by the nitric acid analytical step (pH 0.5) of the S18 determination, it will account to the AOX-S18 in the final charcoal combustion step at temperatures >950 degrees C.After heavy rainfalls sewage sludge composition is strongly influenced by mineralogenic components derived from the erosion of fine grained sediments or soils. Assuming 50% geogenic particles with a mean Cl concentration of 103 mg/kg (as in shales and clays) the mineralogenic Cl-content could add about 50 mg/kg to the organic AOX in sewage sludge.The occurrence of insoluble and non-adsorbable PVC in sewage sludge exhibits the same problems as the mineralogenic constituents: a detection as AOX-S18 is possible when the final high temperature analytical step is applied.Plants as major sources of organohalogens have never been doubted.Only recently [Science 295 (2002) 985] based on the determination of the form of Cl with near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy and extended X-ray adsorption showed the variations in the inorganic Cl(-) and organo-Cl compounds with increasing humification of plant leaves from "fresh leaves--senescent leaves on plants--senescent leaves on soil--powdered top soil--isolated soil humus". His finding of exclusively inorganic Cl(-) in the starting material (fresh leaves) is controverse to our earlier results indicating the presence of ionic inorganic Cl together with water insoluble absorbed organohalogens (AOX-S18) in eight different macrophytes of both terrestrial and marine environments.Our research on AOX in interstitial water of anaerobic limnic sediments has led to the role of bromine playing in the diagenesis of the organic matter of sediments. In sediments of Lake Constance Br(-) concentrations in lake water at the sediment water interface increased from <0.01 to 0.25 mg/l in the pore water at 77 cm sediment depth.In the Neckar River a Br concentrations of 0.02 mg/l at the water/sediment interface increasing to 0.74 mg/l in pore water in 85 cm depth was found. Here a parallel development could be found with ammonium concentration and alkalinity. The very high positive correlation ammonium:bromide and bromide:alkalinity leads to the conclusion, that bromine, originally a high molecular constituent of the organic matter, is released as bromide during an early dehalogenation stage of diagenesis.The mlusion, that bromine, originally a high molecular constituent of the organic matter, is released as bromide during an early dehalogenation stage of diagenesis.The main general reason to discard the AOX sum parameter as a whole lies in the fact, that adsorbable halogenated substances cannot a priori be categorized as natural/anthropogenic, biotic/abiotic, harmful/harmless. If applied to sludges and sediments, adsorbed organohalogens are not water soluble and therefore not adsorbable, and mineralogenic halogens (X) are neither organic nor adsorbable, and therefore by definition no AOX.     

Chemical recycling of poly(ethylene terephthalate) (pet) by hydrolysis and glycolysis

In this paper we review an interesting method of PET recycling, i.e. chemical recycling; it is based on the concept of depolymerizing the condensation polymer through solvolytic chain cleavage into low molecular products which can be purified and reused as raw materials for the production of high-quality chemical products. In this work our attention is confined to the hydrolysis (neutral, acid and alkaline) and glycolysis processes of PET chemical recycling; operating conditions and mechanism of each method are reported and described. The neutral hydrolysis has an auto accelerating character; two kinetic models have been proposed: an half-order and a second order kinetic model. The acid hydrolysis could be explained by a modified shrinking core model under chemical reaction control and the alkaline hydrolysis by a first-order model with respect to hydroxide ion concentration. To describe glycolysis, two different kinetic models have been proposed where EG can act or not as internal catalyst. Further experimental and theoretical investigations are required to shed light on the promising processes of PET chemical recycling reviewed in this work.     

Topsoil (0-5 cm) composition in eight arctic catchments in northern Europe (Finland, Norway and Russia)

Frozen topsoil samples (0-5 cm) were collected during March/April 1994 in eight Arctic catchments in northern Europe (four in Russia, three in Finland, one in Norway), at different distances and in different wind directions from the emissions of the Russian mining, roasting and smelting industry on the Kola Peninsula. Between 14 and 25 sites were sampled in each of the eight catchments ranging in size from 12 to 35 km2. Results show that close to the smelters in Monchegorsk and Nikel, topsoil is clearly enriched in Ag, As, Bi, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sb, Se, Te and V. Cu and Ni median contents in topsoils collected close to Monchegorsk are about 600 times higher than in the Finnish catchments. The effect of open-cast mining and waste dumps of alkaline rocks from the nephelinite industry near Kirovsk can be seen in the elevated contents of Al, Ba, K, La, Mn, Na, Sr, Ti, Y and Zn in topsoil collected in a nearby catchment. For many elements, however, variations observed in single catchments are as great as the total regional variation. Several elements (e.g. Cd, Hg, Cu, Ni, Pb, S, Zn) show strong positive correlation between the organic content of the sample and the element content observed. Thus it is necessary to determine the organic content of the samples and correct the element levels when using depth-related soil samples (here, the 0-5 cm topsoil layer) for regional mapping.     

Pattern recognition and classification of sediments according to their metal content using chemometric tools. A case study: the estuary of Nerbioi-Ibaizabal River (Bilbao, Basque Country)

Chemometrics are increasingly used in environmental monitoring studies, but are still far from being accepted as routine tools by field specialists. The multivariate character of usually highly correlated environmental data recommends the use of advanced chemometrics as part of the analytical methodology in order to get information on the basic structure of data. In this work, we have applied a battery of non-supervised (Principal Component Analysis (PCA)) and supervised (k-Nearest Neighbour (k-NN), Soft Independent Modelling of Class Analogies (SIMCA), Linear Discriminant Analysis (LDA) and Artificial Neural Networks (ANNs)) multivariate techniques on a specific environmental dataset. The dataset consists on the concentration of 14 elements (Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn) in 95 sediments collected at eight different locations of the estuary of the Nerbioi-Ibaizabal River (Bilbao, Basque Country) during 12 sampling campaigns conducted every 3 months between 2005 and 2008. The study aims to present a simple methodology of general applicability which may result in a flexible and practical tool to assess chemical pollution in sediments of a given specific site.     

Impact of biogenic terpene emissions from <Emphasis Type="Italic">Brassica napus</Emphasis> on tropospheric ozone over saxony (Germany)

INTRODUCTION: The role of biogenic emissions in tropospheric ozone production is currently under discussion and major aspects are not well understood yet. This study aims towards the estimation of the influence of biogenic emissions on tropospheric ozone concentrations over Saxony in general and of biogenic emissions from brassica napus in special. MODELLING TOOLS: The studies are performed by utilizing a coupled numerical modelling system consisting of the meteorological model METRAS and the chemistry transport model MUSCAT. For the chemical part, the Euro-RADM algorithm is used. EMISSIONS: Anthropogenic and biogenic emissions are taken into account. The anthropogenic emissions are introduced by an emission inventory. Biogenic emissions, VOC and NO, are calculated within the chemical transport model MUSCAT at each time step and in each grid cell depending on land use type and on the temperature. The emissions of hydrocarbons from forest areas as well as biogenic NO especially from agricultural grounds are considered. Also terpene emissions from brassica napus fields are estimated. SIMULATION SETUP AND METEOROLOGICAL CONDITIONS: The simulations were performed over an area with an extension of 160 x 140 km2 which covers the main parts of Saxony and neighboring areas of Brandenburg, Sachsen-Anhalt and Thuringia. Summer smog with high ozone concentrations can be expected during high pressure conditions on hot summer days. Typical meteorological conditions for such cases were introduced in an conceptual way. RESULTS: It is estimated that biogenic emissions change tropospheric ozone concentrations in a noticeable way (up to 15% to 20%) and, therefore, should not be neglected in studies about tropospheric ozone. Emissions from brassica napus do have a moderate potential to enhance tropospheric ozone concentrations, but emissions are still under consideration and, therefore, results vary to a high degree. CONCLUSIONS: Summing up, the effect of brassica napus terpene emissions on ozone concentrations is noticeable, but not too pronounced. The results give a preliminary estimate on what the effect due to brassica napus emissions could be until better parameterizations can be derived from measurements.     

Calculating pesticide sorption coefficients (Kd) using selected soil properties

Pesticide soil/solution distribution coefficients ( Kd values), commonly referred to as pesticide soil sorption values, are utilized in computer and decision aid models to predict soil mobility of the compounds. The values are specific for a given chemical in a given soil sample, normally taken from surface soil, a selected soil horizon, or at a specific soil depth, and are normally related to selected soil properties. Pesticide databases provide Kd values for each chemical, but the values vary widely depending on the soil sample on which the chemicals were tested. We have correlated Kd values reported in the literature with the reported soil properties for an assortment of pesticides in an attempt to improve the accuracy of a Kd value for a specific chemical in a soil with known soil properties. Mathematical equations were developed from regression equations for the related properties. Soil properties that were correlated included organic matter content, clay mineral content, and/or soil pH, depending on the chemical properties of the pesticide. Pesticide families for which Kd equations were developed for 57 pesticides include the following: Carboxy acid, amino sulfonyl acid, hydroxy acid, weakly basic compounds and nonionizable amide/anilide, carbamate, dinitroaniline, organochlorine, organophosphate, and phenylurea compounds. Mean Kd values for 32 additional pesticides, many of which had Kd values that were correlated with specific soil properties but for which no significant Kd equations could be developed are also included.     

Solid-state conformations and absolute configurations of (+) and (-) alpha-, beta-, and gamma-hexabromocyclododecanes (HBCDs)

Hexabromocyclododecanes (HBCDs) are high production volume chemicals used as flame retardants for plastics and textiles. They are currently produced in quantities exceeding 20,000 t/y. Despite this fact, the correct stereochemistry of most HBCDs is still not known. Six stereocenters are formed during bromination of cyclododecatrienes, resulting in mixtures of different stereoisomers. Considering all elements of symmetry, 16 different stereoisomers including six pairs of enantiomers as well as 4 meso forms are possible theoretically. Recently, we isolated 8 of the 16 possible stereoisomers from a technical HBCD mixture and assigned their relative configurations. Herein, we report on the isolation of 6 enantiomerically pure alpha-, beta-, and gamma-HBCDs, obtained from preparative chiral-phase liquid chromatography, and we present their absolute configurations, which were determined from X-ray diffraction analysis. The absolute configuration of (-) alpha-HBCD was found to be (1R,2R,5S,6R,9R,10S), while the one of (+) beta-HBCD is assigned to (1S,2S,5S,6R,9S,10R), whereas the one of (-) gamma-HBCD corresponds to (1S,2S,5S,6R,9R,10S). The given structural information allows the unambiguous identification of the six most important HBCD stereoisomers, which typically account for more than 95% of technical HBCDs. In addition, we compared the solid-state conformations of racemic and enantiomerically pure alpha-, beta-, and gamma-HBCDs. In all cases, vicinal dibromides adopted a synclinal (sc) conformation with torsion angles of 69+/-6 degrees. A unique structural motive was common to all examined HBCD solid-state conformations. This conserved structure was described as an extended triple turn consisting of an arrangement of three pairs of synclinal and two antiperiplanar torsion angles.     

Ice (photo)chemistry. Ice as a medium for long-term (photo)chemical transformations--environmental implications

This review accounts for the current knowledge about the distribution, accumulation, and chemical/photochemical transformations of persistent, bioaccumulative, and toxic compounds (PBTs) in water ice, especially in the connection with polar regions and atmospheric cloud particles. (Photo)reactions on/in ice are discussed in terms of photochemistry, photobiology, paleochemistry, as well as astrophysics. Authors propose a model, in which a significant amount of some PBTs are generated by (photo)chemistry of primary pollutants in ice, which may subsequently be released to the environment. It is argued that ice photochemistry might play an important role in the chemical transformations in cold ecosystems and in the upper atmosphere, particularly now when the ozone layer is partially depleted.     

Chronic toxicity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in soil determined using the earthworm (Eisenia andrei) reproduction test

The sublethal and chronic effects of the environmental contaminant and explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in artificial soil were assessed using the earthworm (Eisenia andrei). Based on various reproduction parameters (total and hatched number of cocoons, number of juveniles and their biomass), fecundity was reduced at the different concentrations of HMX tested (from 280.0 +/- 12.3 to 2502.9 +/- 230.0 mg kg-1 dry soil) in spiked artificial soil (LOEC: 280.0 +/- 12.3 mg kg-1 dry soil). The growth of adult E. andrei was also reduced at the different concentrations tested, though no mortality occurred, even at the highest tested concentrations. The number of juveniles produced was correlated with the number of total and hatched cocoons, and the biomass of juveniles was correlated with the number of cocoons. Pooled results of these and earlier studies on explosives (TNT, RDX) using the E. andrei reproduction test confirm that effects of HMX on cocoon production are indicative of some reproductive consequences (number of juvenile and their biomass), whereas adult growth, in general, does not correlate strongly with change in reproduction capacity.     

Contaminant-induced irreversible changes in properties of the soil-vadose-aquifer zone: an overview

Most studies on contaminant interactions with the subsurface environment focus on contaminant transport, retention and persistence, and on potential remediation of polluted soils, vadose zones and aquifers. Changes in the soil-vadose-aquifer zone (SVAZ) matrix and properties, caused by human activities, are thus usually considered to be deviations from a normal geochemical environment, which will disappear by natural processes or by specific remediation procedures. However, contaminants may also cause, under specific conditions, irreversible changes in SVAZ properties. In this critical overview, we discuss a different aspect of contaminant-SVAZ interactions: irreversible changes in natural SVAZ properties as a result of anthropogenically-induced chemical contamination. We survey selected research results that illustrate various aspects of such phenomena, in soils, aquifers and the vadose zone. Grouping contaminants according to major and trace elements, we observe that major elements can irreversibly affect water transmission and other physical and chemical properties of the SVAZ, mainly in the liquid phase, while trace elements affect mostly the solid phase matrix.     

Depleted uranium mobility and fractionation in contaminated soil (Southern Serbia)

GOAL, SCOPE AND BACKGROUND: During the Balkan conflict in 1999, soil in contaminated areas was enriched in depleted uranium (DU) isotopic signature, relative to the in-situ natural uranium present. After the military activities, most of kinetic DU penetrators or their fragments remained buried in the ground in certain geomorphological and geochemical environments exposed to local weathering conditions. The contamination distribution, mobility and/or fixation of DU in the contaminated soil profile at one hot spot were the subject of our study. The results should disclose what happened with released DU corrosion products in three years elapsed, given the scope of their geochemical fractionation, and mark out the most probable host substrates in investigated soil type. METHODS: Gamma-spectrometric analysis of soil samples taken in the DU penetrator impact-zone was done to obtain present contamination levels. Set of samples is subjected to five-step and three-step sequential extraction procedures, specifically selective to different physical/chemical associations in soil. The stable elements are determined in extracts by the atomic absorption spectroscopy. After the ion-exchange based uranium separation procedure, alpha-spectrometric analysis of obtained fractions was done and DU distribution in five extraction phases found from 235U/238U and 234U/238U isotopic ratios. RESULTS: Depleted uranium concentration falls down to the 1% of the initial value, at approximately 150 mm distance to the source. Carbonates and iron/manganese hydrous oxides are indicated as the most probable substrates for depleted uranium in the characterized soil type. Therefore, in the highly contaminated soil samples, depleted uranium is still weakly bonded and easy exchangeable. The significant levels of organic-bonded depleted uranium are found in surface soil only. DISCUSSION: Dependence of the fractionation on the contamination levels is evident. Samples with higher DU contents have shown a longer maintenance in the exchangeable phases, probably because adsorption/desorption mass transfer through the medium was not very fast. Organic-bonded, depleted uranium is present in surface soil samples due to its higher humus content. Considering geochemical composition of investigated soil, the indicating chemical associations as substrates are in agreement with some considerations based on the results for low-level waste unsaturated zones. CONCLUSIONS: The soil contamination with depleted uranium in investigated area is still 'spot' type and not widespread. Dependence of the fractionation on the contamination levels and presence of weakly bonded, depleted uranium in the hot spots areas is evident. RECOMMENDATIONS AND PERSPECTIVES: A detailed study may be undertaken with suitable extractive reagents to define a bio-available fraction of depleted uranium in soil. The comparison of results for different soil types investigated by the same methodology may be useful. An applied combination of physical/chemical procedures and analysis may help in the decision making on the remediation strategy for sites contaminated with depleted uranium used in military operations.