Translocation studies of 137Cs and 90Sr in bean plants (Phaseolus vulgaris): simulation of fallout

In case of an accident at a nuclear power plant with liberation of radioactive material into the atmosphere, knowledge about the behavior of plant species when in contact with radionuclides is indispensable for safety reasons. The leaf-fruit translocation is an important route through which agricultural products are contaminated by radionuclides. To quantify the leaf-fruit translocation factors for 137Cs and 90Sr in common beans (Phaseolus vulgaris) an experiment was carried out in a greenhouse with a randomized block design. 137Cs activity was determined by gamma-ray spectrometry, while chemical separation followed by beta counting of 90Y was used for 90Sr determination. The model applied for translocation indicated functional dependence between the moment of tracer application and the physiological development of the bean plant. Translocation factors obtained for 137Cs and 90Sr were 0.16 and less than 0.005, respectively.     

Lower variability of radionuclide activities in upland dairy products compared to soils and vegetation: implication for environmental survey

Contamination of the environment by radionuclides is usually estimated using soil and grass sampling. However, radionuclides are often not homogeneously distributed in soils. In the alpine Mercantour region (Western Alps, France) a large heterogeneity in Chernobyl 137Cs deposition has been previously observed. Here we report additional 137Cs results together with new 90Sr and Pu data for soil, grass, milk, and cheese samples. The results show that radioisotopes from nuclear weapons tests fallout are more homogeneously distributed than Chernobyl 137Cs. Further, we observe that the 137Cs and 90Sr contents are less variable in milk samples than in grass or soil samples. This can be attributed to the homogenization effect of cow vagrancy during grazing. Hence milk seems to be a more robust sample than soil or grass to evaluate the extent of contamination on a regional scale. We explore this idea by comparing own unpublished 90Sr results and 90Sr results from the literature to establish the relationship between altitude of grazing and contamination of soil and milk for Western Europe. There is a significant positive correlation between soil contamination and altitude and an even closer correlation between milk 90Sr activity (A) and altitude (h): A = A0 + e(k x h) where A0 is the expected activity of milk sampled at sea level (A0 = 0.064 +/- 0.014 Bq g(-1) Ca) and h is the altitude of grazing, k being a constant (k = 0.95 x 10(-3) +/- 0.11 x 10(-3) m(-1) Bq g(-1) Ca). The fact that there is less scattering in the relationship for the 90Sr(milk)-altitude than for 90Sr(soil)-altitude suggests, again, that milk is a well-suited sample for environmental survey. The relationship between the altitude of grazing and the 90Sr content of milk and cheese can also be used to assess the authenticity of dairy products.     

Phytoremediation of radiostrontium ((90)Sr) and radiocesium ((137)Cs) using giant milky weed (Calotropis gigantea R.Br.) plants

Potential of plants to remove radionuclides/toxic elements from soils and solutions can be successfully applied for removal of important radionuclides such as strontium-90 (⁹⁰Sr) and cesium-137 (¹³⁷Cs). When uptake of ¹³⁷Cs and ⁹⁰Sr by Calotropis gigantea plants incubated in distilled water spiked with the radionuclides either alone or in combination was studied, it was found to have a high efficiency for the removal of ⁹⁰Sr, with 90% being removed from solutions (5 × 10³ kBq l⁻¹) within 24 h of incubation. However, in case of ¹³⁷Cs, about 44% could be removed from solutions (5 × 10³ kBq l⁻¹) at the end of 168 h of incubation. Accumulation of ⁹⁰Sr and ¹³⁷Cs was higher in roots compared to shoots. The plants could remediate both ⁹⁰Sr and ¹³⁷Cs when they were added together to the solution. When two months old plants were incubated in low level nuclear waste, 99% of activity disappeared at the end of 15 days. The present study suggests that C. gigantea could be used as a potential candidate plant for phytoremediation of ⁹⁰Sr and ¹³⁷Cs.     

Irradiation of sorbents by ions of polymorphic metals for modeling <Superscript>90</Superscript>strontium sedimentation

Background, Aims and Scope Advances in radioecology can support improvements in environmental remediation technologies, especially by illuminating interaction processes between polymorphic metal radionuclides and various materials and their ions in aqueous solutions. This study modeled interaction processes of ⁹⁰Sr with transitive metals to delineate the behavior of polymorphic metal radionuclides. Experimental and modeling results confirmed Sr sedimentation was sensitive to the physical impact of radionuclides on various sorbents and possible chemical reactions occurring between the radionuclides and sorbents. Methods Models were developed to simulate ⁹⁰Sr sedimentation process, and the potential physical and chemical reactions accompanying the process. Models were verified, inorganic salts were used as sorbents to absorb metal cations, activity levels were recorded before and after mixing the inorganic salts while the efficiency of sedimentation using the heavy metals composites was quantified. Results and Discussion This research demonstrates that the process of the sedimentation is complex and occurs in several stages. Micro-structural analysis shows that zones of interaction between the sorbent and source metal are formed during the irradiation of the target’s metal surface. Electrical-microscopic analysis indicates that the composition of the formed zones of interaction of Ti (Sr) with target metals has various structures. Roentgenophase analysis indicates that the interaction of the ions of a precipitable source and a target occurs according to constitution diagrams of equilibrium systems. The results indicate that application of inorganic salts composites based on modeling increases the efficiency of the deactivation of aqueous solutions when compared to standard aluminum sulfate composite. Conclusions Experimental and modeling results confirm ⁹⁰Sr sedimentation is sensitive to the physical impact of radionuclides on various sorbents and possible chemical reactions occurring between the radionuclides and sorbents. The models support estimation of the physical impact of polymorphic metal radionuclides on various components of sorbents and possible chemical reactions occurring between the radionuclides and sorbents during the interaction. Inorganic salt composites deactivate and clear ⁹⁰Sr and Sr⁺² from water. This paper is openly accessible!     

Radionuclides in pinon pine (Pinus edulis) nuts from Los Alamos National Laboratory lands and the dose from consumption

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food--the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of 3H, 137Cs, 90Sr, totU, 238Pu, 239,240Pu, and 241Am in soils (0- to 12-in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of 3H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN fromLANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 microSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 microSv). Soil-to-nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Application of molluscs for radioecological monitoring of the Chernobyl outburst

Accumulation of radionuclides was studied in molluscs from the territories polluted by the Chernobyl outburst. In addition to radiochemical evaluation of (90)Sr, a simple method of beta-radiometry of shells was applied which allowed processing of extensive samples and mapping of contamination of large territories: the Dnieper drainage area and the Kiev administrative region. Pre-Hiroshima and pre-Chernobyl radioactivity was investigated in museum collections. Differences in (90)Sr accumulation in molluscs of different genera were demonstrated for freshwater and terrestrial snails, an especially high accumulation factor was found in Helix. Indices of relative accumulation were calculated treating Lymnaea stagnalis as a standard. All the measurements were recalculated to this standard in order to provide comparisons between sampling sites disregarding collected species and to reduce variance before mapping. Based on shell beta-activity measurements, the average accumulation factor for (90)Sr in Lymnaea compared to its concentration in the river water was about 5000, its transfer factor compared to the soil contamination was about 0.1 m(2) kg(-1), figures for (137)Cs were smaller by an order of magnitude. Inverse dependence between free calcium content in the environment and the transfer factor was demonstrated, as well as a difference in (90)Sr/(137)Cs ratio in molluscs collected on different tracks of Chernobyl pollution. Monitoring the biologically accessible and biologically active fraction of (90)Sr contamination, the shell beta-activity above 15 kBq kg(-1) indicates a dangerous level of contamination for the human population.     

A simplified approach to modelling underground migration of radionuclides from contaminated river sediments

Accidental releases of waste water from the first Czechoslovak nuclear power plant, A1, caused contamination of sediments of the Dudváh river, flowing into the Vah river, in Slovakia. Rather high concentrations of ¹³⁷Cs and ⁹⁰Sr (2150Bq dm⁻³ and 215Bq dm⁻³, respectively) were found in bottom sediments of a former channel of the re-engineered river body at a distance of about 250 m from a village, Siladice, with water-supply wells. In order to assess the possibility of contamination of the wells, underground migration of both radionuclides from the contaminated area was simulated using an original layered convection-diffusion model. K_d values determined in laboratory experiments were used. The analysis of the hydrological situation in the area reveals that the critical condition is a dominant horizontal groundwater flow near the water table in the direction from the Váh bank to Siladice, in the periods when the contaminated body lies under the water table. The simulation calculated under conservative conditions showed that the contamination of water-supply wells would not exceed permissible concentration limits.     

Plant uptake of radionuclides in lysimeter experiments

The results of seven years lysimeter experiments to determine the uptake of 60Co, 137Cs and 226Ra into agricultural crops (endive, maize, wheat, mustard, sugarbeet, potato, Faba bean, rye grass) are described. The lysimeter consists of twelve monolithic soil profiles (four soil types and three replicates) and is located in Seibersdorf/Austria, a region with a pannonian climate (pronounced differences between hot and semi-arid summers and humid winter conditions, annual mean of precipitation: 517 mm, mean annual temperature: 9.8 degrees C). Besides soil-to-plant transfer factors (TF), fluxes were calculated taking into account biomass production and growth time. Total median values of TF's (dry matter basis) for the three radionuclides decreased from 226Ra (0.068 kg kg(-1)) to 137Cs (0.043 kg kg(-1)) and 60Co (0.018 kg kg(-1)); flux values exhibited the same ranking. The varying physical and chemical properties of the four experimental soils resulted in statistically significant differences in transfer factors or fluxes between the investigated soils for 137Cs and 226Ra, but not for 60Co. Differences in transfer between plant species and plant parts are distinct, with graminaceous species showing, on average, TF values 5.8 and 15 times lower than dicotyledonous species for 137Cs and 60Co, respectively. This pattern was not found for 226Ra. It can be concluded that 137Cs transfer is heavily influenced by soil characteristics, whilst the plant-specific factors are the main source of TF variability for 60Co. The variability of 226Ra transfer originates both from soil properties and plant species behaviour.     

Possible change in Asian dust source suggested by atmospheric anthropogenic radionuclides during the 2000s

Decades-long monitoring of anthropogenic radionuclides in the atmospheric deposition in Tsukuba, Japan suggests not only the substantial impacts of the Asian dust (Kosa) on the deposition but also the possible change of the Kosa source region, especially during springs of the 2000s. In order to know more about such change, 4 single wet deposition events occurred in the spring of 2007 were scrutinized. The largest anthropogenic radionuclides wet deposition was supplied by the April 2–4 event. It brought several tens % of the monthly depositions (April 2007) of the dust (residue) mass (4.5 g m^?2) and anthropogenic radionulides (⁹⁰Sr: 16, ¹³⁷Cs: 97 and Pu: 3 mBq m^?2). None of the events observed fulfilled both criteria of the specific activities and ⁹⁰Sr/¹³⁷Cs activity ratio to the Tsukuba soil; they did not exhibit local soil dust signature. The Kosa events in fact have extensive impacts on the atmospheric environment over Japan in spring season. Considering the elevated specific activities as well as greater ¹³⁷Cs/⁹⁰Sr activity ratio in the deposited dust, it is hypothesized that the dust source areas in Asian continent would be shifting from the arid zone to the desert-steppe zone suffering from desertification during the 2000s. This type of the Kosa may be called as the ‘new-regime Kosa’. Chemical observation in the far downwind region of the Kosa dust could allow us to know possible shift in the source regions.     

Effect of ectomycorrhizae and ammonium on 134Cs and 85Sr uptake into Picea abies seedlings

Microorganisms play an important role in the fixation of radionuclides in forest soils. In particular, fungi have the capacity to absorb and translocate radionuclides. The role of the ectomycorrhizal fungus Hebeloma crustuliniforme in the uptake of radiocaesium (134Cs) and radiostrontium (85Sr) into seedlings of Norway spruce (Picea abies) was investigated in a pouch test system. Inoculated and non-inoculated seedlings; seedlings inoculated during 8 and 15 weeks; seedlings exposed during 2 and 3 weeks to the radioactive solution; and seedlings grown under low and high ammonium conditions prior to the application of the radionuclides were compared. The final 134Cs and 85Sr activity was determined in fine-roots, main-roots, stems and needles. The results showed that ectomycorrhizae reduced the uptake of 134Cs and 85Sr. The degree of ectomycorrhization was of crucial importance and seemed to be governed by the period during which ectomycorrhizae were allowed to develop and by the ammonium concentration in the nutrient solution. The radionuclide uptake increased with increasing exposure time. Both radionuclides were predominantly accumulated in fine-roots. However, needles proved to describe best the result of net root uptake and translocation to the shoot. The uptake-and and translocation-rates of 85Sr were smaller than those of 134Cs. It is assumed that the translocation is coupled with the intensity of water fluxes through the xylem and that 85Sr is more readily adsorbed into mycelium or plant tissue relative to 134Cs. The effect of high ammonium growth conditions was overcome by the effect of ectomycorrhization, except in needles with a very large biomass which behaved as a strong sink and led to a high accumulation of 134Cs.     

Impact of an exceptional Saharan dust outbreak in France: PM10 and artificial radionuclides concentrations in air and in dust deposit

The present study focuses on the exceptional Saharan dust event that affected most of France in February 2004. Activity levels of various artificial radionuclides (⁹⁰Sr, ¹³⁷Cs, uranium, thorium and plutonium isotopes, ²⁴¹Am) were examined. Activity or isotopic ratios are discussed in the context of atmospheric nuclear weapons tests, among them French tests performed in Sahara in the 1960s. The daily evolution of ¹³⁷Cs activity levels in the atmosphere was compared to daily PM₁₀ change. A link between airborne ¹³⁷Cs and PM₁₀, is given. It is estimated that this 2-day event deposited as much ¹³⁷Cs as would be deposited on average over a 10-month period. The amount of deposited ¹³⁷Cs and ^239+240Pu represents respectively about 0.1 and 1% of the activity already present in the soil. Such Saharan dust events correspond to an extreme type of “feeder” process of artificial radionuclides in the atmosphere. Therefore, they contribute to the long term background level of artificial radionuclides kept at trace levels in the atmosphere.     

Potential of Hemidesmus indicus for phytoextraction of lead from industrially contaminated soils

Many sites in the industrial region of Kattedan near Hyderabad, Andhra Pradesh (AP), India are contaminated with high concentrations of lead. The use of plants to remove toxic metals from soils (phytoremediation) is emerging as a potential strategy for cost-effective and environmentally sound remediation of contaminated soils. We studied remediation of soils contaminated with lead using a lead hyperaccumulating plant, Hemidesmus indicus. The ability of this plant to accumulate lead in shoots and roots was studied with pot experiments. The results showed that accumulation was maximum in roots for the first 1-3 weeks and later for a contact period of three months, the accumulation rate was maximum in shoots. In addition we used various chelating agents such as EDTA, HEDTA, DTPA and CDTA to determine the best chemical modifier for efficient lead removal from contaminated soils. The effect on lead accumulation of plant in the presence of various metal co-ions was also studied. An attempt was made for the decontamination of lead from five different "Real-life" soils of Kattedan using H. indicus.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

The influence of season and leaf age on concentrations of radiocaesium (137Cs), stable caesium (133Cs) and potassium in Agrostis capillaris

The transfer of radioactive caesium from soils to plants has been well researched. In contrast there is limited knowledge on natural stable 133Cs and its potential role as a predictor for radiocaesium behaviour. In a pot experiment with Agrostis capillaris close correlations were found between plant 137Cs and plant 133Cs concentrations (R2 90-96%). Season and leaf age had significant effects with concentrations increasing 10-30-fold between June and December. Simultaneously the plant concentrations of K, the nutrient analogue of Cs, decreased to around one third. In the soil the exchangeable fractions of K and 137Cs declined. No clear relationships were found between 137+133Cs in the plant and exchangeable K in the soil. However, at the end of the experiment the K content of the above-ground biomass was higher than the exchangeable pool in the soil, suggesting that depletion of soil K could be a key factor in the observed increase of plant 137+133Cs over time.     

Soil remediation: humic acids as natural surfactants in the washings of highly contaminated soils

The remediation of the highly contaminated site around the former chemical plant of ACNA (near Savona) in Northern Italy is a top priority in Italy. The aim of the present work was to contribute in finding innovative and environmental-friendly technology to remediate soils from the ACNA contaminated site. Two soils sampled from the ACNA site (A and B), differing in texture and amount and type of organic contaminants, were subjected to soil washings by comparing the removal efficiency of water, two synthetic surfactants, sodium dodecylsulphate (SDS) and Triton X-100 (TX100), and a solution of a natural surfactant, a humic acid (HA) at its critical micelle concentration (CMC). The extraction of pollutants by sonication and soxhlet was conducted before and after the soil washings. Soil A was richer in polycyclic aromatic hydrocarbons, whereas soil B had a larger content of thiophenes. Sonication resulted more analytically efficient in the fine-textured soil B. The coarse-textured soil A was extracted with a general equal efficiency also by soxhlet. Clean-up by water was unable to exhaustively remove contaminants from the two soils, whereas all the organic surfactants revealed very similar efficiencies (up to 90%) in the removal of the contaminants from the soils. Hence, the use of solutions of natural HAs appears as a better choice for soil washings of highly polluted soils due to their additional capacity to promote microbial activity, in contrast to synthetic surfactants, for a further natural attenuation in washed soils.     

90Sr uptake by Pinus ponderosa and Pinus radiata seedlings inoculated with ectomycorrhizal fungi

Strontium-90 ((90)Sr) is a radionuclide characteristic of fallout from nuclear reactor accidents and nuclear weapons testing. Prior studies have shown that Pinus ponderosa and P. radiata seedlings can remove appreciable quantities of (90)Sr from soil and store it in plant tissue. In this study, we inoculated P. ponderosa and P. radiata seedlings with one of five isolates of ectomycorrhizal fungi. Inoculated and noninoculated (control) seedlings were compared for their ability to remove (90)Sr from an organic growth medium. Seedlings were grown in a growth chamber in glass tubes containing 165 cm(3) of sphagnum peat moss and perlite (1 : 1 (v/v)) and, except in the controls, the fungal inoculum. After 3 months, 5978 Bq of (90)Sr in 1 ml of sterile, distilled, deionized water was added. Seedlings were grown for an additional month and then harvested. P. ponderosa seedlings with ectomycorrhizae accumulated 3.0-6.0% of the (90)Sr; bioconcentration ratios (Bq (90)Sr cm(-3) plant tissue/Bq (90)Sr cm(-3) growth medium) ranged from 98-162. Ectomycorrhizal P. radiata seedlings accumulated 6.0-6.9% of the (90)Sr; bioconcentration ratios ranged from 88-133. Nonmycorrhizal P. ponderosa and P. radiata seedlings accumulated only 0.6 and 0.7% of the (90)Sr and had bioconcentration ratios of 28 and 27, respectively. Ectomycorrhizal P. ponderosa and P. radiata seedlings are able to remove 3-5 times more (90)Sr from contaminated soil than seedlings without ectomycorrhizae.     

Seasonal variation of radionuclides in Fucus vesiculosus L. from the Oresund, Southern Sweden

The activity concentrations of radionuclides (60Co, 54Mn, 137Cs, 40K) in whole plants of Fucus vesiculosus of different ages, and also in tissues of different ages from the same plants were investigated in the vicinity of the Barseb?ck nuclear power plant in southern Sweden. Activity concentration differed between the tissues of different age of the plants, depending on the radionuclide as well as the time of year. The highest concentrations of 60Co and 54Mn were measured in the older parts of the plants in spring and summer, while the activity concentrations of 137Cs and 40K were highest in receptacles and new vegetative fronds. The discharge of radionuclides from the nuclear power plant was reflected in the measured activity concentration in the algae. For 60Co, the response seemed to be smoothed out when considering the whole plant, while the new vegetative tissue better reflected the discharge during the autumn. Thus, it is important to have knowledge about the autecology of the organism when it is used as an indicator for radionuclides.     

Hydrochemical modelling of the retention and transport of metallic radionuclides in the soils of an upland catchment

The CHemistry of the Uplands Model (CHUM) describes the transport of chemicals through upland catchments with acid, organic-rich soils, by a combination of sub-models for equilibrium soil chemistry, hydrology, weathering, and nitrogen cycling. CHUM was used to simulate the retention and transport of metallic radionuclides (Co, Sr, Cs, UO(2), U(IV), Th, Am), in the soils of a small catchment in Cumbria, UK, for 2 years after their atmospheric deposition in a single hypothetical precipitation event. Export of radionuclides to streamwater is calculated to occur most readily following deposition of the dissolved elements at high water saturation of the catchment, when little incoming rainwater is required to make up the small moisture deficit of the organic surface horizon, and solutes can move to greater depths in the soil profile. Deposition when the catchment is drier, or of particulate radionuclides, leads to stronger retention. Radionuclide retention or transport depends on the strength of chemical interaction with the solid phases of the different soil horizons; this varies among the elements, and also with oxidation state, U(IV) species being more strongly retained than UO(2). For purely organic soils, the least strongly retained radionuclide is Cs, but the presence in the mineral soil horizon of small amounts of clay mineral with high selectivity towards Cs can markedly increase with high selectivity towards Cs can markedly increase its retention. For the actinides, binding by dissolved organic matter is important; for example, the rate of transport of Th to the stream is increased by more than two orders of magnitude by complexation with dissolved fulvic acid. The model assumptions suggest that, in the longer term, losses from the catchment of Co, Sr and Cs would take place on a time-scale of decades, whereas the actinides would be much more persistent.     

Evaluation of copper availability to plants in copper-contaminated vineyard soils

The repeated use of copper (Cu) fungicides to control vine downy mildew has led to long-term accumulation of Cu in vineyard soils which now raises the issue of the potential bioavailability of Cu for various living organisms including plant species. The bioavailable Cu can be defined as the portion of soil Cu that can be taken up by roots, for a given plant species. In order to evaluate the bioavailability of Cu to plants, a pot experiment was conducted in glasshouse conditions with a crop species (maize) and 12 soils sampled in the upper horizon of 10 vineyard plots (total Cu ranging from 38 to 251 mg kg-1) and two woodland plots (control soils that had not received any Cu application; total Cu amounting to 20-26 mg kg-1). These soils were selected for their diverse physical (large range of particle size distribution) and chemical (from acid to calcareous soils) properties. After 35 days of growth, plant shoots were harvested for analysis. The roots were separated from soil particles for further analysis. The concentrations of Cu in the roots and aerial parts of the maize were then compared with the amounts of Cu extracted from the soil by a range of conventional extractants. Observed Cu concentrations in maize roots which have grown in contaminated vineyard soils were very high (between 90 and 600 mg kg-1), whereas Cu concentrations in the aerial parts varied only slightly and remained low (< 18 mg kg-1). Root Cu concentrations observed for maize increased with increasing total Cu content in the soil and with decreasing soil CEC. Cu accumulation in maize roots may be as high in calcareous soils as in acid soils, suggesting that soil pH had little influence. In the case of the vineyard soils studied, the lack of correlation found for maize between Cu concentrations in roots and in the aerial parts, suggests that an analysis of the aerial parts would not be a good indicator of plant Cu uptake, as it provides no insight into the real amount of Cu transferred from the soil to the plant. For maize, our results show that extraction with organic complexing agents (EDTA, DTPA) and extraction with ammonium acetate seem to provide a reasonably good estimate of root Cu concentration.     

The application of bioassays as indicators of petroleum-contaminated soil remediation

Bioremediation has proven successful in numerous applications to petroleum contaminated soils. However, questions remain as to the efficiency of bioremediation in lowering long-term soil toxicity. In the present study, the bioassays Spirotox, Microtox, Ostracodtoxkit F, umu-test with S-9 activation, and plant assays were applied, and compared to evaluate bioremediation processes in heavily petroleum contaminated soils. Six higher plant species (Secale cereale L., Lactuca sativa L., Zea mays L., Lepidium sativum L., Triticum vulgare L., Brassica oleracea L.) were used for bioassay tests based on seed germination and root elongation. The ecotoxicological analyses were made in DMSO/H2O and DCM/DMSO soil extracts. Soils were tested from two biopiles at the Czechowice oil refinery, Poland, that have been subjected to different bioremediation applications. In biopile 1 the active or engineered bioremediation process lasted four years, while biopile 2 was treated passively or non-engineered for eight months. The test species demonstrated varying sensitivity to soils from both biopiles. The effects on test organisms exposed to biopile 2 soils were several times higher compared to those in biopile 1 soils, which correlated with the soil contaminants concentration. Soil hydrocarbon concentrations indeed decreased an average of 81% in biopile 1, whereas in biopile 2 TPH/TPOC concentrations only decreased by 30% after eight months of bioremediation. The bioassays were presented to be sensitive indicators of soil quality and can be used to evaluate the quality of bioremediated soil. The study encourages the need to combine the bioassays with chemical monitoring for evaluation of the bioremediation effectiveness and assessing of the contaminated/remediated soils.