Technetium: A toxic waste product of the nuclear fuel cycle: Effects on soybean growth and development

Technetium-99 (⁹⁹Tc) is formed in significant amounts (6.2% fission yield) during fission in both nuclear reactors and nuclear bombs. The effects of technetium on soybeans (Glycine max) were studied in relation to (a) cytochemical events in the apical meristems of germinating seedlings; (b) growth responses to 0, 0.04, 0.2, 1.0, 5.0, and 20.0 ppm Tc; (c) growth responses to varying levels of Tc after a prior 5-day germination on Tc-free media, and (d) response to Tc in the presence of added manganese.By 20 days, reductions in growth were evident at all levels of Tc except 0.04 ppm (Experiment 2). Root growth was most severely affected, and seedling abnormality at 20 ppm was fivefold greater than that of the controls. The effect of 20 ppm Tc was evident at 10 days when the accumulated absorption dose was approximately 25 rads. The first evidence of damage at this dose was a delay in the initiation of the first trifoliate leaf. The shoot meristem size was 1.2-fold smaller than that of the control; however, there was no cytological evidence of radiation-induced damage. Observation of mitotic figures did not reveal any chromosome aberrations, micronuclei, or chromosome bridges. The lowest level of Tc showing toxicity was 0.2 ppm which resulted in a 31% reduction in growth at 20 days. The accumulated dose was 0.5 rad (0.025 rad/day) and thus it seems unlikely that the rapid inhibition of growth and development is due to radiological toxicity. It is quite probable that the growth effects are due to chemical toxicity possibly due to nutrient competition and/or substitution in uptake or metabolism. However, extremely low doses of radiation have been shown to delay the onset of DNA synthesis (possibly by membrane effects) inTradescantia and until the actual mechanism of Tc inhibition is determined a radiation effect cannot be totally ruled out.This research was partially supported by ERDA Contract EY-76-S-02-4139     

Accumulation of selenium in sugarcane (Sachharum officinarum Linn.) in seleniferous areas of Punjab,India

A survey was conducted during 1986–88 to assess the level and pattern of accumulation of selenium in sugarcane plants in seleniferous areas of Punjab (India). Total and water-extractable (available) selenium ranged from 0.55 to 2.58 (mean 1.43 ± 0.67) mg kg^–1 and from 0.02 to 0.05 (mean 0.033 ± 0.007) mg kg^–1, respectively, in seleniferous areas. Corresponding values from non-seleniferous areas were 0.23–0.55 (mean 0.36 ± 0.08) mg kg^–1 and 0.015–0.025 (mean 0.020 ± 0.003) mg kg^–1, respectively. Sugarcane tops from seleniferous areas accumulated high levels of selenium ranging from 7.9 to 67.5 mg kg^–1. These selenium levels were 6–14 times higher than those from non-seleniferous areas. During the early stages of growth (June), the selenium content was highest but decreased during the months of July and August and then did not change up to maturity. In the seleniferous areas sugarcane tops and canes at maturity contained 5.7–9.5 and 1.8–2.1 mg Se kg^–1, respectively. However, the tops and canes of plants growing near the permanent boundary (bundh) contained 9.5–18.8 and 2.1–2.4 mg Se kg^–1, respectively.In a field experiment on sugarcane, application of gypsum up to 1 ton ha^–1 resulted in a significant reduction of selenium content in sugarcane tops as well as in the cane. Selenium content in sugarcane tops at maturity was reduced from 15.16 to 5.08 mg kg^–1 by applying gypsum of 1 ton ha^–1.     

A stochastic approach for the operation of a wind and pumped storage plant under a deregulated environment

To improve the competiveness in the energy market, it is necessary that the wind power plants provide guaranteed power generation, although, it is not possible to forecast power availability from wind power plant accurately. This paper presents a stochastic model and solution technique for the combined operation of wind and pumped storage power plants to improve the power availability and increasing the profit considering uncertainties of wind power generation. In this model, uncertainties in wind data have been forecasted for grid connected day-ahead market using Weibull distribution model. The imbalances in the forecasted wind data and the market demand have been reduced by operating the pumped storage power plant. In this stochastic mixed integer problem, pumped storage plant can take the supply either from the grid or from the wind power plant for the pumping operation to store the energy in order to utilize this energy during peak hours for increasing the overall revenue. The reliability of the pumped storage is improved by replacing the conventional unit with the adjustable speed type pumped storage unit. In order to prove the optimality of the solution, two case studies were considered. In case study–I, scheduling is provided by operating the conventional pumped storage unit, whereas in case study–II, adjustable speed pumped storage unit has been used. It has been found that the adjustable speed pumped storage unit has further reduced the imbalance between generated power and demand. The complete approach has been formulated and implemented using AMPL software.     

Using citizen science in environmental justice: participation and decision-making in a Southern California waste facility siting conflict

Uses of science by environmental justice (EJ) activists reflect struggles to challenge professional scientific expertise, achieve fair outcomes, and effectively participate in decision-making processes. This qualitative research analyses the relationship between citizen science and EJ in a new waste facility siting conflict in urban Los Angeles, namely connections between citizen science and four dimensions of EJ: fair distribution, respect and recognition, participation in decision-making, and community capabilities. Citizen science is one tactic in EJ, yet little research investigates its role in a new facility siting conflict, particularly in relation to multi-faceted EJ goals. The research reveals opportunities for individual empowerment and community capacity building using citizen science, and a small measure of improved respect and recognition for participants who brought their own knowledge, research, and voices to the table. At the same time, the work identifies limitations on citizen science to improve local participatory procedures and decision-making, which also constricted the achievement of outcomes most desired by the EJ group: to prevent approval and construction of the new waste facility. This paper argues that uses of citizen science contributed to partial achievement of EJ goals, while hindered by governance processes that call for public participation yet shield decision-makers from substantive engagement with the volume or content of that participation.     

Freeze–dried synthesized bifunctional biopolymer nanocomposite for efficient fluoride removal and antibacterial activity

Local fluoride contamination and bacterial infections in potable water have dangerous effects on the human body and are today a global concern. In this study, we have synthesized a pH-responsive bifunctional biopolymer nanocomposite (HAZ) of humic acid with incorporating aluminum zirconium bimetallic oxide by deep freeze–drying method. Fast nucleation and interconnection of nanoparticles form a highly porous network because of sublimation of frozen HAZ. This duo nanocomposite has efficiently worked for fluoride removal and showed potent antibacterial activity against the Escherichia coli Gram-negative and Staphylococcus aureus Gram-positive bacteria. The X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the hydroxyl groups act as a pivot in the ion exchange process of adsorption, each element of bimetallic oxide primarily takes part in the adsorption mechanism. The maximum adsorption capacity of the adsorbent was 180.62 mg/g at pH seven. Thermodynamic parameters like Gibbs free energy change (ΔG⁰), entropy (ΔS⁰), and enthalpy (ΔH⁰) indicate that the process was endothermic, feasible, and taken place by a chemisorption mechanism. This is the first novel freeze–dried bifunctional biopolymer nanocomposite composed of humic acid natural polymer incorporated with Al–Zr metal oxide, and it exhibited three times higher adsorption efficacy with excellent antibacterial action at a concentration of 5 µg/mL of the nanocomposite.     

Bioavailability of selenium to forage crops in a sandy loam soil amended with Se-rich plant materials

Greenhouse experiments were conducted to study the bioavailability of selenium (Se) to sorghum (Sorghum bicolor L.), maize (Zea mays L.) and berseem (Trifolium alexandrinum L.) fodders in a sandy loam soil amended with different levels of Se-rich wheat (Triticum aestivum L.) and raya (Brassica juncea L. Czern) straw containing 53.3 and 136.7microg Seg(-1), respectively. Each of the fodder crops was grown after incorporation of Se-rich materials either individually or in a sequence - sorghum-maize-berseem by incorporating Se-rich straws only to the first crop. Application of Se-rich straws to each crop, even at the greatest rate of 1%, did not have any detrimental effect on dry matter yield of different crops. With increase in the level of wheat straw from 0% to 1%, Se content in sorghum and maize plants increased to greatest level of 1.3 and 1.5microg g(-1), respectively, at 0.3% of applied straw and thereafter it decreased consistently. In case of raya straw, the greatest Se content in sorghum (2.3microg g(-1)) and maize (3.0microg g(-1)) was recorded at 0.3% and 0.4% of the applied straw, respectively. Unlike sorghum and maize fodders, Se content in all the four cuts of berseem continued to increase with increase in the level of applied straws and for different cuts of berseem it varied from 1.6 to 2.3 and 3.4 to 4.3microg g(-1) in case of wheat and raya straw, respectively. Similar variations in Se content of different fodder crops were recorded when these were grown in the sequence - sorghum-maize-berseem; but Se content was 2-4 times lower than when each crop was grown with fresh application of Se-rich straw. None of the fodders absorbed Se in levels toxic for animal consumption (>5microg g(-1)) even at the greatest level of applied straw. Of the total Se added through Se-rich straws, utilization of Se was not more than 2% in case of sorghum and maize crops and up to 5% in case of berseem. At the time of sowing of sorghum, hot water soluble Se (HWS-Se) in soils treated with different levels of Se-rich wheat and raya straw, respectively, varied from 18 to 36 and 18 to 79microg kg(-1). Whereas in case of berseem, it varied from 33 to 101 and 33 to 154microg kg(-1), respectively. HWS-Se present at the sowing time of berseem was significantly correlated with Se content of all the four cuts in the soil treated with Se-rich straws; the coefficients of correlation 'r' varied between 0.79 (p0.05) and 0.99 (p0.001). Selenium-rich materials supplied significant amounts of S, P and micronutrients to the growing fodder crops. These investigations suggest that Se-rich raya and wheat straw may be disposed off safely in soils used for growing fodders.