Distributions of radionuclide sorption coefficients (Kd) in sub-surface sediments and the implications for transport calculations

The effect of the spatial variability of K_d on calculations of contaminant travel time in the vadose zone was determined. Depth discrete measurements of K_d were made for a suite of radionuclides (¹⁰⁹Cd, ⁵⁷Co, ⁶⁰Co, ⁸⁵Sr, ¹³⁷Cs, and ⁸⁸Y) utilizing a sediment core from the E-Area at the Savannah River Site. The K_d’s were ordered as ⁸⁵Sr²⁺ < ¹³⁷Cs⁺ < ¹⁰⁹Cd²⁺ < ⁵⁷Co²⁺ = ⁶⁰Co²⁺ << ⁸⁸Y³⁺ and the values generally fell below or near the lowest quartile of values reported in the literature. Correlations were generally weak between soil properties and K_d values. Most importantly, all of the K_d distributions could be reasonably approximated as log-normal. Deterministic and stochastic calculations of contaminant travel time to the water table were made. The deterministic calculations were based on each of three conceptual models of the vadose zone: complete stratification (17 strata, each with a different K_d), two strata (two sections of the vadose zone, each characterized by a single, average K_d), and unstratified (a single zone with an average K_d). Stochastic calculations were based on log-normal fits to the K_d data. The two strata model generally yielded travel times 2× greater than those in the completely stratified model. The unstratified model yielded travel times that were between 3 and 5 times greater than the completely stratified model. The stochastic mean travel times were comparable to those of the two strata model.     

Variation of radiation level and radionuclide enrichment in high background area

Significantly high radiation level and radionuclide concentration along Quilon beach area of coastal Kerala have been reported by several investigators. Detailed gamma radiation level survey was carried out using a portable scintillometer. Detailed studies on radionuclides concentration in different environmental matrices of high background areas were undertaken in the coastal areas of Karunagapalli, Kayankulam, Chavara, Neendakara and Kollam to study the distribution and enrichment of the radionuclides in the region. The absorbed gamma dose rates in air in high background area are in the range 43-17,400 nGyh⁻¹. Gamma radiation level is found to be maximum at a distance of 20 m from the sea waterline in all beaches. The soil samples collected from different locations were analysed for primordial radionuclides by gamma spectrometry. The activity of primordial radionuclides was determined for the different size fractions of soil to study the enrichment pattern. The highest activity of ²³²Th and ²²⁶Ra was found to be enriched in 125-63 μ size fraction. The preferential accumulation of ⁴⁰K was found in <63 μ fraction. The minimum ²³²Th activity was 30.2 Bq kg⁻¹, found in 1000-500 μ particle size fraction at Kollam and maximum activity of 3250.4 Bq kg⁻¹ was observed in grains of size 125-63 μ at Neendakara. The lowest ²²⁶Ra activity observed was 33.9 Bq kg⁻¹ at Neendakara in grains of size 1000-500 μ and the highest activity observed was 482.6 Bq kg⁻¹ in grains of size 125-63 μ in Neendakara. The highest ⁴⁰K activity found was 1923 Bq kg⁻¹ in grains of size <63 μ for a sample collected from Neendakara. A good correlation was observed between computed dose and measured dose in air. The correlation between ²³²Th and ²²⁶Ra was also moderately high. The results of these investigations are presented and discussed in this paper.     

Investigations into the differential reactivity of endogenous and exogenous mercury species in coastal sediments

Stable isotopic tracer methodologies now allow the evaluation of the reactivity of the endogenous (ambient) and exogenous (added) Hg to further predict the potential effect of Hg inputs in ecosystems. The differential reactivity of endogenous and exogenous Hg was compared in superficial sediments collected in a coastal lagoon (Arcachon Bay) and in an estuary (Adour River) from the Bay of Biscay (SW France). All Hg species (gaseous, aqueous, and solid fraction) and ancillary data were measured during time course slurry experiments under variable redox conditions. The average endogenous methylation yield was higher in the estuarine (1.2 %) than in the lagoonal sediment (0.5 %), although both methylation and demethylation rates were higher in the lagoonal sediment in relation with a higher sulfate-reducing activity. Demethylation was overall more consistent than methylation in both sediments. The endogenous and exogenous Hg behaviors were always correlated but the exogenous inorganic Hg (IHg) partitioning into water was 2.0–4.3 times higher than the endogenous one. Its methylation was just slightly higher (1.4) in the estuarine sediment while the difference in the lagoonal sediment was much larger (3.6). The relative endogenous and exogenous methylation yields were not correlated to IHg partitioning, demonstrating that the bioavailable species distributions were different for the two IHg pools. In both sediments, the exogenous IHg partitioning equaled the endogenous one within a week, while its higher methylation lasted for months. Such results provide an original assessment approach to compare coastal sediment response to Hg inputs.     

Effects of agricultural pesticides on the health of Rana pipiens frogs sampled from the field

There is evidence that over the last 30 years, there have been mass declines in diverse geographic locations among amphibian populations due to disease outbreaks. Multiple causes have been suggested to explain this increase in disease incidence. Among these, climate changes, environmental pollution and reduced water quality are gaining attention. Indeed, some chemicals of environmental concerns are known to alter the immune system. It is possible that exposure to these pollutants could alter the immune system of anurans and render them more susceptible to different pathogens. In this study, we sampled Rana pipiens in five different sites near St. Lawrence River (Quebec, Canada) during the months of July and September in 2001. Two of these sites were protected areas, in which low levels of pesticides were detected, while the remaining three sites were located in areas with intensive corn and soybeans cultivations. Our results demonstrated that frogs living in agricultural regions are smaller in size and weight than frogs living in areas with lower levels of pesticides at both sampling times. Moreover, we have observed a significant decrease in the number of splenocytes (cellularity) and the phagocytic activity in frogs sampled in impacted sites. Taken together, these results suggest that frogs living in agricultural regions might be more vulnerable to infections and diseases through their smaller size and alteration of their immune system. Our results also contribute to the overall discussion on factors involved in amphibian declines.     

Low-cost adsorbents from bio-waste for the removal of dyes from aqueous solution

Activated carbons (ACs) were developed from bio-waste materials like rice husk and peanut shell (PS) by various physicochemical activation methods. PS char digested in nitric acid followed by treatment at 673 K resulted in high surface area up to ～585 m²/g. The novelty of the present study is the identification of oxygen functional groups formed on the surface of activated carbons by infrared and X-ray photoelectron spectroscopy and quantification by using temperature programmed decomposition (TPD). Typical TPD data indicated that each activation method may lead to varying amounts of acidic and basic functional groups on the surface of the adsorbent, which may be a crucial factor in determining the adsorption capacity. It was shown that ACs developed during the present study are good adsorbents, especially for the removal of a model textile dye methylene blue (MB) from aqueous solution. As MB is a basic dye, H₂O₂-treated rice husk showed the best adsorption capacity, which is in agreement with the acidic groups present on the surface. Removal of the dye followed Langmuir isotherm model, whereas MB adsorption on ACs followed pseudo-second-order kinetics.     

Photocatalytic degradation of contaminants of concern with composite NF-TiO2 films under visible and solar light

This study reports the synthesis and characterization of composite nitrogen and fluorine co-doped titanium dioxide (NF-TiO₂) for the removal of contaminants of concern in wastewater under visible and solar light. Monodisperse anatase TiO₂ nanoparticles of different sizes and Evonik P25 were assembled to immobilized NF-TiO₂ by direct incorporation into the sol–gel or by the layer-by-layer technique. The composite films were characterized with X-ray diffraction, high-resolution transmission electron microscopy, environmental scanning electron microscopy, and porosimetry analysis. The photocatalytic degradation of atrazine, carbamazepine, and caffeine was evaluated in a synthetic water solution and in an effluent from a hybrid biological concentrator reactor (BCR). Minor aggregation and improved distribution of monodisperse titania particles was obtained with NF-TiO₂-monodisperse (10 and 50 nm) from the layer-by-layer technique than with NF-TiO₂?+?monodisperse TiO₂ (300 nm) directly incorporated into the sol. The photocatalysts synthesized with the layer-by-layer method achieved significantly higher degradation rates in contrast with NF-TiO₂-monodisperse titania (300 nm) and slightly faster values when compared with NF-TiO₂-P25. Using NF-TiO₂ layer-by-layer with monodisperse TiO₂ (50 nm) under solar light irradiation, the respective degradation rates in synthetic water and BCR effluent were 14.6 and 9.5?×?10^?3?min^?1 for caffeine, 12.5 and 9.0?×?10^?3?min^?1 for carbamazepine, and 10.9 and 5.8?×?10^?3?min^?1 for atrazine. These results suggest that the layer-by-layer technique is a promising method for the synthesis of composite TiO₂-based films compared to the direct addition of nanoparticles into the sol.     

Potential of the microbial community present in an unimpacted beach sediment to remediate petroleum hydrocarbons

The potential of the microbial communities present in the intertidal zone of an unimpacted beach (a beach that did not suffer any significant oil spill) to degrade hydrocarbons was investigated. For that, laboratory-based microcosms (50-ml flasks) were set up with sandy beach sediment spiked with crude oil and incubated with local seawater for 15 days in the dark. Three bioremediation treatments were tested (biostimulation (BS), autochthonous bioaugmentation (AB), and combined treatment of biostimulation + bioaugmentation (BS + AB)) and the results were compared with natural attenuation (NA). Visual inspection showed clearly an oil solubility increase (confirmed by a higher hydrocarbons concentration in supernatant solutions) for all tested treatments when compared to NA. Significant degradation of the oil, shown by different profiles of petroleum hydrocarbons, was also observed for the different treatments particularly for BS + AB. Therefore, the microbial community of this unimpacted beach sediment could respond to an oil spill, degrading hydrocarbons. But to increase the natural attenuation pace, obtained results indicated that BS + AB is an appropriate approach for the bioremediation of beaches recently impacted by an oil spill. The autochthonous microbial cultures can be obtained “before” or “after” the contamination of the target site, being inoculated into the site right after it contamination.     

Health care industries: potential generators of genotoxic waste

Health care waste includes all the waste generated by health care establishments, research facilities, and laboratories. This constitutes a variety of chemical substances, such as pharmaceuticals, radionuclides, solvents, and disinfectants. Recently, scientists and environmentalists have discovered that wastewater produced by hospitals possesses toxic properties due to various toxic chemicals and pharmaceuticals capable of causing environmental impacts and even lethal effects to organisms in aquatic ecosystems. Many of these compounds resist normal wastewater treatment and end up in surface waters. Besides aquatic organisms, humans can be exposed through drinking water produced from contaminated surface water. Indeed, some of the substances found in wastewaters are genotoxic and are suspected to be potential contributors to certain cancers. The aim of this study was to evaluate the genotoxic and cytotoxic potential of wastewaters from two hospitals and three clinical diagnostic centers located in Jaipur (Rajasthan State), India using the prokaryotic Salmonella mutagenicity assay (Ames assay) and the eukaryotic Saccharomyces cerevisiae respiration inhibition assay. In the Ames assay, untreated wastewaters from both of the health care sectors resulted in significantly increased numbers of revertant colonies up to 1,000–4,050 as measured by the Salmonella typhimurium TA98 and TA100 strains (with and without metabolic activation) after exposure to undiluted samples, which indicated the highly genotoxic nature of these wastewaters. Furthermore, both hospital and diagnostic samples were found to be highly cytotoxic. Effective concentrations at which 20 % (EC₂₀) and 50 % (EC₅₀) inhibition of the respiration rate of the cells occurred ranged between ～0.00 and 0.52 % and between 0.005 and 41.30 % (calculated with the help of the MS excel software XLSTAT 2012.1.01; Addinsoft), respectively, as determined by the S. cerevisiae assay. The results indicated that hospital wastewaters contain genotoxic and cytotoxic components. In addition, diagnostic centers also represent small but significant sources of genotoxic and cytotoxic wastes.     

Synergistic effect of Eugenia jambolana Linn. and Solidago canadensis Linn. leaf extracts with deltamethrin against the dengue vector Aedes aegypti Linn. at Mysore

With the goal in mind to minimize the application of environmentally hazardous chemical insecticides, the larvicidal activity of two plant extracts along with deltamethrin was studied at University of Mysore. The extracts of Solidago canadensis and Eugenia jambolana were employed for working out the synergistic efficacy against Aedes aegypti larvae, as the extracts of both the plants exhibited high efficacy when applied individually. The deltamethrin when analyzed separately, LC₅₀ and LC₉₀ values were 0.00045 and 0.00148 ppm, respectively. Synergistic studies with two plant extracts on deltamethrin revealed S. canadensis as more effective with synergistic factor(SF) of 4.090 for LC₅₀ value and 4.781 for LC₉₀ followed by E. jambolana with SF 1.80 for LC₅₀ and 2.467 for LC₉₀ at 1:1 ratio of the phytoextracts and deltamethrin. Thus, S. canadensis was found to be a better larvicidal and synergistic agent. Combination of phytochemical and insecticide were found to be more effective than insecticides or phytochemicals alone which could be a good ecofriendly and cost-effective approach to reduce the dose of chemicals with high residual effect to be applied in vector control programs.