The Fate of Hydrogen Peroxide as an Oxygen Source for Bioremediation Activities within Saturated Aquifer Systems

ABSTRACT

In situ bioremediation is an innovative technique for the remediation of contaminated aquifers that involves the use of microorganisms to remediate soils and groundwaters polluted by hazardous substances. During its application, this process may require the addition of nutrients and/or electron acceptors to stimulate appropriate biological activity. Hydrogen peroxide has been commonly used as an oxygen source because of the limited concentrations of oxygen that can be transferred into the groundwater using above-ground aeration followed by reinjection of the oxygenated groundwater into the aquifer or subsurface air sparging of the aquifer. Because of several potential interactions of H₂O₂ with various aquifer material constituents, its decomposition may be too rapid, making effective introduction of the H₂O₂ into targeted treatment zones extremely difficult and costly. Therefore, a bench-scale study was conducted to determine the fate of H₂O₂ within subsurface aquifer environments. The purpose of this investigation was to identify those aquifer constituents, both biotic and abiotic, that are most active in controlling the fate of H₂O₂. The decomposition rates of H₂O₂ were determined using both equilibrated water samples and soil slurries. Results showed H₂O₂ decomposition to be effected by several commonly found inorganic soil components; however, biologically mediated catalytic reactions were determined to be the most substantial.     

Sorption of metolachlor and atrazine in fly ash amended soils: comparison of optimized isotherm models

Adsorption of metolachlor and atrazine was studied in the fly ash (Inderprastha and Badarpur)- amended Inceptisol and Alfisol soils using batch method. Results indicated that sorption of both the herbicides in soil+fly ash mixtures was highly nonlinear and sorption decreased with a higher herbicide concentration in the solution. Also, nonlinearity increased with an increase in the level of fly ash amendment from 0-5%. Three two-parameter monolayer isotherms viz. Langmuir, Temkin, Jovanovic and one imperical Freundlich models were used to fit the experimental data. Data analysis and comparison revealed that the Temkin and the Freundlich isotherms were best-suited to explain the sorption results and the observed and the calculated adsorption coefficient values showed less variability. The study suggested that sorption mechanism of metolachlor and atrazine involved the physical association at the sorbate surface and the nonlinearity in the sorption at higher pesticide or fly ash concentration was due to a decrease in the heat of adsorption and higher binding energy.     

Effect of compression ratio,nozzle opening pressure,engine load,and butanol addition on nanoparticle emissions from a non-road diesel engine

Currently, diesel engines are more preferred over gasoline engines due to their higher torque output and fuel economy. However, diesel engines confront major challenge of meeting the future stringent emission norms (especially soot particle emissions) while maintaining the same fuel economy. In this study, nanosize range soot particle emission characteristics of a stationary (non-road) diesel engine have been experimentally investigated. Experiments are conducted at a constant speed of 1500 rpm for three compression ratios and nozzle opening pressures at different engine loads. In-cylinder pressure history for 2000 consecutive engine cycles is recorded and averaged data is used for analysis of combustion characteristics. An electrical mobility-based fast particle sizer is used for analyzing particle size and mass distributions of engine exhaust particles at different test conditions. Soot particle distribution from 5 to 1000 nm was recorded. Results show that total particle concentration decreases with an increase in engine operating loads. Moreover, the addition of butanol in the diesel fuel leads to the reduction in soot particle concentration. Regression analysis was also conducted to derive a correlation between combustion parameters and particle number emissions for different compression ratios. Regression analysis shows a strong correlation between cylinder pressure-based combustion parameters and particle number emission.

     

Abiotic Oxidation Studies of Oxo-biodegradable Polyethylene

The best approach to induce oxo-biodegradation in polyethylene is the use of special additives known as pro-oxidants. Pro-oxidants accelerate abiotic oxidation and subsequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. In this work, the abiotic oxidation is studied to understand how the addition of nanoclay affects the oxidation rate and the degradation mechanism of oxo-biodegradable polyethylene. In order to achieve this, the following materials were used in this study: (1) polyethylene (PE), (2) oxo-biodegradable polyethylene (OPE), (3) polyethylene nanocomposite (PENac), and (4) oxo-biodegradable polyethylene nanocomposite (OPENac). Wide-Angle X-ray scattering (WAXS) and Transmission Electron Microscopy (TEM) studies reveal that grafting in the preparation of composites helps to achieve mixed intercalated/exfoliated morphology in PENac and OPENac. Abiotic oxidation was carried out in an oven for a period of 14 days at 70 °C with air supply. The effect of abiotic oxidation was evaluated by measuring the changes in tensile strength, elongation at break, carbonyl index and molecular weight. Results show that OPE and OPENac are more susceptible to oxidation than PENac. The molecular weight distribution data obtained from GPC reveal that the addition of nanoclay does not alter the oxidation mechanism in OPE significantly.     

Atmospheric aerosols at a regional background Himalayan site—Mukteshwar, India

Continuous aerosol measurements were made at a regional background station (Mukteshwar) located in a rural Himalayan mountain terrain from December 2005 to December 2008 for a period of 3 years. The average concentrations of particulate matter less than or equal to 10 μm (PM₁₀), particulate matter less than or equal to 2.5 μm (PM_2.5) and black carbon (BC) are 46.0, 26.6 and 0.85 μg/m³ during the study period. Majority of the PM₁₀ values lie below 100 μg/m³ while majority of the PM_2.5 values lie below 30 μg/m³. It is further seen that during the monsoon months, especially July and August, the average values are comparatively low. It is also noted that the PM_2.5/PM₁₀ ratios between 0.50 and 0.75 have the maximum frequency distribution in the data set. Furthermore, the monthly mean ratio of BC to PM_2.5 mass lies between 3.0 and 7.5 % during the study period. Though the average PM₁₀ and PM_2.5 concentrations during the study period are less than the respective Indian ambient air quality standards, however, they are still above the WHO guidelines and would have adverse health impacts. This shows that even in rural/background regions that are far away from major pollution sources or urban areas, the aerosol concentrations are significant and require long-term monitoring, source quantification and aerosol model simulations.     

What difference might sewage treatment performance make to endocrine disruption in rivers?

An assessment of the steroid estrogen removing performance of 23 different sewage treatment plants (STPs) was performed. The assessment relied on a model to estimate influent concentrations, and completed questionnaires on the STP treatment details from the relevant water companies. This information was compared with observed effluent 17beta-estradiol (E2) and estrone (E1) concentrations. The 10 biological filter plants (BFP) in the study performed poorly with only 30% (SD 31) removal on average for E1. This reduced E1 removal performance of the BFPs compared to all the other STP types in the survey was statistically significant (p<0.001). Scenarios of all the STPs as activated sludge types, and one as all BFP types were modelled using the GREAT-ER model set up for the Aire/Calder catchment in the UK. This difference was shown to have an important effect on predicted river E1 concentrations and consequent risk classifications.     

Statistical inferences from measured data on concentrations of naturally occurring radon,thoron, and decay products in Kumaun Himalayan belt

Environmental Science and Pollution Research - Regional averages of radon, thoron, and associated decay product concentration are reported to be higher than their respective global averages in...     

Selective sensing of mercury(II) using PVC-based membranes incorporating recently synthesized 1,3-alternate thiacalix[4]crown ionophore

The construction and electrodes characteristics of poly(vinylchloride) (PVC)-based polymeric membrane electrode (PME) and coated graphite electrode (CGE), incorporating 1,3-alternate thiacalix[4]crown as ionophore for estimation of Hg(II) ions, are reported here. The best potential response was observed for PME-1 having membrane composition of: ionophore (6.2 mg), PVC (100.0 mg), 2-nitrophenyl octyl ether (2-NPOE; 200.0 mg), and sodium tetraphenyl borate (NaTPB; 2.0 mg); for CGE-1 with the membrane composition: ionophore (3.5 mg), PVC (40.0 mg), 2-NPOE (80.0 mg), and NaTPB (2.0 mg). The electrodes exhibits Nernstian slope of 29.16 mV/decade with PME-1 and 30.39 mV/decade with CGE-1 for Hg(II) ions over wide concentration range, i.e., 1.0?×?10^?1 to 5.0?×?10^?6?M with PME-1 and 1.0?×?10^?1 to 5.0?×?10^?7?M with CGE-1. Lower detection limits were found to be 9.77?×?10^?6?M for PME-1 and 7.76?×?10^?7?M for CGE-1 with response time varying from 10 to 20 s. Also, these electrodes work within pH range of 2.0–6.0 for PME-1 and 1.5–6.5 for CGE-1. Overall, CGE-1 has been found to be better than PME-1. CGE-1 has been used as indicator electrode for the potentiometric titration of Hg(II) ions with EDTA as well as successfully applied for determination of Hg(II) content in wastewater, insecticide, dental amalgam, and ayurvedic medicines samples with very good performance (0.9974 correlation coefficient in the comparison against volumetric method).