Vadose zone oxygen (O2) dynamics during drying and wetting cycles: An artificial recharge laboratory experiment

Vadose zone oxygen dynamics control all subsurface redox reactions and play a decisive role in maintaining groundwater quality. Although drying and wetting events are common in artificial recharge, their effects on subsurface oxygen distribution are poorly documented. We monitored oxygen concentration in the unsaturated zone in a mid-scale (1 m high) laboratory soil lysimeter, which was subjected to short wetting and drying cycles that simulated a highly permeable shallow aquifer recharged by river water. Ten cycles of varying duration were performed for a period of 85 days. Measurements of oxygen in the liquid and the gas phases were recorded every 20 s using non-invasive optical fibers (PreSens). The results provided high-resolution (in time) oxygen concentration maps. The infiltration rate revealed a decreasing trend during wetting cycles associated with biological clogging. Such a decrease with time was accompanied by a depletion of O2 concentration, occurring within the first few hours of the infiltration. During drying, O2 concentrations recovered rapidly at all depths owing to air flushing, resulting in a stratified vertical profile consistent with the biological consumption of O2 along the air infiltration path. Furthermore, drying periods caused a potential recovery of the infiltration capacity while preserving the soil biological activity. Scraping also led to the recovery of the infiltration capacity of the soil but was less effective than drying. Our experiment suggests that the small-scale heterogeneity played a key role in accurately mapping pore-scale O2 concentrations and should be considered in modeling O2 fluxes of unsaturated soils under natural or managed recharge conditions

Polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) in biochar and biochar-amended soil: A review

Residual pollutants including polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and carbon (aceous) nanoparticles are inevitably generated during the pyrolysis of waste biomass and remain on the solid coproduct called biochar. Such pollutants could have adverse effects on the plant growth as well as microbial community in soil. Although biochar has been proposed as a ‘carbon negative strategy’ to mitigate the greenhouse gas emissions, the impacts of its application with respect to long���term persistence and bioavailability of hazardous components are not clear. Moreover, the co���occurrence of low molecular weight VOCs with PAHs in biochar may exert further phytotoxic effects. This review describes the basic need to unravel key mechanisms driving the storage vs. emission of these organics and the dynamics between the sorbent (biochar) and soil microbes. Moreover, there is an urgent need for standardized methods for quantitative analysis of PAHs and VOCs in biochar under environmentally relevant conditions. This review is also extended to cover current research gaps including the influence of biochar application on the short��� and long���term fate of PAHs and VOCs and the proper control tactics for biochar quality and associated risk.This study was supported by a grant from the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST) (No. 2009���0093848). This work was also carried out with the support of the ‘Cooperative Research Program for Agriculture Science & Technology Development’ (Project title: Study on model development to control odor from hogpens, Project No. PJ01052101) Rural Development Administration, Republic of Korea. The second author also acknowledges the support made by a National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2014RA1A004893)

Effect of spatial heterogeneity on rate of sedimentary O2 consumption reaction

Quantification of soil hotspots and hot-moments is one of the main challenges to understand the variability encountered in soils in terms of respiration activity and trace gas emissions. At the current state of the art, determination of the link between the biological and soil heterogeneity is a challenge. The latter is also a function of the scale at which the phenomena are observed. However this target is difficult given the lack of instrument to measure spatial variability in bacteria activity at high frequency. In order to fill this gap and to improve the current knowledge, our work aim in studying the temporal evolution of oxygen (O2) consumption maps resulting from the addition of DI water, humic acid and glucose. The overall objective of this study is to investigate the link between the spatial average consumption rate and land use and also to trace spatial variability of O2 for a given time point.Peer Reviewe

Comparison of the effectiveness and safety of Clarithromycin and Co-Amoxyclav in acute exacerbation of chronic otitis media : a randomized, open-labeled, phase iv clinical trial

Objective:To compare the effectiveness and safety of Clarithromycin and co-amoxyclav for the treatment of mild to moderate cases of acute exacerbation of chronic otitis media (AECOM).Materials and methods:Adult patients diagnosed with AECOM were screened and patients fulfilling the inclusion criteria were randomized to receive either Clarithromycin (500 mg) twice daily or co-amoxyclav (625 mg) thrice daily orally for 7 days. The primary outcome of this randomized, open-labeled, phase IV clinical trial was clinical success rate at day 14 visit and the secondary outcome was incidence of adverse events (AES). Fifty patients were enrolled : 25 in the Clarithromycin group and 25 in the co-amoxyclav group.Results :  The clinical success rates were 92.7 % in the Clarithromycin group versus 90.2% in the co-amoxyclav group. These rates are comparable, but no statistically significant difference was observed between the groups.Conclusion:The results of this randomized, open-labeled phase IV clinical trial showed that a 7-day course of Clarithromycin is therapeutically comparable to co-amoxyclav in terms of both clinical effectiveness and safety for the treatment of patients with AECOM

‘Green’ synthesis of metals and their oxide nanoparticles: applications for environmental remediation

Abstract In materials science, “green” synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of “green” synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing