scholarly journals Hydrogen peroxide distribution, production, and decay in boreal lakes

2004 ◽  
Vol 61 (8) ◽  
pp. 1520-1527 ◽  
Author(s):  
Petri J Häkkinen ◽  
Alexandre M Anesio ◽  
Wilhelm Granéli
Keyword(s):  
Hydrogen Peroxide ◽  
Water Column ◽  
Decay Rates ◽  
Boreal Lakes ◽  
Chemical Characteristics ◽  
Mixing Depth ◽  
Physical Chemical ◽  
Doc Concentration ◽  
Iron And Manganese

The distribution, production, and decay of hydrogen peroxide (H2O2) were studied in 10 boreal lakes of differing physical–chemical characteristics. Diurnal and vertical fluctuations in H2O2 concentration were followed in the lakes by sampling at six depths three times per day. In addition, incubations of water filtered through 0.2-µ mesh were made under artificial irradiation to study the abiotic production and decay of H2O2. H2O2 concentrations after 8 h of artificial irradiation were significantly correlated with neither absorption coefficients at 320 nm nor with dissolved organic carbon (DOC) concentrations. However, H2O2 concentration increased rapidly with DOC concentration among lakes with DOC concentrations below 10 mg·L–1. The H2O2 concentration after exposure to ultraviolet radiation was positively related to the half-life of H2O2, which in turn was negatively correlated with iron and manganese concentrations (r2 = 0.68 and 0.70, respectively). In situ H2O2 concentrations at the surface of the water column ranged between 30 and 1041 nmol·L–1 and were largely determined by the decay rates of H2O2 and the mixing depth of the water column.

Circulation patterns and eutrophication phenomena in the Thermaikos Gulf

2020 ◽  
Author(s):  
Yannis N. Krestenitis ◽  
Vasilis Kolovoyiannis ◽  
Yannis Androulidakis ◽  
Christos Makris ◽  
Vasilis Baltikas
Keyword(s):  
Water Column ◽  
Marine Ecosystem ◽  
Simulated Data ◽  
Aegean Sea ◽  
Ocean Model ◽  
Biological Parameters ◽  
Chl A ◽  
Physical Chemical ◽  
Circulation Patterns

<p>Thermaikos Gulf, located in the Northwestern Aegean Sea (Greece), is a marine ecosystem of major importance, not only environmentally (as an area of the deep water formation with contribution to the renewal of the North Aegean deep waters), but also due to the various socioeconomic activities associated with the area. Observational and simulated data are used to investigate the evolution of eutrophication events during the last two years in order to evaluate the current (2017-2019) quality state of the seawater in the Gulf. The quality of the marine environment of Thermaikos Gulf was appraised by measuring physical, chemical and biological parameters. Specific physical-chemical characteristics (temperature, salinity, density along with pH and dissolved oxygen) and biological parameters (chl-a and phytoplankton biomass) throughout the water column were evaluated by conducting in situ measurements during the sampling campaigns. Current fields, derived from a high-resolution 3-D ocean model, together with ADCP measurements, are used to describe the major circulation patterns, the river plume dynamics and the renewal pathways of the Gulf. The obtained results are discussed with regards to seasonal and spatial variability, and the water column stratification. Satellite ocean color data were also used to discuss the in-situ findings and confirm “Dirty” Sea and Red Tide phenomena, that were detected and analyzed based on the physical dynamics and especially the renewal patterns of the Gulf. Moreover, we compare these recent findings to respective observations from a previous period (1997 to 2007) to evaluate potential changes in the quality state of the Gulf with respect to meteorological and river discharge conditions.     </p>

scholarly journals VISUAL QUALITY AND PHYSICAL-CHEMICAL CHARACTERISTICS IN POTATO TUBERS TREATED WITH HYDROGEN PEROXIDE

2018 ◽  
Vol 14 (2) ◽  
pp. 149-154
Author(s):  
Rhayf Eduardo Rodrigues ◽  
Marilia Assis dos Santos ◽  
Clarice Aparecida Megguer ◽  
Murilo Alberto dos Santos ◽  
Ana Carolina de Lima Ribeiro ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Visual Quality ◽  
Chemical Characteristics ◽  
Potato Tubers ◽  
Physical Chemical

scholarly journals Photocatalytic Degradation of Pesticides in Natural Water: Effect of Hydrogen Peroxide

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Natividad Miguel ◽  
María P. Ormad ◽  
Rosa Mosteo ◽  
José L. Ovelleiro
Keyword(s):  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Organic Carbon ◽  
Water Effect ◽  
Chemical Parameters ◽  
Physical Chemical ◽  
Doc Concentration ◽  
Chlorine Demand ◽  
Organic Pesticides ◽  
Photocatalytic Processes

The aim of this paper is to evaluate the effectiveness of photocatalytic treatment with titanium dioxide in the degradation of 44 organic pesticides analyzed systematically in the Ebro river basin (Spain). The effect of the addition of hydrogen peroxide in this treatment is studied, and a monitoring of effectiveness of photocatalytic processes is carried out by measurements of physical-chemical parameters of water. The application of photocatalytic treatment with 1 g L−1of TiO2during 30 minutes achieves an average degradation of the studied pesticides of 48%. Chlorine demand, toxicity, and dissolved organic carbon (DOC) concentration of water are reduced. If hydrogen peroxide is added with a concentration of 10 mM, the average degradation of pesticides increases up to 57%, although chlorine demand and toxicity of water increase while DOC concentration remains unchanged with this treatment. The application of either photocatalytic treatments does not produce variations in the physical-chemical parameters of water, such as pH, conductivity, colour, dissolved oxygen, and hardness. The pesticides which are best degraded by photocatalytic treatments are parathion methyl, chlorpyrifos, α-endosulphan, 3,4-dichloroaniline, 4-isopropylaniline, and dicofol while the worst degraded are HCHs, endosulphan-sulphate, heptachlors epoxide, and 4,4′-dichlorobenzophenone.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

Comparison of decay rates of faecal indicator organisms in recreational coastal water and sediment

2002 ◽  
Vol 2 (3) ◽  
pp. 131-138 ◽  
Author(s):  
D.L. Craig ◽  
H.J. Fallowfield ◽  
N.J. Cromar
Keyword(s):  
Water Column ◽  
Coastal Water ◽  
Decay Rates ◽  
Organic Carbon Content ◽  
Indicator Organisms ◽  
Filtration Method ◽  
E Coli ◽  
Water And Sediment ◽  
Increased Risk ◽  
High Organic Carbon Content

A laboratory based microcosm study utilising intact non-sterile sediment cores was undertaken to determine the survival of the faecal indicator organisms Escherichia coli, Enterococcus faecium and somatic coliphage in both recreational coastal water and sediment. Overlying water was inoculated with the test organisms and incubated at 10°C, 20°C or 30°C. E. coli, enterococcus and coliphage were enumerated from the water column and sediment by the membrane filtration method, Enterolert (IDEXX Laboratories) and the double-agar overlay methods respectively on days 0, 1, 2, 7, 14 and 28 following inoculation. It was demonstrated that for all organisms, greater decay (k; d-1) occurred in the water column compared to sediment. Sediment characteristics were found to influence decay, with lowest decay rates observed in sediment consisting of high organic carbon content and small particle size. Decay of E. coli was significantly greater in both the water column and sediment compared with enterococcus and coliphage under all conditions. Decay of enterococcus was found to closely resemble that of coliphage decay. Survival of all organisms was inversely related to temperature, with greatest decay at 30°C. However, increased temperature had a less significant impact on survival of enterococcus and coliphage compared with E. coli. The importance of this study for estimating risk from recreational exposure is great if some pathogenic microorganisms behave similarly to the organisms tested in this study. In particular if survival rates of pathogens are similar to enterococcus and coliphage, then their ability to accumulate in coastal sediment may lead to an increased risk of exposure if these organisms are resuspended into the water column due to natural turbulence or human recreational activity.

Recent trends in nanozymes design: from materials and structures to environmental applications

2021 ◽  
Author(s):  
Camilo A S Ballesteros ◽  
Luiza Mercante ◽  
Augusto Alvarenga ◽  
Murilo Henrique Moreira Facure ◽  
Rodrigo Schneider ◽  
...  
Keyword(s):  
Environmental Applications ◽  
Chemical Characteristics ◽  
Physical Chemical ◽  
Recent Advances ◽  
Technological Advances ◽  
Recent Trends

A large variety of engineered nanostructures possessing enzyme-like activities have been proposed recently, which unique physical-chemical characteristics enable remarkable technological advances. In this review, we survey recent advances on nanozymes...

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