Depthwise oxygen profile at different times of day in a fishpond (pond 9) where phyto-plankton bloom was there was alsoshow by Ali. His observations are shown in Fig. 8. It isinteresting to see that at dawn while there was minimum oxygenin the pond (see also Ali's temperature date) the maximum DOwas not at the surface but below (cf metalimnetic maximum forstratified lakes, Fig. 4), but as the day progresses, towardsafternoon a clear supersaturation pattern develops in the pond,with a DO minimum of 6 mg/L (28°C) at the bottom and a DOmaximum of 15 mg/L (34°C) at 14.00 hrs. What is the effect offluctuating DO in fish growth? Tsadik (1984) studied the effectof fluctuating DO on Oreochromis niloticus and found that fluctuatingDO reduces growth rate almost close to that caused bylow DO itself (1 mg/L). Thus the DO changes will have greatinfluence on the fish stocked in the pond. See also Wickins(1981)
Respiration of fauna and flora; decomposition of organic matter,reduction due to other gases - gases such as methane, CO2 andothers which accumulate in the bottom bubble up and wash out theoxygen dissolved in water (cf. excess CO2 released through waterin the volcanic lake in Cameroun in 1986, release of oxygen fromsuper-saturated surface waters - when upper waters full with O2warm up the upper waters become supersaturated and release O2 tothe air, inflow of subterranean waters of low O2 content (this isnegligible under fish pond conditions), presence of iron - oxidationof iron to form soluble ferric hydrate consumes oxygenin iron-rich waters.
Bacteriopheophytin, the magnesium-free base of bacteriochlorophyll, undergoes reversible one-electron reduction in organic solvents to yield an anionic free radical with characteristic optical and electron spin resonance spectra. The reduction potential of bacteriopheophytin, E1/2 approximately --0.55 V against a normal hydrogen electrode, compared to E1/2 approximately --0.85 V for bacteriochlorophyll, renders it a likely electron acceptor in the primary charge separation of photosynthesis. Comparison of these data with picosecond optical changes recently observed upon pulsed laser excitation of bacterial reaction centers leads us to propose that bacteriopheophytin is indeed a transient electron acceptor and that the primary charge separation of bacterial photosynthesis occurs between the bacteriochlorophyll complex P870 and bacteriopheophytin to yield the radicals of the oxidized chlorophyll dimer cation and reduced pheophytin anion.
All materials were deposited by drop casting on glassy carbon electrode (CH Instruments, Inc.) and the current of the voltammograms is normalized by the geometric area (~7 × 10−2 cm2) of the glassy carbon. An Ag/Ag+ (0.1 m) electrode in acetonitrile and a platinum wire were used as reference and counter electrode, respectively. The reference electrode was calibrated using the well-known reduction oxidation signals of ferrocene (FCN) (Figure S1). Potentials in the voltammograms are corrected to NHE.
Carbon dioxide (CO2) is one of the main gases produced by human activity and is responsible for the green house effect. Numerous routes for CO2 capture and reduction are currently under investigation. Another approach to mitigate the CO2 content in the atmosphere is to convert it into useful species such as hydrocarbon molecules that can be used for fuel. In this view, copper is one of the most interesting catalyst materials for CO2 reduction due to its remarkable ability to generate hydrocarbon fuels. However, its utilization as an effective catalyst for CO2 reduction is hampered by its oxidation and relatively high voltages. We have fabricated hybrid materials for CO2 reduction by combining the activity of copper and the conductivity of reduced graphene oxide (rGO). Cu nanoparticles (CuNPs) deposited on rGO have demonstrated higher current density and lower overpotential compared to other copper-based electrodes that we have tested. The CuNPs on rGO also exhibit better stability, preserving their catalytic activity without degradation for several hours.
For oxidative phosphorylation the electrons come from hydrocarbon and carbohydrate structures, whereas in photosynthesis, the electrons have to be energized in the magnesium center of chlorophylls.