Effects of Cadmium on Bioaccumulation, Bioabsorption, and Photosynthesis in Sarcodia suiae

This study investigated the changes in bioaccumulation, bioabsorption, photosynthesis rate, respiration rate, and photosynthetic pigments (phycoerythrin, phycocyanin, and allophycocyanin) of Sarcodia suiae following cadmium exposure within 24 h. The bioabsorption was significantly higher than the bioaccumulation at all cadmium levels (p < 0.05). The ratios of bioabsorption/bioaccumulation in light and dark bottles were 2.17 and 1.74, respectively, when S. suiae was exposed to 5 Cd2+ mg/L. The chlorophyll a (Chl-a) concentration, oxygen evolution rate (photosynthetic efficiency), and oxygen consumption rate (respiratory efficiency) decreased with increasing bioaccumulation and ambient cadmium levels. The levels of bioaccumulation and bioabsorption in light environments were significantly higher than those in dark environments (p < 0.05). In addition, the ratios of phycoerythrin (PE)/Chl-a, phycocyanin (PC)/Chl-a, and allophycocyanin (APC)/Chl-a were also higher in light bottles compared to dark bottles at all ambient cadmium levels. These results indicated that the photosynthesis of seaweed will increase bioaccumulation and bioabsorption in a cadmium environment.

Oxygen evolution rate in Antarctic filamentous alga Stigeoclonium sp. evaluated by optodes relates to chlorophyll fluorescence parameters (Short Communication)

Photosynthetic reactions of algal communities, the essential component of primary production in polar regions, are strongly dependent on environmental factors. Among them, availability and amount of light in particular parts of growing season are of major importance. In this paper, the response of the photosynthetic processes of a filamentous fresh-water alga to photosynthetically active radiation (PAR) was studied by two approaches. The simultaneous measurements of the effective quantum yield (FPSII) and oxygen evolution rate (OER) at stepwise increasing photosynthetically active radiation provided data for beneficial correlation analysis of the FPSII to OER relationship in a wide range of PAR. In this study, the culture of filamentous alga Stigeoclonium sp. was analyzed. The linear relationship between FPSII and OER was found for the low PAR (the range of 0 – 200 mmol.m-2.s-1). At high PAR levels (200 – 1000 mmol.m-2.s-1) another linear relationship with different slope was found. The approach combining the fluorometric and oxymetric method might be used for calibration of data in follow up studies and, consequently for evaluation of photosynthetic rates (O2 evolution) from chlorophyll fluorescence data.

Allelopathic Inhibitory Effects of the Dried Macroalga Ulva pertusa on the Photosynthetic Activities of Red Tide-Causing Microalga Skeletonema costatum

Allelopathic effects of dried macroalgaUlva pertusa(Chlorophyta) on photosynthesis of the microalgaeSkeletonema costatum(Bacillariophyta) were evaluated using coexistence culture systems.S. costatumwas cultured with different biomass of driedU. pertusaunder controlled laboratory conditions for three days. The chlorophylla(Chla) fluorescence transient O-J-I-P curve coupled with its specific parameters inS. costatumwas established. The oxygen evolution rate was measured, the Chlafluorescence transients were recorded in vivo at high time resolution and analyzed according to the JIP-test which can quantify photosystem II activity. A clear dose-dependent relationships were observed between the dried biomass ofU. pertusaand its inhibitory effect onS. costatum.The rate of light-saturated maximum photosynthetic oxygen evolution (Pmax) was markedly decreased by different biomass of driedU. pertusa, while dark respiration rate (Rd) was increased. A decrease in the O-J-I-P curve expressed as Chlafluorescence intensity along with its specific parameters were observed, which was also time-dependent. The main photosynthetic inhibitory targets of the macroalga on the microalga, according to oxygen evolution rate and the JIP-test, can be expressed as, the damage to the oxygen-evolving complex, a decrease in the number of active reaction centers and the blocking of the electron transport chain. The results of the present study suggest that dried fragments ofU. pertusaeffectively inhibit photosynthesis inS. costatum.

The Influence of the Ammonolysis Temperature on the Photocatalytic Activity ofβ-TaON

Phase-pure tantalum oxynitride (β-TaON) powders were synthesized by thermal ammonolysis of Ta2O5powders. X-ray diffraction revealed an enlargement of the unit cell and an increase of the crystallite size with increasing ammonolysis temperature. Scanning electron microscopy showed reduced particle sizes forβ-TaON synthesized at 800 and compared to the precursor oxide. With increasing nitridation temperature the Brunauer-Emmett-Teller surface area was reduced and the nitrogen content increased. UV-Vis spectroscopy showed a bandgap energy of 2.6–2.4 eV. The highest oxygen evolution rate of 220 μmol·g−1·h−1was achieved forβ-TaON synthesized at . The factors determining the photocatalytic activity ofβ-TaON powders were found to be the specific surface area and defects in theβ-TaON.

Dimensional modelling of the fuel outgassing phenomenon: Improving flammability assessment of aircraft fuel tanks

Fuel outgassing (oxygen evolution) within aircraft fuel tanks presents a serious flammability hazard. Time constants representing oxygen transfer rate, from the fuel into a tank’s ullage, are used to model the effect of outgassing on tank flammability. These time constants are specific to a single aircraft type and flight envelope and may not accurately represent fuel outgassing behaviour for other aircraft types with differing fuel tank configurations and flight envelopes. To improve current modelling practice for more accurate flammability analysis dimensional modelling has been used to determine the rate of oxygen evolution from Jet A-1 fuel in an aircraft fuel tank. Measurements of oxygen evolution rate, made on a dimensionally similar model, have been projected to an A320 aircraft. The evolution of oxygen from the fuel was found to increase monotonically with time. Fitting the test data with an inverse-exponential function enabled oxygen release rate and its associated time constant (τ) to be determined. Dimensional modelling of aviation fuel outgassing using model fuel tanks will enable oxygen evolution rate from aviation fuel to be determined for a wide range of aircraft fuel tank configurations and environments without the need for flight testing. In turn the accuracy of flammability assessment of aircraft fuel tanks will be improved and significant cost savings made.

2-Alkylsulphanyl-4-pyridinecarbothioamides — inhibitors of oxygen evolution in freshwater alga Chlorella vulgaris

The inhibition of the oxygen evolution rate (OER) in Chlorella vulgaris by 2-alkylsulphanyl-4-pyridinecarbothioamides (APCTs; alkyl = methyl up to hexadecyl) was studied. APCTs were found to inhibit photosynthetic electron transport (PET) which resulted in the inhibition of OER in algae. The inhibitory activity of APCTs was highly dependent on the alkyl chain length of the 2-alkylsulphanyl substituent and the corresponding dependence showed a bilinear course with the decyl derivative as being the most active inhibitor. Using EPR spectroscopy, the site of APCT action in the algal photosynthetic apparatus was determined. It was confirmed that APCT interacted mainly with the D. intermediate, i.e. with tyrosine radical (TyrD) occurring at the 161st position in D2 protein which is situated on the donor side of photosystem 2.