Chlorophyll derivatives/MXene hybrids for photocatalytic hydrogen evolution: Dependence of performance on the central coordinating metals

Development of efficient photocatalytic hydrogen evolution reaction (HER) with illumination of visible light is challenging. In this work, five chlorophyll derivatives (M-Chls; M = H₂/Cu/Ni/Co/Zn) with different central ions in its cyclic tetrapyrrole ring including free base, copper, nickel, cobalt, and zinc were synthesized and employed as the effective visible-light harvester for efficient HER. In addition, two-dimensional (2D) noble metal-free co-catalyst Ti₃C₂T_x MXene was used as an excellent electron capturer due to its outstanding conductivity property. These M-Chls are modified on the surface of Ti₃C₂T_x MXene with 2D accordion-like morphology by means of a simple deposition process to form noble metal-free Chl/Ti₃C₂T_x-based photocatalysts for HER. It is found that the best HER performance as high as 49 μmol/h/g_cat was achieved with the Co-Chl@Ti₃C₂T_x hybrid, which was much higher than those of other M-Chl@Ti₃C₂T_x composites. This research provides a specific way to synthesize low-cost and environmentally friendly natural Chls for developing highly efficient photocatalytic HER through molecular engineering.     

Trends of phosphorus, nitrogen and chlorophyll a concentrations in Finnish rivers and lakes in 1975–2000

During recent decades the amounts of nutrients discharged to Finnish surface waters have markedly decreased. This has been achieved by considerable investments in water protection, which were made mainly to improve municipal and industrial wastewater purification. We investigated whether these water protection measures have decreased phosphorus and nitrogen concentrations in Finnish rivers and lakes. In addition, possible trends in chlorophyll a concentrations in lakes were studied. The data consisted of a total of over 68 000 monitoring results of 22 rivers and 173 lakes (or sub-basins of lakes) with different types of catchment areas. The study period covered the years 1975–2000 and the non-parametric Kendall Tau b and Seasonal Kendall tests were applied for detecting trends. Decreasing nutrient concentration trends were typical in many lakes and rivers earlier polluted by municipal and industrial wastewaters. Increasing nutrient concentration trends were common in smaller rivers and lakes receiving diffuse loading from agriculture. The results show that the investments directed towards wastewater purification have effectively improved the quality of Finnish inland waters. However, no clear effects of decreasing non-point loading were found. Thus, more effective measures should be directed towards decreasing non-point source loading.     

On the issue of limiting nutrient and predictions of cyanobacteria in aquatic systems

This study aims at bridging the gap between freshwater and marine eutrophication studies by presenting (1) a cross-system analysis of the relationship between chlorophyll and the total nitrogen (TN) to total phosphorus (TP) ratio (2) a general model to predict concentrations of cyanobacteria from data on TP, the TN/TP ratio, salinity and temperature, and (3) a general trophic level classification for aquatic systems based on chlorophyll classes (for oligo-, meso-, eu- and hypertrophic systems). The data compiled in this study concerns more than 500 lakes and coastal areas covering a very wide domain in terms of nutrient concentrations and salinity. There was no simple relationship between the TN/TP ratio and empirical chlorophyll concentrations or concentrations of cyanobacteria. Variations in TP rather than TN generally seem to be more important to predict variations among systems in chlorophyll-a and cyanobacteria. Different "bioavailable" forms of the nutrients (DIN, DIP, phosphate, nitrate, etc.) have been shown to have very high coefficients of variation (CV), which means that many samples are needed to obtain reliable empirical data which are necessary in models aiming for high predictive power and practical usefulness.     

The F684/F735 chlorophyll fluorescence ratio: a potential tool for rapid detection and determination of herbicide phytotoxicity in algae

The use of herbicides constitutes the principal method of weed control but the introduction of these compounds into the aquatic environment (primarily through runoff) may have severe consequences for non-target plants. In this study, we describe a sensitive and inexpensive method for detection of photosynthesis-inhibiting herbicides, based on chlorophyll (Chl) fluorescence emission. Algae exhibited a Chl fluorescence signature with two maxima around 684 and 735 nm, correlated with the total Chl content of the algal suspension. The ratio of these two maxima (i.e. F684/F735) can be used as an indicator of stress in the photosynthetic apparatus, and thus represents a very simple method for in vivo evaluation of the health status of algae. Determination of the F684/F735 fluorescence ratio revealed the presence and phytotoxicity of atrazine, metribuzin, terbuthylazine, diuron, DCPMU, DCPU and paraquat. The toxic effect of these pollutants was estimated by monitoring the increase in the F684/F735 value, which reflects photosystem II and photosystem I photochemistry. We observed a drastic increase in the magnitude of this ratio, correlating quantitatively with herbicide concentration and corresponding to a decline in algal photosynthetic activity. For the tested herbicides affecting photosynthetic electron transport, the magnitude of the effect was as follows: diuron= DCPMU > metribuzin > atrazine > terbuthylazine > paraquat > DCPU. The F684/F735 Chl fluorescence ratio thus gives toxicity responses which compare favourably with tests such as the algal growth inhibition test, and could therefore be used to detect the presence and phytotoxicity of herbicides in aquatic environments.     

Investigation of Heat‐Induced Degradation of Virgin Olive Oil Using Front Face Fluorescence Spectroscopy and Chemometric Analysis

A simple setup using a 365‐nm light‐emitting diode coupled to a USB spectrometer through an optical fiber, in a front‐face fluorescence configuration, was used to investigate the heat‐induced deterioration of virgin olive oil at different heating temperatures and times. The samples were heated for 30, 60, 120 and 180 min for every temperature setting of 140, 160 and 180 °C, respectively. Two important results are reported in this article. First, a neo‐formed compound around 665 nm due to the degradation of chlorophyll was observed. This new peak was attributed to pyropheophytins. The second result showed an important rise of the peak around 489 nm, which corresponded to the oxidation products. The correlation obtained between the peroxide value and the 489 nm peak using principal component analysis revealed the mechanism of the oxidation process. It further showed that the peak around 489 nm is a direct consequence of the degradation of hydroperoxide.     

Potential of two cardoon varieties to produce biomass and oil under reduced irrigation and weed control inputs

Cardoon (Cynara cardunculus L.) is an important perennial energy plant, which may produce sufficient biomass under reduced inputs. A 4-years field study was conducted in northern Greece and was repeated for three years in central Greece to determine the productivity of two cardoon varieties (‘Bianco Avorio’ and ‘C12’) under different water (irrigated or non-irrigated) and weed control (weedy or weed-free) conditions. In northern Greece, the density of weeds grown with cardoon increased as years went by, but in central Greece decreased. The absence of irrigation and the presence of weeds significantly reduced cardoon dry biomass, seed and oil yields, especially in the first two years of cultivation. In both environments, irrigated with 90 mm cardoon achieved 22–42% and 35–42% greater dry biomass and seed yield, respectively, than achieved the non-irrigated crop. In weedy cardoon, the dry biomass or seed yields reductions were 33–66% or 41–64%, respectively, in central Greece and 21–95% or 8–99%, respectively, in northern Greece. In central Greece cardoon productivity increased as years went by, but in northern Greece decreased. Generally, the cv. C12 was more productive than the cv. Bianco Avorio. Conclusively, the cardoon cv. C12 could provide satisfactory dry biomass, seed and oil yields for energy use in semi-arid Mediterranean fields, without irrigation or weed control inputs, on condition that they have been successfully established the first year. However, cardoon should be irrigated and weeded in order to provide sufficient yields.     

Hemp seed oil: Minor components and oil quality

Owing to its high content of omega‐6/omega‐3 fatty acids and bioactive minor components with antioxidant activities, hemp seed oil is now recognized for its health benefits by a large number of consumers. This paper primarily discusses the profile of minor components in hemp seed oil and their beneficial and adverse effects on oil quality. While tocopherols, polyphenols and phytosterols prevent oxidative deterioration of hemp seed oil, the high amount of chlorophyll can be detrimental to oil quality.     

Assessment of production efficiency,physicochemical properties and storage stability of spray‐dried chlorophyllide,a natural food colourant,using gum Arabic,maltodextrin and soy protein isolate‐based carrier systems

The aim of this research was to study spray drying as potential action to protect chlorophyllide from environmental conditions for shelf‐life extension and characterisation of the powders. Six formulations were prepared with 7.5 and 10 g of carrier agents [gum Arabic (GA), maltodextrin (MA) and soybean protein isolate (SPI)]/100 mL of chlorophyllide solutions. The powders were evaluated for morphological characteristics (SEM), particle size, water activity, moisture, density, hygroscopicity, cold water solubility, sorption isotherms, colour and stability, during 90 days. All the powders were highly soluble, with solubility values around 97%. A significant lower hygroscopicity was observed for GA powders, whilst the lower X_m values obtained by GAB equation fitting of the sorption isotherms was observed for the 7.5 g MA/100 mL samples. All formulations, but the 1 (7.5 g SPI/100 mL of chlorophyllide), provided excellent stability to the chlorophyllide during 90 days of storage even at room temperature.     

Rapid evaluation of olive oil quality by NIR reflectance spectroscopy

NIR spectroscopy calibrations have been developed for a range of quality parameters in olive oil, including FFA, PV, polyphenol content, induction time, chlorophyll, and the major FA. A set of 216 olive oil samples from throughout the Australian olive-growing areas were used to provide a representative range of quality. The variation in the oils tested virtually covered the range of the chemical standard limits described by the International Olive Oil Council. A FOSS NIRSystems^® 6500 spectrophotometer with a liquid cell holder was used. Multiple correlation coefficients squared (R ²) for minor components stearic acid (0.86), and linolenic acid (0.85) were relatively low because the concentration range is very narrow compared with the reproducibility of the reference method. However, the major FA, oleic (0.99) and linoleic (1.00), FFA (0.97), and chlorophyll (0.98) provided high levels of accuracy. All of the parameters measured were sufficiently accurate for routine screening of olive oil.     

三种氮素营养快速诊断方法在油菜上的适宜性分析

通过大田试验研究SPAD仪（叶绿素仪）法、硝酸盐反射仪法和光谱仪法在油菜氮素营养快速诊断上的适宜性。试验设施氮0、60、120、180、240、300和400kg/hm2处理,在八叶期、十叶期和蕾薹期对各处理SPAD值、冠层归一化植被指数（NDVI值）和硝酸盐含量进行检测,并测定各时期油菜生物量和收获期籽粒产量。对不同施氮量下的油菜产量进行显著性检验及方程拟合,并对三种诊断方法各测定指标与氮肥用量、籽粒产量进行相关分析。结果表明,油菜施氮量与籽粒产量具有较好的相关关系,满足进行氮素营养快速诊断要求。三种诊断方法中,硝酸盐反射仪法能在一定程度上反映油菜氮素营养状况,但受油菜生理特性（苗期生物量小、蕾薹期氮素奢侈性吸收等）影响,诊断结果的可信度和稳定性不高。光谱仪法比较适宜于油菜蕾薹期氮素营养诊断,但存在追肥时期过晚、操作不方便等缺点。综合分析认为,SPAD仪法诊断结果稳定,并且具有快速、简便、低耗等优点,适合于油菜氮素营养快速诊断。