Preparation of zeolite NaA for CO_2 capture from nickel laterite residue

Zeolite NaA was successfully prepared from nickel laterite residue for the first time via a fusion-hydrothermal procedure. The structure and morphology of the as-synthesized zeolite NaA were characterized with a range of experimental techniques, such as X-ray diffraction, scanning electronic microscopy, and infrared spectroscopy. It was revealed that the structures of the produced zeolites were dependent on the molar ratios of the reactants and hydrothermal reaction conditions, so the synthesis conditions were optimized to obtain pure zeolite NaA. Adsorption of nitrogen and carbon dioxide on the prepared zeolite NaA was also measured and analyzed. The results showed that zeolite NaA could be prepared with reasonable purity, it had physicochemical properties comparable with zeolite NaA made from other methods, and it had excellent gas adsorption properties, thus demonstrating that zeolite NaA could be prepared from nickel laterite residue.

Quantification of Photosynthetic Pigments in Neopyropia yezoensis Using Hyperspectral Imagery

Phycobilisomes and chlorophyll-a(Chla)play important roles in the photosynthetic physiology of red macroalgae and serve as the primary light-harvesting antennae and reaction center for photosystem Ⅱ.Neopyropia is an economically important red macroalga widely cultivated in East Asian countries.The contents and ratios of 3 main phycobiliproteins and Chla are visible traits to evaluate its commercial quality.The traditional analytical methods used for measuring these components have several limitations.Therefore,a high-throughput,nondestructive,optical method based on hyperspectral imaging technology was developed for phenotyping the pigments phycoerythrin(PE),phycocyanin(PC),allophycocyanin(APC),and Chla in Neopyropia thalli in this study.The average spectra from the region of interest were collected at wavelengths ranging from 400 to 1000 nm using a hyperspectral camera.Following different preprocessing methods,2 machine learning methods,partial least squares regression(PLSR)and support vector machine regression(SVR),were performed to establish the best prediction models for PE,PC,APC,and Chla contents.The prediction results showed that the PLSR model performed the best for PE(R_(Test^(2))=0.96,MAPE=8.31%,RPD=5.21)and the SVR model performed the best for PC(R_(Test^(2))=0.94,MAPE=7.18%,RPD=4.16)and APC(R_(Test^(2))=0.84,MAPE=18.25%,RPD=2.53).Two models(PLSR and SVR)performed almost the same for Chla(PLSR:R_(Test^(2))=0.92,MAPE=12.77%,RPD=3.61;SVR:R_(Test^(2))=0.93,MAPE=13.51%,RPD=3.60).Further validation of the optimal models was performed using field-collected samples,and the result demonstrated satisfactory robustness and accuracy.The distribution of PE,PC,APC,and Chla contents within a thallus was visualized according to the optimal prediction models.The results showed that hyperspectral imaging technology was effective for fast,accurate,and noninvasive phenotyping of the PE,PC,APC,and Chla contents of Neopyropia in situ.This could benefit the efficiency of macroalgae breeding,phenomics research,and other related applications.

Biogenic silica contents of Lake Qinghai sediments and its environmental significance

Changes in the levels ofbiogenic silica （BSi%） in lake sediments have been widely used in order to study lake productivity and palaeoclimatic changes. However, the provenance of biogenic silica （BSi） needs to be investigated for each lake, especially for large lakes, as does the relationship between levels of BSi and relevant environmental factors. In this study, we measured the percentage of BSi contained in lake sediments, river sediments, and surface soils within the Lake Qinghai catchment, and compared the quantities and shapes of diatoms and phytoliths before and after the extraction processes. The results suggest that BSi in lake sediments is primarily derived from endogenous diatoms; therefore, BSi levels can be used to reflect the changes in primary productivity within the lake. Further comparisons showed that on long-term timescales, the variations in BSi% are generally consistent with those in total organic carbon （TOC） and grain size, reflecting the dominant impacts of precipitation on primary productivity in Lake Qinghai. On short-term timescales, however, the relationship between BSi% and TOC and that between BSi% and grain size are not clear or stable. For example, BSi% sometimes covaried with grain size, but it was sometimes out of phase with or even inversely related to grain size. We speculate that both climate and environmental processes, such as the dilution effect, influence short-term BSi% and its related environmental significance. As a result, BSi% should be used selectively as an indicator of climatic changes on different time scales.

Discrepancy in photosynthetic responses of the red alga Pyropia yezoensis to dehydration stresses under exposure to desiccation,high salinity,and high mannitol concentration

Macroalgae that inhabit intertidal zones are exposed to the air for several hours during low tide and must endure desiccation and high variations in temperature, light intensity, and salinity. Pyropia yezoensis (Rhodophyta, Bangiales), a typical intertidal red macroalga that is commercially cultivated in the northwestern Pacific Ocean, was investigated under different dehydration stresses of desiccation, high salinity, and high mannitol concentration. Using chlorophyll fluorescence imaging, photosynthetic activities of P. yezoensis thalli were analyzed using six parameters derived from quenching curves and rapid light curves. A distinct discrepancy was revealed in photosynthetic responses to different dehydration stresses. Dehydration caused by exposure to air resulted in rapid decreases in photosynthetic activities, which were always lower than two other stresses at the same water loss (WL) level. High salinity only reduced photosynthesis significantly at its maximum WL of 40% but maintained a relatively stable maximum quantum yield of photosystem II (PSII) (Fv/Fm). High mannitol concentration induced maximum WL of 20% for a longer time (60 min) than the other two treatments and caused no adverse influences on the six parameters at different WL except for a significant decrease in non-photochemical quenching (NPQ) at 20% WL. Illustrated by chlorophyll fluorescence images, severe spatial heterogeneities were induced by desiccation with lower values in the upper parts than the middle or basal parts of the thalli. The NPQ and rETRmax (maximum relative electron transport rate) demonstrated clear distinctions for evaluating photosynthetic responses, indicating their sensitivity and applicability. The findings of this study indicated that the natural dehydration of exposure to air results in stronger and more heterogeneous effects than those of high salinity or high mannitol concentration.