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An analytical method for the determination of 11 water-soluble organic acids (lactic acid, fumaric acid, malic acid, tartaric acid, coumaric acid, gallic acid, citric acid, vanillic acid, ferulic acid, and neochlorogenic acid) in plants by online solid-phase extraction (SPE) coupled with high performance liquid chromatography-quadrupole orbitrap high resolution mass spectrometry (HPLC-Q-Orbitrap-HRMS) was developed. Samples were homogenized, ultrasonically extracted, filtrated, diluted, and purified on an Oasis MAX column (20 mm × 2.1 mm, 30 μm). The analytes were separated on separated on a BEH C18 AX column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase consisting of 0.9% formic acid solution containing 10 mmol/L ammonium formate and 0.9% formic acid in acetonitrile. The MS analysis was performed by full MS/dd-MS2 scanning in the negative ion mode. Quantitation was performed using the internal standard method. Under the optimum conditions, the 11 organic acids were well separated within 9 minutes, and the accurate mass deviation for each compound was less than 5.00 × 10-6. The developed method showed good linearity in the range of 1–100 μg/L with correlation coefficients (R2) greater than 0.999. The limits of detection (LOD) and quantification (LOQ) ranged from 0.1 to 3.2 μg/kg and from 0.3 to 9.6 μg/kg, respectively. The average recoveries of the 11 organic acids in Euryale ferox seeds and pakchoi spiked at two concentration levels were 92.2%–111% and 94.2%–110% with intraday relative standard deviations (RSDs) of 1.4%–4.9% and 0.8%–5.6%, respectively. The method was successfully applied to the analysis of organic acids in white radish, carrot, potato, pakchoi, banana, pear, grape, and E. ferox seeds. This method is simple, fast, accurate, and reliable, and can be used as a new approach for the rapid analysis of water-soluble organic acids in plants.

The present study focuses on an efficient Cr(VI)-reducing bacterial strain (CR-2) isolated from an abandoned chromate plant in Qinghai Province, China. CR-2 was confirmed as Lysinibacillus cavernae using 16S rRNA gene sequencing. CR-2 could survive at 500 mg L−1 Cr(VI) and effectively reduce Cr(VI) at concentrations of <50 mg L−1, a pH of 5–9, a temperature of 20–40 °C, and a salinity of 5–15 g L−1. According to the Box–Behnken experimental design, the maximum Cr(VI) removal efficiency by L. cavernae CR-2 was 76.21% under optimum conditions, which comprised a pH of 6.68, a temperature of 28.90 °C, and a salinity of 9.85 g L−1. With regard to Cr(VI) reduction mediated by L. cavernae CR-2, enhancement in efficiency was observed in the presence of Cu2+ and Ca2+, while significant inhibition in the reduction capacity occurred upon exposure to Mg2+, Ba2+, Ni2+, Pb2+, or Cd2+. Moreover, L. cavernae CR-2 tends to use glucose as an electron donor for the reduction of Cr(VI). Results of cell fraction separation and degeneration indicated that the Cr(VI) removal was primarily due to the reduction of Cr(VI) via chromium reductase in the cytoplasm. In addition, bioanalysis of L. cavernae CR-2 by SEM-EDS and TEM-EDS suggested that Cr was distributed both on the surface and in the cell cytoplasm. FT-IR analyses established that multiple functional groups (hydroxyl, carbonyl, amide, amino, and aldehyde groups) participated in the Cr(VI) biosorption on the cell surface. XPS and HPLC also showed that the Cr(III) end-products could be present as Cr(III) hydroxides or as organic–Cr(III) complexes. This study yields insights into the Cr(VI) bioreduction mechanism of L. cavernae CR-2. [ABSTRACT FROM AUTHOR]

Bioreduction of Cr(VI) is an efficient and environmentally friendly remediation method. In this study, we isolated and screened a strain of Penicillium rubens LR6 that could tolerate to Cr(VI) and investigated its mechanism for removing Cr(VI). We ascertained the factors affecting the ability of strain to remove Cr(VI) through batch experiments. The results revealed that the strain could effectively remove high concentrations of Cr(VI) and exhibit excellent removal efficiency under different environmental conditions. The removal of Cr(VI) by the strain could be accurately explained by the exponential decay equation, where approximately 9.45% of the Cr was immobilized on the microorganisms. We further investigated the ability of different cell fractions to remove Cr(VI) and found that bioreduction was the primary mechanism involved. This was supported by SEM and TEM analyses, which showed the presence of Cr on the surface and inside the cells. Additionally, XPS analysis confirmed the presence of both Cr(VI) and Cr(III) on the cell surface, and FTIR analysis suggested the involvement of amino, carboxyl, and hydroxyl groups in the reduction and fixation of Cr(VI) on the cell surface. The findings offer a novel technique for bioremediation of Cr(VI)-contaminated wastewater in weakly acidic to weakly alkaline and high salinity environments, providing potential solutions for remediating chromium-contaminated environments. [ABSTRACT FROM AUTHOR]

In this paper, a tesla-shaped emitter is proposed based on the structure of the "tesla valve" as the source of inspiration, so that the water flow in the channel would produce a variety of energy dissipation phenomena, such as diversion, hedging, and mixing, to explore the hydraulic performance and energy dissipation mechanism of the tesla-shaped emitter. The channel structure parameters were taken as factors, and 16 groups of orthogonal tests were arranged. Based on CFD technology, the pressure–flow relationship curve slope, flow ratio between the main channel and secondary channel, flow field, and head loss of the emitter were calculated and analyzed for different combinations of structural parameters. Based on a significance level α = 0.05 test, the main channel inlet section length (L3) had a significant impact on the curve slope, and the secondary channel length (L1) and main channel inlet section length (L3) had a significant impact on the flow. The multiple linear regression mathematical models between the channel structure parameters and the curve slope and the flow were constructed. The larger the ratio between the main channel and the secondary channel flow, the better the hydraulic performance of the emitter. The channel unit loss coefficient increased linearly with the increase of the emitter inlet pressure, and its value ranged from 4.5769 to 8.1716, with an excellent energy dissipation effect. The hedge mixing of the water flow was the core of the energy dissipation of the tesla-shaped emitter. By appropriately increasing the inlet size of the main channel and other elements to increase the main channel flow and optimize the flow ratio between the main channel and the secondary channel, the mixing was improved, which consequently improved the hydraulic performance of the emitter. [ABSTRACT FROM AUTHOR]