[Determination of trace selenium in plants by hydride generation atomic fluorescence spectrometry with program temperature-controlled graphite digestion].

Discussed several methods of pretreatment for the determination of selenium were discussed, and a program temperature-controlled graphite digestion method was developed to digest 5 kinds of representative standard plant samples of citrus leaves, tea, cabbage leaves, shrubs and rice. The effect of the pretreatment method of digestion solution, digestion temperature and digestion time on the extraction of selenium was investigated in detail. The instrumental working parameters were optimized. For the reaction conditions of hydride generation atomic fluorescence spectrometry (HG-AFS), the effect of the concentration of KBH4 and HCl on the determination of selenium was emphasized. Not only the effect of the concentration of carrier flow HCl was considered, but also the effect of the concentration of sample HCl on the determination of selenium was studied. The best method for determination of trace selenium in plant samples by atomic fluorescence spectrometry with program temperature-controlled graphite digestion was established. Results indicated that the recovery of the method of selenium was 87.1% - 106.2%, the detection limit was 0.018 microg x L(-1) and the relative standard deviation (RSD) was less than 6.0%. In the range of 0-10 microg x L(-1) (low standard) and 0-100 microg x L(-1) (high standard) fluorescence was linearly related to the concentration of selenium, the coefficient of r was 0.9999 and r was 0.9997. Therefore, this method has wide linear range, high sensitivity, low detection limit and good stability, which was very suitable for the determination of trace selenium of plant. And the method was of easy and safe operation, strong practicability, low cost, and low toxicity of chemicals used, so it can be used as a routine analysis method in general laboratory.

Hydrogel-assisted microfluidic spinning of stretchable fibers via fluidic and interfacial self-adaptations.

Stretchable polymeric fibers have enormous potential, but their production requires rigorous environmental controls and considerable resource consumption. It's also challenging for elastic polymers with high performance but poor spinnability, such as silicones like polydimethylsiloxane and Ecoflex. We present a hydrogel-assisted microfluidic spinning (HAMS) method to address these challenges by encapsulating their prepolymers within arbitrarily long, protective, and sacrificable hydrogel fibers. By designing simple apparatuses and manipulating the fluidic and interfacial self-adaptations of oil/water flows, we successfully produce fibers with widely controllable diameter (0.04 to 3.70 millimeters), notable length, high quality (e.g., smooth surface, whole-length uniformity, and rounded section), and remarkable stretchability (up to 1300%) regardless of spinnability. Uniquely, this method allows an easy, effective, and controllable reshaping production of helical fibers with exceptional stretchability and mechanical compliance. We deeply reveal the mechanisms in producing these fibers and demonstrate their potential as textile components, optoelectronic devices, and actuators. The HAMS method would be a powerful tool for mass-producing high-quality stretchable fibers.

Dissolved biochar fractions and solid biochar particles inhibit soil acidification induced by nitrification through different mechanisms.

Biochar can inhibit soil acidification by decreasing the H+ input from nitrification and improving soil pH buffering capacity (pHBC). However, biochar is a complex material and the roles of its different components in inhibiting soil acidification induced by nitrification remain unclear. To address this knowledge gap, dissolved biochar fractions (DBC) and solid biochar particles (SBC) were separated and mixed thoroughly with an amended Ultisol. Following a urea addition, the soils were subjected to an incubation study. The results showed that both the DBC and SBC inhibited soil acidification by nitrification. The DBC inhibited soil acidification by decreasing the H+ input from nitrification, while SBC enhanced the soil pHBC. The DBC from peanut straw biochar (PBC) and rice straw biochar (RBC) decreased the H+ release by 16 % and 18 % at the end of incubation. The decrease in H+ release was attributed to the inhibition of soil nitrification and net mineralization caused by the toxicity of the phenols in DBC to soil bacteria. The abundance of ammonia-oxidizing bacteria (AOB) and total bacteria decreased by >60 % in the treatments with DBC. The opposite effects were observed in the treatments with SBC. Soil pHBC increased by 7 % and 19 % after the application of solid RBC and PBC particles, respectively. The abundance of carboxyl on the surface of SBC was mainly responsible for the increase in soil pHBC. Generally, the mixed application of DBC and SBC was more effective at inhibiting soil acidification than their individual applications. The negative impacts of dissolved biochar components on soil microorganisms need to be closely monitored.

Nitrite stimulates HONO and NOx but not N2O emissions in Chinese agricultural soils during nitrification.

The long-lived greenhouse gas nitrous oxide (N2O) and short-lived reactive nitrogen (Nr) gases such as ammonia (NH3), nitrous acid (HONO), and nitrogen oxides (NOx) are produced and emitted from fertilized soils and play a critical role for climate warming and air quality. However, only few studies have quantified the production and emission potentials for long- and short-lived gaseous nitrogen (N) species simultaneously in agricultural soils. To link the gaseous N species to intermediate N compounds [ammonium (NH4+), hydroxylamine (NH2OH), and nitrite (NO2-)] and estimate their temperature change potential, ex-situ dry-out experiments were conducted with three Chinese agricultural soils. We found that HONO and NOx (NO + NO2) emissions mainly depend on NO2-, while NH3 and N2O emissions are stimulated by NH4+ and NH2OH, respectively. Addition of 3,4-dimethylpyrazole phosphate (DMPP) and acetylene significantly reduced HONO and NOx emissions, while NH3 emissions were significantly enhanced in an alkaline Fluvo-aquic soil. These results suggested that ammonia-oxidizing bacteria (AOB) and complete ammonia-oxidizing bacteria (comammox Nitrospira) dominate HONO and NOx emissions in the alkaline Fluvo-aquic soil, while ammonia-oxidizing archaea (AOA) are dominant in the acidic Mollisol. DMPP effectively mitigated the warming effect in the Fluvo-aquic soil and the Ultisol. In conclusion, our findings highlight NO2- significantly stimulates HONO and NOx emissions from dryland agricultural soils, dominated by nitrification. In addition, subtle differences of soil NH3, N2O, HONO, and NOx emissions indicated different N turnover processes, and should be considered in biogeochemical and atmospheric chemistry models.

Combining modified Graeb score and intracerebral hemorrhage score to predict poor outcome in patients with spontaneous intracerebral hemorrhage undergoing surgical treatment.

Objective: Spontaneous intracerebral hemorrhage (sICH) is a frequently encountered neurosurgical disease. The purpose of this study was to evaluate the relationship between modified Graeb Score (mGS) at admission and clinical outcomes of sICH and to investigate whether the combination of ICH score could improve the accuracy of outcome prediction. Methods: We retrospectively reviewed the medical records of 511 patients who underwent surgery for sICH between January 2017 and June 2021. Patient outcome was evaluated by the Glasgow Outcome Scale (GOS) score at 3 months following sICH, where a GOS score of 1-3 was defined as a poor prognosis. Univariate and multivariate logistic regression analyses were conducted to determine risk factors for unfavorable clinical outcomes. Receiver operating characteristic (ROC) curve analysis was performed to detect the optimal cutoff value of mGS for predicting clinical outcomes. An ICH score combining mGS was created, and the performance of the ICH score combining mGS was assessed for discriminative ability. Results: Multivariate analysis demonstrated that a higher mGS score was an independent predictor for poor prognosis (odds ratio [OR] 1.207, 95% confidence interval [CI], 1.130-1.290, p < 0.001). In ROC analysis, an optimal cutoff value of mGS to predict the clinical outcome at 3 months after sICH was 11 (p < 0.001). An increasing ICH-mGS score was associated with increased poor functional outcome. Combining ICH score with mGS resulted in an area under the curve (AUC) of 0.790, p < 0.001. Conclusion: mGS was an independent risk factor for poor outcome and it had an additive predictive value for outcome in patients with sICH. Compared with the ICH score and mGS alone, the ICH score combined with mGS revealed a significantly higher discriminative ability for predicting postoperative outcome.

Climate warming, but not Spartina alterniflora invasion, enhances wetland soil HONO and NOx emissions.

Climate warming and invasive plant growth (plant invasion) may aggravate air pollution by affecting soil nitrogen (N) cycling and the emissions of reactive N gases, such as nitrous acid (HONO) and nitrogen oxides (NOx). However, little is known about the response of soil NOy (HONO + NOx) emissions and microbial functional genes to the interaction of climate warming and plant invasion. Here, we found that experimental warming (approximately 1.5 °C), but not Spartina alterniflora invasion, increased NOy emissions (0-140 ng N m-2 s-1) of treated wetland soils by 4-10 fold. Warming also decreased soil archaeal and fungal richness and diversity, shifted their community structure (e.g., decreased the archaeal classes Thermoplasmata and Iainarchaeia, and increased the archaeal genus Candidatus Nitrosoarchaeum, and the fungal classes Saccharomycetes and Tritirachiomycetes), and decreased the overall abundance of soil N cycling genes. Structural equation modeling revealed that warming-associated changes in edaphic factors and the microbial N cycling potential are responsible for the observed increase in soil NOy emissions. Collectively, the results showed that climate warming accelerates soil N cycling by stimulating large soil HONO and NOx emissions, and influences air quality by contributing to atmospheric reactive N and ozone cycling.

Alleviation of aluminum phytotoxicity by canola straw biochars varied with their cultivating soils through an investigation of wheat seedling root elongation.

The types and amounts of cations and their uptake by plants vary with cultivating soils, which correlates with the carbonates and subsequent alkalis contents in the derived biochars. However, regional differences in the alkaline properties of crop straw biochars are unclear. In the present study, biochars pyrolyzed from canola straws collected from four different regions were used to assess the differences in the alkaline properties among them. The biochars were referred to as YTBC, XCBC, NJBC, and HYBC, respectively, and their feedstocks were collected from four different regions from south to north of China. The NH4OAC exchangeable base cations (K+, Na+, Ca2+, Mg2+) in the biochars were 270.74, 1427.05, 2089.23, and 1516.48 mmol kg-1 for YTBC, XCBC, NJBC, and HYBC, respectively, which were roughly consistent with the exchangeable base cations in the corresponding planting soils (17.57, 28.20, 151.26 and 444.65 mmol kg-1, respectively). The pH, carbonates content, and alkalinity of biochars considerably increased as follows: YTBC < XCBC < NJBC < HYBC. Wheat seedling root elongation experiment indicated that the Al(III) phytotoxicity alleviation effect of the biochars was as follows: HYBC > NJBC > XCBC > YTBC, which was corroborated by the subsequent findings of Evans blue staining, the remnant aluminum (Al(III)) in the reaction solution and Al(III) distribution in the wheat seedling roots. Thus, planting soil had a dominant influence in alleviating Al(III) phytotoxicity, and studies on crop straw biochar properties concerning alkalinities or liming potentials should not only consider crop genera and pyrolysis conditions, but also cultivating conditions.

Adsorption of Cd(II) by two variable-charge soils in the presence of pectin.

Batch experiments were conducted to investigate cadmium(II) (Cd(II)) adsorption by two variable-charge soils (an Oxisol and an Ultisol) as influenced by the presence of pectin. When pectin dosage was less than 30 g kg(-1), the increase in Cd(II) adsorption with the increasing dose of pectin was greater than that when the pectin dosage was >30 g kg(-1). Although both Langmuir and Freundlich equations fitted the adsorption isotherms of Cd(II) and electrostatic adsorption data of Cd(II) by the two soils well, the Langmuir equation showed a better fit. The increase in the maximum total adsorption of Cd(II) induced by pectin was almost equal in both the soils, whereas the increase in the maximum electrostatic adsorption of Cd(II) was greater in the Oxisol than in the Ultisol because the former contained greater amounts of free Fe/Al oxides than the latter, which, in turn, led to a greater increase in the negative charge on the Oxisol. Therefore, the presence of pectin induced the increase in Cd(II) adsorption by the variable-charge soils mainly through the electrostatic mechanism. Pectin increased the adsorption of Cd(II) by the variable-charge soils and thus decreased the activity and mobility of Cd(II) in these soils.

Effect of pectin on adsorption of Cu(II) by two variable-charge soils from southern China.

The influence of pectin on Cu(II) adsorption by two variable-charge soils (an Oxisol and an Ultisol) was investigated. Pectin increased the adsorption, and the extent of adsorption increased linearly with the dose of pectin, being greater in the Oxisol than that in the Ultisol because the adsorption of pectin by the Oxisol was greater. Both Langmuir and Freundlich equations fitted the adsorption isotherms of Cu(II) for both soils well. The fitting parameters of both equations indicated that pectin increased not only the adsorption capacity of the soils for Cu(II) but also the adsorption strength of Cu(II). The effect of pectin decreased with rising pH in the pH range 3.5-6.0, although the extent of electrostatic adsorption of Cu(II) by both soils was markedly greater over the pH range. Fourier-transformed infrared spectroscopy analysis and zeta potential measurement of soil colloids indicated that adsorption of pectin by the soils made the negative charge on both soils more negative, which was responsible for the increase in the electrostatic adsorption of Cu(II) induced by the addition of pectin. In conclusion, pectin-enhanced adsorption of Cu(II) especially at low pH would be beneficial to the soils as it would decrease the activity and mobility of Cu(II) in acidic variable-charge soils.