Differential responses of temperature sensitivity of greenhouse gases emission to seasonal variations in plateau riparian zones.

Riparian zones, regarded as hotspots for greenhouse gas (GHG) emissions, where the variation in temperature sensitivity (Q10) of GHG emissions is crucial for assessing GHG budgets under global warming. However, the seasonal Q10 of GHG emissions from high-elevation riparian zones and underlying microbial mechanisms are poorly documented. This study focuses on seasonal Q10 patterns of GHG emissions from riparian zones along the Lhasa River on the Tibetan Plateau. CO2 and CH4 emissions from riparian soils were more sensitive to temperature in spring than in summer. The opposite trend was observed for Q10 of N2O emissions. Soil organic carbon (SOC) had relatively large direct effects on the Q10-CO2 value in summer, whereas soil nitrate nitrogen (SNO3--N) was the determinant of Q10-CO2 value in spring. mcrA:pmoA and soil microbial biomass C (SMBC) had strong direct effects on the Q10 of CH4 emissions in summer; the Q10-CH4 value in spring was significantly affected by the mcrA abundance. SMBC and the nirK + nirS abundance were key factors affecting the Q10-N2O value. Q10-CO2 and Q10-CH4 values exhibited strong seasonalities in the lower reaches of riparian soils, mainly due to the seasonalities of SNO3--N and mcrA:pmoA, respectively. The Q10-N2O value in the middle and upper reaches of riparian soils presented seasonality, which was largely due to the seasonalities of soil ammonia nitrogen and microbial biomass carbon. During thawing, plant productivity increased, substrate carbon was sufficient, microbial biomass increased, and inorganic nitorgen and denitrifier abundance decreased, causing 29.67% and 37.47% decreases in the Q10-CO2 and Q10-CH4 values, respectively, and a 70.85% increase in the Q10-N2O value, indicating that the potential release of N2O from riparian zones along the plateau river was more susceptible to seasonal variations. Our findings are conducive to accurately evaluating the potential contribution of GHG emissions from high-elevation riparian zones to global warming.

Seeking the hotspots of nitrogen removal: A comparison of sediment denitrification rate and denitrifier abundance among wetland types with different hydrological conditions.

Wetlands play a vital role in removing nitrogen (N) from aquatic environments via the denitrification process, which is regulated by multiple environmental and biological factors. Until now, the mechanisms by which environmental factors and microbial abundance regulate denitrification rates in wetlands under different hydrological conditions remain poorly understood. Here, we investigated sediment potential denitrification rate (PDR) and unamended denitrification rate (UDR), and quantified denitrifier abundance (nirS, nirK, and nosZ genes) in 36 stream, river, pond, and ditch wetland sites along the Dan River, a nitrogen-rich river in central China. The result indicated that ditches had the highest denitrification rates and denitrifier abundance. Both PDR and UDR showed strong seasonality, and were observed to be negatively correlated with water velocity in streams and rivers. Moreover, denitrification rates were significantly related to denitrifier abundance and many water quality parameters and sediment properties. Interestingly, PDR and UDR were generally positively associated with N and carbon (C) availability in streams and rivers, but such correlations were not found in ponds and ditches. Using a scaling analysis, we found that environmental parameters, including Reynolds number, sediment total C ratio, and interstitial space, coupled with relative nirS gene abundance could predict the hotspots of denitrification rates in wetlands with varying hydrologic regimes. Our findings highlight that hydrological conditions, especially water velocity and hydrologic pulsing, play a nonnegligible role in determining N biogeochemical processes in wetlands.

Environmental Factors and Microbial Diversity and Abundance Jointly Regulate Soil Nitrogen and Carbon Biogeochemical Processes in Tibetan Wetlands.

Wetlands have numerous critical ecological functions, some of which are regulated by several nitrogen (N) and carbon (C) biogeochemical processes, such as denitrification, organic matter decomposition, and methane emission. Until now, the underlying pathways of the effects of environmental and biological factors on wetland N and C cycling rates are still not fully understood. Here, we investigated soil potential/net nitrification, potential/unamended denitrification, methane production/oxidation rates in 36 riverine, lacustrine, and palustrine wetland sites on the Tibet Plateau. The results showed that all the measured N and C cycling rates did not differ significantly among the wetland types. Stepwise multiple regression analyses revealed that soil physicochemical properties (e.g., moisture, C and N concentration) explained a large amount of the variance in most of the N and C cycling rates. Microbial abundance and diversity were also important in controlling potential and unamended denitrification rates, respectively. Path analysis further revealed that soil moisture and N and C availability could impact wetland C and N processes both directly and indirectly. For instance, the indirect effect of soil moisture on methane production rates was mainly through the regulating the soil C content and methanogenic community structure. Our findings highlight that many N and C cycling processes in high-altitude and remote Tibetan wetlands are jointly regulated by soil environments and functional microorganisms. Soil properties affecting the N and C cycling rates in wetlands through altering their microbial diversity and abundance represent an important but previously underestimated indirect pathway.

Efficient removal of gaseous formaldehyde by amine-modified diatomite: a combined experimental and density functional theory study.

Amine-modified diatomite with remarkable formaldehyde (HCHO) removal efficiency was prepared by grafting 3-aminopropyltrimethoxysilane (APTMS) in this research. The interfacial properties and microstructures of the prepared adsorbents were characterized and analyzed. The HCHO adsorption properties of the amine modified diatomite were also systematically studied, and it has been proven to be effective adsorbent with better adsorption performance than activated carbon for the removal of gaseous HCHO. Furthermore, to better explain the experimental results, we performed density functional theory (DFT) study on the adsorption system and calculated the geometry, energy, and charge parameters based on first principles. Also, the underlying adsorption mechanism was proposed detailedly by combining experimentation with DFT calculation, suggesting that amine modified diatomite can be efficient adsorbent for the elimination of gaseous formaldehyde.

Metagenomic insights into the abundance and composition of resistance genes in aquatic environments: Influence of stratification and geography.

A global survey was performed with 122 aquatic metagenomic DNA datasets (92 lake water and 30 seawater) obtained from the Sequence Read Archive (SRA). Antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) were derived from the dataset sequences via bioinformatic analysis. The relative abundances of ARGs and MRGs in lake samples were in the ranges ND (not detected)-1.34 × 100 and 1.22 × 10-3-1.98 × 10-1 copies per 16S rRNA, which were higher than those in seawater samples. Among ARGs, multidrug resistance genes and bacitracin resistance genes had high relative abundances in both lake and sea water samples. Multi-metal resistance genes, mercury resistance genes and copper resistance genes had the greatest relative abundance for MRGs. No significant difference was found between epilimnion and hypolimnion in abundance or the Shannon diversity index for ARGs and MRGs. Principal coordinates analysis and permutational multivariate analysis of variance (PERMANOVA) test showed that stratification and geography had significant influence on the composition of ARGs and MRGs in lakes (p < 0.05, PERMANOVA). Coastal seawater samples had significantly greater relative abundance and a higher Shannon index for both ARGs and MRGs than deep ocean and Antarctic seawater samples (p < 0.05, Kruskal-Wallis one-way ANOVA), suggesting that human activity may exert more selective pressure on ARGs and MRGs in coastal areas than those in deep ocean and Antarctic seawater.

Liberation characteristics after cryogenic modification and air table separation of discarded printed circuit boards.

Liberating useful materials from printed circuit boards (PCBs) is challenging because PCBs are flexible and complex in terms of materials and components. In this study, the crushing of PCBs at low-temperature was investigated. The results indicated that when the temperature was decreased to approximately -20 °C, the strength of PCBs decreased and their brittleness increased, making them easier to crush. A double roll crusher was selected to crush the PCBs. The particle size distribution and power consumption were studied under different working conditions. The results showed that the particle size of most of the lumps was in the range 15×20-25×20 mm, and that power consumption was minimal when the frequency of the crusher was 40-50 Hz. A small shredder was used for cryogenic grinding, and it was found that its power consumption strongly depended on the cooling temperature. An orthogonal experiment was conducted, which revealed that a smaller cutter gap and higher rotational speed could achieve higher yield. Furthermore, the results indicated that the air table developed to liberate PCB materials could effectively separate 2.8-0.5mm grade materials. Overall, the results of this study provide an experimental foundation for more effectively recycling discarded PCBs.

Intradural lysis and peripheral nerve implantation for traumatic obsolete incomplete paralysis.

Twenty-eight patients who suffered traumatic obsolete incomplete paralysis were treated with intradural lysis and peripheral nerve implantation by a microsurgery technique. The endorachis was opened and the fibrous bands adhering to the spinal cord from the arachnoid, pia mater spinalis, ligamenta denticulatum, and the initial part of the nerve root were completely relieved. The abnormal spinal cord was then opened by three to six incisions, which were each 0.1 mm to 0.2 mm deep and longer than the abnormal portion. A cyst found in the back or side of the spinal cord was opened and the liquid in it was drained. After that, the denuded spineurium and perineurium of the autogenous sural nerve were grafted, which makes the character and aspect of the nerve like the cauda equine. The nerve was longitudinally implanted into the incised spinal cord, and the cyst was waded with grafted nerve and at least one of them is ectropion sutured with the pia mater with 9-0 scatheless wire as a drain. Finally, the endorachis was covered by sacrospinal muscle flap. These patients were followed for 2 years to 8 years (average 3.5 years), and the sensibility and motion of each increased at least one grade. The strength of the main muscle was increased two grades and reached four grades in 11 patients, and the capability to walk was recovered. Relieving of the adhesion in the endorhachis, carving the cicatricial spinal cord, and implanting the autogenous peripheral nerve yields good results by initial clinical observation for traumatic obsolete and incomplete paralysis.