The production of the hydroxyl radical (HO·) is important in environmental chemistry. This study reports a new source of HO· generated solely from hydrogen peroxide (H2O2) activated by hydroxylamine (HA). Electron paramagnetic resonance analysis and the oxidation of a HO· probe, benzoic acid, were used to confirm the production of HO·. The production of HO· increased with increasing concentrations of either HA or H2O2 as well as decreasing pH. The second-order rate constant for the reaction was (2.2 ± 0.2) × 10(-4) M(-1) s(-1). HO· was probably produced in two steps: the activation of H2O2 by protonated HA and then reaction between the H2O2 and the intermediate protonated aminoxyl radical generated in the first step. Such a two-step oxidation can possibly be ascribed to the ionizable hydroxyl moiety in the molecular structure of HA, as is suggested by comparing the reactivity of a series of HA derivatives in HO· production. The results shed light on a previously unknown source of HO· formation, which broadens the understanding of its role in environmental processes.

Taxonomic characterization of environmental microbial communities via high-throughput DNA sequencing has revealed that patterns in microbial biogeography affect community structure. However, shifts in functional diversity related to variation in taxonomic composition are poorly understood. To overcome limitations due to the prohibitive cost of high-depth metagenomic sequencing, tools to infer functional diversity based on phylogenetic distributions of functional traits have been developed. In this study we characterized functional microbial diversity at 11 sites along the Mississippi River in Minnesota using both metagenomic sequencing and functional-inference-based (PICRUSt) approaches. This allowed us to determine how distance and variation in land cover throughout the river influenced the distribution of functional traits, as well as to validate PICRUSt inferences. The distribution and abundance of functional traits, by metagenomic analysis, were similar among sites, with a median standard deviation of 0.0002% among tier 3 functions in KEGG. Overall inferred functional variation was significantly different (P ≤ 0.035) between two water basins surrounded by agricultural vs. developed land cover, and abundances of bacterial orders that correlated with functional traits by metagenomic analysis were greater where abundances of the trait were inferred to be higher. PICRUSt inferences were significantly correlated (r = 0.147, P = 1.80 × 10−30) with metagenomic annotations. Discrepancies between metagenomic and PICRUSt taxonomic-functional relationships, however, suggested potential functional redundancy among abundant and rare taxa that impeded the ability to accurately assess unique functional traits among rare taxa at this sequencing depth. Results of this study suggest that a suite of “core functional traits” is conserved throughout the river and distributions of functional traits, rather than specific taxa, may shift in response to environmental heterogeneity.

This article develops a two-country endogenous growth model with accumulation of both physical and human capital. We establish the existence of two-country balanced growth equilibria with physical and human capital in which a static and dynamic version of the Heckscher-Ohlin (HO) hypothesis hold true. We also show the existence of unbalanced growth equilibria in which the static and dynamic HO hypotheses can be violated. The multiplicity of paths with international trade emerge as a result of the intertemporal no-arbitrage condition when factor prices are equalized across countries.

Carbon dots have wide applications in bioimaging, encryption, sensing, and light-emitting devices, but most preparations of carbon dots require complicated separation and purification steps. Here, a clustering-induced emission luminogen, sodium alginate, was covalently "glued" by ethylenediamine to prepare carbon dots on a 100 g scale, without any separation or purification. The conversion yield was as high as 94.7%. Theoretical calculations suggested that the fluorescence emission of as-prepared carbon dots (N-CDs) was mainly attributable to through-space conjugation between oxygen atoms and carbonyl moieties. The N-CDs were shown to have applications as a fluorescent ink for encryption and as a phosphor for white light-emitting diodes. This work provides a convenient method for the large-scale preparation of carbon dots and a new understanding of fluorescent emission of carbon dots.

Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist.

A mechanochemical-assisted extraction (MCAE) method was proposed and investigated for the fast extraction of two kaempferol glycosides (kaempferol-3-O-[2-O-β-D-galactopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside and kaempferol-3-O-[2-O-β-D-xylopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside) from Camellia oleifera Abel. meal. The effects of operating parameters in terms of NaOH content, grinding time, extraction time, and ratio of solution to solid were evaluated by means of response surface methodology (RSM). Under the optimal conditions with a ratio of material to NaOH of 20:1 (g/g), a milling time of 15 min, and a ratio of solution to solid of 20:1 (mL/g) for 60 min, the maximum extraction yields of the two kaempferol glycosides reached 13.34 and 13.83%, respectively. The antioxidant activity of kaempferol glycosides extract was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay and ferric thiocyanate (FTC) assay. Compared with the heat reflux extraction (HRE) method, the yield and the antioxidant activities of the extracts from MCAE with water as solvent were higher and stronger.

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