Asymmetric Intramolecular Amination Catalyzed with Cp*Ir-SPDO via Nitrene Transfer for Synthesis of Spiro-Quaternary Indolinone.

An asymmetric intramolecular spiro-amination to high steric hindering -C-H bond of 1,3-dicarbonyl via nitrene transfer using inactive aryl azides has been carried out by developing a novel Cp*Ir(III)-SPDO (spiro-pyrrolidine oxazoline) catalyst, thereby enabling the first successful construction of structurally rigid spiro-quaternary indolinone cores with moderate to high yields and excellent enantioselectivities. DFT computations support the presence of double bridging H-F bonds between [SbF] and both the ligand and substrate, which favors the plane-differentiation of the enol π-bond for nitrenoid attacking. These findings open up numerous opportunities for the development of new asymmetric nitrene transfer systems.

Atroposelective synthesis of biaxial bridged eight-membered terphenyls via a Co/SPDO-catalyzed aerobic oxidative coupling/desymmetrization of phenols.

Bridged chiral biaryls are axially chiral compounds with a medium-sized ring connecting the two arenes. Compared with plentiful methods for the enantioselective synthesis of biaryl compounds, synthetic approaches for this subclass of bridged atropisomers are limited. Here we show an atroposelective synthesis of 1,3-diaxial bridged eight-membered terphenyl atropisomers through an Co/SPDO (spirocyclic pyrrolidine oxazoline)-catalyzed aerobic oxidative coupling/desymmetrization reaction of prochiral phenols.

[Regulation Effects of Humus Active Components on Soil Cadmium Availability and Critical Threshold for Rice Safety].

Organic materials containing humic acids (HAs) play important roles in regulating the bioavailability of cadmium (Cd) in soils and thus its accumulation in crops. The effects of the two active components of HAs, humic acid (HA) and fulvic acid (FA), in organic materials and their different ratios (HA/FA) on Cd uptake and accumulation in rice were investigated using a field plot experiment, and their relationships with the Cd fractions and availability in paddy soil as influenced by the use of these organic materials were analyzed in combination with the fractionation method of chemical continuous extraction. The results showed that the effects of HAs on Cd availability in soil and Cd accumulation in rice grains were controlled by the ratios of the active components in the organic materials.

[Research Advances in Barrier Technology of Paddy Soil Co-contaminated with As and Cd].

Arsenic (As) and cadmium (Cd) are the most common toxic and harmful heavy metal elements in paddy soils and are easily transferred from the soil to grains. At present, As and Cd and their co-contamination in paddy soils in China are widespread, posing a serious threat to food security and human health. As and Cd have opposite environmental behaviors in soil, and the simultaneous remediation of co-contamination with As and Cd is a current technical difficulty for safe rice production.

[Characteristics of Typical Soil Acidification and Effects of Heavy Metal Speciation and Availability in Southwest China].

Using a spatial instead of temporal approach, soil samples were collected from the main types and different stages of acidification in Southwest China, and the characteristics of soil physicochemical properties, acid-buffering properties, and heavy metal fugacity patterns were analyzed, combined with biological experiments in small cabbage pots, to explore the coupling relationship between soil acidification and changes in heavy metal morphological activity. The results showed that the exchangeable salt-based ions of the soil decreased with increasing acidification in purple and yellow soils, caused by the loss of exchangeable Ca. The acid-buffering capacity of purple and yellow soils was higher at pH>7.

[Effects of Interaction of Zinc and Cadmium on Growth and Cadmium Accumulation of L].

The interaction between different elements is an efficient means to control the heavy metal accumulation in crops. Phosphorus (P) and zinc (Zn), as essential nutrient elements of plants, have been shown to have important impacts on cadmium (Cd) accumulation in crops through interactions with each other. However, the function of the simultaneous interaction of P, Zn, and Cd on vegetable growth and Cd accumulation remains unclear.

[Effects of Water Management on the Transformation of Iron Oxide Forms in Paddy Soils and Its Coupling with Changes in Cadmium Activity].

The transformation of iron oxide forms in the process of soil water management in paddy fields has an important impact on soil cadmium (Cd) activity and accumulation in rice. The test soil for this experiment was purple paddy soil in southwest China contaminated with exogenously added Cd. Through indoor cultivation experiments, the effects of water management (continuous flooding, CW; alternating wet and dry, DW) combined with iron oxide application (goethite, G-Fe; iron powder, Fe) on the pH, redox state (Eh, pe+pH), iron oxide form conversion, and Cd bioavailability changes in Cd-contaminated soil were studied.

Occurrence, correlation, and partitioning of organophosphate esters in soil and tree bark from a megacity, Western China.

Concern over the influences of constant addition of emerging anthropogenic chemicals to the environment has become a public issue during the rapid urbanization. Here, we investigated the occurrence of organophosphate esters (OPEs) in soil and corresponding tree bark in a megacity, Western China. Our results showed levels of OPEs in tree bark (1250 ± 573 ng/g dry weight (dw)) were 1-2 orders of magnitude higher than those in soil (40.

[Cd Pollution and Safe Planting Zoning in Paddy Soils: A Case Study in a District of Chongqing].

Rice has a strong ability to accumulate Cd in soil, and it is of great significance to study Cd pollution and safe planting zoning in paddy soils. In this work, 300 sets of paddy soil-rice samples were simultaneously collected in 22 towns in a District of Chongqing, and soil pH, soil total and available Cd contents, and brown rice Cd contents were determined. Soil Cd pollution was assessed using the geoaccumulation index, bioconcentration factor, and the single-factor pollution index.

[Screening and Evaluation of Methods for Determining Available Lead (Pb) and Cadmium (Cd) in Farmland Soil].

The accumulation of heavy metals in crops is largely dependent on the availability of heavy metals in soils. Due to the differences of soil types and pollution characteristics, there is no widely recognized method for the determination of the bio-available heavy metals in soils such as Pb and Cd. In order to screen and establish suitable methods, the extractable abilities of five extractants (CaCl, NHOAc, HCl, EDTA, and DTPA) and Gradient Diffusion Film Technology (DGT) on four typical farmland soils with very different properties in Chongqing (acid purple soil, neutral purple soil, calcareous yellow soil and calcareous purple soil) were systematically compared.

[Adsorption Effect and Mechanism of Aqueous Arsenic on FeMnNi-LDHs].

Removing As(Ⅲ)from water steadily and efficiently is still a challenging global issue. In this study, novel FeMnNi-LDHs were prepared by a co-precipitation method using Fe, Mn, and Ni as lamellar cations, and the structure were characterized by XRD, TEM, FT-IR, and XPS techniques, and the adsorption performance and mechanism of As(Ⅲ)was explored. The results showed that FeMnNi-LDHs have typical characteristic peaks of layered double hydroxides, with sharp peaks and high crystallinity.

[Photocatalytic Degradation of Rhodamine B with Micro-SiC/Graphene Composite Under Visible Light Irradiation].

To develop low consumption and an environmentally friendly degradation technology for organic pollutants, micro-SiC/graphene composite materials were synthesized by photocatalytic reduction, and the composition and morphology of the prepared materials were characterized by XRD, FTIR, Raman spectroscopy, XPS, and SEM. Rhodamine B (RhB) was selected as the simulated pollutant to investigate the photocatalytic activity and stability of composite materials under visible light irradiation. The degradation mechanism was preliminarily discussed by active species capture experiments.

[Electrocatalytic Oxidation of Sulfadiazine with Ni-Doped Sb-SnO Ceramic Ring Particle Electrode].

The excessive use and abuse of antibiotics has brought about serious threats to water environmental safety and human health. It is necessary to develop efficient, cheap, and environmentally friendly treatment technologies for antibiotics. In this work, a Ni-doped Sb-SnO microporous ceramic ring particle electrode was prepared by the dipping method and characterized by scanning electron microscopy, energy dispersion spectroscopy, and X-ray diffraction.

[Safe Utilization of Paddy Soils Lightly Polluted with Cadmium in Western Chongqing].

The western Chongqing region is the main grain-producing area in Chongqing. This region's soils are characterized by light-to-moderate cadmium (Cd) pollution. Two types of typical paddy soils in this area (acidic and calcareous purple soils) were selected for the development of safe rice production techniques using in situ field remediation experiments.

[Absorption Characterization and the Identification of Factors Influencing Five Organophosphate Esters in Water-Soil System].

In this study, the absorption behavior of five organophosphate esters (OPEs) congeners was monitored in a water-soil system, and three absorption isotherm equations were modeled. Furthermore, the factors influencing the absorption process including temperature and dissolved organic carbon (DOC) were also investigated. The results showed that an equilibrium state was reached after 12 hours of absorption for these five OPEs congeners, which could be appropriately modeled by the Freundlich isotherm equations with values ranging from 0.

[Use of the Nitrogen/Carbon Ratio (N/C) and Two End-Member Sources Mixing Model to Identify the Origins of Dissolved Organic Matter from Soils in the Water-Level Fluctuation Zones of the Three Gorges Reservoir].

Soil dissolved organic matter (soil DOM) plays a crucial role in the environmental fate of pollutants because of its exceptional biogeochemical reactivity. Therefore, tracing the sources and understanding the properties of DOM through chemical characterization is important for clarifying the "structure-reactivity" of DOM in the environment. In this study, traditional elementary analysis methods including nitrogen/carbon ratio (N/C) determinations and derived two end-member source-loads mixing models were applied to soil DOM extracted from the water-level fluctuation zones of the Three Gorges Reservoir (TGR) area.

Phthalate esters in biota, air and water in an agricultural area of western China, with emphasis on bioaccumulation and human exposure.

Phthalate esters (PAEs) have been shown to be ubiquitous in abiotic and biotic environmental compartments; however, information about bioaccumulation behavior and human exposure, both via environmental exposure and the diet, are limited. Herein, we report the concentrations and composition profiles of phthalate esters (PAEs) in biological samples, river water, indoor air, and outdoor air samples collected from an agricultural site in western China. Dibutyl phthalate (DNBP) occupied a relatively high abundance in biological samples, discrepant with the environmental samples in which di-(2-ethylhexyl) phthalate (DEHP) was the dominant congener.

[Simulation of the Migration and Release Characteristics of Organophosphate Esters in Fluctuation Zone Soil of the Three Gorges Reservoir During Flooding].

In this study, we investigated the effects of organophosphate ester (OPE) concentrations, temperature, soil organic matter, and microorganisms on the migration and release of several common OPEs from fluctuation zone soil in the Three Gorges Reservoir (TGR) to the overlying water by simulation experiments in the lab. The results indicate that the release of OPEs is determined based on their concentrations in the soil. The release of OPEs from soil to the overlying water decreases with increasing organic matter content, which indicates that the presence of organic matter could inhibit the migration of OPEs.

[Occurrence and Distribution of the Organophosphate Esters in Soils of Mixed-land Use Area in Chongqing City].

Organophosphate esters (OPEs) in surface soil of four different functional areas in Chongqing were identified and quantified using ultra-high performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS). The composition and characteristics of OPEs were discussed along with the relationships between soil organic matter (SOM) and OPEs through correlation analysis, and possible sources of OPEs were simultaneously investigated through principal component analysis (PCA). The results showed that the concentrations of ∑OPEs ranged from 10.

Organophosphate esters in biota, water, and air from an agricultural area of Chongqing, western China: Concentrations, composition profiles, partition and human exposure.

We measured the concentrations of organophosphate esters (OPEs) in some biotic samples which can serve as human foodstuffs and ambient environments including air and river water from an agricultural area of Chongqing, western China. Fish samples exhibited highest OPEs levels (960 ng/g lipid weight) among the biota, followed by chicken (676 ng/g lw), cattle (545 ng/g lw) and pigs (535 ng/g lw). Tributyl phosphate (TNBP), tris (2-methylpropyl) (TIBP) and chlorinated OPEs were the major analogs in biotic samples, which appeared similar with the patterns from river water and outdoor air, but apparently different from indoor air.

Occurrence of tetrabromobisphenol a (TBBPA) and hexabromocyclododecane (HBCD) in soil and road dust in Chongqing, western China, with emphasis on diastereoisomer profiles, particle size distribution, and human exposure.

Currently, the HBCDs were listed in Annex A by the Stockholm Convention, and the knowledge on the contamination of TBBPA and HBCDs in soil and road dust in China is still limited, and it is unclear what role is played by dust particle size distribution. In this study, a total of 81 soil and 43 road dust samples were analyzed with TBBPA and ΣHBCDs concentrations ranging from < LOQ to 33.8 ng/g dw (dry weight) and 0.

[Occurrence, Distribution and Health Risk of the Phthalate Esters in Riparian Soil in the Fluctuating Zone of the Three Gorges Reservoir].

Soil samples were collected in the fluctuating zone of the Three Gorges Reservoir to analyze the concentrations and distribution of phthalate esters (PAEs) using ultra performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS). Meanwhile, the interrelationships among the PAE congeners were analyzed and the potential sources of PAEs in soil were determined by the correlation analysis and principal component analysis. The results showed that the concentrations of ∑PAEs ranged from 322.

[Occurrence of Organophosphate Esters in Soils of the Three Gorges Reservoir].

Organophosphate esters (OPEs) were first identified and quantified in farmland and riparian soil in the Three Gorges Reservoir (TGR) of western China. The mean concentrations of OPEs were 272 ng·g dry weight (dw) in farmland soil and 498 ng·g dw in riparian soil. These values lie at the middle of the range of worldwide values.