Dissipation and Enantioselective Degradation of Plant Growth Retardants Paclobutrazol and Uniconazole in Open Field, Greenhouse, and Laboratory Soils

Greenhouses are increasingly important in human food supply. Pesticides used in greenhouses play important roles in horticulture; however, little is known about their behavior in greenhouse environments. This work investigates the dissipation and enantioselctive degradation of plant growth retardants including paclobutrazol and uniconazole in soils under three conditions (i.e., open field, greenhouse, and laboratory). The dissipation and enantioselective degradation of paclobutrazol and uniconazole in greenhouse were different from those in open field; they were more persistent in greenhouse than in open field soil. Leaching produced by rainfall is responsible for the difference in dissipation. Thus, local environmental impacts may occur more easily inside greenhouses, while groundwater may be more contaminated in open field. Spike concentrations of 5, 10, and 20 times the concentrations of native residues were tested for the enantioselective dissipation of the two pesticides; the most potent enantioselective degradation of paclobutrazol and uniconazole occurred at the 10 times that of the native residues in the greenhouse environments and at 20 times native residues in open field environments. The higher soil activity in greenhouses than in open fields was thought to be responsible for such a difference. The environmental risk and regulation of paclobutrazol and uniconazole should be considered at the enantiomeric level

General Self-Assembly Route toward Sparsely Studded Noble-Metal Nanocrystals inside Graphene Hollow Sphere Network for Ultrastable Electrocatalyst Utilization

Herein, we rationally design and construct a novel type of sparsely studded noble-metal nanocrystals inside graphene hollow sphere network (abbreviated as noble-metal@G HSN) through an electrostatic-attraction-directed self-assembly approach. The formation of Pt@G and Pd@G hollow sphere networks have been illustrated as examples using SiO₂ spheres as templates. Moreover, the electrocatalytic performance of the Pt@G HSN for methanol oxidation reaction has been examined as a proof-of-concept demonstration of the compositional and structural superiorities of noble-metal@G HSN toward electrocatalyst utilization. The as-prepared Pt@G HSN manifests higher catalytic activity and markedly enhanced long-term durability in comparison with commercial Pt/C catalyst

Enantioselective Interaction of Acid α‑Naphthyl Acetate Esterase with Chiral Organophosphorus Insecticides

Many previous works have demonstrated that acetylcholinesterase (AChE) was enantioselectively inhibited by chiral organophosphorus insecticides (OPs) and that a significant difference in reactivation existed for AChE inactivated by (1<i>R</i>)- versus (1<i>S</i>,3<i>S</i>)-stereoisomers of isomalathion. It had been known that α-naphthyl acetate esterase (ANAE), an enzyme which might play an essential role in the growth of plants and the defense of plants against environmental stress by regulating the concentration of hormones in plants, can be inhibited by OPs. However, it was unknown whether interaction of ANAE with chiral OPs was enantioselective. The present work investigated the inhibition kinetics and spontaneous reactivation of ANAE inactivated by enantiomers of malaoxon, isomalathion, and methamidophos. The order of inhibition potency is (<i>R</i>) > (<i>S</i>) for malaoxon, (1<i>R</i>,3<i>R</i>) > (1<i>R</i>,3<i>S</i>) > (1<i>S</i>,3<i>R</i>) > (1<i>S</i>,3<i>S</i>) for isomalathion, and (<i>S</i>) > (<i>R</i>) for methamidophos according to bimolecular rate constants of inhibition (<i>k</i>_i), which is consistent with the order observed in the enantioselective inhibition of AChE by malaoxon, isomalathion, and methamidophos. The difference in spontaneous reactivation of AChE inactivated between (1<i>R</i>)- and (1<i>S</i>,3<i>S</i>)-isomers of isomalathion is conserved for ANAE. The observations indicated ANAE and AChE have similar selective inhibition kinetics and postinhibitory reactions in reaction with chiral OPs

Concentrations of DDTs and Enantiomeric Fractions of Chiral DDTs in Agricultural Soils from Zhejiang Province, China, and Correlations with Total Organic Carbon and pH

Dichlorodiphenyltrichloroethanes (DDTs) are persistent organic pollutants that were widely used in China, especially eastern China, as insecticides. This work investigated the concentration, dissipation, and volatilization of DDTs and enantiomeric fractions (EFs) of <i>o</i>,<i>p</i>′-DDD and <i>o</i>,<i>p</i>′-DDT in agricultural soils collected in 2006 from 58 sites in Zhejiang province. Correlations between DDT residues and soil properties were assessed to determine the effect of soil properties on the environmental attenuation of DDTs. High concentrations and detection frequencies were found for DDTs in agricultural soils in the region even though large-scale use of DDTs was banned over 20 years ago. The amount of DDTs was about 485 tons in the upper 20 cm of the soil column of cropland in the province in 2010, with a dissipation half-life of ∼9 years. The mass flux of DDTs was 43 ng m^–2 h^–1, which corresponds to emissions of 7.6 tons with an emission factor of 1.6% in 2006. The low <i>p</i>,<i>p</i>′-DDT/<i>p</i>,<i>p</i>′-DDE ratios and high <i>o</i>,<i>p</i>′-DDT/<i>p</i>,<i>p</i>′-DDT ratios suggest that there were no recent inputs of DDTs but fresh application of dicofol, which contains DDT (<i>o</i>,<i>p</i>′-DDT in particular) impurities. The significant positive correlation between concentrations of DDTs and total organic carbon content (TOC) indicates the distribution of DDTs fit a typical “secondary distribution” pattern. DEVrac of <i>o</i>,<i>p</i>′-DDD, which is defined as the absolute value of EFs subtracted from 0.5, was significantly related with most of the physicochemical and microbial soil properties. The most significant correlation is that between DEVrac of <i>o</i>,<i>p</i>′-DDD and soil pH (<i>p</i> < 0.001), indicating that the soil pH plays a key role in enantioselective residues of DDTs

Plant Uptake and Metabolism of 2,4-Dibromophenol in Carrot: In Vitro Enzymatic Direct Conjugation

Plants can extensively uptake organic contaminants from soil and subsequently transform them into various products. Those compounds containing hydroxyl may undergo direct conjugation with endogenous biomolecules in plants, and potentially be preserved as conjugates, thus enabling overlooked risk via consumptions of food crops. In this study, we evaluated the uptake and metabolism of 2,4-dibromophenol (DBP) by both carrot cells and whole plant. DBP was completely removed from cell cultures with a half-life of 10.8 h. Four saccharide conjugates, three amino acid conjugates, and one phase I metabolite were identified via ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry analysis. The dibromophenol glucopyranoside (glucose conjugate) was quantitated by synthesized standard and accounted for 9.3% of the initial spiked DBP at the end of incubation. The activity of glycosyltransferase was positively related to the production of 2,4-dibromophenol glucopyranoside (<i>p</i> = 0.02, <i>R</i>² = 0.86), implying the role of enzymatic catalysis involved in phase II metabolism

Cyanogel-Enabled Homogeneous Sb–Ni–C Ternary Framework Electrodes for Enhanced Sodium Storage

Antimony (Sb) represents an important high-capacity anode material for advanced sodium ion batteries, but its practical utilization has been primarily hampered by huge volume expansion-induced poor cycling life. The co-incorporation of transition-metal (M = Ni, Cu, Fe, <i>etc.</i>) and carbon components can synergistically buffer the volume change of the Sb component; however, these Sb–M–C ternary anodes often suffer from uneven distribution of Sb, M, and C components. Herein, we propose a general nanostructured gel-enabled methodology to synthesize homogeneous Sb–M–C ternary anodes for fully realizing the synergestic effects from M/C dual matrices. A cyano-bridged Sb­(III)–Ni­(II) coordination polymer gel (Sb–Ni cyanogel) has been synthesized and directly reduced to an Sb–Ni alloy framework (Sb–Ni framework). Moreover, graphene oxide (GO) can be <i>in situ</i> immobilized within the cyanogel framework, and after reduction, reduced graphene oxide (rGO) is uniformly distributed within the alloy framework, yielding a homogeneous rGO@Sb–Ni ternary framework. The rGO@Sb–Ni framework with optimal rGO content manifests a high reversible capacity of ∼468 mA h g^–1 at 1 A g^–1 and stable cycle life at 5 A g^–1 (∼210 mA h g^–1 after 500 cycles). The proposed cyanogel-enabled methodology may be extended to synthesize other homogeneous ternary framework materials for efficient energy storage and electrocatalysis

Residues of Currently and Never Used Organochlorine Pesticides in Agricultural Soils from Zhejiang Province, China

Studies on residues of currently and never used organochlorine pesticides (OCPs) facilitate the assessment of the contamination level, distribution, sources, transportation, and trend of these selected OCPs in China. In this work we investigated the concentration levels of endosulfans and chlordane, which are currently used, and the never used aldrin and dieldrin in the province of Zhejiang, a rainy, and hilly tea-growing province in eastern China. The average/mean residue levels of OCPs was in the order ∑endosulfan > ∑chlordane > aldrin > dieldrin. The residue level was in good agreement with the usage of OCPs in Zhejiang. The spatial distribution showed that the residues of OCPs in soils from the mountain area were always higher than those in soils from the plains. The distribution characteristics were related to usage for current-use OCPs and temperature for never used OCPs. The isomeric ratios and enantiomeric fractions are useful tools to identify the degradation preference of contaminants. The wide range of ratios between <i>trans</i>-chlordane (TC) and <i>cis</i>-chlordane (CC) indicated that the degradation of the two isomers of chlordane was different at different sites. Nonracemic residues of TC and CC were observed in most soils; this is significant since the enantiomers have different toxicities