Changes in profile distribution and chemical properties of natural nanoparticles in paddy soils as affected by long-term rice cultivation

Systematic studies on the genesis,properties,and distribution of natural nanoparticles(NNPs)in soil remain scarce.This study examined a soil chronosequence of continuous paddy field land use for periods ranging from 0 to 1000 years to determine how NNPs in soil changed at the early stages of soil genesis in eastern China.Soil samples were collected from coastal reclaimed paddy fields that were cultivated for 0,50,100,300,700,and 1000 years.Natural nanoparticles were isolated and characterized along with bulk soil samples(<2-mm fraction)for selected physical and chemical properties.The NNP content increased with increasing soil cultivation age at 60 g m^(-2) year-1,which was related to decreasing soil electrical conductivity(172-1297μS cm^(-1))and NNP zeta potentials(from -22 to -36 mV)with increasing soil cultivation age.Changes in several NNP properties,such as pedogenic iron oxide and total organic carbon contents,were consistent with those of the bulk soils across the soil chronosequence.Notably,changes in NNP iron oxide content were obvious and illustrated active chemical weathering,pedogenesis,and potential impacts on the microbial community.Redundancy analysis demonstrated that the soil cultivation age was the most important factor affecting NNP properties,contributing 60.7% of the total variation.Cluster and principal component analysis(PCA)revealed splitting of NNP samples into age groups of 50-300 and 700-1000 years,indicating rapid evolution of NNP properties,after an initial period of desalinization(approximately 50 years).Overall,this study provides new insights into NNP evolution in soil during pedogenesis and predicting their influences on agriculture and ecological risks over millennial-scale rice cultivation.

Characterization of FeCo Nanoparticles Reinforced Natural Rubber using Nanomechanical Mapping

The morphology, nanomechanical properties and interfacial regions of natural rubber（NR） and FeCo nanoparticles composite were determined by AFM nanomechanical mapping. The results showed that the size of FeCo particles was mostly from 40 to 100 nm and the FeCo nanoparticles were homogeneously dispersed in the NR bulk. The strength of NR composite increased with the FeCo nanoparticles loading. Young＇s modulus of NR region, FeCo region and interfacial region was measured by AFM nanomechanical tapping as 1.6 ± 0.6, 16.7 ±4.2 and 5.8 ± 1.5 MPa, respectively. The width of the interface for NR5, NR10 and NR15 was determined to be 15±8.1, 26±14.3 and 32±16.4 nm, respectively.

Simulation of oxygen transfer in liquid lead under influence of nanoparticles by using lattice Boltzmann method

Oxygen transfer presents a serious challenge in the application of liquid lead as a nuclear coolant in advanced reactors. To mitigate corrosion by liquid lead in contact with steel, carefully controlling the oxygen concentration has been used as an effective way. Oxygen needs to mix in liquid lead uniformly and quickly. To enhance oxygen transport in liquid lead, nanoparticles are added to the liquid metal. In the current study, a lattice Boltzmann method is applied to investigate natural convection of copper/lead and aluminum oxide/lead in two-dimensional simplified container. Two thermal boundary cases are evaluated in order to check the effect of different natural convection flow patterns on oxygen transport. Some useful information are obtained such as improvement in natural convection and reduction in oxygen equilibrium time.

Complex interplay between formation routes and natural organic matter modification controls capabilities of C_(60)nanoparticles(nC_(60)) to accumulate organic contaminants

Accumulation of organic contaminants on fullerene nanoparticles（nC（60）） may significantly affect the risks of C（60） in the environment.The objective of this study was to further understand how the interplay of nC（60） formation routes and humic acid modification affects contaminant adsorption of nC（60）.Specifically,adsorption of 1,2,4,5-tetrachlorobenzene（a model nonionic,hydrophobic organic contaminant） on nC（60） was greatly affected by nC（60）formation route- the formation route significantly affected the aggregation properties of nC（60）,thus affecting the available surface area and the extent of adsorption via the pore-filling mechanism.Depending on whether nC（60） was formed via the ＂top-down＂ route（i.e.,sonicating C（60） powder in aqueous solution） or ＂bottom-up＂ route（i.e.,phase transfer from an organic solvent） and the type of solvent involved（toluene versus tetrahydrofuran）,modification of nC（60） with Suwannee River humic acid（SRHA） could either enhance or inhibit the adsorption affinity of nC（60）.The net effect depended on the specific way in which SRHA interacted with C（60） monomers and/or C（60） aggregates of different sizes and morphology,which determined the relative importance of enhanced adsorption from SRHA modification via preventing C（60） aggregation and inhibited adsorption through blocking available adsorption sites.The findings further demonstrate the complex mechanisms controlling interactions between nC（60） and organic contaminants,and may have significant implications for the life-cycle analysis and risk assessment of C（60）.

A case study of aggregation behaviors of titanium dioxide nanoparticles in the presence of dodecylbenzene sulfonate in natural water

The present work aims to ascertain the mechanisms of surfactant（dodecylbenzene sulfonate; DBS） effects on the aggregation behaviors of TiO2 nanoparticles（TiO2-NPs） in natural water samples. Aggregation experiments were conducted at a TiO2-NPs concentration of 10 mg/L in deionized water and in natural water samples via dynamic light scattering and Zeta potential determination. Average attachment efficiency was calculated to compare the aggregation behaviors of nanoparticles in the two aqueous media. Results showed that the effects of DBS on aggregation could be interpreted by both Derjaguin–Landau–Verwey–Overbeek（DLVO） and non-DLVO mechanisms. In natural water samples,aggregation did not occur rapidly and was able to develop slowly under all conditions, and the roles of DBS were obvious at high DBS concentration owing to the impacts of inherent components of natural water samples, such as colloids and natural organic compounds.Future aggregation studies should concentrate on multi-factor, multi-colloidal and dynamic aspects under similar environmental conditions.

Sunlight-driven reduction of silver ion to silver nanoparticle by organic matter mitigates the acute toxicity of silver to Daphnia magna

Due to the unique antibacterial activities, silver nanoparticles（AgNPs） have been extensively used in commercial products. Anthropogenic activities have released considerable AgNPs as well as highly toxic silver ion（Ag^＋） into the aquatic environment.Our recent study revealed that ubiquitous natural organic matter（NOM） could reduce Ag^＋to Ag NP under natural sunlight. However, the toxic effect of this process is not well understood. In this work, we prepared mixture solution of Ag^＋and AgNPs with varied Ag^＋% through the sunlight-driven reduction of Ag^＋by NOM and investigated the acute toxicity of the solutions on Daphnia magna. Formation of AgNPs was demonstrated and characterized by comprehensive techniques and the fraction of unconverted Ag^＋was determined by ultrafiltration-inductively coupled plasma mass spectrometry determination. The formation of AgNPs enhanced significantly with the increasing of solution p H and cumulative photosynthetically active radiation of sunlight. The toxicity of the resulting solution was further investigated by using freshwater crustacean D. magna as a model and an 8 hr-median lethal concentration（LC50） demonstrated that the reduction of Ag^＋by NOM to AgNPs significantly mitigated the acute toxicity of silver. These results highlight the importance of sunlight and NOM in the fate, transformation and toxicity of Ag^＋and AgNPs,and further indicate that the acute toxicity of AgNPs should be mainly ascribed to the dissolved Ag^＋from AgNPs.