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Coinage metal (Au, Ag, Cu) cluster and polyoxometalate (POM) cluster represent two types of subnanometer "artificial atoms" with significant potential in catalysis, sensing, and nanomedicine. While composite clusters combining Ag/Cu clusters with POM have achieved considerable success, the assembly of gold clusters with POM is still lagging. Herein, we first designedly synthesized two cluster structural units: an Au3O cluster stabilized by diverse N-heterocyclic carbene (NHC) ligands and an amine-terminated POM linker. The subsequent reaction involved amine substitution in the POM linker for the central O atom in the Au3O cluster, resulting in the first ternary composite cluster - a POM cluster sandwiched by two Au clusters protected by NHCs. Single-crystal X-ray diffraction and other characteristic methods characterized their atomically precise structures. Furthermore, altering the NHC ligands decreased the number of gold atoms in the sandwich structures, accompanying the different protonated degrees of amine ligand in the terminal end of the POM linker. These composite clusters showed excellent performances in catalytic H2O2 conversion through the synergistic effect between gold clusters and POM clusters. This work opens a new avenue to functional composite metal clusters and would promote their enhanced catalysis applications through intercluster synergistic interactions within composite systems., (© 2024 Wiley‐VCH GmbH.)

Detailed photophysical processes of two AuCu 14 clusters with different substituents (-F or -C(CH 3 ) 3 ) of the thiol ligand were studied in this work. The electronic effect of the substituents led to structural shrinkage, thus enhancing the luminous intensity. The internal conversion (IC) and intersystem crossing (ISC) rates in the AuCu14-C(CH3)3 crystal were slower compared with the AuCu14-F crystal, which was caused by the steric effect.

Chemically modified superatoms have emerged as promising candidates in the new periodic table, in which Au 13 and its doped M n Au 13- n have been widely studied. However, their important counterpart, Ag 13 artificial element, has not yet been synthesized. In this work, we report the synthesis of Ag 13 nanoclusters using strong chelating ability and rigid ligands, that fills the gaps in the icosahedral superatomic metal clusters. After further doping Ag 13 template with different degrees of Au atoms, we gained insight into the evolution of their optical properties. Theoretical calculations show that the kernel metal doping can modulate the transition of the excited-state electronic structure, and the electron transfer process changes from local excitation (LE) to charge transfer (CT) to LE. This study not only enriches the families of artificial superatoms, but also contributes to the understanding of the electronic states of superatomic clusters., (© The Author(s) 2024. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.)

The specific states of aggregation of metal atoms in sub-nanometer-sized gold clusters are related to the different quantum confinement volumes of electrons, leading to novel optical and electronic properties. These volumes can be tuned by changing the relative positions of the gold atoms to generate isomers. Studying the isomeric gold core and the electron coupling between the basic units is fundamentally important for nanoelectronic devices and luminescence; however, appropriate cases are lacking. In this study, the structure of the first staggered di-superatomic Au 25 -S was solved using single-crystal X-ray diffraction. The optical properties of Au 25 -S were studied by comparing with eclipsed Au 25 -E. From Au 25 -E to Au 25 -S, changes in the electronic structures occurred, resulting in significantly different optical absorptions originating from the coupling between the two Au 13 modules. Au 25 -S shows a longer electron decay lifetime of 307.7 ps before populating the lowest triplet emissive state, compared to 1.29 ps for Au 25 -E. The experimental and theoretical results show that variations in the geometric isomerism lead to distinct photophysical processes owing to isomerism-dependent electronic coupling. This study offers new insights into the connection between the geometric isomerism of nanosized building blocks and the optical properties of their assemblies, opening new possibilities for constructing function-specific nanomaterials., (© 2024 Wiley-VCH GmbH.)

Enzymatic humification plays a crucial biogeochemical role in eliminating steroidal estrogens and expanding organic carbon stocks. Estrogenic contaminants in agroecosystems can be taken up and acropetally translocated by crops, but the roles of laccase-triggered rhizospheric humification (L-TRH) in pollutant dissipation and plant uptake remain poorly understood. In this study, the laccase-induced decontamination and humification mechanisms of 17β-estradiol (E2) in water-crop media were investigated by performing greenhouse pot experiments with maize seedlings ( Zea mays L.). The results demonstrated that L-TRH effectively dissipated E2 in the rhizosphere solution and achieved the kinetic constants of E2 dissipation at 10 and 50 μM by 8.05 and 2.75 times as much as the treatments without laccase addition, respectively. The copolymerization of E2 and root exudates (i.e. phenols and amino acids) consolidated by L-TRH produced a larger amount of humified precipitates with the richly functional carbon architectures. The growth parameters and photosynthetic pigment levels of maize seedlings were greatly impeded after a 120-h exposure to 50 μM E2, but L-TRH motivated the detoxication process and thus mitigated the phytotoxicity and bioavailability of E2. The tested E2 contents in the maize tissues initially increased sharply with the cultivation time but decreased steadily. Compared with the treatment without laccase addition, the uptake and accumulation of E2 in the maize tissues were obviously diminished by L-TRH. E2 oligomers such as dimer, trimer, and tetramer recognized in the rhizosphere solution were also detected in the root tissues but not in the shoots, demonstrating that the acropetal translocation of E2 oligomers was interrupted. These results highlight a promising strategy for decontaminating estrogenic pollutants, boosting rhizospheric humification, and realizing low-carbon emissions, which would be beneficial for agroenvironmental bioremediation and sustainability., (© The Author(s) 2024. Published by Oxford University Press on behalf of National Academy of Sciences.)

Materials exhibiting X-ray-induced photochromism have consistently piqued the interest of researchers. Exploring the photochromic properties of such materials is valuable for understanding the structural changes and electron transfer processes that occur under high energy radiation, such as X-ray irradiation. Here, a crystalline silver(I) nanocluster synthesized from tert -butylacetylene silver was found to have the ability to exhibit color and photoluminescence changes upon exposure to X-ray radiation. The responsive behavior was observed across a wide temperature range of 100-300 K, with the ability to respond particularly well to soft X-rays ( λ > 1 Å) and exhibit light responsiveness to hard X-rays ( λ < 1 Å). By combining experimental findings including X-ray diffraction, X-ray photoelectron spectroscopy, electron spin resonance, etc. with theoretical calculations, we have proposed that X-ray irradiation induces electron transfer from chloride (Cl - ) located in the center of the silver(I) nanocluster to the surrounding Ag 14 in the skeleton. This represents the first documented example in which electron transfer induced by X-ray excitation has been observed, accompanied by a photochromism process, in silver nanoclusters. This study contributes to our understanding of X-ray-induced photochromism and the electron transfer process in silver cluster compounds. It also provides valuable insights and potential design strategies for applications such as photochromism, photoluminescence color change, and photoenergy conversion.

This work elucidates the potential impact of intramolecular H-bonds within the pore walls of covalent organic frameworks (COFs) on proton conductivity. Employing DaTta and TaTta as representative hosts, it was observed that their innate proton conductivities (σ) are both unsatisfactory and σ(DaTta)<σ(TaTta). Intriguingly, the performance of both imidazole-loaded products, Im@DaTta and Im@TaTta is greatly improved, and the σ of Im@DaTta (0.91×10 -2  S cm -1 ) even surpasses that of Im@TaTta (3.73×10 -3  S cm -1 ) under 100 °C and 98 % relative humidity. The structural analysis, gas adsorption tests, and activation energy calculations forecast the influence of imidazole on the H-bonded system within the framework, leading to observed changes in proton conductivity. It is hypothesized that intramolecular H-bonds within the COF framework impede efficient proton transmission. Nevertheless, the inclusion of an imidazole group disrupts these intramolecular bonds, leading to the formation of an abundance of intermolecular H-bonds within the pore channels, thus contributing to a dramatic increase in proton conductivity. The related calculation of Density Functional Theory (DFT) provides further evidence for this inference., (© 2023 Wiley-VCH GmbH.)

X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal-organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm -1 ., (© 2023 Wiley-VCH GmbH.)

X-ray scintillators are widely used in medical imaging, industrial flaw detection, security inspection, and space exploration. However, traditional commercial scintillators are usually associated with a high use cost because of their substantial toxicity and easy deliquescence. In this work, an atomically precise Au-Cu cluster scintillator ( 1 ) with a thermally activated delayed fluorescence (TADF) property was facilely synthesized, which is environmentally friendly and highly stable to water and oxygen. The TADF property of 1 endows it with an ultrahigh exciton utilization rate. Combined with the effective absorption of X-ray caused by the heavy-atom effect and a limited nonradiative transition caused by close packing in the crystal state, 1 exhibits an excellent radioluminescence property. Moreover, 1 has good processability for fabricating a large, flexible thin-film device (10 cm × 10 cm) for high-resolution X-ray imaging, which can reach 40 μm (12.5 LP mm -1 ). The properties mentioned earlier make the coinage metal cluster promising for use as a substitute for traditional commercial scintillators., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Chiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N-heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au 13 clusters. This new enantiomeric pair of clusters has a quasi-C 2 symmetric core and exhibited CPL with an unprecedent solution-state quantum yield (QY) of 61 % among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters., (© 2023 Wiley-VCH GmbH.)

In order to study the effect of nanosilver on soil nitrification microorganisms and nitrogen transformation, soil culture experiments were carried out. Yellow brown soil and paddy soil were first spiked with different doses of nanosilver (10, 50, 100 mg·kg -1 ) and silver ions (1, 5, 10 mg·kg -1 ). Then, the number of nitrifying bacteria, activity of soil invertase, amoA gene abundance, NH 4 + -N content, NO 3 - -N content, and soil potential ammonia oxidation rate were determined. The results showed that the number of nitrite bacteria and nitrate bacteria decreased significantly when the soils were treated with nanosilver and silver ions. Soil invertases were inhibited, and the effect on urease was greater than that on catalase. The amoA gene abundances of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) decreased, and the effect on the gene abundance of AOB was greater than that of AOA. When (NH 4 ) 2 SO 4 was added to the soil, nanosilver and silver ion pollutants caused NH 4 + -N to accumulate, and the contents of NO 3 - -N were reduced, the rate of ammonia oxidation decreased, and the transformation of ammonium nitrogen to nitrate nitrogen was inhibited. This research suggests that nanosilver and silver ions can have toxic effects on soil nitrification microorganisms and ammonium nitrogen conversion, and the degree of influence was found to be related to the soil physical and chemical properties.

The increasing use of silver-containing nanoparticles (NPs) in commercial products has led to NP accumulation in the environment and potentially in food webs. Identifying the uptake pathways of different chemical species of NPs, such as Ag 2 S-NP and metallic AgNPs, into plants is important to understanding their entry into food chains. In this study, soybean Glycine max L. was hydroponically exposed to Ag 2 S-NPs via their roots (10-50 mg L -1 ) and stable-isotope-enriched 109 AgNPs via their leaves [7.9 μg (g fresh weight) -1 ]. Less than 29% of Ag in treated leaves (in direct contact with 109 AgNP) was accumulated from root uptake of Ag 2 S-NPs, whereas almost all of the Ag in soybean roots and untreated leaves sourced from Ag 2 S-NPs. Therefore, Ag 2 S-NPs are phytoavailable and translocate upward. During trophic transfer the Ag isotope signature was preserved, indicating that accumulated Ag in snails most likely originated from Ag 2 S-NPs. On average, 78% of the Ag in the untreated leaves was assimilated by snails, reinforcing the considerable trophic availability of Ag 2 S-NPs via root uptake. By highlighting the importance of root uptake of Ag 2 S-NPs in plant uptake and trophic transfer to herbivores, our study advances current understanding of the biogeochemical fate of Ag-containing NPs in the terrestrial environment.

Mercury is harmful to the environment, which has gradually become one of the research hotspots. Sediments, as a main repository of pollutants, have an important impact on water quality and the internal organisms, which deserves our research. In this paper, we focused on Hefei landscape water sediment and tried to investigate the status of inorganic mercury and methylmercury pollutions in the sediment. To study the conversion process from inorganic mercury to methylmercury and their enrichment levels and mechanism, we established the ecological chain of "sediment-water-grass-fish" through analog microcosm examination. The results were as follows: from ten water and sediment samples in Hefei landscape water sediment, we found that the contents of inorganic mercury and methylmercury ranged 11.74-13.12 µg · kg⁻¹ and 0.37-2.23 µg · kg⁻¹, respectively. The microcosm examination showed that: with increasing culture time, inorganic mercury in sediments gradually decreased. There was a phenomenon that the content of methylmercury increased at first and then decreased to reach the balance later. Both the inorganic mercury and methylmercury in water change showed an increasing trend. The enrichment contents of inorganic mercury in Egeria densa Planch, and golden mandarin fish (Siniperca scherzeri Steindachner) were low while their enrichment of methylmercury could he great. In addition, we found that both the bioaccumulation ability and the enrichment coefficient of methylmercury in the body of golden mandarin fish were the maximum during the same period.

The effects of solid-state NaOH pretreatment on the efficiency of methane production from semi-dry anaerobic digestion of rose (Rosa rugosa) stalk were investigated at various NaOH loadings (0, 1, 2, and 4% (w/w)). Methane production, process stability and energy balance were analyzed. Results showed that solid-state NaOH pretreatment significantly improved biogas and methane yields of 30-day anaerobic digestion, with increases from 143.7 mL/g volatile solids (VS) added to 157.1 mL/g VS -192.1 mL/g VS added and from 81.8 mL/g VS added to 88.8 mL/g VS-117.7 mL/g VS added, respectively. Solid-state NaOH pretreatment resulted in anaerobic digestion with higher VS reduction and lower technical digestion time. The 4% NaOH-treated group had the highest methane yield of 117.7 mL/g VS added, which was 144% higher compared to the no NaOH-treated group, and the highest net energy recovery. Higher rate of lignocellulose breakage and higher process stability of anaerobic digestion facilitated methane production in the NaOH-pretreated groups.

Fe(III) dissimilatory reduction by microbes is an important process of producing energy in the oxidation of organic compounds under anaerobic condition with Fe(III) as the terminal electron acceptor and Fe(II) as the reduction product. This process is of great significance in element biogeochemical cycle. Iron respiration has been described as one of the most ancient forms of microbial metabolism on the earth, which is bound up with material cycle in water, soil and sediments. Dissimilatory iron reduction plays important roles in heavy metal form transformation and the remediation of heavy metal and radionuclide contaminated soils. In this paper, we summarized the research progress of iron reduction in the natural environment, and discussed the influence and the mechanism of dissimilatory iron reduction on the speciation and bioavailability of heavy metals in soil. The effects of dissimilatory iron reduction on the speciation of heavy metals may be attributed to oxidation and reduction, methytation and immobilization of heavy metals in relation to their bioavailability in soils. The mechanisms of Fe(III) dissimilatory reduction on heavy metal form transformation contain biological and chemical interactions, but the mode of interaction remains to be further investigated.

The effects of the biological dissolution and reduction of goethite on mercury methylation by Shewanella oneidensis MR-1 were studied under laboratory conditions. The results showed that S. oneidensis MR-1 could dissolve goethite, and subsequently dissolved Fe3+ which was reduced to Fe2+. S. oneidensis MR-1 was also a kind of mercury methylation bacterial, which had a potential to transform inorganic mercury to methylmercury. The biological dissolution and reduction of goethite declined with the increasing initial dosage of goethite. The dissimilatory reduction of goethite could promote mercury methylation to a certain extent. Weakly acidic condition was more beneficial to mercury methylation than neutral, alkaline or highly acidic conditions. Low humic acid concentration

The biological dissolution and methylation of solid HgS by Shewanella oneidensis MR-1 and influenced factors under laboratory conditions were studied. Results showed that S. oneidensis MR-1 could grow well at the low concentration of Na2S, but its growth was inhibited at the high concentration of Na2S, which mainly happened in the prolonged lag phase. Iron reducing bacteria S. oneidensis MR-1 could access the solid mercuric sulfide, and rapidly promote the biological dissolution and methylation of HgS. In the appropriate range of sulfide to S. oneidensis MR-1, the biological solubility of HgS was enhanced with the increasing concentration of Na2S, but the methylation just promoted at the low Na2S concentration, and it would be inhibited when the concentration is high. In addition, weakly acidic environment was more beneficial to biological dissolution and methylation of HgS than acidic, neutral or alkaline conditions by S. oneidensis MR-1.

Objective: To explore the risk factors of primary open angle glaucoma (POAG) in women., Methods: This retrospective, case-control study collected 128 female patients with POAG and 142 female with normal controls without POAG from 2009 to 2010. The risk factors including family history, hypertension, diabetes, age of menarche, age of menopause, parity, oral contraceptive (OC) use, hormone therapy were analyzed by logistic regression analysis., Results: Compared with normal control group using logistic regression analysis, there were significant differences in such risk factors in POAG group as family history (OR = 43.36, 95%CI: 5.69 - 346.67; P < 0.001), hypertension(OR = 3.29, 95%CI: 1.82 - 5.94; P < 0.001), age of menarche (OR = 2.046, 95%CI: 1.17 - 3.54; P = 0.011), age of menopause (OR = 0.57, 95%CI: 0.32 - 0.99; P = 0.049), hormone therapy (OR = 0.29, 95%CI: 0.09 - 0.92; P = 0.036)., Conclusions: Family history and hypertension are high risk factors to develop POAG for women. However, female hormones may play a protective role in women with POAG.

Mercury methylation by Geobacter sulfurreducens and the effects of environmental factors were studied under laboratory conditions. The results showed that G. sulfurreducens could grow well in the presence of low concentrations of mercuric chloride, but its growth was inhibited to a certain extent, mainly expressed in the prolonged lag phase. G. sulfurreducens could transform inorganic mercury into methylmercury, and this process was affected by many environmental factors. The efficiency of mercury methylation reached 38% under anaerobic conditions with 1 mg x L(-1) HgCl2 and 0.9% salinity at 35 degrees C, pH 6.0. Increasing the initial HgCl2 concentration or salinity in an appropriate manner improved mercury methylation, but the concentration of methylmercury reduced when the concentrations of HgCl2 and salinity were too high. The efficiency of mercury methylation increased with the increasing temperature in range of 4-35 degrees C. Weakly acidic environment was more beneficial to mercury methylation than acidic, neutral or alkaline conditions. In addition, the efficiency of mercury methylation was also affected by humic acid and cysteine. Humic acid inhibited mercury methyaltion, whereas cysteine could improve the efficiency of mercury methylation. This study provided a direct evidence for mercury methylation mediated by iron-reducing bacteria in the natural aquatic ecosystem.

Competitive adsorption kinetics of aqueous Pb2+ and Cu2+ on Nano-HAP surfaces were investigated by performing the adsorption kinetic experiments and comparing the change of zeta potentials and XRD-map before and after metal adsorption. The results showed that the adsorption quantity of Pb2+ on Nano-HAP was higher than that of Cu2+ in the single system. However, the competitive adsorption of Pb2+ and Cu2+ occurred in the co-existence system of Pb2+ and Cu2+. The adsorption quantity of Cu2+ on Nano-HAP increased, while that of Pb2+ decreased. The X-ray diffraction (XRD) and adsorption quantities of Ca2+ surface analysis indicated that dissolution-precipitation is the primary immobilization mechanism for Pb2+, while surface complexation and electrostatic adsorption account for Cu2+ sequestration. The adsorption quantities of Pb2+ and Cu2+ on Nano-HAP had marked linear relationship with Ca2+ release from Nano-HAP (R2 0.861-0.954). The adsorption kinetics were fitted with the equations of first-order, second-order, parabola, Elovich, double constant equation and LJ function, respectively, in which the second-order and power function kinetics equation fitted the results best. According to above results, the adsorption kinetics of Pb2+ and Cu2+ on Nano-HAP is a complex adsorption processes with both chemical reaction and physical adsorption.

Quartz sand was selected as collector and saturated packed column was constructed to explore the effects of environmental factors (humic acid, pH and ionic strengths of the bulk solution) on the transport and fate of hydroxyapatite nanoparticles (Nano-HAP) through measuring zeta potentials and representative c(i)/c(0) of Nano-HAP. It was suggested that zeta potentials of Nano-HAP colloids became more negative with increasing humic acid concentration and the change in solution composition from 0 to 10 mg/L humic acid yielded an increase in the zeta potentials of Nano-HAP colloids from -15 mV to -55 mV and a sharp decrease in a (attachment efficiency) from 1.0 to 0.012, meanwhile, the increase in bulk solution pH yielded a slight decrease in a which enhancing its transportation in saturated packed column. However, zeta potentials of Nano-HAP colloids became less negative as the ionic strength of bulk solution increased due to the compression of diffuse double layer and yielded an increase in a which greatly impeded its mobility during the pore-water solution, meanwhile, divalent cations have significantly stronger influence on the transport of Nano-HAP than monovalent cations of the bulk solution. The increase in the concentration of monovalent cation (Na+) from 1 to 100 mmol/L yielded an increase in a from 0.030 to 0.13, and divalent cations (Ca2+) from 0.2 to 10 mmol/L yielded a greatly increase in alpha from 0.030 to 1.0. It is important to note that the results could considerably contribute to gain insights in the transport and fate of Nano-HAP in natured and engineered porous media.

Reductive transformation of 2,4-Dichlorophenoxyacetic acid (2,4-D) by nanoscale Fe3O4 was studied, and the effects of 2,4-D initial concentration, the dosage of nanoscale Fe3O4, pH and temperature on degradation rate of 2,4-D were investigated. The results showed that 48% 2,4-D with initial concentration of 10 mg/L was transformed within 48 h in the presence of 300 mg/L nanoscale Fe3O4. The degradation of 2,4-D was a reductive dechlorination process, and the concentration of chloride ion increased sharply with the degration of the 2,4-D. Disappearance of parent species and formation of reaction intermediates and products were analyzed by LC/MS. The transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP) and phenol. The degradation equations of 2,4-D by nanoscale Fe3O4 conformed to pseudo-first-order kinetics, and the reaction rate constant (K) of 4-CP, 2,4-DCP and phenol were 0.0043 h(-1), 0.0026 h(-1) and 0.0032 h(-1), respectively. The degradation rate increased with an increase in initial concentration of 2,4-D from 0 mg/L to 10 mg/L, and increasing the dosage of nanoscale Fe3O4 from 0 mg/L to 300 mg/L. The pH of reaction solution significantly influenced reductive degradation of 2,4-D, and the optimum pH value was 3.0. Besides, high temperature could improve dechlorination rate of 2,4-D.

Reductive transformation of 2,4-dichlorophenoxyacetic acid (2,4-D) by nanoscale and microscale Fe(3)O(4) was investigated and compared. Disappearance of the parent species and formation of reaction intermediates and products were kinetically analyzed. Results suggest that the transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), chlorophenol (2-CP, 4-CP) and phenol. About 65% of 2,4-D with initial concentration of 50 micro M was transformed within 48 h in the presence of 300 mg L(-1) nanoscale Fe(3)O(4), and the reaction rates increased with increasing dosage of nanoscale Fe(3)O(4). The decomposition of 2,4-D proceeded rapidly at optimum pH 3.0. Chloride was identified as a reduction product for 2,4-D in the magnetite-water system. Reductive transformation of 2,4-D by microscale Fe(3)O(4) was slower than that by nanoscale Fe(3)O(4). The reactions apparently followed pseudo-first-order kinetics with respect to the 2,4-D transformation. The degradation rate of 2,4-D decreased with the increase of initial 2,4-D concentration. In addition, anions had a significant adverse impact on the degradation efficiency of 2,4-D.

Photolysis of bensulfuron-methyl on soil surface was studied under sunlight and UV light. Seven photoproducts were isolated and characterised by spectroscopic methods. The major processes in the photolysis of bensulfuron-methyl in soil are cleavage of the sulfonylurea bridge, scission of the SO2NH bond and contraction of the sulfuronylurea bridge. The rates of photodegradation of bensulfuron-methyl on different soils followed first-order rate kinetics with half lives of 21.9, 28.4, 36.9, 59.2 and 47.2 h (UV) and 23.1, 27.5, 29.1, 38.9 and 33.8 days (sunlight) for vertisol, alluvial, alfisol, red and laterite soils, respectively. The differences in rates of photodegradation were dependent upon the soil texture and organic matter content.

The electrokinetic removal of chromium and copper from contaminated soils by adding lactic acid in cathode chamber as an enhancing reagent was evaluated. Two sets of duplicate experiments with chromium contaminated kaolinite and with a silty soil sampled from a superfund site in California of USA and polluted by Cr and Cu, were carried out in a constant current mode. Changes of soil water content and soil pH before and after the electrokinetic experiments, and variations of voltage drop and electroosmosis flow during the treatments were examined. The results indicated that Cr, spiked as Cr( VI ) in the kaolinite, was accumulated mainly in the anode chamber, and some of Cr and metal hydroxides precipitated in the soil sections in contact with the cathode, which significantly increased electrical energy consumption. Treatment of the soil collected from the site showed accumulation of large amounts of Cr and Cu in the anode chamber while none was detected in the cathode one. The results suggested that the two metals either complexed with the injected lactic acid at the cathode or existed as negatively charged complex, and electromigrated toward the anode under a voltage gradient.

Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water-soluble and exchangeable(SE), weakly specific adsorbed(WSA), Fe and Mn oxides-bound(OX) and organic-bound(ORG). The results showed that fractions of heavy metals in the soil subsamples depended on their speciation. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil subsamples as SE, WSA and OX fractions simultaneously, although SE was still the major fraction. Organic-bound heavy metals were not clearly apparent in all the soil subsamples. The concentration of some heavy metal fractions in soil subsamples showed the good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with 0.20 mol/L NH4Cl, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil subsamples depended greatly on pH, the composition and original heavy metal content of the soil subsamples. However, most of the heavy metals in the soil subsamples were still be retained after multiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did not show difference significantly from that of the parent one by statistical analysis. Heavy metals existed in the soil subsamples mainly as exchangeable and precipitated simultaneously.