Photoreduction is a major obstacle for using the X-ray absorption near-edge structure (XANES) fingerprint to perform metal speciation at the molecular level in biological and environmental samples, especially for metalloproteins. In this study, soft X-ray induced photoreduction was observed in organic Cu(II) compounds during XANES measurements in a third-generation synchrotron source. Next Cu L3-edge, O K-edge, and C K-edge XANES spectroscopy, together with the scanning transmission X-ray microscopy (STXM), were used to probe the specific radiation damage processes of Cu acetate with similar local structures to Cu metalloproteins. Breakup of the Cu–Cu bond was hypothesized for the initial photoreduction of Cu acetate. The following radiation damage of Cu acetate produced CuO and an organic Cu(I) compound with a C═C bond, and the further photoreduction of the resulting CuO to Cu metal was also demonstrated. Our results indicated the importance of consideration of photoreduction during soft XANES measurements for the solid state compounds with high valence metals. Reducing the radiation dose to ∼0.1 MGy effectively prevented the photoreduction of organic Cu(II) compounds during these measurements. This proposed radiation damage mechanism in Cu acetate may be generally useful in explaining the photoreduction process in Cu metalloproteins.

The primitive recycling of electronic waste (e-waste) in developing countries is causing serious environmental pollution. The objective of this study was to determine the contamination and toxicity of surface sediment of Nanguan River, which runs through the e-waste recycling area of Taizhou, East China.Surface sediments were collected from Nanguan River, including one from the control site, four near the household workshops, and two near the industrial parks. Levels of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals/metalloid (Ni, Pb, Cd, Cr, Zn, Cu, Hg, and As), which are most widely detected in e-waste contaminated surroundings, were determined. Acute toxicity and genetic toxicity were evaluated by luminescence inhibition assay in luminescent bacterium Vibrio qingaiensis sp. nov. (Q67) and Vicia faba roots tip micronucleus assay, respectively.The surface sediment has been seriously contaminated by PCBs, PAHs, and heavy metals/metalloid due to the e-waste disassembly process. Significant acute and genetic toxicity of the sediments presented a big threat to the aquatic life and human health through food chain, as the river is an extent water source for local residents.The environmental issue of e-waste recycling is emergent and measures should be taken to mitigate the adverse impacts of e-waste disassembly.

To study the oxidative stress and antioxidative response of Cinnamomum camphora seedlings exposed to nitrogen dioxide (NO2) fumigation.Measurements were made up of the growth, chlorophyll content, chlorophyll fluorescence, antioxidant system and lipid peroxidation of one-year-old C. camphora seedlings exposed to NO2 (0.1, 0.5, and 4 μl/L) fumigation in open top chambers over a period of 60 d.After the first 30 d, 0.5 and 4.0 μl/L NO2 showed insignificant effects on the growth of C. camphora seedlings. However, exposure to 0.5 and 4.0 μl/L NO2 for 15 d significantly reduced their chlorophyll content (P<0.05), enhanced their malondialdehyde (MDA) content and superoxide dismutase (SOD) activity (P<0.05), and also significantly reduced the maximal quantum yield of PSII in the dark [the ratio of variable fluorescence to maximal fluorescence (Fv/Fm)] (P<0.05). In the latter 30 d, 0.5 μl/L NO2 showed a positive effect on the vitality of the seedlings, which was reflected by a recovery in the ratio of Fv/Fm and chlorophyll content, and obviously enhanced growth, SOD activity, ascorbate (AsA) content and glutathione reductase (GR) activity (P<0.05); 4.0 μl/L NO2 then showed a negative effect, indicated by significant reductions in chlorophyll content and the ratio of Fv/Fm, and inhibited growth (P<0.05). Conclusion: The results suggest adaptation of C. camphora seedlings to 60-d exposure to 0.1 and 0.5 μl/L NO2, but not to 60-d exposure to 4.0 μl/L NO2. C. camphora seedlings may protect themselves from injury by strengthening their antioxidant system in response to NO2-induced oxidative stress.

The objective in the first phase of this study was to screen four plant species (alfalfa, ryegrass, tall fescue and rice) for phytoremediation of aged polychlorinated biphenyl (PCB)-contaminated soil from an electronic and electric waste (e-waste) recycling site. Glucose, biphenyl and three surfactants (TritonX-100, randomly methylated-β-cyclodextrins and β-cyclodextrin) were used to enhance the phytoremediation process. During the second phase, the focus was rhizosphere characteristics and plant uptake to investigate the mechanism of PCB removal from soil. In the first phase, all the tested plant species showed a significantly greater PCB removal percentage compared to the unplanted controls, while different amendments showed no significant difference. The most effective plant (ryegrass) combined with β-cyclodextrin was selected for further studies. During the rhizosphere characteristics and plant uptake study, the highest PCB removal percentage (38.1%) was observed in the ryegrass planted soil when β-cyclodextrin was amended at 1.0% (w/w). The presence of plants significantly increased the biological activity (microbial counts and enzyme activity) of both β-cyclodextrin amended and non-amended soils. Higher levels of PCB removal were closely related to greater microbial counts and soil enzyme activities by correlation analysis. After 120 days of plant growth, ryegrass accumulated 708.7–820.1 ng PCBs/g in the root and 71.7–110.8 ng PCBs/g in the shoot, resulting in about 0.08% PCBs removal from soil. It was concluded that high PCB degradation was due to the increased PCB bioavailability as well as biostimulation of microbial communities after plantation and β-cyclodextrin addition. Furthermore, results suggested that PCB removal was mainly contributed by microbial degradation rather than plant uptake or abiotic dissipation.

Elsholtzia splendens is generally considered as a Cu-tolerant and -accumulating plant species, and a candidate for phytoremediation of Cu-contaminated soils. To better understand the Cu tolerance/accumulation mechanisms in E. splendens, proteomic analysis was performed on E. splendens roots and leaves exposed to 100 μM CuSO4 for 3 and 6 days. After 6 days of treatment, Cu accumulation in roots increased much more than that in leaves. SDS–PAGE analysis showed that the proteins changed more intensively in roots than did in leaves upon Cu stress. Two-dimensional gel electrophoresis (2-DE) and image analyses found that 45 protein spots were significantly changed in roots, but only six protein spots in leaves. The abundance of protein spots mostly showed temporal changes. MALDI-TOF MS and LTQ-ESI-MS/MS were used to identify the differently expressed protein spots. The identified root proteins were involved in various cellular processes such as signal transduction, regulation of transcription and translation, energy metabolism, regulation of redox homeostasis and cell defense. The leaf proteins were mainly degraded fragments of RuBisCo and antioxidative protein. The roles of these proteins in Cu tolerance/accumulation were discussed. The resulting differences in protein expression pattern suggested that redirection of root cellular metabolism and redox homeostasis might be important survival mechanisms of E. splendens upon Cu stress.

The bioavailability and potential toxicity of sediment-associated organic compounds are affected by sorption processes. The particulate matter (ash) from field burning of crop residues is one of the primary sources for environmental black carbon, which is regarded as supersorbent for organic contaminants and may reduce their ecotoxicity. This study aimed to investigate the influence of ash on sediment-associated organic pollutants’ potential toxicity.Pentachlorophenol (PCP) and pyrene (PYE) were chosen as the target organic pollutants, earthworms (Eisenia fetida) were used to evaluate the genotoxicity of contaminated sediments in the exposure experiments, and the genotoxicity (expressed as DNA damage) was quantified by comet assay. Sediments amended with different levels of ash (1%, 3%, 5%, and 10%) were selected as the sorbent to investigate the influence of ash on the sorption and genotoxicity of sediment-associated organic compounds. In order to study the toxic effect of ash, the ash-amended sediments without pollutants addition were adopted as exposure systems in the comet assay.The sorption capacity for PCP and PYE increased with ash content in the sediment. The high adsorptivity of ash was attributed to the black carbon contained in the ash, which is in line with many previous studies. When spiked at a concentration of 200 μg/kg, both PCP and PYE exerted significant genotoxic effect on earthworms. The genotoxicity of sediment-associated pollutants decreased as the ash content in sediment increased. The DNA damage in the 5% ash-amended exposure showed no significant difference with that in the control exposure, probably due to the strong sorption capactiy of ash, which decreased bioavailability as well as toxicity of sediment-associated pollutants. However, the 10% ash treatment had a higher DNA lesion than that in the 5% char-added exposure. This may have been caused by the genotoxic compounds and high alkalinity contained in the ash.Addition of ash increased sorption and inhibited the genotoxicity of sediment-associated organic toxicants. When added at a high rate (e.g., 10%), ash could also exert genotoxic effect. As field burning is a common land-cleaning method in many agricultural areas, the ecological influence of ash should be given much attention in the future study. More research should be conducted to better understand the mechanism of toxic effect of ash.

In recent years, increasing concern has surrounded the consequences of improper electric and electronic waste (e-waste) disposal. In order to mitigate or remediate the potentially severe toxic effects of e-waste recycling on the environment, organisms, and humans, many contaminated sites must first be well-characterized. In this study, soil samples were taken from Taizhou city, one of the largest e-waste disposal centers in China, which was involved in recycling for nearly 30 years. The extracts of the samples were assayed for aryl hydrocarbon receptor (AhR)-mediated ethoxyresorufin-O-deethylase (EROD) induction in the rat hepatoma cell line H4IIE. Some of the target AhR agonists, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs), were instrumentally analyzed as well. The cause−effect relationship and dose–response relationship between the chemical concentrations of AhR agonists and observed EROD activity were examined. The results showed that soil extracts could induce AhR activity significantly, and the chemically derived 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents (TEQcal) were perfectly correlated to bioassay-derived TCDD equivalents (TEQbio; R = 0.96, P < 0.001), which indicated that the known AhR agonists could account for the observed responses. Among different contributors, PCBs accounted for 87.2–98.2% and PCDD/Fs contributed 1.7–11.6% of TEQcal, while the contribution of PAHs could almost be neglected. Under these conditions, a quantitative dose–effect relationship between TEQPCB and EROD activity could be evaluated, suggesting that the observed AhR effect was mainly caused by PCBs. Further source identification by congener profiles analysis showed that the crude dismantling of electric power devices and open burning of electric wires and printed circuit boards may be the main sources of these dioxin-like compounds. This study suggests that the combination of in vitro bioassay and chemical analysis is useful to screen, identify, and prioritize AhR agonists in soil from e-waste recycling areas.

Previously performed studies have shown that Pseudomonas putida CZ1 biomass can bind an appreciable amount of Cu(II) and Zn(II) ions from aqueous solutions. The mechanisms of Cu- and Zn-binding by P. putida CZ1 were ascertained by chemical modifications of the biomass followed by Fourier transform infrared and X-ray absorption spectroscopic analyses of the living or nonliving cells. A dramatic decrease in Cu(II)- and Zn(II)-binding resulted after acidic methanol esterification of the nonliving cells, indicating that carboxyl functional groups play an important role in the binding of metal to the biomaterial. X-ray absorption spectroscopy was used to determine the speciation of Cu ions bound by living and nonliving cells, as well as to elucidate which functional groups were involved in binding of the Cu ions. The X-ray absorption near-edge structure spectra analysis showed that the majority of the Cu was bound in both samples as Cu(II). The fitting results of Cu K-edge extended X-ray absorption fine structure spectra showed that N/O ligands dominated in living and nonliving cells. Therefore, by combining different techniques, our results indicate that carboxyl functional groups are the major ligands responsible for the metal binding in P. putida CZ1.

Controversy still exists over whether photocatalytic oxidation proceeds via OH radicals, valence band holes, O2− or H2O2. In this paper, the role of these primary oxidants in the photodegradation of an azo dye, Acid Orange 7 (AO7) in UV-illuminated TiO2 suspension was investigated. Little influence of methanol or isopropanol on the degradation indicated that the oxidation was not primarily proceeding by reaction between OH radicals and AO7, because alcohols could effectively scavenge OH radicals. But the presence of I− (hole scavenger) significantly inhibited the degradation, thus suggesting that holes played a major role. Then, experiments carried out in acetonitrile, methanol or isopropanol solvent confirmed the major role of holes, since OH radicals were minimized in dry solvent. In addition, it was suggested that O2− and H2O2 had a negligible effect when Cr(VI) was used as electron scavenger instead of O2. The effects of surface modification by F− or SO42− on the initial steps of photodegradation were also investigated. The hydroxyl groups on the surface of TiO2 were replaced by F− or SO42− and there were little adsorbed AO7 molecules to be trapped by hole, so the initial process could shift progressively from hole-dominated surface reaction to homogeneous radical reaction in bulk solution. Discussion about the relationship between adsorption and photodegradation indicated that the degradation rate was not strongly affected by the actual location amount of organics on TiO2 surface.

Elsholtzia splendens is a copper tolerant plant growing in copper mine areas in south of China and accumulates considerable heavy metals in plant tissue. In this study, synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) microprobe was used to study the Cu and other elements distribution in E. splendens. The element (P, S, Cl, K, Ca, Mn, Fe, Cu, Zn) in the leaf epidermis and cross-sections of the stem and leaf could be checked by SRXRF which was considered a sensitive technique for trace element analysis. The highest Cu levels were measured in the vascular tissues of stem and petiole, while Cu levels in mesophyll were higher than in leaf epidermis. The levels of most elements were not higher in trichomes than in other tissues. It seems that the celluar compartmentation of heavy metals in epidermis and epidermal trichomes was not the general feature of all plants. There was a significant correlation between Cu and P, S, Ca in distribution, which suggested P, S, and Ca played an important role in Cu accumulation of E. splendens. Based on the significant correlation between Cu and elements Mn, Fe, and Zn in distribution, it seemed that Cu, Mn, Fe, and Zn could be transported by the same transporters with a broad substrate range.

In this paper, silica gel supported titanium dioxide particles (TiO2/SiO2) prepared by acid-catalyzed sol–gel method was as photocatalyst in the degradation of acid orange 7 (AO7) in water under visible light irradiation. The particles were characterized by X-ray diffraction, BET specific surface area determination, and point of zero charge measurement. The supported catalyst had large surface area, high thermal stability and good sedimentation ability. The photodegradation rate of AO7 under visible light irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The photodegradation rate of AO7 using 31% TiO2/SiO2 particles was faster than that using P-25 and TiO2 (Shanghai) as photocatalyst by 2.3 and 12.3 times, respectively. The effect of the calcination temperature and the TiO2 loading on the photoactivity of TiO2/SiO2 particles was also discussed.

The environmental risk of heavy metal pollution is pronounced in soils adjacent to large industrial complexes. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by heavy metals. We studied the potential effects of heavy metals on microbial biomass, activity, and community composition in soil near a copper smelter in China. The results showed that microbial biomass C was negatively affected by the elevated metal levels and was closely correlated with heavy metal stress. Enzyme activity was greatly depressed by conditions in the heavy metal-contaminated sites. Good correlation was observed between enzyme activity and the distance from the smelter. Elevated metal loadings resulted in changes in the activity of the soil microbe, as indicated by changes in their metabolic profiles from correlation analysis. Significant decrease of soil phosphatase activities was found in the soils 200 m away from the smelter. Polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) analysis demonstrated that heavy metals pollution had a significant impact on bacterial and actinomycetic community structure. There were negative correlations between soil microbial biomass, phosphatase activity, and NH4NO3 extractable heavy metals. The soil microorganism activity and community composition could be predicted significantly using the availability of Cu and Zn. By combining different monitoring approaches from different viewpoints, the set of methods applied in this study were sensitive to site differences and contributed to a better understanding of heavy metals effects on the structure, size and activity of microbial communities in soils. The data presented demonstrate the role of heavy metals pollution in understanding the heavy metal toxicity to soil microorganism near a copper smelter in China.

AbstractPhytoremediation has been used as an emerging technology for remediation of soil contamination with polycyclic aromatic hydrocarbons (PAHs), ubiquitous persistent environmental pollutants derived from natural and anthropogenic processes, in the last decade. In this study, a pot experiment was conducted to investigate the potential of phytoremediation of pyrene from spiked soils planted with white clover (Trifolium repens) in the greenhouse with a series of pyrene concentrations ranging from 4.22 to 365.38 mg kg−1. The results showed that growth of white clover on pyrenecontaminated soils was not affected. The removal of pyrene from the spiked soils planted with white clover was obviously higher than that from the unplanted soils. At the end of the experiment (60 d), the average removal ratio of pyrene in the spiked soils with white clover was 77%, which was 31% and 57% higher than those of the controls with or without micobes, respectively. Both roots and shoots of white clover took up pyrene from the spiked soils and pyrene uptake increased with the soil pyrene concentration. However, the plant-enhanced dissipation of soil pyrene may be the result of plant-promoted microbial degradation and direct uptake and accumulation of pyrene by white clover were only a small part of the pyrene dissipation. Bioconcentration factors of pyrene (BCFs, ratio of pyrene, on a dry weight basis, in the plant to that in the soil) tended to decrease with increase in the residual soil pyrene concentration. Therefore, removal of pyrene in the contaminated soils was feasible using white clove.

A field experiment located in Taihu Lake Basin of China was conducted, by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen (N) export in a typical rice field through “zero-drainage water management” combined with sound irrigation, rainfall forecasting and field drying. N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations, and subsequently tended to return to the background level. Before the first field drying, total particulate nitrogen (TPN) was the predominant N form in floodwater of plots with no N input, dissolved inorganic nitrogen (DIN) on plots that received urea only, and dissolved organic nitrogen (DON) on plots treated with the mixture of urea and manure. Thereafter TPN became the major form. No N export was found from the rice field, but total nitrogen (TN) of 15.8 kg/hm2 was remained, mainly due to soil N sorption. The results recommended the zero-drainage water management for full-scale areas for minimizing N export.

The objective in the first phase of this study was to screen four plant species (alfalfa, ryegrass, tall fescue and rice) for phytoremediation of aged polychlorinated biphenyl (PCB)-contaminated soil from an electronic and electric waste (e-waste) recycling site. Glucose, biphenyl and three surfactants (TritonX-100, randomly methylated-β-cyclodextrins and β-cyclodextrin) were used to enhance the phytoremediation process. During the second phase, the focus was rhizosphere characteristics and plant uptake to investigate the mechanism of PCB removal from soil. In the first phase, all the tested plant species showed a significantly greater PCB removal percentage compared to the unplanted controls, while different amendments showed no significant difference. The most effective plant (ryegrass) combined with β-cyclodextrin was selected for further studies. During the rhizosphere characteristics and plant uptake study, the highest PCB removal percentage (38.1%) was observed in the ryegrass planted soil when β-cyclodextrin was amended at 1.0% (w/w). The presence of plants significantly increased the biological activity (microbial counts and enzyme activity) of both β-cyclodextrin amended and non-amended soils. Higher levels of PCB removal were closely related to greater microbial counts and soil enzyme activities by correlation analysis. After 120 days of plant growth, ryegrass accumulated 708.7–820.1 ng PCBs/g in the root and 71.7–110.8 ng PCBs/g in the shoot, resulting in about 0.08% PCBs removal from soil. It was concluded that high PCB degradation was due to the increased PCB bioavailability as well as biostimulation of microbial communities after plantation and β-cyclodextrin addition. Furthermore, results suggested that PCB removal was mainly contributed by microbial degradation rather than plant uptake or abiotic dissipation.