Mercury capture into biogenic amorphous selenium nanospheres produced by mercury resistant Shewanella putrefaciens 200

Shewanella putrefaciens 200, resistant to high concentration of Hg(II), was selected for co-removal of mercury and selenium from aqueous medium. Biogenic Hg(0) reduced from Hg(II) by S. putrefaciens 200 was captured into extracellular amorphous selenium nanospheres, resulting in the formation of stable HgSe nanoparticles. This bacterial reduction could be a new strategy for mercury removal from aquatic environments without secondary pollution of mercury methylation or Hg(0) volatilization.     

纳米材料的水生态毒理学研究进展

纳米材料特殊的理化特性,使它们被广泛地应用到各个生活领域中,但纳米材料给人们生活带来巨大改变的同时,其对水环境引起的负面效应也引起了人们广泛的关注.纳米材料可通过多种途径进入水体,对水生生物产生毒理效应,其生态学影响不可忽视.目前,还很缺乏对纳米材料的水生态毒理学研究,众多不确定的生态安全性问题还有待更深入的研究.总结了国内外现有的相关研究,简要综述了纳米材料的水环境行为、水生态毒理学研究现状,分析了该研究领域的未来需要.     

Consumption of biogenic nitric oxide in hydrated soil

An experimental study was conducted in order to determine the relationship of nitric oxide (NO) consumption to water-filled pore space in soil. A test system that included the capability to blend gases, test soil samples, and analyze off-gases was used to conduct the study. The experimental set consisted of three replicates at five different levels of soil water content and three different levels of soil nitrogen in a sandy loam soil: unamended soil, soil fertilized at 56.2 kg N per ha (50 lb N acre(-1)), and soil fertilized at 112.3 kg N per ha (100 lb N acre(-1)). The average NO consumption rates were 7.1x10(-13) g-NO cm(-3) soil, 3.5x10(-11) g-NO cm(-3) soil, and 1.5x10(-10) g-NO cm(-3) soil, respectively.     

An overview of nanomaterials applied for removing dyes from wastewater

Organic dyes are one of the most commonly discharged pollutants in wastewaters; however, many conventional treatment methods cannot treat them effectively. Over the past few decades, we have witnessed rapid development of nanotechnologies, which offered new opportunities for developing innovative methods to treat dye-contaminated wastewater with low price and high efficiency. The large surface area, modified surface properties, unique electron conduction properties, etc. offer nanomaterials with excellent performances in dye-contaminated wastewater treatment. For examples, the agar-modified monometallic/bimetallic nanoparticles have the maximum methylene blue adsorption capacity of 875.0 mg/g, which are several times higher than conventional adsorbents. Among various nanomaterials, the carbonaceous nanomaterials, nano-sized TiO₂, and graphitic carbon nitride (g-C₃N₄) are considered as the most promising nanomaterials for removing dyes from water phase. However, some challenges, such as high cost and poor separation performance, still limit their engineering application. This article reviewed the recent advances in the nanomaterials used for dye removal via adsorption, photocatalytic degradation, and biological treatment. The modification methods for improving the effectiveness of nanomaterials are highlighted. Finally, the current knowledge gaps of developing nanomaterials on the environmental application were discussed, and the possible further research direction is proposed.     

Desorption of polycyclic aromatic hydrocarbons from carbon nanomaterials in water

Desorption behavior of pyrene, phenanthrene and naphthalene from fullerene, single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) was examined. Available adsorption space of carbon nanotubes (CNTs) was found to be the cylindrical external surface, neither the inner cavities nor inter-wall spaces due to impurities in the CNTs and restricted spaces (0.335nm) of the MWCNTs, respectively. Desorption hysteresis was observed for fullerene but not for CNTs. Deformation-rearrangement was proposed to explain the hysteresis of polycyclic aromatic hydrocarbons (PAHs) for fullerene, due to the formation of closed interstitial spaces in spherical fullerene aggregates. However, long, cylindrical carbon nanotubes could not form such closed interstitial spaces in their aggregates due to their length, thus showing no significant hysteresis. High adsorption capacity and reversible adsorption of PAHs on CNTs imply the potential release of PAHs if PAH-adsorbed CNTs are inhaled by animals and humans, leading to a high environmental and public health risk.     

The effects of nanomaterials on microstructures of sludge ash cement paste

To broaden the beneficial reuse of sewage sludge, small amounts of nanomaterial were considered as additives to evaluate influences of nanomaterials on microstructures of sludge cement paste. Paste specimens were manufactured using different mix designs and cured for various ages. Tests such as scanning electron microscope, X-ray diffraction, transmission electron microscope, and mercury intrusion porosimetry were then performed. Results obtained indicated that the quantities of crystallization in hydrates rose with the increased amounts of nanomaterial added. Moreover, nanomaterial additives could make crystallizations denser, pore sizes smaller, and the number of pores decreased. Consequently, the strength of sludge cement paste became better as more amounts of nanomaterial were added.     

Elevated biogenic sulphur dioxide concentrations over the North Atlantic

Elevated biogenic SO₂ from the oxidation of dimethylsulphide (DMS) in the marine atmosphere was measured over the North Atlantic Ocean in spring and summer 2003. Stable isotope apportionment was used to distinguish between anthropogenic and biogenic SO₂ in the marine atmosphere south of Greenland. Atmospheric DMS measurements were within range of previous studies. Biogenic SO₂ concentrations were as high as 82 nmol m^?3 (spring geometric mean: 4 nmol m^?3, σ = 17; summer geometric mean 7 nmol m^?3, σ = 19) and are the highest reported values for marine biogenic SO₂ in the literature. Elevated biogenic SO₂ was found in air masses influenced by anthropogenic pollutants during the summer. This indicates that anthropogenic pollutants may affect the fate of oceanic emissions of sulphur compounds in the atmosphere favoring the formation of cloud condensation nuclei.     

Corbicula fluminea gene expression modulated by CeO2 nanomaterials and salinity

Environmental Science and Pollution Research - Cerium dioxide nanomaterials (CeO2 NMs) are used in different fields and incorporated in daily products. Several studies highlighted their effects on...     

Characterizing kinetics of transport and transformation of selenium in water-sediment microcosm free from selenium contamination using a simple mathematical model

This study developed a seven-compartment model for predicting the fate of selenium (Se) in an aquatic environment containing a water-sediment boundary. Speciation of Se in water-sediment microcosms under microaerobic conditions was measured to evaluate first-order kinetics of Se transportation and transformation. The microcosm consisted of a 10-ml solution containing 1mM soluble Se as selenate (Se6+) or selenite (Se4+) and 8 g wet sediment that was free from Se contamination, sampled from the Senri, Yamato, or Yodo Rivers in Osaka, Japan. Stepwise reaction coefficients describing transportation and transformation were determined using an inverse method on this model which includes: selenate (Se(W)6+) and selenite (Se(W)4+) in ponded water; selenate (Se(S)6+) and selenite (Se(S)4+), elemental Se (Se0), organic Se (Se2-) in sediment; and gaseous Se (DMSe). During this 1-month experiment, soluble Se was transported from ponded water to the sediment and Se was transformed sequentially to other Se species through biochemical reactions. Experimental and kinetic analyses indicated quantitatively that the Yamato River microcosm, with its high organic matter content, had a high adsorption rate of soluble Se. The Yodo River microcosm had a low adsorption rate for Se6+ and a low Se reduction rate. The Senri River microcosm had an apparent high volatilization rate of DMSe. The model developed in this study is extremely useful for predicting fate of Se in aquatic environment in the field.     

Distribution and bioaccumulation of selenium in aquatic microcosms

Closed-system microcosms were used to study factors affecting the fate of selenium (Se) in aquatic systems. Distribution and bioaccumulation of Se varied among sediment types and Se species. A mixture of dissolved (75)Se species (selenate, selenite and selenomethionine) was sorbed more rapidly to fine-textured, highly organic pond sediments than to sandy riverine sediments. Sulfate did not affect the distribution and bioaccumulation of (75)Se over the range 80-180 mg SO(4) liter(-1). When each Se species was labeled separately, selenomethionine was lost from the water column more rapidly than selenate or selenite. Selenium lost from the water column accumulated primarily in sediments, but volatilization was also an important pathway for loss of Se added as selenomethionine. Loss rates of dissolved Se residues were more rapid than rates reported from mesocosm and field studies, suggesting that sediment: water interactions are more important in microcosms than in larger test systems. Daphnids accumulated highest concentrations of Se, followed by periphyton and macrophytes. Selenium added as selenomethionine was bioaccumulated preferentially compared to that added as selenite or selenate. Organoselenium compounds such as selenomethione may thus contribute disproportionately to Se bioaccumulation and toxicity in aquatic organisms.     

A biogenic volatile organic compound emission inventory for Hong Kong

Biogenic volatile organic compounds (BVOCs) in the atmosphere react to form ozone and secondary organic aerosols, which deteriorate air quality, affect human health, and indirectly influence global climate changes. The present study aims to provide a preliminary assessment of BVOC emissions in Hong Kong (HKSAR). Thriteen local tree species were measured for their isoprene emission potential. Tree distribution was estimated for country park areas based on field survey data. Plant emission data obtained from measurements and the literature, tree distribution estimation data, land use information, and meteorological data were combined to estimate annual BVOC emissions of 8.6×10⁹ g C for Hong Kong. Isoprene, monoterpenes, and other VOCs contributed about 30%, 40%, and 30% of the estimated total annual emissions, respectively. Although hundreds of plant species are found in Hong Kong country parks, the model results indicate that only 10 tree species contribute about 76% of total annual VOC emissions. Prominent seasonal and diurnal variations in emissions were also predicted by the model. The present study lays a solid foundation for future local research, and results can be applied for studying BVOC emissions in nearby southern China and Asian regions that share similar climate and plant distributions.     

Estimating Taiwan biogenic VOC emission: Leaf energy balance consideration

The goal of the present study is to provide a comprehensive model to estimate biogenic volatile organic compounds (BVOCs) in Taiwan. In addition to metrological data, the model consists of (1) 83 land-use patterns, (2) emission factors for various vegetations, (3) energy balance equation to account for leaf temperature, and (4) correction terms for photosynthetically active radiation. The model output includes 4 categories of 33 BVOCs [isoprene, methylbutenol (MBO), 14 species of monoterpenes and 17 other BVOCs]. The results of model verification based on several approaches include: (1) predicted isoprene emission flux correlates relatively good with the observed isoprene concentration (R² = 0.66); (2) correlation between leaf temperature and observed isoprene levels is better than that between ambient temperature and isoprene concentrations (R² = 0.63 vs. 0.58); (3) model-predicted isoprene fluxes match well with observed 3-day diurnal isoprene concentration variations; and (4) subsequent model-predicted O₃ concentrations with the BVOC input obtained in the present study match well than that with previous estimated BVOC data with the observed 6-day diurnal O₃ levels in 8 air quality monitoring stations.Based on the meteorological data in 2000, the total emission of BVOCs in Taiwan was simulated to be about 433,000 ton (33% of total VOCs) of which both isoprene and 14 species of monoterpenes account for about 34%, with 17 species of other BVOCs being 31% and <2% contribution from MBO. Total emissions of BVOCs are higher in lower and medium altitude (300–1000 m) mountain areas with an average of around 15–30 ton km⁻² y⁻¹. The implication of the other results is also discussed.     

Protein bound selenium in some marine organisms

Total selenium levels and the fraction of element associated with protein have been determined in several marine organisms by gas-liquid chromatography. A large fraction of selenium in all organisms was associated with protein.     

Structure elucidation of four possible biogenic organohalogens using isotope exchange mass spectrometry

The molecular structures of four unknown bioaccumulating halogenated compounds, C10H6N2Br3Cl3, C10H6N2Br4Cl2, C10H6N2Br5Cl, and C10H6N2Br6 were characterized using isotope exchange positive chemical ionization (IE-PCI) mass spectrometry (MS) and identified by comparison to synthesized standards. NH3 and ND3 were used as reagent gases for the IE-PCI-MS experiment. The shift in mass of the quasimolecular ion between the NH3 and ND3 PCI obtained spectra indicated the number of exchangeable hydrogens attached to the two nitrogen atoms in C10H6N2Br4Cl2, and thus the type of amines present (primary, secondary, or tertiary). 19 compounds (13 amines of varying degree of substitution; six containing no nitrogen) were used as reference compounds and controls in the experiment to validate the IE-PCI technique. The results of the IE-PCI-MS indicated the presence of two tertiary amine functional groups. The molecular structures of the four hexahalogenated compounds were then proposed to be 1,1'-dimethyl-3,3',4,-tribromo-4',5,5'-trichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole, and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole and subsequently synthesized. Comparison of retention times and electron capture negative ionization (ECNI) full scans on various gas chromatography (GC) columns between the synthesized bipyrroles and the corresponding unknown compounds in biota indicated that three of the unknown compounds--possible marine natural products--were the proposed halogenated dimethyl bipyrroles. The placement of the halogen atoms on the fourth compound, C10H6N2Br3Cl3 could not be unequivocally determined since the synthesized standard could not be fully characterized.     

Design scenario for the radioisotopic estimation of the biogenic component of airborne particles

An experimental design is described to estimate the fraction of secondary fine particle from the biogenic component of volatile organic compounds (VOCs) in the atmosphere using radiocarbon isotopic abundance ratios. The method distinguishes between "modern" carbon (C), and "old" C of primary and secondary origins based on three components, condensed-phase organic carbon (OC), semi-volatile particulate compounds (SVOCs), and VOCs. The method depends on interpretation of diurnal and seasonal variation in OC, SVOC, and VOC concentrations. Sampling employs a filter-denuder unit, which collects the three C components for isotopic analysis. The samples are collected repetitively for a daily sequence of the same hourly intervals covering diurnal periods with similar meteorological conditions. Collected C is thermally treated to separate OC from black carbon on filters and VOCs or SVOCs from adsorbents, with all four fractions individually oxidized to carbon dioxide to determine the radiocarbon content by accelerator mass spectrometry. Using C isotope abundance, the data are interpreted for fractions of primary modern C and secondary modern C as estimated from averaging diurnal and seasonal variations in the concentration data. As support for interpretation, samples of OC, SVOCs, and VOCs would be analyzed for speciation to identify source indicator species present.     

中国植物挥发性有机化合物排放估算研究进展

植物挥发性有机化合物(BVOCs)因其排放量大、化学活性高,对大气环境质量、气候变化以及碳循环等方面均影响很大。主要从中国BVOCs的来源、组成、合成和排放机制,不同树种BVOCs排放速率,不同尺度BVOCs排放量的估算等方面对国内外相关研究进行了评述,并展望了BVOCs排放估算在今后的发展,以期在大气污染防治角度对植物的合理选择和配置提供一定的参考依据。