Speciation Profiles Research Articles

Measuring the distribution of trace elements amongst dissolved colloidal species as a fingerprint for the contribution of tributaries to large boreal rivers

Organic and inorganic colloids play important roles governing the speciation, transport, and bioaccessibility of trace elements in aquatic systems. These carriers are especially important in the boreal zone, where rivers that contain high concentrations of iron and organic matter are prevalent. The distribution of trace elements amongst different colloidal species (or “speciation profile”) can therefore be useful as a fingerprint to detect different trace element sources and for tracking colloid transformations, with implications for bioaccessibility. Asymmetrical flow field-flow fractionation coupled to an inductively coupled plasma mass spectrometer was applied to detect the source of trace elements based on their speciation profile along a 125-km stretch of a large river in the Canadian boreal forest. Both the concentration and proportion of bound trace elements were increased by tributary inputs: bound As, Co, Fe, Mn, Pb, U, and Zn increased monotonically from upstream to downstream, increasingly resembling the speciation profile of tributaries. Principal component (PC) analysis also revealed tributary contributions of bound Cu, Ni, Th, V, and Y reflecting their higher concentrations in tributaries, and PC scores also increased monotonically from upstream–downstream. Monotonically decreasing concentrations of mainly ionic and small (i.e. <ca. 300 Da) As, Ba, Mo, and U species were also observed from upstream–downstream.

Cocrystal solubility-pH and drug solubilization capacity of sodium dodecyl sulfate – mass action model for data analysis and simulation to improve design of experiments

This review discusses the disposition of the anionic surfactant, sodium dodecyl sulfate (SDS; i.e., sodium lauryl sulfate), to solubilize sparingly-soluble drugs above the surfactant critical micelle concentration (CMC), as quantitated by the solubilization capacity (k). A compilation of 101 published SDS k values of mostly poorly-soluble drug molecules was used to develop a prediction model as a function of the drug’s intrinsic solubility, S0, and its calculated H-bond acceptor/donor potential. In almost all cases, the surfactant was found to solubilize the neutral form of the drug. Using the mass action model, the k values were converted to drug-micelle stoichiometric binding constants, Kn, corresponding to drug-micelle equilibria in drug-saturated solutions. An in-depth case study (data from published sources) considered the micellization reactions as a function of pH of a weak base, B, (pKa 3.58, S0 52 μg/mL), where at pH 1 the BH.SDS salt was predicted to precipitate both below and above the CMC. At low SDS concentrations, two drug salts were predicted to co-precipitate: BH.Cl and BH.SDS. Solubility products of both were determined from the analysis of the reported solubility-surfactant data. Above the CMC, in a rare example, the charged form of the drug (BH+) appeared to be strongly solubilized by the surfactant. The constant for that reaction was also determined. At pH 7, the reactions were simpler, as only the neutral form of the drug was solubilized, to a significantly lesser extent than at pH 1. Case studies also featured examples of solubilization of solids in the form of cocrystals. For many cocrystal systems studied in aqueous solution, the anticipated supersaturated state is not long-lasting, as the drug component precipitates to a thermodynamically stable form, thus lowering the amount of the active ingredient available for intestinal absorption. Use of surfactant can prevent this. A recently-described method for predicting the solubility product of cocrystals (coupled with predicted k values described here) allowed for simulations of solubility-pH speciation profiles of cocrystal systems in the presence of SDS. Well in advance of any actual measurements, these simulations can be used to probe conditions favorable to the design of cocrystal experiments where SDS stabilizes cocrystal suspensions against drug precipitation over a predicted range of pH values.

Thermodynamic modelling using e-UNIQUAC model for CO2 absorption by novel amine solutions: 1-Dimethylamino- 2-propanol (1DMA2P), 3-dimethylamino-1-propanol (3DMA1P) and 4-diethylamino-2-butanol (DEAB)

The proper selection of thermodynamic models is an important step in the design and simulation of CO2 removal processes using amine solutions. In this study, we aim to study the thermodynamic behaviour of the CO2 removal process by employing the extended-universal quasichemical (e-UNIQUAC) model for three novel amine systems, namely CO2+1DMA2P + H2O, CO2+3DMA1P + H2O, and CO2+DEAB + H2O. The thermodynamic behaviour was studied in terms of the CO2 loading of amines, the ion speciation profiles, the isothermal pressure-composition (Pxy) profiles, and the pH of the amine solutions. Adjustable parameters of the model include binary interaction parameters, and the volume and surface area parameters of the amine and protonated amine were determined using different objective functions based on the experimental data available in the literature. The ion and molecular speciation profiles are obtained and compared with nuclear magnetic resonance (NMR) data for CO2+1DMA2P + H2O and CO2+DEAB + H2O systems. The model predicted the experimental data with average absolute relative deviations (AARDs) of 8.06%, 13.39% and 16.50% for CO2 loading values of DEAB, 1DMA2P, and 3DMA1P, respectively. In addition, the results of Pxy profiles at different temperatures show that the azeotrope does not form in the 3DMA1P + H2O system. The adjustable parameters and predicted data of the applied e-UNIQUAC model may contribute to the rate-based simulation of CO2 absorption processes using novel amine systems.

Source-specific speciation profiles of PM2.5 for heavy metals and their anthropogenic emissions in China

Heavy metals are concerned for its adverse effect on human health and long term burden on biogeochemical cycling in the ecosystem. In this study, a provincial-level emission inventory of 13 kinds of heavy metals including V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Sn, Sb, Ba and Pb from 10 anthropogenic sources was developed for China, based on the 2015 national emission inventory of primary particulate matters and source category-specific speciation profiles collected from 50 previous studies measured in China. Uncertainties associated with the speciation profiles were also evaluated. Our results suggested that total emissions of the 13 types of heavy metals in China are estimated at about 58000 ton for the year 2015. The iron production is the dominant source of heavy metal, contributing 42% of total emissions of heavy metals. The emissions of heavy metals vary significantly at regional scale, with largest amount of emissions concentrated in northern and eastern China. Particular, high emissions of Cr, Co, Ni, As and Sb (contributing 8%–18% of the national emissions) are found in Shandong where has large capacity of industrial production. Uncertainty analysis suggested that the implementation of province-specific source profiles in this study significantly reduced the emission uncertainties from (−89%, 289%) to (−99%, 91%), particularly for coal combustion. However, source profiles for industry sectors such as non-metallic mineral manufacturing are quite limited, resulting in a relative high uncertainty. The high-resolution emission inventories of heavy metals are essential not only for their distribution, deposition and transport studies, but for the design of policies to redress critical atmospheric environmental hazards at local and regional scales. Detailed investigation on source-specific profile in China are still needed to achieve more accurate estimations of heavy metals in the future.

A unique arsenic speciation profile in Elaphomyces spp. (\u201cdeer truffles\u201d)\u2014trimethylarsine oxide and methylarsonous acid as significant arsenic compounds

Arsenic and its species were investigated for the first time in nine collections of Elaphomyces spp. (“deer truffles”) from the Czech Republic with inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography coupled to ICPMS. The total arsenic concentrations ranged from 12 to 42 mg kg−1 dry mass in samples of E. asperulus and from 120 to 660 mg kg−1 dry mass in E. granulatus and E. muricatus. These concentrations are remarkably high for terrestrial organisms and demonstrate the arsenic-accumulating ability of these fungi. The dominating arsenic species in all samples was methylarsonic acid which accounted for more than 30% of the extractable arsenic. Arsenobetaine, dimethylarsinic acid, and inorganic arsenic were present as well, but only at trace concentrations. Surprisingly, we found high amounts of trimethylarsine oxide in all samples (0.32–28% of the extractable arsenic). Even more remarkable was that all but two samples contained significant amounts of the highly toxic trivalent arsenic compound methylarsonous acid (0.08–0.73% of the extractable arsenic). This is the first report of the occurrence of trimethylarsine oxide and methylarsonous acid at significant concentrations in a terrestrial organism. Our findings point out that there is still a lot to be understood about the biotransformation pathways of arsenic in the terrestrial environment.Graphical abstractTrimethylarsine oxide and methylarsonous acid in “deer truffles”

Volatile Organic Compounds Emission from Chinese Wood Furniture Coating Industry: Activity-based Emission Factor, Speciation Profiles, and Provincial Emission Inventory

Volatile organic compounds (VOCs) have been identified as the most crucial precursors of tropospheric photochemical O3 formation and secondary organic aerosols. In this study, field measurement was conducted to develop VOCs emission factors and source profiles of the wood furniture coating industry in China. An activity-based database was established, involving coat consumption-based, coating area-based, furniture production-based, and output value-based VOCs emission factors. Combining the results of field tests and literature surveys, emission factors were calculated by enterprise scale, coating type, spraying technology, and emission control device. The uncertainties were quantified by using Monte Carlo simulations. VOCs emission factors were estimated: 0.22 (0.10–0.34, 95% CI) kg kg–1 for coat consumption-based; 21.97 (10.10–29.38) g m–2 for coating area–based; 0.69 (0.34–1.00) kg piece–1 for furniture production-based; and 6.95 (3.42–10.21) kg 10–4 yuan for output value–based calculation, respectively. Aromatics and oxygenated VOCs (OVOCs) were predominant species of solvent borne paint emission, with the proportion of 71.1% and 22.9% of totals, respectively. VOCs emissions from the wood furniture coating industry were estimated at 179.76 × 103 (88.58 × 103–260.52 × 103, 95% CI) t in 2016. Due to the huge production output and intensive distribution of enterprises, VOCs emissions mainly concentrated in Guangdong, Zhejiang, Shandong, Fujian, Jiangxi, and Sichuan province, with the combined contribution of 43.8% of the national totals.

Speciation and antifungal susceptibility profiles of Candida isolates from vaginitis patients attending STD Clinic at a Tertiary Care Hospital

Back ground: Candidiasis is the most common vaginal infection affecting approximately 50–72% of women. Rapid identification of yeast isolates to species level is essential to optimize antifungal treatment. Aim: To determine the prevalence of various Candida species among vaginal candidiasis and to determine the antifungal susceptibility pattern of the isolates. Materials and Methods: A total of 471 women who were clinically diagnosed to have vaginal candidiasis were included in the study. Out of 471 vaginitis patients, 91 were positive for Candida species. All the isolates were speciated comprising five species – C. albicans 42 (46.1%), C. krusei 5 (5.5%), C. glabrata 40 (43.9%), C. tropicalis 3 (3.3%), and C. gullermondi 1 (1.1%). Antifungal susceptibility testing result of all Candida isolates are 100% susceptible to amphotericin B, nystatin, flucytosine, econazole, ketoconazole, miconazole, fluconazole. C. krusei isolates are showing 100% resistance to fluconazole. Discussion: In the present study, C. albicans is most common species 46.1% followed by C. glabarata. C. albicans adhere to vaginal, epithelial cells in significantly higher number than other Candida species. This could explain relative higher frequency of C. albicans in vaginal candidiasis. Conclusion: Presumptive identification followed by confirmation of Candida species helps to initiate early appropriate antifungal treatment, thereby reducing the morbidity and mortality.

Amine-based post-combustion CO2 capture mediated by metal ions: Advancement of CO2 desorption using copper ions

For the large-scale implementation of amine-based post-combustion CO2 capture, the energy consumption associated with the absorbent regeneration remains the most critical challenge. Despite efforts to reduce regeneration duty, such as using new amine formulations and modifying process configurations, an advanced method of overcoming this technical barrier is still required. Here, we introduce a novel approach to decreasing the heat requirement of absorbent regeneration by introducing metal ions catalyst into aqueous amine solution. Our approach uses the dual ability of amine in aqueous solution to both react with CO2 and complex with transition metal ions to reduce the heat of CO2 desorption via metal–amine complexation. Based on benchmarking monoethanolamine (MEA) absorbent and copper (Cu) ions, we developed a model that describes the process chemistry of Cu(II)–MEA–CO2–H2O to understand the speciation profiles under various conditions, particularly for Cu–MEA complexes. We conducted the comprehensive experiments to investigate the influence of Cu(II) addition on the performance of MEA-based CO2 capture process, including the CO2 absorption/desorption capacity, CO2 absorption/desorption rate, CO2 absorption temperature increase and heat of CO2 desorption. The results showed that adding Cu(II) to MEA solution significantly improved the CO2 capture performance, i.e. it mitigated the temperature increase during CO2 absorption, enhanced the CO2 desorption rate, increased the solvent’s cyclic CO2 capacity due to deep CO2 stripping. More importantly, the heat of CO2 desorption was reduced by 13.2–24.0% depending on the copper ion concentration. Our results indicate that metal–amine complexes play an important role in advancing the amine-based CO2 capture process and have potential application to industrial practice.

Improve regional distribution and source apportionment of PM2.5 trace elements in China using inventory-observation constrained emission factors

Contributions to 15 trace elements in airborne particulate matter with aerodynamic diameters <2.5μm (PM2.5) in China from five major source sectors (industrial sources, residential sources, transportation, power generation and windblown dust) were determined using a source-oriented Community Multiscale Air Quality (CMAQ) model. Using emission factors in the composite speciation profiles from US EPA's SPECIATE database for the five sources leads to relatively poor model performance at an urban site in Beijing. Improved predictions of the trace elements are obtained by using adjusted emission factors derived from a robust multilinear regression of the CMAQ predicted primary source contributions and observation at the urban site. Good correlations between predictions and observations are obtained for most elements studied with R>0.5, except for crustal elements Al, Si and Ca, particularly in spring. Predicted annual and seasonal average concentrations of Mn, Fe, Zn and Pb in Nanjing and Chengdu are also consistently improved using the adjusted emission factors. Annual average concentration of Fe is as high as 2.0μgm−3 with large contributions from power generation and transportation. Annual average concentration of Pb reaches 300–500ngm−3 in vast areas, mainly from residential activities, transportation and power generation. The impact of high concentrations of Fe on secondary sulfate formation and Pb on human health should be evaluated carefully in future studies.

Source apportionment of secondary organic aerosol in China using a regional source-oriented chemical transport model and two emission inventories.

A Community Multiscale Air Quality (CMAQ) model with source-oriented lumped SAPRC-11 (S11L) photochemical mechanism and secondary organic aerosol (SOA) module was applied to determine the contributions of anthropogenic and biogenic sources to SOA concentrations in China. A one-year simulation of 2013 using the Multi-resolution Emission Inventory for China (MEIC) shows that summer SOA are generally higher (10-15μgm-3) due to large contributions of biogenic (country average 60%) and industrial sources (17%). In winter, SOA formation was mostly due to anthropogenic emissions from industries (40%) and residential sources (38%). Emissions from other countries in southeast China account for approximately 14% of the SOA in both summer and winter, and 46% in spring due to elevated open biomass burning in southeast Asia. The Regional Emission inventory in ASia v2.1 (REAS2) was applied in this study for January and August 2013. Two sets of simulations with the REAS2 inventory were conducted using two different methods to speciate total non-methane carbon into model species. One approach uses total non-methane hydrocarbon (NMHC) emissions and representative speciation profiles from the SPECIATE database. The other approach retains the REAS2 speciated species that can be directly mapped to S11L model species and uses source specific splitting factors to map other REAS2 lumped NMHC species. Biogenic emissions are still the most significant contributor in summer based on these two sets of simulations. However, contributions from the transportation sector to SOA in January are predicted to be much more important based on the two REAS2 emission inventories (∼30-40% vs. ∼5% by MEIC), and contributions from residential sources according to REAS2 was much lower (∼21-24% vs. ∼42%). These discrepancies in source contributions to SOA need to be further investigated as the country seeks for optimal emission control strategies to fight severe air pollution.

A comprehensive experimental and kinetic modeling study of n-propylbenzene combustion

This work presents a comprehensive experimental and kinetic modeling study on the combustion of n-propylbenzene. Flow reactor pyrolysis of n-propylbenzene at 0.04, 0.2 and 1 atm and laminar premixed flames of n-propylbenzene at 0.04 atm with equivalence ratios of 0.75 and 1.00 were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry. Jet stirred reactor (JSR) oxidation of n-propylbenzene at 10 atm with equivalence ratios of 0.5, 1.0, 1.5 and 2.0 was investigated with gas chromatography. A detailed kinetic model for n-propylbenzene combustion with 340 species and 2069 reactions was developed and validated against the data measured in this work. Model analyses such as rate of production analysis and sensitivity analysis were also performed to reveal the key pathways in the consumption of fuel and formation of polycyclic aromatic hydrocarbons (PAHs). The analysis results demonstrate that the benzylic CC bond dissociation reaction is crucial for the decomposition of n-propylbenzene in the pyrolysis and rich flame. Low temperature oxidation reactions play important roles in the high pressure JSR oxidation of n-propylbenzene. In addition, the formation pathways of PAHs are strongly related to the fuel structure, especially for the formation of bicyclic PAHs such as indene and naphthalene. Furthermore, the present model was also validated against previous experimental data of n-propylbenzene combustion under a wide range of conditions, including ignition delay times, laminar flame speeds, extinction strain rates, speciation profiles in atmospheric pressure JSR oxidation, flow reactor oxidation and high pressure shock tube pyrolysis and oxidation.

Stabilization of gas-phase uranyl complexes enables rapid speciation using electrospray ionization and ion mobility-mass spectrometry

Significant challenges exist when characterizing f-element complexes in solution using traditional approaches such as electrochemical and spectroscopic techniques as they do not always capture information for lower abundance species. However, provided a metal-complex with sufficient stability, soft ionization techniques such as electrospray offer a means to quantify and probe the characteristics of such systems using mass spectrometry. Unfortunately, the gas-phase species observed in ESI-MS systems do not always reflect the solution phase distributions due to the inherent electrochemical mechanism of the electrospray process, ion transfer from ambient to low pressures conditions, and other factors that are related to droplet evaporation. Even for simple systems (e.g. hydrated cations), it is not always clear whether the distribution observed reflects the solution phase populations or whether it is simply a result of the ionization process. This complexity is further compounded in mixed solvent systems and when multiply charged species are present. Despite these challenges, the benefits of mass spectrometry with respect to speed, sensitivity, and the ability to resolve isotopes continue to drive efforts to develop techniques for the speciation of metal complexes. Using an electrospray ionization atmospheric pressure ion mobility mass spectrometer (ESI-apIMS-MS), we demonstrate an approach to stabilize simple uranyl complexes during the ionization process and mobility separation to aid speciation and isotope profile analysis. Specifically, we outline and demonstrate the capacity of ESI-apIMS-MS methods to measure mobilities of different uranyl species, in simple mixtures, by promoting stable gas phase conformations with the addition of sulfoxides (i.e. dimethyl sulfoxide (DMSO), dibutyl sulfoxide (DBSO), and methyl phenyl sulfoxide (MPSO)). Addition of these sulfoxides, as observed in the mass spectrum and mobility domain, produce stable gas-phase conformations that enable the observation of the counter anion pair while minimizing the range of ligand exchange events as the ionized complex enters the gas-phase. Other enhancements include improved data acquisition times by applying multiplexing approaches to the IMS Bradbury-Nielsen (BN) gate to realize increased ion transmission and improve ion statistics measured at the m/z detector. Analyte identification using this approach is based on a multitude of combined measured gas-phase ion metrics, which include mass measurements, isotope profiling, and experimentally determined reduced mobilities measured at the low-field limit (<2 E/N). Though geared initially towards uranyl complexes, this approach may find application in fields where both chemical speciation and isotopic profiles provide diagnostic information for a given metal.

Improved provincial emission inventory and speciation profiles of anthropogenic non-methane volatile organic compounds: a case study for Jiangsu, China

Abstract. Non-methane volatile organic compounds (NMVOCs) are the key precursors of ozone (O3) and secondary organic aerosol (SOA) formation. Accurate estimation of their emissions plays a crucial role in air quality simulation and policy making. We developed a high-resolution anthropogenic NMVOC emission inventory for Jiangsu in eastern China from 2005 to 2014, based on detailed information of individual local sources and field measurements of source profiles of the chemical industry. A total of 56 NMVOCs samples were collected in nine chemical plants and were then analyzed with a gas chromatography – mass spectrometry system (GC-MS). Source profiles of stack emissions from synthetic rubber, acetate fiber, polyether, vinyl acetate and ethylene production, and those of fugitive emissions from ethylene, butanol and octanol, propylene epoxide, polyethylene and glycol production were obtained. Various manufacturing technologies and raw materials led to discrepancies in source profiles between our domestic field tests and foreign results for synthetic rubber and ethylene production. The provincial NMVOC emissions were calculated to increase from 1774 Gg in 2005 to 2507 Gg in 2014, and relatively large emission densities were found in cities along the Yangtze River with developed economies and industries. The estimates were larger than those from most other available inventories, due mainly to the complete inclusion of emission sources and to the elevated activity levels from plant-by-plant investigation in this work. Industrial processes and solvent use were the largest contributing sectors, and their emissions were estimated to increase, respectively, from 461 to 958 and from 38 to 966 Gg. Alkanes, aromatics and oxygenated VOCs (OVOCs) were the most important species, accounting for 25.9–29.9, 20.8–23.2 and 18.2–21.0 % to annual total emissions, respectively. Quantified with a Monte Carlo simulation, the uncertainties of annual NMVOC emissions vary slightly through the years, and the result for 2014 was −41 to +93 %, expressed as 95 % confidence intervals (CI). Reduced uncertainty was achieved compared to previous national and regional inventories, attributed partly to the detailed classification of emission sources and to the use of information at plant level in this work. Discrepancies in emission estimation were explored for the chemical and refinery sectors with various data sources and methods. Compared with the Multi-resolution Emission Inventory for China (MEIC), the spatial distribution of emissions in this work were more influenced by the locations of large point sources, and smaller emissions were found in urban area for developed cities in southern Jiangsu. In addition, discrepancies were found between this work and MEIC in the speciation of NMVOC emissions under the atmospheric chemistry mechanisms CB05 and SAPRC99. The difference in species OLE1 resulted mainly from the updated source profile of building paint use and the differences in other species from the varied sector contributions to emissions in the two inventories. The Community Multi-scale Air Quality (CMAQ) model simulation was applied to evaluate the two inventories, and better performance (indicated by daily 1 h maximum O3 concentrations in Nanjing) were found for January, April and October 2012 when the provincial inventory was used.

Speciation of anthropogenic emissions of non-methane volatile organic compounds: a global gridded data set for 1970–2012

Abstract. Non-methane volatile organic compounds (NMVOCs) include a large number of chemical species which differ significantly in their chemical characteristics and thus in their impacts on ozone and secondary organic aerosol formation. It is important that chemical transport models (CTMs) simulate the chemical transformation of the different NMVOC species in the troposphere consistently. In most emission inventories, however, only total NMVOC emissions are reported, which need to be decomposed into classes to fit the requirements of CTMs. For instance, the Emissions Database for Global Atmospheric Research (EDGAR) provides spatially resolved global anthropogenic emissions of total NMVOCs. In this study the EDGAR NMVOC inventory was revised and extended in time and in sectors. Moreover the new version of NMVOC emission data in the EDGAR database were disaggregated on a detailed sector resolution to individual species or species groups, thus enhancing the usability of the NMVOC emission data by the modelling community. Region- and source-specific speciation profiles of NMVOC species or species groups are compiled and mapped to EDGAR processes (detailed resolution of sectors), with corresponding quality codes specifying the quality of the mapping. Individual NMVOC species in different profiles are aggregated to 25 species groups, in line with the common classification of the Global Emissions Initiative (GEIA). Global annual grid maps with a resolution of 0.1° × 0.1° for the period 1970–2012 are produced by sector and species. Furthermore, trends in NMVOC composition are analysed, taking road transport and residential sources in Germany and the United Kingdom (UK) as examples.

Mercury flows in large-scale gold production and implications for Hg pollution control

Large-scale gold production (LSGP) is one of the five convention-related atmospheric mercury (Hg) emission sources in the Minamata Convention on Mercury. However, field experiments on Hg flows of the whole process of LSGP are limited. To identify the atmospheric Hg emission points and understand Hg emission characteristics of LSGP, Hg flows in two gold smelters were studied. Overall atmospheric Hg emissions accounted for 10%–17% of total Hg outputs and the Hg emission factors for all processes were 7.6–9.6kg/ton. There were three dominant atmospheric Hg emission points in the studied gold smelters, including the exhaust gas of the roasting process, exhaust gas from the environmental fog collection stack and exhaust gas from the converter of the refining process. Atmospheric Hg emissions from the roasting process only accounted for 16%–29% of total emissions and the rest were emitted from the refining process. The overall Hg speciation profile (gaseous elemental Hg/gaseous oxidized Hg/particulate-bound Hg) for LSGP was 34.1/57.1/8.8. The dominant Hg output byproducts included waste acid, sulfuric acid and cyanide leaching residue. Total Hg outputs from these three byproducts were 80% in smelter A and 84% in smelter B. Our study indicated that previous atmospheric Hg emissions from large-scale gold production might have been overestimated. Hg emission control in LSGP is not especially urgent in China compared to other significant emission sources (e.g., cement plants). Instead, LSGP is a potential Hg release source due to the high Hg output proportions to acid and sludge.

Complete transformation of ZnO and CuO nanoparticles in culture medium and lymphocyte cells during toxicity testing

Here, we present evidence on complete transformation of ZnO and CuO nanoparticles, which are among the most heavily studied metal oxide particles, during 24 h in vitro toxicological testing with human T-lymphocytes. Synchrotron radiation-based X-ray absorption near edge structure (XANES) spectroscopy results revealed that Zn speciation profiles of 30 nm and 80 nm ZnO nanoparticles, and ZnSO4- exposed cells were almost identical with the prevailing species being Zn-cysteine. This suggests that ZnO nanoparticles are rapidly transformed during a standard in vitro toxicological assay, and are sequestered intracellularly, analogously to soluble Zn. Complete transformation of ZnO in the test conditions was further supported by almost identical Zn spectra in medium to which ZnO nanoparticles or ZnSO4 was added. Likewise, Cu XANES spectra for CuO and CuSO4-exposed cells and cell culture media were similar. These results together with our observation on similar toxicological profiles of ZnO and soluble Zn, and CuO and soluble Cu, underline the importance of dissolution and subsequent transformation of ZnO and CuO nanoparticles during toxicological testing and provide evidence that the nano-specific effect of ZnO and CuO nanoparticles is negligible in this system. We strongly suggest to account for this aspect when interpreting the toxicological results of ZnO and CuO nanoparticles.

Selenium speciation profiles in biofortified sangiovese wine.

Biofortification is an agronomic-based strategy, utilized by farmers, to produce selenium (Se)-enriched food products that may help reduce dietary deficiencies of Se occurring throughout susceptible regions of the world. The foliar exposure route application ensures a high efficiency of Se assimilation by the plant since it does not depend on root-to-shoot translocation. In this study we treated grapevines of Sangiovese variety in the pre-flowering period with sodium selenate (100mg Se L-1). Se content was measured in leaves, fruit at harvest time and in wine respectively in treated and not treated samples with ICP-MS. At harvest, a higher amount of Se in the treated leaves compared to untreated ones was found, 16.0±3.1mgkg-1 dry weight (dw) against 0.17±0.006mgkg-1 dw in the untreated ones. The treated grapes had a content of Se of 0.800±0.08mgkg-1 dw, while that untreated one 0.065±0.025mgkg-1 dw. Immediately after the malolactic fermentation, the wine obtained from treated and untreated vines had a Se content of 0.620±0.09mg Se L-1 and 0.024±0.010mg Se L-1 respectively. In our case the percentage of inorganic Se is 26% of the total Se in the untreated wine, while in Se enriched wine this percentage increase to 47.5% of the total Se. The Se(VI) was the inorganic chemical form more present in enriched wine, probably due to foliar application with selenate. Distributions of Se species suggested being careful to the choice of the enrichment solutions to promote a balanced distribution of different chemical forms, perhaps favouring the accumulation of organic forms.

Estimating population exposure to ambient polycyclic aromatic hydrocarbon in the United States – Part I: Model development and evaluation

PAHs (polycyclic aromatic hydrocarbons) in the environment are of significant concern due to their negative impact on human health. PAH measurements at the air toxics monitoring network stations alone are not sufficient to provide a complete picture of ambient PAH levels or to allow accurate assessment of public exposure in the United States. In this study, speciation profiles for PAHs were prepared using data assembled from existing emission profile data bases, and the Sparse Matrix Operator Kernel Emissions (SMOKE) model was used to generate the gridded national emissions of 16 priority PAHs in the US. The estimated emissions were applied to simulate ambient concentration of PAHs for January, April, July and October 2011, using a modified Community Multiscale Air Quality (CMAQ) model (v5.0.1) that treats the gas and particle phase partitioning of PAHs and their reactions in the gas phase and on particle surface. Predicted daily PAH concentrations at 61 air toxics monitoring sites generally agreed with observations, and averaging the predictions over a month reduced the overall error. The best model performance was obtained at rural sites, with an average mean fractional bias (MFB) of −0.03 and mean fractional error (MFE) of 0.70. Concentrations at suburban and urban sites were underestimated with overall MFB=−0.57 and MFE=0.89. Predicted PAH concentrations were highest in January with better model performance (MFB=0.12, MFE=0.69; including all sites), and lowest in July with worse model performance (MFB=−0.90, MFE=1.08). Including heterogeneous reactions of several PAHs with O3 on particle surface reduced the over-prediction bias in winter, although significant uncertainties were expected due to relative simple treatment of the heterogeneous reactions in the current model.

Mercury emission and speciation from industrial gold production using roasting process

Gold production has been identified as an important source of anthropogenic mercury emissions. Few measurements have been conducted on the mercury emission in the industrial gold production. In this study, field measurements on mercury concentration and speciation profile in the roasting flue gas were conducted in a two-stage roasting gold smelter, and the corresponding mercury emission factors were obtained using mass balance analysis. The average mercury concentration in the feed gold concentrates was 730.0μg/kg, and the daily input mercury was 94.9g in this research. In the roasting procedure, 38.4%, 27.3% and 9.0% of input mercury was removed into the sulfuric acid, contaminated water and arsenic, respectively, while 22.8% of input mercury flowed into the cyanidation-refining procedure within the roasting residue and the dust collected from the gas cooling tower and the electrostatic precipitator. Finally, 2.3% and 5.9% of input mercury was emitted into the atmosphere with the roasting flue gas and the refining flue gas. Mercury concentration in the roasting flue gas was 4.02μg/m3, where the proportion of Hgp:Hg2+:Hg0 was 11:57:33. The balance calculation results indicated that the atmospheric mercury emission factor was 2.27×10−3gmercury/g gold produced for the tested smelter. Both the emission factor and mercury removal efficiencies of air pollution control devices are useful for development of a more accurate emission inventory.

An updated experimental and kinetic modeling study of n-heptane oxidation

This work presents an updated experimental and kinetic modeling study of n-heptane oxidation. In the experiments, ignition delay times of stoichiometric n-heptane/air mixtures have been measured in two different high-pressure shock tubes in the temperature range of 726–1412K and at elevated pressures (15, 20 and 38bar). Meanwhile, concentration versus time profiles of species have been measured in a jet-stirred reactor at atmospheric pressure, in the temperature range of 500–1100K at φ=0.25, 2.0 and 4.0. These experimental results are consistent with those from the literature at similar conditions and extend the current data base describing n-heptane oxidation.Based on our experimental observations and previous modeling work, a detailed kinetic model has been developed to describe n-heptane oxidation. This kinetic model has adopted reaction rate rules consistent with those recently developed for the pentane isomers and for n-hexane. The model has been validated against data sets from both the current work and the literature using ignition delay times, speciation profiles measured in a jet-stirred reactor and laminar flame speeds over a wide range of conditions. Good agreement is observed between the model predictions and the experimental data. The model has also been compared with several recently published kinetic models of n-heptane and shows an overall better performance. This model may contribute to the development of kinetic mechanisms of other fuels, as n-heptane is a widely used primary reference fuel. Since the sub-mechanisms of n-pentane, n-hexane and n-heptane have adopted consistent reaction rate rules, the model is more likely to accurately simulate the oxidation of mixtures of these fuels. In addition, the successful implementation of these rate rules have indicated the possibility of their application for the development of mechanisms for larger hydrocarbon fuels, which are of great significance for practical combustion devices.