δ13CDIC tracing of dissolved inorganic carbon sources at Three Gorges Reservoir, China.

In order to understand water chemistry after impoundment of the Three Gorges Reservoir (TGR), the authors assessed the hydrogeochemical parameters (water temperature, pH, conductivity, dissolved O2), major element composition, and the carbon stable isotopic value of dissolved inorganic carbon (δ13CDIC) in summer and winter at various depths in the water column at TGR in 2009. In reservoir water, the DO values are lower in winter than in summer, but the pH values and conductivity values are higher. Ca2+ and Na+ are the dominant cations and HCO3- and SO42- are the dominant anions. In surface waters, the δ13CDIC values are more negative in summer than they are in winter, whereas the dissolved inorganic carbon (DIC) concentrations are relatively lower. In the water column, the DIC and δ13CDIC values do not change significantly with water depth or seasons. The DIC content shows a dilution effect in summer and is not modified by phytoplanktonic activity or photosynthesis. Even after the dam obstructed flow, the chemical profile of water in TGR is similar to that of the natural rivers before impoundment. Therefore, in this study, the water at TGR still had riverine characteristics and was still a heterotrophic system.

Low-smoke chulha in Indian slums: study protocol for a randomised controlled trial.

BACKGROUND: Biomass fuel is used as a primary cooking source by more than half of the world's population, contributing to a high burden of disease. Although cleaner fuels are available, some households continue using solid fuels because of financial constraints and absence of infrastructure, especially in non-notified slums. The present study documents a randomised controlled study investigating the efficacy of improved cookstove on the personal exposure to air pollution and the respiratory health of women and children in an Indian slum. The improved cookstove was based on co-creation of a low-smoke chulha with local communities in order to support adaption and sustained uptake. METHODS: The study will be conducted in a non-notified slum called Ashrayanagar in Bangalore, India. The study design will be a 1:1 randomised controlled intervention trial, including 250 households. The intervention group will receive an improved cookstove (low-smoke chulha) and the control group will continue using either the traditional cookstove (chulha) or a combination of the traditional stove and the kerosene/diesel stove. Follow-up time is 1 year. Outcomes include change in lung function (FEV1/FVC), incidence of pneumonia, change in personal PM2.5 and CO exposure, incidence of respiratory symptoms (cough, phlegm, wheeze and shortness of breath), prevalence of other related symptoms (headache and burning eyes), change in behaviour and adoption of the stove. Ethical clearance was obtained from the Institutional Ethics Committee of the Indian Institute of Public Health Hyderabad- Bengaluru Campus. DISCUSSION: The findings from this study aim to provide insight into the effects of improved cookstoves in urban slums. Results can give evidence for the decrease of indoor air pollution and the improvement of respiratory health for children and women. TRIAL REGISTRATION: The trial was registered with clinicaltrials.gov on 21 June 2016 with the identifier NCT02821650 ; A Study to Test the Impact of an Improved Chulha on the Respiratory Health of Women and Children in Indian Slums.

Stardust in meteorites.

Primitive meteorites, interplanetary dust particles, and comets contain dust grains that formed around stars that lived their lives before the solar system formed. These remarkable objects have been intensively studied since their discovery a little over twenty years ago and they provide samples of other stars that can be studied in the laboratory in exquisite detail with modern analytical tools. The properties of stardust grains are used to constrain models of nucleosynthesis in red giant stars and supernovae, the dominant sources of dust grains that are recycled into the interstellar medium by stars.

Evaluation of reagentless pH modification for in situ ocean analysis: determination of dissolved inorganic carbon using mass spectrometry.

RATIONALE: In situ analytical techniques that require the storage and delivery of reagents (e.g., acidic or basic solutions) have inherent durability limitations. The reagentless electrolytic technique for pH modification presented here was developed primarily to ease and to extend the longevity of dissolved inorganic carbon (DIC) determinations in seawater, but can also be used for other analytical methods. DIC, a primary carbon dioxide (CO(2)) system variable along with alkalinity, controls seawater pH, carbonate saturation state, and CO(2) fugacity. Determinations of these parameters are central to an understanding of ocean acidification and global climate change. METHODS: Electrodes fabricated with electroactive materials, including manganese(III) oxide (Mn(2)O(3)) and palladium (Pd), were examined for potential use in electrolytic acidification. In-line acidification techniques were evaluated using a bench-top membrane introduction mass spectrometry (MIMS) setup to determine the DIC content of artificial seawater. Linear least-squares (LLSQ) calibrations for DIC concentration determinations over a range between 1650 and 2400 µmol kg(-1) were obtained, using both the novel electrolytic and conventional acid addition techniques. RESULTS: At sample rates of 4.5 mL min(-1), electrodes clad with Mn(2)O(3) and Pd were able to change seawater pH from 7.6 to 2.8 with a power consumption of less than 3 W. Although calibration curves were influenced by sampling rates at a flow of 4.5 mL min(-1), the 1σ measurement precision for DIC was of the order of ±20 µmol kg(-1). CONCLUSIONS: Calibrations obtained with the novel reagentless technique and the in-line addition of strong acid showed similar capabilities for DIC quantification. However, calculations of power savings for the reagentless technique relative to the mechanical delivery of stored acid demonstrated substantial advantages of the electrolytic technique for long-term deployments (>1 year).

Isotopic imprints of mountaintop mining contaminants.

Mountaintop mining (MTM) is the primary procedure for surface coal exploration within the central Appalachian region of the eastern United States, and it is known to contaminate streams in local watersheds. In this study, we measured the chemical and isotopic compositions of water samples from MTM-impacted tributaries and streams in the Mud River watershed in West Virginia. We systematically document the isotopic compositions of three major constituents: sulfur isotopes in sulfate (δ(34)SSO4), carbon isotopes in dissolved inorganic carbon (δ(13)CDIC), and strontium isotopes ((87)Sr/(86)Sr). The data show that δ(34)SSO4, δ(13)CDIC, Sr/Ca, and (87)Sr/(86)Sr measured in saline- and selenium-rich MTM impacted tributaries are distinguishable from those of the surface water upstream of mining impacts. These tracers can therefore be used to delineate and quantify the impact of MTM in watersheds. High Sr/Ca and low (87)Sr/(86)Sr characterize tributaries that originated from active MTM areas, while tributaries from reclaimed MTM areas had low Sr/Ca and high (87)Sr/(86)Sr. Leaching experiments of rocks from the watershed show that pyrite oxidation and carbonate dissolution control the solute chemistry with distinct (87)Sr/(86)Sr ratios characterizing different rock sources. We propose that MTM operations that access the deeper Kanawha Formation generate residual mined rocks in valley fills from which effluents with distinctive (87)Sr/(86)Sr and Sr/Ca imprints affect the quality of the Appalachian watersheds.

Determinants of exposure to dust and dust constituents in the Norwegian silicon carbide industry.

INTRODUCTION: The aim of this study was to identify important determinants of dust exposure in the Norwegian silicon carbide (SiC) industry and to suggest possible control measures. METHODS: Exposure to total dust, respirable dust, quartz, cristobalite, SiC, and fiber was assessed in three Norwegian SiC plants together with information on potential determinants of exposure. Mixed-effect models were constructed with natural log-transformed exposure as the dependent variable. RESULTS: The exposure assessment resulted in about 700 measurements of each of the sampled agents. Geometric mean (GM) exposure for total dust, respirable dust, fibers, and SiC for all workers was 1.6mg m(-3) [geometric standard deviation (GSD) = 3.2], 0.30mg m(-3) (GSD = 2.5), 0.033 fibers cm(-3) (GSD = 5.2), and 0.069mg m(-3) (GSD = 3.1), respectively. Due to a large portion of quartz and cristobalite measurements below the limit of detection in the processing and maintenance departments (>58%), GM for all workers was not calculated. Work in the furnace department was associated with the highest exposure to fibers, quartz, and cristobalite, while work in the processing department was associated with the highest total dust, respirable dust, and SiC exposure. Job group was a strong determinant of exposure for all agents, explaining 43-82% of the between-worker variance. Determinants associated with increased exposure in the furnace department were location of the sorting area inside the furnace hall, cleaning tasks, building and filling furnaces, and manual sorting. Filling and changing pallet boxes were important tasks related to increased exposure to total dust, respirable dust, and SiC in the processing department. For maintenance workers, increased exposure to fibers was associated with maintenance work in the furnace department and increased exposure to SiC was related to maintenance work in the processing department. CONCLUSION: Job group was a strong determinant of exposure for all agents. Several tasks were associated with increased exposure, indicating possibilities for exposure control measures. Recommendations for exposure reduction based on this study are (i) to separate the sorting area from the furnace hall, (ii) minimize manual work on furnaces and in the sorting process, (iii) use remote controlled sanders/grinders with ventilated cabins, (iv) use closed systems for filling pallet boxes, and (v) improve cleaning procedures by using methods that minimize dust generation.

Can new energy demonstration city policy reduce carbon emissions? A quasi-natural experiment from China.

Against achieving carbon peaking by 2030 and carbon neutrality by 2060 context in China, the new energy demonstration city policy (NEDCP) has a crucial function to perform in promoting resource utilization efficiency, building the green development policy system, and facilitating carbon emission reduction. However, existing research has rarely investigated the contribution of NEDCP on carbon reduction. To investigate the policy effect of NEDCP, the differences-in-differences (DID) model is introduced to quantify the influence of NEDCP on carbon reduction, taking a statistical sample of 285 Chinese cities over the period 2005-2017 on the basis of exploring the intrinsic mechanism of NEDCP on carbon emissions. The statistical results reveal that NEDCP significantly inhibits carbon emissions. NEDCP's dampening impact on carbon reduction is more pronounced in the eastern area but not in other areas. City size and resource endowment heterogeneity results suggest that NEDCP significantly inhibits the output of carbon emissions in non-resource-based and large cities but insignificantly in resource-based and small- and medium-sized cities. Finally, we conclude that policy-makers should not only broaden the scope of NEDCP implementation continuously but also design relevant policy combination tools following the basic characteristics of each city to provide institutional guarantees for achieving carbon emission reduction.

Carbon emission fluctuations of Chinese inter-regional interaction: a network multi-hub diffusion perspective.

The "double-carbon" policy is a new opportunity for the transformation of China's production sector. With steady economic growth, each province has proposed specific policies aimed at cleaner production. However, the interactions between regions and the complex linkages between industries have hindered the implementation of the "double-carbon" policy. In order to address this issue, we introduced a complex network framework with multiple industries at a national level. The framework aimed to clarify whether there is fluctuation diffusion in China's multi-province multi-industry carbon emission system, to identify key industries and regions, and to answer the question of "who" is the most effective in governance. The results showed that the fluctuations of industrial carbon emissions had a cross-regional diffusion effect in China indeed. The diffusion capacity of industry fluctuation depends on whether the industry is located at a "hub" position in the network. Hub industries with strong capacity can spread the carbon emission fluctuation of themselves and upstream or downstream industries to the whole country through regional interactions. This characteristic of the hub industry should be taken into account in governance to maximize the effectiveness of emission reduction. Shandong and Inner Mongolia, as important provinces for the production of intermediate products and energy chemicals in China, had a greater role to play in global carbon supply push from their hub industries than in the demand pull. The pulling capacity of Beijing-Tianjin-Hebei region to the national carbon demand side was greater than that of Yangtze River Delta and Pearl River Delta. These findings might have implications for environmental and economic policymaking, particularly with regard to cross-provincial coordinated systemic solutions and policy anchors for synergy with industries.

A novel strategy for retrospective exposure assessment in the Norwegian silicon carbide industry.

The objective was to construct a retrospective job-exposure matrix (JEM) for the Norwegian silicon carbide industry. More than 3300 historical total dust measurements were available (1967-2005); however, there were few measurements of other agents. Total dust measurements were therefore used as the basis for the JEM, and a novel method was developed to estimate exposure to other agents. Multiple linear regression models were developed to describe historical exposure to total dust. Exposure estimates were extrapolated backward to periods without exposure data by adjustments for process and work-hour related changes. An exposure assessment study was performed where total dust was sampled in parallel with fibers or respirable dust. The respirable dust was analyzed for the content of quartz, cristobalite, and silicon carbide. Mixed-effect models were developed to estimate the exposure to these agents from total dust exposure, plant, and job group. Exposure to asbestos and polycyclic aromatic hydrocarbons was assigned qualitatively. Multiple linear regression models of total dust described historical exposure best in the furnace department (R(2) (adj) = 0.49-0.74). Models in the other departments explained less variance (R(2) (adj) = 0.12-0.32). Exposure determinants and total dust explained a substantial proportion of the between- (70-100%) and within-worker (8.0-54%) variance in the mixed-effect models. The relative bias between available historical measurements and the estimated exposure to dust components varied between -39% (fiber) and 40% (quartz). However, corrections were not considered necessary due to limitations in the historical data. The component-specific metrices were sufficiently different from each other (r(Pearson) < 0.7), with the exception of total and respirable dust (r(Pearson) = 0.84) and total dust and cristobalite (r(Pearson) = 0.72), and will enable component-specific epidemiologic analyses in the future. Improved and less correlated estimates of exposure levels for the different components in the dust were obtained with the updated exposure assessment. Due to limitations in the measurement data, assumptions had to be made, especially in the period before 1967. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a file containing tables outlining multiple linear regression models for prediction of total dust exposure in the processing departments of Norwegian SiC producing plants, evaluation of the predictive abilities of the reduced total dust models, and mixed models for pedicting exposure to fibers and respirable quartz, cristobalite, non-fibrous silicon carbide and respirable dust from total dust exposure.].

Theoretical versus observed gas-particle partitioning of carbonyl emissions from motor vehicles.

A state-of-the-science thermodynamic model describing gas-particle absorption processes was used to predict the gas-particle partitioning of mixtures of approximately 60 carbonyl compounds emitted from low-emission gasoline-powered vehicles, three-way catalyst gasoline-powered vehicles, heavy-duty diesel vehicles under the idle-creep condition (HDDV idle), and heavy-duty diesel vehicles under the five-mode test (HDDV 5-mode). Exhaust was diluted by a factor of 120-580 with a residence time of approximately 43 sec. The predicted equilibrium absorption partitioning coefficients differed from the measured partitioning coefficients by several orders of magnitude. Time scales to reach equilibrium in the dilution sampling system were close to the actual residence time during the HDDV 5-mode test and much longer than the actual residence time during the other vehicle tests. It appears that insufficient residence time in the sampling system cannot uniformly explain the failure of the absorption mechanism to explain the measured partitioning. Other gas-particle partitioning mechanisms (e.g., heterogeneous reactions, capillary adsorption) beyond the simple absorption theory are needed to explain the discrepancy between calculated carbonyl partitioning coefficients and observed partitioning. Both of these alternative partitioning mechanisms imply great challenges for the measurement and modeling of semi-volatile primary organic aerosol (POA) species from motor vehicles. Furthermore, as emitted particle concentrations from newer vehicles approach atmospheric background levels, dilution sampling systems must fundamentally change their approach so that they use realistic particle concentrations in the dilution air to approximately represent real-world conditions. Samples collected with particle-free dilution air yielding total particulate matter concentrations below typical ambient concentrations will not provide a realistic picture of partitioning for semi-volatile compounds.

Determining Inorganic and Organic Carbon.

Carbon is the element which makes up the major fraction of lipids and carbohydrates, which could be used for making biofuel. It is therefore important to provide enough carbon and also follow the flow into particulate organic carbon and potential loss to dissolved organic forms of carbon. Here we present methods for determining dissolved inorganic carbon, dissolved organic carbon, and particulate organic carbon.

A simple predictive model for estimating relative e-cigarette toxic carbonyl levels.

E-cigarette devices are wide ranging, leading to significant differences in levels of toxic carbonyls in their respective aerosols. Power can be a useful method in predicting relative toxin concentrations within the same device, but does not correlate well to inter-device levels. Herein, we have developed a simple mathematical model utilizing parameters of an e-cigarette's coil and wick in order to predict relative levels of e-liquid solvent degradation. Model 1, which is coil length/(wick surface area*wraps), performed in the moderate-to-substantial range as a predictive tool (R2 = 0.69). Twelve devices, spanning a range of coil and wick styles, were analyzed. Model 1 was evaluated against twelve alternative models and displayed the best predictability. Relationships that included power settings displayed weak predictability, validating that power levels cannot be reliably compared between devices due to differing wicking and coil components and heat transfer efficiencies.

Quantitative determination of airborne respirable non-fibrous alpha-silicon carbide by x-ray powder diffractometry.

OBJECTIVES: The purpose of the present investigation was to establish a method for the determination of airborne respirable non-fibrous silicon carbide (SiC). The main application is within the industrial production of SiC. METHODS: Due to the complex airborne aerosol mixture of crystalline compounds in the SiC industry, X-ray powder diffractometry was selected as the most appropriate method. Without any international standard material for the respirable fraction of non-fibrous SiC, pure and suitable products from three SiC plants in Norway were selected. These products have a median particle diameter in the range 4.4-5.1 mum. The method is based on thin sample technique, with the dust deposited on a polycarbonate filter. Absorption correction is done by standard procedures with the use of a silver filter, situated below the polycarbonate filter. RESULTS: The diffraction line used for quantitative determination was selected carefully. This was done to avoid interferences from quartz, cristobalite, and graphite, which all are airborne components present in the atmosphere during the industrial process. The instrumental limit of detection for the method is 12 microg. CONCLUSIONS: This method has been used to determine airborne non-fibrous SiC in a comprehensive ongoing project in the Norwegian SiC industry for further epidemiological studies. The method is fully applicable for compliance work.

Determination of sulfur forms in wine including free and total sulfur dioxide based on molecular absorption of carbon monosulfide in the air-acetylene flame.

A new method for the determination of sulfur forms in wine, i.e., free SO(2), total SO(2), bound SO(2), total S, and sulfate, is presented. The method is based on the measurement of the carbon monosulfide (CS) molecular absorption produced in a conventional air-acetylene flame using high-resolution continuum source absorption spectrometry. Individual sulfur forms can be distinguished because of the different sensitivities of the corresponding CS molecular absorption. The sensitivity of free SO(2) is about three times higher than the value for bound SO(2) and sulfate. The method makes use of procedures similar to those used in classic reference methods. Its performance is verified by analyzing six wine samples. Relative standard deviations are between 5 and 13% for free SO(2) and between 1 and 3% for total SO(2). For the validation of the accuracy of the new method, the results are compared with those of reference methods. The agreement of the values for total SO(2) with values of the classic method is satisfactory: five out of six samples show deviations less than 16%. Due to the instability of free SO(2) in wine and the known problems of the used reference method, serious deviations of the free SO(2) results are found for three samples. The evaluation of the limits of detection focuses on the value for free SO(2), which is the sulfur form having by far the lowest concentration in wine. Here, the achievable limit of detection is 1.8 mg L(-1). [figure: see text] Detection of non-metal elements using continuum source flame absorption spectrometry.

Exposure to fibres, crystalline silica, silicon carbide and sulphur dioxide in the norwegian silicon carbide industry.

OBJECTIVES: The aim of this study was to assess personal exposure to fibres, crystalline silica, silicon carbide (SiC) and sulphur dioxide in the Norwegian SiC industry. METHODS: Approximately 720 fibre samples, 720 respirable dust samples and 1400 total dust samples were collected from randomly chosen workers from the furnace, processing and maintenance departments in all three Norwegian SiC plants. The respirable dust samples were analysed for quartz, cristobalite and non-fibrous SiC content. Approximately 240 sulphur dioxide samples were collected from workers in the furnace department. RESULTS: The sorting operators from all plants, control room and cleaning operators in Plant A and charger, charger/mix and payloader operators in Plant C had a geometric mean (GM) of fibre exposure above the Norwegian occupational exposure limit (OEL) (0.1 fibre cm(-3)). The cleaner operators in Plant A had the highest GM exposure to respirable quartz (20 mug m(-3)). The charger/mix operators in Plant C had the highest GM exposure to respirable cristobalite (38 mug m(-3)) and the refinery crusher operators in Plant A had the highest GM exposure to non-fibrous SiC (0.65 mg m(-3)). Exposure to the crystalline silica and non-fibrous SiC was generally low and between 0.4 and 2.1% of the measurements exceeded the OELs. The cleaner operators in Plant A had the highest GM exposure to respirable dust (1.3 mg m(-3)) and total dust (21 mg m(-3)). GM exposures for respirable dust above the Norwegian SiC industry-specific OEL of 0.5 mg m(-3) were also found for refinery crusher operators in all plants and mix, charger, charger/mix and sorting operators in Plant C. Only 4% of the total dust measurements exceeded the OEL for nuisance dust of (10 mg m(-3)). Exposure to sulphur dioxide was generally low. However, peaks in the range of 10-100 p.p.m. were observed for control room and crane operators in Plants A and B and for charger and charger/mix operators in Plant C. CONCLUSION: Workers in the SiC industry are exposed to a mixture of several agents including SiC fibres, quartz, cristobalite, non-fibrous SiC and sulphur dioxide. Exposure levels were generally below the current Norwegian OELs; however, high exposure to fibres and respirable dust still occurs in the furnace department.

Discrimination of three Ephedra species and their geographical origins based on multi-element fingerprinting by inductively coupled plasma mass spectrometry.

Discrimination of species and geographical origins of traditional Chinese medicine (TCM) is essential to prevent adulteration and inferior problems. We studied Ephedra sinica Stapf, Ephedra intermedia Schrenk et C.A.Mey. and Ephedra przewalskii Bge. to investigate the relationship between inorganic element content and these three species and their geographical origins. 38 elemental fingerprints from six major Ephedra-producing regions, namely, Inner Mongolia, Ningxia, Gansu, Shanxi, Shaanxi, and Sinkiang, were determined to evaluate the importance of inorganic elements to three species and their geographical origins. The contents of 15 elements, namely, N, P, K, S, Ca, Mg, Fe, Mn, Na, Cl, Sr, Cu, Zn, B, and Mo, of Ephedra samples were measured using inductively coupled plasma mass spectroscopy. Elemental contents were used as chemical indicators to classify species and origins of Ephedra samples using a radar plot and multivariate data analysis, including hierarchical cluster analysis (HCA), principal component analysis (PCA), and discriminant analysis (DA). Ephedra samples from different species and geographical origins could be differentiated. This study showed that inorganic elemental fingerprint combined with multivariate statistical analysis is a promising tool for distinguishing three Ephedra species and their geographical origins, and this strategy might be an effective method for authenticity discrimination of TCM.

Inorganic carbon limitations on nitrification: experimental assessment and modelling.

Nitrification is a two-step process that involves two different biomass populations: ammonia oxidising biomass (AOB) and nitrite oxidising biomass (NOB). Both populations are autotrophic (i.e. their carbon source is inorganic). Therefore, a deficit of this substrate should result in a decrease of the process rate. Recent technology advances such as the SHARON process have brought new scenarios in biological nitrogen removal where these limitations should be considered. Hence, this work examines the inorganic carbon limitation using respirometric and titrimetric techniques. For this aim, the nitrification rate was measured at different total inorganic carbon (TIC) concentrations. The experimental results obtained show that AOB was limited at TIC concentrations lower than 3mmol CL(-1). At the same time, no carbon source limitation for NOB was observed in spite of the low TIC concentrations attained (lower than 0.1mmol CL(-1)). The AOB limitation could be successfully modelled using Monod, Tessier and sigmoidal kinetics. The best fit was obtained with sigmoidal kinetics. However, unexpected biomass activity (oxygen consumption) was observed despite a very low TIC concentration (lower than 0.1mmol CL(-1)).

Decomposition of belowground litter and metal dynamics in salt marshes (Tagus Estuary, Portugal).

The concentrations of C, Fe, Mn, Zn, Cu, Pb and Cd were determined monthly in decomposing roots of Halimione portulacoides, using litterbag experiments, in two salt marshes of the Tagus estuary with different levels of contamination. Although carbon concentrations varied within a narrow interval during the experiment, litter decomposed rapidly in the first month (weight loss between 0.051 and 0.065 g d(-1)). The time variation of metals was examined in terms of Me/C ratios and metal stocks. Ratios of Fe/C and Mn/C and their metal stocks increased in spring, presumably due to the precipitation of oxides in the surface of decomposing roots. Subsequent decrease of Fe/C and Mn/C ratios suggests the use of Fe and Mn oxides, as electron acceptors, in the organic matter oxidation. Zinc, Cu, Pb and Cd ratios to C were, in general, higher than at initial conditions implying that metal that leached out was slower than carbon. However, metal stocks decreased during the experiment indicating that incorporation or sorption of metals in Fe and Mn oxides did not counterbalance the amount of Zn, Pb and Cd released from decomposing litter. An exception was observed for Cu, since stock in the less contaminated marsh (Pancas) increased during the decomposition, indicating that litter was efficient on Cu binding under more oxidising conditions. These results emphasize the importance of litter decomposition and sediment characteristics on metal cycling in salt marshes.

Dynamics of phosphorus, nitrogen and carbon removal in a horizontal subsurface flow constructed wetland.

The dynamics of nitrogen (N), phosphorus (P) and carbon (C) accumulation in the filter material of a horizontal subsurface constructed wetland (HSSF CW; established in 1997) and in a specially designed oil-shale ash filter (2002) for P retention have been studied. Concentrations of N, P and C in filter media (coarse sand) in the HSSF beds show an increasing trend. Both the annual accumulation of P and increasing outflow concentrations of P in the HSSF CW reflect the possible saturation of filter media with P after 8 years working. Tested ash material derived from oil-shale combustion demonstrated very high P removal efficiency in laboratory batch experiments. However, during the first 4 months of the in situ ash filter experiment, the efficiency of P removal was about 71% (an average outflow concentration of 1.9 mg L(-1) was achieved). Subsequently, the efficiency decreased to 10-20%, which might be a sign of saturation or clogging due to quick biofilm development on the ash particles. The increasing of hydraulic retention time and the improvement of design for maximal contact between material and wastewater are considered to be key factors that can provide optimal pH for the removal processes.

[Identification of the carbonaceous fraction of particulate matter pollution in the urban area of Rome--Part I]. / Caratterizzazione della frazione carboniosa dell'inquinamento particellare nell'area urbana di Roma Parte I.

BACKGROUND: Particulate Matter pollution in urban areas is due to different sources and varies in composition, where the carbonaceous fraction is of particularly importance due to its effects on human health and the climate. OBJECTIVES: to study the contribution of the carbonaceous fraction in PM10 pollution in the urban area of Rome and identify the composition of its organic fraction. METHODS: Separation of Elemental Carbon (EC) from Organic Carbon (OC) was carried out by means of a 5400 Ambient Carbon Particulate Monitor 5400 based on a two-step combustion procedure. RESULTS: The carbonaceous fraction in central Rome accounted for 30-40% of PM10 at ground level and consisted of 60-70% Elemental Carbon and 30-40% Organic Carbon. Polycyclic Aromatic Hydrocarbons, n-Alkanes and n-Alkanoic acids were identified among the constituents of the OC fraction, sulphates, nitrate and ammonia in the hydrosoluble inorganic fraction and heavy metals (Cd, Cr, Fe, Ni, Pb, V, Zn) in the non-hydrosoluble inorganic fraction. PM10 temporal trends were interpreted using measurement of the natural radioactivity (radon and its short-lived decay products) as tracer of the dynamic properties of the atmospheric boundary layer. CONCLUSIONS: Carbonaceous particulate matter is a fundamental parameter to evaluate atmospheric pollution due to combustion processes and can be considered as a specific index of motor vehicle traffic pollution. Its separation into elemental carbon, of primary origin, and organic carbon, of both primary and secondary origin, is toxicologically signficant and in order to study the formation mechanisms of photochemical pollution.