Integrating dual C and N isotopic approach to elemental and mathematical solutions for improving the PM source apportionment in complex urban and industrial cities: Case of Tarragona - Spain

Identification of dominant airborne Particulate Matter (PM) sources is essential for maintaining high air quality standards and thus ensuring a good public health. In this study, different approaches were applied for source apportionment of three PM fractions (PM1, PM2.5 and PM10) at the outdoor of 14 schools of a coastal city with a significant land use interweaving such as Tarragona (Spain). PM were collected in 24h-quartz microfiber filters in two seasonal campaigns (cold and warm), together with nine local potential sources, so a total of 84 samples were chemically, mineralogically, and isotopically characterised. Source apportionment was assessed by (i) main chemical components, (ii) Principal Component Analysis (PCA), (iii) dual C and N isotope approach, and (iv) a Bayesian isotope mixing model. When chemical concentrations were grouped into marine, crustal, secondary inorganic aerosols and organic matter + elemental carbon categories, the unaccounted component reached 45% of PM mass. The PCA allowed to identify also traffic and industrial contributions, reducing the unaccounted mass to about 25%. Adding δ13C and δ15N values, secondary organic aerosol could be estimated and a continuous contribution of diesel combustion was identified together with a remarkable use of natural gas in winter. Isotopic values were better understood when considering air masses back trajectories and a possible long-distance contribution from coal-fired electric generating units (EGUs). Finally, using Bayesian dual isotope mixing models, the unaccounted PM mass was reduced up to 5% when adding these EGUs to marine-carbonate related, road traffic, domestic heating, waste incinerator and livestock waste contributions. The added value of the dual isotope approach combined with a Bayesian isotope mixing model, in comparison with conventional chemical approaches, was thus demonstrated for PM source apportionment in an urban and industrial site where many sources and processes converge and can then be applied to other complex cities

Simultaneous determination of methyl tert.-butyl ether and its degradation products, other gasoline oxygenates and benzene, toluene, ethylbenzene and xylenes in Catalonian groundwater by purge-and-trap-gas chromatography-mass spectrometry

14 pages, 5 figures, 4 tables.-- PMID: 12800934 [PubMed].-- Available on line May 8, 2003.-- Erratum published in: Journal of Chromatography A 1007(1-2): 209-210 (Jul 25, 2003).In Catalonia (northeast Spain), a monitoring program was carried out to determine methyl tert.-butyl ether (MTBE), its main degradation products, tert.-butyl alcohol (TBA), tert.-butyl formate (TBF), and other gasoline additives, the oxygenate dialkyl ethers ethyl tert.-butyl ether, tert.-amyl methyl ether and diisopropyl ether and the aromatic compounds benzene, toluene, ethylbenzene and xylene (BTEX) in 21 groundwater wells that were located near different gasoline point sources (a gasoline spill and underground storage tank leakage). Purge-and-trap coupled to gas chromatography–mass spectrometry was optimised for the simultaneous determination of the above mentioned compounds and enabled to detect concentrations at ng/l or sub-μg/l concentrations. Special attention was given to the determination of polar MTBE degradation products, TBA and TBF, since not much data on method performance and environmental levels are given on these compounds in groundwater. All samples analysed contained MTBE at levels between 0.3 and 70 μg/l. Seven contaminated hot spots were identified with levels up to US Environmental Protection Agency drinking water advisory (20–40 μg/l) and a maximum concentration of 670 μg/l (doubling the Danish suggested toxicity level of 350 μg/l). Samples with high levels of MTBE contained 0.1–60 μg/l of TBA, indicating (but not proving) in situ degradation of parent compound. In all cases, BTEX was at low concentrations or not detected showing less solubility and persistence than MTBE. This fact confirms the suitability of MTBE as a tracer or indicator of long-term gasoline contamination than the historically used BTEX.This research is part of the WATCH (EVK1-CT-2000-00059) EU project funded by the EU Environment and Sustainable Development sub-program and from the Ministerio de Ciencia y Tecnología (REN2001-5039-E).Peer reviewe

Simultaneous determination of methyl tert-butyl ether, its degradation products and other gasoline additives in soil samples by closed-system purge-and-trap gas chromatography–mass spectrometry

11 pages, 4 tables, 3 figures.-- PMID: 16904119 [PubMed].-- Printed version published Nov 3, 2006.A new protocol for the simultaneous determination of methyl tert-butyl ether (MTBE); its main degradation products: tert-butyl alcohol (TBA) and tert-butyl formate (TBF); other gasoline additives, oxygenate dialkyl ethers: ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE); aromatics: benzene, toluene, ethylbenzene and xylenes (BTEX) and other compounds causing odour events such as dicyclopentadiene (DCPD) and trichloroethylene (TCE) in soils has been developed. On the basis of US Environmental Protection Agency (EPA) method 5035A, a fully automated closed-system purge-and-trap coupled to gas chromatography/mass spectrometry (P&T-GC/MS) was optimised and permitted to detect μg/kg concentrations in solid matrices avoiding losses of volatile compounds during operation processes.Parameters optimised were the sampling procedure, sample preservation and storage, purging temperature, matrix effects and quantification mode. Using 5 g of sample, detection limits were between 0.02 and 1.63 μg/kg and acceptable method precision and accuracy was obtained provided quantification was performed using adequate internal standards.Soil samples should be analysed as soon as possible after collection, stored under −15°C for not longer than 7 days if degradation products have to be analysed. The non-preservative alternative (empty vial) provided good recoveries of the most analytes when freezing the samples up to 7 day holding time, however, if biologically active soil are analysed the preservation with trisodium phosphate dodecahydrate (Na3PO4·12H2O or TSP) is strongly recommended more than sodium bisulphate (NaHSO4). The method was finally applied to provide threshold and background levels of several gasoline additives in a point source and in sites not influenced by gasoline spills. The proposed method provides the directions for the future application on real samples in current monitoring programs at gasoline pollution risk sites where till now little monitoring data for MTBE in soils are available.This research was part of the WATCH (EVK1-CT-2000-00059) and PROMOTE (contract no. 518074; GOCE) EU projects that were funded by the EU Environment and Sustainable Development sub-program and from the Ministerio de Ciencia y Tecnología (REN2001-5039-E). M.R. acknowledges a grant from the Department of Universities, Research and Information Society of the Generalitat de Catalunya (2005FIR 00348) and thanks Dori Fanjul and Roser Chaler for helpful GC/MS assistance.Peer reviewe

Analysis, occurrence and fate of MTBE in the aquatic environment over the past decade

14 pages, 4 figures, 2 tables.-- Printed version published Nov 2006.In the past decade, it became progressively more evident that fuel oxygenate methyl tertiary butyl ether (MTBE) is nearly ubiquitous in the worldwide environment. The frequency of detection of MTBE rivals other volatile organic compounds (VOCs) that have been produced and used for a much longer time. Its mere presence in water bodies used as drinking-water reservoirs (rivers, lakes or groundwater tables) has aroused concern about its potential sources, persistence and possible adverse effects (aesthetic or toxic implications) for end users and aquatic life. This article aims to provide an updated overview of the analytical techniques applied for current environmental concentrations, the occurrence of MTBE as a pollutant in the different aquatic compartments, the relevance of diffuse and point sources and the different options for remediation of MTBE-contaminated sites.Some results shown in the present review came from EU projects [WATCH (EVK1–CT–2000–00059) and P-THREE (EVK1-2001-00283)] funded by the EU Environment and Sustainable Development sub-program and from the Spanish Ministerio de Educación y Ciencia Project EVITA (CTM2004-06255-CO3-01). M. Rosell acknowledges a grant from Department of Universities, Research and Information Society, La Generalitat de Catalunya (2005FIR 00348).Peer reviewe

Analysis, occurrence and fate of MTBE in the aquatic environment over the past decade

14 pages, 4 figures, 2 tables.-- Printed version published Nov 2006.In the past decade, it became progressively more evident that fuel oxygenate methyl tertiary butyl ether (MTBE) is nearly ubiquitous in the worldwide environment. The frequency of detection of MTBE rivals other volatile organic compounds (VOCs) that have been produced and used for a much longer time. Its mere presence in water bodies used as drinking-water reservoirs (rivers, lakes or groundwater tables) has aroused concern about its potential sources, persistence and possible adverse effects (aesthetic or toxic implications) for end users and aquatic life. This article aims to provide an updated overview of the analytical techniques applied for current environmental concentrations, the occurrence of MTBE as a pollutant in the different aquatic compartments, the relevance of diffuse and point sources and the different options for remediation of MTBE-contaminated sites.Some results shown in the present review came from EU projects [WATCH (EVK1–CT–2000–00059) and P-THREE (EVK1-2001-00283)] funded by the EU Environment and Sustainable Development sub-program and from the Spanish Ministerio de Educación y Ciencia Project EVITA (CTM2004-06255-CO3-01). M. Rosell acknowledges a grant from Department of Universities, Research and Information Society, La Generalitat de Catalunya (2005FIR 00348).Peer reviewe

Variations in 13C/12C and D/H enrichment factors of aerobic bacterial fuel oxygenate degradation

8 pages, 3 figures.-- PMID: 17410802 [PubMed].-- Printed version published on Mar 15, 2007.Supplementary information (Suppl. figure S1, 6 pages) available at: http://pubs.acs.org/doi/suppl/10.1021/es0616175/suppl_file/es0616175si20061213_010401.pdfReliable compound-specific isotope enrichment factors are needed for a quantitative assessment of in situ biodegradation in contaminated groundwater. To obtain information on the variability on carbon and hydrogen enrichment factors (εC, εH) the isotope fractionation of methyl tertiary (tert-) butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) upon aerobic degradation was studied with different bacterial isolates. Methylibium sp. R8 showed a carbon and hydrogen isotope enrichment upon MTBE degradation of -2.4 ± 0.1 and -42 ± 4‰, respectively, which is in the range of previous studies with pure cultures (Methylibium petroleiphilum PM1) as well as mixed consortia. In contrast, εC of the β-proteobacterium L108 (-0.48 ± 0.05‰) and Rhodococcus ruber IFP 2001 (-0.28 ± 0.06‰) was much lower and hydrogen isotope fractionation was negligible (εH < -0.2‰). The varying isotope fractionation pattern indicates that MTBE is degraded by different mechanisms by the strains R8 and PM1 compared to L108 and IFP 2001. The carbon and hydrogen isotope fractionation of ETBE by L108 (εC = - 0.68 ± 0.06‰ and εH = -14 ± 2‰) and IFP 2001 εC = -0.8 ± 0.1‰ and εH = -11 ± 4‰) was very similar and seemed slightly higher than the fractionation observed upon MTBE degradation by the same strains. The low carbon and hydrogen enrichment factors observed during MTBE and ETBE degradation by L108 and IFP 2001 suggest a hydrolysis-like reaction type of the ether bond cleavage compared to oxidation of the alkyl group as suggested for the strains PM1 and R8. The variability of carbon and hydrogen enrichment factors should be taken into account when interpreting isotope pattern of fuel oxygenates with respect to biodegradation in contamination plumes.We thank Ursula Günther, Monika Neytschev, and Cornelia Schumann for technical support at the UFZ. We are also grateful to Erik Arvin (Technical University of Denmark, Lyngby, Denmark) and Françoise Fayolle-Guichard and Frédéric Monot (Institute Françoise du Petrole, Cedex, France) for providing an enrichment culture and strain IFP 2001, respectively. Part of the work was financed by the German Federal Ministry of Education and Research (02 WN 0348) within the METLEN project and by the UFZ (SAFIRA). The fellowship of Mònica Rosell was supported by AXIOM-Marie Curie Host Fellowships For Early Stage Training (EST) (contract MEST-CT-2004-8332) and Catalonian fellowship for research in an outsider country (2005 BE 00008) in the framework of AXIOM project "Assessment of in situ Transformation of Xenobiotic Organic Material". She also received a regular PhD grant from Department of Universities, Research and Information Society of Generalitat de Catalunya (expedient 2005FIR 00348).Peer reviewe

Fate of gasoline oxygenates in conventional and multilevel wells of a contaminated groundwater table in Düsseldorf, Germany

11 pages, 5 figures, 5 tables.-- PMID: 16398114 [PubMed].-- Printed version published Nov 2005.In a gasoline-contaminated site in Düsseldorf, Germany a two-year monitoring program was carried out to determine the presence, behavior, and fate of 12 gasoline additives in a total of 96 samples from 14 groundwater wells. The origin of contamination was suspected to be a gasoline spill at a gas station. Target compounds were methyl-tert-butyl ether (MTBE), its main degradation products, tert-butyl alcohol (TBA) and tert-butyl formate (TBF); other gasoline additives, oxygenate dialkyl ethers: Ethyl-tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE); aromatics: Benzene, toluene, ethylbenzene and xylenes (BTEX), and other compounds causing odor problems: Dicyclopentadiene and trichloroethylene. Purge and trap coupled with gas chromatography-mass spectrometry permitted detection of ng/L concentrations. Ninety of the 96 samples analyzed contained MTBE at levels varying between 0.01 to 645 μg/L. Five contaminated hot spots were identified with levels up to U.S. Environmental Protection Agency (U.S. EPA) drinking water advisory values (20–40 μg/L) and one of them doubling Danish suggested toxicity level of 350 μg/L at a depth of 11 m. No significant natural attenuation was found in MTBE degradation, although samples with high levels of MTBE contained 0.1 to 440 μg/L of TBA. These levels were attributed to its presence in the contamination source more than MTBE degradation. tert-Butyl alcohol was found to be recalcitrant in groundwater. In all cases, BTEX were at low concentrations or not detected, showing less persistence than MTBE. The monitoring of the contamination plume showed that the distribution of the MTBE and TBA in the aquifer formed a similar vertical concentration profile that was influenced by the groundwater flow direction.This research was part of the WATCH (EVK1-CT-2000-00059) European Union project that was funded by the European Union Environment and Sustainable Development subprogram and from the Ministerio de Ciencia y Tecnología (REN2001-5039-E).Peer reviewe

Dual C-Br isotope fractionation indicates distinct reductive dehalogenation mechanisms of 1,2-dibromoethane in Dehalococcoides- and Dehalogenimonas-containing cultures

Brominated organic compounds such as 1,2-dibromoethane (1,2-DBA) are highly toxic groundwater contaminants. Multi-element compound-specific isotope analysis bears the potential to elucidate the biodegradation pathways of 1,2-DBA in the environment, which is crucial information to assess its fate in contaminated sites. This study investigates for the first time dual C−Br isotope fractionation during in vivo biodegradation of 1,2-DBA by two anaerobic enrichment cultures containing organohaliderespiring bacteria (i.e., either Dehalococcoides or Dehalogenimonas). Different εbulk C values (−1.8 ± 0.2 and −19.2 ± 3.5¿, respectively) were obtained, whereas their respective εbulk Br values were lower and similar to each other (−1.22 ± 0.08 and −1.2 ± 0.5¿), leading to distinctly different trends (ΛC−Br = Δδ13C/Δδ81Br ≈ εbulkC /εbulkBr ) in a dual C−Br isotope plot (1.4 ± 0.2 and 12 ± 4, respectively). These results suggest the occurrence of different underlying reaction mechanisms during enzymatic 1,2-DBA transformation, that is, concerted dihaloelimination and nucleophilic substitution (SN2-reaction). The strongly pathway-dependent ΛC−Br values illustrate the potential of this approach to elucidate the reaction mechanism of 1,2-DBA in the field and to select appropriate εbulkC values for quantification of biodegradation. The results of this study provide valuable information for future biodegradation studies of 1,2-DBA in contaminated sites