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Polybrominated diphenyl ethers and their methoxylated metabolites in anchovy (Coilia sp.) from the Yangtze River Delta, China
2010
Su, Guan-yong | Gao, Zi-shen | Yu, Yijun | Ge, Jia-chun | Wei, Si | Feng, Jian-fang | Liu, Feng-yan | Giesy, John P. | Lam, Michael H. W. | Yu, Hong-xia
Background, aim, and scope Polybrominated diphenyl ethers (PBDEs) and their metabolites are toxic to animals, and concentrations of the PBDEs metabolites can exceed those of the parent materials. But no information was available on concentrations of PBDEs metabolites in the lower Yangtze River in the region around Jiangsu Province of China, which is heavily urbanized and industrialized area. The aims of this study were to determine whether PBDEs and their methoxylated PBDEs (MeO-PBDEs) were accumulated in Coilia sp. in this area and to investigate the potential sources for these two kinds of brominated organic pollutants. Materials and methods Samples of four species of anchovy were collected from eight sites in the lower Yangtze River, Taihu Lake, and Hongzehu Lake. Concentrations of 13 PBDEs congeners and eight methoxylated PBDEs were determined by use of organic solvent extraction, followed by gas chromatography and mass spectrometry. Results and discussion The frequencies of detection for PBDEs and MeO-PBDEs were 92% and 53%, respectively. Concentrations of ∑PBDEs ranged from not detected (ND) to 77 ng/g lipids (ND-3.8 ng/g wet weight). Concentrations of ∑MeO-PBDEs in anchovy ranged from ND to 48 ng/g lipids (ND-8.2 ng/g wet weight). The PBDE concentrations in anchovy from the Yangtze River Delta were similar to or less than those reported for other species from other locations around the world, while the concentrations of MeO-PBDEs were comparable to or slightly less than those reported in other studies. This is the first report of MeO-PBDEs in biota of China. Conclusions The results of this study as well as those of other studies suggest that PBDEs in anchovy are primarily of synthetic origin and released by human activities, while MeO-PBDEs in anchovy are primarily from nature as natural products from the sea instead of metabolism of PBDEs in anchovy.
Show more [+] Less [-]Characteristics of exhaust gas, liquid products, and residues of printed circuit boards using the pyrolysis process
2010
Chiang, Hung-Lung | Lo, Cho-Ching | Ma, Sen-Yi
Introduction The pyrolytic method was employed to recycle metals and brominated compounds blended into printed circuit boards (PCBs). Methods PCBs were crushed into pieces 4.0-4.8 mm in size, and the crushed pieces were pyrolyzed at temperatures ranging from 200 to 500°C. The compositions of pyrolytic residues, liquid products, and exhaust were analyzed by inductively coupled plasma atomic emission spectrometer, inductively coupled plasma mass spectrometry, and gas chromatography-mass spectrometry. Pyrolytic exhaust was collected by an impinger system in an ice bath cooler to analyze the composition fraction of the liquid product, and uncondensable exhaust was collected for gas constituent analysis. Results Phenol, methyl-phenol, and bromo-phenol were attributed mainly to the liquid product. Metal content was low in the liquid product. In addition, CO, CO₂, CH₄, and H₂ were the major components of pyrolytic exhaust. Conclusions Brominated and chlorinated compounds—i.e., dichloromethane, trans-1,2 dichloroethylene, cis-1,2 dichloroethylene, 1,1,1-trichloroethane, tetrachloromethane, bromophenol, and bromoform—could be high, up to the several parts per million (ppm) level. Low molecular weight volatile organic compounds (VOCs)—i.e., methanol, acetone, ethyl acetate, acrylonitrile, 1-butene, propene, propane, and n-butane—contributed a large fraction of VOCs. The concentrations of toluene, benzene, xylene, ethylbenzene, and styrene were in the ppm range.
Show more [+] Less [-]Influence of linear alkylbenzene sulfonate (LAS) on the structure of Alphaproteobacteria, Actinobacteria, and Acidobacteria communities in a soil microcosm
2010
Sánchez-Peinado, Mª del Mar | Gonzalez-López, Jesús | Martínez-Toledo, Mª Victoria | Pozo, Clementina | Rodelas, Belén
Background, aim, and scope Linear alkylbenzene sulfonate (LAS) is the most used anionic surfactant in a worldwide scale and is considered a high-priority pollutant. LAS is regarded as a readily biodegradable product under aerobic conditions in aqueous media and is mostly removed in wastewater treatment plants, but an important fraction (20-25%) is immobilized in sewage sludge and persists under anoxic conditions. Due to the application of the sludge as a fertilizer, LAS reaches agricultural soil, and therefore, microbial toxicity tests have been widely used to evaluate the influence of LAS on soil microbial ecology. However, molecular-based community-level analyses have been seldom applied in studies regarding the effects of LAS on natural or engineered systems, and, to our knowledge, there are no reports of their use for such appraisals in agricultural soil. In this study, a microcosm system is used to evaluate the effects of a commercial mixture of LAS on the community structure of Alphaproteobacteria, Actinobacteria, and Acidobacteria in an agricultural soil. Material and methods The microcosms consisted of agricultural soil columns (800 g) fed with sterile water (8 ml h⁻¹) added of different concentration of LAS (10 or 50 mg l⁻¹) for periods of time up to 21 days. Sterile water was added to control columns for comparison. The structures of Alphaproteobacteria, Actinobacteria, and Acidobacteria communities were analyzed by a cultivation independent method (temperature gradient gel electrophoresis (TGGE) separation of polymerase chain reaction (PCR)-amplified partial 16S rRNA genes). Relevant populations were identified by subsequent reamplification, DNA sequencing, and database comparisons. Results Cluster analysis of the TGGE fingerprints taking into consideration both the number of bands and their relative intensities revealed that the structure of the Alphaproteobacteria community was significantly changed in the presence of LAS, at both concentrations tested. The average number of bands was significantly lower in the microcosms receiving 50 mg l⁻¹ LAS and in the lower portion of soil cores. The clear differentiation of the samples of the upper portion of the soil columns amended with LAS was specifically related to the presence and intensity of a distinctive major band (named band class 7). There was a statistically significant positive correlation between the concentrations of LAS detected in soil portions taken from LAS 10 mg l⁻¹ and LAS 50 mg l⁻¹ microcosms and the relative intensity of band class 7 in the corresponding TGGE profiles. Prevalent Alphaproteobacteria populations in the soil microcosms had close similarity (>99%) to cultivated species affiliated to genera of the Rhizobiaceae, Methylocystaceae, Hyphomicrobiaceae, Rhodospirillaceae, Brucellaceae, Bradyrhizobiaceae, and Caulobacteraceae families. The population represented by band class 7 was found closely related to the genus Phenylobacterium (Caulobacteraceae). According to cluster analysis of TGGE profiles, the structure of both Actinobacteria and Acidobacteria communities in the soil microcosms was remarkably stable in the presence of LAS at the two concentrations tested, as most bands were universally present in all samples and displayed fairly similar relative intensities. Discussion Previous studies by others authors, based on biological and chemical tests, concluded that LAS toxicity was not an important microbial selection factor in sludge amended soil, while work based on the use of molecular fingerprinting to evaluate the impact of LAS in aqueous media and marine sediments showed that concentrations as low as 1 mg l⁻¹ significantly influence the development of the bacterial community structure. Although TGGE is not a strictly quantitative method due to the bias introduced by the PCR reaction, changes of band intensity through experiments are a consequence of a change in the relative abundance of the corresponding populations in the community and can be used as a semiquantitative measure of bacterial diversity. Our results evidence that the Phenylobacterium population represented by band class 7 was favored by the presence of increasing concentrations of LAS in the soil and turned into a dominant population, suggesting its possible ability to use LAS in soil as a source of nutrients. As studies with pure cultures are required to confirm the ability of this population to degrade LAS, isolation strategies are currently under development in our laboratory. The weak effect of LAS on the structure of Actinobacteria and Acidobacteria communities is particularly interesting, as to our knowledge, there are no previous reports regarding the effects of LAS on these bacterial groups in soil. Conclusions, recommendations, and perspectives The Phenylobacterium-related alphaproteobacterial population identified in this work was selectively enriched in LAS polluted soil and is a plausible candidate to play a relevant role in the biotransformation of the surfactant under the conditions tested. The surfactant had no remarkable effects on the Actinobacteria and Acidobacteria fingerprints in soil, even when present at concentrations widely exceeding those reached in soil immediately after sludge application. TGGE fingerprinting provides a reliable and low time-consuming method for the monitoring of the bacterial community structure and dynamics, and we recommend its integration with the biological and chemical analyses usually applied in risk assessment of LAS in the environment.
Show more [+] Less [-]Source identification of sulphate forming salts on sandstones from monuments in Salamanca, Spain—a stable isotope approach
2010
Schleicher, Nina | Recio Hernández, Clemente
Background, aim and scope Salt efflorescences markedly contribute to the alteration and deterioration of building material, in this case the Villamayor Sandstone of the facades in the Old Town of Salamanca, Spain (United Nations Educational, Scientific and Cultural Organization world cultural heritage site). A better understanding of the mechanisms of salt formation and the involved elements would allow more precise measures in monument conservation. The magnesium which is required for the salt precipitation originates from selective processes of hydrolysis. The source of sulphate, however, is presently not as clear. Identifying the source of the sulphur was the main goal of this research. Isotope ratio measurement of δ³⁴S and δ¹⁸O was used to clarify the origins of Mg sulphate salts. Materials and methods A total of 56 Mg sulphate samples were collected in two different seasons (July and November 2005) from monuments of the Old Town of Salamanca. These sampled salt efflorescences were analysed for δ³⁴S and δ¹⁸O by mass spectrometry. A ‘dual-inlet' type by VG Isotech was used for δ³⁴S and continuous flow type Isoprime by GV Instruments for δ¹⁸O. Samples were measured in triplicates and standard material was analysed for quality control. Results δ³⁴S values range between 3.6‰ and 15.4‰ with a median value of 10.2‰ for the July samples and of 10.1‰ for November samples. The results of the sulphur ratios hint towards a bimodal distribution (with modes at δ³⁴S = 6‰ and 12‰) for winter samples, which is less obvious during summer. δ¹⁸O values range from 7.1‰ to 41.1‰. However, most values range from 7.1‰ to 20.8‰, whereas only few summer samples show outliers towards higher δ¹⁸O values. The median δ¹⁸O value for July samples is 15.5‰ and for November samples 14.6‰. Discussion The isotopic ratios of the analysed sulphate samples were compared with values of possible source materials. Sulphur sources in the case of Salamanca are barites from the Villamayor Sandstone itself, sea spray, sulphides from regional rocks, biogenic sulphur (soil, avian excreta), as well as sulphur from anthropogenic sources such as building materials (especially mortar) or traffic exhaust. Salamanca is a representative site for non-industrial cities with no heavy industry and thus, there are no significant SO₂ emissions from industry. Conclusions Based on the measured isotopic ratios, it was ascertained that more than one sole sulphur source is present. However, based on additional information about the source material and possible transport ways, some sources could be excluded whereas others only played a minor role. Finally, there is strong indication that the main sulphur source is atmospheric pollution and the exhaust emissions from vehicles in particular, while mortar as building material also contributes to a minor extent. The δ¹⁸O values support this hypothesis. Moreover, the reported δ¹⁸O values are a strong indicator of the secondary nature of the Mg sulphates. Isotope ratio measurement and especially the combined use of δ³⁴S and δ¹⁸O values have proven to be a good instrument in clarifying the origin of salt efflorescences on buildings. Recommendations and perspectives Further studies should investigate more closely the isotopic composition of atmospheric aerosols in Salamanca in order to get a more detailed knowledge about the main sulphur sources, as well as to quantify the relation between the isotopic values and the amount and mineralogical form of the salts.
Show more [+] Less [-]Brominated phenols, anisoles, and dioxins present in blue mussels from the Swedish coastline
2010
Löfstrand, Karin | Malmvärn, Anna | Haglund, Peter | Bignert, Anders | Bergman, Åke | Asplund, L. (Lillemor)
INTRODUCTION: Naturally occurring hydroxylated polybrominated diphenyl ethers (OH-PBDEs), their methoxylated counterparts (MeO-PBDEs), and polybrominated dibenzo-p-dioxins (PBDDs), together with their potential precursors polybrominated phenols (PBPs) and polybrominated anisoles (PBAs), were analyzed in blue mussels (Mytilus edulis) gathered along the east coast (bordering the Baltic Sea) and west coast of Sweden (bordering the North Sea). Brown algae (Dictyosiphon foenicolaceus) and cyanobacteria (Nodularia spumigena) from the Baltic Sea, considered to be among the primary producers of these compounds, were also analyzed for comparison. MATERIALS AND METHODS: The samples were liquid–liquid extracted, separated into a phenolic and a neutral fraction, and subsequently analyzed by gas chromatography–mass spectrometry (GS-MS). RESULTS AND DISCUSSION: The levels of OH-PBDEs, MeO-PBDEs and PBDDs were significantly higher in Baltic Sea mussels than in those from the west coast, whereas the levels of PBPs and PBAs displayed the opposite pattern. The blue mussels from the Baltic Sea contained high levels of all analyzed substances, much higher than the levels of, e.g., polybrominated diphenyl ethers. In addition, the GC-MS chromatogram of the phenolic fraction of the west coast samples was dominated by four unknown peak clusters, three of which were tentatively identified as dihydroxy-PBDEs and the other as a hydroxylated-methyl-tetraBDE. CONCLUSIONS: Clearly, all of the compounds analyzed are natural products, both in the Baltic and the North Sea. However, the geographical differences in composition may indicate different origin, e.g., due to differences in the occurrence and/or abundance of various algae species along these two coasts or possibly a more extensive dilution on the west coast.
Show more [+] Less [-]Different natural organic matter isolates cause similar stress response patterns in the freshwater amphipod, Gammarus pulex
2010
Bedulina, Darya S. | Timofeyev, Maxim A. | Zimmer, Martin | Zwirnmann, Elke | Menzel, Ralph | Steinberg, Christian E. W.
Background, aim, and scope Dissolved humic substances (HSs) are exogenous stressors to aquatic plants and animals which activate a variety of transcriptional and biochemical reactions or block photosynthesis. While there are consistent indications which structures may lead to reduced photosynthetic activity, there is much less clear information available on which HS structures or building blocks act as stressors in animals. Consequently, this work was designed to comparatively study the impact of natural organic matter (NOMs) from different sources on major anti-stress mechanisms in one single animal. We utilized major antioxidant responses and relative expression levels of stress proteins (small HSPs and HSP70) and expected that different HSs provoke different response patterns. Materials and methods We tested the freshwater amphipod Gammarus pulex which was collected from several shallow creeks in Northern Germany. All specimens were maintained in aerated 5-L tanks with filtered water from their natural environment at 10°C with prior acclimation. Animals were fed ad libitum with a commercial preparation once every second day. The exposure water was exchanged with the same frequency. NOMs were isolated from three different sources: two from small brown-water lakes in Northern Germany by reverse osmosis and the third one as an aqueous extract from a black layer of a Brazilian sandbar soil (State of Rio de Janeiro). The rationale was to apply NOMs of contrasting quality. Chemical fingerprint features of the NOMs were taken by high-performance size exclusion chromatography. As stress parameters in the animals, the activities of peroxidase and catalase were recorded quantitatively, and stress proteins, HSP70, as well as small α-crystalline HSPs were analyzed semiquantitatively. Results The three NOMs clearly differed in molecular masses, humic substance contents, the moieties of polysaccharides, and low-molecular-weight substances. With the exception of one short-term response, the peroxidase activity increased after 3 to 12 h exposure, whereas the catalase activity did not show any significant modulation. With one exception, the stress protein expression increased after 30 min exposure in a biphasic pattern, and the sHSPs responded less strongly than HSP70. Discussion Although the quality of the exposed NOMs differs significantly, a rather uniform response pattern appears in the animals. Obviously, the contrasting contents of HSs and polysaccharides did not affect the anti-stress response of the exposed gammarids which is in contrast to previous lifespan studies with Caenorhabditis elegans. Furthermore, all NOM sources led to increased contents of both HSP70 and sHSPs. To the best of our knowledge, this is the first protein study to show that also small HSPs are expressed when the animals are exposed against humic material. Conclusions Since the response patterns of the exposed gammarids, in contrast to the initial hypothesis, are rather uniform and since HSs are parts of life on Earth, we furthermore presume that they may have been a primordial exogenous trigger for the development of anti-stress systems in exposed organisms. Recommendations and perspectives Effect studies of chemical stresses on organisms should consider exposure to both natural triggers and xenobiotic compounds in low concentrations—in order to prospectively differentiate between these triggers and, subsequently, classify them.
Show more [+] Less [-]Estimation of the cancer risk to humans resulting from the presence of cyclophosphamide and ifosfamide in surface water
2010
Kümmerer, Klaus | Al-Ahmad, Ali
Background, aim, and scope Anti-tumour agents and their metabolites are largely excreted into effluent, along with other pharmaceuticals. In the past, investigations have focused on the input and analysis of pharmaceuticals in surface and ground water. The two oxazaphosphorine compounds, cyclophosphamide and ifosfamide are important cytostatic drugs used in the chemotherapy of cancer and in the treatment of autoimmune diseases. Their mechanism of action, involving metabolic activation and unspecific alkylation of nucleophilic compounds, accounts for genotoxic and carcinogenic effects described in the literature and is reason for environmental concern. The anti-tumour agents cyclophosphamide (CP) and ifosfamide (IF) were not biodegraded in biodegradation tests. They were not eliminated in municipal sewage treatment plants. Degradation by photochemically formed HO radicals may be of some relevance only in shallow, clear, and nitrate-rich water bodies but could be further exploited for elimination of these compounds by advanced oxidation processes, i.e. in a treatment of hospital waste water. Therefore, CP and IF are assumed to persist in the aquatic environment and to enter drinking water via surface water. The risk to humans from input of CP and IF into surface water is not known. Materials and methods The local and regional, i.e. nationwide predicted environmental concentration (PEClocal, PECregional) of CP and IF was calculated for German surface water. Both compounds were measured in hospital effluents, and in the influent and effluent of a municipal treatment plant. Additionally, published concentrations in the effluent of sewage treatment plants and surface water were used for risk assessment. Excretion rates were taken into account. For a worst-case scenario, maximum possible ingestion of CP or IF by drinking 2 L a day of unprocessed surface water over a life span of 70 years was calculated for adults. Elimination in drinking water processing was neglected, as no data is available. This intake was compared with intake during anti-cancer treatment. Results and discussion Intake of CP and IF for anti-cancer treatment is typically 10 g within a few months. Under such conditions, a relative risk of 1.5 for the carcinogenic compounds CP and IF is reported in the literature. In the worst case, the maximum possible intake by drinking water is less than 10⁻³ (IF) and 10⁻⁵ (CP) of this amount, based on highest measured local concentrations. On a nationwide average, the factor is approx. 10⁻⁶ or less. Conclusions The additional intake of CP and IF due to their emission into surface water and its use without further treatment as drinking water is low compared to intake within a therapy. This approach has shortcomings. It illustrates the current lack of methodology and knowledge for the specific risk assessment of carcinogenic pharmaceuticals in the aquatic environment. IF and CP are directly reacting with the DNA. Therefore, with respect to health effects a safe threshold concentration for these compounds cannot be given. The resulting risk is higher for newborns and children than for adults. Due to the lack of data the risk for newborns and children cannot be assessed fully. The data presented here show that according to present knowledge the additional risk of cancer cannot be fully excluded, especially with respect to children. Due to the shortage of data for effects of CP and IF in low doses during a whole lifespan, possible effects were assessed using data of high doses of CP and IF within short-term ingestion, i.e. therapy. This remains an unresolved issue. Anyway, the risk assessment performed here could give a rough measure of the risks on the one hand and the methodological shortcomings on the other hand which are connected to the assessment of the input of genotoxic and carcinogenic pharmaceuticals such as CP and IF into the aquatic environment. Therefore, we recommend to take measures to reduce the input of CP and IF and other carcinogenic pharmaceuticals. We hope that our manuscript further stimulates the discussion about the human risk assessment for carcinogenic pharmaceuticals in the aquatic environment. Recommendations and perspectives CP and IF are carcinogens. With respect to newborn and children, reduction of the emission of CP and IF into effluent and surface water is recommended at least as a precautionary measure. The collection of unused and outdated drugs is a suitable measure. Collection of patients' excreta as a measure of input reduction is not recommended. Data suitable for the assessment of the risk for newborn and children should be collected in order to perform a risk assessment for these groups. This can stimulate discussion and give new insights into risk assessment for pharmaceuticals in the environment. Our study showed that in the long term, effective risk management for the reduction of the input of CP and IF are recommendable.
Show more [+] Less [-]Extractable organic matter of Standard Reference Material 1649a influences immunological response induced by pathogen-associated molecular patterns
2010
Ulrich, Kerstin | Wölfle, Sabine | Mayer, Anja | Heeg, Klaus | Braunbeck, T (Thomas) | Erdinger, Lothar | Bartz, Holger
Background, aim, and scope Lungs are permanently and simultaneously challenged by airborne microorganisms and airborne pollutants. Temporal increase of airborne particulate matter (APM), a potential carrier for extractable organic matter (EOM), degrades the situation of pulmonary patients. The Ah receptor (AhR) has been described as an important factor influencing the immunological challenge by viral infections. Molecular mechanisms underlying epidemiological observations are not well understood. Cytokine secretion (IL-6, IL-8, and TGF-β) from human bronchial epithelial cells (Beas2B) was determined as an indicator for immune responses upon co-stimulation with an artificial analog of viral dsRNA [polyinosinic/polycytidylic acid, (PIC)] and EOM of Standard Reference Material 1649a (SRM). Since polycyclic aromatic hydrocarbons are major components of APM usually acting via the AhR, particular focus was on AhR involvement. Materials and methods Cytokine secretion was demonstrated by enzyme-linked immunosorbent assay. To mimic the activation of organic matter during contact of particles with the human lung, Soxhlet extraction of SRM was performed. In some experiments, the AhR was blocked by α-naphthoflavone. Results Microbial stimulation (PIC) induced Beas2B cytokine release, whereas isolated exposure to EOM of APM did not. Co-stimulation with EOM and PIC increased IL-8 secretion, whereas neither IL-6 nor TGF-β was affected. Blocking of the AhR suppressed the release of IL-8. Discussion Organic compounds adsorbed on airborne particulate matter influence the cytokine secretion of lung epithelial cells induced by pathogen-associated molecular patterns. Recommendations and perspectives Further investigation of these observations is required to understand the molecular mechanisms underlying adverse health effects of APM reported in epidemiological studies.
Show more [+] Less [-]Water-soluble main ions in precipitation over the southeastern Adriatic region: chemical composition and long-range transport
2010
Đorđević, Dragana S. | Tošić, Ivana | Unkašević, Miroslava | Đurašković, Pavle
Background, aim and scope Precipitation samples collected from 1995 to 2000 at meteorological station in the eastern outskirts of Herceg Novi (Montenegro) were analysed on Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, SO₄ ²⁻, NO₃ ⁻ and NH₄ ⁺. Four-day backward trajectory simulations were conducted during the precipitation period to investigate the regional transport of main ions and their deposition in the region of the southeastern Adriatic Sea. The air mass trajectories were classified into six trajectory categories by the origin and direction of their approach to Herceg Novi. Materials and methods A bottle and funnel with a small net between them was used for sampling at a height of 1.5 m above the ground. The concentrations of Cl⁻, NO₃ ⁻, NH₄ ⁺ and SO₄ ²⁻ were determined spectrophotometrically, the concentrations of Na⁺ and K⁺ were determined by the FAES method and the concentrations of Mg²⁺ and Ca²⁺ by the FAAS method. The factor analysis technique (PCA analysis) based on the calculation of the factors was employed to differentiate the contribution of emission sources to the content of the main ions in the precipitation. The obtained data sets were processed using the SPSS 11.5 statistical program. The Hybrid Single-Particle Lagrangian Integrated Trajectory model was used to study the air origin for the city of Herceg Novi (42°27′N, 18°33′E), Montenegro. Discussion The following origins of the air masses were considered: northern Europe (NE), eastern Europe-northeastern Europe (EE-NE); eastern Mediterranean-southeastern Europe (EM-SE); Africa-Central Mediterranean (A-CM); western Mediterranean (WM); western Europe-Central Europe (WE-CE) and undefined. The heights and frequencies of precipitation coming by air masses from northern Europe and eastern-northeastern Europe are the lowest. On the contrary, the heights and frequencies of precipitation coming by air masses from the western Mediterranean (36.6%) and Africa and the Central Mediterranean (30.6%) are the highest. The sea salt components (Na⁺, Cl⁻, Mg²⁺) are significantly correlated, except for air masses originating from the northern and eastern European regions. Significant correlations between SO₄ ²⁻ and NO₃ ⁻ are found in air masses coming from the western Europe and North Africa, over the Mediterranean. Conclusions The highest volume-weighted mean (VWM) of: SO₄ ²⁻ , NH₄ ⁺ and Mg²⁺ are for precipitation from EE-NE while the highest values of VWM of Cl ⁻ are from WM and of K⁺ are from WE-CE. Long-range transport of Sahara dust is confirmed. Recommendations and perspectives For better estimation of origins of water-soluble ions in precipitation expanding list of analysis on anions of organic acids, such as HCOO⁻, CH₃COO⁻, and C₂H₂COO⁻, could be indicative of volatile organic compounds emitted by vegetation but also traffic. The chemical composition of precipitation together with a study of air backward trajectories is the proper tool for tracking the long-range transport of water-soluble ions and estimating transboundary pollution.
Show more [+] Less [-]On the relationship between ozone and its precursors in the Pearl River Delta: application of an observation-based model (OBM)
2010
Cheng, Hairong | Guo, Hai | Wang, Xinming | Saunders, Sam M | Lam, S. H. M | Jiang, Fei | Wang, Tijian | Ding, Aijun | Lee, Shuncheng | Ho, K. F
Background, aim, and scope Photochemical smog, characterized by high concentrations of O₃ and fine particles, is of great concern in the urban areas, in particular megacities and city clusters like the Pearl River Delta. Materials, methods, and results Ambient ozone (O₃) and its precursors were simultaneously measured at two sites in the Pearl River Delta, namely, Wan Qing Sha (WQS) in Guangzhou and Tung Chung (TC) in Hong Kong, from 23 October to 01 December 2007 in order to explore their potential relationship. Eight high O₃ episode days were identified at WQS and two at TC during the sampling campaign, indicating a more serious O₃ pollution in Guangzhou than in Hong Kong. An observation-based model was employed to determine the ozone-precursor relationship. At both sites, O₃ production was found to be volatile organic compound (VOC)-limited, which is consistent with previous observations. Anthropogenic hydrocarbons played a key role in O₃ production, while reducing nitric oxide emissions aided the buildup of O₃ concentrations. Among VOC species, the summed relative incremental reactivity (RIR) of the top 12 compounds accounted for 89% and 85% of the total RIR at WQS and TC, respectively, indicating that local photochemical O₃ formation can be mainly attributed to a small number of VOC species. Discussion and conclusions A large increment in both simulated HO₂ and O₃ concentrations was achieved with additional input of hourly carbonyl data. This suggested that apart from hydrocarbons, carbonyls might significantly contribute to the O₃ production in the Pearl River Delta.
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