Seasonal variations of anhydrosugars in PM2.5 in the Pearl River Delta Region, China

Anhydrosugars including levoglucosan and mannosan are the most effective organic tracers for biomass burning aerosol in the atmosphere. In this study, to investigate the contribution of biomass burning emissions to the aerosol burden in the Pearl River Delta (PRD) region, China, 24-hour integrated PM2.5 samples were collected simultaneously at four locations, (i) Guangzhou (GZ), (ii) Zhaoqing (ZQ) in Guangdong province, (iii) Hok Tsui (HT) and (iv) Hong Kong Polytechnic University (PU) in Hong Kong, in four seasons between 2006 and 2007. Levoglucosan and mannosan, together with water-soluble inorganic ions and water-soluble organic carbon (WSOC), were determined to elucidate the seasonal and spatial variations in biomass burning contributions. The concentrations of levoglucosan and mannosan were on average 82.4±123 and 5.8±8.6 ng m−3, respectively. The WSOC concentrations ranged from 0.2 to 9.4 µg m−3, with an average of 2.1±1.6 µg m−3. The relative contributions of biomass burning emissions to OC were 33% in QZ, 12% in GZ, 4% at PU and 5% at HT, respectively, estimated by the measured levoglucosan to organic carbon ratio (LG/OC) relative to literature-derived LG/OC values. The contributions from biomass burning emissions were in general 1.7–2.8 times higher in winter than those in other seasons. Further, it was inferred from diagnostic tracer ratios that a significant fraction of biomass burning emissions was derived from burning of hard wood and likely also from field burning of agricultural residues, such as rice straw, in the PRD region. Our results highlight the contributions from biomass/biofuel burning activities on the regional aerosol budget in South China

Seasonal variations of C-1-C-4 alkyl nitrates at a coastal site in Hong Kong: Influence of photochemical formation and oceanic emissions

Five C-1-C-4 alkyl nitrates (RONO2) were measured at a coastal site in Hong Kong in four selected months of 2011 and 2012. The total mixing ratios of C-1-C-4 RONO2 (Sigma 5RONO2) ranged from 15.4 to 143.7 pptv with an average of 65.9 +/- 33.0 pptv. C-3-C-4 RONO2 (2-butyl nitrate and 2-propyl nitrate) were the most abundant RONO2 during the entire sampling period. The mixing ratios of C-3-C-4 RONO2 were higher in winter than those in summer, while the ones of methyl nitrate (MeONO2) were higher in summer than those in winter. Source analysis suggests that C-2-C-4 RONO2 were mainly derived from photochemical formation along with biomass burning (58.3-71.6%), while ocean was a major contributor to MeONO2 (53.8%) during the whole sampling period. The photochemical evolution of C-2-C-4 RONO2 was investigated, and found to be dominantly produced by the parent hydrocarbon oxidation. The notable enrichment of MeONO2 over C-3-C-4 RONO2 was observed in a summer episode when the air masses originating from the South China Sea (SCS) and MeONO2 was dominantly derived from oceanic emissions. In order to improve the accuracy of ozone (O-3) prediction in coastal environment, the relative contribution of RONO2 from oceanic emissions versus photochemical formation and their coupling effects on O-3 production should be taken into account in future studies. (C) 2017 Elsevier Ltd. All rights reserved

Spatial and temporal variability of iodine in aerosol

In this work, we describe the compilation and homogenization of an extensive data set of aerosol iodine field observations in the period between 1963 and 2018 and we discuss its spatial and temporal dependences by comparison with CAM-Chem model simulations. A close to linear relationship between soluble and total iodine in aerosol is found (∼80% aerosol iodine is soluble), which enables converting a large subset of measurements of soluble iodine into total iodine. The resulting data set shows a distinct latitudinal dependence, with an enhancement toward the Northern Hemisphere (NH) tropics and lower values toward the poles. This behavior, which has been predicted by atmospheric models to depend on the global distribution of the main oceanic iodine source (which in turn depends on the reaction of ozone with aqueous iodide on the sea water-air interface, generating gas-phase I 2 and HOI), is confirmed here by field observations for the first time. Longitudinally, there is some indication of a wave-one profile in the tropics, which peaks in the Atlantic and shows a minimum in the Pacific. New data from Antarctica show that the south polar seasonal variation of iodine in aerosol mirrors that observed previously in the Arctic, with two equinoctial maxima and the dominant maximum occurring in spring. While no clear seasonal variability is observed in NH middle latitudes, there is an indication of different seasonal cycles in the NH tropical Atlantic and Pacific. Long-term trends cannot be unambiguously established as a result of inhomogeneous time and spatial coverage and analytical methods

Iodine speciation in atmospheric aerosols in the marine boundary layer

Iodine chemistry plays an important role in the tropospheric ozone depletion and the new particle formation in the Marine Boundary Layer (MBL). The sources, reaction pathways, and the sinks of iodine are investigated using lab experiments and field observations. The aims of this work are, firstly, to develop analytical methods for iodine measurements of marine aerosol samples especially for iodine speciation in the soluble iodine; secondly, to apply the analytical methods in field collected aerosol samples, and to estimate the characteristics of aerosol iodine in the MBL. Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) was the technique used for iodine measurements. Offline methods using water extraction and Tetra-methyl-ammonium-hydroxide (TMAH) extraction were applied to measure total soluble iodine (TSI) and total insoluble iodine (TII) in the marine aerosol samples. External standard calibration and isotope dilution analysis (IDA) were both conducted for iodine quantification and the limits of detection (LODs) were both 0.1 μg L- 1 for TSI and TII measurements. Online couplings of Ion Chromatography (IC)-ICP-MS and Gel electrophoresis (GE)-ICP-MS were both developed for soluble iodine speciation. Anion exchange columns were adopted for IC-ICP-MS systems. Iodide, iodate, and unknown signal(s) were observed in these methods. Iodide and iodate were separated successfully and the LODs were 0.1 and 0.5 μg L-1, respectively. Unknown signals were soluble organic iodine species (SOI) and quantified by the calibration curve of iodide, but not clearly identified and quantified yet. These analytical methods were all applied to the iodine measurements of marine aerosol samples from the worldwide filed campaigns. The TSI and TII concentrations (medians) in PM2.5 were found to be 240.87 pmol m-3 and 105.37 pmol m-3 at Mace Head, west coast of Ireland, as well as 119.10 pmol m-3 and 97.88 pmol m-3 in the cruise campaign over the North Atlantic Ocean, during June – July 2006. Inorganic iodine, namely iodide and iodate, was the minor iodine fraction in both campaigns, accounting for 7.3% (median) and 5.8% (median) in PM2.5 iodine at Mace Head and over the North Atlantic Ocean, respectively. Iodide concentrations were higher than iodate in most of the samples. In the contrast, more than 90% of TSI was SOI and the SOI concentration was correlated significantly with the iodide concentration. The correlation coefficients (R2) were both higher than 0.5 at Mace Head and in the first leg of the cruise. Size fractionated aerosol samples collected by 5 stage Berner impactor cascade sampler showed similar proportions of inorganic and organic iodine. Significant correlations were obtained in the particle size ranges of 0.25 – 0.71 μm and 0.71 – 2.0 μm between SOI and iodide, and better correlations were found in sunny days. TSI and iodide existed mainly in fine particle size range (< 2.0 μm) and iodate resided in coarse range (2.0 – 10 μm). Aerosol iodine was suggested to be related to the primary iodine release in the tidal zone. Natural meteorological conditions such as solar radiation, raining etc were observed to have influence on the aerosol iodine. During the ship campaign over the North Atlantic Ocean (January – February 2007), the TSI concentrations (medians) ranged 35.14 – 60.63 pmol m-3 among the 5 stages. Likewise, SOI was found to be the most abundant iodine fraction in TSI with a median of 98.6%. Significant correlation also presented between SOI and iodide in the size range of 2.0 – 5.9 μm. Higher iodate concentration was again found in the higher particle size range, similar to that at Mace Head. Airmass transport from the biogenic bloom region and the Antarctic ice front sector was observed to play an important role in aerosol iodine enhancement. The TSI concentrations observed along the 30,000 km long cruise round trip from East Asia to Antarctica during November 2005 – March 2006 were much lower than in the other campaigns, with a median of 6.51 pmol m-3. Approximately 70% of the TSI was SOI on average. The abundances of inorganic iodine including iodine and iodide were less than 30% of TSI. The median value of iodide was 1.49 pmol m-3, which was more than four fold higher than that of iodate (median, 0.28 pmol m-3). Spatial variation indicated highest aerosol iodine appearing in the tropical area. Iodine level was considerably lower in coastal Antarctica with the TSI median of 3.22 pmol m-3. However, airmass transport from the ice front sector was correlated with the enhance TSI level, suggesting the unrevealed source of iodine in the polar region. In addition, significant correlation between SOI and iodide was also shown in this campaign. A global distribution in aerosol was shown in the field campaigns in this work. SOI was verified globally ubiquitous due to the presence in the different sampling locations and its high proportion in TSI in the marine aerosols. The correlations between SOI and iodide were obtained not only in different locations but also in different seasons, implying the possible mechanism of iodide production through SOI decomposition. Nevertheless, future studies are needed for improving the current understanding of iodine chemistry in the MBL (e.g. SOI identification and quantification as well as the update modeling involving organic matters).Iod spielt eine wichtige Rolle beim Abbau von Ozon in der Troposphäre und bei der Bildung neuer Partikel in der maritimen Grenzschicht (Marine Boundary Layer, MBL). Die Quellen, Reaktionswege und Senken für Jod werden mit Hilfe von Laborexperimenten und Feldstudien untersucht. Im Rahmen dieser Arbeit wird hierzu zunächst eine analytische Methode zur Messung von löslichen Jodspezies in maritimen Aerosolproben entwickelt. Anschließend wird diese Methoden verwendet, um in Feldstudien gesammelte Proben zu untersuchen und die Charakteristika der Iodspezies im Aerosol der MBL abzuschätzen. Induktiv gekoppelte Plasma-Massenspektrometrie (Inductive coupled Plasma - Mass Spectrometry, ICP-MS) wurde als Messtechnik für Iod benutzt. Offline Methoden, die zum einen Wasser und zum anderen Tetramethylammoniumhydroxid als Extraktionsmittel benutzen, werden verwendet, um den gesamten löslichen Iodgehalt (total soluble iodine, TSI) und den gesamten unlöslichen Iodgehalt (total insoluble iodine, TII) in den marinen Aerosolproben zu bestimmen. Externe Starndardkalibration und Isotopenverdünnungsanalyse (isotop dilution analysis, IDA) wurden beide benutzt um Iod zu quantifizieren, wobei die Nachweisgrenzen (limits of detection, LODs) 0,1 μg/L für TSI und TII-Messungen betrugen. Online Kopplungen mit der Ionenchromatographie (IC)-ICP-MS und der Gelelektrophorese (GE)-ICP-MS wurden beide für die Speziation von löslichen Iodverbindungen entwickelt. Iodid, Iodat und unbekannte Signale wurden durch diese Methoden nachgewiesen. Iodid und Iodat wurden erfolgreich getrennt und die Nachweisgrenzen betrugen 0,1 μg/L und 0,5 μg/L. Die unbekannten Signale waren lösliche organische Iodspezies (soluble organic iodine species, SOI) und wurden mit der Kalibrationskurve von Iodid quantifiziert, aber bislang nicht klar identifiziert und quantifiziert. Diese analytischen Methoden wurden alle zur Iodspeziesanalytik in maritimen Aerosolproben aus weltweiten Kampagnen benutzt. Die TSI und TII Konzentrationen (Mittelwerte) im PM2,5 lagen im Bereich von 240,87 pmol/m3 und 105,37 pmol/m3 in Mace Head (an der Westküste Irlands) sowie im Bereich von 119,01 pmol/m3 und 97,88 pmol/m3 während einer Schiffkampagne über den nordatlantischen Ozean in der Zeit von Juni bis Juli 2006. Die anorganischen Iodspezies, hauptsächlich Iodid und Iodat, stellten in beiden Kampagnen die kleinere Iodfraktion dar, zusammen etwa 7,3% (Mittelwert) im PM2,5 in Mace Head und 5,8% (Mittelwert) im PM2,5 über dem nordatlantischen Ozean. Die Iodidkonzentrationen waren in den meisten Fällen höher als die von Iodat. Mehr als 90% des TSI waren im Gegensatz dazu SOI und die SOI-Konzentration korrelierte signifikant mit der Iodidkonzentration. Die Korrelationskoeffizienten (R2) waren beide größer als 0,5 in Mace Head und auf dem ersten Teil der Schiffkampagne. Größenfraktionierte Aerosolproben, die mit einem 5-stufigem Berner-Kaskaden-Impaktor gesammelt wurden, zeigten ähnliche Verteilungen der organischen und anorganischen Iodspezies. Signifikante Korrelationen wurden in einem Bereich von 0,25 -0,71 µm und 0,71-2,0 µm zwischen SOI und Iodid erhalten, wobei bessere Korrelationen an sonnigen Tagen gefunden wurden. TSI und Iodid existierten hauptsächlich im Bereich der kleinen Partikel (<2,0 µm), wohingegen sich Iodat überwiegend im „Coarse-mode“ (2,0-10,0 µm) befindet. Das Iodid im Aerosol, so wurde vermutet, sollte mit der Gezeitenzone zusammenhängen. Natürliche meteorologische Bedingungen wie Sonnenstrahlung, Regen etc. besitzen einen Einfluss auf die Iodspezies im Aerosol. Während der Schiffskampagne auf dem Nordatlantischen Ozean (Januar – Februar 2007), lagen die TSI-Konzentrationen (Mittelwerte) zwischen 35,14-60,63 pmol/m3 in den 5 Stufen. Ebenso wurde SOI als die am meisten vorkommende Iodfraktion im TSI mit einem Mittelwert von 98,6% gefunden. Signifikante Korrelationen zeigten sich auch zwischen SOI und Iodid in einem Größenbereich von 2,0 -5,9 µm. Höhere Iodatkonzentrationen wurden wieder in einem Bereich größerer Partikel, ähnlich wie in Mace Head gefunden. Hierbei wurde beobachtet, dass der Luftmassentransport aus der biologischen „bloom region“ und der Antarktischen Eisfront eine wichtige Rolle bei Anreicherung von Iodspezies im Aerosol spielt. Die TSI-Konzentrationen, die während der 30.000km langen Schiffskampagne von Ostasien zur Antarktis und wieder zurück in der Zeit von November bis März 2006 gefunden wurden, waren mit einem Mittelwert von 6,51 pmol/m3 sehr viel kleiner als die Werte in anderen Kampagnen. Ungefähr 70% des TSI waren im Durchschnitt SOI. Die Menge an anorganischem Iodspezies, Iod und Iodid eingeschlossen, betrug weniger als 30%. Dabei war die mittlere Iodidkonzentration (1,49 pmol/m3) mehr als 4mal so hoch wie die mittlere Iodatkonzentration (0,28 pmol/m3). Messungen an verschiedenen Standorten wiesen darauf hin, dass die höchsten Iodkonzentrationen im Aerosol in tropischen Gebieten vorliegen. Die TSI Konzentration war in der Nähe der Antarktischen Küste einem Mittelwert von 3,22 pmol/m3 deutlich niedriger. Dennoch korrelierte der Luftmassentransport aus dem Bereich der Eisfront mit der Zunahme der TSI-Konzentration, was eine unentdeckte Iodquelle in der polaren Region vermuten lässt. Zusätzlich wurde eine signifikante Korrelation zwischen SOI und Iodid in dieser Kampagne gezeigt. Eine globale Verteilung von Iodspezies im Aerosol wurde in den Feldkampagnen dieser Arbeit gezeigt. SOI wurde weltweit an verschiedenen Probennahmeorten nachgewiesen und machte einen großen Anteil der TSI-Konzentration im maritimen Aerosol aus. Die Korrelationen zwischen SOI und Iodid wurden nicht nur für verschieden Orte erhalten, sondern auch in unterschiedlichen Jahreszeiten, was einen möglichen Mechanismus der Iodid-Produktion durch SOI-Zersetzung impliziert. Trotzdem sind auch in Zukunft weitere Studien notwendig, um das aktuelle Verständnis der Iodchemie in der MLB zu verbessern (z.B. SOI –Identifikation und Quantifizierung sowie die Aktualisierung der Modelle, die organische Bestandteile einbeziehen)

Organophosphate Esters in Air, Snow, and Seawater in the North Atlantic and the Arctic

The concentrations of eight organophosphate esters (OPEs) have been investigated in air, snow and seawater samples collected during the 'cruise of ARK-XXVIII/2 from sixth June to third July 2014 across the North Atlantic and the Arctic. The sum of gaseous and particle concentrations (Sigma OPE) ranged from 3S to 343 pg/m(3). The three chkirinated OPEs accounted for 88 +/- 5% of the Sigma OPE. The most abundant OPE was tris(2-chloroethyl) phosphate (TCEP), with concentrations ranging from 30 to 227 pg/m(3), followed by three major OPEs; such as tris(1-chloro,2-propyl) phosphate (TCPP, 0.8 to 82 pg/M-3), tri.'n-butyl phosphate (TnBP, 2 to 19 pg/m(3)), and tri-iso-butyi phosphate (TiBP, 0.3 to 14 pg/m(3)). The LOPE concentrations in snow and seawater ranged from 4356 to 10561 pg/L and from 348 to 8396 pg/L, respectively. The atmospheric particle-bound dry depositions of TCEP ranged from 2 to 12 ng/m(2)/day. The air seawater gas exchange fluxes were dominated by net volatilization from seawater to air for TCEP (mean, 146 239 ng/tri(2)/day), TCPP (mean, 1670 +/- 3031 ng/m(2)/day), TiBP (mean, 537 581 ng/m(2)/day) and TnBP (mean, 230 +/- 254 ng/m(2)/clay). This study highlighted that OPEs are subject to long-range transport via both air and seawater from the European continent and seas to the North Atlantic and the Arctic

Characterisation of volatile organic compounds at hotels in Southern China

In the recent years, there has been a dramatic growth in the development of hotels in Southern China to meet the rapid demand of business and tourism industry. The indoor air quality of the hotels has become an important consideration due to a large workforce that is engaged in this industry. The objective of this study was to characterise the volatile organic compounds (VOCs) found in the indoor air in 13 new hotels in Southern China and assess their possible health impact. A 2-day non-simultaneous sampling was carried out in each of the hotels. Decorating materials, cleansing agents and even local regional pollutants outside the hotels could have a contribution and worsen indoor air quality. Toluene level was as high as 498 μg m -3 in a hotel fitted with lots of plywood products. The highest concentrations of methylene chloride (34 μg m -3) and total carbonyls (517 μg m -3) were detected in a hotel where high VOCs cleansing agents were used in guest rooms. In a hotel located in an industrial centre, acetone concentration of 102 μg m -3 was found. The second highest total VOCs concentration (445 μg m -3) was observed in a newly renovated hotel. Wooden interior fixtures and wall panels were identified as the major sources of VOCs and carbonyls found inside the guest rooms. © The Author(s), 2011.link_to_subscribed_fulltex

Seasonal variations of anhydrosugars in pm2.5 in the pearl river delta region, china

Anhydrosugars including levoglucosan and mannosan are the most effective organic tracers for biomass burning aerosol in the atmosphere. In this study, to investigate the contribution of biomass burning emissions to the aerosol burden in the Pearl River Delta (PRD) region, China, 24-hour integrated PM2.5 samples were collected simultaneously at four locations, (i) Guangzhou (GZ), (ii) Zhaoqing (ZQ) in Guangdong province, (iii) Hok Tsui (HT) and (iv) Hong Kong Polytechnic University (PU) in Hong Kong, in four seasons between 2006 and 2007. Levoglucosan and mannosan, together with water-soluble inorganic ions and water-soluble organic carbon (WSOC), were determined to elucidate the seasonal and spatial variations in biomass burning contributions. The concentrations of levoglucosan and mannosan were on average 82.4 +/- 123 and 5.8 +/- 8.6 ng m(-3), respectively. The WSOC concentrations ranged from 0.2 to 9.4 mu g m(-3), with an average of 2.1 +/- 1.6 mg m(-3). The relative contributions of biomass burning emissions to OC were 33% in QZ, 12% in GZ, 4% at PU and 5% at HT, respectively, estimated by the measured levoglucosan to organic carbon ratio (LG/OC) relative to literature-derived LG/OC values. The contributions from biomass burning emissions were in general 1.7-2.8 times higher in winter than those in other seasons. Further, it was inferred from diagnostic tracer ratios that a significant fraction of biomass burning emissions was derived from burning of hard wood and likely also from field burning of agricultural residues, such as rice straw, in the PRD region. Our results highlight the contributions from biomass/biofuel burning activities on the regional aerosol budget in South China

Reconstructed Light Extinction Coefficients of Fine Particulate Matter in Rural Guangzhou, Southern China

A one-year campaign was conducted to collected PM2.5 samples in the rural area of Guangzhou, the largest megacity in South China, from March 2012 to February 2013. Mass concentration of PM2.5, carbonaceous fractions (i.e., organic carbon (OC) and elemental carbon (EC)) and 6 water-soluble ions were analyzed. Light extinction coefficient (b(ext)) of fine particulate matter was reconstructed using the revised IMPROVE formula at the site. The reconstructed b(ext) was compared with the measured b(ext) converted from visibility. A good correlation was obtained between the two sets of b(ext) with a coefficient of determination (R-2) of 0.61 and a slope of 0.99. The average reconstructed b(ext) in the study was 253.7 +/- 162.9 Mm(-1). The seasonal reconstructed b(ext) was in the order of autumn (319.4 +/- 207.2 Mm(-1)) > winter (269.6 +/- 175.5 Mm(-1)) > summer (219.0 +/- 129.3 Mm(-1)) > spring (193.3 +/- 94.9 Mm(-1)). (NH4)(2)SO4 (AS) made a dominant contribution to the light extinction budget, accounting for 61.3% (155.6 +/- 108.5 Mm(-1)) annually, with highest in autumn (68.0%) and lowest in winter (55.2%). Organic matter (OM) was the second largest contributor accounting for 20.5% (52.2 +/- 42.7 Mm(-1)) with highest in winter (23.4%) and lowest in spring (18.0%). The relationship between reconstructed b(ext) and measured bext was investigated under the influence of seasonality, visibility and PM2.5 concentration. We found that b(ext) could be reconstructed using revised IMPROVE formula in high PM2.5 days (threshold value of similar to 60 mu g m(-3)). On other hand, the performance of formula was unsatisfactory for b(ext) reconstruction of in low PM2.5 days, when meteorological conditions could have significant impact on visibility