Diurnal Variation and Chemical Characteristics of Atmospheric Aerosol Particles and Their Source Fingerprints at Xiamen Bay

This study investigated the diurnal variation of mass concentration and chemical composition of atmospheric aerosol particles sampled at Xiamen Bay, located on the west bank of the Taiwan Strait. Atmospheric PM10 samples were collected at ten particulate matter (PM) sampling sites at Xiamen Bay, including five sites at the Kinmen Islands and five sites in urban Xiamen, at both daytime and nighttime during the regular and intensive sampling periods. Regular sampling was conducted to collect PM10 with high-volume samplers three times a month from April 2009 to April 2010, while intensive sampling was conducted to collect PM2.5 and PM2.5–10 with dichotomous samplers in the spring and winter of 2009 and 2010. This study further selected ten major emission sources (e.g., stone processing, power plants, soil dusts, and biomass burning) at Xiamen Bay to collect fugitive particulate samples which were then resuspended in a self-designed resuspension chamber to collect PM2.5 and PM2.5–10 with two separate dichotomous samplers for further chemical analysis. The results from PM10 sampling indicated that atmospheric aerosol particles tended to be accumulated in Xiamen Bay all year round, but especially in spring and winter. A significant diurnal variation of PM10 was observed, with higher PM10 concentrations in the daytime during the regular sampling periods. The chemical analysis results showed that the major chemical components of PM10 were SO4, NO3, NH4, OC, EC, and crustal elements (Ca, Mg, Fe, and Al), which were usually higher in the daytime than at night at Xiamen Bay. The differences were most pronounced at night, where the concentrations of most anthropogenic elements (Ni, Cu, As, and V) were higher than those in the daytime. The elemental composition of PM emitted from stone processing and the cement industry were dominated by crustal elements, particularly Ca, whereas the profile of top-soil mainly contained Al and Ca. The profiles of industrial sources were dominated by secondary inorganic aerosols and EC. Moreover, construction and road dusts contained large amounts of Fe and Al, while biomass burning released large amounts of K, OC, and SO4.


INTRODUCTION
Xiamen Bay located at the west bank of Taiwan Strait has two major islands, Kinmen and Xiamen Islands, and surrounding coastal region as shown in Fig. 1.In recent years, the rapid development of economy and industry along Xiamen Bay results in serious environmental problems, particularly poor air quality and visibility impairment.Ambient air quality monitoring data shows that a high percentage (4.6-13.2%) of poor air quality (PSI > 100) in Kinmen Island, which is the worst air quality region among seven Air Quality Zones (AQZs) in Taiwan.Unlike Kinmen Islands, the stationary sources in metro Xiamen were approximately twenty times higher than those in Kinmen Islands.Thus, this study also collected resuspended dusts from major industrial sources around Xiamen Bay for further physicochemical analysis of suspended particles.Atmospheric particulates with aerodynamic diameter less than 10 μm (PM 10 ), especially the fine particle fraction (aerodynamic diameter ≤ 2.5 μm), has been found to associate with health problem, such as mortality asthma (Anderson, et al., 1992;Dockery, et al., 1993;Dockery, et al., 1994).As well as the size distribution, the chemical composition of atmospheric particulates can induce health-related effects.Of particular concern is the fact that toxic trace metals, such as lead (Pb), zinc (Zn), arsenic (As), and copper (Cu), are in the form of fine particles with a size distribution equivalent to atmospheric particulates with 1.0 μm or less in diameter Fig. 1.Location of ten PM 10 sampling sites at Xiamen Bay.(Dongarrà et al., 2007;Zhang, 2009;Dongarrà et al., 2010;Lim et al., 2010).Previous investigators suggest that trace metals distribute widely throughout the lung on fine particles could catalyze and enhance the formation of oxidants, which in turn produces tissue damage (Fernández et al., 2002).Previous studies reported that the chemical composition of atmospheric particulates correlates with ambient air quality, particularly the impairment of atmospheric visibility (Yuan et al., 2002;Lee et al., 2005;Yuan et al., 2006).Our recent studies revealed that the main composition of PM 10 are secondary aerosols (SO 4 2-, NO 3 -, and NH 4 + ), crustal elements, and carbons at Xiamen Bay in the seasons of winter and spring (Zhao et al., 2011;Li et al., 2012;Wu et al., 2012).Although several previous studies have been performed on filed measurement of atmospheric PMs and their chemical composition at Xiamen Bay (Wu et al., 2010;Zhao et al., 2011;Li et al., 2012;Wu et al., 2012), there is no study focused on source characterization in terms of elemental content of PM fractions.The chemical composition of PMs emitted from various sources presents their fingerprints and source profiles which can be potentially used for CMB models.The source profiles used for previous study on CMB receptor modeling at Xiamen Bay (Li et al., 2012) were mainly obtained from previous researcher's findings of the chemical composition of PM s emitted from various stationary and mobile sources including industrial and automobile combustion processes.However, the source profiles of local fugitive sources from industrial and agriculture activities such as road dusts, construction area, farmland dusts, cement industry, stone processing industry, ceramic tile industry, biomass burning were limited and incomplete.Therefore, the aim of this study is to collect and chemically characterize PM 10 emitted from major fugitive sources in the study area, which can be further applied for the source apportionment of PM 10 by using CMB model (Ho et al., 2003;Mugica et al., 2009).

Sampling Protocol of Atmospheric Aerosol Particles
In this study, ambient air quality monitoring were conducted at ten particulate matter sampling sites at Xiamen Bay, including five sites at Kinmen Islands (Lieyu, Jinding, Jinsa, Guchung, and Bortsuen) and five sites at metro Xiamen (Xiamen, Daderng, Anhai, Jinjing, and Xiangzhi) as shown in Fig. 1  metropolitan area would influence the ambient air quality at site XM during the northeastern monsoon periods, whereas air pollutants emitted from Houshi power plant could be transported to the downwind sites.Site DD located at an island of Dadeng in northern Xiamen is a tourism township with a cargo harbor.Kinmen Islands are recognized as a national park and its local emission sources are well controlled.Thus, sites LY, JD, JS, GC, and BT in Kinmen Islands are more likely to be influenced by regional air pollution, especially from the upwind northern and northeastern industrial areas in Jinjiang River and Jinjing during the northeastern monsoon seasons.Particulate matter sampling was conducted in the daytime (8:00-17:00) and at nighttime (17:00-8:00), for both regular and intensive sampling.Regular sampling was conducted to collect PM 10 with high-volume samplers trice a month from April 2009 to April 2010, while intensive sampling was conducted to collect fine (PM 2.5 ) and coarse (PM 2.5-10 ) particles with dichotomous samplers for consecutive 5 days in the spring and winter of 2009-2010.After sampling, the physicochemical properties of PM, including mass concentrations, water-soluble ionic species, metallic elements, and carbonaceous contents were further analyzed.

Sampling of Resuspension Dusts
In recent years, air pollution of Xiamen Bay (including Kinmen and Xiamen Islands) has become one of the most serious environmental problems accompanying with rapid urbanization and economic development.In order to understand the physicochemical fingerprints of particulate matter emitted from various PM emission sources at Xiamen Bay, this study selected ten major emission sources (tile kiln stoves, power plants, soil dusts, biomass burning, and etc.) at Xiamen Bay to collect their emitted particulate samples which were initially sieved with Tyler 400 mesh (d p < 38 μm) to obtain dusts of 5 g.As shown in Table 2, descriptions of major PM fugitive sources were selected in this study surrounding the Xiamen Bay.Two dichotomous samplers in the resuspension chamber were used to collect PM 2.5 and PM 2.5-10 from the resuspended dusts obtained from major fugitive PM sources.The sampling of PM in the chamber continued for at least 30 mins to ensure adequate PM deposition on the filters.In addition to industrial sources, fugitive sources including top-soils, coal piles, and coal ashes were further tested.The soil and ash samples were stored in high-density polyethylene (HDPE) bottles after passing through sieves (less than 38 μm mesh size), which were then homogenized manually and resuspended to the air for PM sampling and chemical analysis.The resuspended PM 2.5 and PM 2.5-10 samples were collected by two dichotomous samplers using teflon and quartz filters, respectively.This study collected ten major types of industrial dusts in the region surrounding Xiamen Bay and brought back to the Air Pollution Laboratory in the Institute of Environmental Engineering at National Sun Yat-sen University, and then resuspended the dusts in a self-designed resuspension chamber for sampling PM 2.5 and PM 2.5-10 with two separate dichotomous samplers (Fig. 2).After sampling, the chemical composition of atmospheric particulates, including watersoluble ions, metallic elements, and carbonaceous contents were further analyzed (Yatkin and Bayram, 2008).This study finally established the database of particulates emitted from various industrial sources and then compare their physicochemical fingerprints at Xiamen Bay.

Chemical Analysis
After sampling, quartz fiber filters were temporarily stored at 4°C and then transported back to the Air Pollution Laboratory in the Institute of Environmental Engineering at National Sun Yat-Sen University for further conditioning, weighing, and chemical analysis.All PM 10 sampling filters collected by high-volume samplers were cut into four identical parts.One part of the quartz fiber filter was analyzed for water-soluble ionic species.The filter analyzed for ionic species was put inside a 15-mL PE bottle for each sample.Distilled de-ionized water (D.I.H 2 O) was added into each bottle and vibrated in an ultrasonic process for approximately 60 mins.An ion chromatographer (DIONEX, Model DX-120) was used to analyze the concentration of major anions (F -, Cl -, SO 4 2-, and NO 3 -) and cations (NH 4 + , K + , Na + , Ca 2+ and Mg 2+ ).
Another part of the quartz fiber filter analyzed for metallic elements was initially digested in a 20 mL mixed acid solution (HNO 3 :HClO 3 = 3:7) at 150-200°C for 2 hrs, and then diluted to 25 ml with distilled de-ionized water (D.I.H 2 O).During the digestion, D.I. H 2 O was added to the residual solution two or more times in order to eliminate the acid content of the digestion solution.The metallic elements of the PM 10 , including Na, Ca, Al, Fe, Mg, K, Zn, Cr, Ti, Mn, Ba, Sr, Ni, Pb, and Cu, were then analyzed with an  inductively coupled plasma-atomic emission spectrometer, ICP-AES (Perkin Elmer, Model Optima 2000DV).Two parts of the quartz fiber filters were further used to measure the carbonaceous contents of PM 10 .The carbonaceous contents, including elemental, organic, and total carbons (OC, EC, and TC), were measured with an elemental analyzer (Carlo Erba, Model 1108).Before sampling, all quartz fiber filters were pre-heated to 900°C for 1.5 hr to expel potential carbon impurities from the fiber filters.The preheating procedure could minimize the background carbon in the quartz fiber filters and matrix, which might cause interference with the analytical results, leading to an overestimation of the carbonaceous content of PM 10 .The elemental analyzer (EA) was operated using the procedure of oxidation at 1020°C and that of reduction at 500°C, with continuous heating for 15 mins.Additionally, one-eighth of the quartz fiber filters was heated in advance by hot nitrogen gas at 340-345°C for at least 30 mins to expel the organic carbon (OC) fraction, after which the amount of elemental carbon (EC) was determined.Another one-eighth of the quartz fiber filter was analyzed without heating to determine total carbon (TC).The amount of OC was then estimated by subtracting EC from TC.

Quality Assurance and Quality Control
The quality assurance and quality control (QA/QC) for both PM sampling and chemical analysis were conducted in this study.Prior to conducting PM 10 sampling, the flow rate of each PM 10 sampler was carefully calibrated with an orifice calibrator.Quartz fiber filters were then carefully handled and placed on the PM 10 samplers to prevent potential cracking during the sampling procedure.After sampling, aluminum foil was used to fold the quartz fiber filters, which were then temporarily stored at 4°C and transported back for further chemical analysis.The sampling and analytical procedure was similar to that described in various previous studies (Cheng and Tsai, 2000;Yuan et al., 2006;Tsai et al., 2008;Tsai et al., 2010Tsai et al., , 2011Tsai et al., , 2012)).Both field and transportation blanks were undertaken for PM 10 sampling, while reagent and filter blanks were applied for chemical analysis.The determination coefficient (R 2 ) of the calibration curve for each chemical species was required to be higher than 0.995.Background contamination was routinely monitored by using operational blanks (unexposed filters), that were proceeded simultaneously with field samples.The background interference was found to be insignificant and can thus be ignored in this study.At least 10% of the samples were analyzed by spiking with a known amount of metallic and ionic species to determine their recovery efficiencies.

Transportation Routes of Air Masses
The mass concentrations measured at the stations varied with seasons and wind directions, higher values were recorded in winter (northeasterly wind) than in summer (southwesterly wind).In order to trace the air mass, backward trajectories from a receptor site are commonly used to identify air pollution source regions and specific sources (Man and Shih, 2001;Kong et al., 2010;Zhu et al., 2011).The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) is a widely used model that plots the trajectory of a single air parcel from a specific location and height above ground over a period of time.The 96-hour backward trajectories of air parcels that arrived at Xiamen Bay on four different days.The level of atmospheric PM 10 was affected by meteorological condition, thus PM 10 concentrations in spring and winter was much higher than those in fall and summer.Results obtained from backward trajectories showed that the concentrations of PM 10 blown from the north were generally higher than those from the south.

Mass Concentration of PM 10 and Mass Ratio of Fine and Coarse Particles
The regular sampling of PM 10 concentrations at ten sampling sites at Xiamen Bay was conducted from April 2010 to April 2011.As illustrated in Fig. 3, the highest PM 10 concentrations in the daytime were in spring (XM: 144.42 μg/m 3 ), summer (AH: 141.74 μg/m 3 ), fall (AH: 150.08 μg/m 3 ), and winter (JJ: 161.31 μg/m 3 ); and the highest PM 10 concentrations at nighttime were in spring (AH: 102.30μg/m 3 ), summer (LY: 106.70 μg/m 3 ), winter (AH: 161.20 μg/m 3 ), and fall (AH: 161.87 μg/m 3 ), respectively, at Xiamen Bay.The daytime and nighttime wind roses are illustrated in Fig. 4. Fig. 4 illustrates the prevailing wind direction and speed both daytime and nighttime at Xiamen Bay.It shows that the prevailing winds were respectively blown from the northeastern monsoons (from fall to early spring) and the southwestern monsoons (from late spring to summer).The prevailing winds varied frequently from the northeastern monsoons to the southwestern monsoons and vice versa during the sampling periods of this study.As illustrated in Fig. 3 and Fig. 4, the wind directions were commonly stable, but the PM 10 concentration generally varied relatively frequently in the daytime and at nighttime.The differences of PM 10 concentration in the daytime and at nighttime suggested that local fugitive emissions dominated PM 10 concentration level in summer and fall.However, in winter and spring, the northeastern monsoons brought highly polluted air masses from the far urban and industrial areas to the downwind sites.It thus caused a significant increase of PM 10 concentration at Xiamen Bay due to long-range transportation.Among ten sampling sites, the average concentrations of 24-hr PM 10 frequently violated the ambient air quality standard of 125 μg/m 3 in winter and spring.The highest 24-hr PM 10 concentrations mostly occurred in winter and spring, while the lowest generally occurred in summer.The ratio of PM 10 concentrations in the daytime to nighttime (D/N) were generally higher than unity at Xiamen Bay.The average ratio of PM 10 concentrations in the daytime to those at nighttime (D/N) were 1.30, 1.44, 1.48, and 1.52, respectively.Additionally, the average D/N ratio of PM 10 concentrations were 1.54 at Kinmen Islands, which were generally higher than those (1.30) in metro Xiamen.Seven sampling sites (A1, A2, B1, B2, B3, B4 and B5) located at the center of Xiamen Bay had relatively higher PM 10 concentration than other three sampling sites (A3, A4 and A5) located outside the Xiamen Bay.Our previous study concluded that a superimposition phenomenon was regularly observed during the air pollution episodes at Xiamen Bay.This study further revealed that local emissions from the Xiamen Bay were generally more significant than long-rang transportation from the Northeastern Monsoons.Besides, high PM 10 concentrations might also result from more human activities in the daytime than those at nighttime.Regular PM 10 sampling results showed a significant diurnal variation with higher PM 10 concentrations in the daytime compared to those at nighttime in all seasons.However, an opposite trend was observed at site DD in spring and fall.Results from PM sampling indicated that atmospheric particulates had a tendency to accumulate at Xiamen Bay all year round.A seasonal variation of PM 10 was commonly  The northern winds could transport atmospheric particles from the upwind emission sources to the downwind sites at Kinmen Islands, resulting in a significant increase of atmospheric PM 10 concentrations at Kinmen Islands.During the intensive sampling periods, both PM 2.5 and PM 2.5-10 were simultaneously sampled at site JD and JS with dichotomous samplers.The mass ratios of fine and coarse particles are presented in Table 3.During the intensive sampling period in winter, the highest PM 10 and PM 2.5 concentration were 182.77 and 107.30μg/m 3 in the daytime, and were 207.12 and 165.19 μg/m 3 at nighttime, respectively.The mass ratios of PM 2.5 to PM 10 (PM 2.5 /PM 10 ) ranged from 26.32 to 77.22% and 29.47 to 79.75% in the daytime and at nighttime, respectively.Generally speaking, fine particles dominated in the warm sector ahead, while coarse particles dominated in the frontal passage at Xiamen Bay.In this study, high PM 10 concentrations were generally dominant in coarse particle mode.The results indicated that high PM 10 concentrations were mainly attributed to local upwind fugitive sources (i.e., industrial areas along the northern coast of Xiamen Bay) of the sampling sites during the intensive sampling periods.
Particularly, the northern winds transported atmospheric particles from the upwind fugitive sources to the downwind Kinmen Islands.According to previous study at Xiamen Bay, the local emissions at Xiamen Bay were as important as longrange transportation from the Northeastern Monsoons, and thus a superimposition phenomenon was regularly observed during the air pollution episodes at Xiamen Bay (Li et al., 2012).As shown in Table 3, both high PM 2.5 /PM 10 ratios and high PM 2.5 concentrations were generally observed at high PM episodes whenas the winds were prevailingly blown from the northeast.This phenomenon was probably caused by long-rang transportation from the northern China.Besides, low PM 2.5 /PM 10 ratios and high PM 2.5-10 concentrations  4, the fugitive dusts except biomass burning were dominant by coarse particles (PM 2.5-10 ).

Chemical Properties of PM 10
This study revealed that the concentration of ionic species in the daytime were generally higher than those at nighttime.Secondary inorganic aerosols (i.e., SO 4 2-, NO 3 -, and NH 4 + ) was abundant on PM 10 , accounting for about 85% of total ionic species (Fig. 5), and the most possible chemical species of PM 10 were secondary inorganic aerosols (i.e., ammonium sulfate ((NH 4 ) 2 SO 4 ) and ammonium nitrate (NH 4 NO 3 )) as well as organic carbons in this study.The percentage of total ionic species accounted for approximately 48% of PM 10 in this study.
The concentrations of crustal elements (e.g., Ca, Mg, Fe, and Al) were generally higher than anthropogenic elements (e.g., Zn and Pb) as shown in Fig. 6.Most of the time, the concentrations of metallic elements in the daytime were generally higher than those at nighttime.However, in spring and summer, some metals (Pb, Cu, Zn, As) at nighttime were higher than those in daytime.In fall and winter, the concentrations of metals in the daytime were generally higher than those at nighttime.The highest metallic concentrations were appeared at site DD, suggesting that anthropogenic metallic elements of PM 10 were highly affected by the surrounding emission sources at site DD.Pollution emissions from municipal and industrial incinerators as well as heavy vessels are very heavy around Xiamen Bay, resulting in high Zn and Pb emissions.High Pb emissions may came from incinerator, leaded-gasoline combustion.High Pb concentrations could be contributed form dense heavy vessels which were quite busy around Xiamen Bay.The  et al., 1994).In addition, there are many stone processing plants located at the north of site JJ.Moreover, other anthropogenic metallic elements could be also transported to Xiamen Bay from the southeastern coast of China through long-range transportation by the Northeastern Monsoons.The metallic concentrations of PM 10 in the daytime were generally higher than those in the nighttime.The daytime and nighttime PM 10 concentration ratios (D/N) for Mg, K, Ca, Cr, Mn, Fe, Zn, Al, Cu, As, and V were in the same order of magnitude, however, the D/N ratios of Cd, Pb, Ni, and Ti in spring and summer varied even higher than an order of magnitude, indicating that the emission sources of PM were different in the daytime and at nighttime.The carbonaceous contents of PM 10 sampled at Xiamen Bay are illustrated in Fig. 7. Elemental carbon (EC), which has a chemical structure similar to impure graphite, originated primarily from direct emissions of fuel combustion.Organic carbon (OC) is emitted from primary anthropogenic sources and secondary organic aerosols formed by chemical reactions in the atmosphere.In this study, the OC concentrations of PM 10 were always higher than EC for all seasons at each sampling site.The average OC/EC ratios of PM 10 ranged from 1.27 to 1.77.It indicated that OC was the major species of carbonaceous contents of PM 10 at Xiamen Bay.

Physicochemical Fingerprints of Atmospheric Particulates Emitted from Various Sources at Xiamen Bay
This study revealed that the mass ratio of PM 2.5 and PM 10 (PM 2.5 /PM 10 ) was 89.83% for biomass burning, and PM 2.5 /PM 10 for other industrial sources were 14.12-37.40%(Table 4).The results showed that all industrial dusts except for biomass burning were dominant in coarse particles (PM 2.5-10 ), while biomass burning was dominant in fine particles (PM 2.5 ).Fig. 8 illustrates the ionic species, metallic elements, and carbonaceous contents of various industrial sources.
The fingerprints of stone processing industry were Ca, Al, and Fe.Cement industry was abundant of Ca, SO 4 2-, and K + .Ceramic industry was abundant of Al, K, Mg.Ceramic tile industry was abundant of Al, Fe, and Ca.Construction dusts were abundant of Fe, Al, and NO 3 -.Farmland dusts were abundant of Fe, Al, and NH 4 + .Road dusts were abundant of Al, Fe, and Zn.Biomass burning was abundant of K, OC, and SO 4 2-.Coal was abundant of EC, Al, and Fe.Coal ash was abundant of Al, Ca, and NO 3 -.Overall, the watersoluble ionic components were dominated in secondary inorganic aerosols (SO 4 2-, NO 3 -, and NH 4 + ), but oceanic materials (Na + and Cl -) were also observed in the industrial dusts.Metallic elements were dominant in Ca, Al, Mg, and K, while the power plants and road dusts contained As, Cr, and other trace toxics.It suggested that the resuspended  nighttime, respectively.The average concentrations of 24hr PM 10 were 93.67 ± 33.78 and 76.20 ± 41.61 μg/m 3 in the air trajectories of SWM in the daytime and at nighttime, respectively.The average PM 10 concentrations in the air trajectories of CC were generally the highest, while the lowest occurred in the air trajectories of SWM.The results indicated that the level of atmospheric PM 10 was highly influenced by meteorological condition.The PM 10 concentrations observed in spring and winter were generally higher than those in fall and summer.Results from backward trajectories showed that the concentrations of PM 10 blown from the north were much higher than those from the south.The air trajectories of CMC and CC at Xiamen Bay were dominated by the Northeastern Monsoons, which blew air pollutants from the southeastern coast of China to the Xiamen Bay, causing a significant increase in the concentration of atmospheric particle at Kinmen Islands.The air trajectories of SEM were dominated by the Southwest Monsoons blowing from the South China Sea, resulting in the lowest PM 10 concentration at Kinmen Islands.

CONCLUSIONS
The average concentrations of 24-hr PM 10 frequently violated the ambient air quality standard of 125 μg/m 3 in winter and spring at Xiamen Bay.The highest 24-hr PM 10 concentrations mostly occurred in winter and spring, while the lowest generally occurred in summer.The ratio of PM 10 concentrations in the daytime to those at nighttime (D/N) were generally higher than unity in summer and fall, indicating that PM 10 had a tendency to accumulate at Xiamen Bay in the daytime than those at nighttime.Results from PM sampling indicated that atmospheric particulates had a tendency to accumulate at Xiamen Bay all year round.A seasonal variation of PM 10 was commonly observed with higher PM 10 concentration occurred in spring and winter.Secondary inorganic aerosols (i.e., SO 4 2-, NO 3 -, and NH 4 + ) was abundant on PM 10 , accounting for about 85% of total ionic species and the percentage of total ionic species were accounting for about 48% of PM 10 , suggesting that the most possible chemical compositions of ammonium sulfate ((NH 4 ) 2 SO 4 ) and ammonium nitrate (NH 4 NO 3 ).The concentrations of crustal elements (e.g., Ca, Mg, Fe, and Al) were generally higher than anthropogenic elements (e.g., Zn and Pb).In spring and summer, some metals (e.g., Pb, Cu, Zn, As) at nighttime were higher than those in the daytime.In fall and winter, the concentrations of metals in the daytime were generally higher than those at nighttime.The average OC/EC ratios of PM 10 ranged from 1.27 to 1.77, indicating that OC was the major species of carbonaceous contents of PM 10 at Xiamen Bay.The physicochemical fingerprints of atmospheric particulates emitted from various sources at Xiamen Bay showed that all industrial dusts except for biomass burning were dominant in coarse particles (PM 2.5-10 ), while biomass burning was dominant in fine particles (PM 2.5 ).According to transportation routes of air masses observed at Kinmen Islands, the mass concentrations of PM 10 associated with the SWM type trajectories were the lowest among the continental types as they were diluted by the marine air along the coast of South China Sea.PM 10 concentrations associated with the CMC type trajectory were the highest in three types of trajectories.CMC trajectories were originated from the hundreds of kilometers away from the Xiamen Bay.

Fig. 3 .
Fig. 3. Variation of PM 10 concentration during the sampling periods at Xiamen Bay.

Fig. 7 .
Fig. 7. Variation of EC and OC of PM 10 during the sampling periods.

Fig. 8 .Fig. 9 .Fig. 10 .
Fig. 8.Chemical fingerprints of particulates emitted from various sources at Xiamen Bay.dusts consisted of anthropogenic metallic elements emitted from industrial sources adjacent to the Xiamen Bay.The mass ratios of Fe and Al (Fe/Al) for ceramics and ceramic tile industries were in the range of 0.20-0.26which were lower than Taylor's Fe/Al ratios of crustal materials.Transportation Routes of Air Masses Observed at Kinmen IslandsAir masses arriving Kinmen islands included three typical

Table 1 .
and Table1.Sampling sites XM and JJ located in the downtown Xiamen and Jinjing are next to a street and likely to be influenced by direct emissions from vehicular exhausts and textile industries.Air pollutants from Zhangzhou Harbor, Xiamen Harbor, Songyu power plant and Xiamen General information of particulate matter sampling sites located at Xiamen Bay.

Table 2 .
Descriptions of major fugitive PM sources surrounding the Xiamen Bay.

Table 3 .
Mass ratio of fine and coarse particles during the intensive sampling periods.

Table 4 .
Physical characteristics of particulates emitted from various sources at Xiamen Bay.Pb is the metallic marker emitted from oil burning of heavy vessels.The concentrations of Ca and Fe at metro Xiamen in the rural open lands and construction sites were higher than those at other regions.Al and Ca are the main metallic elements in the earth's crust and particles emitted from the cement industry, and the wind-blown dusts and frictional works from construction sites where increased the atmospheric loading of dust particles (Huang