Qi Yuan

Airborne particulate polycyclic aromatic hydrocarbon (PAH) pollution in a background site in the North China Plain: Concentration, size distribution, toxicity and sources

The size-fractionated characteristics of particulate polycyclic aromatic hydrocarbons (PAHs) were studied from January 2011 to October 2011 using a Micro-orifice Uniform Deposit Impactor (MOUDI) at the Yellow River Delta National Nature Reserve (YRDNNR), a background site located in the North China Plain. The average annual concentration of total PAHs in the YRDNNR (18.95 ± 16.51 ng/m(3)) was lower than that in the urban areas of China; however, it was much higher than that in other rural or remote sites in developed countries. The dominant PAHs, which were found in each season, were fluorene (5.93%-26.80%), phenanthrene (8.17%-26.52%), fluoranthene (15.23%-27.12%) and pyrene (9.23%-16.31%). A bimodal distribution was found for 3-ring PAHs with peaks at approximately 1.0-1.8 μm and 3.2-5.6 μm; however, 4-6 ring PAHs followed a nearly unimodal distribution, with the highest peak in the 1.0-1.8 μm range. The mass median diameter (MMD) values for the total PAHs averaged 1.404, 1.467, 1.218 and 0.931 μm in spring, summer, autumn and winter, respectively. The toxicity analysis indicated that the carcinogenic potency of particulate PAHs existed primarily in the <1.8 μm size range. Diagnostic ratios and PCA analysis indicated that the PAHs in aerosol particles were mainly derived from coal combustion. In addition, back-trajectory calculations demonstrated that atmospheric PAHs were produced primarily by local anthropogenic sources.

Sources apportionment of PM2.5 in a background site in the North China Plain

To better understand the sources and potential source regions of PM2.5, a field study was conducted from January 2011 to November 2011 at a background site, the Yellow River Delta National Nature Reserve (YRDNNR) in the North China Plain. Positive matrix factorisation (PMF) analysis and a potential source contribution function (PSCF) model were used to assess the data, which showed that YRDNNR experienced serious air pollution. Concentrations of PM2.5 at YRDNNR were 71.2, 92.7, 97.1 and 62.5 μg m(-3) in spring, summer, autumn and winter, respectively, with 66.0% of the daily samples exhibiting higher concentrations of PM2.5 than the national air quality standard. PM2.5 mass closure showed remarkable seasonal variations. Sulphate, nitrate and ammonium were the dominant fractions of PM2.5 in summer (58.0%), whereas PM2.5 was characterized by a high load of organic aerosols (40.2%) in winter. PMF analysis indicated that secondary sulphate and nitrate (54.3%), biomass burning (15.8%), industry (10.7%), crustal matter (8.3%), vehicles (5.2%) and copper smelting (4.9%) were important sources of PM2.5 at YRDNNR on an annual average. The source of secondary sulphate and nitrate was probably industrial coal combustion. PSCF analysis indicated a significant regional impact on PM2.5 at YRDNNR all year round. Local emission may be non-negligible at YRDNNR in summer. The results of the present study provide a scientific basis for the development of PM2.5 control strategies on a regional scale.

Trace metals in atmospheric fine particles in one industrial urban city: Spatial variations, sources, and health implications

Trace metals in PM2.5 were measured at one industrial site and one urban site during September, 2010 in Jinan, eastern China. Individual aerosol particles and PM2.5 samples were collected concurrently at both sites. Mass concentrations of eleven trace metals (i.e., Al, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Ba, and Pb) and one metalloid (i.e., As) were measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The result shows that mass concentrations of PM2.5 (130 microg/m3) and trace metals (4.03 microg/m3) at the industrial site were 1.3 times and 1.7 times higher than those at the urban site, respectively, indicating that industrial activities nearby the city can emit trace metals into the surrounding atmosphere. Fe concentrations were the highest among all the measured trace metals at both sites, with concentrations of 1.04 microg/m 3 at the urban site and 2.41 microg/m3 at the industrial site, respectively. In addition, Pb showed the highest enrichment factors at both sites, suggesting the emissions from anthropogenic activities existed around the city. Correlation coefficient analysis and principal component analysis revealed that Cu, Fe, Mn, Pb, and Zn were originated from vehicular traffic and industrial emissions at both sites; As, Cr, and part of Pb from coal-fired power plant; Ba and Ti from natural soil. Based on the transmission electron microscopy analysis, we found that most of the trace metals were internally mixed with secondary sulfate/organic particles. These internally mixed trace metals in the urban air may have different toxic abilities compared with externally mixed trace metals.

Mixing state and hygroscopicity of dust and haze particles before leaving Asian continent

Pollutants during haze and Asian dust storms are transported out of the Asian continent, affecting the regional climate and the hydrological and biogeochemical cycles. Understanding the physicochemical properties of aerosol particles is essential to quantify their impacts. In order to determine physicochemical properties of aerosols before leaving the Asian continent, we carried out a field campaign from 14 April to 2 May 2011 at a background site in the path of Asian dust and haze outflows. We measured concentrations of gaseous pollutants (SO2, NO2, NO, O3, and CO), black carbon (BC), and particle number in situ and collected airborne particles for microscopic analysis. Pollutant concentrations (BC, 4u2009µgu2009m−3; CO, 808u2009ppb; SO2, 24u2009ppb; NO2, 37u2009ppb) were highest during haze periods, except for PM2.5 mass, which was highest (162u2009µgu2009m−3) during a dust storm. Seventy-one percent of haze particles were coated with organic films and 32% were internal mixtures of sulfates and refractory particles (e.g., soot, metal/fly ash, and mineral). Seventy-nine percent of haze particles have deliquescence relative humidity at 68–70%. During a dust storm, soot particles were observed among dust particles. Most dust particles were hydrophobic, and no Ca(NO3)2 was observed in dust particles collected during the dust storms, but up to 32% of dust particles were found to be coated with Ca(NO3)2 after the main dust storm moved out of the sampling area. These results indicated that both natural and anthropogenic aerosol particles in Asian outflow can undergo significant physicochemical processes before leaving the Asian continent.

Temporal variations, acidity, and transport patterns of PM2.5 ionic components at a background site in the Yellow River Delta, China

To better understand the pollution characteristics and potential sources of PM2.5 ionic components at the Yellow River Delta (YRD), a semicontinuous measurement was conducted to observe water-soluble ions in PM2.5 at a nature reserve in Dongying of Shandong province, China, in 2011. The results showed that SO42−, NO3−, and NH4+ were the dominant ionic species (constituting 93xa0% of the total ionic mass) with their annual average concentrations of 22.48, 12.77, and 11.21xa0μg/m3, respectively. These three ion concentrations were generally lower than those observed in major cities in China but higher than those in other rural and nature reserve sites. Ion concentrations exhibited large seasonal variations, and maximum values were observed in summer. SO42− concentration presented a daytime peak in summer, autumn, and winter, while in spring, a relative flat diurnal cycle was observed. NO3− concentration changed with that of SO42− during most of measurement period. Transport from surrounding areas contributed to the diurnal cycle of secondary ions. In addition, photochemical reaction and thermodynamic equilibrium played important roles on the diurnal variation of SO42− and NO3−, respectively. The aerosol at the YRD was weakly acidic, and it was most acidic in winter. A cluster analysis showed that fine particle pollution at the YRD was mainly affected by southwest local emissions and northern middle- to long-distance transport.

Haze particles over a coal‐burning region in the China Loess Plateau in winter: Three flight missions in December 2010

[1]xa0Heavy haze frequently occurs in winter over a coal-burning region, the Taiyuan Basin, in the eastern China Loess Plateau, which is the upstream area of the North China Plain. We participated in three research flights to collect aerosol particles and to monitor SO2concentration in hazes from the ground (780xa0m asl) up to ∼4000xa0m during 17–18 December, 2010. Meteorological records reveal that the whole haze column (ground to 4000xa0m) was stable and could be further divided into three sub-layers depending on the sampling altitude, which are characterized by two shifts of the lapse rate of virtual potential temperature and water vapor mixing ratio: Layer-1, surface to 1500xa0m; Layer-2, 1500xa0∼xa03000xa0m on 17 December, and 1500xa0∼xa02500xa0m on 18 December; Layer-3, above 3000xa0m on 17 December and above 2500xa0m on 18 December. SO2concentration was 16–116xa0ppb with an average of 58xa0ppb in the Layer-1, 2–45xa0ppb with an average of 10xa0ppb in the Layer-2, and 1–10xa0ppb with an average of 4xa0ppb in the Layer-3. The accumulation of SO2in the Layer-1 was due to the stable meteorological conditions and the strong anthropogenic emissions in addition to the possible valley topography. Analyses of the collected particles using a transmission electron microscope revealed the dominance of organic particles and fly ash in the Layer-1 and Layer-2 and sulfate particles in the Layer-3. The organic aerosols frequently contained certain amounts of Si and Cl. Fly ash particles consisted of O and Si with minor Fe, Mn, Zn, Ti, Pb, As, Co, and Cr. These two types of aerosol particles are typically emitted from coal burning. These results indicate that the haze particles were characterized in principle by aerosols from primary emissions of coal burning, which are different from those over the North China Plain where secondary sulfate particles are the dominant component.

Particle size distributions, PM 2.5 concentrations and water-soluble inorganic ions in different public indoor environments: a case study in Jinan, China

In this study, we collected particles with aerodynamic diameter ⩽2.5 μm (PM2.5) from three different public indoor places (a supermarket, a commercial office, and a university dining hall) in Jinan, a medium-sized city located in northern China. Water-soluble inorganic ions of PM2.5 and particle size distributions were also measured. Both indoor and outdoor PM2.5 levels (102.3–143.8 μg·m−3 and 160.2–301.3 μg·m−3, respectively) were substantially higher than the value recommended by the World Health Organization (25 μg·m−3), and outdoor sources were found to be the major contributors to indoor pollutants. Diurnal particle number size distributions were different, while the maximum volume concentrations all appeared to be approximately 300 nm in the three indoor locations. Concentrations of indoor and outdoor PM2.5 were shown to exhibit the same variation trends for the supermarket and dining hall. For the office, PM2.5 concentrations during nighttime were observed to decrease sharply. Among others, SO42−, NH4+ and NO3− were found to be the dominant water-soluble ions of both indoor and outdoor particles. Concentrations of NO3− in the supermarket and office during the daytime were observed to decrease sharply, which might be attributed to the fact that the indoor temperature was much higher than the outdoor temperature. In addition, domestic activities such as cleaning, water usage, cooking, and smoking also played roles in degraded indoor air quality. However, the results obtained here might be negatively impacted by the small number of samples and short sampling durations.

Particle physical characterisation in the Yellow River Delta of Eastern China: number size distribution and new particle formation

Particle number concentration was measured in 2011 in the Yellow River Delta (YRD) of eastern China. The objectives were to study the number size distribution characteristics of ambient aerosols and the meteorological effects on the particle physical characterisation, in addition to investigating the new particle formation (NPF) events in the Yellow River Delta. The particle formation rates and growth rates of the newborn particles were evaluated to identify the new particle formation events. The annual median total number concentration (5–10,000xa0nm) was 10,349xa0cm−3, with a maximum concentration in autumn and lowest in winter. A higher number concentration was observed for Aitken mode particles than for accumulation and nucleation mode particles. Higher temperature and lower humidity could favour the homogeneous nucleation. With increasing wind speed, the Aitken and accumulation mode particle numbers decreased obviously, and the particle sizes were reduced. Higher particle number concentrations were associated with southeast local air masses which passed from polluted area, and smaller diameter peaks were associated with northern air masses. In total, 26 new particle formation events were recorded during the 120xa0days of measurements, and this frequency was slightly lower than that observed in other cities in China. The mean growth and formation rates were calculated as 5.3xa0nmxa0h−1 and 6.6xa0cm−3xa0s−1, respectively. High SO2 and O3 concentrations might have contributed to the increase in nucleation mode particles in the NPF events.