Aerosol and Air Quality Research
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社團法人台灣氣膠研究學會,正常發行
選擇卷期
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The sources and characteristics of particulate matter (PM) were determined in a modern underground chrome mine in Finland. Measurements were conducted at five locations in the mine: the maintenance area, blasting area, ore pit dumping area, crushing station and conveyor belt. The measurement set-up consisted of a Soot Particle Aerosol Mass Spectrometer (SP-AMS) for the particles' chemical composition; an Electrical Low Pressure Impactor, Nano Scanning Mobility Particle Sizer and Optical Particle Counter for the particle number and mass size distribution; and an Aethalometer for black carbon (BC). The particle number and mass concentration depended strongly on the measurement location and period. The PM_(10) and the total number concentrations varied from 22 to 1100 μg m^(-3) and 1.7 × 10^3 to 2.3 × 10^5 # cm^(-3), respectively, in the mine. In terms of the composition, the sub-micrometer particles (PM_1) consisted mostly of organic matter and BC, but at the blasting site, the fraction of sulfate was also significant. The SP-AMS data was analyzed with Positive Matrix Factorization (PMF) to identify and quantify the main sources of PM_1 in the mine. Based on the PMF analysis, the PM_1 originated mostly from diesel engines (35-84%) and blasting (7-60%). The impact of blasting on air quality in mines may become more pronounced in the future as the emissions from diesel engines decrease due to alternative fuels and better engine and after-treatment technologies.
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Water-soluble organic compounds are important constituents of atmospheric aerosols and have been recognized as unique fingerprints to identify atmospheric processes. Fine aerosol samples (PM_(2.5)) were collected at Ambikapur (23.1°N and 83.2°E) in eastern central India from March to June 2017. The samples were analyzed for water-soluble dicarboxylic acids (C_2-C_(12)), glyoxylic acid (ωC_2), glyoxal (Gly), methylglyoxal (MeGly), organic carbon (OC), elemental carbon (EC) and water-soluble OC (WSOC). Oxalic acid (C_2) was detected as the most abundant species, followed by succinic (C_4) and malonic (C_3) acids. Temporal variation in concentrations of C_2 diacid and related compounds was pronounced from early to late April when biomass burning (BB) was dominant in eastern central India. Strong positive correlations of C_2 diacid and related compounds with levoglucosan (r = 0.83-0.99) further demonstrate that organic aerosols (OAs) were affected by BB in eastern central India. Strong positive correlations of C_2 with saturated diacids (C_3-C_9: r = 0.78-0.97), ωC_2 (r = 0.98), Gly (r = 0.96) and MeGly (r = 0.84) suggest that their sources and formation processes were similar and oxalic acid might be produced via the photochemical degradation of precursor compounds. The relatively high ratios of WSOC to OC (avg. 0.69) and C_3 to C_4 diacid (avg. 0.95) suggest that water-soluble OAs were photochemically processed during the campaign. The total water-soluble organic compounds detected in Ambikapur PM_(2.5) samples accounted for an average of 1.9% (1.1-3.1%) of OC. Our results demonstrate that BB and photochemical processing caused high levels of water-soluble organic compounds over eastern central India.
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This study investigated the inter-correlation of atmospheric PM_(2.5) between southern Taiwan and the northern Philippines. 24-hour samples of PM_(2.5) were simultaneously collected at two remote sites, Checheng (Taiwan) and Laoag (Philippines), during all four seasons. The water-soluble ions, metallic elements, carbonaceous content, and anhydrosugars in the PM_(2.5) were then analyzed to characterize the chemical fingerprint. Furthermore, principal component analysis, chemical mass balance (CMB) receptor modeling, and backward trajectory simulation were applied to resolve the source apportionment of PM_(2.5) at both of the sites. The results showed that Checheng and Laoag were highly influenced by polluted air masses transported long-range from the north, producing elevated PM_(2.5) concentrations during winter and spring. The water-soluble ions (WSIs) were abundant in secondary inorganic aerosols (SO_4^(2-), NO_3^-, and NH_4^+), which accounted for 34.1-76.0%. Crustal elements dominated the metallic content in the PM_(2.5), but the concentrations of trace elements originating from anthropogenic sources increased during the northwestern monsoon periods. More organic carbon (OC) than elemental carbon (EC) was found, with secondary OC (SOC) contributing approximately 23.9-38.9% to the former. Moreover, the level of levoglucosan highly correlated with those of K^+ and OC, confirming that these three substances are key indicators of biomass burning. The two sites exhibited similar chemical compositions for PM_(2.5), indicating the possibility of transport between Checheng and Laoag, and a paired t-test obtained a p-value of 0.030 (p ＜ 0.05), implying a potential inter-correlation for PM_(2.5) between southern Taiwan and the northern Philippines. The major sources of the PM_(2.5) were soil dust, mobile sources, sea salt, and biomass burning along the northerly transport routes during winter and spring. The contribution of anthropogenic sources (i.e., industrial boilers, waste incinerators, and secondary aerosols) to the PM_(2.5) frequently increased during winter and spring, unlike during summer, suggesting that the northerly transport of PM_(2.5) highly affected particulate air pollution at both of the sites.
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Atmospheric pollution has been found to modify the hygroscopicity of particles and the ability of aerosols to become cloud condensation nuclei (CCN). Aerosols and the bulk CCN were measured in urban Guangzhou during pollution periods in January 2016, and the particle liquid water content (PLWC) and aerosol acidity (Aero-pH) were calculated to examine their possible effects on aerosols' CCN activation. The results demonstrate that the PLWC and Aero-pH likely play key roles in enhancing aerosol activation during the early stages of pollution episodes. The analysis of the calculated and the observed data shows that CCN, PLWC, Aero-pH and water-soluble inorganic matter (WSIM) are closely linked to each other, particularly at night, and Aero-pH and PLWC act as pre-occurring indicators of activated aerosols and aerosol activity, respectively, during the rapid onset of pollution. In theory, the feedback between chemical reactions, aerosol acidity and particle water content accounts for the changes in aerosol activation accompanying particle accumulation and aging. Our research provides insights into the swift formation of particle pollution characterized by secondary aerosols and suggests a possible approach to tracking or characterizing its effects on the activation of aerosols into CCN without requiring CCN or aerosol number measurements.
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To investigate the molecular characteristics and formation mechanisms of biogenic secondary organic aerosol (BSOA), daytime and nighttime PM_(2.5) samples were collected at the summit of Mt. Tai during the summer of 2016. The critical indicators of primary sources, such as elemental carbon (EC) and levoglucosan, displayed similar values during the daytime and nighttime, suggesting that changes in the boundary layer heights (BLHs) produced only inconsequential effects during the observation campaign. The molecular distributions of the BSOA were dominated by isoprene SOA tracers (68.5 ± 42.6 ng m^(-3)), followed by monoterpene (43.5 ± 24.4 ng m^(-3)) and β-caryophyllene (16.3 ± 8.6 ng m^(-3)) SOA tracers. Due to the higher diurnal temperatures and solar radiation, the concentrations of all of the tracers were higher during the day than at night. The ratio of the combined cis-pinonic and cis-pinic acid to the MBTCA (P/M) was much lower than in Chinese cities and at the Tibetan background site, indicating that the monoterpene SOA was relatively aged in the mountainous atmosphere, in large part because of the stronger solar radiation at the peak of Mt. Tai. The concentrations of the BSOA products exhibited a significantly positive correlation with the level of ozone during the daytime (R^2 = 0.58-0.86) and the temperature over the whole sampling period (R^2 = 0.37-0.75), as higher temperatures can accelerate the emission of biogenic volatile organic compounds and the formation of SOA. By contrast, the BSOA tracers displayed a negative linear correlation with the relative humidity (RH) (R^2 = 0.43-0.84) and the in situ particle pH (pH_(is)) (R^2 = 0.55-0.70) because high RH can inhibit the acid-catalyzed formation of BSOA due to the dilution of the aerosol acidity. No correlation between the BSOA tracers and anthropogenic pollutants (e.g., levoglucosan, SO_4^(2-), NO_3^- and EC) was observed during the daytime or nighttime, suggesting that BSOA tracers in the atmosphere of Mt. Tai during summer were primarily derived from the local oxidation of BVOCs rather than long-distance-transported anthropogenic emissions from the lowlands.
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The National Air Pollution Control Plan implemented by China in 2013 reduced the concentrations of air pollutants, especially PM_(2.5) (aerosol particles with an aerodynamic diameter equal to or less than 2.5 μm), between 2014 and 2017. This reduction in PM_(2.5) potentially affected the intensity of urban heat islands (UHIs), as the presence of fine particles can influence the energy balance of the earth-atmosphere system. In this study, the effect of the pollution control plan on the UHI intensity in the Yangtze River Delta, China, was investigated via observational analysis and numerical modeling. According to the observational data, the PM_(2.5) concentrations in the megacities of the Yangtze River Delta, viz., Shanghai, Nanjing, Hangzhou and Hefei, in 2017 were ~35 μg m^(-3), showing decreases of approximately 48.36%, 28.25%, 29.41% and 32.5%, respectively, compared to 2014. Furthermore, these reductions in the PM_(2.5) concentration correlated well with the strengthened diurnal intensity (increasing by up to 1 K) and the weakened nocturnal intensity (decreasing by up to 1 K) of the UHIs. Numerical simulations confirmed that this ＂seesaw effect＂ on the UHI intensity was due to the decrease in PM_(2.5) and the consequent increase in the downward surface shortwave radiation and the outgoing top-of-the-atmosphere longwave radiation. Thus, the Air Pollution Control Plan noticeably affected the UHI intensity by reducing PM_(2.5)-a factor which should be considered in future studies on urban climate and environmental planning.
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In order to determine the seasonal characteristics of water-soluble inorganic ions (WSIIs) in aerosols in urban atmospheres, size-segregated particulate matter (PM) samples were collected over a one-year period from February 2012 to January 2013 in a typical urban location, Chengdu in Southwest China, using an Andersen cascade impactor sampler. The PM mass concentrations, particularly the fine fraction, peaked during winter, and the WSIIs were more enriched in the fine fraction (21.7%) than the coarse fraction (9.2%). The sums of the equivalent ratios of cations (Na^+, NH_4^+, K^+, Mg^(2+), and Ca^(2+)) to anions (SO_4^(2-), NO_3^-, Cl^-, and F^-) indicated that the fine particles (0.86) were more acidic than the coarse ones (1.60). The average NH_4^+/SO_4^(2-) molar ratio (A/S) in the fine fraction (1.79) was much higher during winter than the other three seasons (＜ 1.5), implying a generally NH_3-poor atmosphere in Chengdu; hence, the NO_3^- in the fine particles was principally formed through homogeneous reactions involving ammonia and nitric acid during winter, whereas it was heterogeneously formed during the other three seasons. Significant positive correlations were observed between the A/S and NO_3^- molar concentrations during spring and winter; therefore, the formation of particle-phase NO_3^- may be accelerated by increased A/S in both NH_3^- poor and -rich atmospheres. Moreover, the A/S and NO_3^-/SO_4^(2-) molar ratios displayed negative and positive correlations during spring and winter, respectively, suggesting that the variation in atmospheric NH_4^+ (or NH_3) during winter affected the formation of NO_3^- more strongly than that of SO_4^(2-), whereas more SO_4^(2-) than NO_3^- was formed in the NH_3-poor atmosphere during spring, when most of the NO_3^- in the aerosols would be expected to form via heterogeneous reactions.
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Substantial biomass burning (BB) activities in Indochina during March and April of each year generate aerosols that are transported via westerly winds to southern China. These BB aerosols have both radiative (direct and semi-direct) and indirect effects on the climate. This study evaluates impacts of BB in Indochina during April 2013 on atmospheric conditions in southern China using WRF-Chem sensitivity simulations. We show that the atmosphere becomes drier and hotter under the aerosol radiative effect in southern China, while the changes linked to the indirect effect are opposite. The former (the latter) rises (reduces) surface temperature 0.13°C (0.19°C) and decrease (increase) water vapor mixing ratios 0.23 g kg^(-1) (0.40 g kg^(-1)) at 700 hPa. Atmospheric responses to aerosols in turn affect aerosol dissipation. Specifically, BB aerosols absorb solar radiation and heat the local atmosphere, which inhibits the formation of clouds (reducing low-level cloud about 7%) related to the aerosol semi-direct effect. Less cloud enhances surface solar radiation flux and temperature. Otherwise, northeasterly winds linked to radiative effect suppress water vapor transport. In this case, precipitation reduces 1.09 mm day^(-1), diminishing wet removal and westward transport of aerosols. Under the indirect effect, greater cloud coverage is formed, which reduces surface solar radiation flux and increases local latent heat release. This extra heating promotes air convection and diffusion of pollution. Regional mean precipitation increases 0.49 mm d^(-1), facilitating wet pollution removal. Under indirect effect, aerosol extinction coefficient reduces 0.011 km^(-1) at 2-km height over southern China. However, it increases around 0.002 km^(-1) at 3-km height over southernmost China related to radiative effect. Therefore, atmospheric changes linked to indirect effect play a greater role in removing pollutants from the atmosphere than radiative effect over southern China.
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To estimate the spatial and temporal variation in urban particle number concentrations (PNCs), e.g., for exposure studies, a better knowledge of the exchange of particles between the urban surface and the atmosphere is important. Size-resolved fluxes of PNCs were quantified in Berlin, Germany, using the micrometeorological eddy covariance technique. The method requires measurements of particle number size distributions (PNSDs) by a fast particle spectrometer. The Engine Exhaust Particle Sizer (EEPS) Spectrometer 3090 (TSI Inc.) is designed for fast (10 Hz), high-concentration measurements of particles in the size range of 5.6-560 nm, e.g., in the exhaust plume of engines. In the urban background environment of Berlin, however, PNCs in some size channels can temporarily fall below the minimum threshold concentration of the analyser, resulting in missing concentrations that lead to gaps in the PNSD. In the present study, three gap-filling methods were applied to derive complete PNSDs: linear interpolation (LI), natural spline interpolation (NSI) and log-normal fitting (LNF). To evaluate the methods, different numbers of artificial gaps were inserted into 10^5 gapless PNSDs. Using three different data sets, the results demonstrate that LI and NSI (LI: R^2 = 0.84-0.94; NSI: R^2 = 0.84-0.95) outperform LNF (R^2 = 0.78-0.88). With regard to the Berlin data set, NSI is the recommended gap-filling method since it results in a lower average uncertainty of 10.5-21.8% vs. 13.3-22.9% for LI. It is advisable to reject the boundary areas of the PNSD from gap filling, i.e., D_p ＜ 10 nm and D_p ＞ 200 nm, as this considerably improves the gap-filling quality. This study provides recommendations on how to gap-fill incomplete PNSD data sets obtained with an EEPS.
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The rapid expansion of the worldwide tourism industry has significantly increased energy consumption in hotels. Hence, the renovation of existing hotel buildings is relevant to achieving the energy-saving goals of the construction sector. This study takes a hotel in eastern China as an example of energy-saving renovation. First, based on a BECS energy-saving design and SPSS statistical analysis software, the energy-saving effects of renovation of building envelope (windows, walls, and roofs) are dynamically simulated, and a comparison of various renovation schemes is carried out by adopting an orthogonal experimental method and conducting a variance analysis. Second, the energy performance of the lighting and air conditioning systems is analyzed during the entire renovation process. Third, the economic environmental and social benefits were comprehensively analyzed. The results show that energy-saving renovations can effectively reduce energy consumption in existing buildings as well as the associated CO_2 emissions. Specifically, the energy-savings rate of the building envelopes and the energy systems were 14%-20% and 60%-70% respectively. As for carbon emission, 947.55 tons of total CO_2 emissions per year were eliminated through the renovation project. Specifically, CO_2 emission reductions reach 247.65 tons per year through energy-saving renovation of building envelope, and CO_2 emissions reductions resulting from the renovation of the air-conditioning system and lighting system were 220.88 tons and 479.09 tons per year respectively. Additionally, the dynamic investment payback period of the hotel energy-saving renovation project was calculated to be between 8-9 years. The demonstrates that the renovation of hotel buildings plays an essential role in benefiting the environment and the economy and social welfare.