Suburban Nanjing Research Articles

Significance of Volatile Organic Compounds to Secondary Pollution Formation and Health Risks Observed during a Summer Campaign in an Industrial Urban Area.

The chemical complexity and toxicity of volatile organic compounds (VOCs) are primarily encountered through intensive anthropogenic emissions in suburban areas. Here, pollution characteristics, impacts on secondary pollution formation, and health risks were investigated through continuous in-field measurements from 1-30 June 2020 in suburban Nanjing, adjacent to national petrochemical industrial parks in China. On average, the total VOCs concentration was 34.47 ± 16.08 ppb, which was comprised mostly by alkanes (41.8%) and halogenated hydrocarbons (29.4%). In contrast, aromatics (17.4%) dominated the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) with 59.6% and 58.3%, respectively. Approximately 63.5% of VOCs were emitted from the petrochemical industry and from solvent usage based on source apportionment results, followed by biogenic emissions of 22.3% and vehicle emissions of 14.2%. Of the observed 46 VOC species, hexachlorobutadiene, dibromoethane, butadiene, tetrachloroethane, and vinyl chloride contributed as high as 98.8% of total carcinogenic risk, a large fraction of which was ascribed to the high-level emissions during ozone pollution episodes and nighttime. Therefore, the mitigation of VOC emissions from petrochemical industries would be an effective way to reduce secondary pollution and potential health risks in conurbation areas.

Pollution Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons in Agricultural Soils of Different Land Use Types in Nanjing Suburbs

In order to clarify the pollution characteristics of PAHs in suburban agricultural soils, the content of 16 types of PAHs was measured in agricultural soils with different land use types (paddy fields, vegetable fields, and forest land) in the suburbs of Nanjing. The results showed that acenaphthene (Acy) was not detected in any soil samples. The concentration of 15 PAHs in agricultural soil in suburban Nanjing ranged from 24.49 to 925.54 μg·kg-1, with an average concentration of 259.88 μg·kg-1. In different land use types, the order of PAHs concentration in soil from high to low was:forest land>paddy fields>vegetable fields, and the high-ring PAHs content was dominant in general. The effects of different soil physicochemical properties on PAHs showed that there was a certain correlation between soil organic carbon (TOC) and clay (clay) content and PAHs, whereas pH and total nitrogen (TN) had no significant correlation with PAHs. The toxic equivalence method and CSI index method were used for ecological risk assessment, which showed that the ecological risk of PAHs in agricultural soils in suburban Nanjing was relatively small; however, the ecological risk of PAHs in forest land should be given some attention, and supervision should be strengthened. Health risk assessment using incremental lifetime cancer risk (ILCR) showed that the threat to the health of children was slightly greater than that of adults, and the CR of forest land was significantly higher than that of vegetable and paddy fields, though still within an acceptable range. Uncertain health assessments were performed in adults, showing that risk analyses of deterministic health risks underestimated the health risks of PAHs. The results of sensitivity analysis showed that the input parameter that had the greatest impact on the total variance of the total carcinogenic risk CR was the exposure frequency EF (50.7%), followed by the pollutant concentration CS (43.3%).

Assessment of carbonaceous aerosols in suburban Nanjing under air pollution control measures: Insights from long-term measurements

The concentrations of organic carbon (OC) and elemental carbon (EC) in fine particulate matter (PM2.5) were analyzed using a semicontinuous carbon analyzer to characterize their carbonaceous components at the Nanjing University site from August 2013 to December 2018. OC was divided by the minimum R squared (MRS) method into primary organic carbon (POC) and secondary organic carbon (SOC). The results showed that annual mean POC and EC concentrations declined from 10.00 to 3.62 μg m−3 and from 6.73 to 3.40 μg m−3, respectively, during 2013–2018. The apparent reduction in POC and EC concentrations indicated that the implementation of air pollution control measures helped reduce carbonaceous aerosol pollution. Higher concentrations of POC and EC were recorded during the cold season and lower in the warm season. The annual mean SOC concentrations varied between 4.35 and 3.18 μg m−3 from 2013 to 2018. Elevated SOC was observed during the warm season, most likely attributable to the enhanced photochemical activity at high temperatures. Regarding the diurnal variation, the high concentrations of POC and EC were observed at night and in the morning due to stronger primary emissions and accumulations of pollutants with low boundary-layer heights, while the peak of SOC was observed at approximately noon due to the increases in photochemical activity. Nonparametric wind regression analysis showed the higher concentrations of POC, SOC and EC in the northwesterly, southwesterly to southeasterly, and southwesterly winds with high speeds. Concentration-weighted trajectory (CWT) analysis suggests that the areas with potentially high contributions to POC and EC changed from the north to the western areas of China, and that northern China played an increasingly important role in the SOC concentration of Nanjing. These results demonstrate that controlling emissions from the western and the northern areas in China may further alleviate carbonaceous aerosol pollution in Nanjing.

Chemical composition, sources and optical properties of nitrated aromatic compounds in fine particulate matter during winter foggy days in Nanjing, China

Functionalized aromatic compounds are one of the most important light-absorbing organic chromophores – so-called brown carbon (BrC) – in fine particulate matter (PM2.5). In this study, we conducted a wintertime field campaign to measure eight nitrated aromatic compounds (NACs) in PM2.5 with offline analysis techniques, including liquid chromatograph mass spectrometer (LC-MS) and aerodyne high-resolution aerosol mass spectrometer (AMS) measurements, during foggy and nonfoggy days in suburban Nanjing in the Yangtze River Delta region, China. On average, 4-nitrophenol could be one of the most important light absorbing materials in the observed BrC, which accounted for over 40% of the mass concentration of identified chromophores. The mass concentration of 2-methyl-4-nitrophenol and 2,6-dimethyl-4-nitrophenol were evidently increased during foggy days, contribution of which to total NACs were increased by 10% and 5%, respectively. Positive matrix factorization analysis of combining LC-MS and AMS dataset was performed to identify the primary and secondary sources of NACs. Primary sources, e.g., traffic and solid-fuel combustion, accounted for 71% of the sum of 4-nitrophenol, 2,6-dimethyl-4-nitrophenol and 3-nitrosalicylic acid, suggesting important contribution of primary emissions to these NACs. The contribution of secondary sources, associated with two oxygenated organic aerosols, could contribute 66% to 4-nitrophenol, reflecting the link of such nitrated aromatic compounds to secondary organic aerosol source. Together with optical measurements, 4-nitrophenol presented a high contribution (>50%) to the identified BrC absorbance in the light range 250 and 550 nm was observed. This could highlight an important role of such NACs in ambient BrC light absorption, despite its mass contribution to total organic carbon was negligible. Our work could improve the understanding of the links between optical properties and chemical composition of BrC, and the difference between BrC chromophores from nonfoggy days and foggy days under the typical polluted atmospheric conditions.

Characteristics and Sources of Nitrated Phenols in Atmospheric Fine Particles of Northern Suburban Nanjing

Nitrated phenols are a group of nitrogen-containing organics ubiquitously present in ambient air, which are also important components of atmospheric light-absorbing organic matter (brown carbon) that have significant impacts on climate change, air quality, and human health. In this study, we collected a total of 265 daily filter samples of fine particles (PM2.5) in northern suburban Nanjing from March 2019 to January 2020. We used ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) to detect and quantify eight nitrated phenolic species. The results showed that the average annual concentration of total nitrated phenols in the sampling site was 18.77 ng·m-3, and the average concentrations in spring, summer, autumn, and winter were 16.82, 8.59, 17.28, and 44.79 ng·m-3, respectively. Such concentrations were obviously higher than those determined in other countries but were similar to those in domestic cities, such as Jinan. 4-Nitrophenol was the most abundant nitrated phenol, followed by 4-nitrocatechol and 2-methoxy-5-nitrophenol. Correlation analysis showed that 3-nitrosalicylic acid was from a specific source different from that of other species. Finally, we used a positive matrix factorization model to quantify the source contributions of nitrated phenols. The major sources were vehicle emissions (32%), mixed coal and biomass burning emissions (44%), and industrial emissions (24%). The mixed coal and biomass burning emissions were dominant in autumn and winter. The mass fraction of 3-nitrosalicylic acid in the factor of industrial emissions was>90%, consistent with the results of the correlation analysis. Overall, this study provides valuable insights into the understanding of concentrations, characteristics, and sources of atmospheric nitrated phenols in ambient air.

Seasonal variations, temperature dependence, and sources of size-resolved PM components in Nanjing, east China

Size-segregated ambient particulate matter (PM) samples were collected seasonally in suburban Nanjing of east China from 2016 to 2017 and chemically speciated. In both fine (< 2.1 µm, PM2.1) and coarse (> 2.1 µm, PM>2.1) PM, organic carbon (OC) accounted for the highest fractions (26.9% ± 10.9% and 23.1% ± 9.35%) of all measured species, and NO3− lead in average concentrations of water-soluble inorganic ions (WSIIs). The size distributions of measured components were parameterized using geometric mean diameter (GMD). GMD values of NO3−, Cl−, OC, and PM for the whole size range varied from < 2.1 µm in winter to > 2.1 μm in warm seasons, which was due to the fact that the size distributions of semi-volatile components (e.g., NH4NO3, NH4Cl, and OC) had a dependency on the ambient temperature. Unlike OC, elemental carbon (EC), and elements, NH4+, NO3−, and SO42− exhibited an increase trend in GMD values with relative humidity, indicating that the hygroscopic growth might also play a role in driving seasonal changes of PM size distributions. Positive matrix factorization was performed using compositional data of fine and coarse particles, respectively. The secondary formation of inorganic salts contributing to the majority (> 70%) of fine PM and 20.2% ± 19.9% of speciated coarse PM. The remaining coarse PM content was attributed to a variety of dust sources. Considering that coarse and fine PM had comparable mass concentrations, more attention should be paid to local dust emissions in future air quality plans.

EVALUATING VILLAGERS' LIFE SATISFACTION IN RESETTLEMENT COMMUNITY: A PILOT STUDY OF SUBURBAN NANJING, CHINA

This paper assesses displaced villagers’ life satisfaction in government-designated resettlement communities after land expropriation. From the theoretical perspective of subjective well-being, the study explores the relationship between the overall life satisfaction of displaced villagers and their subjective satisfaction with three dimensions in their post-resettlement life – 1) material living conditions, 2) social security and employment support, and 3) attitudinal perceptions, social relations and participation. A pilot survey was conducted in two resettlement communities in suburban Nanjing. The study shows that while compensation and resettlement policy reforms have improved resettled villagers’ material living conditions; they still struggle with urban life transformation and adaptation from the social and attitudinal perspectives. An integrated resettlement approach is proposed to facilitate better accessibility to social security programs and non-agricultural employment opportunities, and to address issues in identity adaptation, lifestyle transformation, and social activity participation.

Characteristics and potential sources of black carbon particles in suburban Nanjing, China

As an important species of ambient fine particles, black carbon (BC) has significant adverse effects on air quality, human health and climate. This work reports results of one-year measurement of BC conducted in northern suburb of Nanjing, China from December 2017 to November 2018. Annual mean BC concentration was determined to be 2.78 μg/m³. BC concentration presented a “U” shape from December to November, lowest in summer and highest in winter. Nighttime BC concentration on average was higher than it in daytime, indicating heavier influence of meteorology than emissions. Diurnal pattern revealed that besides a clear emission-induced morning peak, meteorology played a more important role in governing BC changes in the rest of the day. Influences of meteorological factors on BC were in an order of boundary layer height, wind speed, temperature and relative humidity (RH), and further Granger causality analysis verified that the first three factors were indeed Granger causes of BC, while RH was not. Based on the diagnostic mass ratios of BC to CO, NO2 and SO2, as well as their correlation coefficients, we inferred that diesel vehicles rather than gasoline vehicles were the major BC emission source in suburban Nanjing; contributions from industry coal combustion were relatively less important. Back trajectory and potential source contribution analyses showed that regional rather than long-range transported air parcels led to the BC pollution in this site. Our findings provide useful insights into the reductions of BC and air pollution in this and similar atmospheric environments.

Characteristics of Black Carbon Particle-Bound Polycyclic Aromatic Hydrocarbons in Two Sites of Nanjing and Shanghai, China

Airborne polycyclic aromatic hydrocarbons (PAHs) are of great concern to human health due to their potential high toxicity. Understanding the characteristics and sources of PAHs, as well as the governing factors, is therefore critical. PAHs and refractory black carbon (rBC) are both from combustion sources. This work, for the first time, investigated exclusively the rBC-bound PAH properties by using a laser-only Aerodyne soot-particle aerosol mass spectrometer (SP-AMS). This technique offers highly time-resolved PAH results that a traditional offline measurement is unable to provide. We analyzed two datasets conducted in urban Shanghai during the fall of 2018 and in suburban Nanjing during the winter of 2017, respectively. Results show that the average concentration of PAHs in Nanjing was much higher than that in Shanghai. Nanjing PAHs contained more low molecular weight components while Shanghai PAHs contained more high molecular weight ones. PAHs in Shanghai presented two peaks in early morning and evening, while Nanjing PAHs had only one significant morning peak, but remained high throughout the nighttime. A multi-linear regression algorithm combined with positive matrix factorization (PMF) analyses on sources of PAHs reveals that the industry emissions contributed the majority of PAHs in Nanjing (~80%), while traffic emissions dominated PAHs in Shanghai (~70%). We further investigated the relationships between PAHs with various factors. PAHs in both sites tended to positively correlate with primary pollutants, including primary organic aerosol (OA) factors, and gaseous pollutants of CO, NO2 and SO2, but negatively correlated with secondary OA factors and O3. This result highlights the enhancement of rBC-bound PAHs level due to primary emissions and their oxidation loss upon atmospheric aging reactions. High concentration of PAHs seemed to frequently appear under low temperature and high relative humidity conditions, especially in Shanghai.

A Comparison Study of Indoor and Outdoor Air Quality in Nanjing, China

ABSTRACT Because humans spend much of their time in indoor microenvironments, the air quality indoors has attracted significant attention. This study simultaneously conducted real-time indoor observations and comprehensive outdoor measurements of O3, CO and PM2.5 in suburban Nanjing in eastern China from September to December 2018. The O3, CO and PM2.5 exhibited median indoor concentrations of 3.2 ppb, 395.8 ppb and 17.3 µg m–3, respectively, based on measurements in a room with closed windows and relatively regular daily indoor human activity, and median outdoor values of 30.5 ppb, 386.1 ppb and 37.2 µg m–3, resulting in median indoor-outdoor (I/O) ratios of 0.14, 1.01 and 0.46. Moreover, the indoor concentrations traced the outdoor variations with correlations of approximately 0.68, 0.82 and 0.82 for the O3, CO and PM2.5, respectively. During pollution episodes, the indoor O3 and PM2.5 concentrations reached about 30 ppb and 130 µg m–3, respectively. Both meteorological conditions (e.g., wind speed or relative humidity) and human activity indoors influenced the relationships between the indoor and outdoor concentrations, including the I/O ratios and time lag. A simplified indoor-outdoor mass-balance equation was developed to simulate the indoor concentrations, and the predictions fitted the observed data for most of the testing period, especially after considering the human activity indoors and limited penetration of particles. This study enhances our understanding of the indoor-outdoor relationships for gaseous and particulate matter concentrations in polluted areas such as the Yangtze River Delta and highlights the urgent need for improving indoor air quality in the megacities of China.

Characterization of Size-Resolved Hygroscopicity of Black Carbon-Containing Particle in Urban Environment.

The hygroscopic properties of BC-containing particles (BCc) are important to determine their wet scavenging, atmospheric lifetime, and interactions with clouds. Such information is still lacking in the real world because of the challenges in isolating BCc from other aerosols to be directly characterized. In this study, the size-resolved chemical components of BCc including the refractory BC core and associated coatings were measured by a soot particle-aerosol mass spectrometer in suburban Nanjing. The size-resolved hygroscopicity parameter of BCc (κBCc) was obtained based on this full chemical characterization of BCc. We found increased inorganic fraction and more oxidized organic coatings with thicker coatings, which modified κBCc besides the determinant of particle size. The bulk κBCc was observed to range from 0.11 to 0.34. The size-resolved κBCc consistently showed minima at coated diameter (Dcoated) of 100 nm, parametrized as κ(x) = 0.28-0.35 × exp(-0.004 × x), x = Dcoated. Under critical supersaturations (SS) of 0.1% and 0.2%, the D50 values of BCc were 200 ± 20 and 135 ± 18 nm, respectively. On average 33 ± 16% and 59 ± 20% of BCc in number could be activated at SS = 0.1% and 0.2%, respectively. These results provide constraints on surface CCN sources for the light-absorbing BC-containing particles.

Chemical composition of dew water at a suburban site in Nanjing, China, during the 2016–2017 winter

A dew condenser was used to collect dew and frost samples to investigate the chemical properties of dew water for comparison with frost, rain and fog in Nanjing, China during the 2016–2017 winter. Twenty-three separate ambient dew samples were collected at a grassland site in suburban Nanjing, China, from 1st November 2016 to 20th January 2017. Six frost samples, two fog water samples and 13 rainwater samples were also collected for comparative study. Cations (Na+, Ca2+, NH4+, K+, and Mg2+), anions (NO3−, NO2−, Cl−, SO42−, and F−) and pH were detected and measured in all wet depositional samples. In addition, seven kinds of water-soluble ions (WSIs) in atmospheric fine particulates (PM2.5) and atmospheric gas (SO2 and NH3) concentrations were investigated. The field study elucidated that dew water resembles frost water, with WSIs ranked in the order of Ca2+> NH4+> Na+> Mg2+> K+ for cations and SO42− > NO3− > Cl− > NO2− > F− for anions. Most dew and frost samples were alkaline and not as acidic as the rainwater and fog water samples. The mean concentrations of various ions and total ionic content (TIC) in the fog samples were the highest, while the ion concentration ranges in the dew, rain and frost samples were similar. The neutralization strength decreased in the order of NH4+>Ca2+>Mg2+>K+ for the fog samples and decreased in the order of Ca2+> NH4+>Mg2+>K+ for the dew, frost and rainwater samples. A high pairwise correlation between K+, Mg2+ and Ca2+ was observed, which means these cations shared a common crustal source. The SO42−, NO2− and Cl− ions were closely correlated, indicating that the ions were released simultaneously from anthropogenic sources. The low and negative correlations among the NO3−, SO42− and NH4+ ions in the dew water and PM2.5 may imply that fine-mode aerosols have little impact on the composition of dew, which means that the dew water component was dominated by coarse-mode aerosols. The NH3 in the atmosphere plays an important role in dew water due to the strong relationship between NH3 and NH4+.

State-led commodification of rural China and the sustainable provision of public goods in question: A case study of Tangjiajia, Nanjing

This paper examines the commodification process initiated through a series of state-led programs and questions the sustainable public goods provision in rural China. We challenge the unilateral understanding of spontaneous commodification by the profit-seeking community, and argue that the influence exerted by the Chinese government cannot be ignored. It is found that a preliminary partnership among the state, private investors and villagers was formed to create a hot-spring village called Tangjiajia in suburban Nanjing. The reconstruction was the result of a state-led renovation of the built environment, but it also catalyzed villager entrepreneurship and boosted community consensus. Regarding the public goods provision, stakeholders in the village now enjoy high-quality facilities and services provided by the government for free but have failed to foster reciprocal cooperation to replenish the subtractability of the rural commons. We claim that state intervention is temporal but not a cure-all. A pricing mechanism for the sustainable delivery of public goods is urgently needed in the community. The state-led commodification has undermined the previous low-level equilibrium of rural governance. From the stance of rural sustainability, only self-organization of the rural community can solve the dilemma.

Evaluation of particulate matter deposition in the human respiratory tract during winter in Nanjing using size and chemically resolved ambient measurements

Size-segregated ambient aerosols were collected by a five-stage impactor at a suburban Nanjing site during the winter of 2016–2017 to estimate the chemical composition and size distribution of particles deposited in different parts of the human respiratory tract. Chemical compositions of carbonaceous aerosols, water-soluble ions, and trace heavy metals were measured. Particulate matter (PM) mass deposited in nasopharyngeal (NOPL), tracheobronchial (TB), and pulmonary (P) was obtained by integrating the size-dependent deposition fractions. During the sampling period, the average PM10 and PM2.5 concentrations were 108.8 ± 30.8 and 77.2 ± 24.2 μg/m3, respectively. Organic matter and water-soluble ions were major components in fine particles. The fine particles had a significant contribution to the particulate pollution in winter Nanjing. The mass concentration of particles increases significantly from the clean days to the pollution days, especially for particles in 1–2.5 μm. The proportion of NO3− and undetected components in particulate matter increases on pollution days, while the proportion of elemental carbon (EC), SO42−, and NH4+ decreases. During the study period, the total particulate matter deposit per minute in the NOPL, TB, and P was 1.06 ± 0.35, 0.10 ± 0.03, and 0.42 ± 0.14 μg, respectively, assuming normal respiration of tidal volumes of 1450 cm3 per breath and 15 breaths per minute. Particles in 2.5–10 μm had the highest deposition mass in NOPL of 0.57 ± 0.16 μg, while particles in < 0.5 μm had the highest deposition mass in TB (0.03 ± 0.01 μg), and particles in 1–2.5 μm had the highest deposition mass in P (0.14 ± 0.06 μg). The total particulate matter deposited in the NOPL, TB, and P increased from 0.79 ± 0.25, 0.08 ± 0.02, and 0.30 ± 0.09 μg on the clean days to 1.23 ± 0.29 μg, 0.12 ± 0.03 μg, and 0.49 ± 0.11 μg on the pollution days. More secondary inorganic aerosol (SNA) and metals (especially Zn, Cr, and Cu) were in the PM deposited in TB and P than in the ambient PM, while more undetected components in the PM deposited in NOPL. The chemical composition fractions deposited in a specific region were different from those measured in the ambient atmosphere, indicating that health effect studies of PM should consider the deposition rates of PM in the human respiratory tract, in addition to the ambient size and chemical characteristics of ambient PM.

Characteristics and sources of ambient refractory black carbon aerosols: Insights from soot particle aerosol mass spectrometer

This short communication investigated the characteristics and sources of refractory black carbon (rBC) aerosols using an Aerodyne soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS dataset acquired at suburban Nanjing observed carbon clusters (Cn+) up to n = 160, which was classified into three groups (low-C: C1+-C5+; mid-C: C6+-C31+; full-C (fullerenes): C32+-C160+). A simple method was first developed to reduce influences of organic molecules on the Cn+ signals. We found that the temporal variations of low-C and mid-C varied similarly, but were substantially different from full-C, indicating different source contributions. Furthermore, positive matrix factorization analyses showed that the C1+/C3+ ratios of traffic-, industry-, cooking-related rBC were 0.88, 1.29 and 0.01, respectively. We propose such C1+/C3+ ratios can be used as references to distinguish different sources for rBC in ambient conditions, yet further verifications with more field data are still required, and whether or not such ratios in rBC cores are stable upon atmospheric ageing remains to be elucidated.

Seasonal Variation in Water-Soluble Ions in Airborne Particulate Deposition in the Suburban Nanjing Area, Yangtze River Delta, China, During Haze Days and Normal Days.

To investigate the seasonal variation and characterization of water-soluble ions (WSIs) present in airborne particle deposition (APD) during Haze Days (visibility ≤7.5km) and Normal Days (visibility >7.5km) in suburban Nanjing area, 151 filter samples were collected from 18 May 2013 to 26 May 2014. Ten different WSIs from the samples were determined by Ion Chromatography. The results indicated that secondary WSIs (NH4+, NO3-, and SO42-) were the main ions in the WSIs, averaging 17.2, 18.5, and 17.1μg/m3, respectively, and accounting respectively 20.9, 22.5, and 20.8% of the total WSIs. On Haze Days, the concentration of WSIs increased dramatically in fine size (particle size <2.1μm), especially for NH4+, NO3-, and SO42- (increased by 52.6, 71.3, and 73.1%, respectively), whereas the concentrations of WSIs increased slowly in coarse size (2.1μm<particle size<10μm), in which NH4+, NO3-, and SO42- increased by 14.7, 27.2, and 54.5%, respectively. According to the backward trajectories and the principal component analysis analysis, Nanjing APD were mainly derived from the soil dust in northern China (35%) in the spring, from ocean air masses (61 and 55%) in the summer and the autumn, and from local air masses (73%) in the winter. On summer Haze Days, secondary components in PM2.1 consisted mainly of (NH4)2SO4 and NH4NO3, whereas secondary components in PM2.1-10 consisted mainly of (NH4)2SO4, NH4Cl, and NH4NO3. The increasing concentrations of secondary components increase the light extinction coefficients of aerosol on winter and autumn Haze Days. The concentrations of WSIs in fine size rose sharply on Haze Days, leading the visibility to exponential decline. Differently, the concentrations of WSIs in coarse size were not the main cause in the change of the visibility.

Chemical and Light Extinction Characteristics of Atmospheric Aerosols in Suburban Nanjing, China

This work reports the chemical and light extinction characteristics of the atmospheric particles collected from January to November 2014 in suburban Nanjing. Size-segregated measurement results showed that more than 80% of the major aerosol components were concentrated in PM2.5. The concentration of PM2.5 was highest in winter and lowest in autumn. Specifically, K+ concentration peaked in late spring indicating heavy influences from straw burning, while sulfate concentration was highest in summer and its daytime concentration was also higher than its nighttime concentration, both reflecting a significant role of photochemical production. Nevertheless, except for sulfate, all other components had higher concentrations during nighttime, signifying the role of unfavorable meteorological conditions in exacerbating the air pollution. The IMPROVE formula was employed, which can reconstruct the PM2.5 mass and light extinction well. The light extinction was mainly contributed by (NH4)2SO4 and NH4NO3 (together 58.3%). Mass concentrations of all PM2.5 components increased significantly with the increase of pollution levels, but nitrate increased most rapidly; correspondingly, the contribution of nitrate to light extinction also increased quickly when pollution became heavy. Such results were different from those observed in Beijing-Tianjin-Hebei where sulfate increased most quickly. Our results thus highlight that reduction of vehicular NO2 is likely a priority for air quality improvement in Nanjing. Back trajectory analysis showed the dominance of the local air mass and the one from Huanghai, yet the air mass originated from Bohai, and passed though Shandong and north of Jiangsu province could deliver highly-polluted air to Nanjing, as well.

The surface aerosol optical properties in the urban area of Nanjing, west Yangtze River Delta, China

Abstract. Observational studies of aerosol optical properties are useful for reducing uncertainties in estimations of aerosol radiative forcing and forecasting visibility. In this study, the observed near-surface aerosol optical properties in urban Nanjing are analysed from March 2014 to February 2016. Results show that near-surface urban aerosols in Nanjing are mainly from local emissions and the surrounding regions. They have lower loadings but are more scattering than aerosols in most cities in China. The annual mean aerosol extinction coefficient (EC), single-scattering albedo (SSA) and asymmetry parameter (ASP) at 550 nm are 381.96 Mm−1, 0.9 and 0.57, respectively. The aerosol absorption coefficient (AAC) is about 1 order of magnitude smaller than its scattering coefficient (SC). However, the absorbing aerosol has a larger Ångström exponent (AAE) value, 1.58 at 470∕660 nm, about 0.2 larger than the scattering aerosols (SAE). All the aerosol optical properties follow a near-unimodal pattern, and their values are mostly concentrated around their averages, accounting for more than 60 % of the total samplings. Additionally, they have substantial seasonality and diurnal variations. High levels of SC and AAC all appear in winter due to higher aerosol and trace gas emissions. AAE (ASP) is the smallest (largest) in summer, possibly because of high relative humidity (RH) which also causes considerably larger SC and smaller SAE, although intensive gas-to-particle transformation could produce a large number of finer scattering aerosols in this season. Seasonality of EC is different from the columnar aerosol optical depth. Larger AACs appear during the rush hours of the day while SC and back-scattering coefficient (Bsp) only peak in the early morning. Aerosols are fresher in the daytime than at night-time, leading to their larger Ångström exponent and smaller ASP. Different temporal variations between AAC and SC cause the aerosols to be more absorbing (smaller SSA) in autumn, winter and around rush hours. ASP has a good quasi-log-normal growth trend with increasing SC when RH is below 60 %. The correlation between AAC and SC at the site is close but a little smaller than that in suburban Nanjing in spring. Atmospheric visibility decreases exponentially with increasing EC or SC, more sharply in spring and summer, and it could be further deteriorated with increasing SSA and ASP.

Seasonal Variations and Sources of 17 Aerosol Metal Elements in Suburban Nanjing, China

In this work, the seasonal variations and sources of trace metal elements in atmospheric fine aerosols (PM2.5) were investigated for a year-long field campaign from July 2012 to June 2013, conducted in suburban Nanjing, eastern China, at a site adjacent to an industry zone. The PM2.5 samples collected across four seasons were analyzed for 17 metal elements, namely, Sodium (Na), Magnesium (Mg), Aluminum (Al), Vanadium (V), Chromium (Cr), Manganese (Mn), Nickel (Ni), Copper (Cu), Zinc (Zn), Arsenic (As), Selenium (Se), Strontium (Sr), Cadmium (Cd), Barium (Ba), Lead (Pb), Molybdenum (Mo), and Antimony (Sb) using an inductively coupled plasma mass spectrometry (ICP-MS). We found that the total concentration of all 17 metal elements was 1.23 μg/m3, on average accounting for 1.0% of the total PM2.5 mass. For our data, mass concentrations of Al, Cd, Ba were highest in summer, Mg, Cu, Zn, Se, Pb peaked in autumn, Cr, Mn, Ni, As, Sr, Sb increased significantly in winter, while the concentrations of Na, V, Mo were at their highest levels in spring. Air mass back trajectory analysis suggested that air parcels that arrived at the site originated from four dominant regions (Japan, yellow sea and bohai; Southeast of China, the Pacific Ocean; Southwest of Jiangsu and Anhui province; Northern Asia inland and Mongolia region), in particular, the one from Northern Asia inland and Mongolia contained the highest concentrations of As, Sb, Sr, and was predominant in winter. Positive matrix factorization (PMF) analyses revealed that the industrial emission is the largest contributor (34%) of the observed metal elements, followed by traffic (25%), soil dust (19%), coal combustion (10%), incineration of electronic waste (9%), and a minor unknown source (3%). In addition, we have also investigated the morphology and composition of particles by using the scanning electron microscopy (SEM)/energy-dispersive spectrometry (EDS) techniques, and identified particles from coal burning sources, etc., similar to the PMF results.

Dualities of semi-urbanization villages in social-spatial transition: A case study of Zhoucun village in suburban Nanjing, China

In contrast with the classical topics of poverty and exclusion of rural areas, the multiple dualities in the social-spatial dimension of villages in semi-urbanized suburbs of China’s large cities have received little attention to date. As this paper demonstrates, such dualities have emerged during China’s rapid urbanization since the early 2000s. It is firstly argued that these dual characteristics are derived from the institutional separation of urban and rural entitlements (e.g., hukou, welfare, land property ownership etc.). These distinctions are then projected into social capital differentiation, such as the division between the strong and weak ties of local community residents. Consequentially, the dualities are embodied in the residential space segregation between established residents and rural migrants that is divided into Houses in Single-Family Occupancy (HSFOs) and Houses in Multiple-Family Occupancy (HMFOs). To support these claims, a case study of the village of Zhoucun, a southern suburb of the Nanjing Metropolitan Area on the east coast China, is used. This draws on both quantitative and qualitative data that includes interviews with authorized officers from local government to municipal government, and a questionnaire survey and interviews with both the HSFO and HMFO residents themselves.