Hongjun Mao

Health burden attributable to ambient PM2.5 in China

In China, over 1.3 billion people have high health risks associated with exposure to ambient fine particulate matter (PM2.5) that exceeds the World Health Organization (WHO) Air Quality Guidelines (AQG). The PM2.5 mass concentrations from 1382 national air quality monitoring stations in 367 cities, between January 2014 and December 2016, were analyzed to estimate the health burden attributable to ambient PM2.5 across China. The integrated exposure-response model was applied to estimate the relative risks of disease-specific mortality. Disease-specific mortality baselines in province-level administrative units were adjusted by the national mortality baseline to better reveal the spatial inequality of the health burden associated with PM2.5. Our study suggested that PM2.5 in 2015 contributed as much as 40.3% to total stroke deaths, 33.1% to acute lower respiratory infection (ALRI, <5yr) deaths, 26.8% to ischemic heart disease (IHD) deaths, 23.9% to lung cancer (LC) deaths, 18.7% to chronic obstructive pulmonary disease (COPD) deaths, 30.2% to total deaths combining IHD, stroke, COPD, and LC, 15.5% to all cause deaths. The population weighted average (PWA) attributable mortality rates (10-5 y-1) were 112.0 in current year analysis, and 124.3 in 10-year time lag analysis. The Mortality attributable to PM2.5 in 10-year time lag analysis (1.7 million) was 12% higher than the current year analysis (1.5 million). Our study also estimated site-specific annual PM2.5 concentrations in scenarios of achieving WHO interim targets (ITs) and AQG. The mortality benefits will be 24.0%, 44.8%, 70.8%, and 85.2% of the total current mortalities (1.5 million) when the PWA PM2.5 concentrations in China meets the WHO IT-1, IT-2, IT-3, and AQG, respectively. We expect air quality modeling and cost-benefits analysis of emission reduction scenarios and corresponding health benefits in meeting the site-specific annual PM2.5 concentrations (WHO IT-1, IT-2, IT-3, and AQG) this study raised.

Long-term exposure to urban air pollution and lung cancer mortality: A 12-year cohort study in Northern China.

Cohort evidence that links long-term exposures to air pollution and mortality comes largely from the United States and European countries. We investigated the relationship between long-term exposures to particulate matter <10μm in diameter (PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2) and mortality of lung cancer in Northern China. A cohort of 39,054 participants were followed during 1998-2009. Annual average concentrations for PM10, NO2, and SO2 were determined based on data collected from central monitoring stations. Lung cancer deaths (n=140) were obtained from death certificates, and hazard ratios (HRs) were estimated using Cox proportional hazards models, adjusting for age, gender, BMI, education, marital status, smoking status, passive smoking, occupation, alcohol consumption, etc. Each 10mg/m(3) increase in PM10 concentrations was associated with a 3.4%-6.0% increase in lung cancer mortality in the time-varying exposure model and a 4.0%-13.6% increase in the baseline exposure model. In multi-pollutant models, the magnitude of associations was attenuated, most strongly for PM10. The association was different in men and women, also varying across age categories and different smoking status. Substantial differences exist in the risk estimates for participants based on assignment method for air pollution exposure.

Numerical Model-Based Artificial Neural Network Model and Its Application for Quantifying Impact Factors of Urban Air Quality

Knowledge of the relationship between air quality and impact factors is very important for air pollution control and urban environment management. Relationships between winter air pollutant concentrations and local meteorological parameters, synoptic-scale circulations and precipitation were investigated based on observed pollutant concentrations, high-resolution meteorological data from the Weather Research and Forecast model and gridded reanalysis data. Artificial neural network (ANN) model was developed using a combination of numerical model derived meteorological variables and variables indicating emission and circulation type variations for estimating daily SO2, NO2, and PM10 concentrations over urban Lanzhou, Northwestern China. Results indicated that the developed ANN model can satisfactorily reproduce the pollution level and their day-to-day variations, with correlation coefficients between the modeled and the observed daily SO2, NO2, and PM10 ranging from 0.71 to 0.83. The effect of four factors, i.e., synoptic-scale circulation type, local meteorological condition, pollutant emission variation, and wet removal process, on the day-to-day variations of SO2, NO2, and PM10 was quantified for winters of 2002–2007. Overall, local meteorological condition is the main factor causing the day-to-day variations of pollutant concentrations, followed by synoptic-scale circulation type, emission variation, and wet removal process. With limited data, this work provides a simple and effective method to identify the main factors causing air pollution, which could be widely used in other urban areas and regions for urban planning or air quality management purposes.

Gasoline aromatic: a critical determinant of urban secondary organic aerosol formation

19 Gasoline vehicle exhaust is an important contributor to secondary organic aerosol (SOA) 20 formation in urban atmosphere. Fuel composition has potentially considerable impact on 21 gasoline SOA production, but the link between fuel components and SOA production is still 22 poorly understood. Here, we present chamber experiments to investigate the impacts of 23 gasoline aromatic content on SOA production through chamber oxidation approach. A 24 significant amplification factor of 3 6 for SOA productions from gasoline exhausts is 25 observed as gasoline aromatic content rose from 29% to 37%. Considerably higher emission 26 of aromatic volatile organic compounds (VOCs) using high-aromatic fuel plays an essential 27 role in the SOA production enhancement, while the semi volatile organic compounds (e.g., 28 gas-phase PAHs) may also contribute to the higher SOA production. Our findings indicate 29 that gasoline aromatics significantly influence ambient PM2.5 concentration in urban area and 30 highlight that more stringent regulation on gasoline aromatic content will achieve unexpected 31 benefit on urban air quality. 32 33

Emission factors of volatile organic compounds (VOCs) based on the detailed vehicle classification in a tunnel study

In order to obtain VOCs emission characteristics and emission factors from vehicle, a tunnel experiment was conducted in the Fu Gui Mountain Tunnel in Nanjing, China. The tunnel is located in the middle of city, with total length of 480m and speed limit of 50km/h. The studied vehicle fleet was composed of 87% light duty vehicles and 13% heavy duty vehicles (liquefied natural gas bus, LNGB). The emerging radio frequency identification (RFID) technology was used to divide fine vehicles type including China I, China II, China III, China IV, China V and LNGB. Ambient air samples (4-h averages) were collected inside the tunnel using 3.2L stainless-steel canisters. Samples collected in the canisters were analyzed for 97 individual VOCs using high-resolution GC-MS in the laboratory. The average tunnel emission factor for the collective light-duty vehicles was 160.79±65.94mg/(km∗veh), and for the China I, China II, China III, China IV and China V vehicles, it was 632.07±259.44, 450.35±184.85, 205.42±84.32, 118.51±48.65, and 110.61±45.4mg/(km∗veh), respectively. The average emission factor for heavy-duty vehicles was 358.02±124.86mg/(km∗veh). Ethane, isopentane, propane, ethylene, toluene, propylene and 2,3-dimethylbutane were the most common VOC species in vehicle emissions. The total O3 formation potential was 373.88mg∗O3/(km∗veh) in the tunnel. Ethylene, propylene, m/p-xylene, toluene, and isopentane were the largest contributors to O3 production. Compared with previous studies, fuel quality increased from China II-FQ to China IV-FQ levels, while the BTEX emission levels exhibited a decreasing trend.

Occurrence of benzothiazole and its derivates in tire wear, road dust, and roadside soil

Benzothiazole (BT) and its derivates are commonly used as vulcanization accelerators in rubber production. Information on the occurrence of BTs in road dust (RD) and on human exposure to these compounds is very limited. BT and its six derivates in tire wear particles (TWPs) and RD were determined in this study. Samples were extracted using solid-liquid extraction, purified by a HLB SPE column, and determined by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). All seven BTs were found in 17 TWPs samples from different tire brands. The mass fractions of all seven BTs (∑BTs) in TWPs ranged from 46.93 to 215 μg/g with an average concentration of 99.32 μg/g. Benzothiazole and 2-hydroxybenzothiazole (2-OH-BT) were the two major compounds, accounting for 56%-89% of the total. The seven BTs were also found in all 36 sets of RD samples (each set included one sample of TSP (particles < 75 μm in diameter), PM10 (particles < 10 μm in diameter) and PM2.5 (particles < 2.5 μm in diameter)) fractions of RD. The median ∑BTs concentration was highest in PM2.5 (26.62 μg/g), followed by PM10 (22.03 μg/g), and TSP (0.68 μg/g). Of the seven BTs, BT, 2-aminobenzothiazole (2-NH2-BT), 2-mercaptobenzothiazole (MBT), and 2-(methylthio)benzothiazole (MTBT) were distributed in PM2.5 and 2-OH-BT was distributed in PM2.5-10 of RD. Based on the mass fractions of BTs in the TSP, PM10, and PM2.5 fractions of RD, human exposure via ingestion, inhalation and dermal absorption were evaluated. Ingestion was found to be the main exposure pathway in humans, and daily intake of BTs in PM2.5 was highest, followed by PM10 and TSP, respectively. Children may suffer more health risks than adults when exposed to RD.

Evaluation of the potential of pelletized biomass from different municipal solid wastes for use as solid fuel

Four different municipal solid wastes (dog manure, horse manure, apple pomace waste and tea waste) and an industrial by-product (NovoGro) were used to produce solid fuel pellets. The mixtures followed a raw material to NovoGro ratio of 50:1. The pellets diameters varied between 4 and 5 mm, and the average length was 20 mm. The dog manure, horse manure, apple pomace waste and tea waste pellets were denoted as DN, HN, AN and TN, respectively. The combustion characteristics of the pelletized fuels were investigated, such as total moisture, ash content, calorific value and ash fusion point, etc. The physicochemical properties were analyzed by using a number of analytical techniques including X-ray fluorescence spectrometry (XRF), X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results of the mechanical, thermal and morphological properties show that the raw materials were effectively combined with the NovoGro binder; furthermore, the DN, HN and TN pellets exhibited excellent mechanical and thermal properties, including high calorific values (>16.30 MJ/kg), high resistance to mechanical shock (>99%), high volatile matter contents, optimal softening temperatures and optimal ash contents. However, the high K, Ca, and Si contents of the AN can form low-melting-point eutectics, which can cause slagging. Moreover, the AN materials had large particle sizes, and high cellulose and hemicellulose contents led to high total moistures, low softening temperatures and low calorific values. The AN was not suitable for use as a fuel. The results suggested that NG is an effective binder for pelletization of biomass and showed the feasibility of using municipal solid wastes for energy production.

Numerical simulation of the impact of reforestation on winter meteorology and environment in a semi-arid urban valley, Northwestern China.

Since 1999 Chinese government has made great effort to reforest the south and north mountains surrounding urban Lanzhou - a city located in a river valley, Northwestern China. Until 2009 obvious land use change occurred, with 69.2% of the reforested area been changed from grasslands, croplands, barren or sparsely vegetated land to closed shrublands and 20.6% from closed shrublands, grasslands, and croplands to forests. Reforestation changes land-surface properties, with possible impact on the evolution of atmospheric variables. To understand to what extent the local meteorology and environment could be affected by reforestation in winter, and through what processes, two sets of simulations were conducted using the Weather Research and Forecasting model (WRF) and the FLEXible PARTicle (FLEXPART) dispersion model for a control case with high-resolution remotely sensed land cover data for 2009 and a scenario assuming no reforestation since 1999. Results suggested that the changes in albedo, surface exchange coefficient and surface soil heat conductivity related to reforestation led to the changes in surface net radiation and surface energy partitioning, which in turn affected the meteorological fields and enhanced the mountain-valley wind circulation. Replacement of shrublands and grassland with forest in the south mountain through reforestation play a dominant role in the enhancement of mountain-valley wind circulation. Reforestation increased the amount of air exchanged between the valley and the outside during the day, with the largest hourly increase of 10% on calm weather days and a monthly mean hourly increase of 2% for the study period (Dec. 2009). Reforestation affected the spatial distribution of pollutants and slightly improved the urban air quality, especially in the eastern valley. Results from this study provide useful information for future urban air quality management and reforestation plan, and some experience for cities with similar situations in the world.

Development and Application of Urban High Temporal-Spatial Resolution Vehicle Emission Inventory Model and Decision Support System

This paper reports on the development and application of an urban high temporal-spatial resolution vehicle emission inventory model and decision support system based on the current situation in China and actual vehicle emission control requirements. The system incorporates a user-friendly modular architecture that integrates a vehicle emission model and a decision support platform and includes scenario analysis and visualisation capabilities. A bottom-up approach based on localised emission factors and actual on-road driving condition has been adopted to develop the system. As a case study of application and evaluation, an emission reduction effect analysis of the supposed low-emission zone (LEZ) policy in Beijing (2012) was conducted. According to the simulated results in the forms of tables, histograms and grid maps, the establishment of this LEZ had a definite effect on the emission reduction of various types of air pollutants, especially carbon monoxide and hydrocarbon. In the system, the simulation methodology for identifying environmental benefits brought by the LEZ policy could be used to assess other similar environmental policies. Through flexible modification of configuration values or input data variables, the efficacy of separate or joint policies could be quantifiably evaluated and graphically displayed.

Research on biochar via a comprehensive scientometric approach

A comprehensive statistical study related to biochar was conducted by using the scientometric method. The publications are mainly in the form of articles (over 16 000), accounting for 87.7% of the total, which demonstrates that researchers have great interest in this research field. Among these articles, 96.8% were written and published in English and came from 2655 different journals. The rate of increase in the annual number of publications was rapid from 2010 to 2017, and it was predicted that the cumulative number of articles concerning biochar will exceed 20 000 by the year 2020. At least one article from 154 countries or regions has been published, and every continent except Antarctica has had articles published over the past 20 years period. The percentage of collaborative articles was 71.9% and the collaboration between the USA and China has been the most fruitful. In addition, the Chinese Academy of Sciences is the research institute with the most publications. Furthermore, over 60% of the articles were published as a result of the cooperation and connection between the Chinese Academy of Sciences and the University of Chinese Academy of Sciences. The article published in Nature had the highest citation numbers, while Environmental Science & Technology had the most articles (4) that were selected as the top 20 for the most-cited articles. The agriculture research category had the highest average citations among the top four categories (i.e., environmental sciences and ecology, agriculture, chemistry and engineering).