Observation and Source Apportionment of Atmospheric Alkaline Gases in Urban Beijing.

Alkaline gases, including NH3, C1-3-amines, C1-3-amides, and C1-3-imines, were measured in situ using a water cluster-CIMS in urban Beijing during the wintertime of 2018, with a campaign average of 2.8 ± 2.0 ppbv, 5.2 ± 4.3, 101.1 ± 94.5, and 5.2 ± 5.4 pptv, respectively. Source apportionment analysis constrained by emission profiles of in-use motor vehicles was performed using a SoFi-PMF software package, and five emission sources were identified as gasoline-powered vehicles (GV), diesel-powered vehicles (DV), septic system emission (SS), soil emission (SE), and combustion-related sources (CS). SS was the dominant NH3 source (60.0%), followed by DV (18.6%), SE (13.1%), CS (4.3%), and GV (4.0%). GV and DV were responsible for 69.9 and 85.2% of C1- and C2-amines emissions, respectively. Most of the C3-amines were emitted from nonmotor vehicular sources (SS = 61.3%; SE = 17.8%; CS = 9.1%). DV accounted for 71.9 and 34.1% of C1- and C2-amides emissions, respectively. CS was mainly comprised of amides and imines, likely originating from the pyrolysis of nitrogen-containing compounds. Our results suggested that motor vehicle exhausts can not only contribute to criteria air pollutants emission but also promote new particle formation, which has not been well recognized and considered in current regulations. Urban residential septic system was the predominant contributor to background NH3. Enhanced NH3 emissions from soil and combustion-related sources were the major cause of PM2.5 buildup during the haze events. Combustion-related sources, together with motor vehicles, were responsible for most of the observed amides and imines and may be of public health concern within the vicinity of these sources.

Inhalable microorganisms in Beijing's PM2.5 and PM10 pollutants during a severe smog event.

Particulate matter (PM) air pollution poses a formidable public health threat to the city of Beijing. Among the various hazards of PM pollutants, microorganisms in PM2.5 and PM10 are thought to be responsible for various allergies and for the spread of respiratory diseases. While the physical and chemical properties of PM pollutants have been extensively studied, much less is known about the inhalable microorganisms. Most existing data on airborne microbial communities using 16S or 18S rRNA gene sequencing to categorize bacteria or fungi into the family or genus levels do not provide information on their allergenic and pathogenic potentials. Here we employed metagenomic methods to analyze the microbial composition of Beijing's PM pollutants during a severe January smog event. We show that with sufficient sequencing depth, airborne microbes including bacteria, archaea, fungi, and dsDNA viruses can be identified at the species level. Our results suggested that the majority of the inhalable microorganisms were soil-associated and nonpathogenic to human. Nevertheless, the sequences of several respiratory microbial allergens and pathogens were identified and their relative abundance appeared to have increased with increased concentrations of PM pollution. Our findings may serve as an important reference for environmental scientists, health workers, and city planners.

Significant reduction in air pollutant emissions from household cooking stoves by replacing raw solid fuels with their carbonized products.

Residential solid fuel combustion contributes significantly to ambient and indoor air pollutions. An appropriate clean solid fuel to reduce residential emissions is urgently needed. This study evaluates the reduction in pollutant emissions achieved by carbonized solid fuels in residential cooking practice. Four biochar samples, three semi-coke briquette samples and their raw materials were tested in a typical cooking stove. These carbonized samples showed higher thermal efficiencies and lower particulate matter (PM) emission factors (EFs) than their raw material samples. Owing to distilled volatile matter during carbonization treatment, average energy delivered-based PM2.5 EFs were 10 ±â€¯5 mg/kJ (carbonized) and 50 ±â€¯28 mg/kJ (raw) for the biomass and 0.33 ±â€¯0.04 mg/kJ (carbonized) and 3.0 ±â€¯1.3 mg/kJ (raw) for the coal samples. The energy delivered-based EFs of organic carbon, elemental carbon, and 16 priority polycyclic aromatic hydrocarbons extracted from PM2.5 samples from carbonized fuels were reduced by 97 ±â€¯1%, 93 ±â€¯3%, and 97 ±â€¯2%, respectively, for the tested biomass samples, and those for the tested coal samples were 96 ±â€¯1%, 90 ±â€¯6%, and 98 ±â€¯2%, respectively. Average EFs of benzo[a]pyrene equivalent carcinogenic potency for individual polycyclic aromatic hydrocarbons were reduced 95 ±â€¯3% to ~0.51 µg/kJ (carbonized) from ~19.6 µg/kJ (raw). Furthermore, the average ratio of volatile organic compounds contained in PM2.5 samples was also reduced from 38.8 ±â€¯5.4% to 7.1 ±â€¯3.9%. These results suggest that carbonized solid fuels exhibit better performance in reducing carcinogenic potency and pollutants, most of which are highly correlated with the volatile matter content of the fuel. Switching from raw solid fuel to carbonized solid fuel will help to reduce pollutant emissions from household combustion and achieve both environmental benefits and health benefits for household residents.

Influence of flue gas desulfurization (FGD) installations on emission characteristics of PM2.5 from coal-fired power plants equipped with selective catalytic reduction (SCR).

Flue gas desulfurization (FGD) and selective catalytic reduction (SCR) technologies have been widely used to control the emissions of sulphur dioxide (SO2) and nitrogen oxides (NOX) from coal-fired power plants (CFPPs). Field measurements of emission characteristics of four conventional CFPPs indicated a significant increase in particulate ionic species, increasing PM2.5 emission with FGD and SCR installations. The mean concentrations of PM2.5 from all CFPPs tested were 3.79 ± 1.37 mg/m3 and 5.02 ± 1.73 mg/m3 at the FGD inlet and outlet, respectively, and the corresponding contributions of ionic species were 19.1 ± 7.7% and 38.2 ± 7.8%, respectively. The FGD was found to enhance the conversion of NH3 slip from the SCR to NH4+ in the PM2.5, together with the conversion of SO2 to SO42-, and increased the primary NH4+ and SO42- aerosol emissions by approximately 18.9 and 4.2 times, respectively. This adverse effect should be considered when updating the emission inventory of CFPPs and should draw the attention of policy-makers for future air pollution control.

[Estimate the mercury emissions from non-coal sources in China].

Based on the activity level and emission factors, we estimated the provincial mercury emissions from non-coal sources during the period of 1995 -2003 in China. In the year of 2003, non-coal mercury emissions in China reached 393 tonnes, which was 137 tonnes more than the emissions from coal combustion. Approximately 84 % of the non-coal mercury emissions came from nonferrous metals smelting. The zinc production, lead production, copper production and gold production contributed respectively 51%, 18%, 4% and 11% of total non-coal mercury emissions. The shares of elemental mercury (Hg0), oxidized mercury (Hg2+ ) and particulate mercury (HgP) were 77 % , 18 % and 5 % , respectively. The mercury emissions from non-coal sources in provinces including Hunan, Henan and Yunnan exceeded 30 t x a(-1). The emission intensity of Shanghai, Hunan, Henan and Liaoning exceeded 100 g x (km(2)xa)(-1). Main emission sources in these provinces are nonferrous metals smelting and household waste burning. Mercury emissions from non-coal sources in China increased averagely 9 percent from 1995 to 2003, and the household waste burning increased extremely fast, with an average increase rate of 42 percent.