Quantifying Air Pollutant Variations during COVID-19 Lockdown in a Capital City in Northwest China

In the context of the outbreak of coronavirus disease 2019 (COVID-19), strict lockdown policies were implemented to control nonessential human activities in Xi’an, northwest China, which greatly limited the spread of the pandemic and affected air quality. Compared with pre-lockdown, the air quality index and concentrations of PM2.5, PM10, SO2, and CO during the lockdown reduced, but the reductions were not very significant. NO2 levels exhibited the largest decrease (52%) during lockdown, owing to the remarkable decreased motor vehicle emissions. The highest K+ and lowest Ca2+ concentrations in PM2.5 samples could be attributed to the increase in household biomass fuel consumption in suburbs and rural areas around Xi’an and the decrease in human physical activities in Xi’an (e.g., human travel, vehicle emissions, construction activities), respectively, during the lockdown period. Secondary chemical reactions in the atmosphere increased in the lockdown period, as evidenced by the increased O3 level (increased by 160%) and OC/EC ratios in PM2.5 (increased by 26%), compared with pre-lockdown levels. The results, based on a natural experiment in this study, can be used as a reference for studying the formation and source of air pollution in Xi’an and provide evidence for establishing future long-term air pollution control policies.

Honeycomb-Shaped Brass Plate Catalyst to Reduce Motor Vehicle Emissions

The increasing number of motorized vehicles has a direct impact on exhaust gas air pollution. The air pollution in urban areas is dominated by motorized vehicle emissions, along with pollution problems. This study aims to reduce motor vehicle emissions by using a catalytic converter design made from a brass plate catalyst in the shape of a honeycomb. Honeycomb-shaped brass is suitable for catalysts in the catalytic converter. Besides being easy to obtain and cheap in price, the catalyst can reduce and oxidize exhaust gases well, making it suitable as a catalyst material. The method used in this research is the experimental method. It is started from the design of the catalytic converter house and determining the type of catalyst to the process of making the catalytic converter with a honeycomb-shaped brass plate. Then, testing to determine the emission of exhaust gases produced is required. The last step is to compare it without using a catalytic converter or standard conditions. From the results of the emission test, it was found that the use of a catalytic converter made from a brass plate catalyst in the shape of a honeycomb can reduce HC and CO emissions, while CO2 emissions have increased. A decrease in HC gas emissions by 19.1% for a single catalytic converter and 33.7% for a dual catalytic converter is better compared to without using a catalytic converter or standard conditions. Reduced CO gas emissions by 23.8% for a single catalytic converter and 43.1% for a dual catalytic converter are compared to without using a catalytic converter. Meanwhile, CO2 gas emissions increased by 60.7% for a single catalytic converter, and 81.6% for multiple catalytic converters are compared without using a catalytic converter. This is a result of the addition of oxygen to the oxidation process that running smoothly.

Mass Effect of Coconut Shell-derived Activated Carbon on Adsorption of Benzene, Toluene, Ethylbenzene, and Xylene in Motorcycle Emissions

The use of motorized transportation in Indonesia is now proliferating. The higher the use of motorized vehicle-based transportation in an area, the higher the potential for air pollution. One of the air pollutants is a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX). This study examines the effect of coconut shell-derived activated carbon adsorbent mass which is adjusted with different thicknesses on its adsorption ability for BTEX. The adsorbent is used to adsorb the emissions of the 1990 GL-Pro motorcycle with premium fuel. The results of gas chromatography-mass spectroscopy (GC-MS) show that motor vehicle emissions contain BTEX and other hydrocarbons. ANOVA variant analysis showed that the difference in mass of activated carbon in the range of this study did not provide a significant difference in BTEX adsorption.Keywords: adsorbent; motor vehicle emissions; BTEX pollutants; coconut shell

Variability in Observation-Based Onroad Emission Constraints from a Near-Road Environment

This study uses Las Vegas near-road measurements of carbon monoxide (CO) and nitrogen oxides (NOx) to test the consistency of onroad emission constraint methodologies. We derive commonly used CO to NOx ratios (∆CO:∆NOx) from cross-road gradients and from linear regression using ordinary least squares (OLS) regression and orthogonal regression. The CO to NOx ratios are used to infer NOx emission adjustments for a priori emissions estimates from EPA’s MOtor Vehicle Emissions Simulator (MOVES) model assuming unbiased CO. The assumption of unbiased CO emissions may not be appropriate in many circumstances but was implemented in this analysis to illustrate the range of NOx scaling factors that can be inferred based on choice of methods and monitor distance alone. For the nearest road estimates (25 m), the cross-road gradient and ordinary least squares (OLS) agree with each other and are not statistically different from the MOVES-based emission estimate while ∆CO:∆NOx from orthogonal regression is significantly higher than the emitted ratio from MOVES. Using further downwind measurements (i.e., 115 m and 300 m) increases OLS and orthogonal regression estimates of ∆CO:∆NOx but not cross-road gradient ∆CO:∆NOx. The inferred NOx emissions depend on the observation-based method, as well as the distance of the measurements from the roadway and can suggest either that MOVES NOx emissions are unbiased or that they should be adjusted downward by between 10% and 47%. The sensitivity of observation-based ∆CO:∆NOx estimates to the selected monitor location and to the calculation method characterize the inherent uncertainty of these methods that cannot be derived from traditional standard-error based uncertainty metrics.

Inventarisasi Emisi Pencemar Kriteria dan Gas Rumah Kaca dari Sektor Transportasi On-Road di Kota Bandung menggunakan Model International Vehicle Emissions (IVE)

AbstrakPerkembangan Kota Bandung berimplikasi terhadap pesatnya pertumbuhan aktivitas transportasi. Akibatnya, terjadi peningkatan emisi kendaraan bermotor secara kontinu. Penelitian ini bertujuan untuk mengestimasi beban emisi pencemar kriteria dan gas rumah kaca dari sektor transportasi on-road di Kota Bandung, khususnya untuk truk. Estimasi beban emisi diperoleh dari hasil simulasi model IVE untuk menghasilkan faktor emisi lokal komposit disertai dengan pembaruan pada jumlah registrasi seluruh jenis kendaraan di Kota Bandung. Beban emisi total tahunan paling dominan yang dihasilkan dari aktivitas transportasi di Kota Bandung tahun 2019 yakni 5.286.612,81 ton/tahun (94,48%) CO2; 254.378,9 ton/tahun (4,55%) CO; dan 35.501,65 ton/tahun (0,63%) NOx dengan kontribusi terbesar berasal dari (98,9%) emisi running. Moda transportasi yang menyumbang proporsi emisi total terbesar berasal dari 43,4% mobil pribadi, 27,8% truk, 17,1% sepeda motor, dan 10,1% berasal dari bus.Kata kunci: Aktivitas Transportasi, Model International Vehicle Emissions (IVE), Beban EmisiAbstractThe development of Bandung city has affected the level of community mobilization needs, which has implications for the rapid growth of transportation activities. As a result, an increase in motor vehicle emissions continues to have an impact on decreasing air quality in Bandung city. This study aims to estimate emission load of criteria pollutant and greenhouse gases from the on-road transportation sector, especially for trucks. Emission load estimates are obtained from the results of the IVE model simulation to generate composite local emission factors accompanied by updates on current registration numbers of vehicles in Bandung city. The most dominant total annual emission load generated from all type of fleets in Bandung city in 2019 was 5,286,612.81 tons/year (94.48%) CO2; 254,378.9 tons/year (4.55%) CO; and 35,501.65 tons/year (0.63%) NOx, with the largest contribution coming from running emissions. Major transportation modes that accounted for the largest proportion of total emissions came from 43.4% of private cars, 27.8% of trucks, 17.1% of motorbikes and 10.1% of buses. Keywords: Transportation Activities, International Vehicle Emissions (IVE) Model, Emission Load

Optical source apportionment and radiative forcing of light-absorbing carbonaceous aerosol at a tropical marine monsoon climate zone: the importance of ship emissions

Source-specific optical properties of light-absorbing carbonaceous (LAC) aerosol are poorly understood owing to its various sources in the atmosphere. Here, a receptor model coupling multi-wavelength absorption with chemical species was utilized to explore the source-specific LAC optical properties at a tropical marine monsoon climate zone. Results showed that biomass burning contributed the largest to LAC absorption on average, but ship emissions became the dominant contributor (44–45 %) when the air masses originated from the South China Sea. The source-specific absorption Ångström exponent indicates that black carbon (BC) was the dominant LAC aerosol in ship and motor vehicle emissions while there was also brown carbon (BrC) existed in biomass-burning emissions. The source-specific mass absorption cross section (MAC) showed that BC from ship emissions had a stronger light-absorbing capacity than biomass burning and motor vehicle emissions. The BrC MAC derived from biomass burning was smaller than BC MAC and highly depended on wavelengths. Radiative effect assessment indicates a comparable atmospheric forcing and heating capacity of LAC aerosol from biomass burning and ship emissions. Our study provides insights into the optical properties of LAC aerosol from various sources and can improve our understanding of the LAC radiative effects caused by ship emissions.