Study on Short-lived Climate Pollutants in Hanoi in the Context of Climate Change and Sustainable Development

Overview: BC and PM 2.5 variations were similar with each other, while features of TO 3 variation did not always agree with them. Their concentrations varied with season o[r]

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

DO DUY TUNG

STUDY ON SHORT-LIVED CLIMATE POLLUTANTS IN HANOI

IN THE CONTEXT OF CLIMATE

CHANGE AND SUSTAINABLE

DEVELOPMENT

MASTER’S THESIS

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

DO DUY TUNG

STUDY ON SHORT-LIVED CLIMATE POLLUTANTS IN HANOI

IN THE CONTEXT OF CLIMATE

CHANGE AND SUSTAINABLE

i

PLEDGE

In writing Master’s thesis, I carefully read the thesis guidelines at Vietnam Japan University, Vietnam National University and fully understand what is written there and comply with all related rules and guidelines I ensure that this thesis is my own research and has not been published The use of results of other research and documents must comply with the regulations Citations and references for documents, books, research papers and web pages must be on the list of references

of the thesis

I pledge my honor that I comply with provisions give above

Author of the thesis

Do Duy Tung

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TABLE OF CONTENTS

PLEDGE i

LIST OF TABLES iv

LIST OF FIGURES v

LIST OF ABBREVIATIONS vii

ACKNOWLEDGEMENT viii

ABSTRACT ix

CHAPTER 1 BACKGROUND AND OBJECTIVES 1

1.1 Definition of SLCPs and their significance 2

1.2 Definition of BC, TO3 and PM2.5 and their significance 8

1.2.1 BC 8

1.2.2 TO 3 .10

1.2.3 PM 2.5 .12

1.3 Preceding Studies: Status of SLCPs in Vietnam and Southeast Asia 13

1.4 Mitigation measures to reduce SLCPs in Vietnam and SE Asia 21

1.5 SLCPs’ sources in Vietnam 22

1.6 Objectives of this study 24

CHAPTER 2 METHODOLOGY AND STRATEGY IN THIS STUDY 25

2.1 Strategy to attain the objectives 26

2.2 Ground-based Observation 28

2.2.1 BC 29

2.2.2 Tropospheric Ozone 31

2.2.3 PM2.5 34

2.3 Signatures indicating contributions of local/regional/remote sources 36

2.3.1 Diurnal variation 36

2.3.2 Correlation of observed SLCP concentration levels with the trajectory and local meteorological parameters 37

2.4 Remote Observational Sites 41

2.4.1 Initial Data Processing 41

2.4.2 Observational Data Provided by Other Activities 41

2.5 Meteorological Data and Trajectory Analysis 42

2.5.1 HYSPLIT Trajectory Model 42

2.5.2 Local Meteorological Data 42

CHAPTER 3 RESULTS 43

3.1 Observed SLCPs’ Concentrations and Their Variation 43

3.1.1 Winter 45

3.1.2 Spring 47

3.1.3 Summer 48

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3.1.4 Autumn 49

3.2 Seasonal Features of Trajectories 53

CHAPTER 4 ANALYSIS AND DISCUSSION 55

4.1 Correlation between SLCPs in each season 55

4.1.1 BC and PM2.5 55

4.1.2 PM2.5 and TO3 57

4.2 Comparison of Observed Enhances of SLCP with the Transport Areas in each season 59

4.2.1 Winter 60

4.2.2 Spring 62

4.2.3 Summer 62

4.2.4 Autumn 63

4.3 Comparison of Observed Enhances of SLCP with the local / regional transport features 64

4.4 Comparison of Multi-station Observational Data 65

4.5 Discussion on contribution of local/regional sources in Northern Vietnam and on the inference of SLCP Climate Effect in this region 67

4.5.1 Contribution of local/regional sources in Northern Vietnam 67

4.5.2 Climate Effects of BC 67

CHAPTER 5 CONCLUSION 66

REFERENCES 67

APPENDIX 70

iv

LIST OF TABLES

Table 1.1 Key features of SLCPs compared with CO2 6

Table 2.1 Diurnal Analysis of BC, O3 and PM2.5 concentration in Hanoi 39 Table 2.2.2 Evidences for distinguishing local/remote source influences 40

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LIST OF FIGURES

Figure 1.1 Critical air polluted condition in Hanoi by open biomass burning 1 Figure 1.2 Global annual mean distribution of BC direct radiative forcing at TOA 3 Figure 1.3 Radiative Forcing Caused by Human Activities Since 1750 3 Figure 1.4 Model of CO2 and SLCP cuts compared with other pathways until 2100 4

Figure 1.5 Dominant sources of BC from human activities 9 Figure 1.6 Schematic Display of Photochemical Ozone Formation in the

Troposphere 10

Figure 1.7 Diagram shows PM2.5 particles size 12

Figure 1.8 Planetary boundary layer (PBL) heating by surface emission of BC 15 Figure 1.9 Monthly mean BC mass concentration (left) and heating rate (right)

over Ahmedabad in 2008 16

Figure 1.10 Vertical profiles of heating rate due to aerosol black carbon calculated

from FBC profiles 17

Figure 1.11 Annual mean model median change in near-surface temperature (top

left), zonally averaged temperature change for the model median (black line) and individual models (top right) .18

Figure 2.1 Initial strategy of research activities in this study 26 Figure 2.2 Updated strategy to attain objectives of this study 28 Figure 2.3 Schematic diagram of Particle Soot Absorption Photometer (PSAP) 30 Figure 2.4 Flowrate calibration in PSAP 30 Figure 2.5 Schematic diagram of dual-beam UV-absorption ozone photometer 32 Figure 2.6 Schematic diagrams of the newly developed PM2.5 sensor: 34 Figure 2.7 PM2.5 optical sensor calibration 35

Figure 2.8 Three typical patterns of BC, O3 and PM2.5 concentration in Hanoi 36 Figure 2.9 Local, regional and remote sources to Hanoi 39 Figure 2.10 Screenshot of monitoring portal of CEM website

http://enviinfo.cem.gov.vn/ 41

Figure 2.11 Screenshot of monitoring portal of AQICN website http://aqicn.org/ 42 Figure 3.1 Monthly average of BC, PM2.5 and TO3 in Hanoi in 2019 44 Figure 3.2 Timeseries of BC, TO3 and PM2.5 in Hanoi associated with

meteorological data in winter 2019 47

Figure 3.3 Timeseries of BC, TO3 and PM2.5 in Hanoi associated with

meteorological data in spring 2019 48

Figure 3.4 Timeseries of BC, TO3 and PM2.5 in Hanoi associated with

meteorological data in summer 2019 49

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Figure 3.5 Timeseries of BC, TO3 and PM2.5 in Hanoi associated with

meteorological data in autumn 2019 49

Figure 3.6 Hourly concentration of PM2.5, BC and O3 in Hanoi 51

Figure 3.7 PM2.5 concentration in Hanoi during Tet 2020 compared with 2019 52

Figure 3.8 SLCPs in Hanoi during lockdown as coronavirus widespread 53

Figure 3.9 PM2.5 of Hanoi in April 2020 compared with April 2019 53

Figure 3.10 Trajectories of SLCPs in Hanoi associated with meteorological data in wintertime 2019 54

Figure 3.11 Time series of BC, TO3 and PM2.5 in Hanoi associated with meteorological data in 2019 55

Figure 4.1 Correlation of BC and PM2.5 in each season 56

Figure 4.2 Correlation of TO3 and PM2.5 in each season 57

Figure 4.3 Photochemical smog in Hanoi 58

Figure 4.4 SLCP Transport Areas in each season 60

Figure 4.5 Winter variation of SLCP Transport Areas 61

Figure 4.6 Spring variation of SLCP Transport Areas 62

Figure 4.7 Summer variation of SLCP Transport Areas 63

Figure 4.8 Autumn variation of SLCP Transport Areas 64

Figure 4.9 Comparison of transport features and observed enhances of BC and PM2.5 65

Figure 4.10 Diurnal variation of BC and TO3 in Hanoi 65

Figure 4.11 PM2.5 in Hanoi compared with coastal cities in Northern Vietnam 66

Figure 4.12 Atmospheric heating rate of BC 68

(Source: Ramachandran and Kedia, 2009) 68

Figure 4.13 BC concentration in Tokyo have decreased 3 time by stringent regulations for PM emissions 69

Figure 4.14 The differences between the prior and posterior anthropogenic BC emissions for April and October 2006, using OMI_GC AAOD_BC as the observation .69

SLCPs Short-lived Climate Pollutants

TO3 Tropospheric Ozone

TOA Top of the Atmosphere

UFP Ultra-Fine Particle

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ACKNOWLEDGEMENT

I would like to express my gratitude to Professor Kazuyuki Kita for his tireless guidance and training It’s barely impossible to conduct this research without his lead

I thank VJU staff and lecturers, Dr Akihiko Kotera, Dr Hoang Thi Thu Duyen, Ms Bui Thi Hoa for their great help in doing this project, especially in the hard time of coronavirus pandemic, so that this study can continue to moving forward

My appreciation and gratefulness go to JICA, Vietnam - Japan University, Ibaraki University and Vietnam National University of Forestry for their support to set up instruments and implement SLCP monitoring systems in Hanoi

The results showed monthly average of BC, daytime TO3 and PM2.5 as 1-3μg/m3, 21-55ppbv, 18-65μg/m3, accordingly Both BC and PM2.5 were remarkably increased during rush hours or night-time in diurnal variation In contrast, TO3 was often high at noon and depleted to zero at night These diurnal variations can be attributed to their local/regional emissions and production of them near Hanoi The climax episodes of BC and PM2.5 were observed in wintertime, especially in January with periods lasting from 1 day to 1 week These high rises were mostly associated with winter monsoon trajectories from South China Sea, which actually transported emissions from North East region of Northern Vietnam These results firstly show a large contribution of Northern Vietnam sources of SLCP to their concentrations

Given the significant climate forcing of BC, this study strongly suggests that mitigation measures to reduce BC in Vietnam can considerably improve both regional climate change and air quality in the Northern Vietnam region

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CHAPTER 1 BACKGROUND AND OBJECTIVES

“Science is where revolutions happen.”

~Carlo Rovelli

As a physicist and bestselling author, Carlo Rovelli, a professor at Aix-Marseille University has guided thousands of readers through a marvelous adventure of physical world in his wonderful book named ―Seven Brief Lessons on Physics‖ In

this book, he also wrote: “Ever since we discovered that Earth is round and turns

like a mad spinning-top, we have understood that reality is not as it appears to us”

Overall, the Earth and the Universe still conceal many uncertainties and mysteries from us Our mission is to find them out This will not only help us to survive from current threats and moving on but also enable us to tackle the incoming challenges

in the future

In this chapter, we will review the decadal efforts of scientists and researchers to improve our understandings on black carbon, tropospheric ozone, and their impacts

on our climate system by comparing observations and simulations

However, before coming to basic definitions of SLCPs’ species and updated mechanisms of their climate impact, we can have a look through a story behind a picture, which was taken nearby my place in Hanoi, evidently showed the

threatening existence of black carbon in everyday life of local residents

Figure 1.1 Critical air polluted condition in Hanoi by open biomass burning

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In this above picture, local people were still doing exercises in a really bad condition of air quality of black and thick smoke from biomass burning nearby the stadium After two rounds, a middle-aged runner started coughing and walking slowly to the source of the smoke There he met the burner burning leaves and trash behind his house The conversation between them shifted from a low tone request to

a furious quarrel The thing that stopped them from diving into each other with kicks and punches was just a fence Suddenly, the fire became so much bigger and caught into the house of the burner Someone started screaming The burner stopped his ―loud conversation‖ with the middle-aged man and urged people around to help him extinguish the fire

It’s clear that no one could force the burner to stop burning leaves in the backyard behind his house, but his own threat Every action has a motive

Whenever I crossed by the burnt house outside the stadium, I thought that if those two men observed the small flame calmly and consciously, they would have soon realized that it could turn into a really big fire in that dry and windy day Then, the tragedy could have been avoided

1.1 Definition of SLCPs and their significance

Several air pollutants, which have significant warming effects and short lifetime in atmosphere, are called Short-lived Climate Pollutants (SLCPs) Significant SLCPs are black carbon (BC) and tropospheric ozone (TO3) Besides, SLCPs also include non-pollutants such as methane and hydrofluorocarbons (HFCs), which are also referred as Short-lived Climate Forcers (SLCFs)

Until today, SLCP is still an unfamiliar topic and remains underrated in Southeast Asia, and in particular Vietnam Recently, PM2.5 from biomass burning, transportation and thermal power plants have been taken into serious consideration

by localities due to its direct impacts to human health However, the link between SLCPs, especially black carbon and tropospheric ozone, with climate change issues

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and sustainable development has not received enough concern from Vietnam

academia and policy makers

Figure 1.2 Global annual mean distribution of BC direct radiative forcing at TOA

(Source: Wang et al., 2014)

Figure 1.3 Radiative Forcing Caused by Human Activities Since 1750

(Source: EPA, 2016)

TO3 BC

Other

aerosols

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Recent studies have shown that radiative forcing by SLCP increase is evaluated to

be comparable with that by CO2 Sum of radiative forcing by SLCPs is estimated to

be 1.75W/m2, larger than 1.66W/m2 of CO2

Although the lifespan of SLCPs in the atmosphere is much shorter than carbon dioxide (SLCPs’ is hours to years, while CO2 is a decade to century), SLCPs’ radiative forcing is significant compared with CO2 According to a research of EPA

in 2016, the positive warming effect of BC, TO3 and methane in total is comparable with that of CO2 and accounts for around half of total radiative forcing caused by human activities

Because of long lifetime of CO2, only mitigation actions on CO2 are insufficient, but cutting down SLCPs is necessary to achieve 1.5 C target by 2030 according to

SR 1.5 ̊C IPCC 2018

Figure 1.4 Model of CO2 and SLCP cuts compared with other pathways until 2100

(Source: Allen, 2015)

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The short atmospheric lifetime of SLCPs means that their concentrations can be reduced in a matter of weeks to years after emissions are cut, with a noticeable effect on global temperature within the following decades In contrast, CO2 has a long lifetime, so the majority of the climate benefits will take many decades to accrue after the reductions Long-term warming, however, will be essentially determined by total cumulative CO2 emissions – assuming SLCPs are eventually reduced – and will be effectively irreversible on human timescales without carbon removal Thus SLCPs and CO2 both have important effects on climate, but these occur on very different timescales (CCAC, 2014)

According to Special Report 1.5°C of IPCC, Human-induced warming has reached approximately 1°C above pre-industrial levels since 2017 At the present rate, the global temperature would reach 1.5°C around 2040 Pledges contained within current NDCs are insufficient to put the world on a course to 1.5 ̊C, even with the maximum rates of change post-2030 available in the models (IPCC, 2018)

It should be taken into consideration that global temperatures could pass 1.5 C sooner if emissions do not decrease For example, the 1.5 ̊C guardrail could be crossed as early as 2030 if emissions follow the high emissions RCP8.5 scenario from IPCC’s 5th Assessment Report Following that scenario, even for a short period, would make achieving a 1.5 ̊C virtually impossible (IPCC, 2013)

Therefore, it will be too late if mitigation is delayed An integrated multiple-benefits approach enables ambitious action by maximizing multiple-benefits and avoiding negative trade-offs since climate change, air pollution, and sustainable development are inter-linked (CCAC, 2014)

Environmental Effects

BC +0.60(best

estimated) 4-12 days

Fossil fuel combustion (40%), biomass burning (40%), biofuels

(20%)

Health: carrier of toxic chemicals to the human body as

PM2.5

TO 3 +0.35 Hours - Weeks

Precursor pollutants (CO, CH4, NMVOC, NOx) after photochemical reaction

Health:

Cardiovascular, Respiratory diseases Agriculture: reduction of crop yield by damaging ability to absorb

CO 2 +1.66 200 years industrial processesFossil fuel and Ocean acidification

(Source: Bond et al., 2004; IPCC 2007; UNEP and WMO 2011; CCAC)

Co-benefits of SLCPs’ cut will avoid negative trade-offs, since climate change, air pollution and sustainable development are inter-linked in it Recent scientific assessments coordinated by the UN Environment Programme (UNEP) have identified several “win-win‖ or synergy measures for near term climate protection

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and clean air benefits (UNEP & WMO 2011; UNEP 2011a, UNEP 2011b) Fast uptake of these cost-effective and readily available measures, which target emissions of short-lived climate pollutants (SLCPs) in key sectors, could bring rapid and multiple benefits for human well-being These measures are spread across

a variety of sectors, from waste management, where CH4 emissions can be harnessed as a source of energy, to transport, where high-emitting vehicles can be eliminated to reduce BC emissions, to industry where new technologies can be phased in to avoid use of HFCs with a high global warming potential (GWP) “If someone proposed that you could save close to 2.5 million lives annually, cut global crop losses by around 30 million tonnes a year and curb climate change by around half a degree Celsius, what would you do? Act, of course‖ UNEP’s Executive Director, Achim Steiner, has written “More than a decade of painstaking science has built a case that cannot be ignored, namely, that swift action on the multiple sources of black carbon, HFCs, and methane can deliver extraordinary benefits in terms of public health, food security and near term climate protection‖ (CCAC, 2014)

Based on scientific evidence, Climate and Clean Air Coalition in 2014 stated that the rapid and large-scale implementation of SLCP control measures could deliver near term multiple benefits for climate change and sustainable development Recent reports have identified 16 BC and methane measures that can deliver significant benefits to human well-being by protecting the environment and public health, promoting food and energy security, and addressing near term climate change These measures involve technologies and practices that already exist and in most cases are cost effective (CCAC, 2014)

If fully implemented by 2030, these measures could reduce global methane emissions by about 40% and BC emissions by about 80% relative to a “reference‖ scenario (UNEP & WMO 2011)

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In short, SLCPs are responsible for a substantial fraction of near-term climate change, with a particularly large impact in sensitive regions of the world, and can have significant, detrimental health, agricultural and environmental impacts However, the challenge is yet to be fully recognized by the international community (CCAC, 2014)

1.2 Definition of BC, TO 3 and PM 2.5 and their significance

As BC is a product of the incomplete combustion of fossil fuels, biofuels, and biomass, the main sources of black carbon are open burning of biomass, diesel engines, and the residential burning of solid fuels such as coal, wood, dung, and agricultural residues (U.S EPA, 2012) When suspended in the atmosphere or deposited on ice or snow, BC contributes to global warming by heating surrounding

areas, reducing albedo effect and causes human health problems as well

BC is always emitted with co-pollutants, such as organic carbons and sulphates, which can have neutral or even cooling effect by dimming the sunlight and increase the reflection ability of local or regional atmosphere Therefore, BC and co-pollutant particles may disturb the rainfall patterns by modifying atmospheric circulation (semi-direct effect) and may affect Indian monsoon These effects would create impact on agriculture production, food security and sustainable development

of vulnerable countries, especially the ones in Asia and Africa

In terms of health effect, BC may cause cancer and has effects on cardiovascular system (WHO, 2013) BC and co-pollutants make up for most of the particulate matter 2.5 air pollution, one of the leading environmental causes of ill health and premature death 3.5 and 3.2 million people die prematurely each year from exposure to indoor and outdoor PM2.5 pollution, respectively (Lim S et al 2012)

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Ozone is a highly reactive gas composed of three oxygen atoms It is produced naturally in the stratosphere and is majorly produced from air pollutants in the troposphere Depending on where it is in the atmosphere, ozone affects life on Earth

in either good or bad ways (EPA, 2012)

Figure 1.6 Schematic Display of Photochemical Ozone Formation in the

Troposphere (Source: CCAC, 2014)

TO3 is the product of the chemical reactions involving a number of precursor pollutants as well as volatile natural organics precursor pollutants created by human activities include carbon monoxide (CO), non-methane hydrocarbons (NMHC) and nitrogen oxides (NOx), which are largely emitted by cars and other vehicles, fossil

TO3 has strong greenhouse effect because it absorbs infrared radiation from the earth surface in the atmospheric window at around wavelength of 9.6μm

To the matter of human health, TO3 makes it more difficult to breathe deeply and vigorously, shortness of breath and pain when taking deep breaths, or coughing and sore throats It can cause respiratory diseases such as asthma, emphysema, lung cancer, chronic bronchitis, etc., TO3 is dangerous to children, old people, and sensitive patients (EPA, 2019)

To agriculture and forestry, TO3 causes lower crop yield by reducing photosynthesis activity and by damaging leaves and roots It also has warming effect by reducing absorption of CO2 by vegetation

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PM2.5 are tiny particles whose diameter is smaller than 2.5 micrometer (30 times smaller than human hair), and their major components are sulfate aerosol,

secondary organic aerosol and BC

Figure 1.7 Diagram shows PM2.5 particles size

(EPA, nd.)

PM2.5 contains BC which accounts for up to 10% as a key warming effect component However, BC is often emitted along with its co-pollutants Therefore, PM2.5 also includes other cooling effect component such as sulfate and organic particles which stem from vegetation and incomplete combustion of coal and oil

Major sources of PM2.5 are incomplete combustion of coal, oil and biomass from motor vehicles, thermal power plants, residential burning, burning of (agriculture)

Because PM2.5 particles are small enough to be breathed into deep lung and they can cause premature deaths According to WHO, the global deaths every year on PM2.5

is about 7 million people and it is increasing fast in developing countries, especially Southeast Asia Recently, the number of researches on PM2.5 has been increasingly conducted in many countries due to its critical impacts on human health

In this study, PM2.5 is used as a proxy of BC, because their concentrations generally show a tight positive correlation and because PM2.5 concentration can be continuously measured much easier than BC concentration

1.3 Preceding Studies: Status of SLCPs in Vietnam and Southeast Asia

SLCPs observation in Vietnam

Several studies have shown concentrations of BC and TO3 based on in situ observations in Vietnam However, they were mostly focused on air pollution No simultaneous observation of BC and TO3 have been conducted so far

Gatari et al (2006) sampled and analyzed atmospheric aerosols from seven rural sites in North of Vietnam, east of Hanoi and stated that coal and heavy fuel oil combustion were major sources of atmospheric pollutants in the area and that biomass burning and road transport had a marked influence on regional air quality

It was also concluded that Pha Lai thermal power plant was the dominant emitter of coal combustion emission and PM2.5 concentrations were strongly influenced by seasonal variations

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Concerning the air pollution and photochemical smog in Hanoi, D.D An et al (2008) stated that photochemical smog potential in Hanoi at that time was still low Analyzing hourly ozone concentrations in 2 year data (2002-2003), the result of this study indicated that the high episode of TO3 was in March with ozone concentration larger than 46ppb and the emission sources were VOC and NOx emissions from industrialization and transportation in the city

Sakamoto et al (2017) observed TO3 and its precursor pollutants CO, VOC and

NOx in Hanoi, inner city area from 2015-2016 (1-year observation) The results from this research stated that the daily mean value of TO3 was 19.3 ± 15.3 ppb and the correlation among CO, VOC and NOx indicated that the emission mainly originated from vehicles including motorcycles, as well as buses, trucks and cars were the main sources of ozone precursors throughout the year

Investigating the seasonal and sub seasonal variation of ozone mixing ratio (OMR)

in Hanoi, Ogino et al (2013) mentioned that the minimum OMR shown in winter and maximum OMR found in spring and summer By analyzing 7-year ozonesonde data from Hanoi, the authors of this study concluded that low OMR air masses were transported from the equatorial troposphere in winter, and high OMR air masses are transported from the midlatitude stratosphere in summer

In general, there has been up to now few studies on SLCPs in Hanoi and Vietnam, and there are still uncertainties about BC and TO3 especially in the context of climate change

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Climate influence of SLCPs in SE Asia

Figure 1.8 Planetary boundary layer (PBL) heating by surface emission of BC

BC particles absorb solar radiation and heat surrounding air, known as their direct effect Ramachandran and Kedia (2010) calculated the atmospheric heating rates based on the observed BC concentration and showed that heating rates including

BC aerosols are at least a factor of 3 higher than when BC aerosols are absent However, the heating effect of BC is not very significant at the ground surface, because the atmospheric heating by BC is smaller than that by absorption of solar radiation by the ground In contrast, Tripathi et al (2007) and Wang et al (2018) calculated altitude profiles of the heating rate by BC was high throughout the surface boundary layer although BC concentration gradually decreased with altitudes Wang et al (2018) indicated that BC increased atmospheric temperature

at altitudes around the top of the surface boundary layer and that BC did not change the surface temperature directly

Absorption of solar radiation by BC often enhances the temperature at above altitudes but does not change or decrease the temperature at the surface, and this perturbation of the atmospheric temperature profile may change the atmospheric

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circulation and distribution of precipitation, so-called semi-direct effect (e.g Koch and Del Genio, 2010) Lee and Kim (2010) suggested that BC radiative forcing could change the circulation pattern to reduce precipitation especially in Southeast Asia

Although the climate influence by BC is difficult to quantitatively understand because it depends on various parameters: particle size, mixing state, altitude distribution, atmospheric adjustment and so on (Matsui et al., 2018; Takemura and Suzuki, 2019), many model studies predicted that increase of BC emission cause significant temperature increase near surface (Stjern et al., 2017; Sand et al., 2020)

Figure 1.9 Monthly mean BC mass concentration (left) and heating rate (right)

over Ahmedabad in 2008 (Source: Ramachandrand and Kedia 2010)

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Figure 1.10 Vertical profiles of heating rate due to aerosol black carbon calculated

from FBC profiles (Source: Tripathi et al., 2007; Wang et al., 2018)

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Figure 1.11 Annual mean model median change in near-surface temperature (top

left), zonally averaged temperature change for the model median (black line) and

individual models (top right)

(Source: Stjern et al., 2017)

The remaining panels in Figure 1.3.4 show individual model results Data are based

on the last 50 years of the coupled runs, and hatched areas in the model median map indicate grid cells for which values are more than one multi-model standard deviation away from zero

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Although few studies have been focused on climate change by SLCPs in Southeast Asia so far, it was studied as a part of Asian climate change especially in China and India The understanding about BC aerosols, ozone and their effects on regional and global climate has been improved through time

Meehl et al (2008) mentioned possible effects of BC aerosols on Indian Monsoon

By simulating six-member ensemble of twentieth century with only BC varying whereas, natural and human-induced forcing fixed with their pre-industrial values, the researchers experimented the effects of BC over South and Southeast Asia Differences of BC simulations showed that the radiative effects of BC aerosols were most dramatic during the dry season over South Asia, and changes in the temperature of air masses over India and Tibetan Plateau due to absorption and reflection solar radiation of BC aerosols would lead to anomalous inflow from Indian Ocean to the south and increased precipitation over most of India in the pre-monsoon period (March, April, May) In summer, BC also weakened China rainfall while enhanced precipitation in Southeast Asia and Japan This study pointed the significance of BC aerosols for rainfall pattern over most of Asia and Indian Monsoon in particular

Lee and Kim (2010) discussed the effects of BC radiative forcing on decrease of spring rainfall over Southeast Asia The results from this study showed that atypical precipitation patterns and associated large-scale circulation induced by BC radiative forcing can explain observed rainfall reductions Therefore, BC was considered as one of the most important factors impacting precipitation trend in Southeast Asia

Although both Meehl et al (2008) and Lee & Kim (2010) agreed on possible effects

of BC on rainfall patterns in Southeast Asia, there were still many biases and uncertainties of BC radiative forcing due to underestimation of global models at that time on solar radiation absorption of BC aerosols That was when Wang et al (2016) estimated BC direct RF based on a model constrained by observations and indicated BC DRF in South and Southeast Asia This study reduced uncertainty in

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BC RF from -101%/+152% to -70%/+71% over Asia and constrained BC RF of 0.61 W/m2 This is the best estimate until now This implied that reduction in BC emissions would contribute to decrease the rate of global warming, but the contribution could be less than previous thought

In general, researchers in nearly a decade have found evidence linked SLCPs to climate change, especially regional climate in Southeast Asia Chen et al (2017) also confirmed direct radiative forcing of anthropogenic aerosols, TO3 and greenhouse gases and indicated that aerosol influence may change wind flow and precipitation in East, Southeast, South Asia in winter This one more time rang the bell for policy makers, entrepreneurs and stakeholders to take SLCP’s cut into serious consideration

Hang (2014) evaluated the impact of BC aerosols to temperature and precipitation

of Vietnam and surrounding regions from 1991 to 2000 by using RegCM 4.2 and module Chem_aerosol through 3 experimental simulation: no aerosols; BC from human and biomass burning; and dust The results showed the average BC as 0.92 – 1.17 mg/m2 The high rises of BC lasted from Nov to Mar, while low BC was from Jun to Sep due to wet deposition in rainfall season BC caused temperature decrease

in almost region, significant decrease in winter in India, Southeast China, Myanmar, Lao, N Vietnam from -0.3 to -0.8 Celsius degree Less decrease of T in summer and autumn (-0.1 to -0.3) in Lao and N Vietnam BC impact and dust impact on precipitation was not clear however dust impact on rainfall was in larger than that of

BC In July, dust caused -8mm/month decreased precipitation in Myanmar and N Vietnam

Van (2013) studied the ability to apply WRF-CHEM to Vietnam region by 2 experiments of WRF_DUST and WRF_NOCHEM using meteorological data from NCEP FNL in 2006 and emission inventories from RETRO and EDGAR The results showed the practical and meaningful application of WRF-CHEM to Vietnam This was the first time 0.3 resolution simulated in Vietnam region with

up to 50%, and cumulative sea-level rise by about 30% as compared to the same scenario (Hu A et al 2013)

1.4 Mitigation measures to reduce SLCPs in Vietnam and SE Asia

A number of countries participated in the Climate and Clean Air Coalition (CCAC),

a voluntary partnership of governments, intergovernmental organizations, businesses, scientific institutions and civil society organizations, for improving air quality and protecting the climate through actions to reduce short-lived climate

pollutants (CCAC, nd)

Vietnam has become a partner of CCAC since 2017 to cooperate in implementing measures to mitigate methane in agriculture sector, especially in rice cultivation In Vietnam, agriculture sector is responsible for 33% of total greenhouse gas emissions with livestock and rice production as primary sources Therefore, it is understandable and efficient to start cutting down methane as the first commitment

of reducing short-lived climate pollutants This is not only an ensured feasible approach but also a foreseeable efficient plan as Vietnam’s economy is transforming from agriculture sector to industry and service sector In addition, Vietnam starts contribution to cut down other SLCPs; requesting funding from

(https://www.ccacoalition.org/en/activity/vietnam-hfc-inventory), and Vietnam freight assessment report (2017) which proposed actions for the development of green freight program in Viet Nam, helping to reduce BC emission in Vietnam

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In Southeast Asia, other countries have been actively contributed to SLCPs’ reduction Thailand is developing their understandings on emissions of BC and precursor pollutants of TO3 from biomass burning, vehicles and industrial production Lao is focusing on HFCs, municipal solid waste and agriculture

1.5 SLCPs’ sources in Vietnam

Kurokawa and Ohara (2019) estimated air pollutants emissions including BC emission in Asia to make the Regional Emission inventory in ASia (REAS) version 3.1, and showed NOx, most significant ozone precursor, and BC emission from Vietnam was 568 and 64 Gt/year in 2015 These values are larger than those from Laos, Myanmar and Cambodia, similar to those from Thailand and Philippines, and much less than those from China and India

- Remote sources: long-range transport of air masses by human and industrial activities in China, South Thailand and India; biomass burning in South China, India, Thailand, Myanmar and Lao

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1.6 Objectives of this study

- To make clear the concentrations of BC, TO3 and PM2.5 in Hanoi and the features of their variations based on in situ observations

- To identify source regions affecting the increase of these SLCPs in Hanoi for each season on the basis of the observed features and the trajectory analysis

The scope of this research mainly focuses on variations and sources of BC and TO3

as two species of short-lived climate pollutants in Hanoi The climate effects of BC and TO3 will be discussed in Chapter 4 based on results in Chapter 3 Quantitative evaluation of warming effect by SLCP needs comprehensive climate model and is beyond this study

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CHAPTER 2 METHODOLOGY AND STRATEGY IN THIS STUDY

“In the real life, I was told, one had to abandon the impossible and embrace the practical.”

“Give the impossible a chance.”

~Michio Kaku

Without a solid background in advanced physics, the young Michio Kaku realized that he would be forever speculating about futuristic technologies without

understanding whether or not they were possible “I realized, I need to immerse

myself in advanced mathematics and learn theoretical physics,” Michio said “So that is what I did”

Constructing particle accelerator to create antimatter in a high school science fair was the first ambitious project of young Michio, which earned him a ride to Harvard Today, Michio is known as the co-founder of string theory, finishing what Einstein started, combining the theory of general relativity and quantum mechanics More evidence and better understanding on string theory may one day allow us to travel between universes, into new dimensions, or even time travel

That is what people talked about Michio, actually I was more impressed with what

he described about Michael Faraday, the ―father‖ of force fields, which were previously thought to be useless Today, the light that we are using, and all the electricity, computers and internet are driven by force fields of Faraday He has created forces to build our modern civilization However, not so many people know that the poor young Faraday was illiterate in mathematics Consequently, his

notebooks are full of hand-drawn diagrams, not of equations “Ironically, his lack

of mathematical training led him to create the beautiful diagrams of lines of forces that can be found in any physics textbooks nowadays”, Michio wrote in his recent

renowned book, Physics of the Impossible

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Inspired by Michio and Faraday, I struggled to embrace this research without a solid background in natural science

2.1 Strategy to attain the objectives

In order to achieve two objectives of this study, I apply the combination of the observation of SLCPs, their source information, and the meteorological analysis I have observed data of black carbon, tropospheric ozone and particulate matter 2.5 in Hanoi since December 2018, while I was in second semester of Master Program of Climate Change and Sustainable Development in Vietnam - Japan University

Although these atmospheric compounds have been observed separately in Vietnam,

it is probably the first time to observe them simultaneously and compared This simultaneous observation will enable us to discuss their correlation to examine local source contribution This is a significant advantage of this study

Figure 2.1 Initial strategy of research activities in this study

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Figure 2.1.1 illustrates the original strategy of this study to attain our objectives To answer the questions (i) what is the concentration of SLCPs in Hanoi and how they vary, we started and based on observational data as the primary data, because reliable observations can directly provide these information To get the answer for the question (ii) where do they come from and what source contribute to increase SLCPs in Hanoi, we planned the correlation analyses of source distribution data and meteorological data with the observational data After the data processing of black carbon, tropospheric ozone and particulate matter 2.5 to see the correlation, we firstly examine their correlation and their diurnal variations Secondly, comparing the observed variation of SLCP concentrations with the transport routes estimated

by the trajectory analysis, contributions of local/regional emission and that of the transport from remote sources can be examined

In this study, a large contribution of remote sources was projected Contributions of various remote source would be estimated from the integration of emission amount based on the inventory data along air mass trajectories Because biomass burning emission has large variability, its contribution would be estimated using open burning signature derived from the remote sensing data along the air mass trajectory Comparing correlations of the observed variation with these estimation

of various sources, we can estimate that relative significance of them

However, in the process of this study, finding that local source more significantly contributed to the increase of SLCPs than the projection, the focus of this study has been changed to the local/regional source in the northern Vietnam The strategy of this study has been changed as to the following as illustrated in Figure2.1.2 To make clear the influence of local/regional sources, various features of the variation

of the observed SLCP concentrations with meteorological conditions including trajectories are examined as shown in the next section As one of key evidences, BC concentrations observed at multiple sites surrounding Hanoi were compared In order to carry out this comparison, we use PM2.5 concentration data as a proxy or indicator of the BC concentration

to BC and TO3 was pumped to one inlet, then it was separated to each BC and TO3 instrument with different specialized tubes to ensure the same air sample and accuracy for measurement All three instruments have been observed in VJU - MCCD office since December 2018

Picture: Simultaneous monitoring system of BC, TO3 and PM2.5 at VJU Hanoi

The principle features of the PSAP are:

- The instrument is self-contained and requires only an external vacuum source to

provide a sample flow of 1 to 2 lpm

- Optical absorption coefficient, flow rate and lamp reference are available as both

analog and serial data Outputs update once each second