Khóa luận tốt nghiệp ASSESSMENT OF ACID RAIN PROGRESS IN HANOI CITY DURING THE PERIOD OF 2008-2018

VIETNAM NATIONAL UNIVERSITY, HANOI VNU UNIVERSITY OF SCIENCE FACULTY OF ENVIRONMENTAL SCIENCES Lê Thi Thuy ASSESSMENT OF ACID RAIN PROGRESS IN HANOI CITY DURING THE PERIOD OF 2008-2018 Submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Environmental Sciences (Advanced Program) Hanoi - 2020 VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAMVNU NATIONAL UNIVERSITY, HANOI UNIVERSITY OF SCIENCE UNIVERSITY OF SCIENCE FACULTYVNU OF ENVIRONMENTAL SCIENCES FACULTY OF ENVIRONMENTAL SCIENCES Lê Thi Thuy Lê Thi Thuy ASSESSMENT OF ACID RAIN PROGRESS ASSESSMENT OFDURING ACID RAIN IN HANOI CITY THEPROGRESS PERIOD OF IN HANOI CITY DURING 2008-2018THE PERIOD OF 2008-2018 Submitted in partial fulfillment of the requirements for the degree of SubmittedBachelor in partialoffulfillment Science inofEnvironmental the requirements Sciences for the degree of Bachelor of (Advanced Science in Environmental Program) Sciences (Advanced Program) Supervisor : DrPham PhamThi ThịThu ThuHa Ha Supervior : Dr Hanoi - 2020 Hanoi - 2020 ACKNOWLEDGEMENT Foremost, I would like to express my sincere gratitude to my supervisor Dr Pham Thi Thu Ha, Faculty of Environmental Sciences – University of Science, Vietnam National University, Hanoi I feel fortunate and honored to have had her as my supervisor It was her expertise and experience that provided me with practical knowledge, comments, and support during the thesis writing process I would like to thank Acid Deposition Monitoring Network in East Asia system for providing data I am most in debt to the households, the district and commune authorities who were most collaborative in completing the data, and in providing discussion opportunities on the results I am grateful to the lecturers of the Faculty of Environmental Sciences from VNU University of Science, Vietnam University for teaching and conveying a lot of professional knowledge to me during my studies Last but not least, I would like to thank my family and friends, whose kindness, encouragement and support are with me against all the odds Hanoi, September 2020 Student Lê Thị Thuy LIST OF ABBREVIATIONS AIRMoN : Research Monitoring Network AF AP CF : Anthropogenic factor : Acidify potential : Crust fraction DS : Dry season EANET : East Asia Acid Deposition Monitoring Network EEC : European Economic Community EDGAR : The Electronic Data Gathering, Analysis, and Retrieval system EFs HYSPLI MDN : Enrichment factors : Hybird Single Partical Lagrangian Integrated Trajectory model : mercury deposition network NAD/NTN : The National Atmospheric Deposition Program VWM volume weighted mean NP : Neutralize potential NF : Neutralization factor NSS : non-sea salt RS : Rain season SSF SMK : Sea spray fraction : Seasonal MannKendall LIST OF ABBREVIATIONS INTRODUCTION CHAPTER LITERATURE REVIEW 1.1 Rain water 1.1.1 The concept of rain water 1.1.2 Acid rain 1.2 Oveview of dosmestic and worldwide researches 1.2.1 In the world 1.2.2 In Vietnam 1.3 Overview of area 12 1.3.1 Location 12 1.3.2 Climate 13 1.3.3 Hydrography 14 1.3.4 The economic growth in Hanoi 15 CHAPTER MATERIAL AND REARCH METHODS 17 2.1 Research object 17 2.2 Scope of study 17 2.3 Database 17 2.4 Methodology 18 2.4.1 Collection and synthesis of secondary data method 18 2.4.2 Field investigation and survey method 18 2.4.3 Calculation method of acid rain characteristics and data processing 18 2.4.4 Annual volume - weighted mean precipitation concentrations 19 2.4.5 Acid neutralization 19 2.4.6 Wet deposition flux 19 2.4.7 Marine and crustal enrichment factors 20 2.4.8 Non-parametric test method Seasonal Mann-Kendall 20 2.4.9 Correlation coefficient 22 2.4.10 Calculate [nss-SO4 2-] and [nss- Ca2+] 22 2.4.11 Calculate pAi index 23 CHAPTER RESULT AND DISCUSSION 24 3.1 Annual volume - weighted mean precipitation concentrations 24 3.2 pH of rain water 25 3.3 Seasonal variation of the chemical composition 28 3.4 Assessment on wet deposition trend 29 3.4.1 Monthly deposition of ions 29 3.4.2 Trend of ions deposition 30 3.4.3 Trend of ions concentration 35 3.5 Correlation coefficient 36 3.6 Acid neutralization 38 3.7 Wet deposition rates of major ions 41 3.8 Enrichment factors 41 3.9 Source assessment for different ionic component 43 CONCLUSION AND RECOMMENDATION 45 Conclusions 45 Recommendations 46 REFERENCE 47 APPDENDIX 52 LIST OF FIGURES Figure This image illustrates the pathway for acid rain in our environment [18] Figure Administrative map of Hanoi city [11] 13 Figure Hanoi climate graph [10] 14 Figure Chemical composition percentages of rainwater in Hanoi 24 Figure Frequency distribution of the pH values of rainwater in Hanoi during the sampling period 25 Figure Frequency distribution of the pH values of rainwater in Ho Chi Minh 26 Figure Frequency distribution of the pH values of rainwater in Hoa Binh 27 Figure Frequency distribution of the pH values of rainwater in Yen Bai 27 Figure VWM of major ions in rain season and dry season in Hanoi during 2008-2018 (µmol L-1) 28 Figure 10 The trend of wet deposition of ions over the months in Hanoi between 2000-2018 34 Figure 11 The average multi annual wet flux depositions (mmol m-2y-1) of major ions at the studied sampling site 41 LIST OF TABLES Table Seasonal variations of the VWM concentrations of the major ions in the rainwater from Hanoi (µmol L-1) 28 Table The average value of ion deposition, the level of change in deposition, the Sen’s slope, significance level p at Hanoi station during the period from 2000-2018 30 Table Level of change in concentration and precipitation by year (%) in Hanoi from 2000-2018 35 Table Pearson correlations matrix for the ion concentrations in rainwater of Hanoi 36 Table The value of neutralization factor (NF) of rainwater from Hanoi and other areas in Vietnam 39 Table The value of neutralization factor (NF) of rainwater from Hanoi and other areas in Vietnam 40 Table Enrichment factors relative to seawater and soil for rainwater constituents in Hanoi in 2008-2018 43 Table Source contributions for different ionic constituents in rainfall measured in Hanoi in the period 2008 -2018 44 Table Comparison of pH and major ions concentration (in µmol L-1) at Hanoi with other areas in Vietnam 52 INTRODUCTION In recent years, the problem of air pollution has become an urgent problem that all countries aim to solve, especially its consequences such as acid rain, the greenhouse effect, Acid rain is one of the most serious consequences of air pollution Acid rain has caused serious harm to the environment, ecosystem and people Currently, research on acid rain in many countries around the world is very methodical and organized Many countries have laws regarding gas emissions that cause acid rain [18] The atmospheric precipitation is an important means of scavenging pollutants from the atmosphere and this occurs either by wet or dry deposition Sulfur compounds and acids were already identified in the air and in rainwater during the 17th century; however, in the 19th century, there was an increase in rain acidity mainly due to anthropogenic emissions [42] Acid rain has a pH lower than 5.6, the value expected on the equilibrium of pure water and atmospheric CO2 This decrease of pH values is basically caused by the presence of sulfuric, nitric and carboxylic acids, their main precursors being emissions of sulfur and nitrogen oxides, hydrocarbons and carboxylic compounds These processes involve complex chemical reactions in the atmosphere [42, 43] Rain is the most effective scavenging factor for removing particulate and dissolved organic gaseous pollutants from the atmosphere The scavenging of the atmospheric pollutants affects the chemical composition and the pH of rainwater The acidity level depends on the neutralization produced by certain rainwater components such as NH3, CaCO3 and hydroxide [25, 42, 43] Rainwater composition plays an important role in scavenging soluble components from the atmosphere and helps us understand the relative contribution of different sources of atmospheric pollutants [25, 31, 42] Acid deposition, commonly known as acid rain, occurs when emissions from the combustion of fossil fuels and other industrial processes undergo complex chemical reactions in the atmosphere and fall to the earth as wet deposition (rain, snow, cloud, fog) or dry deposition (dry particles, gas).[19] Acid deposition often occurs in highly industrialized areas such as Europe and North America, and its range of impacts has now expanded to Asia [31] Acid deposition has serious human and property consequences such as damaging crops, reducing crop yields, destroying forests, threatening aquatic and terrestrial life, destroying architectural and construction works and seriously affecting human health [19] In developing countries, with high economic growth and energy consumption, air pollution has become a socially significant issue that needs to be scientifically considered Rainwater plays an important role in collecting dissolved components from the atmosphere, so the composition of the rainwater will provide information on the contributions of various sources to air pollution [21, 37] Rapid economic development and increased energy demand have resulted in severe air pollution problems throughout Vietnam, and the increasing emissions of man-made acidic oxides of sulfur and nitrogen have led to the significant deposition of acid rain in Vietnam Acid rain is one of the manifestations of acid deposition in the atmosphere Rainwater washes pollutants from the air, so acid rain is considered a problem of environmental pollution, the main cause of SO2 and NOx emissions from various sources Nearly one decade, the extent and magnitude of acid deposition in Vietnam and some Asian countries become apparently increasing More importantly, in Vietnam acid rain has been recorded in almost the city and some dramatic effects of acid rain on terrestrial plants have been investigated [14] Vietnam is in the period of industrialization and modernization, so air pollution is becoming an urgent problem The overexploitation of natural resources, development of industrial parks and urban areas without synchronous planning lead to increased degradation environmental quality According to the annual Vietnam Environmental Status Report, the air environment around most urban centers and some industrial zones has been polluted, and thus its consequences will lead to acid rain [14] Observed data from the national 3.6 Acid neutralization In general, the acidity of rainwater is controlled mainly by the concentration of acidic ions (e.g., NO3− and SO42−) As discussed above, the rainwater from Hanoi has quite high pH value compared with that of other areas in Vietnam (Table 9) However, the concentrations of NO3− and SO42− are also the highest This indicates that the content of acidic ions is not the main reason for the low pH value of rainwater in Hanoi Previous studies have pointed out that the rainwater acidity can also be affected by the contents of basic ions (Ca2+ and NH4+) in the rainwater [36] The rainwater acidity and the relationship between the acidic and basic components can reflect the intensity of neutralization To assess the neutralization capacity of the basic components, the ratio of the neutralizing potential to the acidifying potential (NP/AP) was employed as suggested by Fujita et al (2000) [36]: NP/AP = [nss−Ca2+ + NH4+] / [nss−SO42− + NO3-] Where the value of [nss-Ca2+ + NH4+] is considered to be the neutralizing potential (NP), and [nss-SO42− + NO3−] is considered to be the acidifying potential (AP) The non-sea salt (NSS) values of different ionic species were calculated from the measured element concentrations by using sodium as the reference element and assuming that all sodium is derived from marine sources [18] Non-sea-salt fraction ion concentrations were given by: NSSX = [X]rainwater − [Na+] rainwater × ([X] / [Na+]) seawater, Which X denotes the measured ions The calculated results of nss-Ca2+, nss-SO42−, NP, AP and NP/AP of rainwaters in Hanoi and other areas in Vietnam are presented in Table The equivalent ratio of NP/AP in Hanoi, Hoa Binh, Ho Chi Minh, Yen Bai were 1.27, 1.18, 1.23, 1.2, respectively, indicating that alkaline constituents neutralize the acidity [20, 27] 38 Table The value of neutralization factor (NF) of rainwater from Hanoi and other areas in Vietnam Area nss-Ca2+ nss-SO42NP AP NP/AP pH pAi ΔpH Hanoi (2008-2018) 22.8 32.4 77.7 59.3 1.27 5.8 4.14 1.66 Hoa Binh (2008-2018) 14.39 20.09 46.17 38.12 1.18 5.5 4.42 1.08 Ho Chi Minh (2014-2018) 17.52 22.2 36.32 29.5 1.23 5.98 4.1 1.88 Yen Bai (2015-2018) 19.91 29.1 68.57 56.99 1.2 5.23 4.24 0.99 To determine the degree of neutralization of the acidity, ΔpH is computed as: ΔpH = pH−pAi Where pAi is the estimated pH The pAi equals the measured pH when no neutralization has occurred [25], and the pAi can be calculated by the following equation: pAi = − log [ nss−SO42− + NO3− ] Thus, the differences (ΔpH) between the measured pH and the estimated pH (pAi) can be taken as the evaluation index of the acid neutralization capacity The calculated results of pAi and ΔpH are presented in Table The ΔpH of rainwater from Hanoi, Hoa Binh, Ho Chi Minh are 1.66, 1.08, 1.88, respectively Whereas, the ΔpH of rainwater from Yen Bai is the lowest with 0.99, which reflects weak neutralizing capacity of the basic cations in the rainwater To evaluate the neutralization percentage of basic cations in rainwater, the neutralization factor (NF) was calculated by the following equation [25, 36]: NFXi = [Xi] / ([nss−SO42− + NO3−] Where Xi is the chemical composition of interest, with all of the ions expressed in μmol l−1 The NF values of Ca2+, NH4+, Mg2+ and K+ in the rainwaters of Hanoi and other areas in Vietnam are presented in Table The NF values of Ca2+, NH4+, Mg2+ and K+ in the rainwater of the study area are only 39 0.39, 0.93, 0.08 and 0.06, respectively Compared with other cities in Vietnam, the NF values of Ca2+ (NF (Ca2+)) and NH4+ (NF(NH4+)) in the rainwater of all city were quite low, which indicated the weak neutralization resulting from the deficiency of alkaline constituents Based on the calculated results of the NP/AP, ΔpH and NF (Ca2+) and NF (NH4+) in the rainwater, the lack of a neutralization capacity could be the main reason for the severe acid rain in all city Although Hoa Binh and Yen Bai are rural and mountainous areas characterized by an agricultural economy, small and medium-sized industries, acid rains occur with high frequency in Hoa Binh and Yen Bai, indicating the occurrence of acid rain is not only dependent on local emission sources but also on atmospheric circulation Table The value of neutralization factor (NF) of rainwater from Hanoi and other areas in Vietnam Area Hanoi (2008-2018) Hoa Binh (2008-2018) Ho Chi Minh (2014-2018) Yen Bai (2015-2018) NF(Ca2+) NF (NH4+) NF (Mg2+) NF(K+) 0.39 0.93 0.08 0.06 0.38 0.83 0.07 0.08 0.78 0.64 0.31 0.23 0.35 0.85 0.05 0.08 40 3.7 Wet deposition rates of major ions 100 90 80 mmol m-2y-1 70 60 50 40 30 20 10 SO42- NO3- Cl- NH4+ Na+ K+ Ca2+ Mg2+ Figure 11 The average multi annual wet flux depositions (mmol m-2y-1) of major ions at the studied sampling site The rates of wet deposition are directly correlated to both the annual rainfall amount and the chemical content measured in precipitation, therefore it can be said that wet deposition is mainly influenced by the annual total rainfall [19] In case of cations, NH4+ had wet deposition the highest with 91.3 mmol m-2y-1, while the smallest values were K+ with values 6.8 mmol m-2y-1, the following is Mg2+ with values 8.1 mmol m-2y-1, respectively In case of anions the largest values were measured for SO42– with 56.2 mmol m-2y-1, and 20.5 mmol m-2y-1 were the values of Cl- which were the smallest in all anions 3.8 Enrichment factors Enrichment factors (EFs) are normally applied to identify the source of ions in rainwater Na is commonly taken as the best reference element for seawater since it is assumed to be of purely marine origin [38] Al and Ca are typical lithophilic elements normally used as reference elements for continental crust [20] To estimate the marine and terrestrial contributions to rainwater, the EF values for rainwater compositions were calculated using Ca2+ as a reference element for crustal source and Na+ for marine source [20, 24] 41 Generally, an element is considered to be enriched or diluted relative to the reference source with an enrichment factor (EF) value much higher or much smaller than [20, 26, 38] An EF value close to one is an indicator that the only source of that element to be seawater or soil derived, respectively, while higher values than unity are suggesting the influence of other sources too [25] Table gives the ratios of Cl-, SO42+, K+, Ca2+ and Mg2+ with respect to Na+, the ratios of Cl-, SO42-, NO3-, K+, Na+ and Mg2+ relative to Ca2+ and the EF values of ions in rainwater for crust and sea salt components All ratios of SO42, K+ and Mg2+ with respect to Na+ in rainwater of Hanoi were found to exceed recommended seawater ratios These elevated values may be due to the contribution of anthropogenic and crustal sources Similarly, the ratios of Cl-, SO42+ and NO3- with respect to Ca2+ in rainwater of Hanoi are higher than recommended crustal ratios suggesting a non-crustal source The calculated EFseawater and EFcrust for ionic species provided further evidence of this Cl− had EFmarine value of 1.3 and EFsoil value of 170, clearly indicating that Cl− had been enriched relative to sea water and soil, but the influence of marine source was considerable The average EFseawater and EFcrust for Mg2+ and K+ indicates that Mg2+ and K+ mostly originate from crust source and partly from marine source These results are in agreement with those from other sites [2, 27, 38] Average EF marine value of Ca2+ was 66.12, suggesting that it originated from terrestrial source SO42− had EFmarine value of 28.22 and EFsoil value of 75.26, showing largely enriched relative to marine source and soil source These high EF values of SO42− indicated that SO42− mainly originated from anthropogenic sources NO3− had high EF value for soil (EFsoil=585) and was meager from marine Thus, anthropogenic activities were also considered as the major sources of nitrate 42 Table Enrichment factors relative to seawater and soil for rainwater constituents in Hanoi in 2008-2018 [X/Na+]seawater [X/Na+]rainwater EFmarine [X/Ca2+]crust [X/Ca2+]rainwater EFcrust 3.9 K+ 0.022 0.42 21.736 K+ 0.04 0.17 0.34 Ca2+ 0.044 2.56 66.12 Na+ 0.569 0.39 0.69 Mg2+ 0.227 0.5 2.082 Mg2+ 0.561 0.2 0.36 SO420.125 3.66 28.22 SO420.019 1.43 75.26 Cl1.16 1.3 1.12 Cl0.003 0.51 170 NO30.002 1.17 585 Source assessment for different ionic component The ions in precipitation were mainly from anthropogenic sources, sea spray and terrestrial dust from wind erosion, provided that contributions from volcanic and other natural sources were negligible The chemical compositions of precipitation were expected to reflect the relative contribution of the ions from these reservoirs [20, 38] The anthropogenic, marine and crust sources of ionic components in rainwater were computed respectively using the following equations: %SSF = 100(X/Na+)marine / (X/Na+)rainwater %CF = 100(X/Ca2+) soil / (X/Ca2+)rainwater %AF = 100 - %SSF - %CF Where SSF, CF and AF represented sea spray fraction, crust fraction and anthropogenic fraction, respectively Table showed the approximate contributions of different sources to ionic species in rainwater The results indicated that nearly all the SO42−, Ca2+, K+ appeared to be of non-marine origin Ca2+ and K+ were mainly from crust origin K+ might be also considered as a chemical signature of biomass burning [20] K+ usually occurs in coarse particles in soil, while fine particles of K+ resulted from the wood combustion [27, 38] The primary source of K+ was considered as the terrestrial source since it was difficult to distinguish the soil source from the wood combustion in the precipitation Cl− mainly came from both marine (89.23%) and a little from crust 43 (0.59%) and anthropogenic sources (10.18%) Mg2+ mainly came from crust source and part from marine source SO42- had a tiny contribution from crust source, with about 95.25% of total SO42- due to anthropogenic sources The contribution from anthropogenic source was estimated by subtracting the crust contribution from that of total nitrate in rainwater About 99.83% of NO 3- was then attributed to the anthropogenic source These results reflect coal combustion and vehicle traffic of Hanoi Extensive SO2 and NOx emitted into the atmosphere due to coal combustion and vehicles led to the high content of acidic ions (SO42- and NO3-) Table Source contributions for different ionic constituents in rainfall measured in Hanoi in the period 2008 -2018 Terrestrial fraction (%) Ions Sea salt fraction (%) Crust fraction (%) Anthropogenic source fraction (%) SO42- 3.42 1.33 95.25 NO3- - 0.17 99.83 10.18 Cl- 89.23 0.59 Ca2+ 1.72 98.41 Mg2+ 45.4 54.6 K+ 5.21 94.79 44 CONCLUSION AND RECOMMENDATION Conclusions Based on the rainwater chemical monitoring data source of the East Asia Acid Deposition Monitoring Network (EANET) at Hanoi station in the period 2008 - 2018, the study has evaluated progress of acid rain in Hanoi city Some main conclusions are drawn as follows: The results of this study clearly showed that acid rain (pH