INVESTIGATION OF THE TRANSPORT PROFILE AND DISPERSION OF ATMOSPHERIC AEROSOL OVER THE COASTAL REGION OF LAGOS

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ABSTRACT

This study investigates the transport profile and source-sink system for sea salt aerosol over the coastal region of Lagos. The study utilized the GPS information of the study locations to simulate meteorological variables over the area from the Air Resource Laboratory (ARL) website, The ARL/GFS model was used to determine the wind rose information between 8th and 14th of June, 2017. In addition, backward air mass trajectories were determined at various heights of 0m, 1000m and 2000m above ground level (AGL) for aerosol transport patterns as well as concentration dispersion using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model.

The result showed that aerosols are of sea salt origin which evolved from the sea of the Atlantic Ocean. The maximum wind speed for the period considered from 8th to 14th June 2017 was 4 to < 7 m/s range in SW direction and as such complete calmness was not observed during the period under consideration. The highest frequency of wind blown was 56% which implies that 56% of atmospheric sea salt aerosol were transported during the study period. The backward concentration trajectory indicated that the maximum aerosol pollution reaching Lagos was 2.1 x 10-10 mg/m3 which were from the Atlantic Ocean and the minimum was about 5.0 x 10-16 mg/m3. Since these pollutants are most likely sea salts which are highly corrosive, adequate corrosion protection is recommended.

TABLE OF CONTENTS

DECLARATION……………………………………………………………………………………………… i

CERTIFICATION…………………………………………………………………………………………… ii

DEDICATION……………………………………………………………………………………………….. iii

ACKNOWLEDGEMENTS……………………………………………………………………………… iv

ABSTRACT……………………………………………………………………………………………………. v

LIST OF FIGURES……………………………………………………………………………………….. viii

LIST OF ABBREVIATIONS…………………………………………………………………………… ix

CHAPTER ONE……………………………………………………………………………………………… 1

INTRODUCTION…………………………………………………………………………………………… 1

CHAPTER TWO…………………………………………………………………………………………….. 6

LITERATURE REVIEW…………………………………………………………………………………. 6

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CHAPTER THREE……………………………………………………………………………………….. 28

RESEARCH METHODOLOGY…………………………………………………………………….. 28

CHAPTER FOUR…………………………………………………………………………………………. 33

RESULTS AND DISCUSSION……………………………………………………………………….. 33

CHAPTER FIVE…………………………………………………………………………………………… 47

CONCLUSION AND RECOMMENDATION………………………………………………….. 47

REFERENCES……………………………………………………………………………………………… 48

APPENDIX………………………………………………………………. Error! Bookmark not defined.

LIST OF FIGURES

Figure 4.1: Windrose for Lagos within 10m and 950mb between 08/06/2017 and 11/06/2017…… 35

Figure 4.2: Windrose for Lagos within 10m and 950mb between 09/06/2017 and 12/06/2017…… 36

Figure 4.3: Windrose for Lagos within 10m and 950mb between 10/06/2017 and 13/06/2017…… 37

Figure 4.4: Windrose for Lagos within 10m and 950mb between 11/06/2017 and 14/06/2017…… 38

Figure 4.5: A four-day air mass transport route reaching Lagos between 11th and 15th June, 2017

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Figure 4.6: A four-day air mass transport route reaching Lagos between 15th and 19th June, 2017

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Figure 4.7 Transport pathway of sea salt aerosol and concentration dispersion for 2300hr 12th June to 0000hr 13th June………………………………………………………………………………………………………………. 43

Figure 4.8: Transport pathway of sea salt aerosol and concentration dispersion for 1100hr 12th June to 1200hr 12th June………………………………………………………………………………………………………………. 44

Figure 4.9: Transport pathway of sea salt aerosol and concentration dispersion for 0500hr 12th June to 0600hr 12th June………………………………………………………………………………………………………………. 45

Figure 4.10: Transport pathway of sea salt aerosol and concentration dispersion for 0800hr 11th June to 0900hr 11th June………………………………………………………………………………………………………………. 46

LIST OF ABBREVIATIONS

ARL               AIR RESOURCE LABORATORY CCN                       CLOUD CONDENSATION NUCLEI GFS                       GLOBAL FORECAST SYSTEM

GDAS             GLOBAL DATA ASSIMILATION SYSTEM

HYSPLIT HYBRID SINGLE PARTICLE LAGRANGIAN  INTEGRATED TRAJECTORY

NOAA NATIONAL OCEANOGRAPHY AND ATMOSPHERIC ADMINISTRATION READY REAL TIME ENVIRONMENTAL APPLICATION AND DISPLAY SYSTEM SSA      SEA SALT AEROSOL

CHAPTER ONE INTRODUCTION

                        Background of Study

Aerosol is a suspension of fine solid particles or liquid droplets in the atmosphere. Examples are smoke, sea dust, volcanic dust, air pollution, etc. Aerosol can also be a liquid substance, as a disinfectant or deodorant, sealed in a metal container under pressure with an inert gas or other activating agent and released as a spray or foam through a push-button valve or nozzle. Ocean water and sea salt are transferred to the atmosphere through air bubbles at the sea surface. As this water evaporates, the salt is left suspended in the atmosphere which forms aerosols. Air-sea exchange of particulate matter contributes to the global cycles of carbon, nitrogen, and sulfur aerosols.

Aerosols originate from a wide variety of natural and anthropogenic sources. Anthropogenic aerosols are aerosols as a result of human activities which include burning fossil fuels, biomass burning, direct emissions, etc. Natural aerosols include volcanoes, condensation, forest fires, botanical debris, etc. The open ocean is one of the major sources of natural aerosols, producing annually 1015-1016 g of sea-salt aerosols. Sea-salt aerosols, together with wind-blown mineral dust, and naturally occurring sulfates and organic compounds, are part of natural tropospheric aerosols. Sea salt aerosols influence radiative transfer directly by scattering solar radiation and indirectly by altering cloud droplet size distribution and concentration and contributes to atmospheric corrosion (Gong et al., 1997; Syed, 2006).

It is believed that much of the removal of atmospheric aerosols occurs in the vicinity of large weather systems and high altitude jet streams, where the stratosphere and the

lower atmosphere become intertwined and exchange air with each other. In such regions, many pollutant gases in the troposphere can be injected in the stratosphere, affecting the chemistry of the stratosphere. Likewise, in such regions, the ozone in the stratosphere is brought down to the Aerosol measurements can also be used as tracers to study how the Earth’s atmosphere moves. Because aerosols change their characteristics very slowly, they make much better tracers for atmospheric motions than a chemical species that may vary its concentration through chemical reactions. Aerosols have been used to study the dynamics of the Polar Regions, stratospheric transport from low to high latitudes, and the exchange of air between the troposphere and stratosphere. Aerosols can act as sites for chemical reactions to take place (heterogeneous chemistry). The most significant of these reactions are those that lead to the destruction of stratospheric ozone. Aerosols can be found in many typical household products such as hairsprays, some typewriter correction fluids, deodorants, dry cleaning agents, petrol lighter fuel, etc. There are serious risks associated with inhaling aerosols. Some immediate side effects include sneezing, coughing, vomiting, diarrhea, slurred speech, double vision, drowsiness, and muscle pain. Long-term use of aerosols can damage the liver, kidneys, lungs, heart, and brain. Sometimes the damage will heal once the huffing has stopped; sometimes however, it is permanent.

Other risks associated with the inhaling of aerosols include:

  1. Suffocation – users have often passed out while inhaling with a bag over their faces and died of suffocation.
    1. Heart failure – results from strenuous activity immediately after inhaling.
  1. Depression – some users get depressed, often resulting in suicide attempts.

                        Statement of problem

The atmosphere contains more than just molecules of gases, there are also small (micro and submicron) sized solid or liquid particles, which are called aerosols. Aerosols come from natural sources such as condensation, freezing of water vapour, volcanoes, dust storms, forest and grassland fires, vegetation and sea spray. These particles affect the composition of the natural atmosphere. Aerosols are also, formed from human activities such as burning fossil fuels and biomass, ploughing or digging up soil (Hess and Schult, 1998). This anthropogenic contribution to the atmospheric aerosol loading is not well established, neither is the level of the total aerosol loading currently well defined (Andreae, 1996). Atmospheric aerosol particles consist of a mixture of different substances (Andreae, 1996) such as organic matter, dust and sea- salt. Organic matter constitutes an important fraction of aerosol mass, both in remote and urban locations; the presence of organic compounds in aerosol particles is due to primary emission and secondary organic aerosol formation (Gilardoni et al., 2000). Atmospheric dust constitutes of Na, Mg, Al, Si, P, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ba, As and Pb (Bates et al., 2008).

Sea-salts aerosols are chemical caries of species containing Cl, Br, I and S. The Br and Cl, once mobilized by sea salt inorganic produces gaseous Br2 and Cl2 which contributes in atmospheric Ozone depletion (Von Salzen and Dchlunzen, 1999; Hallquist et al., 2003). Sea salts aerosols are of high concentrated salt origin and can be propagated downwind to highly industrialized region and cause corrosion to industries especially those located offshore (Syed, 2006). These aerosol types also exert a strong influence on solar radiation, cloud formation, meteorological variables and chemistry of the marine atmosphere. The coastal region of Lagos has high concentration of sea salt aerosol which is a major pollutant from Atlantic Ocean in that region. Sea-salts are

considered to be one of the major contributors to the total solid particles and also referred to as particulate matter present in the atmosphere (Witek et al., 2000).

In the atmosphere, aerosols are regarded as pollutants because, they influence the Earth’s climate system; both solar and terrestrial radiation budget impair visibility by scattering and absorption and indirectly by providing the condensation nuclei for cloud droplets. As well as influencing tropospheric photochemistry (Ina et al., 2002; Highwood et al., 2000; Roberts et al., 2000; Bates et al., 2008; De Gouw et al., 2008).

Aerosols ³ 1 and

mm in diameter (coarse particles) are derived from soil dust and sea

salt (Raes et al., 1 995). Upon deposition, aerosols can harm humans, sensitive aquatic as well as terrestrial ecosystems (Smimov et al., 2002; Bates et al., 2008). A measure of the extent to which aerosols affect the transmission of sunlight is known as atmospheric aerosol thickness (James, 1995; David, 1998). The intensities of aerosols within an area are an indication of the levels of loading across that region. Therefore this study investigates the transport profile and source-sink system for sea salt aerosols over the coastal region of Lagos by utilizing the GPS information of the study region to simulate meteorological variables and aerosol data over the area from the Air Resource Laboratory (ARL) website.