Abstract

Air quality in Port Harcourt had reached such an alarming level that particulate matter has been observed to be literally falling out of the atmosphere. This has led to outcry from several quarters asking for the situation to be addressed. The problem is that government has not been able to address the fundamental issues involved, namely the sources, the potential impact and how to control the episode. In this regard, the Centre for Occupational Health, Safety and Environment (COHSE) decided to set up a monitoring station. Daily monitoring readings obtained were astronomical. Some of the readings were far above both the Federal Ministry of Environment (FMEnv) and WHO exposure limits. Results reveals that particulate matter especially PM_2.5 and PM₁₀ exceeded the exposure limits set by both FMEnv and WHO by up to 90 per cent. Emission sources are recommended to be regulated.

1. Introduction

The current soot episode in Port Harcourt and its environs in Rivers State has brought air pollution to the forefront of debate and research. Several groups such as NGOs, regulatory agencies and foreign missions in Nigeria have also expressed their concerns. Port Harcourt is an industrial port city, but in addition to industrial and vehicular air pollution the current soot problem is linked to illegal refineries and some very poorly operated industrial flares and plume stacks.

Air pollution is a concern to many people as it directly influences the quality of human health, especially respiratory problems, heart and lung diseases, and may in extreme cases cause death. Children are at greater risk as they are generally more active outdoors and their lungs are still developing, while elderly people are also sensitive to some serious types of air pollution ².

The change in atmospheric concentration of any pollutant is affected by source strength or emission rate and meteorological factors such as rain, sunlight, geography, cloud cover, moisture, and weather patterns. The elevated levels of particulate matter settling on Port Harcourt has been obvious even to the least illiterate as soot is visibly seen dropping from the atmosphere or blown around. The result of this investigation will be compared to Federal Ministry of Environment (FMEnv) Nigeria and the WHO permissible emission standards (Table 1).

Recently the government of Rivers State of Nigeria has set up a task force with the responsibility of finding out the source of the increased particulate matter pollution and curbing it. Membership is drawn from the Department of Petroleum Resources, State Ministry of Environment and House of Assembly but none from the academia.

From studies already carried out in the Niger Delta in the last ten years, the critical air pollutants are: sulphur dioxide (SO₂), nitrogen oxide (NO₂), carbon monoxide (CO), ground level ozone (O₃), lead (Pb), fine particles less than 10 micrometres (PM₁₀) and nitric acid (HNO₃). ¹. Table 2 summarizes the effects of these pollutants on human health.

2. Materials and Methods

Port Harcourt the erstwhile garden city of Nigeria is the capital of Rivers State of Nigeria. Its geographical coordinates are 4° 47' 21" North, 6° 59' 55" East. Port Harcourt is the capital and largest city of Rivers State, Nigeria. It lies along the Bonny River and is located in the heart of the Niger Delta. As of 2016, the Port Harcourt urban area has an estimated population of 1,865,000 inhabitants, up from 1,382,592 as of 2006

With the discovery of crude oil in commercial quantities in 1956 at a place called Oloibiri. This turned Port Harcourt's economy into petroleum when the first shipment of Nigerian crude oil was exported through the city in 1958. By the benefits of the Nigerian petroleum industry, the city further developed, with aspects of modernization and industrialization. Multinational Oil companies that currently have offices in Port Harcourt include Royal Dutch Shell, Total, Agip, Chevron and others.

With the activities of these firms involving gas flaring, including nefarious activities of hoodlums engaged in illegal refining nearby along the Bonny River creeks with crude technology comes a peak in particulate pollution.

The monitoring location was ‘Mgbuoba’ in Port Harcourt as indicated on the map (Figure 1).

1. Davies Vue weather station to measure parameters mounted at 10m high

2. Garmin model 64S GPRS for station identification

3. CW-Hat 200S Particulate Monitor - For hourly monitoring of PM_2.5 and PM₁₀ particulate matter

4. AMSTAT USA Multifunctional Environmental Meter - For hourly monitoring of Temperature, humidity and wind speed.

Levels of particulate matter PM_2.5 and PM₁₀ including meteorological data (temperature, humidity and wind speed). Observations continued throughout the day from January 4, 2017 till the last day in September 2017. This cover the dry and wet seasons.

3. Results and Discussions

Results presented in this paper cover January to February that represents the dry season and May data that represents wet season in Nigeria.

The results of the particulate matter and meteorological parameters are plotted in Figure 2. Relative humidity and temperature tend to have minimal effect on particulate matter concentration.

The effect of wind on particulate matter distribution is shown in Figure 3 for the dry season. Both the PM_2.5 and PM₁₀ peaked during calm periods (0 m/s wind speed). Thus, the effect of wind dispersion on particulate pollution is strongly at work in this situation. In Figure 4, the concentration of PM_2.5 went up to 341 µg/m³ and PM₁₀ was at a concentration level of 781 µg/m³ at 3.32am on Monday February 13, 2017 when the wind was 0 m/s. PM_2.5 however was at a concentration level of 22 µg/m³ and PM₁₀ was 45 µg/m³ at 11.57am on Thursday January 26, 2017.

The relationship is shown in Figure 4 from which astrong correlation was established with a R² = 0.98. with the observations in this study and others on particulate concentration due to oil activities in the Niger Delta region of Nigeria, is approximately 50 percent of in ratio of 2.2 to 1.

Percentage distribution of and of particulate concentration levels are shown in Figure 5 and Figure 6 respectively. Figure 5a demonstrates that over 70% of the PM_2.5 particles are of the range 20 to 170 while Figure 5b shows that over 60% of the PM_2.5 particles exceeded 50 .

Figure 6 shows that 70% of the PM₁₀ particles monitored were in the range 70 to 310 .

The high particulate pollution levels observed during the dry season started to decline as the rainy season sets in (Figure 7). In May the highest observed daily reading are PM_2.5 - 28µg/m³ and PM₁₀ - 69µg/m³ and because the rains scrub the air of particulate matter and other pollutants readings of PM_2.5 < 20µg/m³ and PM₁₀ < 50µg/m³ are predominant Table 2. The level of particulate matter is expected to continue to drop in subsequent months of the rainy season. This downwash of pollutants by rainfall may result in secondary pollutant(s) polluting water bodies and soil. This is the case with NO₂ which forms HNO₃ that acidifies surface water, soil and soil water.

4. Conclusion

Nigerian cities are developing fast and experience the problems of development. Air pollution is a major problem of development. We should see our problems as such that has to do with development. The cooperation of all, corporate and private individuals is solicited for a healthy environment to rid the environment of this dangerous inhalable and respirable particulate matter.

References