Influence of meteorological variables on air characteristics of Onitsha, Nigeria

Abstract

This study evaluated the influence of prevailing meteorological characteristics on the concentration of air parameters in Onitsha metropolis, Anambra State, Nigeria in 2019. The information is required in meteorological forecasts, wind climatology, weather characteristics for planning control measures which might improve or worsen air quality, essential to evaluating air pollution control in the study area. A total of forty sampling points and one control point were selected and used for the study across Onitsha metropolis. The sampling points were selected in accordance with WHO guidelines for sampling point selection. Air quality and meteorological data were collected in-situ from primary sources in the field via portable air quality instrument and Kestrel 4500NV weather tracker. The results showed that wind direction was predominantly North-east in the dry season and South-west in the wet season. Temperature levels in the area were found to be higher in the dry season than in the wet season. Conversely, relative humidity levels were higher in the wet season than in the dry seasons. It also showed that some parameters such as SO2, NO2, H2S, VOC2, CO, PM2.5 and PM10 had higher concentrations in the dry season than in the wet season. On the other hand, TSP, PM10 and PM7 showed higher concentrations in the wet season than during dry season. High levels of measured air quality parameters were recorded around major junctions and market places within Onitsha, which are harmful to public health. Air movements influenced the fate of air pollutants; If the air was calm and pollutants couldn’t disperse, then the concentration of these pollutants would build up. On the other hand, when strong, turbulent winds blew, pollutants dispersed quickly, resulting in lower pollutant concentrations. The study further showed that transportation activities and trading activities at the market places were the main sources of high concentration levels of air parameters in the study area. Health impact assessment should be conducted in Onitsha metropolis for residents. State government should enforce compliance laws and regulate the activities of industries in the areas. The findings showed that meteorological data could help identify the source of pollutants, predict air pollution events, simulate and predict air quality using computer models. Identifying the sources means planning to reduce the impacts on air quality by anthropogenic activities.