Assessment Of Air Quality, Noise Levels And Heavy Metal Concentrations During Dry And Rainy Seasons From Industrial Areas Of Blantyre City, Malawi

Abstract

This research investigated concentration of air quality, heavy metals and noise levels from industrial areas in Blantyre City, Malawi. Air, noise, and soil samples were collected in both dry and rainy seasons at 15 industrial sites based in Makata, Limbe, Maselema, Chirimba and Maone in Blantyre. Sampling and analysis of air, noise and soil employed the use of standardized methods detailed in the American Public Health Association (APHA), Canada Standards, English Standards as well as Malawi Standards (MS). Air was analyzed for Carbon Monoxide (CO), Total Suspended Particles (TSP), Particulate Matter 10 (PM10) and Particulate Matter 2.5 (PM2.5). Heavy metals were assessed using Atomic Absorption Spectrophotometry (AAS). Soil was analyzed for pH, electrical conductivity, Cadmium (Cd), Copper (Cu) and Zinc (Zn). Noise levels were also recorded using a noise level meter. In the rainy season, the average concentration values of CO, TSP, PM10, and PM2.5 were 0.49 ± 0.65 mg/m3, 85.03 ± 62.18 μg/m3, 14.65 ± 8.13 μg/m3, and 11.52 ± 7.19 μg/m3, respectively. Dry season average concentration values increased to 1.31 ± 0.81 mg/m3, 99.86± 30.06 μg/m3, 24.35 ± 9.53 μg/m3, and 18.28 ± 7.14 μg/m3. Noise levels remained below public MS and WHO standards (85 dB). Chirimba AP had the highest mean Zn concentrations of 822 mg/kg in the rainy season and 579 mg/kg in the dry season. Maone NM had the highest Cd concentrations, measuring 2.09 mg/kg in the rainy season and 3.06 mg/kg in the dry season. Chirimba AP also had the highest Cu concentrations with levels of 105 mg/kg in the dry season and 79 mg/kg in the rainy season. The study found that the 87 % of soil sample concentrations were in line with England's stipulated standards for heavy metal concentrations, with exceptions noted in specific instances like Chirimba AP and Makata LF, where concentrations surpassed the defined limits signifying a health concern. In the rainy season, the range of soil mean pH was 6.3 - 7.83 while in the dry season it was 6.67 - 8.15. In the rainy season, the range of soil mean electrical conductivity was 24.3±0.35 μS/cm - 265±0.42 μS/cm while in the dry season it was 43.8±0.49 μS/cm - 2353±5.508 μS/cm. Source apportionment of air quality parameters as well as heavy metals showed various factors contributing to the respective concentrations. A geo-accumulation index analysis of heavy metals in soil was done to assess potential contamination risks and Zn was shown to be a major contaminant, presenting an ecological and pollution risk. The results of the source apportionment analysis using Positive Matrix Factorization (PMF) model indicated that air and heavy metal pollution were mainly caused by (1) metal processing and manufacturing industries, (2) plastic manufacturing industries (3) cement manufacturing industries, (4) food manufacturing industries, (5) beverage manufacturing industries and (6) furniture manufacturing vii industries. It was recommended for periodic sampling be done to observe the seasonal pollution trends considering potential impacts on public health and environmental sustainability. Further studies should look at factors affecting the dynamics of PMF in Blantyre City. This will help in putting up measures that can help to control the release of pollutants and ensuring public health.