Assessment of Ambient Air Quality around Ihetutu Minefield, Ishiagu, Nigeria

Abstract

This study assessed the levels of physicochemical characteristics and heavy metals in ambient air around Ihetutu community in Ishiagu, Nigeria, to evaluate the impact of prolonged Pb-Zn mining and several other related activities on air quality in the area. Particulates, heavy metals, microclimatic and gaseous parameters in ambient air were analyzed for the assessment. Sampling and quality measurements were done during rainy, late rainy, dry and late dry seasons between 2018 and 2019, from study and control areas. Samples were analyzed for particulates and heavy metals in the laboratory while microclimatic and gaseous parameters were measured in-situ using standard field equipment and procedures. Mean and seasonal concentrations of parameters were determined to evaluate the ambient air quality at various locations in the study area. Results showed high mean values of some parameters including; ambient temperature (35.19oC), Relative Humidity (65.78%), SO2 (0.33ppm), NO2 (0.30ppm), PM10 (89.73µg/m3), Cu (0.03mg/L), Zn (0.06mg/L), Fe (0.39mg/L), Mn (2.28mg/L), Ni (0.04mg/L) and Pb (0.05mg/L). Highest Noise level in the study area was 60.40 dB(A). SO2 and NO2 were below detection limits during the dry seasons, but with mean levels above daily average limits of DPR, NESREA, and WHO, due to their high levels during the rainy seasons, except at Amaonye Square. CO mean levels were above FMEnv daily average limit but within DPR limit. PM10 mean values were within NESREA recommended daily average limit while dry season values were above. Zn and Fe pollution along the stations were in the order of SAS3>SAS4>SAS5, while Pb pollution was SAS3>SAS4=SAS5. Generally, trend of heavy metal pollution was Mn>Fe>Pb>Zn>Cd=Cu=Ni. Highest positive correlation within the heavy metals was between Zn and Fe (r = 1.000). There were also no statistically significant differences in means of the parameters among sampling stations (p>0.05). The results revealed pollution of ambient air in the area by heavy metals and gaseous substances, especially around the mining sites and high traffic areas. Proper monitoring of the operations of mining companies and other artisan activities is recommended, to ensure that ambient air status in the area is excellent and within standard guidelines.