Air Quality Changes under the Influence of Cut-Off Lows and Omega Blocking Patterns and Associated Health Risks in a Coastal Mediterranean Region: Case of Bizerte, Northern Tunisia

Abstract

The study of the daily and diurnal variability of NO, NO2, surface O3 and PM10 was carried out in urban Bizerte (Northern Tunisia), from January to March, 2013. The main results showed three distinct periods depending on multi-scale sources and meteorology. The first period, (≈20% of total cases) influenced by moderately stable conditions, was characterized by a slight excess of NO due to traffic emissions. The second period, (≈ 60% of total cases) associated with moderately unstable conditions, was devoid of any significant impact of sources. The third period, (≈ 20% of total cases) distinguished by noteworthy excess of O3 and PM10, was attributed to a marked effect of succeeding Cut-off lows and Omega blocking patterns. Under these conditions, the scatter plots of NO, NO2, and O3 versus NOx for daytime and nighttime showed good polynomial fit curves with high R2 values for NO and NO2 only. Under both moderately unstable and stable conditions, significant negative correlation coefficients between O3 and NOx were found to be 0.53 (p < 0.05) and 0.50 (p < 0.05) for daytime and nighttime, respectively. Under Cut-off lows and Omega, an absence of any significant correlations between O3 and NOx was noticed. Under Cut-off lows, the good linear regression fits between OX (=O3 + NO2) and NOx illustrated high NOx independent contributions, possibly attributed to the biogenic VOCs effect. The investigation of the air quality index (AQI) for NO2, PM10 and O3 (running 8-h mean) highlighted the significant effect of both O3 and PM10 only under Cut-off lows and Omega which were retraced by poor to very poor air quality categories.