249 Table 1 – Performance evaluation of OPC N3 sensor with respect to the reference instrument. Performance metrics Target value Dust type OPC N3 Linearity Coefficient of determination (R2) ≥ 0.70 Coal 0.97a Iron ore 0.77a Bias Slope 1.0 ± 0.35 Coal 0.51 Iron ore 0.82a Intercept (b) -5 ≤ b ≤ 5 µg m-3 Coal 9.8 Iron ore -7 Error Normalized root mean square error (NRMSE) ≤ 30% Coal 60 Iron ore 34 aMeets US EPA criterion 3. RESULTS AND DISCUSSION 3.1 Surface iron ore mine A significant variability in PM levels was observed at different depth in iron ore mine, with higher variability in PM10 compared to PM2.5 ad PM1. Higher PM levels (PM10: 228 μg m3, PM2.5: 84 μg m-3, PM1: 35 μg m-3) were recorded at the pit bottom location and lowest was found to be at the pit top (Figure 4). Figure 4 – PM concentration at different vertical depth in surface iron ore mine
RkJQdWJsaXNoZXIy MTM0Mzk2