UTA Electric Bus Air Quality Monitoring Dataset Written By: Dr. Alexander Jacques, University of Utah Updated: August 2, 2023 --------------------------- This README describes the format and fields of the measurements observed as part of the UTA Electric Bus Air Quality Monitoring Study, conducted by the University of Utah and supported by Salt Lake County. --------------------------- This dataset is divided into monthly compressed comma-delimited files for each measurement platform. As of this update, there are five different platforms available: BUS01 - Instruments deployed on UTA Electric Bus 18153 BUS02 - Instruments deployed on UTA Electric Bus 18151 BUS03 - Instruments deployed on UTA Electric Bus 18152 BUS04 - Instruments deployed on UTA Electric Bus 23101 BUS05 - Instruments deployed on UTA Electric Bus 23103 Platforms installed include GPS positioning, bus-top ambient temperature and humidity, particulate measurements from either a Met One ES-642 Dust Monitor or Met One ES-405 Simultaneous Particulate Profiler, ozone measurements from a 2B Technologies 205 Ozone Monitor, and in some instances NOx measurements from a 2B 405 sensor. All platforms record sampled measurements from each instrument every 5 seconds, with the exception of the Met One ES-405 which has a data frequency of one measurement per minute. --------------------------- FIELD DESCRIPTIONS Missing observations/fields for a given timestamp are denoted with a -9999 value. The following fields may be seen in the comma-delimited files: Timestamp - The timestamp of the observational record in YYYY-MM-DDTHH:MM:SS format. Observations are recorded in Universal Time Coordinated (UTC), so 7 hours must be subtracted to convert to Mountain Standard Time (6 for Mountain Daylight Time). Latitude - The GPS latitude output (decimal degrees) Longitude - The GPS longitude output (decimal degrees) Elevation - The GPS elevation above sea level output (meters) GPS_Speed - A GPS-derived velocity for the movement of the platform (meters/second) GPS_Direction - A GPS-derived direction of movement for the movement of the platform (degrees - 0 means northward) GPS_RMC_Valid - A GPS-derived binary message on GPS validity (0 = suspect, 1 = valid) Battery_Voltage - The battery voltage recorded by the data logging device (volts) Bus_Box_Temperature - The temperature recorded inside the installation unit (degrees C) Bus_Top_Temperature - The ambient temperature recorded outside of the installation box on top of the bus (degrees C) Bus_Top_Relative_Humidity - The ambient relative humidity recorded outside of the installation box on top of the bus (percent) ES642_PM2.5_Concentration - The sampled PM2.5 concentration (ug/m3) ES642_Air_Flow_Rate - The air flow rate measured by the ES-642 (L/minute) ES642_Internal_Air_Temperature - The internal temperature of the ES-642 sampled air (degrees C) ES642_Internal_Relative_Humidity - The internal relative humidity of the ES-642 sampled air (percent) ES642_Internal_Air_Pressure - The internal air pressure of the ES-642 sampled air (hectopascals) ES642_Error_Code - The numeric error code recorded by the ES-642 (0 if no errors, integer > 0 if errors indicated) ES405_PM1_Concentration - The sampled PM1 concentration (ug/m3) ES405_PM4_Concentration - The sampled PM4 concentration (ug/m3) ES405_PM2.5_Concentration - The sampled PM2.5 concentration (ug/m3) ES405_PM10_Concentration - The sampled PM10 concentration (ug/m3) ES405_Air_Flow_Rate - The air flow rate measured by the ES-642 (L/minute) ES405_Internal_Air_Temperature - The internal temperature of the ES-642 sampled air (degrees C) ES405_Internal_Relative_Humidity - The internal relative humidity of the ES-642 sampled air (percent) ES405_Internal_Air_Pressure - The internal air pressure of the ES-642 sampled air (hectopascals) ES405_Error_Code - The numeric error code recorded by the ES-642 (0 if no errors, integer > 0 if errors indicated) 2B_Ozone_Concentration - The sampled ozone concentration (ppbv) 2B_Air_Flow_Rate - The air flow rate measured by the 2B 205 (L/minute) 2B_Internal_Air_Temperature - The internal temperature of the 2B 205 monitor (degrees C) 2B_Internal_Air_Pressure - The internal air pressure of the 2B 205 monitor (degrees C) 2B405_NO_Concentration - The sampled NO concentration (ppbv) 2B405_NO2_Concentration - The sampled NO2 concentration (ppbv) 2B405_NOX_Concentration - The sampled NOX concentration (ppbv) 2B405_Internal_Air_Temperature - The internal temperature of the 2B 405 monitor (degrees C) 2B405_Internal_Air_Pressure - The internal air pressure of the 2B 405 monitor (degrees C) 2B405_Air_Flow_Rate - The air flow rate measured by the 2B 405 (L/minute) 2B405_Cell_O3_Flow_Rate - The ozone cell flow rate measured by the 2B 405 (mL/minute) PM2.5_Data_Flagged - Binary indication that particulate concentrations should be used with caution (0 or 1 - additional info below) Ozone_Data_Flagged - Binary indication that ozone concentrations should be used with caution (0 or 1 - additional info below) --------------------------- DATA QUALITY CHECKS Numerous automated data quality checks have been applied to these data to help remove potentially suspicious or inaccurate observations. The unique nature of these deployments on top of electric buses, which share roadways with other vehicles, means that short-term/rapid changes in concentrations could be the result of real signals produced by adjacent vehicles at times. Users are encouraged to inspect data they may use further as well based on their needs (e.g. for temporal or spatial averaging purposes). The following checks have been applied to this dataset: 1) Data are omitted entirely if it has been determined that the GPS is malfunctioning 2) Particulate concentrations are set to -9999 if the ES-642 (ES-405) air flow rate falls below 1.5 (0.5) L/minute, or if the concentrations do not pass an unphysical high-frequency noise test. 3) Ozone concentrations are set to -9999 if the 2B air flow rate falls below 1.5 L/minute or if the concentrations do not pass an unphysical high-frequency noise test. 4) PM2.5_Data_Flagged is set to 1 if the ES-642 (ES-405) produces an error code, if the ES-642 (ES-405) internal relative humidity exceeds 50%, or if the ambient train-top relative humidity exceeds 70%. High RH can result in particulate concentrations that are much higher than official measurements when concentrations are elevated (official measurements are heated to remove water). There may be use cases where using this data is still reasonable, which is why it is provided with the flag attribute in place. 5) Ozone_Data_Flagged is set to 1 if the 2B internal temperature or installation unit exceeds 50 degrees C. The performance of the 2B sensors can degrade in extreme heat, so caution should be applied when this is the case.