Air Quality Monitoring

Below you will find detailed descriptions of the equipment and methods used by the Air Quality Program to measure ambient conditions on the Reservation. Real time measurements from the instruments at the Air Monitoring Station can be viewed online here.

Weather

Weather Station Equipment

Current weather conditions are measured using a set of instruments, located at the top of a 10m (30 foot) tower, next to the Environmental Management-A Office and air quality monitoring station platform.

The meteorological station measures wind speed, wind direction, max wind gust, temperature, relative humidity, precipitation, barometric pressure, & solar radiation; and calculates resultant wind speed, resultant wind direction, wind direction standard deviation, & dewpoint temperature.

  • A lightening rod protects the instruments.

  • The anemometer (the rotating cups) measures wind speed up to 125 mph. The wind vane measures wind direction.

  • The pyranometer measures solar radiation.

  • The barometer is located in a shelter on the side of the building.

Rainfall is measured with a tipping bucket, mounted on the station platform. The Tribe also utilizes a National Weather Service approved standard 4" gauge for collecting precipitation data- one of the most reliable and relatively accurate precipitation gauges available. The gauge can collect up to 11", and is read in increments of .01” by reading the inner tube. Amounts over 1" can be transferred to the tube for cumulative readings.

Web Cameras

The Tribe uses 2 cameras, one pointing at a fixed location, approximately 13 miles from the Reservation, and featuring Winuba/Mt. Tom, and one pointing southeast down Owens Valley, to collect information on visibility. Images are transmitted to the station servers once an hour, in PST. These images correspond to real time information on meteorological and air quality conditions, making it possible for users to assess the contribution of various conditions to visibility.

Ambient Air Quality

To protect the health of reservation residents, air quality is monitored on the Bishop Paiute Reservation.

The Tribe operates 3 air quality monitors, all of which receive 3rd party audits annually. Two instruments are used to measure the concentration of very small particles that are suspended in the air (particulate matter). These measurements are important because the particles are small enough to lodge in the human lung and cause or aggravate health problems. In the Owens Valley, particulate matter is the primary air pollutant and there are two primary sources, dust and smoke.

The Tribe also operates a continuous monitoring system for ground-level ozone. Ozone exists in the Owens Valley largely due to wind transport from more densely populated areas and major traffic corridors. Currently, the Tribe's 1-hour and 8-hour ozone standards are .09 ppm and .07 ppm, respectively. All monitoring systems are all federally approved and use certified instruments, and are audited annually. 

Particulate Monitoring

  • The Tribe collects measurements for two particle sizes. PM10 refers to particles that are less than 10 microns in diameter (about 8 will fit in the diameter of a human hair). PM2.5 refers to particles that are less than 2.5 microns in diameter. Generally speaking, high PM-10 measurements reflect dust events and high PM2.5 measurements reflect smoke events.

    Particulate matter is measured in micrograms per cubic meter of air. Standards have been established by the US Environmental Protection Agency (US EPA) and by the State of California. When the concentration of particulate matter exceeds these standards, health can be adversely affected. All standards refer to the average concentration in a 24-hour period. The Bishop Tribe's standards are the same as the California standards for both particle size.

    PM10:

    Federal: 24-hour average concentrations must not exceed 150 micrograms per cubic meter

    California: 24-hour average concentrations must not exceed 50 micrograms per cubic meter

    PM2.5:

    Federal: 24-hour average concentrations must not exceed 35 micrograms per cubic meter

    California: Default to federal standard

    For more detailed information about AQI from Great Basin Unified Air Pollution Control District click here.

  • The instruments used are a 1405 TEOM for FEM PM10, and a T640 light spectroscopy monitor for FEM PM2.5. These are EPA certified, sophisticated and extremely accurate monitoring devices. They measure the concentration of particulates in micrograms per cubic meter of air. A microgram is one-millionth of a gram.

    The TEOM operates on a simple principle. Particles are selected for size and drawn into the instrument in a temperature-controlled column. They are deposited on a filter that sits at the top of a quartz element (the weighing device). This element oscillates at a known frequency. As material accumulates on the filter, the frequency of oscillation is changed in a way that is directly proportionate to the mass of particulate. This frequency is measured every 2 seconds along with the flow of air through the instrument and is used to calculate the mass of particles that are in the volume of air, as instantaneous, 1-hr, 8-hr, and 24-hr average concentration values, measured in micrograms per cubic meter.

    The T640 measures particles by light spectroscopy, where particles of different sizes scatter LED sourced light in measurable quantities of intensity. The particles enter in the sample stream of air pumped in at a low volumetric flow through a conditioner into the instrument. The monitor can also measure different size particles, i.e. PM10, PM10-PM2.5, (though modifications are required to do this for FEM criteria).

Ozone Monitoring

Ground-level ozone is a respiratory irritant that may aggravate a variety of respiratory problems, including asthma. The Tribe uses one instrument to measure ozone. It measures the concentrations of a gas composed of three oxygen molecules (O3).

Ozone is measured using a Thermo 49i analyzer. This instrument samples the air and determines the amount of ozone using ultraviolet photometry. Ozone is measured in parts per billion (ppb).

  • The instrument operates on the principle that ozone molecules absorb ultraviolet light at a known wavelength of 254 nanometers and the degree to which ozone is absorbed is directly related to the ozone concentration according to a mathematical formula, known as the Beer-Lambert Law.

    A small pump draws air through an inlet on the roof of the EMO building. The sample stream is then spit into a reference stream that passes through an ozone scrubber and a sample stream. Solenoid valves allow the two streams between two cells. The UV light intensities in each cell are then measured and the streams are switched. The analyzer outputs the average concentration on the front panel of the instrument and data are also transmitted to the data logger and subsequently to the internet.

    The analyzer is challenged biweekly with span/zero and and 1- point precision calibration gases, generated by a dedicated calibration instrument. The monitoring system uses a Teledyne 703U calibrator. Periodic multipoint calibrations ensure the range of instrument measurements is conforming to QA standards.