Phase 2 – Water Quality Monitoring Equipment

Methods

Long-term continuous water quality monitoring has been impossible in the past, but recently developed technology has made it possible to use for environmental studies. UV-visual spectrophotometers can know be left in the field to analyze the water on a regular basis. The water quality probes that we are using can measure turbidity, nitrate, dissolved organic carbon (DOC), and total organic carbon (TOC) by shining UV and visual light through the water along the measuring path.

Figure 1. Two UV-visual spectrophotometers that will be installed in the tidal stream to continuously monitor the water quality.

Having a clean measuring path for the light to shine through is critical for the spectrophotometer to produce accurate measurements. Cleaning during site visits is not adequate to ensure that the measurement path remains clear. Biofilm growth or sediment could easily cause the measurement path to be obstructed between site visits. The probes are manufactured such that compressed air can be used to clean the measurement path. There are two openings in the measurement path that direct air toward the measurement windows. The challenge is to supply compressed air to the probe in such a remote location. The research team has assembled an air compressor and tank within a small box for use in the field.

Figure 2 (left). Close up photo of the spectrophotometer measuring path.

Figure 3 (right). An air compressor set up to clean the measuring path and windows in the field.

The research site is located nearly 8 miles from the nearest paved road and about 5 miles from the nearest source power, so all of the equipment is powered using batteries and solar power. The air compressors require a large amount of power, so each monitoring station has been equipped with a 135 watt solar panel. The monitoring equipment also needs to be protected from the elements and wildlife. The large green equipment boxes prevent bears from destroying the equipment and minimize exposure to rain. The boxes are about 4 feet above the marsh to prevent water from getting to the equipment.

Figure 4. The equipment housing and solar panel required for the monitoring.