Water quality methods

Understanding the variability of water quality parameters remains a serious challenge, requiring measurements for a long enough time over a great enough area. A CTD is used to examine these parameters. CTD stands for Conductivity-Temperature-Depth sensor. These instruments are commonly set up to measure pH and dissolved oxygen also.

We use them in 2 ways:

1. To measure multiple stations manually

2. Deployed at one station for continuous time series measurements

The CTDs we have used include:

1. SeaBird Electronics

2. Hydrolab

3. Yellow Springs Instrument Co. (YSI) 6920 and 85

4. In-Situ, Inc. Trolls 8000 and 9000

Here is how a CTD is set up for deployment:

The nutrient analyzer we use is made by SubChem Systems. It has a submersible reagent delivery module and optical detectors for in situ spectrophometric and fluorometric measurements of total nitrogen, nitrite, ammonium, phosphate, and iron.

In the salt ponds, we keep the instrument on the deck of the boat and pump water past it. We can record real time measurements throughout the pond, which allows the identification of plumes. This is a significant advancement over point measurements.

We also have the capability of towing the instrument, allowing greater flexibility in terms of profiling deeper waters.