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Water Quality Monitoring System
U-20XD Series
The Importance of Measurement Items in the Monitoring of Water Pollution in Lakes and Marshes
- Introduction
Since the 1960s, the most intractable problem in terms of water pollution has been human-made eutrophication. In this process, large quantities of various nitrogen, phosphorus and the like are dumped in bodies of water as part of industrial waste water. These substances nourish plant plankton, stimulating rapid growth and causing water pollution. To assess and solve this problem, the state of water pollution must be appraised from many different perspectives. Particular focus is needed on the lakes and wetlands, whose water plays such an important role in supplying the drinking and other daily needs of human populations. Data must be gathered from a broad area, encompassing tributary rivers and streams as well as lakes themselves. Other aspects need to be carefully studied as well, such as vertical distribution data and changes according to time and season.
- Elements of Water Quality Measurement
The U-20 multi-component water quality monitoring device, newly developed by HORIBA, boasts a versatile array of monitoring features. In addition to measuring 13 distinct items, the device provides highly precise measurement at depths up to 100m. It records longitude and latitude using GPS, and is capable of continuous monitoring for up to one month. In the example of measurements taken in Lake Biwa, the U-20 detected (1)pH, (2) water temperature, (3)conductance, (4)turbidity, (5)dissolved oxygen(DO), (6)oxidation-reduction potential (ORP), (7)nitrogen ions and ammonia gas, (8)chlorides, (9)calcium ions, (10)sodium and potassiumThe importance of each is described below.
- Other Measurement Items
Although the U-20 is not able to measure as of yet, there are two other items which are given much attention, namely phosphorus ions and chlorophyll.
· Phosphorusions
Lakes that are rich in phosphorus ions are generally on their way toward eutrophication. This is because plant plankton require the uptake of phosphoric acid ions for photosynthesis.
·Chlorophyll A
Knowing the size of the plant plankton population is an important part of understanding the state of eutrophication of a lake or wetland and the circulation of substances within it. However, the size of plant plankton organisms varies widely, from as large as an order of 1/10mm to picoplankton less than 2µm across. Therefore, an indirect method of gauging the volume of plankton is adopted, in which the quantity of chlorophyll in the water is measured. Chlorophyll A in particular is intimately connected with the process of photosynthesis. In fact, a fixed relationship is known to exist between water transparency and chlorophyll A, and between chlorophyll A and total nitrogen and phosphorus in the lake. These facts will be put to use as measurement ingredients in the sensor that HORIBA will develop.
References
- Yasoku Saijo and Osamu Mitamura, Survey Methods in Lakes and Wetlands, new edition
- Environment Agency, Water Pollution Control Division, Practical Handbook of Water Quality Measurement
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