Welcome to the Coquitlam River: Iron Ochre!
A Little History of Coqultlam River:
The Coquitlam River is a tributary of the Fraser River. The river's name comes from the word Kʷikʷəƛ̓əm which translates to "Red fish up the river". The name is a reference to sockeye salmon that once occupied the river's waters. 1 The Kwikwetlem First Nations have lived in the region for over 9,000 years and are renowned for their canoe and paddle craftsmanship. They have lived throughout the Coquitlam watershed and relied on fishing, gathering, and trade with other First Nations living along the Fraser River. 2
European settlers first arrived in the region in the mid 1800's and began using the river for food and for water and later for power. The first dam was built at the mouth of Coquitlam Lake in 1892 to provide a source of drinking water for the growing colony of New Westminster. In 1905, the Vancouver Power Company completed construction on a second dam and a tunnel to nearby Buntzen Lake for power generation . In 1915, an even larger dam was contructed due to increased power demand. However, unlike in previous dams, fish access to the lake was completely blocked, further impacting the river's ecology. 3
The watershed was logged throughout the 1900s and a gravel pit was mined along its banks causing heavy sediment loads especially during high precipitation events. The area is surrounded by residential areas and light industry as well which has contributed to further streamside erosion and pollutants.
Earthcache requirements:
At gz Waypoint #1: you should find a sign from the City of Port Coquitlam that discusses the natural process that occurs at this site.
You have 2 questions to answer and these can be answered by reading the sign:
1. Why does the creek look rusty in this area? Describe the process in a sentence or two.
2. How would you differentiate oil sheen from a sheen produced by iron-oxidizing bacteria?
Waypoint #2:
3. After reading over the sign and answering the questions, walk downstream to waypoint #2 by the leaning tree on the bank. Where do you see examples of iron ochre dis-coloration? (by near bank, by far bank or some other part of the stream?) Take a picture of yourself and an example of the iron ochre discolouring with you or a part of you in the picture. Were you able to see some of the gooey material or just the rust discoloration?
Discussion:
Iron Ochre is a substance created by a natural process that involves the oxidation of dissolved iron by bacteria. When de-oxygenated water reaches a source of oxygen, iron bacteria convert dissolved iron into an insoluble reddish-brown gelatinous slime that discolours stream beds and can stain plumbing fixtures, clothing or utensils washed with the water carrying it. 4
Organic material dissolved in water is often the underlying cause of an iron-oxidizing bacteria population. Groundwater may be naturally de-oxygenated by decaying vegetation in swamps. 5
Iron Oxidizing Bacteria Process:
| A. Aerobic Decomposition |
B. Iron Dissolution |
C. Ochre Water |
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* pictures are from the sign at gz
Why does the creek look rusty and polluted?
Iron ochre is a naturally occurring, rusty coloured substance that develops when groundwater containing dissolved iron is exposed to oxygen. Dissolved iron is introduced into the water when groundwater passes through areas full of organic matter like peat, rotting logs or plants that have been buried underground. When the water emerges from the ground and is exposed to oxygen in the atmosphere, the dissolved iron is oxidized by bacteria which causes water to look rusty and produces a rainbow sheen at its surface.
Natural Sheens:
To differentiate an oil sheen from a sheen produced from iron-oxidizing bacteria, break the sheen up with a stick:
- an oil sheen will swirl and reform
- a natural sheen will break up into small separate platelets
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References:
1 https://en.wikipedia.org/wiki/Coquitlam_River
2 https://en.wikipedia.org/wiki/Coquitlam_River
3 https://en.wikipedia.org/wiki/Coquitlam_River
4 https://en.wikipedia.org/wiki/Iron-oxidizing_bacteria
5 https://en.wikipedia.org/wiki/Iron-oxidizing_bacteria