Dissolved Organic Carbon
Dissolved Organic Carbon (DOC) is used to describe the thousands of dissolved compounds found in water
that derive from organic materials (such as decomposed plant matter).
Mean (or average) DOC levels in Maine is 5.7 ppm (parts per million)
(from EPA
Environmental Monitoring and Assessment Program)
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Newbert Pond's tea colored water.
Newbert is located in a boggy area rich in organic matter. Water
flows through this debris and leaches out tannins and lignins, which
color the pond. This process is often compared to making a cup of
tea. |
DOC is organic material
from plants and animals broken down into such a small size that it is
“dissolved” into water. Some DOC molecules have a recognizable chemical
structure that can easily be defined (such as fats, carbohydrates, and
proteins) however most have no readily identifiable structure and are
lumped under the term humic or tannin substances.
The more recognizable types of DOC such as
soluble fats, proteins, and carbohydrates are often created within the
stream or lake from animal feces or decomposition of fish and insects.
This type of DOC is not pigmented and does not influence the color
of a lake or stream. However, DOC
imported from outside a lake or stream is created by the decomposition
of leaves and woody debris that have fallen around or in water. The plant
material is slowly broken down by organisms into very small particles that are
dissolved into water. Because they are not quickly fed on, they have more
time to hang out in the water and react with other molecules to
form complex structures that as explained above, are difficult to define
as any one type of compound. These humic or tannin substances also often have natural acids associated
with them (which can influence pH levels). Yellow to black in color, this humic
type of DOC is the most abundant kind found in lakes and streams and can
have a great influence on water color.
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