Dissolved Oxygen
Dissolved Oxygen
| The graphs below show dissolved oxygen concentration and saturation at the sampling sites in the Nequasset Watershed. DO Concentration measures how many gaseous milligrams of oxygen are available per liter of water, and DO Saturation tells us how much gaseous oxygen is in the water relative to its carrying capacity, which is a function of temperature. |
| Colder water can hold more DO than warmer water, explaining the above graph’s general trend: DO rises as winter approaches, and steadily decreases once winter turns to spring and temperature increases. |
| As seen in these graphs, Wright Lane and Delano Rd. have suprisingly low DO values in the early fall. This may be because the early fall is the driest time of year, and lack of flowing water from channels into these bodies leave the stagnant water with very low levels of DO. As soon as mid-October arrived, though, the onset of late fall rains led to a general "flushing" of stagnant water out of the tributaries, the turbulent mixing from which increased DO levels. Even though colder water can hold more DO, and the winter exhibits an overall rise in DO levels, the graphs show that DO actually decreased during the coldest parts of the winter. These minor decreases can be attributed to the effect of ice cover on limiting the diffusion of DO from the atmosphere into the water, especially in the wetlands and ponds where water is more still to begin with. |
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The clear outlier in each of these graphs is the Meadow Road tributary. Meadow Road is the closest of our sites to upstream wetlands, which may explain why its DO is drastically lower than the other sites. DO is used to decay organic material, and so the wetlands nearby consume a lot of DO, and therefore cause lower DO levels downstream. |
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