Natural sources of organic matter include plant decay and leaf fall. However, plant growth and decay may be unnaturally accelerated when nutrients and sunlight are overly abundant due to human influence. Oxygen consumed in the decomposition process robs water quality monitoring pdf aquatic organisms of the oxygen they need to live. Organisms that are more tolerant of lower dissolved oxygen levels may replace a diversity of more sensitive organisms.
In this test, the dissolved oxygen level of a water sample is measured five days after it was collected. On the day of collection, the DO level is measured in an initial sample. The biochemical oxygen demand is the difference between DO levels in the two samples, so the level of the original sample must be known. Follow directions through step four of the DO measurement. The sample bottle which was stored in the paper bag and should be placed in the dark and incubated for five days at 20 degrees Celsius, which is approximately room temperature. If no incubator is available, place the sample bottle and bag into a “light-tight” drawer or cabinet. After five days, determine the DO level of the sample by repeating steps five and six of the treatment procedure and all steps of titration and cleanup.
Follow instructions for the dissolved oxygen test. Turbidity is a measure of cloudiness in water. The more turbid the water, the murkier it is. Turbidity can be caused by soil erosion, waste discharge, urban runoff, bottom feeders like carp that stir up sediments, household pets playing in the water, and algal growth. Turbid waters become warmer as suspended particles absorb heat from sunlight, causing oxygen levels to fall. Warm water holds less oxygen than cooler water.