Question

A natural pond is producing a rotten egg like smell. After some investigation it was found that the smell was due to the presence of H2S in the lake.

a) What can you say about the concentration of dissolved oxygen in the pond?

b) What can you say about the form of manganese and iron to be found in the

pond? Explain.

C. Does this situation likely represent aerobic or anaerobic conditions? Explain.

Answer 1

a.Dissolved oxygen (DO) is the most critical indicator of a lake’s health and water quality. DO levels in natural waters are dependent on the physical, chemical and biochemical activities prevailing in the water body. Oxygen is added to aquatic ecosystems by aquatic plants and algae through the process of photosynthesis; and by diffusion at the water’s surface and atmosphere interface.   When the oxygen is used up in the bottom of the lake, anaerobic bacteria continue to breakdown organic materials, creating toxic hydrogen sulfide gas in the process. For a healthy game-fish population, oxygen levels in the 6-10 mg/L range are necessary. Respiration stress in most fish occurs when oxygen levels are reduced to 3-4 mg/L.

b.Nutrients like phosphorus, nitrogen, carbon, silicon, calcium, potassium, magnesium, sulfur, sodium, chloride, iron) are primarily transported to ponds and lakes via streamflow.When concentrations exceed 0.1 mg/L, iron precipitates on exposure to air, decreasing pond clarity, potentially clogging irrigation pipes, and encouraging iron bacteria, which affects the flavor of both fish and water. Levels greater than 0.3 mg/L can cause staining on buildings and sidewalks when the water is used for irrigation.

c.oxygen levels in the 6-10 mg/L range is necessory for aerobic oxidation when this leves lowers then oxygen supplyy get reduced aand it is harmful to auatic animal.if this pond contains H2S then obious condition is anaerobic, which is less oxygen content.