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A council monitors the water quality of a local river daily - HSC - SSCE Chemistry - Question 31 - 2011 - Paper 1
Question 31
A council monitors the water quality of a local river daily. The records for six days are shown in the table. During this period contamination from unknown sources w... show full transcript
Worked Solution & Example Answer:A council monitors the water quality of a local river daily - HSC - SSCE Chemistry - Question 31 - 2011 - Paper 1
Step 1
Propose possible sources of the contamination
Answer
One possible source of contamination is the high turbidity reading observed on Tuesday (67 NTU). High turbidity can often be linked to runoff from construction sites or urban areas, introducing sediment and pollutants into the water. The substantial increase in turbidity from 5 NTU on Monday to 67 NTU on Tuesday indicates a significant environmental change that could be attributed to human activities nearby.
Another possible source of contamination is the spikes in faecal coliform levels, particularly noted on Wednesday (512 cfu/100 mL) and Thursday (514 cfu/100 mL). Such high levels suggest the presence of sewage or animal waste, which could originate from sewer overflows or agricultural runoff during rainfall, introducing harmful pathogens into the waterway.
Both of these indicators—high turbidity and increased faecal coliform counts—are critical in assessing the health of the waterway and indicating potential contamination.