Let's carefully evaluate the given contaminants for each well to determine which ones are found in toxic quantities.
First, we need to know the toxic thresholds for each contaminant:
- Arsenic: 0.01 mg/L
- Cadmium: 0.005 mg/L
- Cyanide: 0.2 mg/L
- Nitrate: 10 mg/L
- Thallium: 0.002 mg/L
- Barium: 2 mg/L
- Lead: 0.01 mg/L
Now, let's look at the contaminant levels in Well A:
1. Arsenic in Well A: 0.040 mg/L
- Threshold: 0.01 mg/L
- Since 0.040 is greater than 0.01, arsenic is found in toxic quantities.
2. Cadmium in Well A: 0.007 mg/L
- Threshold: 0.005 mg/L
- Since 0.007 is greater than 0.005, cadmium is found in toxic quantities.
3. Cyanide in Well A: 0.31 mg/L
- Threshold: 0.2 mg/L
- Since 0.31 is greater than 0.2, cyanide is found in toxic quantities.
4. Nitrate in Well A: 12 mg/L
- Threshold: 10 mg/L
- Since 12 is greater than 10, nitrate is found in toxic quantities.
5. Thallium in Well A: 0.000 mg/L
- Threshold: 0.002 mg/L
- Since 0.000 is not greater than 0.002, thallium is not found in toxic quantities.
Now, let's look at the contaminant levels in Well B:
1. Arsenic in Well B: 0.06 mg/L
- Threshold: 0.01 mg/L
- Since 0.06 is greater than 0.01, arsenic is found in toxic quantities.
2. Barium in Well B: 3.0 mg/L
- Threshold: 2 mg/L
- Since 3.0 is greater than 2, barium is found in toxic quantities.
3. Cadmium in Well B: 0.001 mg/L
- Threshold: 0.005 mg/L
- Since 0.001 is not greater than 0.005, cadmium is not found in toxic quantities.
4. Lead in Well B: 0.000 mg/L
- Threshold: 0.01 mg/L
- Since 0.000 is not greater than 0.01, lead is not found in toxic quantities.
5. Nitrate in Well B: 0.00 mg/L
- Threshold: 10 mg/L
- Since 0.00 is not greater than 10, nitrate is not found in toxic quantities.
Based on this evaluation, the contaminants found in toxic quantities for each well are:
- Well A:
- Arsenic
- Cadmium
- Cyanide
- Nitrate
- Well B:
- Arsenic
- Barium
