Atrazine was a widely-used agricultural herbicide that can be commonly detected in rivers and streams. Drinking water with high concentrations of atrazine can lead to cardiovacular and reproductive problems. A water test found a concentration of 1.5 ppbm of atrazine. (a) (10 pts) Convert the concentration to mg/L. Does the measured concentration exceed the EPA regulated limit of 0.003 mg/L for atrazine in drinking water? (b) (10 pts) If an average person drinks 2 L of water per day, determine the mass of atrazine (in mg) that they would consume per day with 1.5 ppbm of atrazine in the water. (c) (10 pts) Look up the chemical formula of atrazine and calculate the molecular weight of atrazine from the formula. Convert the 1.5 ppbm concentration to µmol/L.

Answer: a) 0.0015 mg/L < 0.003 mg/L; so, no, it's not up to the EPA limit.

b) An average person takes in 0.003 mg atrazine per day

c) Concentration of atrazine in μmol/L = 0.00695 μmol/L

Explanation:

a) ppb = μg/L

1000 μg/L = 1 mg/L

1.5 ppb = 1.5 μg/L = (1.5/1000) mg/L = 0.0015 mg/L

0.0015 mg/L < 0.003 mg/L

The measured concentration isn't up to EPA regulated limit.

b) An average person takes in 2L of water daily,

2L of water contains (2 * 0.0015) mg of atrazine = 0.003mg.

An average person takes in 0.003 mg atrazine per day.

c) Chemical formula for atrazine is C8H14ClN5, molecular weight = 215.68 g/mol

Concentration in μmol/L = (concentration in μg/L) / (Molecular Weight)

concentration in μg/L = 1.5 μg/L

Molecular weight = 215.68 g/mol

Concentration in μmol/L = 1.5/215.68 = 0.00695 μmol/L

QED!