Sulfamethoxazole is a widely used antibiotic that often contaminates aquatic environments. Scientists investigated the rate at which sulfamethoxazole is broken down by populations of sediment-dwelling microorganisms at two different pH treatments: pH 5.5 and pH 7.5.
They measured the concentration of sulfamethoxazole in sediment samples over 8 days. Each sample started with the same initial concentration of sulfamethoxazole and had the exact same dry mass of sediment. Their results are shown in the graph below:
Suggest why, in this investigation, the scientists expressed the concentration of sulfamethoxazole in units of μg kg−1\mu\text{g }\text{kg}^{-1}μg kg−1.
Calculate the difference in the rate of breakdown of sulfamethoxazole per day between day 0 and day 4 at pH 5.5 and pH 7.5. Show your working and state the units for your answer.
