A farmer applies 1605 kg of a fertilizer that contains 10.0% nitrogen to his fields each year. Fifteen percent (15.0%) of the fertilizer washes into a river that runs through the farm.

Question

If the river flows at an average rate of 0.470 cubic feet per second, what is the additional concentration of nitrogen (expressed in milligrams of nitrogen per liter) in the river water due to the farmer's fertilizer each year?

Answer 1

Hello, Alyssa,

This is a long series of conversions. Calculate secs/year and change the Fertilizer and River flow to per second values. I can't add my table due to space limitations. Carefully look at the units and they will guide you through the steps.

My table can be found here: https://docs.google.com/spreadsheets/d/1UW0YDAzYaHupkLPwxf-WmFAumHv7Mk2_MsrENTEI_fE/edit?usp=sharing.

Convert both kg to mg and ft^3 to liters. Calculate seconds/year and convert the Fertilizer into mg N/sec that reaches the river after accounting for both the 10% and 15% values.

Once everything is in liters/sec and mg/sec, just divide the two to get mg N/liter.

I hope this helps. Bob