Practise IB ESS SL 4.4 by tracing pollutants through water systems, interpreting direct measurements and evaluating controls at source, pathway and ecosystem level.
A small lake is going through the process of eutrophication. State one possible point source and one possible non-point source of nutrient pollution in the lake.
Point source:
Non-point source:
Define the term biochemical oxygen demand (BOD).
Figure:pH-tolerance ranges of freshwater organisms
The pH-tolerance chart shows the ranges over which aquatic organisms in a small lake can survive.
Use the pH-tolerance ranges of freshwater organisms: the pH tolerance ranges of trout, bass, perch, frogs, salamanders, clams, crayfish, snails and mayfly in the small lake.
State which organism(s) would still be present if the pH of the lake was reduced to 5.0.
Use the pH-tolerance ranges of freshwater organisms: the pH tolerance ranges of trout, bass, perch, frogs, salamanders, clams, crayfish, snails and mayfly in the small lake.
Explain why the populations of remaining organisms in the lake may decline in the long term.
Many countries produce large amounts of solid domestic waste. Pacific Ocean currents concentrate and trap solid domestic waste from the Pacific Rim countries and have created the Great Pacific Garbage Patch (GPGP) in the North Pacific Gyre (Figure 5).
Figure 6:Consumption and disposal of plastic waste for India and selected Pacific Rim countries
* Estimated for 2017 based on 10% growth.
Identify one reason why most plastics may be considered more serious pollutants than other forms of solid domestic waste.
Explain why the data in Figure 6 show no correlation between plastic consumption and plastic waste deposited in ocean for the countries listed.
Figure:Coliform bacteria one day after untreated sewage release
Using Figure 11(b), estimate the highest concentrations of coliform bacteria (in units/100 mL) found in the St Lawrence River one day after the untreated sewage was released.
Outline an environmental problem that may result from the release of untreated sewage into a river.
Figure:Coliform bacteria before untreated sewage release
Montreal:
In November 2015, the City of Montreal discharged between 5 and 8 billion litres of untreated sewage into the St Lawrence River.
• It was called “FlushGate” in the Canadian news.
• Citizens were warned to avoid contact with the water.
• River pollution levels returned to normal within 4 to 10 days.
• The Mayor of Montreal described it as the “most environmentally-friendly solution”.
Quebec:
In November 2016, the City of Quebec discharged 110 million litres of untreated sewage into the St Lawrence River.
Nationally:
• 25 % of Canadians do not have access to sewage or wastewater treatment centres.
• 205 billion litres of untreated sewage are released into Canadian rivers and oceans each year.
With reference to Figures 10, 11(a) and 11(b), describe a method to monitor the impact of the release of untreated sewage into the St Lawrence River ecosystem.