20.3. Pollution
A subsection of Biology, 0610, through 20. Human influences on ecosystems
Listing 10 of 168 questions
Some pollutants are not broken down easily and remain in the environment for a long time. These are described as persistent pollutants. PCBs are a waste material from the manufacturing of electrical insulation. PCBs are one of the most persistent pollutants in the environment. Between 1947 and 1976, factories dumped large quantities of PCBs into the Hudson River in the USA. Studies measured the concentrations of PCBs in the tissues of organisms in a food chain in the sea near the Hudson River, as shown in . 11 400 – 17 300 concentrations of PCBs in arbitrary units 6 – 45 1.56 0.85 porpoise herring zooplankton phytoplankton not to scale Describe the results shown in . Suggest an explanation for the different concentrations of PCBs in the organisms of the food chain. PCBs are toxic to many organisms because they bind to a protein molecule known as AHR. The Atlantic tomcod, Microgadus tomcod, is a fish that lives in the Hudson River and other rivers nearby. 90% of the tomcod population in the Hudson River is resistant to the effects of PCBs. This is because these fish have a different type of AHR compared with other tomcod populations. Suggest how this resistance came about. Scientists predict that the proportion of fish resistant to PCBs will decrease if the concentration of PCBs in the river decreases. Suggest reasons why the proportion of fish with the altered AHR protein might decrease. Describe the problems caused by non-biodegradable plastics in the environment.
0610_w14_qp_32
THEORY
2014
Paper 3, Variant 2
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Some students studied water pollution in a stream near their school. They took samples of water at six sampling points along the stream and carried out a chemical analysis on the water samples. They also counted the numbers of five different invertebrates at the same sampling points. The students used a four point scale to record the numbers they found in each sample. Their results are shown in Table 6.1. Table 6.1 sampling points chemical analysis types of invertebrates nitrate concentration oxygen concentration rat-tailed maggot mayfly nymph stonefly nymph tubifex worm water louse low high + +++ + + + high very low ++ – – +++ ++ high very low ++ – – +++ ++ very high very low ++ + – +++ ++ very high low + ++ – ++ ++ low high + +++ + + + key – none + 1 to 10 ++ 11 to 100 +++ too many to count Using only the information from Table 6.1, state the invertebrates that survive in polluted water state the invertebrate that is most sensitive to a decrease in the oxygen concentration of the water. The students noticed there were many algae and aquatic plants growing in the stream at sampling points 4 and 5. Use the results in Table 6.1 to explain why there are many algae and aquatic plants growing in these parts of the stream. The students decided there were advantages in sampling invertebrates to assess the level of pollution in the stream, compared with carrying out a chemical analysis of the water. Suggest the advantages of carrying out a survey of invertebrates when studying the pollution of freshwater ecosystems, such as streams and rivers. The students found that the stream was polluted by sewage from a nearby house. Outline how sewage should be treated before entering a stream. The stream contained many plastic items that had been thrown away. Most of the plastic was non-biodegradable. Describe the likely environmental problems caused by non-biodegradable plastics in streams and rivers.
0610_w15_qp_32
THEORY
2015
Paper 3, Variant 2
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Plastic bags cause many problems in the environment. Plastic bags were banned in Bangladesh in 2002. Outline the effects of non-biodegradable plastics on the environment. Some countries have not banned plastic bags. There have been many studies to analyse possible alternatives to plastic bags. Table 5.1 shows the results of a study comparing the environmental impact of producing plastic bags and paper bags. Table 5.1 environmental impact of production plastic bags paper bags waterborne chemical waste / g per bag 1.1 2.7 airborne chemical waste / g per bag 0.025 1.25 energy used / kJ per bag trees used per bag 0.0014 oil used / dm3 per bag 0.022 Compare the environmental impact of making plastic bags with the environmental impact of making paper bags. You should use data from Table 5.1 in your answer. Heavy metals and acids are the most common waterborne chemical wastes from the production of paper bags. Describe the effects of these waterborne chemical wastes on the environment. Table 5.2 shows the results from a study comparing recycling of plastic bags and paper bags. Table 5.2 plastic bags paper bags bags recycled / % 0.6 19.4 energy used to recycle / kJ per bag 14 444 Compare the energy used to make plastic bags with the energy used to recycle plastic bags. You should use data from Table 5.1 and Table 5.2 in your answer. Pollution by heavy metals and acid is one concern about the making of paper bags. There are additional concerns about the making and recycling of paper bags. Discuss these additional concerns.
0610_w15_qp_33
THEORY
2015
Paper 3, Variant 3
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Questions Discovered
168