Effects of pollutants on the aquatic environment
Effects of pollutants on the aquatic environment

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Effects of pollutants on the aquatic environment

6.2 Immiscible liquids

Immiscible liquids may be present as oils, greases or tarry substances, often in the form of an emulsion (a colloidal suspension of one liquid in another, as in mayonnaise). They may affect turbidity in the same way as suspended solids. However, emulsions are not likely to settle to the bed of the river. Frequently they float on the surface and adhere to vegetation at the waterline. Some immiscible liquids are decomposed slowly by aquatic microorganisms. Many oils and tars are slightly soluble in water and thereby impart tastes and odours to it.

Oil is generally less dense than water and will spread over the surface to form an extremely thin, often visible film; a small quantity of oil is therefore likely to pollute a large area. Even when the oxygen demand in the water is low and oil imposes little additional biological load, the presence of an oil film with a thickness of only one thousandth of a millimetre (1 µm) may reduce the rate at which oxygen is transferred from air to water. It can also affect the life cycle of insects, since the larvae of some species float on the surface.

Oil is one of the more serious pollution problems. As an example, there are now around 3000 pollution incidents involving oil and fuels every year in England and Wales (Environment Agency, 2013). Although some of these affect land, the vast majority affect the water environment.

T868_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371