Understanding water quality
Understanding water quality

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

Understanding water quality

2.4 Organic and inorganic chemicals

Organic and inorganic chemicals can become pollutants when they are washed into rivers, lakes or the sea. Some of the chemicals are toxic, depending on their concentrations. Toxic organic substances include agricultural pesticides such as dichlorodiphenyltrichloroethane (DDT) and dimethyl mercury and also polychlorinated biphenyls (PCBs), which are byproducts of the plastics industry. DDT and PCBs are particularly dangerous as they are very stable and not biodegradable, so they can accumulate in water and in living organisms. Because of this, the use of DDT is now banned in most industrialised countries, although it is still used in some developing ones as it is a cheap and effective pesticide. Toxic inorganic substances include salts of the metals copper, silver, lead, gold, nickel, chromium, zinc, cadmium and mercury, and the metalloid arsenic. Many of these are toxic even at low concentrations: less than 1mg l-1. Most are wastes from industrial processes or mining (Figure 9).

Figure 9 Acid mine drainage in the Carnon River, Cornwall from the Wheal Jane mine, an example of inorganic chemical pollution caused by oxidation of sulphide minerals. The water and sediment is coloured orange by compounds of iron and other metals.
S278_15

Take your learning further371

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 courses372.

If you are new to university level study, we offer two introductory routes to our qualifications. Find out Where to take your learning next?373 You could either choose to start with an Access courses374or an open box module, which allows you to count your previous learning towards an Open University qualification.

Not ready for University study then browse over 1000 free courses on OpenLearn375 and sign up to our newsletter376 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