Divide pupils into smaller groups and let them guess what a wetland is (A wetland is an area, where the ground is saturated with water, and it is at least for a part of the year covered with water – swamp, marsh, pools, floodplains, etc.).
Every group gets a glass with water and food pigment, to which the pupils add water and stir well. They put celery sticks in the water and observe. After a while, you show them a glass with celery sticks that you prepared on a former day for comparison.
Explain that the pigment represents pollution with organic substances, that are also nutrients for plants. Celery absorbs the pigment in water in the same way as plants in nature absorb pollutants from water. The pigment can also represent inorganic substances, poisonous substances (e.g. heavy metals) that some plants absorb despite their toxicity and, in this way, they purify water and sediments.
Does a plant absorb all the pigment? (No, only as much as it needs for life processes).
How do we use these characteristics of wetland in practice? (We have constructed wetlands, a kind of wastewater treatment plant that absorbs pollutants dissolved in water).
How is it possible to increase the self-purification ability of watercourses? (By preserving natural river banks covered by woody vegetation, and by preserving floodplains and wetlands, that have considerable cleaning ability; protect plants and animals living in wetlands and floodplains).
Materials and Worksheets
food pigment (it represents different substances in wastewater, organic substances, nutrients, other pollutants)