Didactic experience for the analysis of phosphates in waters

Abstract

Phosphate, as nitrates, is an essential nutrient for primary production, although it is often less abundant and more limiting. However, like any parameter, if it exceeds certain concentrations, it becomes an environmental risk by causing eutrophication (excess of nutrients, mainly nitrogen and phosphorus). Phosphates present in water may have a natural origin, due to washing of the basin (mainly by the weathering of the rocks with phosphorus and by a subsequent dissolution in the water of rain), or an anthropogenic origin, caused by human contamination. The final objective of this experience will be that students learn to quantify phosphates present in water. It includes the following learning items:

Phosphates

• Introduction

Principle of operation of the visible spectrophotometer ONDA V-10 plus

• Preparation of the potassium hydrogenophosphate solution (KH2PO4)
• Preparation of solutions for the calibration curves
• Determination of maximum wavelength absorbance
• Additional analysis of water quality: pH and turbidity
• Analysis of ortophosphates by colorimetry

This science education experience involves seven sessions and a total of eight hours. The content of the sessions is described in this article. The final objective is for students’ work to be shown in a blog that they themselves will elaborate while working on the experience mentioned above. The blog will include the same items mentioned above. This science education experience has been carried out with three students of 4th of ESO (secondary compulsory education) in the subject of “social sciences’ research project”.