An open-source dual-beam spectrophotometer for citizen-science-based water quality monitoring

Efforts to understand and mediate threats to water supplies rely on collection of reliable data at large scale, a goal which is often limited by availability of tools that are both affordable and reliable. We present here a low-cost, easy-to-use, do-it-yourself (DIY) spectrometer for measurement of a variety of relevant solute concentrations when coupled with inexpensive commercially-available reagents. Comparison of its performance with commercial options demonstrates the potential value of this device as transparent, versatile, and accurate-enough alternative for widespread application.