Abstract
Developments in digital image acquisition technologies and citizen science lead to more water color observations and broader public participation in environmental monitoring. However, the implications of the use of these simple water color indices for water quality assessment have not yet been fully evaluated. In this paper, we build a low-cost digital camera colorimetry setup to investigate quantitative relationships between water color indices and concentrations of optically active constituents (OACs). As proxies for colored dissolved organic matter (CDOM) and phytoplankton, humic acid and algae pigments were used to investigate the relationship between water chromaticity and concentration. We found that the concentration fits an ascending relationship with xy chromaticity values and a descending relationship with hue angle. Our investigations permitted us to increase the information content of simple water color observations, by relating them to chemical constituent concentrations in observed waters.
Highlights
Water quality is related to the ecological environment, water cycle dynamics as well as human impacts on water resources
Since the future application of this technique might be adopted under different illumination conditions with different cameras, the device-dependent RGB values could be hardly used for quantitative optically active constituents (OACs) in water
This paper showed a design of a low-cost digital camera colorimetry setup and a method to correct the bias caused by different light illumination conditions and camera settings
Summary
Water quality is related to the ecological environment, water cycle dynamics as well as human impacts on water resources. The use of water color as a surrogate or proxy for water quality is rapidly increasing due to the rapid expansion of smartphone applications as citizen tools for observing and monitoring aquatic environments [1,2,3]. Water color is an important and distinct indicator of water quality. The different colors of natural water bodies have been described for centuries, with records tracing back to writings of the 16th century and paintings of the 18th century [4]. 19th century, a color comparator scale called Forel-Ule was adopted by oceanographers to record water color data [5]. It was later converted to a modern tool and connected with chromaticity values (x, y) and dominant wavelengths in 2014 by Novoa et al [6]
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