The Water-Colour Exhibition

A simple, laser-based reflectometer is described for the measurement of water turbidity via 180° optical scattering. Applications exist both in clean source waters (0-1000NTU) with a minimum detectable turbidity better than 1NTU, and in dense wastewater primary-clarifier sludges. The non-contact measurement is performed from a distance at least up to 10m, substantially avoiding the usual window fouling problems of optical instruments. By measuring directly in the process, through a free water surface or on the side of a flowing water stream, the difficulties of transporting sample to the instrument are also avoided. Extensions to be described allow measurement also of water colour.

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Citizen Science Tools Reveal Changes in Estuarine Water Quality Following Demolition of Buildings

Remote Sensing ◽

10.3390/rs13091683 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1683

Author(s):

Nandini Menon ◽

Grinson George ◽

Rajamohananpillai Ranith ◽

Velakandy Sajin ◽

Shreya Murali ◽

...

Keyword(s):

Water Quality ◽

Dissolved Oxygen ◽

Citizen Science ◽

Secchi Depth ◽

Lake Water Quality ◽

Demolition Waste ◽

Water Colour ◽

Water Quality Variables ◽

The Impact

Turbidity and water colour are two easily measurable properties used to monitor pollution. Here, we highlight the utility of a low-cost device—3D printed, hand-held Mini Secchi disk (3DMSD) with Forel-Ule (FU) colour scale sticker on its outer casing—in combination with a mobile phone application (‘TurbAqua’) that was provided to laymen for assessing the water quality of a shallow lake region after demolition of four high-rise buildings on the shores of the lake. The demolition of the buildings in January 2020 on the banks of a tropical estuary—Vembanad Lake (a Ramsar site) in southern India—for violation of Indian Coastal Regulation Zone norms created public uproar, owing to the consequences of subsequent air and water pollution. Measurements of Secchi depth and water colour using the 3DMSD along with measurements of other important water quality variables such as temperature, salinity, pH, and dissolved oxygen (DO) using portable instruments were taken for a duration of five weeks after the demolition to assess the changes in water quality. Paired t-test analyses of variations in water quality variables between the second week of demolition and consecutive weeks up to the fifth week showed that there were significant increases in pH, dissolved oxygen, and Secchi depth over time, i.e., the impact of demolition waste on the Vembanad Lake water quality was found to be relatively short-lived, with water clarity, colour, and DO returning to levels typical of that period of year within 4–5 weeks. With increasing duration after demolition, there was a general decrease in the FU colour index to 17 at most stations, but it did not drop to 15 or below, i.e., towards green or blue colour indicating clearer waters, during the sampling period. There was no significant change in salinity from the second week to the fifth week after demolition, suggesting little influence of other factors (e.g., precipitation or changes in tidal currents) on the inferred impact of demolition waste. Comparison with pre-demolition conditions in the previous year (2019) showed that the relative changes in DO, Secchi depth, and pH were very high in 2020, clearly depicting the impact of demolition waste on the water quality of the lake. Match-ups of the turbidity of the water column immediately before and after the demolition using Sentinel 2 data were in good agreement with the in situ data collected. Our study highlights the power of citizen science tools in monitoring lakes and managing water resources and articulates how these activities provide support to Sustainable Development Goal (SDG) targets on Health (Goal 3), Water quality (Goal 6), and Life under the water (Goal 14).

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When art meets taxonomy: identity of Erythrina laeta (Fabaceae)

Phytotaxa ◽

10.11646/phytotaxa.255.2.3 ◽

2016 ◽

Vol 255 (2) ◽

pp. 144 ◽

Cited By ~ 2

Author(s):

EMANUELE DEL GUACCHIO ◽

PAOLA CENNAMO ◽

MARIO VÁZQUEZ TORRES ◽

BRUNO MENALE

Keyword(s):

Botanical Garden ◽

Water Colour

The unresolved name Erythrina laeta Dehnh. is neotypified by a water-colour kept in the Botanical Garden of Naples (Italy). The Dehnhardt’s name resulted to be a heterotypic synonym of E. americana. The nomenclatural types of the names and their synonyms are discussed, and the names E. enneandra DC. and E. fulgens Loisel. are lectotypified by two pictures.

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Landsat Views of Sudbury (Canada) Area Acidic and Nonacidic Lakes

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-298 ◽

1992 ◽

Vol 49 (S1) ◽

pp. 33-39 ◽

Cited By ~ 3

Author(s):

J. Roger Pitblado

Keyword(s):

Thematic Mapper ◽

Landsat Data ◽

Multivariate Statistical ◽

Temporal Dimension ◽

Acidic Lake ◽

Water Colour ◽

Statistical Procedures ◽

Changes Over Time ◽

Radiance Data ◽

Over Time

Multivariate statistical procedures are used to establish empirical associations between acidity, visual lake water colour, dissolved organic carbon (DOC) concentrations, and Landsat-5 Thematic Mapper (TM) radiance data. Acidic lakes in an area northeast of Sudbury (Canada) are characterized by their clear, blue colours and very low DOC. With a subjective, three-class water colour grouping, 92% of the study lakes were correctly classified using TM data. Further, it is shown that DOC, the major component of water colour in this area, can be predicted within 1 mg/L of observed concentrations using TM data (multiple r = 0.93, P < 0.01). By deriving interrelationships between pH levels, water colour, and DOC, Landsat data provide a means to discriminate and map the acidic and nonacidic lakes of the study area. Examination of the reflectance characteristics of a single acidic lake (Bowland Lake) that has undergone neutralization suggests that Landsat data may be used to detect optical changes over time. However, the capability for monitoring the temporal dimension of lake acidification using satellite data has yet to be established.

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