Mosses remove heavy metals from water

Mar 20, 2013
Ultra concise summary of the following abstract:

Mosses remove heavy metals from the water. Why? Because they have a large number of sites available to bind with metals.


"This study quantifies the adsorption of heavy metals on 4 typical moss species used for environmental monitoring in the moss bag technique. The adsorption of Cu2+, Cd2+, Ni2+, Pb2+ and Zn2+ onto Hypnum sp., Sphagnum sp., Pseudoscleropodium purum andBrachytecium rutabulum has been investigated using a batch reactor in a wide range of pH (1.3–11.0) and metal concentrations in solution (1.6 μM–3.8 mM). A Linear Programming Model (LPM) was applied for the experimental data to derive equilibrium constants and the number of surface binding sites. The surface acid–base titration performed for 4 mosses at a pH range of 3–10 in 0.1 M NaNO3 demonstrated thatSphagnum sp. is the most efficient adsorbent as it has the maximal number of proton-binding sites on the surface (0.65 mmol g−1). The pKa computed for all the moss species suggested the presence of 5 major functional groups: phosphodiester, carboxyl, phosphoryl, amine and polyphenols. The results of pH-edge experiments demonstrated that B. rutabulum exhibits the highest percentage of metal adsorption and has the highest number of available sites for most of the metals studied. However, according to the results of the constant pH “Langmuirian” isotherm, Sphagnum sp. can be considered as the strongest adsorbent, although the relative difference from other mosses is within 20%. The LPM was found to satisfactorily fit the experimental data in the full range of the studied solution parameters. The results of this study demonstrate a rather similar pattern of five metal adsorptions on mosses, both as a function of pH and as a metal concentration, which is further corroborated by similar values of adsorption constants. Therefore, despite the species and geographic differences between the mosses, a universal adsorption edge and constant pH adsorption isotherm can be recommended for 4 studied mosses. The quantitative comparison of metal adsorption with other common natural organic and inorganic materials demonstrates that mosses are among the most efficient natural adsorbents of heavy metals."

Gonzales, A.G., Pokrovsky, O.S. "Metal adsorption on mosses: Toward a universal adsorption model". Journal of Colloid and Interface Science, 415 (2014), 169-178.

So this may be a huge reason why moss should be added to shrimp tanks because it removes, through adsorption, metals which may be toxic in high concentrations. That may explain why, after moving a number of CBS into a new tank with no moss, they started dying. I feel horrible.

This probably also explains why putting sphagnum moss in the filter will help soften the water, because it adsorbs the calcium and magnesium ions as well as the heavy metals. This may also explain why mosses tend to be very tolerant of heavy metals, because its external structure prevents absorption of the metals into the cells which can cause damage.
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Dennis Singh

May 5, 2013
Orange County, CA
Are any of these even aquatic? Spaghnum gotta be a nutrient hog so easy and multipliable but its terrarium moss.

Good find L. I bet the absorption is way different in the mosses we use though, don't you think?

Tom Barr

Staff member
Jan 23, 2005
Tannins generally detoxify most metals, hence the driftwood and clay, peat , kappa leaves etc, all showing benefits for shrimp.

The Ecology of Humic Substances in Freshwater is a deeper read....... but provides a good overview.

Plants cannot run from bad conditions, so they are quite good at tolerating a very wide range of chemicals, and they make chemicals to counteract .........those toxic ones, Na+ for example.

How do salt water plants deal with all the Na+?

The answer is pretty simple.

Other plants are good at taking them in and then it becomes a similar thing to the above answer internally inside the cell/tissue/organ.