The interception effect of a multi-filtration system of moss tufa on heavy metal levels in the stream.

Moss tufa, a significant filtration system in karst environments, plays a crucial role in intercepting heavy metals in water and ensuring aquatic ecological security. However, studies on the superimposed effect of multi-filtration moss tufa systems on intercepting heavy metals in water are scarce. Thus, this study focused on three adjacent moss tufa filtration systems (upstream, midstream, and downstream) as research subjects. Ecological importance value, niche width, interception rate, and enrichment coefficient were utilized to analyze the interception effect of these systems on heavy metals in water. The findings revealed that multiple moss tufa systems exerted a superimposed effect on heavy metal interception. Moreover, within the three moss tufa filtration systems, mosses from 9 families, 11 genera, and 13 species were detected. Among them, Hydrogonium arcuate (Griff.) Chen was the dominant species with the widest niche width. The interception rates of the moss tufa filtration system for Cd, Fe, Cr, and Zn were 95.7 %, 88.3 %, 77.4 %, and 74.3 %, respectively, whereas those for V, Mn, Ni, Cu, and Pb ranged between 50 % and 65 %. Importantly, in the moss tufa filtration systems consisting of the upstream, midstream, and downstream, the tufa and moss respectively accumulated 3 and 2-3 times as much concentration as the single upstream. In conclusion, these study findings highlight that the moss tufa filtration system can purify the majority of heavy metals and that multi-filtration system of moss tufa exerts a superimposed effect intercepting heavy metals.