Copper bioaccumulation capacity of the floating fern Salvinia minima

LAURA DE CABO; MARÍA VICTORIA CASARES; RAFAEL SEOANE; SILVANA ARREGHINI

Barcelona, España

Simposio; 3rd Wetland Pollutant Dynamics and Control Symposium; 2009

The present contribution assessescopper and nutrient removal efficiency of Salvinia minima, like a promising alternative to effluentstreatment in Pilcomayo and Matanza-Riachuelo basins.The water purification capacity of S.minima at different Cu concentrations was determined.Monoculture plants were selected and acclimated to greenhouse conditions for at least a week. Astatic 96 hours experiment was conducted. Plastic containers with 1litre of simplified 1/10 Hutner’smedium and 400 fronds have been used. pH medium was adjusted to 6.5-7.5 and photoperiod was12:12 light/dark. pH, temperature and conductivity were measured at the beginning and at the endof the experiment. Copper was added to each container as CuCl2. The studied concentrations bytriplicate were 0, 6, 8, 10, 20, 40, 50 y 100 ppm. At the end of the experiment, water samples weretaken and fronds counted. Fronds (aerial) were separated from rhizome and pseudo roots (RPR)(submersed) and dry weight and chlorophyll a and b were determined. In water samples NH4+, NO3-DIN (Dissolved Inorganic Nitrogen), SRP (Soluble Reactive Phosphorous), sulphates andmagnesium were estimated (APHA, 1992). Copper in water samples and plants was determinedafter acid digestion (HNO3:HClO4:HCl) by atomic absorption spectrophotometry (Perkin Elmer1100B). The average relative growth rate (RGR) was calculated using Hunt’s equation and initialand final frond number.DIN and SRP decreased in all treatments. At the end of the experiment concentrations were lessthan quarter parts of the initial ones. T40, T50 and T100 showed reduced decrease of sulphates andan increase in magnesium concentration which can be attributed to plants decomposition. In fact,magnesium is one of the nutrients more rapidly released (Sharma & Goel, 1986). (Table 1)Frond Number decreased with copper concentration from T6 to T8 remaining low in the rest ofthe treatments and chlorophyll showed the same trend from T6 to T10 (Table 2). The percentage ofCu removed was 95,05 %, 89,7 %, 94,3 %, 73 % and 61 % of the total copper added in T6, T8, T10,T50 and T100, respectively, and the accumulation of copper occurred especially in RPR (Table 3).RGR decreased with Cu concentration (Table 2).S. minima is a promising alternative to reduce high copper and nutrients concentrations ineffluent’s treatment in artificial wetlands. The results obtained here show that plants should beharvested to avoid the possibility of copper being released during decomposition.