Mobilization of some metals in water and animal tissue by NTA, EDTA and TPP

Abstract

Parallel experiments were conducted under stagnant and flowing conditions to determine whether sodium tripolyphosphate (TPP), the conventional detergent builder, or two potential replacements, nitrilotriacetic acid (NTA) and ethylene—diaminetetraacetic acid (EDTA) significantly influenced the mobilization of major cations (Ca, Mg, Na, K) and some heavy metals (Fe, Mn, Zn, Cu, Pb, Cr). Water sediments and tissue of chironomid adults ( Chironomus tentans Fabricius), crayfish ( Orconectes virilis Hagen) and rainbow trout ( Salmo gairdnerii Richardson) were examined. The results showed that the chelating agents applied in concentrations of 0.2–5.0 mg 1 −1 often increased the concentration of iron, manganese, lead and zinc in water above contaminated lake sediments. Other heavy metals were not affected significantly. EDTA was the most active mobilizing agent while NTA and TPP both had a less significant effect. The chelating agents generally had little effect on the rate of uptake of most metals by chironomids in aquaria. The role of chelating agents in flowing systems was even less pronounced. Zinc concentrations in water were significantly elevated by the treatment with 1 mg 1 −1 EDTA and manganese concentrations were significantly higher in trout from the pond treated with an intermediate level (1 mg 1 −1) of NTA. All other treatments yielded levels of major ions and heavy metals that were not significantly different from those in the control ponds.