Evaluation of phytotoxic effects of cationic polyacrylamide polymers: implication for the use of sludges as organic soil amendments in assisted phytostabilization.

Sludges, as biosolids, are organic soil amendments commonly used in assisted phytostabilitation. Extensive studies on their environmental impacts exists, particularly for improper land application and contents of trace elements, organic compounds and pathogens, but not for their content of cationic polyacrylamide polymers (C-PAMs). Direct toxicity of C-PAMs on aquatic organisms has been demonstrated but scarce information about plant toxicity is available. In this study, the effect of C-PAMs on early plant growth was evaluated by means of standard toxicity assays. Firstly, increasing doses of C-PAMs were applied as solutions to seeds of and to evaluate germination and root elongation. Secondly, the effect of increasing doses of C-PAMs spiked in pig manure and mixed with sand (75 t hadry base) was evaluated on the emergence, radicle elongation and biomass of . Results showed high phytotoxicity of C-PAMs in solutions above 1,000 mg L, but no effect was detected when spiked into experimental substrate; a significant effect was only observed above 5,000 mg L for radicle elongation, aerial biomass, and radicle biomass. Results demonstrate direct phytotoxic effects of C-PAMs, which can be mitigated when spiked into an organic (pig manure) and mineral (sand) matrix.