###### Abstract  
The remediation of dredged sediments (DS) as a major waste generation field has become an urgent environmental issue. In response to the limited strategies to restore DS, the current study aimed to investigate the suitability of _Paulownia tomentosa_ (Thunb.) Steud as a tool for decontamination of DS, both independently and in combination with a sewage sludge-based biochar. The experimental design included unannended and biochar-supplemented DS with the application rates of 2.5, 5.0, and 10.0%, in which vegetation of _P. tomentosa_ was monitored. The results confirmed that the incorporation of biochar enriched DS with the essential plant nutrients (P, Ca, and S), stimulated biomass yield and improved the plant's photosynthetic performance by up to 3.36 and 80.0 times, respectively; the observed effects were correlated with the application rates. In addition, biochar enhanced the phytostabilisation of organic contaminants and shifted the primary accumulation of potentially toxic elements from the aboveground biomass to the roots. In spite of the inspiring results, further research has to concentrate on the investigation of the mechanisms of improvement the plant's development depending on biochar's properties and application rate and studying the biochar's mitigation effects in the explored DS research system. complex contamination; waste valorisation; _Paulownia tomentosa_; biochar dose; circular economy  
14 September  
agriculture looks very promising, prior to application, DS have to be significantly cleaned from contaminants of both organic and inorganic origin. Indeed, given the substantial volume of sediments designated for dredging and recycling, estimated in the Czech Republic as 200 M m\({}^{3}\)[19], the further valorisation of DS demands the development of sustainable approaches aimed at their remediation. The biological cleaning of DS remains underexplored due to their heterogeneous composition and limited oxygen availability [20]. Numerous studies have demonstrated the viability of phytoremediation for the revitalisation of sediments both ex situ and in situ [21; 22; 23; 24; 25; 26; 27; 28; 29; 30]. The selection of plants should be based on the phytoremediation potential in relation to the target contaminants and ecological adaptability [31]. _Paulownia tomentosa_ (Thunb.) Steady (_P. tomentosa_) is among the viable candidates due to the plant's tolerance to xenobiotics, essential yield achieved even under the non-optimised growth conditions, and ability to accumulate trace elements (TEs) and organochlorine pesticides [32; 33]. The application of the widely utilised phytoagent _Miscanthus_\(\times\)_siganteus_[34] in DS that is complexly contaminated by pesticides and TEs, may be unsuccessful due to earlier reported essential stress plant experiences in heavily pesticide-contaminated soil [35]. The substitution of _Miscanthus_\(\times\)_siganteus_ for _Miscanthus sinensis_, proposed for Kazakhstan [35; 36], cannot be implemented in some European countries, including the Czech Republic, where _Miscanthus sinensis_ is classified as an invasive crop [37; 38]. Despite the approved attractiveness of _Paulownia_ sp. biomass for valorisation in biorefineries [39], the investigations covering the scientific framework for utilisation are limited: from 1971 to 2021, only 820 scientific documents were published on the related topics [40]. The studies dedicated to the exploration of _P. tomentosa_ as a phytoagent are almost absent, and the existing ones focus on the phytoremediation of TE-contaminated soils [41; 42; 43; 44; 45]. Our previous research on the behaviour of _P. tomentosa_ in soils complexly contaminated with organochlorine pesticides and TEs was pioneering [33] in terms of the utilisation of this plant for the phytoremediation of complexly contaminated soil. The current study aimed to continue investigation on the potential of _P. tomentosa_ to develop within the same contamination nature but in a different substrate.