Solubilisation of six polycyclic aromatic hydrocarbons (PAHs) (acenaphthene, anthracene, fluoranthene, fluorene, phenanthrene and pyrene) by three synthetic cyclodextrins (CDs) (2-hydroxypropyl-β-CD, hydroxypropyl-γ-CD and ramdomly methylated-β-CD) was investigated in order to select the CD which presents the greatest increase in solubility and better complexation parameters for its use in contaminated scenarios. The presence of the three cyclodextrins greatly enhanced the apparent water solubility of all the PAHs through the formation of inclusion complexes of 1∶1 stoichiometry. Anthracene, fluoranthene, fluorene and phenanthrene clearly presented a higher solubility when β-CD derivatives were used, and especially the complexes with the ramdomly methylated-β-CD were favoured. On the contrary, pyrene presented its best solubility results when using 2-hydroxypropyl-γ-CD, but for acenaphthene the use of any of the three CDs gave the same results. Complementary to experimental phase-solubility studies, a more in-depth estimation of the inclusion process for the different complexes was carried out using molecular modelling in order to find a correlation between the degree of solubilisation and the fit of PAH molecules within the cavity of the different CDs and to know the predominant driving forces of the complexation.

43The phenylurea herbicide diuron [N-(3,4-dichlorophenyl)-N,N-dimethylurea] is widely 44 used in a broad range of herbicide formulations, and consequently, it is frequently 45 detected as a major soil and water contaminant in areas where there is extensive use. 46Diuron has the unfortunate combination of being strongly adsorbed by soil organic 47 matter particles, and hence, slowly degraded in the environment due to its reduced 48 bioavailability. N-phenylurea herbicides seem to be biodegraded in soil, but it must be 49 kept in mind that this biotic or abiotic degradation could lead to accumulation of very 50 toxic derived compounds, such as 3,4-dichloroaniline. 51A research was conducted to find procedures that might result in an increase in the 52 bioavailability of diuron in contaminated soils, through solubility enhancement. For our 53 purpose we used a double system composed of hydroxypropyl-β-cyclodextrin (HPCD), 54 which is capable of forming inclusion compounds in solution, and a two-members 55 bacterial consortium formed by the diuron-degrading Arthrobacter sulfonivorans 56 (Arthrobacter sp. N2) and the linuron-degrading Variovorax soli (Variovorax sp. 57 SRS16), which will be able to achieve a complete biodegradation of diuron to CO 2 . The 58 cyclodextrin-based bioremediation technology here described shows for the first time an 59 almost complete mineralisation of diuron in a soil system, as opposite to previous 60 incomplete mineralization based on single or consortium bacterial degradation. 61 62

16 17The objective of the present study was to characterize the polycyclic aromatic 18 hydrocarbons (PAHs) content of an aged contaminated soil and to propose remediation 19 techniques using cyclodextrins (CD). Four CDs solutions were tested as soil 20 decontamination tool and proved more efficient in extracting PAHs than when an 21 aqueous solution was used; especially two chemically modified CDs resulted in higher 22 extraction percentages than natural β-CD. The highest extraction percentages were 23 obtained for 3-ring PAHs, because of the appropriate size and shape of these 24 compounds relative to those of the hydrophobic cavities of the CDs studied.

14Sorption-desorption experiments of fluorene (FLU) and fluoranthene (FLT) in soils 15were carried out and correlated to their removal from aged contaminated soils using 16 aqueous solutions in the absence and in the presence of hydroxypropyl-β-cyclodextrin 17 (HPBCD) as the extraction agent. FLU became more resistant to extraction in aged 18 contaminated soils due to its initial adsorption onto the mineral and amorphous soil 19 organic matter (SOM) domains, sites of lower binding energy from which, due to its 20 small size, it could spread towards the condensed SOM as the contact time increased. 21Therefore, FLU will not be easily desorbed from aged contaminated soils due to 22 physical entrapment mechanisms, even when using HPBCD as extractant, presenting 23 FLU low risks to the environment. On the contrary, FLT was extracted from aged soils 24 in the presence of HPBCD in solutions to a much greater extent than in its absence. Due 25 to its more hydrophobic character FLT sorption in soils was relatively quicker, 26 remaining more or less fixed on hydrophobic sites of the organic matter (OM) with 27 different energies, and therefore the amount of FLT extracted was almost constant for 28 different ageing times. During extraction experiments, the influence of the OM quality 29 of the soils was also highlighted because an inverse proportionality between OM 30 content of soil and extractability of sorbed FLT was observed. It was concluded that 31Preprint submitted to Elsevier 2 soils with lower OM content that had more diagenetically processed OM could block 1 the extraction of FLT more effectively than soils with higher OM content that are less 2 humified. This indicates the need to not only use adsorption-desorption data in 3 contaminant fate and transport models, but also extraction studies in aged contaminated 4 soils and other complementary analytical approaches when assessing soil 5 contamination-related risks. 6 7 8

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