title: Evaluation of the surface affinity of water in three biochars using fast field cycling NMR relaxometry.
abstract: Many soil functions depend on the interaction of water with soil. The affinity of water for soils can be altered by applying soil amendments like stone meal, manure, or biochar (a carbonaceous material obtained by pyrolysis of biomasses). In fact, the addition of hydrophobic biochar to soil may increase soil repellency, reduce water-adsorbing capacity, inhibit microbial activity, alter soil filter, buffer, storage, and transformation functions. For this reason, it is of paramount importance to monitor water affinity for biochar surface (also referred to as 'wettability') in order to better address its applications in soil systems. In this study, we propose the use of fast field cycling NMR relaxometry technique with the application of a new mathematical model for data interpretation, as a valid alternative to the traditional contact angle (CA) measurements for biochar wettability evaluation. Either NMR or CA results revealed the same wettability trend for the biochars studied here. The advantage of NMR relaxometry over CA measurements lies in the possibility to obtain at the microscopic level a variety of different information in only one shot. In fact, while CA provides only wettability evaluation, NMR relaxometry also allows achievement of the mechanisms for water molecular dynamics on biochar surface, thereby leading to the possibility to understand better, in future research, the role of biochar in increasing soil quality and plant nutrition.
authors.affiliation: Stelar srl, 27035, Mede, PV, Italy.|JEOL (ITALIA) S.p.A., Palazzo Pacinotti-Milano 3 City, Via Ludovico il Moro 6/A, 20080, Basiglio, MI, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Bubici
authors.affiliation: Physique de la Matière Condensée, Ecole Polytechnique-CNRS, 91128, Palaiseau, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Korb
authors.affiliation: Institute for Environmental Sciences, Department of Soil and Environmental Chemistry, University of Koblenz-Landau, Landau, 76829, Germany.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kučerik
authors.affiliation: Dipartimento di Scienze Agrarie e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy.
authors.forename: Pellegrino
authors.initials: P
authors.lastname: Conte
mesh_terms: D002606:Charcoal / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: C540010:biochar; D014867:Water; D002606:Charcoal
keywords: 1H; NMR; biochar; fast field cycling; relaxometry; water affinity; wettability