TY - JOUR

T1 - The multilayer model of soil mineral–organic interfaces—a review

AU - Gao, Jiajia

AU - Mikutta, Robert

AU - Jansen, Boris

AU - Guggenberger, Georg

AU - Vogel, Cordula

AU - Kalbitz, Karsten

N1 - Funding Information: We thank the China Scholarship Council for financial support. This study was partially supported by the Deutsche Forschungsgemeinschaft DFG [ FOR1806 , “ The Forgotten Part of Carbon Cycling: Organic Matter Storage and Turnover in Subsoils ” ( SUBSOM ); “ Formation and properties of mineral–organic soil interfaces as revealed by X‐ray photoelectron spectroscopy ” ( MI 1377/13‐1 )] and the Fundamental Research Funds for the Central Universities ( No . SWU7130200010/036 ). We are grateful to Susanne K. Woche for providing the surface‐modified glass slides as well as Prof. Markus Kleber for reviewing the manuscript and discussion.

PY - 2020/2/6

Y1 - 2020/2/6

N2 - Association of organic matter (OM) with minerals is an important pathway in the formation of stable OM in soil. While the importance of mineral–organic associations (MOA) in regulating soil carbon cycling has been rigorously demonstrated by empirical evidence, knowledge about the molecular-scale arrangement of OM at mineral surfaces is still lacking. Such knowledge is urgently needed to disentangle the mechanisms of long-term storage of soil OM. Based on indirect observations regarding the formation, composition, and structure of MOA, a conceptual multilayer model was proposed by Kleber et al. in 2007 to foster debate and help elucidating the structure and reactivity of MOA. According to this model, the associated OM at mineral surfaces is discrete and self-organized into a multilayer structure. In this review, we aim to collect and evaluate existing studies that used this model to explain biogeochemical processes at mineral–organic interfaces, and based on this, assess the applicability of the model. The multilayer model has seen extensive adoption within soil science and related fields. In general, existing studies either support the concept of a patchy distribution of adsorbed OM on mineral surfaces or advocate that OM can be coprecipitated with nanosized poorly crystalline minerals or hydrolysable metals. However, the evidence for the patchy distribution of adsorbed OM cannot support the multilayer model on its own. There is little consensus about the role of N-rich OM in forming the contact zone according to the multilayer model but surface conditioning by different classes of organic compounds appears to be an essential factor for the overall adsorption of OM. Nevertheless, large uncertainty still remains with respect to multilayer-like organization of MOA. By taking advantage of recent developments in surface analytical sciences and computational chemistry, a rigid experimental testing of the multilayer model at the molecular level is still required and awaits to be integrated into improved concepts of MOA formation and OM stabilization.

AB - Association of organic matter (OM) with minerals is an important pathway in the formation of stable OM in soil. While the importance of mineral–organic associations (MOA) in regulating soil carbon cycling has been rigorously demonstrated by empirical evidence, knowledge about the molecular-scale arrangement of OM at mineral surfaces is still lacking. Such knowledge is urgently needed to disentangle the mechanisms of long-term storage of soil OM. Based on indirect observations regarding the formation, composition, and structure of MOA, a conceptual multilayer model was proposed by Kleber et al. in 2007 to foster debate and help elucidating the structure and reactivity of MOA. According to this model, the associated OM at mineral surfaces is discrete and self-organized into a multilayer structure. In this review, we aim to collect and evaluate existing studies that used this model to explain biogeochemical processes at mineral–organic interfaces, and based on this, assess the applicability of the model. The multilayer model has seen extensive adoption within soil science and related fields. In general, existing studies either support the concept of a patchy distribution of adsorbed OM on mineral surfaces or advocate that OM can be coprecipitated with nanosized poorly crystalline minerals or hydrolysable metals. However, the evidence for the patchy distribution of adsorbed OM cannot support the multilayer model on its own. There is little consensus about the role of N-rich OM in forming the contact zone according to the multilayer model but surface conditioning by different classes of organic compounds appears to be an essential factor for the overall adsorption of OM. Nevertheless, large uncertainty still remains with respect to multilayer-like organization of MOA. By taking advantage of recent developments in surface analytical sciences and computational chemistry, a rigid experimental testing of the multilayer model at the molecular level is still required and awaits to be integrated into improved concepts of MOA formation and OM stabilization.

KW - adsorption

KW - carbon dynamics

KW - mineral–organic associations

KW - soil organic carbon

KW - submicron imaging technique

UR - http://www.scopus.com/inward/record.url?scp=85076137334&partnerID=8YFLogxK

U2 - 10.1002/jpln.201900530

DO - 10.1002/jpln.201900530

M3 - Article

AN - SCOPUS:85076137334

VL - 183

SP - 27

EP - 41

JO - Journal of Plant Nutrition and Soil Science

JF - Journal of Plant Nutrition and Soil Science

SN - 1436-8730

IS - 1

ER -