Interaction of soil humin fraction with pesticides - a review

The use of pesticides significantly influences the efficiency of agriculture production, but at the same time, their extensive and widespread use, raises serious concerns regarding the release of harmful substances into the environment [1,2]. The fate of pesticides in soil depends on many factors related mainly to the physico-chemical properties of these compounds as well as content and quality of organic matter [3]. Humin as the predominant fraction of organic matter, may significantly determine the behavior and transformations of pesticides in soil [5]. Therefore, the aim of this review was to present the state of the art of humin-pesticides mutual interactions.

Sorption-related studies showed that humin has dissimilar binding strengths with pesticides [4,5]. According to Pignatello [7], the sorption selectivity by humin has a number of potential causes: (1) preference for particular microdomains within fractions that are envisioned to segregate on the basis of functional group identity (aromatic, paraffinic, carbohydrate domains); (2) preference based on strong functional group interactions, such as hydrogen bonding and (3) preference based on the nature of the thermodynamic physical state of humin, namely the configurations and conformations of the molecules and strands at microstructural level.

Moreover, humin exhibits potentially different accumulation capacities for xenobiotics. Wang et al. [9] explained these relations with the limited accessibility to microporous domains of humin matrices for the larger-molecular-weight particles. The authors [9] observed a lower adsorbed mass of spatially developed compounds compared to compounds with small diameters. This process is probably most likely related to the structural rearrangement of the humin matrix under slow diffusion into microporous domains pronounced with the adsorption of large molecular weight compounds. Additionally, Pignatello [7] as well as Schaumann [4,5] indicated that the humin surface is covered with various polar and non-polar functionalities, which may efficiently interact with pesticides by van der Waals forces, hydrophobic attraction, hydrogen bonding, charge transfer or ligand exchange processes. Nevertheless, the chemical properties of pesticides as well as their coexistence with other chemical compounds i.e.: surfactants, coagulants, decomposition inhibitors and others [8] can modify the interactions of pesticides with humin in natural soil environment.

Literature:

[1] FAO, ITPS Global Assessment of the Impact of Plant Protection Products on Soil Functions and Soil Ecosystems. FAO, Rome 2017, 40 pp.

[2] Silva, V.; Mol, H.; Zomer, P.; Tienstra, M.; Ritsema, C.J.; Geissena, V. Sci. Total. Environ.  2019, 653, 1532–1545.

[3] Stolte, J.; Tesfai, M.; Øygarden, L.; Kværnø, S.; Keizer, J.; Verheijen, F.; et al. Soil Threats in Europe: Status, Methods, Drivers and Effects on Ecosystem 4 Services, 2016, Report

[4] Stevenson F. 1994, John Wiley & Sons, New York

[5] Schaumann G. 2006a, J Plant Nutr Soil Sci 169:145–156

[6] Schaumann G. 2006b, J Plant Nutr Soil Sci 169:157–167

[7] Pignatello J. 2012,  J Soils Sediments 12:1241–1256

[8] Ehlers, G.; Loibner, A. 2006, Environ. Pollut. 141, 494-512

[9] Wang X, Guo X, Yang Y, Tao S, Xing B. 2011, Environ Sci Technol 45:2124–2130

 

Acknowledgement: The studies were supported from the National Science Centre project no. 2018/31/B/ST10/00677 “Chemical and spectroscopic properties of soil humin fraction in relation to their mutual interaction with pesticides”