Microplastics increase nitrogen mobility in soils while biochar regulates NH4+ and NO3- transport: A soil column study

İbrahim Karaoğlanoğlu Aydoğan; Halil Erdem; Cabir Çağrı Gence

doi:10.24925/turjaf.v14i8.2304-2310.9066

Authors

İbrahim Karaoğlanoğlu Aydoğan Tokat Gaziosmanpaşa University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, 60250, Tokat, Türkiye https://orcid.org/0009-0002-0929-6779
Halil Erdem Tokat Gaziosmanpaşa University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, 60250, Tokat, Türkiye https://orcid.org/0000-0002-3296-1549
Cabir Çağrı Gence Aksaray University, Aksaray Technical Sciences Vocational School, Department of Plant and Animal Production, 68100, Aksaray, Türkiye https://orcid.org/0000-0001-9748-1303

DOI:

https://doi.org/10.24925/turjaf.v14i8.2304-2310.9066

Keywords:

Ammonium, Biochar, Microplastics, Nitrate, Nitrogen leaching

Abstract

This study investigated the effects of microplastics (MPs) and biochar (BC) on nitrogen (NH₄⁺ and NO₃^-) leaching and their vertical distribution in a soil column system. A completely randomized design with three replications was conducted using rice husk biochar (0% and 2% w/w) and microplastics (0%, 1%, and 2% w/w) under controlled leaching conditions. Nitrogen was applied as NH₄NO₃, and leachates were collected weekly over a six-week period. Results showed that microplastic application significantly increased both NH₄⁺ and NO₃^- losses from the soil system. The highest total nitrogen leaching occurred in the MP2BC0 treatment, indicating that microplastics impaired soil structural stability and enhanced nutrient mobility. In contrast, biochar application consistently reduced nitrogen leaching across all microplastic levels, demonstrating a strong mitigating effect. This reduction was associated with the high cation exchange capacity and porous structure of biochar. Vertical distribution results revealed that NH₄⁺ accumulated more in the 10-20 cm layer under control conditions, while microplastics enhanced ammonium depletion in both 0-10 cm and 10-20 cm layers. Biochar significantly improved NH₄⁺ retention across both depths. Similarly, NO₃^- showed strong downward mobility, which was intensified by microplastic application but partially restricted by biochar. Overall, the findings demonstrate that microplastics increase nitrogen leaching and vertical mobility in soil, whereas biochar acts as an effective soil amendment for mitigating these losses under microplastic contamination.

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