LC-MS/MS Detects Antibiotics in Olive Grove Soil

Chemical fertilizers used in farming are a major contributor to soil pollution, which is why keeping soil healthy over the long run matters so much. One way that farmers try to be more sustainable is by switching to organic farming and swapping out synthetic chemicals for natural alternatives like manure. The catch is that manure can carry leftover antibiotics, which could pose risks to people and the environment, including helping antibiotic-resistant bacteria develop. To look into this, researchers used liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) to check for nine different families of antibiotics in soil from 52 olive groves in five Mediterranean countries (Spain, Portugal, Italy, Greece, and Morocco) comparing soils managed in three different ways: traditional farming, high-density farming, and organic farming. The results showed that the type of farming method used was linked to different patterns of antibiotic contamination. A paper based on their efforts was published in the journal Environmental Research.¹

Why Does Farming's Contribution to Soil Pollution Matter, and Why Should Authorities Push for More Sustainable Farming Practices?

Although farming is still a major part of Europe's economy (making up 1.2% of the EU's GDP in 2024), it is also one of the biggest contributors to soil pollution.²In conventional farming, the main cause of soil pollution is the use of synthetic fertilizers and pesticides.³On top of that, these pollutants will not just stay in one place; through rain washing them away, seeping down into the ground, soil erosion, and even drifting through the air, they can spread into other ecosystems, including rivers, lakes, and groundwater.⁴This, in the opinion of the research team, is why authorities should be encouraging more sustainable farming approaches , such as conservation agriculture and organic farming, to help reduce farming's negative effects and keep it viable for the long haul.⁵

How Do Different Farming Methods Affect Antibiotic Contamination Levels, Depth Distribution, and Risk in Olive Grove Soils?

The research team reported that the results of their study showed clear patterns tied to farming method. Organically managed soils had the highest overall antibiotic levels, with one antibiotic, amoxicillin, reaching as high as 10.8 micrograms per kilogram; this, the researchers believe, is likely because of untreated organic fertilizers going into the ground. High-density and traditional farms had lower typical levels (between roughly 0.23 and 5.70 micrograms per kilogram), though high-density soils turned up antibiotics more often, even if the amounts were smaller.¹

When comparing the upper soil layer (0–10 cm) to the layer just below it (10–20 cm), there was not much difference overall in total antibiotic levels, which suggests that antibiotics move down through the soil fairly widely. However, that observation changed depending on the specific antibiotic: one group (fluoroquinolones), which tends to stick tightly to soil particles, mostly stayed near the surface, while another group (sulfonamides) sank down into the lower layer in some farming systems, raising concerns about them leaching further into the ground. Looking specifically at amoxicillin, there was not a major difference between the upper and lower layers within any single farming method, but the farming method itself did significantly affect how much amoxicillin showed up deeper in the soil.¹

Overall, most of the antibiotics found posed little to no real risk. The one exception was oxytetracycline, which showed a moderate risk in traditional and organic soils, even though it wasn't found very often (in under 6% of samples), raising concerns about longer-term effects like harm to plants and the potential for antibiotic resistance to develop.¹

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References

1. Rascón, A. J.; Fernández-García, A.; Moreno-Gónzalez, D. et al. Occurrence and Risk Assessment of Antibiotic Residues in Mediterranean Olive Grove Soils with Different Management: An EU-Wide Pilot Study. Environ Res. 2026, 125492. DOI: 10.1016/j.envres.2026.125492
2. Performance of the Agricultural Sector. Eurostat website 2025. https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Performance_of_the_agricultural_sect
3. Tang, F. H. M.; Wyckhuys, K. A .G.; Li, Z., et al. Transboundary Impacts of Pesticide Use in Food Production. Nat Rev Earth Environ. 2025, 6, 383-400. DOI: 10.1038/s43017-025-00673-y
4. Nuruzzaman, M.; Bahar, M. M.; Naidu, R. Diffuse Soil Pollution from Agriculture: Impacts and Remediation. Sci Total Environ. 2025, 962, 178398. DOI: 10.1016/j.scitotenv.2025.17839
5. Cárceles Rodríguez, B.; Durán-Zuazo, V. H.; Soriano Rodríguez, M. et al. Conservation Agriculture as a Sustainable System for Soil Health: A Review. Soil Systems2022, 6 (4), 87. DOI: 10.3390/soilsystems6040087