Pesticides contamination across soil, water, and components of a paddy in paddy fields of Thrace and Marmara region, Türkiye: occurrence, transfer, and health risk assessment

Abstract

Context—Paddy fields are prone to multi-matrix contamination because prolonged flooding can enhance exchanges between soil, water, and plant compartments, allowing pesticide residues to persist and potentially reach edible tissues. In Türkiye, evidence remains limited for stage-resolved monitoring that simultaneously links residue occurrence in environmental compartments and rice tissues with exposure and health-risk metrics in major rice-producing regions.Objective—This study investigated the occurrence, temporal variation, and health risk implications of pesticide residues in monoculture paddy fields in Ipsala and Biga (Türkiye) during the 2024 growing season.Method—Residues were extracted using the QuEChERS procedure and analyzed by LC–MS/MS across multiple matrices, including soil, water, shoot, stubble, husk, and harvested rice grain. Descriptive and association analyses were applied to characterize matrix-specific occurrence patterns and site-dependent co-occurrence among detected compounds. Matrix-to- matrix transfer was evaluated using concentration-ratio metrics to indicate empirical partitioning under flooded field conditions. Human health risks (carcinogenic and non-carcinogenic) for adults and children were assessed using the US EPA modeling framework.Results—Soil showed the highest residue occurrence, with detection frequencies of 45–52%, followed by notable detections in stubble and shoot. Temporal profiles differed by compound and site. In Biga, tridemorph remained elevated in soil and water and increased in husk and grain at harvest, whereas oxadiazon was largely associated with stubble at harvest with minimal levels in husk and grain. In Ipsala, clomazone showed a high pre-planting soil concentration followed by lower levels later in the season, and tridemorph decreased across harvest fractions (stubble: 40.7; husk: 29.5; grain: 21.7 µg kg⁻¹). Tridemorph and oxadiazon were detected in both regions despite being unauthorized in Türkiye, with tridemorph exceeding the maximum residue limit (MRL) in harvested rice grains. Correlation analysis suggested region-specific patterns, with a strong positive association between azoxystrobin and flutriafol in Biga (r = 0.97; p < 0.001) and a more complex co-variation structure was observed in Ipsala, which may reflect co-occurrence or matrix-specific distribution patterns. These active ingredients were also recorded in the pesticide application history of the study fields. Human health risk assessment results suggested that estimated non- carcinogenic and, where applicable carcinogenic risks for adults and children, calculated using the US EPA framework, remained within commonly applied regulatory acceptability thresholds.Conclusion—The findings suggest that pesticide residues may persist and partition differently across interconnected paddy matrices under field conditions and that unauthorized or legacy compounds can be detected, including in edible grain. Continued multi-matrix monitoring that considers stage-dependent behavior, together with source-to-receptor evaluation of transfer pathways, may support compliance checks and risk-informed management to improve the long-term sustainability of rice production in key Turkish rice-growing regions.