Effects of Di-n-octyl Phthalate (DNOP) on Sinapis alba in a Microcosm Experiment

Abstract

Phthalates, such as di-n-octyl phthalate (DnOP), are micropollutants released from microplastics, entering the environment mainly through biowaste collected and stored in plastic bags. When compost becomes contaminated, these compounds may be transferred into agricultural systems, potentially reducing crop yield and quality as well as posing risks to food safety. This study examined DnOP leaching from PVC under different conditions and its effects on white mustard (Sinapis alba) in a microcosm experiment with the aim of evaluating agricultural risks. Leaching experiments showed that DnOP release was most pronounced in water, reaching 60.43 µg/L by Month 6. In contrast, release into soil was minimal with only 14.41 µg/L detected, suggesting stronger retention. The ‘Simple’ samples displayed consistent and significant increases over time with concentrations of up to 45.25 µg/L measured. Plant experiments revealed that DnOP inhibited germination and early growth in a concentration-dependent manner. By Day 12, control plants grew to a height of 5.5 cm, while those exposed to 200 mg/L DnOP were only 3 cm tall. By Day 30, plants that were exposed were shorter due to a reduction in growth rate and visible stress, although flowering was observed, indicating an altered growth strategy under chemical pressure. Importantly, no distinct morphological abnormalities were detected, even at the highest concentrations. Chemical analysis confirmed a dose-dependent accumulation of DnOP in plant tissues. Uptake was particularly significant between 100 and 150 mg/L, resulting in a 13.8% increase, while the rise between 150 and 200 mg/L was smaller (+6.1%). Plants exposed to higher concentrations contained nearly double the DnOP levels of their control counterparts, highlighting the significance of the growth medium and high exposure scenarios. The findings demonstrate that substantial amounts of DnOP can accumulate in white mustard. Further studies are needed to clarify its impact on plant nutrient metabolism, particularly sulfur-related compounds, as yield, nutritional quality and agricultural sustainability might be under threat.