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pH-Dependent Effects of Polystyrene Microplastics on Ciprofloxacin Toxicity and Uptake by Lolium perenne L
Yun Wang1, Ning Shan1, Zumrat Habibul2
1College of Chemistry and Chemical Engineering, Xinjiang Normal University, Urumqi, 830054, China.
Abstract:
This study investigated the impact of pH on the combined toxicity of polystyrene microplastics (MPs) and ciprofloxacin (CIP) on ryegrass growth and CIP uptake. Two different sizes of PS-COOH (200 and 500 nm) were utilized. The findings indicated that neutral and alkaline pH conditions (pH 7.0 and 8.8) significantly reduced CIP accumulation in ryegrass roots, regardless of MP presence. Conversely, CIP content in shoots (including leaves) increased with rising pH, showing 24.7-fold and 29.5-fold enhancements under CIP + 200 nm MPs and CIP + 500 nm MPs treatments at pH 8.8 compared to pH 5.3. Additionally, pH significantly influenced growth inhibition, with more pronounced effects at pH 7.0 and 8.8 than at pH 5.3. Under neutral and alkaline conditions, shoot lengths in 500 nm MPs + CIP and 200 nm MPs + CIP treatments were reduced to 50.3%, 69.7% and 86.8%, 81.3% of those at pH 5.3, respectively. These findings highlight the critical role of pH in modulating CIP uptake and toxicity in ryegrass, particularly in MP co-contaminated environments. Moreover, the relatively high CIP removal efficiency suggests the potential of ryegrass for CIP remediation in MP-polluted systems.
Insights
This study shows that pH significantly affects how much ciprofloxacin (CIP) is absorbed by ryegrass and how toxic it is, especially when microplastics (MPs) are present. Higher pH levels increase CIP in shoots and inhibit growth more severely.
Area of Science:
- Environmental Science
- Ecotoxicology
- Plant Science
Background:
- Microplastics (MPs) and pharmaceuticals like ciprofloxacin (CIP) are emerging environmental contaminants.
- The combined toxicity and fate of MPs and CIP in terrestrial ecosystems are not fully understood.
- Environmental factors, such as pH, can influence the behavior and bioavailability of these contaminants.
Purpose of the Study:
- To investigate the impact of pH on the combined toxicity of polystyrene microplastics (MPs) and ciprofloxacin (CIP) on ryegrass.
- To determine how pH affects the uptake of CIP by ryegrass in the presence of MPs.
- To assess the influence of pH on ryegrass growth inhibition under co-contamination.
Main Methods:
- Ryegrass was exposed to two sizes of carboxylated polystyrene microplastics (PS-COOH; 200 and 500 nm) and ciprofloxacin (CIP) at different pH levels (5.3, 7.0, and 8.8).
- CIP accumulation in ryegrass roots and shoots was quantified.
- Ryegrass shoot length was measured to assess growth inhibition.
Main Results:
- Neutral and alkaline pH (7.0 and 8.8) significantly reduced CIP accumulation in ryegrass roots.
- CIP content in ryegrass shoots increased with rising pH, with substantial fold-increases observed at pH 8.8.
- pH significantly influenced growth inhibition, with more pronounced effects at neutral and alkaline conditions, leading to reduced shoot lengths.
Conclusions:
- pH plays a critical role in modulating CIP uptake and toxicity in ryegrass, particularly in environments co-contaminated with MPs.
- The findings suggest that ryegrass exhibits potential for CIP remediation in MP-polluted systems due to high CIP removal efficiency.
- Understanding pH-dependent interactions is crucial for assessing the ecological risks of combined MP and pharmaceutical pollution.
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