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Influence of microplastics on the availability of antibiotics in soils
Suyu Ren1, Yuxiang Xia1, Xiaojie Jin2
1School of Environmental and Material Engineering, Yantai University, Yantai 264005, China.
Abstract:
Microplastics (MPs) and antibiotics, as two major types of emerging pollutants, inevitably coexist in the soil environment due to agricultural film residue, sewage irrigation and sludge application. However, the impact of MPs on antibiotic availability in soils with varying characteristics has not been extensively studied. Therefore, in this study, an interference experiment was conducted using three types of MPs (polyethylene (PE), polyvinyl chloride (PVC) and polypropylene (PP)) in red soil, paddy soil and cinnamon soil. The available antibiotics in soils were evaluated using diffusive gradients in thin-films (DGT). Results showed that MPs had a significant impact on the amount of antibiotics adsorbed on soil solid (Cs) by providing additional binding sites or altering soil characteristics (e.g., pH and dissolved organic carbon). The most significant effects on Cs were observed in cinnamon soil, and the Cs values were dependent on concentration of MPs. The available antibiotics, as measured by DGT significantly decreased after the addition of MPs. This decrease was influenced by the soil characteristics. However, the concentration of antibiotics in soil solutions (Cd) was only slightly impacted by MPs. Therefore, the influence of MPs on the migration of antibiotics was reflected by their impact on the soil/water partition coefficient (Kd), while the resupply ability (R) from the soil solid phase was less influential. Moreover, the dosage of MPs had a significant effect on the availability of antibiotics in CS by promoting the adsorption of antibiotics on the solid phase, while in RS and PS, the soil properties played a dominate role in the changes in antibiotic availability after MP addition. These results indicate that the impact of MPs on available antibiotics mainly depends on soil properties. In addition, DGT measurement is more sensitive than soil solution to investigate the effects of coexisting pollutants on the behavior of antibiotics in soil.
Insights
Microplastics (MPs) significantly reduce available antibiotics in soil by altering adsorption, with effects varying by soil type. Diffusive gradients in thin-films (DGT) measurements are more sensitive than soil solutions for assessing these impacts.
Area of Science:
- Environmental Science
- Soil Science
- Ecotoxicology
Background:
- Microplastics (MPs) and antibiotics are prevalent emerging soil pollutants.
- Their combined impact on antibiotic availability across diverse soil types is poorly understood.
Purpose of the Study:
- To investigate how three types of MPs (polyethylene, polyvinyl chloride, polypropylene) affect antibiotic availability in red, paddy, and cinnamon soils.
- To evaluate the role of soil characteristics and MP concentration on antibiotic adsorption and mobility.
Main Methods:
- Interference experiments using polyethylene (PE), polyvinyl chloride (PVC), and polypropylene (PP) MPs.
- Quantification of available antibiotics using diffusive gradients in thin-films (DGT).
- Analysis of antibiotic adsorption (Cs), soil solution concentration (Cd), soil/water partition coefficient (Kd), and resupply rate (R).
Main Results:
- MPs significantly increased antibiotic adsorption to soil solids (Cs), particularly in cinnamon soil, and decreased available antibiotics measured by DGT.
- The impact of MPs on Cs was concentration-dependent, while soil properties (pH, dissolved organic carbon) modulated the overall decrease in antibiotic availability.
- Antibiotic concentration in soil solutions (Cd) was only slightly affected, indicating MPs primarily influence adsorption rather than direct dissolution.
Conclusions:
- MP presence significantly alters antibiotic availability in soils, primarily by enhancing adsorption to soil solids.
- The extent of this alteration is strongly dependent on intrinsic soil properties, with MP concentration playing a key role in some soils.
- Diffusive gradients in thin-films (DGT) offer a more sensitive method than soil solutions for detecting the influence of co-existing MPs on antibiotic behavior in soil environments.
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