Warming exponentially stimulates photoleaching of dissolved organic matter from multiple microplastics

Xiaoxia Cai; Randy A Dahlgren; Yan Li; Dezhong Wang; Liyin Qu; Xufeng Xie; Xinhong Wang; Weidong Guo

doi:10.1016/j.jhazmat.2025.139079

Warming exponentially stimulates photoleaching of dissolved organic matter from multiple microplastics

J Hazard Mater. 2025 Jun 26:495:139079. doi: 10.1016/j.jhazmat.2025.139079. Online ahead of print.

Authors

Xiaoxia Cai¹, Randy A Dahlgren², Yan Li³, Dezhong Wang⁴, Liyin Qu⁵, Xufeng Xie⁴, Xinhong Wang⁶, Weidong Guo⁷

Affiliations

¹ State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361012, China; College of Ocean and Earth Sciences, Xiamen University, Xiamen 361012, China.
² Department of Land, Air and Water Resources, University of California, Davis 95616, USA.
³ National Observation and Research Station for the Taiwan Strait Marine Ecosystem (Xiamen University), Zhangzhou 363400, China.
⁴ College of Ocean and Earth Sciences, Xiamen University, Xiamen 361012, China.
⁵ National and Local Joint Engineering Research Center of Ecological Treatment Technology for Urban Water Pollution, Wenzhou University, Wenzhou 325035, China.
⁶ College of the Environment and Ecology, Xiamen University, Xiamen 361102, China.
⁷ State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361012, China; College of Ocean and Earth Sciences, Xiamen University, Xiamen 361012, China. Electronic address: wdguo@xmu.edu.cn.

PMID: 40580737
DOI: 10.1016/j.jhazmat.2025.139079

Abstract

The substantial release of microplastics (MPs) into the marine environment is now deeply integrated into Earth's carbon cycle. However, the mechanisms by which warming regulates the release of MP-leached dissolved organic matter (MP-DOM) in seawater media remain highly uncertain. This work considers four typical MPs that enter the ocean (polyethylene, PE; polypropylene, PP; polyethylene terephthalate, PET; and polyvinyl chloride, PVC) over 1-week experiments under UV light and dark conditions at a narrow temperature interval of 5 °C between10-35 °C. The results indicate that different MPs have variable photoleaching rates of dissolved organic carbon (MP-DOC, 0.06 ± 0.01-0.61 ± 0.07 mg-C/g-MP/week) and fluorescent DOM (MP-FDOM). An unexpected inconsistency emerged in the photoleaching of MP-DOC and MP-FDOM, with dominant MP-DOC release for PE, PP and PVC, while PET showed substantial release of both. The humification index and biological index pair is a useful indicator to distinguish MP-DOM versus natural DOM. The Q₁₀ values, which reflect the temperature sensitivity of MP-DOC photoleaching, ranged from 1.62 (PVC) to 1.93 (PET) indicating an exponential increase in MP-DOC leaching rates with rising temperature. These findings highlight the need for incorporating ocean warming into predicting the effects of plastic pollution on the marine carbon cycle.

Keywords: Dissolved organic carbon; Microplastic degradation; Ocean warming; Temperature sensitivity; UV irradiation.