Occurrence, distribution and sources of microplastics in typical marine recirculating aquaculture system (RAS) in China: The critical role of RAS operating time and microfilter

Zheng Zhou; Xiefa Song; Dengpan Dong; Xian Li; Yue Sun; Liwei Wang; Zhitao Huang; Meng Li

doi:10.1016/j.watres.2024.121476

Occurrence, distribution and sources of microplastics in typical marine recirculating aquaculture system (RAS) in China: The critical role of RAS operating time and microfilter

Water Res. 2024 May 15:255:121476. doi: 10.1016/j.watres.2024.121476. Epub 2024 Mar 14.

Authors

Zheng Zhou¹, Xiefa Song², Dengpan Dong¹, Xian Li¹, Yue Sun¹, Liwei Wang¹, Zhitao Huang³, Meng Li⁴

Affiliations

¹ College of Fisheries, Ocean University of China, Qingdao 266003, PR China.
² College of Fisheries, Ocean University of China, Qingdao 266003, PR China. Electronic address: yuchuan@ouc.edu.cn.
³ Norwegian Institute for Water Research (NIVA), Thormøhlengate 53 D, Bergen 5006, Norway.
⁴ College of Fisheries, Ocean University of China, Qingdao 266003, PR China. Electronic address: limeng2022@ouc.edu.cn.

PMID: 38503181
DOI: 10.1016/j.watres.2024.121476

Abstract

Industrial mariculture, a vital means of providing high quality protein to humans, is a potential source of microplastics (MPs) which have recently received increasing attention. This study investigated the occurrence and distribution of microplastics in feed, source water and recirculating aquaculture system (RAS) with long & short operating times as well as in fish from typical industrial mariculture farms in China. Results showed that microplastics occurred in all samples with the average concentration of 3.53 ± 1.39 particles/g, 0.70 ± 0.17 particles/L, 1.53 ± 0.21 particles/L and 2.21 ± 0.62 particles/individual for feed, source water, RAS and fish, respectively. Microplastics were mainly fiber in shape, blue in color and 20-500 μm in size. Compared with short operated RAS, long operating time led to higher microplastic concentration in RAS, especially that of microplastic in 20-500 μm, granular and blue. Regardless of short or long operating time, microplastics in RAS mainly gathered in culture tank, tank before microfilter and fixed-bed biological filter, and the microfilter removed efficiently the microplastic with the shape of film, granule, fragment as well as those with size > 1000 μm. As for the polymer types, polyamide (PA, 71.9 %) and polyethylene terephthalate (PET, 65.7 %) dominated in feed and source water, respectively, which may be the reason for the high proportion of PA (38.8 % and 26.4 %) and PET (31.8 % and 30.2 %) in RAS and fish. In addition, polypropylene (PP) was also detected in RAS (18.7 %) and fish (22.6 %), indicating that other plastic facilities such as PP brush carrier also made a contribution. Positive matrix factorization (PMF) model revealed three sources of MP in RAS, namely plastic facilities, industrial sewage and plastic packaging products. Our results provided a theoretical basis for the management of MP in RAS.

Keywords: Microplastic; Occurrence & distribution; Positive matrix factorization; Recirculating aquaculture system; Source analysis.