Forty-year pollution history of microplastics in the largest marginal sea of the western Pacific

Marine sediments have been considered to be a major sink for microplastics, yet the pollution history of microplastics recorded in these sediments remains poorly understood. Using a combination of Pb-210 chronology and quantification of microplastics in undisturbed sediment cores, here we established the forty-year pollution history of microplastics in the northern South China Sea (SCS), the largest marginal sea of the western Pacific. We found that the pollution of microplastics in the northern SCS commenced in the 1980s. A dramatic increase of microplastic abundance in about 1998 marked an important breakpoint for microplastic contamination. Since then, microplastic abundances in the sediments have continued to increase and reached the highest level in 2018. This was well in line with the increasing trend of plastic output in the local industries. Reconstructing regional pollution history further revealed the shift of microplastic depocentres in the northern SCS over the past forty years. We estimated that the microplastic abundances in the sediments at nearshore stations will double by 2028. Our results provide the first example of the reconstruction of microplastic pollution history in marine sediments and new insights into how microplastics contaminated the marginal sea.