Temporal/Spatial signals of PCBs in global sediment cores mimics global PCB production: Analysis

The stratigraphic record of legacy pollutants such as polychlorinated biphenyls (PCBs) in lake sediments offers a powerful tool for tracking temporal inputs and historical production, usage, and regulation on regional to global scales. PCBs were extensively produced and used worldwide from the 1940s until the 1970s, with total production estimated at approximately 1,314 million Tonnes. Due to their chemical properties (ow water solubility, low vapor pressure, high affinity for organic matter, and environmental persistence), PCBs are transported long distances through the atmosphere, rivers, and ocean currents, ultimately accumulating in sediments of lakes, rivers, and marine systems. As a result, PCBs are now ubiquitous, found even in remote environments such as polar regions, high-altitude lakes, and oceanic depths. This study investigates the temporal signal of PCBs in dated sediment cores from lakes across the globe and examines the synchronicity of sedimentary PCB records with global production and regulatory milestones, particularly the bans enacted in the 1970s. PCB profiles in sediment cores strongly reflect the Anthropocene signal, offering insights into industrial activity, environmental transport, and the effects of regulatory intervention. Global production of PCBs peaked ~ 1972, coinciding with open-use bans, followed by further restrictions in closed systems by 1979. This production timeline is mirrored in many dated sediment cores, which show rising concentrations beginning in the 1940s, accelerating in the 1950s, peaking in the ~1970, and declining thereafter. However, some lake cores reveal elevated PCB levels in more recent sediments, deviating from global trends. These anomalies are attributed to local factors such as glacial meltwater inputs, remobilization from contaminated horizons, local and delayed PCB usage, flooding, illegal use, leakage from remaining stockpiles, and mixing of surface sediments due to bioturbation. The strong temporal coherence between sedimentary PCB records and global production trends, especially in North America and Europe, suggests rapid environmental transport and deposition, with lag times as short as 1–2 years. This underscores how industrial chemicals in commerce can quickly reach environmental sinks and be preserved in the sedimentary archive, offering a detailed chronicle of human impact on the environment. • The onset of PCBs in the early 1940s suggests that PCBs were produced, used, emitted and deposited in aquatic systems as soon as they were produced, used and exposed to the environment. This is likely the case for other industrial chemicals as well as infamous agrichemicals such as DDT. • The temporal profiles of PCB in global aquatic sediment cores are coincident with an increase in PCB production/emissions. • The ban of PCBs in open and closed systems from 1972 to 1979 led to a major PCB decrease in global lake sediment cores proportional to the decrease in global production. • The PCB concentrations/accumulation rates in lake sediment cores in recent times results from emissions both from primary sources, and mobilisation from secondary sources (i.e., vegetation, soils, water). • The apparent coincidence in the temporal profile of global PCB production/use and occurrence in sediment cores suggests that long range transport of primary emissions is limited (~ 100 s to 1000 km). It is likely that low MW PCB congeners have transport distances of several 1000 kms. • The similar temporal profiles of PCBs in sediment cores and ombrotrophic peat cores suggest that PCBs emitted into a river basin are distributed to the atmosphere and land with a similar time constant. • The agreement of PCB temporal profiles in sediment cores at a global scale and to the global PCB production profile suggest that the sediment dating techniques employed ( 210 Pb) across many studies are comparable and accurate.