Legacy contaminants in polar sediments: A critical perspective

This review provides a comprehensive overview of 73 research works on the occurrence and analysis of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs) in marine sediments from polar regions. It examines the range of sample preparation strategies and highlights key methodological considerations. Reported concentrations and spatial distributions of legacy contaminants are assessed, identifying the most prominent compounds within each chemical class. Among all studies reviewed, PAHs were consistently detected at higher concentrations than PCBs and pesticides, occasionally exceeding 10,000 ng/g dw in samples collected near local pollution sources. A subset of rarely monitored PCB congeners was found to occur frequently and at comparable or higher levels than the traditional indicator PCBs, suggesting that current monitoring programs may underestimate total PCB burdens. As regards pesticides, most studies focused exclusively on legacy OCPs such as DDT, HCH, or chlordane, while currently used pesticides remain largely unaddressed, which hinders the assessment of modern agricultural inputs reaching polar ecosystems. This review also evaluates the common use of total organic carbon (TOC) as a normalization factor, noting the weak correlation often observed with pollutant levels. Cross-comparisons with other environmental compartments - biota, air, and water - are discussed to explore sediments-environmental linkage. Lastly, we identify methodological gaps and report inconsistencies that hinder a comprehensive evaluation and comparison of results across studies. This work aims to consolidate existing knowledge, propose recommendations for more harmonized practices, and serve as a critical reference and practical guide for future research in polar contaminant monitoring.