Recent Increased Loading of Carbonaceous Pollution from Biomass Burning in the Baltic Sea

Thin-layer capping with granular activated carbon and calcium-silicate to remediate organic and metal polluted harbor sediment - A mesocosm study

Sediments polluted with hydrophobic organic contaminants (HOCs) and metals can pose environmental risks, yet effective remediation remains a challenge. We investigated a new composite sorbent comprising granular activated carbon (GAC) and a calcium-silicate (Polonite®, PO) for thin-layer capping of polluted sediment, with the aim to sequester both HOCs and metals. Box cores were collected in polluted Oskarshamn harbor, Sweden, and the sediments were treated with GAC and/or Polonite in a 10-week mesocosm study to measure endpoints ranging from contaminant immobilization to ecological side effects on native fauna and biogeochemical processes. The GAC particle size was 300-500 μm to reduce negative effects on benthic fauna (by being non-ingestible) and of biogenic origin (coconut) to have a small carbon footprint compared with traditional fossil ACs. The calcium-silicate was a fine-grained industrial by-product used to target metals and as a carrier for GAC to improve the cap integrity. GAC decreased the uptake of dioxins (PCDD/Fs) in the bivalve Macoma balthica by 47 % and the in vitro bioavailability of PCB by 40 %. The composite cap of GAC + Polonite decreased sediment-to-water release of Pb < Cu < Ni < Zn < Cd by 42-98 % (lowest to highest decrease) and bioaccumulation of Cd < Zn < Cu in the worm Hediste diversicolor by 50-65 %. Additionally, in vitro bioavailability of Pb < Cu < Zn, measured using digestive fluid extraction, decreased by 43-83 %. GAC showed no adverse effects on benthic fauna while Polonite caused short-term adverse effects on fauna diversity and abundance, partly due to its cohesiveness, which, in turn, can improve the cap integrity in situ. Fauna later recovered and bioturbated the cap. Both sorbents influenced biogeochemical processes; GAC sorbed ammonium, Polonite decreased respiration, and both sorbents reduced denitrification. In conclusion, the side effects were relatively mild, and the cap decreased the release and bioavailability of both HOCs and metals effectively, thus offering a promising sustainable and cost-effective solution to remediating polluted sediments.

A methodological review of compound-specific radiocarbon analysis for polycyclic aromatic hydrocarbons in environmental matrices

Identifying the sources of polycyclic aromatic hydrocarbons (PAHs) in complex environmental matrices is essential for understanding the impact of combustion-related human activities on the environment. Since the turn of the century, advances in analytical capability and accuracy of accelerator mass spectrometry (AMS) have made it possible to accurately determine the source apportionment of PAHs based on their radiocarbon (14C) mass conservation. This also allows us to trace the environmental transport processes of PAHs from the perspective of molecular 14C. However, natural environmental matrices have very low concentrations of PAHs (ppb to ppm level). To meet the requirements of carbon weight for 14C measurement by AMS, trace PAHs in complex environmental matrices must be enriched thousands of times, and then higher purity individual PAH molecules should be obtained through a series of complex purification procedures. Therefore, the technical difficulty is the main challenge in expanding the application of compound-specific 14C analysis in environmental science. This article reviews the detailed pretreatment procedures for 14C measurement of specific PAHs, including sample enrichment, extraction and purification of aromatic components, preparation of compound-specific PAHs by preparative capillary gas chromatography, graphitization of samples with ultra-small carbon content, and relevant quality control and assurance procedures. This study aims to help environmental geoscientists understand the technical process of 14C analysis of PAHs and inspire new scientific questions related to environmental science. To our knowledge, this is the first comprehensive review of the technical method of compound-specific 14C analysis for PAHs.

Historic distribution of Polycyclic Aromatic Compounds (PAC) in a Skagerrak fjord, Swedish west coast as reflected in a high-resolution sediment record and compared to the Environmental Quality Standards (EQS)

We present the historic distribution of Polycyclic Aromatic Compounds (PAC) in a Skagerrak fjord, a relatively unexploited area, on the Swedish west coast. PACs encompass various compounds, including PAHs, alkyl-PAHs, nitro-PAHs, and oxy-PAHs. These compounds, have environmental implications due to their harmful properties. Using a high-resolution sediment record, PAC variations including standard PAHs, nitro-PAHs and oxy-PAHs were investigated over the last approximately 170 years, comparing them with other European records. The sediment record reveals a significant increase in PAC levels during the 1940s-1950s, followed by peaks in the 1960s and 1970s, and a subsequent decrease in the 1980s. These trends align with industrial growth and evolving stronger environmental regulations in the region. The highest recorded concentration of PACs (1950-1970) reached levels comparable to present-day polluted urban environments. The study also compared PAH levels with EQS values. Results indicated that PAH levels exceeded EQS standards, potentially posing risks to sediment-dwelling organisms.