Overview of the Policies for Phasing Out Ocean Dumping of Sewage Sludge in the Republic of Korea

Distributions and compositional characteristics of per- and polyfluoroalkyl substances (PFASs) in sediments of the regional seas of South Korea

This study investigated the distribution and composition of 28 per- and polyfluoroalkyl substances (PFASs) in surface and core sediments from the regional seas of South Korea. Surface sediments were collected from the Yellow Sea (YS, n = 10), East China Sea (ECS, n = 6), South Sea (SS, n = 5), and East Sea (ES, n = 12), and core sediments were obtained from the ES (n = 3, 0-30 cm). Sediment samples were extracted with methanol by shaking, followed by purification using solid-phase extraction cartridges. The purified extracts were then analyzed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to quantify 11 perfluoroalkyl carboxylic acids, 9 perfluoroalkyl sulfonic acids, 5 precursors, and 3 emerging PFASs. The highest PFAS concentrations in surface sediments were observed in the YS (300 ng g-1 organic carbon (OC)), followed by the ES (150 ng g-1 OC), ECS (120 ng g-1 OC), and SS (14 ng g-1 OC). Core sediment analysis revealed the accumulation of PFASs within the top 10 cm depth at the dumpsite, along with elevated OC contents (2.7-4.4 %) and lighter carbon stable isotope ratios (δ13C, -23 to -22 ‰) indicating the influence of dumped wastes. Principal component analysis classified the sites into three groups based on chemical composition, reflecting regional differences in PFASs usage, transport, and deposition. These findings provide critical insights into the distribution and environmental behavior of PFASs in marine sediments and contribute to developing future regulatory frameworks and pollution management strategies.

A review on waste activated sludge pretreatment for improved volatile fatty acids production and their upcycling into polyhydroxyalkanoates

Waste activated sludge (WAS), a byproduct of wastewater treatment (WWTPs) facilities is challenging to manage because of its high organic content. Most of WAS is managed via anaerobic digestion (AD) to produce biogas, which is not deemed economically viable. The AD of WAS into volatile fatty acids (VFA) and their subsequent upcycling into polyhydroxyalkanoates (PHA) is gaining popularity due to their high value and uses. However, the fundamental issue with WAS is its low solubility, and pretreatment is required to increase it. Pretreatment disintegrates sludge floc and enhances its solubility, supports acetogens, and inhibits methanogens, leading to increased VFA synthesis in the AD process. The key factors influencing VFA yield include the size of the sludge granules, the mixing rate, and the presence of resistant organic components. Fermented broth containing VFA from AD can be utilized directly as a feedstock for microbial fermentation to produce PHA using both pure as well as mixed cultures. Utilisation of mixed cultures is useful since they are robust, able to consume a wide range of substrates, and do not require sterility. In addition, the VFA, which is made up of various organic acids, impacts the structure, productivity, characteristics, and type of PHA produced by microbial communities. Considering the importance of WAS management through VFA production and its integration with PHA production process this review article discusses the WAS pretreatment strategies, various factors that influence the AD process, trends in VFA to PHA production technologies with challenges, and possible solutions for integrated process development.

Applying new regional background concentration criteria to assess heavy metal contamination in deep-sea sediments at an ocean dumping site, Republic of Korea

It is crucial to establish appropriate background concentrations to discern heavy metal pollution in the marine environment. In this study, we analyzed heavy metals in deep-sea sediment cores to determine regional background concentrations at the East-Sea Byeong Ocean dumping site. The vertical profiles of heavy metals were categorized into three groups based on their contamination characteristics, and regional background levels for 12 metals were determined using pre-1900 averages. The enrichment factor, contamination factor, and pollution load index, calculated using regional background concentrations, indicated significant contamination by Cr, Co, Cu, Zn, Cd, Hg, and Pb during the ocean dumping period. These results differ from those obtained using global average concentrations. This underscores the importance of considering regional characteristics to minimize the risk of misinterpreting anthropogenic impacts. The approach based on local information is considered useful when sediment quality guidelines are absent or inapplicable.

Heavy metal characterization of land-based waste dumped at three ocean dumping sites in the Republic of Korea

From 1991 to 2021, 16 categories of land-based waste, totaling 131,400,000 m³, were dumped at three sites in Korea. The concentration of heavy metals varied by waste type, with organic sludge showing higher levels than liquid waste. While wastewater treatment sludge was the most commonly discarded waste, the quantity and types of waste disposed of varied by site. Before the 2015 ban on ocean dumping, 62,330 tons of heavy metals were introduced, including zinc, copper, chromium, lead, arsenic, cadmium, and mercury in descending order of frequency. In each heavy metal category, the portion of land-based waste varied by dumping site. Compared to heavy metals from atmospheric deposition, anthropogenic heavy metal input from dumping was up to 141 times higher for copper. This study serves as a reference for estimating the impact of pollutants from dumped waste.

Distribution and assessment of heavy metal concentrations in the East Sea-Byeong ocean dumping site, Korea

Sediment cores were collected from three sites, the Control, Dumping, and Resting sites in the East Sea-Byeong ocean dumping site, Korea, and the enrichment and degree of accumulation of heavy metals were investigated. Further, to assess the level of heavy metal pollution and understand the potential effects of the ocean dumping activities that began in 1993, the results obtained corresponding to the different sampling sites were compared, and various criteria were employed. Indices, including the enrichment factor and the modified contamination degree, demonstrated that the sediments were contaminated with various heavy metals at different contamination levels. The results also indicated a significant upward enrichment in heavy metals, with the uppermost 0-10 cm sediment layer showing relatively high concentrations. Overall, this study confirmed that anthropogenic heavy metal contamination at the study sites, and the implementation of continuous monitoring, alongside the application of proper management tools, is recommended.