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.

Long-term effects of chromium from red mud (bauxite residue) ocean dumping on the benthic environment in South Korea.

Between 1999 and 2009, 344,000 m3 of red mud was released into the red mud dumping zone in the East Sea-Byeong ocean dumping site in South Korea. This study aimed to assess the impacts before and after the 2010 red mud dumping ban. We quantified total Cr concentrations by depth from core sediment samples at the red mud dumping station and evaluated benthic communities in 2004, 2009, 2012, 2017, and 2019. At the dumping station DB-085, the Cr content in the upper layer (0-10 cm) exceeded the effect range median criteria in all study years and decreased with time. Geochemical fraction studies using sequential extraction methods from core sediment samples in 2004, 2009, and 2017 showed high ratios of non-residual fractions (anthropogenic inputs), indicating persistent potential long-term risk after the 2010 ban. Additionally, we confirmed that Thyasira tokunagai, an opportunistic and contamination-stress-resistant species, dominated the study station.

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.

Fractionation and risk assessment of metals in sediments of an ocean dumping site.

Sediments of Yellow Sea dumping sites (YSDS) collected in 2015 were analyzed using the European Community Bureau of Reference (BCR) sequential extraction method to assess the contamination and potential risk to the environment. Cr, Ni, Cu, and Zn exhibited the most dominant residual fraction, whereas Cd was mostly in the exchangeable fraction and Pb in the reducible fraction. Cr contains a significant amount of oxidizable fraction in the dumping area due to the dumping of tannery sludge with high concentrations of Cr, mainly in the organic matter-bound form. The global contamination factor (GCF) showed that high non-residual fractions of Cd and Pb contributed considerably to contamination. Nevertheless, modified potential ecological risk index (MRI) suggested low ecological risk for metals in YSDS because of the low total content of Cd and the small mobile fraction of other metals.

Variations in the concentrations of heavy metals through enforcement of a rest-year system and dredged sediment capping at the Yellow Sea-Byung dumping site, Korea.

In 2014, the concentrations of 13 heavy metals in surface sediments from 14 sampling stations were analyzed and compared to samples from previous years to evaluate the remediation effectiveness of the "rest-year" (RY) system and capping with dredged material at the Yellow Sea-Byung dumping site offshore Korea. Since the 2006 introduction of the RY system, annual variations in metal concentrations at stations within the RY zone have gradually decreased over time. Heavy metal concentrations at most stations were lower than sediment quality guidelines, indicating the success of the RY system. Additionally, the effects of capping the contaminated sediment with dredged materials were investigated. The results indicate that dredged materials successfully capped the contaminated sediment within the dredged material dumping area, as the concentrations of Cr and total organic carbon were significantly reduced. We conclude that dredged materials may be used as capping materials for the remediation of contaminated sediments.

Contribution of the proximal nerve stump in end-to-side nerve repair: in a rat model.

BACKGROUND: The aim of this study was to evaluate the contribution of the proximal nerve stump, in end-to-side nerve repair, to functional recovery, by modifying the classic end-to-side neurorrhaphy and suturing the proximal nerve stump to a donor nerve in a rat model of a severed median nerve. METHODS: Three experimental groups were studied: a modified end-to-side neurorrhaphy with suturing of the proximal nerve stump (double end-to-side neurorrhaphy, Group I), a classic end-to-side neurorrhaphy (Group II) and a control group without neurorrhaphy (Group III). Twenty weeks after surgery, grasping testing, muscle contractility testing, and histological studies were performed. RESULTS: The grasping strength, muscle contraction force and nerve fiber count were significantly higher in group I than in group II, and there was no evidence of nerve recovery in group III. CONCLUSIONS: The contribution from the proximal nerve stump in double end-to-side nerve repair might improve axonal sprouting from the donor nerve and help achieve a better functional recovery in an end-to-side coaptation model.

Intramuscular lipoma in thenar or hypothenar muscles.

We report on six patients of intramuscular lipoma of the hand. Four of them occurred in the thenar muscles and two in the hypothenar muscles. The mean age was 49 years (7-68 years). The duration of the lesions prior to excision was averaged as 35 months (12-60 months). Preoperative MRI was taken in all patients, and it was very useful for the diagnosis and differentiation between four well-circumscribed types and two infiltrative types. All operations were performed under loupe magnification. Preoperatively four patients with thenar lipoma had difficulty in moving their thumbs. Two out of four patients with lipomas in the thenar muscles had preoperative intermittent paresthesia and hyperesthesia caused by compression of the radial digital nerve of the thumb. Two patients with lipoma in the hypothenar eminence complained of difficulty with strong grip. The average diameter of the thenar group in its longest dimension was 5.2 cm (3-7 cm), and those of the hypothenar group was 5.5 cm (4-7 cm). At a mean follow-up of 55 months (21-91 months), no tumour had recurred.