Interannual variation and sources identification of heavy metals in seawater near shipping lanes: Evidence from a coral record from the northern South China Sea

Deciphering multi-media occurrence and anthropogenic drivers of potentially toxic elements in a rapidly urbanized estuary: A neural network-enhanced source apportionment

Estuaries and adjacent waters are the most important and vulnerable areas to human activities in coastal seawater, and potentially toxic elements (PTEs) pollution have long received global attention. This study presents a multi-media occurrence to assess the distribution, sources, and ecological risks of PTEs (Cu, Pb, Zn, Cd, Cr, Hg, and As) in the Modaomen Estuary, a rapidly urbanizing coastal zone in southern China. Results revealed that the most abundant elements in seawater, surface sediment, and marine organisms was Zn, while the element with the lowest concentration was Hg. The PTEs in seawater is at a low pollution level according to the comprehensive pollution index (CPI). Sediment analysis highlighted significant enrichment of Cd and Hg, with potential ecological risk index (PERI) identifying these elements as the primary contributors to ecological hazards. Zn in seawater is the most easily enriched element by marine organisms. By integrating advanced Self-organizing maps (SOM) and Positive matrix factorization (PMF) model, we conducted a comprehensive source analysis of PTEs. The SOM-PMF model successfully delineated three major anthropogenic sources-industrial wastewater discharge, fossil fuel combustion, and agricultural activities-accounting for 62.5 % of the total PTEs contributions. This study not only provides a robust framework for understanding PTE dynamics in estuarine environments but also introduces an innovative methodological approach for source apportionment and risk assessment.

Trace elements concentration, tissue distribution, and associated health risks in wild and captive pantropical spotted dolphins (Stenella attenuata)

Trace element (TEs) concentrations are key indicators for evaluating the health status of cetaceans. However, there is currently no research on TEs levels and tissue distributions in captive dolphins. Investigating TEs in wild and captive dolphins could provide critical insights into the effects of diets and habitats on TEs accumulation and improve healthcare protocols for captive dolphins. This study investigated concentrations of six TEs (Hg, Cd, Cr, Se, Cu, and Zn) in seven tissues (skin, muscle, liver, spleen, lung, kidney, and intestine) of wild (n = 8) and captive (n = 6) Stenella attenuata. The findings indicated that most studied wild and captive individuals exhibited medium levels of Hg, Cd, and Cr globally, with low health risks. However, alarming concentrations, such as 306 μg/g Hg in captive individuals and 178 μg/g Cd in wild individuals, suggested localized contamination persists. Tissue distributions of TEs indicated that ingestion and inhalation were the predominant exposure routes for wild and captive dolphins. Additionally, positive correlations between Hg levels in skin and liver and Cd levels in skin and kidney indicated that skin could serve as a healthy indicator for captive dolphins. Consuming odontocete tissue, even from healthy individuals, poses potential health risks to humans.

Impact of multiple-factors on health and infections in marine mussels (Perumytilus purpuratus) inhabiting contaminated sites in the Humboldt Current System

Marine organisms are increasingly exposed to a combination of environmental stressors. However, most studies focus on single factors, limiting our understanding of real-world ecological challenges. This study investigates the combined effects of metal pollution, parasites, pathogens, and environmental variables on the health of Perumytilus purpuratus, a mussel species inhabiting the coast of northern Chile. The upwelling system in this area, combined with low water turnover, creates a unique environment in which to study how multiple factors interact. Mussels were sampled from several sites affected by metal discharges. Analyses revealed that individuals from central and northern sites exhibited the highest levels of parasites, pathogens, and tissue lesions. These health impacts were strongly associated with elevated pH, salinity, cadmium and copper concentrations in the water. Findings emphasise the synergistic effects of chemical and abiotic factors, underscoring the importance of incorporating multiple factors interactions into monitoring programmes. Such an approach can enhance predictions of ecological responses, inform conservation efforts, and guide policies addressing global challenges like aquatic pollution. Our study provides critical insights into how combined factors threaten aquatic ecosystems, offering a framework for more comprehensive environmental assessment.

An Over 30-Year Analysis of Heavy Metal Deposition in Daya Bay Sediments

Sediment cores were collected from the nearshore to bay mouth region in Daya Bay, aiming to describe the historical patterns of heavy metals deposition in the sediment. During the last 40 years, the heavy metals exhibited significant different deposition behaviors in the sediment, in which As, Zn, Cr were more enriched and contributed to metals pollution in this area. Moreover, heavy metals deposition exhibited completely opposite behaviors from the nearshore to bay mouth region. An increasing of pollution level and ecological risk was observed in the nearshore, whereas a decreasing trend was detected in the bay mouth. Principal component analysis suggested that heavy metals were possibly derived from anthropogenic activities in the nearshore, whereas natural sources were the main sources in bay mouth. The results indicated the urgency of implementing efficient measures to mitigate heavy metals contamination in the adjacent sea.

Biomonitoring potential of trace metal accumulation and bioavailability in coral skeletons and reef sediments of Persian Gulf: A comparative study

Nayband Marine National Park in the northern Persian Gulf is an important ecological areas, significantly impacted by industrial activites that poses risk of trace metal pollution to living organisms. In this study, we investigated the bioaccumulation of trace metals in scleractinian corals using annual growth bands and biota-sediment accumulation factor to assess their potential as biomonitoring organisms. Furthermore, to assess the sediment quality, sediment pollution indices and international guidelines was employed. To achieve this, three Faviidae coral and sixteen sediment samples were collected in March 2023 from three sites: an industrial zone (site I), a rural fishing zone (site II), and a marine protected area (site III). In first step, coral samples washed, sun-dried, sliced into 1-cm slabs, X-rayed to reveal annual growth bands, and powder was prepared from each growth band. Then freeze-dried sediments and coral powder were ground, sieved (63 μm), digested (using United States Environmental Protection Agency - Method 3050b) and filtered (Whatman No. 42). Finally, trace metals were analyzed using Inductively Coupled Plasma Mass Spectrometry instrument. The results show severe anthropogenic pollution at sites I and II compared to site III and significant differences between their sampling stations. Mg and Sr concentrations were highest in sediments and corals, respectively, while, Co is lowest in both. According to the sediment pollution indices, Site I showed the highest potential toxicity to biota, followed by Site II and then Site III. The results also suggest that the Faviidae corals are effective bio-indicators for Pb, Li, Cu, and Ni contamination.

Cadmium contamination in sediments from a mangrove wetland: Insights from lead isotopes

Cadmium (Cd) pollution has gained significant attention in mangrove sediments due to its high toxicity and mobility. However, the sources of Cd and the factors influencing its accumulation in these sediments have remained elusive. In this study, we utilized lead (Pb) isotopic signatures for the first time to assess Cd contamination in mangrove sediments from the northern region of the Beibu Gulf. A strong correlation was observed between Cd and Pb concentrations in the mangrove sediments, suggesting a shared source that can be estimated using Pb isotopic signatures. By employing a Bayesian mixing model, we determined that 70.1 ± 8.2 % of Cd originated from natural sources, while 12.9 ± 4.9 %, 9.8 ± 3.7 %, and 7.1 ± 3.4 % were attributed to agricultural activities, non-ferrous metal smelting, and coal combustion, respectively. Our study clearly suggests that natural Cd could also dominate the high Cd content. Agricultural activities were the most important anthropogenic Cd sources, and the increased anthropogenic Cd accumulation in mangrove sediment was related to organic matter. This study introduces a novel approach for assessing Cd contamination in mangrove sediment, providing useful insights into Cd pollution in coastal wetlands.

Assessment of potentially toxic element contamination in commercially harvested invertebrates from the Beibu Gulf, China

Marine pollutants, especially potentially toxic elements (PTEs), increasingly threaten the ecological environment and fishery resources of the Beibu Gulf due to their bioaccumulative nature, toxicity, and persistence. However, the occurrences of multiple PTEs in marine invertebrates within this region remains unclear. Hence, a total of 18 species of commercially harvested invertebrates (shrimp, crab, cephalopod, shellfish, and sea cucumber) were collected from the Beibu Gulf, and the concentrations of nine important PTEs (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were examined. Subsequent stable isotope analysis for δ13C and δ15N facilitated investigations into biomagnification and human health risk assessment. The results showed that, except for As, the concentrations of the PTEs in the invertebrates were below the national safety limits. Furthermore, significant positive correlations were found between trophic levels (TLs) and log-transformed concentrations of As (P < 0.001, R2 = 0.20) and Cr (P < 0.001, R2 = 0.13), indicating biomagnification of these two metals across trophic positions among species. Finally, the human health risk assessment revealed that the consumption of cephalopod, shellfish, and sea cucumber poses a higher risk of adverse effects compared to shrimp and crab.

Spatiotemporal distribution patterns and coupling effects of aquatic environmental factors in the dry-wet season over a decade from the Beibu Gulf, South China Sea

Since the 21st century, the Beibu Gulf area has been affected by increasing anthropogenic activities, which makes the coastal aquatic ecosystem extremely concerning. However, the comprehensive exploration and analysis of the long-term scale behavior change characteristics of various water quality environment factors is still limited. Through comprehensively detecting coastal surface water environmental behavior information from 33 locations in the Beibu Gulf from 2005 to 2015, we revealed and quantified mutual response characteristics and patterns of various environmental indicators. The main environmental pollution indicators (e.g., COD, NH4+, NO3-, and DIP) showed a gradual decrease in concentration from the coast to the offshore sea area, and significantly increases during the wet season. The semi-enclosed Maowei Sea exhibited the most prominent performance with significant differences compared to other regions in Beibu Gulf. The average Chlorophyll-a (Chla) content in the coastal area of the Beibu Gulf during the wet season was more than twice that of the dry season, yet the interaction pattern between Chla and environmental factors in the two seasons was opposite to its concentration behavior, accompanied by a closely significant relationship with thermohaline structure and the input of nitrogen and phosphorous nutrients. The multivariate statistical analysis results of total nutrient dynamics suggested that the Beibu Gulf was clearly divided into different regions in both dry and wet season clusters. The present study can provide a comprehensive perspective for the spatial and temporal migration patterns and transformation laws of coastal water environmental factor, which should contribute to improve the prevention countermeasure of nutrient pollution in coastal environment.

Risk assessment of trace metals and polycyclic aromatic hydrocarbons in seawater of typical bays in the Bohai Sea

The ecological risks of trace metals (Cu, Zn, As, Cd, Pb, and Hg) and PAHs in seawater from three typical bays of the Bohai Sea (the Liaodong Bay, Bohai Bay, and Laizhou Bay) were comprehensively assessed by recompiling 637 sites. Results highlighted that scrutiny should be given to the ecological risks of Cu (3.80 μg/L) in the Bohai Bay and Hg (0.23 μg/L) in the Laizhou Bay. Conversely, the Liaodong Bay exhibited negligible ecological risks related to trace metals. The risks of ΣPAHs in the Liaodong Bay, Bohai Bay, and Laizhou Bay were moderate, with mean concentrations of 368.16 ng/L, 731.93 ng/L, and 187.58 ng/L, respectively. The source allocation of trace metals and PAHs required consideration of spatial variability and anthropogenic factors, which greatly affected the distribution and composition of these pollutants. The combined ecological risks in the Bohai Bay (6.80 %) and Laizhou Bay (5.43 %) deserved more attention.

Anthropogenic influences on the sources and distribution of organic carbon, black carbon, and heavy metals in Daya Bay's surface sediments

The total organic carbon (TOC), total nitrogen (TN), black carbon (BC), δ13CTOC, δ15N, δ13CBC, grain size, and heavy metals of surface sediments collected from Daya Bay were determined to investigate the spatial distributions of these parameters and to evaluate the influences of human activities. Marine organic matter was found to constitute approximately 84.41 ± 7.70 % of these sediments on average. The western and northern regions of Daya Bay exhibited relatively fine grain sizes, weak hydrodynamic conditions, and high sedimentation rates, which favored the burial and preservation of organic matter. The high concentration of organic matter could be attributed to the influence of petroleum and aquaculture industries. Fossil fuels were the main source of BC. The enrichment factor (EF) and geo-accumulation index (Igeo) were used to evaluate the sources and pollution levels of heavy metals. The results revealed that the source and distribution of heavy metals were strongly influenced by human activities, resulting in moderate pollution levels across most regions of Daya Bay. A strong correlation was observed between the Igeo values of heavy metals and BC, TOC, TN, and mean particle grain size (Mz). This suggests that the ability of sediments in Daya Bay to enrich and adsorb heavy metals depends on the sediment grain size, the content and type of organic matter. Importantly, sediments in the inner bay of Daya Bay exhibited a greater capacity to impede the migration of heavy metals compared to those in the outer bay.