Pollution characteristics and ecological risk of heavy metals in ballast tank sediment

Spatial Distribution, Ecological and Human Health Risks of Potentially Toxic Elements (PTEs) in River Ravi, Pakistan: A Comprehensive Study

Significant quantities of potentially toxic elements have been and are still being discharged into Pakistan's rivers through natural sources and anthropogenic activities. The present study provides a comprehensive study of potentially toxic element contamination in the water and sediment of the Ravi River, Pakistan. The research aims to examine the extent of pollution, its ecological risks, and the potential human health impacts through detailed geospatial analysis and statistical correlation. Water and sediment representative samples were taken and analyzed for potentially toxic elements, including Cobalt (Co), Cadmium (Cd), Zinc (Zn), Nickel (Ni), Arsenic (As), Chromium (Cr), Lead (Pb), Copper (Cu), and Manganese (Mn). Various pollution indices, such as the "Geo-accumulation Index (Igeo), Modified degree of Contamination (mCd), Nemerow comprehensive pollution index (Pt), Contamination factor (CF), Enrichment factor (EF), Pollution Load Index (PLI), and Potential Ecological Risk Index (PERI)," were calculated to determine the contamination levels and ecological risks. The results indicated significant spatial variability in metal concentrations, with higher levels observed in industrial and urban areas (near Lahore). Cd and As were identified as the most critical pollutants, exhibiting high Igeo, CF, EF, and PERI values. The PLI revealed that several regions along the river are heavily polluted. Pt shows high comprehensive pollution near Lahore and moderate to high pollution in surrounding areas. According to mCd, most of the study area, especially sampling points near Lahore, ranges between 8 and 16, indicating a high degree of pollution. The Human Health Risk (HHR) assessment, considering ingestion, inhalation, and dermal contact pathways, highlighted that children are particularly vulnerable, showing higher Hazard Quotient (HQ) and Hazard Index (HI) values for several metals. Correlation analysis revealed significant relationships between certain metals, suggesting common sources of contamination, likely from industrial discharges and urban runoff. The comprehensive mapping and statistical analysis underscore the urgent need for implementing effective pollution control measures to mitigate the risks posed by potentially toxic element contamination in the Ravi River. This study provides critical insights for policymakers and environmental managers to prioritize areas for remediation and to develop strategies to protect both ecological and human health in the region.

Comparison of heavy metal pollution and ecological risk assessment in ballast tank sediments based on two applicable reference standards

The potential risks of ballast tank sediments have garnered global attention. This study collected sediment samples from ballast tanks of four transoceanic ships and determined 27 metal(loid) s by GB 5085.6-2007 and 9 metal(loid)s by GB 18668-2002. The pollution characteristics and ecological risk assessment of 8 typical heavy metals measured by both standards were analyzed and compared. Concentrations of Cd, Zn, and As were found to be high in the ballast tank sediments, and attention should also be directed toward Sn and Mn, which were rarely studied in ballast tank sediments. The concentration of Ni had significant differences between the two standards (P < 0.05). The results of ecological risk methods indicate that Cd, Zn, and As pose significant ecological risks. GB 5085.6-2007 demonstrated sensitivity in reflecting the ecological risks of heavy metals. Overall, this study provides valuable insights into establishing a unified standard for heavy metals for future ballast tank sediment management.

Assessment of heavy metals contamination of sediments and surface waters of Bitter lake, Suez Canal, Egypt: Ecological risks and human health

The concentrations of heavy metals in the surface waters and sediments of Bitter Lake were investigated to assess the level, distribution, and source of pollution and the associated ecological and human health risks. The ecological indices of the lake water indicate low contamination degrees by heavy metals. A dermal exposure-based health risk evaluation revealed no carcinogenic or non-carcinogenic impact on human health. The contamination factor (CF) for Cu, Ni, Pb, Mn, Fe, and Zn (CF < 1) indicate low contamination levels, while Cd reaches very high contamination in most sediment sites (CF ranges from 6.2 to 72.4). Furthermore, the potential ecological risk factor (Erⁱ) and modified hazard quotient (mHQ) indicate low ecological risk for all metals except Cd, revealing high to very high-level ecological risk in most sites (Erⁱ ranges from 185 to 2173 and mHQ from 1.8 to 6.3). This emphasizes the urgency of prompt actions to improve the environment in Bitter Lake.

Deciphering the characterization, ecological function and assembly processes of bacterial communities in ship ballast water and sediments

Various microorganisms are transported worldwide via the water and sediments inside ship ballast tanks. Nevertheless, the ecological functions and assembly processes of bacterial communities in ballast water and sediments remain poorly understood. Here, we investigated the bacterial composition, community assembly processes, and putative functions through analyses of 70 ballast water and sediment samples obtained from various ships. The results showed that the ballast sediments contained a higher diversity of bacterial communities, whereas the ballast water was characterized by the dominance of Proteobacteria. Both the composition and potential function structures of bacterial communities were clearly different between the ballast water and sediment samples. The ballast water exhibited an abundance of microorganisms that involved in sulfur oxidation, whereas the bacterial species associated with nitrogen metabolism were abundant in the sediments. Co-occurrence network analysis revealed that the communities in ballast sediment samples possessed more complex network structures with higher modularity and positive associations among bacterial populations. Stochastic processes, especially the dispersal limitation process played the most important influence in the assembly of the communities in ballast water. Meanwhile, the bacterial communities in the ballast sediments were primarily governed by the homogeneous selection of determinacy. The results from this study will help us understand the ecological processes related to the bacterial communities in the ballast tanks and provide a foundation for the management of ballast water and sediments.

Modelling spatial dispersion of contaminants from shipping lanes in the Baltic Sea

Major sources of pollution from shipping to marine environments are antifouling paint residues and discharges of bilge, black, grey and ballast water and scrubber discharge water. The dispersion of copper, zinc, naphthalene, pyrene, and dibromochloromethane have been studied using the Ship Traffic Emission Assessment Model, the General Estuarine Transport Model, and the Eulerian tracer transport model in the Baltic Sea in 2012. Annual loads of the contaminants ranged from 10^-2 tons for pyrene to 100 s of tons for copper. The dispersion of the contaminants is determined by the surface kinetic energy and vertical stratification at the location of the discharge. The elevated concentration of the contaminants at the surface persists for about two-days and the contaminants are dispersed over the spatial scale of 10-60 km. The Danish Sounds, the southwestern Baltic Sea and the Gulf of Finland are under the heaviest pressure of shipborne contaminants in the Baltic Sea.

Application of a behavioural and biochemical endpoint in ecotoxicity testing with Exaiptasia pallida

Exaiptasia pallida has been applied as a cnidarian model to assess the toxicity of various contaminants using endpoints related to growth, reproduction and mortality. However, increasingly accepted behavioural and biochemical endpoints are underrepresented in ecotoxicity testing with cnidarian species. The aim of this study was to assess the suitability of tentacle retraction and superoxide dismutase activity as behavioural and biochemical endpoints for ecotoxicity testing with E. pallida. A concentration-dependent, tentacle retraction response was found in sub-lethal toxicity testing for anemones exposed to 1-65 μg L^-1 Cu and 2-630 μg L^-1 Zn for 24 and 96 h. Semi-quantitative and quantitative approaches to tentacle retraction analysis showed a difference in response sensitivity, however, both methods resulted in similar 24- and 96-h EC50 values for Cu and Zn. Additionally, tentacle retraction analysis provided the benefit of identifying recovery in anemones previously exposed to 359 μg L^-1 Zn following a 96-h recovery period. Conversely, no significant difference in superoxide dismutase activity was detected in anemones exposed to the Cu and Zn solutions compared with controls, after either 24- or 96-h exposures. These findings support the ease of application and sensitivity of tentacle retraction as an endpoint in ecotoxicity testing with E. pallida and recommend its suitability for use in acute, sub-lethal toxicity testing. Moreover, evidence of recovery in E. pallida following exposure suggests that recovery should be incorporated into future toxicity assessments.

Investigation of heavy metals in the ballast water of ship tanks after and before the implementation of the ballast water convention: Bushehr Port, Persian Gulf

In this study, the amount of heavy metals such as Ni, Cd, Pb and Cu and some physiochemical factors including pH, temperature and total organic carbon (TOC) in the ballast water of the ships entering the Bushehr Port were measured for two years (cold and hot seasons) before and after the ballast water convention was enforced. The mean concentrations of Ni, Cd, Pb and Cu, before and after implementation of the convention were 46.55, 3.93, 5.36, 58.83 and 26.41, 2.12, 2.59, 23.54 ppb. It became clear that the concentrations of heavy metals after the implementation of the convention was lower in comparison and there was a significant difference (p < .05). It seems that continuous monitoring of the quality of the ballast water and determination of locations free of pollution and contamination in the Persian Gulf are necessary for ships that intend to exchange their ballast water in this Gulf.

Time-response characteristic and potential biomarker identification of heavy metal induced toxicity in zebrafish

The present work aims to explore the time-response (from 24 h to 96 h) characteristic and identify early potential sensitive biomarkers of copper (Cu) (as copper chloride dihydrate), cadmium (Cd) (as cadmium acetate), lead (Pb) (as lead nitrate) and chromium (Cr) (as potassium dichromate) exposure in adult zebrafish, focusing on reactive oxygen species (ROS), SOD activity, lipid peroxidation and gene expression related to oxidative stress and inflammatory response. Furthermore, the survival rate decreased apparently by a concentration-dependent manner after Cu, Cr, Cd and Pb exposure, and we selected non-lethal concentrations 0.05 mg/L for Cu, 15 mg/L for Cr, 3 mg/L for Cd and 93.75μg/L for Pb to test the effect on the following biological indicators. Under non-lethal concentration, the four heavy metals have no apparent histological change in adult zebrafish gills. Similar trends in ROS production, MDA level and SOD activity were up-regulated by the four heavy metals, while MDA level responded more sensitive to Pb by time-dependent manner than the other three heavy metals. In addition, mRNA levels related to antioxidant system (SOD1, SOD2 and Nrf2) were up-regulated by non-lethal concentration Cu, Cr, Cd and Pb exposure. MDA level and SOD1 gene have a more delayed response to heavy metals. Genes related to immunotoxicity were increased significantly after heavy metals exposure at non-lethal concentrations. TNF-α and IL-1β gene have similar sensibility to the four heavy metals, while IL-8 gene was more responsive to Cr, Cd and Pb exposure at 48 h groups and IFN-γ gene showed more sensitivity to Cu at 48 h groups than the other heavy metals. In conclusion, the present works have suggested that the IFN-γ gene may applied as early sensitive biomarker to identify Cu-induced toxicity, while MDA content and IL-8 gene may use as early sensitive biomarkers for evaluating the risk of Pb exposure. Moreover, IL-8 and IFN-γ gene were more responsive to heavy metals, which may become early sensitive and potential biomarkers for evaluating inflammatory response induced by heavy metals. This work reinforces the concept of the usefulness of gene expression assays in the evaluation of chemicals effects and helps to establish a background data as well as contributes to evaluate early environmental risk for chemicals, even predicting toxicity.

Composition and influencing factors of bacterial communities in ballast tank sediments: Implications for ballast water and sediment management

This study aims to reveal the composition and influencing factors of bacterial communities in ballast tank sediments. Nine samples were collected and their 16S rRNA gene sequences were analyzed by high-throughput sequencing. The analysis results showed the Shannon index in ballast tank sediments was in the range of 5.27-6.35, which was significantly higher than that in ballast water. Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi and Proteobacteria were the dominant phyla and accounted for approximately 80% of all 16S rRNA gene sequences of the samples. Besides, the high contents of sulfate reducing bacteria (SRB) and sulfur oxidizing bacteria were detected in sediments, indicating that the corrosion of metal caused by SRB might occur in ballast tank. In addition, the trace of human fecal bacteria and candidate pathogens were also detected in ballast tank sediments, and these undesirable microbes reduced the effect of ballast water exchange. Furthermore, C and N had significant effects on the bacterial community composition in ballast tank sediments. In conclusion, our findings suggest that the proper management and disposal of the ballast tank sediments should be considered in order to reduce the negative impact and ecological risks related to ballast water and sediments.

Sensitive biomarkers identification for differentiating Cd and Pb induced toxicity on zebrafish embryos

Cadmium (Cd) and lead (Pb) are naturally existing heavy metals that pose significant health risks. The present study aims to identify sensitive biomarkers for differentiating the toxicities induced by Cd and Pb and for providing clues for the early prediction of toxicity and environmental risk assessment. Indicators related to oxidative stress and inflammatory responses in zebrafish treated with Cd and Pb over time (from 24hpf to 96hpf) were compared. Furthermore, endpoints such as embryo lethality and teratogenicity were detected. Then, several related genes involved in oxidative stress and inflammatory responses characterizing both Cd and Pb exposure, along with key molecules in the MAPKs pathway, were compared at the mRNA level, allowing the selection of the most sensitive and informative biomarkers. Significant increases in reactive oxygen species (ROS) production were observed in zebrafish exposed to Cd and Pb. Cd and Pb exposure induced developmental toxicity, influencing survival rate, hatching rate, larval growth, and heart rate and causing abnormal embryonic development. Similar trends in SOD1 and SOD2 gene expression were induced by Cd and Pb, while nuclear factor erythroid-2 related factor 2 (Nrf2) gene expression responded differently to each metal. In addition, Cd and Pb induced a delayed activation of the CAT and HO-1 genes, with no apparent change in the 24hpf and 48hpf groups. Genes related to immunotoxicity were activated significantly in a time-dependent manner, and these genes exhibited different sensitivities to Cd and Pb. MAPKs pathway genes were also activated in a time-dependent manner, and the expression of these genes showed different effects under Cd and Pb treatment. In summary, the present works have identified some potential sensitive biomarkers. The Nrf2 gene is a potential biomarker to differentiate Pb-induced toxicity from that of Cd, and the IFN-γ gene may be used as a sensitive biomarker for evaluating the risk of Pb contamination. We found that the timeline of MAPKs pathway activation helped to differentiate these two metals toxicities. Furthermore, Pb induced the early activation of ERK2/3 and JNK1, while p38 MAPKs showed delayed activation with no apparent change in the 24hpf group. Cd induced an early activation of ERK2 and a delayed activation of p38a, p38b, ERK3 and JNK1, indicating that the JNK1 pathway is sensitive to Pb exposure, while the p38 pathway may be susceptible to Cd. This work contributes to sensitive biomarker identification and early environmental risk evaluation for chemicals as well as toxicity prediction.