Geochemical baseline establishment and pollution assessment of heavy metals in the largest coastal lagoon (Pinqing Lagoon) in China mainland

Potentially toxic elements accumulation in the surface sediment of the Bouregreg estuary, Morocco: Implications for environmental changes and human activities over the last decades

This study investigates the sources, spatiotemporal distribution, contamination levels, and ecological risks of six potentially toxic elements (PTEs) in surface sediments of the Bouregreg Estuary, Morocco, an ecologically significant estuarine system undergoing urbanization and management improvements. The mean PTEs concentrations (mg/kg) were Zn (47.32) > V (30.72) > Pb (17.41) > Cr (14.31) > Cu (9.92) > Cd (1.17). Cd emerged as the most concerning pollutant (up to 2.12 mg/kg), exceeding the background value, showing moderate to strong pollution (Igeo), moderate to very high contamination (CF), and moderate to high ecological risk (ERI). Followed by Pb which showed low to moderate contamination (up to 23.21 mg/kg) according to the CF, correlating with fine, organic-rich sediments near urban areas. Significant seasonal and spatial variations, influenced by anthropogenic pressures and sediment characteristics, were confirmed through principal component analysis and correlation analysis. Historical comparisons indicate an overall improvement in the estuary's ecological health. However, persistent Cd and Pb hotspots emphasize the need for targeted management strategies to safeguard the estuary's ecological integrity and community health.

Emerging environmental risks to the largest coastal lagoon (Pinqing Lagoon) on the Chinese mainland: Assessment through a water-sediment-ecological perspective

Coastal lagoons are vital yet vulnerable marine ecosystems. This study analyzes a five-year dataset to evaluate changes in water quality and their impacts on biota in Pinqing Lagoon (PQL). Seasonal surveys conducted from 2019 to 2023 across 14 sites revealed significant variability in water and sediment quality parameters. During the wet summer season, water quality deteriorated significantly as nutrient levels peaked. In contrast, the dry winter season posed a high ecological risk from heavy metals (HMs), specifically Cu, Hg, and Cd, in sediments. Sediment core analysis indicates upward trends in HMs since the 1950s. Salinity and pH are the primary drivers shaping the benthic communities in transitional zones, while nutrients and HMs primarily affect organisms in the inner bay. Nutrient enrichment has exacerbated HM accumulation and ecological degradation, with tolerance to HMs emerging as a critical factor for benthic survival. This comprehensive assessment of PQL highlights the seasonal patterns of pollution in urban lagoons, providing valuable insights for future conservation efforts.

Environmental protection measures mitigate Pb but not Cd accumulation in soils: Evidence from a 49-year soil chronosequence in an industrial and mining city in Southwest China

To address severe soil Pb and Cd contamination from anthropogenic activities, governments have implemented various environmental management measures. However, the extent to which these measures have constrained Pb and Cd accumulation in industrial and mining city soils remains unclear. Here, we investigated Pb and Cd accumulation patterns in soils of Panzhihua City, Southwest China, and determined their dominant anthropogenic drivers using Pb and Cd isotopes. Pb accumulation initially slowed and then increased, while Cd showed a continuous acceleration. Traffic and coal-burning power generation were the dominant anthropogenic forcings for Pb and Cd accumulation in the soils, respectively. Environmental protection measures, particularly the ban on leaded gasoline, significantly reduced Pb accumulation by decreasing traffic-related Pb contributions to soils from 1980 to 2008. However, environmental management measures could not practically mitigate Cd accumulation in the soils owing to the high Cd content in consumed coal, poor efficiency of air pollutant control measures, and steep rise in coal-burning power generation. This study thus indicates the criticality of controlling Cd emissions from thermal power generation. Additionally, the challenges faced by small industrial and mining cities during economic transformation and environmental policy implementation warrant more attention.

Health risk assessment by consumption of commercial biota contaminated with heavy metals in Tampamachoco coastal lagoon, Gulf of Mexico

Metal pollution is a significant environmental and health problem in aquatic ecosystems worldwide, particularly in coastal systems impacted by emissions from thermoelectric plants, as is the case of the Tampamachoco lagoon. To evaluate the seasonal contamination levels of Cd, Pb, Cr, and Cu in species of commercial interest in the Tampamachoco lagoon and estimate the health risk associated with their consumption, a total of 180 fish, 90 oysters (Crassostrea virginica), 27 crabs (Callinectes sapidus), and 24 shrimp (Litopenaeus setiferus) were sampled. Metal concentrations in the species analyzed were Cu > Pb > Cr > Cd. According to the Target Hazard Quotient and the health risk index, consumption of the marine species examined should be considered safe for human health, as both values are <1. However, Carcinogenic risk values for Pb and Cr indicated that consumers may be at risk of cancer (10-3), due to exposure from the thermoelectric emissions.

Sediment record of heavy metals in Xincun Lagoon indicating anthropogenic impact over the last 200 years

Anthropogenic metal pollution is a leading environmental problem in southern China, especially in remote regions where its impact remains poorly understood. This study investigates the historical variation of heavy metal pollution over the last 200 years using a sediment core from Xincun Lagoon, Hainan Island, South China. The temporal evolution of heavy metal pollution aligns with China's socioeconomic development. Prior to the 1950s, heavy metal concentrations were at geochemical background levels, reflecting China's agrarian status. Since the 1950s, the increased heavy metal accumulation may be attributed to intensified human activities linked to rapid urbanization and industrialization. Despite the increase in heavy metal enrichments since the 1950s, Xincun Lagoon currently faces a low ecological risk.

Geochemical behavior of rare earth elements in agricultural soils along the Syr Darya River within the Aral Sea Basin

The widespread use of rare earth elements (REEs) across various industries makes them a new type of pollutant. Additionally, REEs are powerful indicators of geochemical processes. As one of the two main rivers in the Aral Sea, identifying the geochemical behavior of REEs in agricultural soils of the Syr Darya River is of great significance for subsequent indicative studies. In this study, the geochemical characteristics, influencing factors, and potential application significance of REEs in agricultural soils from three sampling areas along the Syr Darya River were analyzed using soil geography and elemental geochemical analyses. The results showed that the highest total concentration of REEs in the agricultural soil was in Area I, with a mean value of 142.49 μg/g, followed by Area III with a mean value of 124.56 μg/g, and the lowest concentration was in Area II with a mean value of 122.48 μg/g. The agricultural soils in the three regions were enriched in light rare earth elements (LREEs), with mean L/H values of 10.54, 10.13, and 10.24, respectively. The differentiation between light and heavy rare earth elements (HREEs) was also high. The concentration of REEs in agricultural soil along the Syr Darya River was primarily influenced by minerals such as monazite and zircon, rather than human activities (the pollution index of all REEs was less than 1.5). The relationship between Sm and Gd can differentiate soils impacted by agricultural activities from natural background soils. The results of this study can serve as a basis for indicative studies of REEs in Central Asia.

Salinity and pH related microbial nitrogen removal in the largest coastal lagoon of Chinese mainland (Pinqing Lagoon)

Coastal lagoon is critical habitat for human and provides a wide range of ecosystem services. These vital habitats are now threatened by waste discharge and eutrophication. Previous studies suggest that the pollution mitigation of coastal lagoon relies on the water exchange with open sea, and the role of microbial processes inside the lagoon is overlooked. This study takes the Pinqing Lagoon which is the largest coastal lagoon in Chinese mainland as example. The distribution of nutrients, microbial activity of nitrogen removal and community structure of denitrifying bacteria in sediment are analyzed. The results showed that the nutrient in sediment represented by DIN (1.65-12.78 mg kg-1), TOM (0.59-8.72 %) and TN (0.14-1.93 mg g-1) are at high levels and are enriched at the terrestrial impacted zone (TZ). The microbial nitrogen removal is active at 0.27-19.76 μmol N kg-1 h-1 in sediment and denitrification is the dominate pathway taking 51.44-98.71 % of total N removal. The composition of the denitrifying microbial community in marine impacted zone (MZ) is close to that of ocean and estuary, but differs considerably with those of TZ and transition zone (TM). The denitrification activity is mainly controlled by salinity and pH, and the denitrifying bacterial community composition related to the nutrient parameters of TN, TOM, etc. Our study suggested that the distribution of nutrients, microbial activity of nitrogen removal and community structure in Lagoon are the combined effects of terrestrial input and exchange with open sea. The microbial processes play important role in the nitrogen removal of coastal lagoon.

Differentiating environmental scenarios to establish geochemical baseline values for heavy metals in soil: A case study of Hainan Island, China

Soil heavy metal distributions exhibit regional heterogeneity due to the complex characteristics of parent materials and soil formation processes, emphasizing the need for appropriate regional standards prior to assessing soil risks. This study focuses on Hainan Island and employs the Multi-purpose Regional Geochemical Survey dataset to establish heavy metal geochemical baseline and background values for soil using an iterative method. Geographical detector analysis reveals that parent materials are the primary factor influencing heavy metal distribution, followed by soil types and land use. Heavy metal geochemical baseline values are established for the island's three environments and administrative regions. Notably, a universal geochemical baseline value cannot adequately represent regional variations in heavy metal distribution, with parent materials playing a crucial role in various scenarios. Locally applicable values based on parent material are the most representative for Hainan Island. This study provides a reference framework for developing region-specific environmental baseline values for soil heavy metal assessments.

Coastal sediment heavy metal(loid) pollution under multifaceted anthropogenic stress: Insights based on geochemical baselines and source-related risks

Contamination and risk assessments generally ignore the potential bias in results caused by the variation of background values at different spatial scales due to the spatial heterogeneity of sediments. This study aims to perform quantitative source-ecological risk assessment via establishing geochemical baselines values (GBVs) of heavy metal(loid)s (HMs) in Daya Bay, China. Cumulative frequency distribution (CFD) curves determined the GBVs of 12.44 (Cu), 30.88 (Pb), 69.89 (Zn), 0.06 (Cd), 47.85 (Cr), 6.80 (As), and 0.056 mg kg-1 (Hg), which were comparable to the background values of Guangdong Province surface soils, and implied a potential terrestrial origin of the coastal sediments. Principal component analysis (PCA) and positive matrix factorization (PMF) identified three sources (F1: natural processes; F2: anthropogenic impacts; F3: specific sources) with contributions of 51.7%, 29.2%, and 19.1%, respectively. The source-specific risk assessment revealed an ecological risk contribution potential of 73.8% for the mixed anthropogenic sources (F2 + F3) and only 26.2% for natural processes. Cd and Hg were the priority management of metallic elements, occupying 63.5% and 72.5% of the contribution weights of F2 and F3, respectively, which showed multi-level pollution potentials and ecological risk levels. The spatial distribution patterns demonstrated the hotspot features of HM pollution, and priority concerns should be given to the management of marine traffic and industrial point source pollution in Daya Bay. The results of the study provide a scientific approach and perspective for pollution treatment and risk management in the coastal environment.

Metals profile in deep-sea sediment from an active tectonic region around Simeulue Island, Aceh, Indonesia

Simeulue waters are adjacent to the northern part of Sumatra Island, which is undergoing massive land-use transformations; moreover, the waters are located in an active tectonic region. Land changes and tectonic activity might affect the metal pollution profile in this deep sea area. Thus, this study aimed to investigate the vertical profile and assess the sediment quality from the deep-sea marine sediment around Simeulue Island based on metal concentration. Seventy-six bottom sediment samples were collected from eight cores at a water depth of up to 2800 m in the Simeulue waters, Indonesia, in November 2017. Metals Cd, Cu, Fe, Ni, Pb, and Zn were quantified from the cores and multivariate analyses were carried out to understand the process. Metals distributions are analogous to the grain size parameters and LOI₅₅₀ distribution pattern, while Sumatra and Simeulue islands influenced grain size and LOI₅₅₀ spatial distribution. The vertical grain size profile exhibited no extreme oscillation in the investigated cores. Thus, sediment transport from the Island was the main suspect for these metals' profiles in the deep water, and the tectonic activity had a minor impact. Cu, Ni, Pb, and Zn tend to rise in the collected cores, suggesting that the accumulation of the metals is growing. While Fe tended to be stable and Cd oscillated in the cores. Indices were computed to assess the metal contamination profile. The cores were dominated by EF class 1 (none to slight enrichment) status and I_geo class 1 (unpolluted). Cd was the metal of concern in the study since a high Cd was observed in some layers (maximum EF = 26.45 and maximum I_geo = 3.81). Thus, this study can be used as a database to improve the regulation formulation for improved environmental managerial efforts in the region.