Contamination of Heavy Metals in Sediments from an Estuarine Bay, South China: Comparison with Previous Data and Ecological Risk Assessment

Heavy metals and metalloid contamination and risk evaluation in the surface sediment of the Bakkhali River estuary in Bangladesh

Current state of contamination and subsequent risk of contaminated sediment of a tidal river of Bangladesh was evaluated in the present study. Sediment samples were collected from five locations in the tributary of Bakkhali River estuary during summer (April) and winter (December) season, 2020. Collected samples were processed using standard protocol and the content of heavy metals (Cd, Cr, Cu, Pb and Zn) and metalloid (As), were analyzed by the Flame Atomic Absorption Spectrometer. Sediment contamination was evaluated by pollution load index (PLI), contamination factor (CF), degree of contamination (Cd), potential ecological risk index (PERI), non-carcinogenic and carcinogenic risk (CR) due to the dermal contact of the sediment. Multivariate statistical analysis such as principal component analysis (PCA) and cluster analysis (CA) were also applied to find out the possible sources of the contaminant in the sediment. Results showed the average concentration of As, Cd, Cr, Pb, Cu and Zn was 9.74 ± 3.57, 2.00 ± 0.85, 48.75 ± 8.92, 29.78 ± 8.39, 5.44 ± 2.03 and 56.94 ± 8.57 mg/kg, respectively. Concentration of Cu, Pb and Zn were within the recommended level whereas the concentration of As, Cd and Cr were suppressed the recommended level of WHO and FAO/WHO standards. PLI, CF and Cd revealed considerably low degree of contamination of the sediment. Geo-accumulation index indicated uncontaminated to moderately contaminated condition of the sediment. Although the values of enrichment factor revealed no potential enrichment for most of the metals, Cd showed a minor enrichment during the winter season. Based on the ecological risk assessment, the sediment from all of the sample locations was found to be of moderate to low risk. PCA and CA analysis revealed the origin of contaminants mainly from anthropogenic sources. Although different metals showed non-carcinogenic risk to the inhabitants, cancer risk values for dermal contact (CRderm) were much lower than 10-6 indicating no cancer risk for adult and child. However, the findings also revealed that children were more susceptible to CRderm compared to adults. The present study concluded that long term dermal contact of the sediment of Bakkhali River estuary will be contagious to the people. Therefore, regular monitoring of the estuarine environment is necessary so that contamination does not get worse.

Contaminant levels versus toxicity bioassays in ecological risk assessment of sediments from the southern Baltic Sea

Surface sediments collected in 2021 from six locations in the southern Baltic Sea (Polish district) were examined by chemical and toxicological methods. Chemical analyses included polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and their alkylated derivatives, butyltin compounds and 16 major and trace elements. The toxicity was measured using Ostracodtoxkit F and Microtox. The ecological risk of sediment was estimated by hazard quotient (HQ) calculation. Some PAHs, alkylated PAHs and metals (Zn, Hg, Cd and As) could pose a moderate risk in the sediments from the Gdańsk Deep and in the vicinity of the wrecks, but the risk resulting from the presence of all analyzed compounds was considered high for these sediments. In studies using biotests, sediments from the vicinity of the t/s Franken wreck and the Słupsk Furrow were highly toxic to test organisms. Ostracodtoxkit F, compared to Microtox, appeared a more sensitive test for measured compounds.

Heavy Metal Accumulation in Oysters from an Aquaculture Area in the Luoyangjiang River Estuary

Oysters are a group of economically important bivalves in China, with estuaries serving as one of their primary cultivation areas. However, heavy metal pollution in these estuarine environments poses a potential threat to aquaculture by leading to the accumulation of heavy metals in farmed oysters, which could impact their safety and marketability. This study was conducted in the aquaculture area of the Luoyangjiang River estuary, where eight sampling sites were selected. Water, sediment, and oysters categorized by shell length were collected from each site. The concentrations of heavy metals (Ag, As, Cd, Cr, Cu, Ni, Pb, and Zn) were determined in both the environmental samples and oyster tissues. Additionally, multiplex species-specific PCR was used to identify oyster species. The results showed significant variations in dissolved-phase and suspended particulate matter (SPM) metal concentrations across different sampling sites, while sediment metal concentrations were more consistent but similar to those in SPM. The large oysters were comprised of 50% Magallana angulata and 50% Magallana gigas, while small oysters were identified as Magallana sikamea. The Cd, Cu, Pb, and Zn levels in both size groups of oysters exceeded data from previous studies, indicating contamination in the estuary. The observed differences in heavy metal concentrations between large and small oysters primarily reflect species-specific variability in metal accumulation, which may also be influenced by factors such as growth and exposure duration. Furthermore, the lack of significant correlation between metal concentrations in environmental media and oysters suggests that oysters may be exposed to multiple sources of metal contamination.

Ecological and public health risk assessment of potentially toxic elements in the surface sediments of the Pasur river estuary, Bangladesh

Potentially toxic elements (PTEs) in the surface sediments of the Pasur river estuary was investigated to assess its distribution, potential sources, and current dangers to ecological and public health. The Pasur River is a tidal, meandering, perennial river in south-western Bangladesh with a considerable number of fisheries and industrial activities. Sediment samples were collected from seven sampling points from January to December 2022 to assess the contamination level of six potentially toxic elements (Pb, Cr, Cd, As, Cu and Zn). Flame Atomic Absorption Spectrophotometer was utilized to detect the concentration of PTEs by following some sequential analytical procedure. Concentration of PTEs followed the reducing trend of Zn > Cr > Pb > As > Cu > Cd with the mean value of 61.04 > 49.15 > 26.58 > 10.28 > 6.28 > 1.59 mg/kg, respectively. The principle component and cluster analyses justified the anthropogenic source of the studied PTEs. The mean values of contamination factor (CF), geo-accumulation index (Igeo) and enrichment factor (EFc) showed that Pb and Cd were highly responsible for sediment (uncontaminated to moderate) contamination. Pollution load index (PLI) indicated higher pollution of sediments near the port areas. Potential ecological risk index (PERI) indicated low to moderate risks due to the contaminated sediment. However, the contamination of sediment was not associated with the non-carcinogenic (HQderm and HI < 1) and carcinogenic (CRderm < 10-6) risks due to the dermal contact. Although the risks were within the tolerable limit, regular monitoring is suggested to reduce the risk of PTEs contamination.

A first study on the bioaccumulation of trace metals in Rhyssoplax olivacea (Mediterranean Polyplacophora)

This study investigates, for the first time, the bioaccumulation of trace metals in the chiton Rhyssoplax olivacea. Fe, Cu, Co, Cr and Cd were measured in the shell and soft tissue of R. olivacea sampled in five sites along the Algerian west coast during the cold and hot seasons. Physiological and contamination indices were calculated. The condition index provides information on habitat quality and on R. olivacea reproductive performance and physiological status. The metal/shell-weight index informs on the bioavailability of trace metals. The trace element pollution index is used to assign a global contamination status to the studied sites. The trace element spatial variation index ranks Cd and Cr as trace metals of primary environmental concern based on the overall variability of their levels. An exhaustive review compiling data on trace element bioaccumulation in chitons is performed. The potential use of R. olivacea as bioindicator species is discussed.

Advances in Remediation of Contaminated Sites

With the development of the social economy, the population has increased sharply, and the land area involved in people’s production and life is also gradually increasing [...]

Pollution Assessment and SSD-Based Ecological Assessment of Heavy Metals in Multimedia in the Coast of Southeast China

Heavy metals in the ocean exist in various media and assessing heavy metal pollution in the multimedia in seawater is important for proposing effective strategies to protect marine ecosystem health. However, comprehensive coastal pollution assessments and SSD-based assessments of heavy metals have been limited from an international perspective. This study discusses the distribution, sources, interactions, associated environmental factors, and potential ecological risks related to heavy metal pollution. To attain this objective, several tools and models were considered. The partition coefficient between sediment and water was used to understand the ability of heavy metals to be adsorbed from seawater by sediment. The water quality index was applied to evaluate the comprehensive heavy metal pollution at different sampling sites. The species diversity index was calculated by calculating the concentration of chlorophyll a. The geo-accumulation and potential ecological risk indexes were employed for the sediments' general pollution characteristic of heavy metals. Species sensitivity distribution was used for ecological risk evaluation. The results indicated that heavy metal pollution and ecological risk (Cu, Pb, Zn, Cd, As, Cr and Hg) are not serious, and the pollution conditions remain safe. Only Cu, Pb, and Hg concentrations in seawater exceed the Nation Class I Water Quality Standard. The concentrations of heavy metals showed significant spatial characteristics. Fisheries activities and industrial effluent discharges were identified as the main anthropogenic sources. This study provides a comprehensive assessment of heavy metals in multi-media, and the results will provide valuable information for nearshore ecological management and risk avoidance.

Accumulation of Co, Ni, Cu, Zn and Cd in Aboveground Organs of Chinese Winter Jujube from the Yellow River Delta, China

In the present study, winter jujube organs including fruit, fruiting leaf and foliage leaf, and associated soils in 14 typical orchards in Binzhou City, Shandong Province, China were collected and determined for the mass fractions of Co, Ni, Cu, Zn, and Cd. The mass fractions of Co, Ni, Cu, Zn, and Cd in plant tissues generally showed an order of Cu > Zn > Ni > Co > Cd as well as those in the soils decreased as Zn > Cu > Ni > Co > Cd. The values of single factor index and Nemerow pollution index suggested the jujube fruits were not polluted by heavy metals. Values of estimated daily intake for all the elements were far below their associated acceptable reference values, indicating no health risks would be caused by a single trace element. The results of targeted hazard quotient (THQ) of the metals in the fruits decreased as Cu > Ni > Zn > Cd accompanying total THQ (TTHQ) lower than 1 showing no hazard would be caused by those metals. Correlation analysis showed soil might not be the main source of heavy metals in winter jujube organs. Bioaccumulation factors (BAFs) for Co, Ni, Zn and Cd in fruits and leaves were far below 1 suggesting their low bioavailablities. The relatively great BAFs of Cu in the leaves might be due to the application of fertilizers and pesticides containing great amounts of Cu through soil and foliar spraying. To sum up, heavy metals tended not to be a major threat to winter jujube cultivation, and winter jujube had great edible safety.

Heavy Metal Contamination in Sediments from Wetlands Invaded by Spartina alterniflora in the Yellow River Delta

Heavy metals are major pollutants that pose threats to wetland environments. In the present study, surface sediments from wetlands vegetated by invasive species Spartina alterniflora in the Yellow River Delta were collected and determined for the mass fractions of Co, Ni, As, Cd and Pb. Results showed mass fractions of Co, Ni, As, Cd and Pb in the sediments of the S. alterniflora communities ranged from 8.5 to 16.0, 13.9−27.9, 3.2−13.8, 0.08−0.24, and 17.6−37.5 mg/kg dw, respectively, generally presenting an order of Pb > Ni > Co > As > Cd. The levels of heavy metals in sediments in the S. alterniflora communities were higher than those in the wetland vegetated by the native plant species Suaeda heteroptera. Correlations among metal elements were highly significant, suggesting that they might have the same sources. Clay and TOC were important factors affecting the spatial distribution of metals. The Igeo values of the investigated elements in the sediments were frequently lower than 0, revealing the slight pollution status of these metals. Relatively slight values of Eri and RI suggested that the potential ecological risks caused by the 5 metals were low. Our findings could provide a better understanding of the correlation between metal pollution and bio-invasion in wetland ecosystems.

Speciation Distribution and Influencing Factors of Heavy Metals in Rhizosphere Soil of Miscanthus Floridulus in the Tailing Reservoir Area of Dabaoshan Iron Polymetallic Mine in Northern Guangdong

Through field investigation and experimental analysis, the forms, contents and distribution of heavy metals (Zn, Pb, Cu, Cd, Ni, Cr) in rhizosphere and non-rhizosphere soils of Miscanthus floridulus growing everywhere in Tielongwei mine pond (sample plot 1), Caoduikeng tailings pond (sample plot 2), Donghua tailings pond (sample plot 3) and Small tailings pond (sample plot 4) in Dabaoshan, Guangdong Province were studied. The results showed that the main forms and distributions of heavy metals in rhizosphere and non-rhizosphere soils are basically the same, which shows that the mineral content accounts for most of the total amount of heavy metals, while the exchange content is low. Compared with non-rhizosphere soil, the proportion of exchangeable and organic heavy metals in rhizosphere soil increased significantly, in which the proportion of organic-bound Cu increased by 53.25%, the proportion of organic-bound Cd and Pb increased by more than 17%, and the proportion of Zn increased by 5.67%. At the same time, the contents of carbonate-bound and iron manganese oxide-bound decreased. Statistical analyses showed that the morphological distribution of Zn, Pb, Cu, Cd, Ni and Cr in rhizosphere soil was closely related to soil pH value, organic matter content, plant growth and other factors. The results of this study provided a basis for the restoration of heavy metal-contaminated sites by Miscanthus.