Trace metals in sediments and benthic animals from aquaculture ponds near a mangrove wetland in Southern China

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.

Mangrove forest health condition from space and the use of in situ data

Remote sensing (RS) is a widely used technology for monitoring mangrove forests, but there are some inconsistencies in their capacity to assess mangrove ecosystem health status. Our review aims to investigate how RS and in situ data are being applied together in assessments of mangrove forest health conditions. Our results showed that commonly the concept of mangrove ecosystem health was not defined and indicators that were not clearly related to it were applied. Furthermore, low to medium spatial resolution satellites were more used to detect changes in the mangrove forests' environmental condition than the high spatial resolution ones, and the use of RS with data collected in situ was present in only 39% of the articles. We concluded that studies consider vegetation indexes the same as vigor, so the mangrove ecosystem health; and vigor as the only indicator needed, not using in situ data to validate the mangrove health status.

Comprehensive evaluation of the distribution, transport and ecological risk of heavy metals in intra-urban river sediments using high-resolution techniques

Determining the distribution trends, transport mechanisms, and ecological risks of heavy metals (HMs) in urban river sediments is essential for the government to conduct appropriate remediation work. In this study, we collected sediment cores from the Yayao Waterway in Foshan City, China. The vertical distribution profiles of dissolved and labile Fe, Mn, Cd, Zn, Cu, Cr, Ni, Pb, As, and Co in the sediments were obtained using the thin-film diffusive gradient (DGT) and high-resolution peeper (HR-Peeper) techniques. In addition, the transport rates, contamination levels, and ecological concerns of the HMs were evaluated using the European Community Bureau of Reference (BCR) sequential extraction technique, the DGT-induced sediment fluxes (DIFS) model, and multiple contamination evaluation metrics. The results showed that most of the DGT-labile HMs were associated with Fe/Mn (hydrogen) oxides, and in particular, Zn, Ni, and Cr showed a significant negative correlation with Fe/Mn (p < 0.001). Additionally, Cd had the highest bioavailability (89.17%), and its net diffusive flux at the sediment-water interface (SWI) was positive, which indicated a high release risk from the sediment. However, the R-value of Cd based on the DGT-induced sediment fluxes (DIFS) operation was extremely low, suggesting that although Cd had the biggest supply pool of releases, its release rate was slow. The majority of sampling sites had significantly higher total HM contents in the surface sediments than the background values. The HM contamination in the sediments originated from human activities, primarily from industrial enterprises and with a large contribution from both agricultural and domestic sources. The most polluted HM with the highest ecological danger was Cd, followed by Cu, Zn, Ni, and As when the results of the four pollution evaluation indicators were combined. Consequently, the risk of contamination by HMs in inner-city river sediments should receive more attention.

Assessing heavy metal pollution in sediments from the northern margin of Chinese mangrove areas: Sources, ecological risks, and health impacts

With the rapid economic development of coastal cities, the discharge of substantial amounts of heavy metal pollutants poses a serious hazard to mangroves; however, the potential sources of heavy metals and the resulting health risks are not fully understood. In this study, we analyzed the contents, sources, and ecological and health risks of heavy metal contamination in mangrove sediments from the northern margin of China. The accumulation of heavy metals in mangroves was primarily driven by five potential sources, namely agricultural (33.5 %), natural sources (21.3 %), industrial (19.1 %), aquaculture (14.3 %), and traffic (11.8 %). The assessment of health risks using a probabilistic approach demonstrated that noncarcinogenic risks were within acceptable limits for all populations. It was worth noting that both noncarcinogenic and carcinogenic risks were greater in children than in adults. Analysis of source-oriented health risks revealed that agricultural sources and As and Cd were priority sources and elements of pollution requiring attention.

Sedimentary records of environmental evolution in Dongzhai Port mangrove swamps (South China) over the last hundred years: Insights from corrections of grain-size effects

Mangrove sediments play a vital role in the biogeochemical processes of elements by behaving as both sources and/or sink for nutrients and trace metals. Under the combined impacts of grain-size effects and human activities, it is difficult to accurately assess the sources and degree of pollutants. For this purpose, two cores were collected from a mangrove swamps of Dongzhai Port (South China) and analyzed for temporal distributions of grain size, nutrients, major and trace elements, and 210Pb activities. Due to the significant vertical variation of grain size with depth, linear regression analysis was conducted based on trace metals (i.e., Pb, Cr, Ni, Cu, Cd, Zn) and normalized element Al to reconstruct local environmental background. The results showed that the contents of Cu, Cd, and Zn in the surface layers exhibited significantly increasing trends since the 1980s, with maximum contents of 9.06, 0.16, and 228.66 μg g-1, and their enrichment factors up to 1.52, 1.40, and 1.50, respectively. It should be attributed to shrimp farming and domestic sewage, indicating slight anthropogenic inputs. The evolution process was divided into three stages in Dongzhai Port over the last 100 years: before 1980 AD, 1980-2000 AD, and from 2000 AD to the present, corresponding to the stages of natural deposition, domestic pollution, and aquaculture pollution, respectively.

Does mangrove leave falling dominate the bury of polycyclic aromatic hydrocarbons in the mangrove of China?

Mangrove wetlands are vital coastal ecosystems that can absorb and accumulate pollutants. Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that pose potential risks to ecosystems and human health. However, their source and transport fate in mangrove areas are poorly understood. This study investigates 29 PAHs pollution of water and sediment in Zhangjiangkou Mangrove Wetland, the northernmost large-scale mangrove wetland reserve in China. We examine the distribution, source, transport mechanisms and risk assessment of PAHs. The results show that the concentrations of PAHs in mangrove sediment range from 55.62 to 347.36 ng/g (DW), with 5-ring PAHs being the dominant species. While the concentrations of PAHs in surface water range from 10.61 to 46.39 ng/L, with 2-ring PAHs and alkylated PAHs being the dominant species. The PAHs concentrations in surface water and sediment of river are higher than those in mangrove area, indicating that mangrove water could receive PAHs through tidal exchange. Based on diagnostic ratios (DRs), principal component analysis (PCA), and positive matrix factorization (PMF), we infer that the leaf deposition (48.55%) could be an important pathway of PAHs in mangrove sediment except for river water transport (51.45%), while the PAHs in estuary water originate mainly from point sources such as biomass burning (50.96%) and traffic emission (49.04%). The range of toxic equivalents in surface water and sediment was 2.73-16.09 ng TEQ g-1 and 0.03-3.63 ng/L, respectively. Although the ecological risk assessment suggests that the PAHs pollution in surface water and sediment poses a low risk, we recommend more attention to the protection of the mangrove ecosystem. This study reveals that mangrove leaf falling might be a significant mechanism of PAH sequestration in the mangrove system, which deserves more attention in future research.

Potentially toxic element bioaccumulation in consumed indoor shrimp farming associated with diet, water and sediment levels

Shrimp production is an important industry for many countries and shrimp consumption is increasing worldwide. Shrimps are a highly nutritional food, but can pose a risk for human health if subject to high levels of environmental contaminants. This work studies the presence of As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn in shrimps from Ecuador and compares them to such contents noted in other shrimp-production areas in the world to evaluate the possible risks associated with these elements for consumer health, and to relate them to potentially toxic element (PTE) contents in water, sediments and diets, and also to animal biometric parameters. The PTE levels (mg kg-1 DM) obtained are as follows: in the head-As (3.52-6.11), Cd (0.02-0.10), Co (0.14-0.49) Cr (0.23-4.89), Cu (99.9--233.0), Ni (0.52-1.86), Pb (0.24-1.09), Zn (51.8-100.5) and Hg (μg kg-1 DM) (10.00-66.81); in the tail-(0.91-3.21), Cd (0.01-0.02), Co (0.01-0.43) Cr (0.01-6.52), Cu (20.0-72.44), Ni (0.15-2.03), Pb (0.01-0.69), Zn (31.2-66.1) and Hg (μg kg-1 DM) (10.00-67.18). The concentration of all the PTEs is generally lower than the limits set for seafood by European regulations, except for As in the cephalothorax (4.63 mg kg-1). Different behaviours for PTE accumulation in shrimps were found, which preferentially tend to accumulate in the cephalothorax, except for Hg (40.13 μg kg-1 DM), which accumulates in muscle (body) and is associated with contents of proteins, lipids and total shrimp weight. Nonetheless, the target hazard quotient (THQ) values for PTEs indicate that the consumption of shrimp muscles from Ecuador does not pose a human health risk because the values of these indices are below 1 in all cases.

Contamination in mangrove ecosystems: A synthesis of literature reviews across multiple contaminant categories

Mangrove forests are exposed to diverse ocean-sourced and land-based contaminants, yet mangrove contamination research lags. We synthesize existing data and identify major gaps in research on five classes of mangrove contaminants: trace metals, persistent organic pollutants, polycyclic aromatic hydrocarbons, microplastics, and pharmaceuticals and personal care products. Research is concentrated in Asia, neglected in Africa and the Americas; higher concentrations are correlated with waste water treatment plants, industry, and urbanized landscapes. Trace metals and polycyclic aromatic hydrocarbons, frequently at concentrations below regulatory thresholds, may bioconcentrate in fauna, whereas persistent organic pollutants were at levels potentially harmful to biota through short- or long-term exposure. Microplastics were at variable levels, yet lack regulatory and ecotoxicological thresholds. Pharmaceuticals and personal care products received minimal research despite biological activity at small concentrations. Given potential synergistic effects, multi-contaminant research, increased monitoring of multiple contaminant classes, and increased public outreach and involvement are needed.

Occurrence and Distribution of Tetrabromobisphenol A and Diversity of Microbial Community Structure in the Sediments of Mangrove

The occurrence and distribution characteristics of tetrabromobisphenol A (TBBPA) and its relationship with microbial community diversity in different mangrove sediments need further investigation. The results of this study indicated levels of TBBPA in mangrove sediments from the Zhangjiang Estuary (ZJ), Jiulongjiang Estuary (JLJ), and Quanzhou Bay (QZ) in Southeast China ranging from 1.80 to 20.46, 3.47 to 40.77, and 2.37 to 19.83 ng/g dry weight (dw), respectively. Mangrove sediments from JLJ contained higher levels of TBBPA, possibly due to agricultural pollution. A correlation analysis revealed a significant correlation between total organic carbon (TOC), total nitrogen (TN), and TBBPA distribution in ZJ and JLJ mangrove sediments, but not in QZ mangrove sediments. TOC significantly affected the distribution of TBBPA in mangrove sediments, but pH had no effect. High-throughput 16S rRNA gene sequencing showed that Pseudomonadota dominated the sediment bacteria followed by Chloroflexota, Actinobacteota, Bacillota, Acidobacteriota, Bacteroidota, and Aminicenantes in mangrove sediments. Although the microbial community structure of the ZJ, JLJ, and QZ mangrove sediments was similar, the taxonomic profile of their sensitive responders differed markedly. The genus Anaerolinea was dominant in the mangrove sediments and was responsible for the in situ dissipation of TBBPA. Based on redundancy analysis, there was a correlation between TBBPA, TOC, TN, C/N, pH, and microbial community structure at the genus level. Combining TBBPA, TN, and TOC may induce variations in the microbial community of mangrove sediments.

Dynamics of heavy metals during the development and decomposition of leaves of Avicennia marina and Kandelia obovata in a subtropical mangrove swamp

In mangrove wetlands, leaves make up a high proportion of the plant biomass and can accumulate heavy metals from contaminated sediment. Despite this, it is still unclear how heavy metal concentrations in leaves change as they develop and how metals in senescence leaves are recycled back into the mangrove ecosystems during decomposition. The present study aims to investigate the dynamics of six heavy metals (Cu, Zn, Cr, Ni, Cd, and Pb) in leaves of two common mangrove plants, Avicennia marina and Kandelia obovata, at different stages of development (young, mature, and senescent) and leaf litter decomposition (from 0 to 20 weeks). Based on litterbag experiments in a subtropical mangrove swamp, both plant species showed similar trends in alternations of the six heavy metals during leaf development, that was, decreased in Cu and Zn but increased in Pb, while Cr, Ni, and Cd remained steady. All heavy metals in litter gradually increased in concentration during decomposition. By the end of the 20-weeks decomposition, the concentrations of Cu, Zn, and Cd in decayed leaves were comparable to those in sediment, with Cu, Zn, and Cd at approximately 18, 75, and 0.2 mg·kg^-1, respectively, while Cr (66 mg·kg^-1), Ni (65 mg·kg^-1), and Pb (55 mg·kg^-1) were lower than those in sediment, indicating that metals were not retained in litter but recycled back to the sediment. Tannins in mangrove leaf litter might chelate heavy metals, affecting their migration and transformation of heavy metals in estuarine mangrove wetlands. The findings of our study provide insight into the interactions between toxic heavy metals and mangrove plant species during leaf development, representing the first example of how most metals would be retained in leaf litter during decomposition, thereby reducing their release to estuarine and marine ecosystems.

Distribution, Risk Assessment and Source of Heavy Metals in Mangrove Wetland Sediments of Dongzhai Harbor, South China

Heavy metals are common environmental contaminants that are toxic, non-biodegradable, and bioaccumulative. They can bioaccumulate through the food chain and present a risk to both public health and ecology. Therefore, this study takes the mangrove wetland of Dongzhai Harbor as an example. The concentrations of heavy metals such as As, Cd, Cr, Cu, Ni, Pb, and Zn in the surface sediments of mangrove wetlands were measured to reveal their distribution, the contamination level was assessed, and the sources of contamination were analyzed. The distribution of Cr, Zn, Ni, Pb, Cu, and Cd concentrations are: Yanfeng East River > Sanjiang River > Yanzhou River > Yanfeng West River, while the As concentration in the Yanfeng West River is greater than that in the Yanfeng East River. According to the correlation analysis, the concentrations of Cr, Zn, Ni, Cu, and Cd are significantly and positively correlated with total organic carbon (TOC), total phosphorus (TP), total nitrogen (TN), and salinity (SAL) and shared a significantly negative correlation with pH. There is moderate contamination risk of As and slight contamination risk of Cd, Cr, Cu, Ni, Pb, and Zn in most regions within the study area. Cd, Cr, Cu, Ni, Pb, and Zn exhibit the same sources, which are mainly influenced by human sources such as aquaculture, agricultural cultivation, and livestock farming, while the source of As comes from aquaculture.

Effects of land use on the heavy metal pollution in mangrove sediments: Study on a whole island scale in Hainan, China

In recent decades, mangrove ecosystems at coastal zone are experiencing rapid land-use conversion, however effects of land use on the heavy metal pollution in mangrove sediments still are not clear. This study investigated the concentration and distribution of heavy metals (including chromium (Cr), zinc (Zn), lead (Pb), copper (Cu), arsenic (As) and cadmium (Cd)) in different mangrove sediments with different land-use patterns along seashore of the whole Hainan island (with the third largest mangrove area of China). The effects of land use on the accumulation of heavy metals in these mangrove sediments are also analyzed. The results showed contaminations of ∑6Metals in this study following the order of arable lands (ARAB) > aquaculture ponds (AQUA) > riverine area (RIVER) > ecological area (ECOL) > construction area (CONS). Accumulation degree of As and Cd were high in the AQUA, ARAB, and RIVER area. As metal hotspots, ARAB, RIVER and AQUA area showed the deteriorated sediment quality with high pollution load index (>1). Redundancy discriminate analysis revealed that mangrove, paddy lands and aquaculture ponds related activities correlated well with the metal pollution. The results clearly revealed that different land uses would not only change the accumulation capacity of mangrove soil for heavy metals, but also contribute different sources of heavy metal pollution. These findings do help to facilitate land-use planning and contribute to guide a better mangrove wetland management at coastal zone.

Risk assessment of heavy metals in a typical mangrove ecosystem - A case study of Shankou Mangrove National Natural Reserve, southern China

Mangroves bear enormous ecosystem value, while the ecosystems are facing increasing environmental pressures. In this study, 73 samples of soil sediments in mangroves, paddy fields, grasslands, forests, and shrimp ponds were collected from Shankou Mangrove National Nature Reserve (SKMNNR), Guangxi Zhuang Autonomous Region, China. The pollution status and ecological risks of heavy metal elements of Cr, Ni, Cu, Zn, As, Cd, Pb, V, and Co were determined using the enrichment factor (EF), geoaccumulaton index (I_geo), and potential ecological risk index (PERI). The average concentration is shown to be substantially lower than the background value. In general, the I_geo values indicated that the pollution conditions of different land use types in SKMNNR are relatively minor. Most of the PERI values were at the moderate level. This study demonstrates that the current status of sediment quality in SKMNNR is relatively good, and the pollution level is relatively low. Large-scale coastal aquaculture development and industrial expansion should not no longer be permitted there.

Geospatial modeling and ecological and human health risk assessments of heavy metals in contaminated mangrove soils

Heavy metal-contaminated wastes can threaten mangrove forests, one of the most biodiverse ecosystems in the world. The study evaluated the geospatial distribution of heavy metals concentrations in soils, the ecological and human health risks, and metal contents in soil fractions and mangrove organisms in the Botafogo estuary, Brazil, one of the most environmentally impacted estuaries in the country. The metal concentrations exceeded by up to 2.6-fold the geochemical background; 91%, 59%, 64%, 31%, and 82% of the soils were contaminated with Cr, Zn, Pb, Cu, and Ni, respectively. Adverse effects to the biota may occur due to Cr, Cu, Ni and Pb exposures. Contents of clay and organic matter were the main factors governing the distribution of metals in soil, contributing to up to 63% of the total variability. However, the geospatial modeling showed that the predictive ability of these variables varied spatially with the metal and location. The ecological and human health risks assessments indicated that the metal concentrations in soils are safe for the environment and human beings. There was a low transfer of metals from the soil to the biota, with values of sediment-biota accumulation factor (SBAF) and biological accumulation coefficients (BAC) lower than 1.0, except for Zn (SBAF = 13.1). The high Zn bioaccumulation by Crassostrea rhizophorae may be associated with the concentrations of Zn in the bioavailable fractions.

Potential and mechanism of glomalin-related soil protein on metal sequestration in mangrove wetlands affected by aquaculture effluents

Aquaculture effluent discharge containing heavy metals affects estuarine mangrove wetlands. Glomalin-related soil protein (GRSP) is recalcitrant organic matter that can be trapped in mangrove wetlands and is critical to metal sequestration. However, studies on the effects of long-term aquaculture effluents on metal pollution in adjacent mangrove wetlands and the ecological role of GRSP are lacking. For the first time, we revealed the effects of discharge histories (0, 8, and 14 years) of shrimp pond effluents on metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), including the entire process from feed to metals binding with GRSP in mangrove soils. Results showed that mangrove soils receiving the effluents generally had higher or similar metal loadings compared to the control, and long-term effluent discharge increased the potential toxicity of the metals. Aquaculture feed could be a main source of metal input. Redundancy analysis indicated that 14-year effluent discharge increased the pH, bulk density, total nitrogen, and total phosphorus of mangrove soils, reducing the potential of GRSP-bound metals. Scanning electron microscopy and infrared spectroscopy characterisation revealed that effluent disturbances changed the surface morphology and functional group contents of GRSP. This study provides insights into using GRSP as an aquaculture pollution bioindicator.

Effects of heavy metals and organic matter fractions on the fungal communities in mangrove sediments from Techeng Isle, South China

Heavy metal pollution has become a serious environmental problem in mangrove ecosystems and has attracted more attention. Most of previous studies have mainly focused on the effects of heavy metals on bacterial communities in mangrove sediments. This study was the first to investigate the effects of heavy metals (e.g., As, Co, Cr, Cu, Mn, Ni, Pb, V and Zn) and organic matter fractions (including total organic carbon (TOC), total nitrogen (TN), and total sulfur (TS)) on the fungal communities in mangrove sediments from Techeng Isle, South China. The results of this study indicated that the average contents of Mn, Pb and V of 8.30-161.80 μg/g presented relatively higher pollution levels, while the concentrations of Zn, Cr, Cu and Ni of 0.80-21.93 μg/g were lower than those recorded in other mangrove ecosystems. Furthermore, the sediment fungal community structures responded differently to the nine heavy metals and three organic matter fractions. Heavy metals Cr, Pb and V displayed significant positive correlations with Eutypella (P < 0.05), whereas significant negative correlations with Cystobasidium, Lulworthia, Cladosporium, Lulwoana and Cephalotheca (P < 0.05). In addition, the effects of heavy metals and TS on many fungal genera were opposite to those of TOC and TN. Fungal genera that decreased with high TOC and TN contents may be increased with high heavy metal contents and TS, and vice versa, and the genera that increased with high TOC and TN contents may be decreased with high heavy metals and TS. Our results suggested that many heavy metals, such as Cr, Pb and V, were sensitive to several fungal genera in mangrove sediments, and heavy metals together with organic matter fractions may participate and shape the fungal communities in mangrove sediments.

Bioaccumulation of heavy metals in fish species of Iran: a review

Accumulation of heavy metals (HMs) in fish tissues is an important factor in monitoring the health and safety of aquatic ecosystems. Furthermore, fish are important parts of aquatic food chains and play a significant role in human health. Considering the significant role of fish in the diet of humans and their ability to transfer and biomagnify HMs, it is necessary to determine and study these contaminants in fish tissues, especially in the edible parts of the fish. In addition to the other ecological and economic services of aquatic ecosystems, water bodies, especially the Persian Gulf in the south and the Caspian Sea in the north of Iran, are the main sources of seafood for people in nearby areas, as well as people living farther away who have gained access to seafood due to the extensive trade of aquatic organisms. This study provides an overview of the health conditions of the aquatic ecosystems in Iran by monitoring HM bioaccumulation in fish species. For this purpose, we reviewed, summarized, and evaluated papers published on HM concentrations in fish species from different aquatic ecosystems, including the Persian Gulf, the Caspian Sea, wetlands, rivers, qanats, water reservoirs, lakes, and dams, with emphasis on species habitats, feeding habits, and target organs in accumulation of HMs. Generally, the highest concentrations of HMs were observed in fishes collected from the Persian Gulf, followed by species from the Caspian Sea. Species inhabiting the lower zone of the water column and carnivorous and/or omnivorous species showed the highest levels of HMs. Moreover, liver was the main accumulator organ for HMs.

Heavy metal pollution and toxicity assessment in Mallorquin swamp: A natural protected heritage in the Caribbean Sea, Colombia

This work reports the level and ecotoxicity impact of metals in the sediments of the Mallorquín swamp, a protected coastal lagoon in the Caribbean coast of Colombia. The distribution of metals was in the following decreasing order: Zn > Cu > Pb > Cd > Hg, showing statistically significant differences among sites. The average Pb and Cd concentrations in sediments were about 17 and 5 times higher, respectively, compared to those in background values. Several contamination indices suggested moderate contamination of Hg, Cu, and Zn, and strong pollution due to Cd and Pb. Multivariate analysis revealed spatial variations for metals and its anthropogenic origin, such as municipal and industrial wastewater discharges (Pb, Zn, and Hg) and agricultural activities (Cd and Cu). These findings showed the negative impact of human activities and the need to apply protective management strategies.

Assessment of the ecological and human health risks from metals in shrimp aquaculture environments in Central Java, Indonesia

The occurrence and contamination level of seven important toxic metals (Cd, Cu, Co, Cr, Hg, Pb, and Zn) and three additional metals (Al, Fe, and Mn) in the water, sediment, and shrimp muscle in aquaculture areas located in Central Java, Indonesia, were investigated. The results suggest that the majority of metals have higher concentrations in the inlet followed by the outlet and ponds. Cd dissolved in the waters exhibited the highest level in Pekalongan (3.15 ± 0.33 μg L^-1). Although Pb was not detected in the water, it was detected in the sediment, and the concentration ranged from 7.6 to 15.40 mg kg^-1 dw. In general, the heavy metal concentrations in the sediments were found to decrease in the sequence Al > Fe > Mn > Zn > Cr > Cu > Co > Pb. Concentrations below the effects range low level based on the Canadian sediment quality guidelines were found for Cr, Cu, Pb, and Zn, whereas moderate sediment pollution (25-75 mg kg^-1 dw) was observed for Cr (all regions), Cu (except in the Pekalongan region), and Zn (Brebes and Tegal regions) according to the US EPA standard. The status of the waters was evaluated by calculating a pollution index derived mostly from Mn and Zn. The ecological risk (geoaccumulation index (I_geo), contamination factor (CF), pollution load index (PLI), and potential ecological risk index (ERI)) determined in the sediments indicated that all studied areas had low to moderate contamination. The concentrations of all metals in shrimp were generally below the maximum limits for seafood, except for Zn (in all stations), Pb, and Cr (Tegal and Pekalongan). The hazard index values for metals indicated that consuming shrimp would not have adverse effects on human health.

Heterogeneous Cubic Multidimensional Integrated Circuit for Water and Food Security in Fish Farming Ponds

Among major food production sectors, world aquaculture shows the highest growth rate, providing more than 50% of the global seafood market. However, water pollution in fish farming ponds is regarded as the leading cause of fish death and financial losses in the market. Here, an Internet of Things system based on a cubic multidimensional integration of circuit (MD-IC) is demonstrated for water and food security applications in fish farming ponds. Both faces of the silicon substrate are used for thin-film-based device fabrication. The devices are interconnected via through-silicon-vias, resulting in a bifacial complementary metal-oxide-semiconductor-compatible electronics system. The demonstrated cubic MD-IC is a complete, small, and lightweight system that can be easily deployed by farmers with no need for specialists. The system integrates on its outer sides simultaneous air and water quality monitoring devices (temperature, electrical conductivity, ammonia, and pH sensors), solar cells for energy-harvesting, and antenna for real-time data-transfer, while data-management circuitry and a solid-state battery are integrated on its internal faces. Microfluidic cooling technology is used for thermal management in the MD-IC. Finally, a biofriendly polymeric encapsulation is used to waterproof the embedded electronics, improve the mechanical robustness, and allow the system to float on the surface of the water.

Trace metals contamination in different compartments of the Sundarbans mangrove: A review

This review study aimed to decipher distribution of trace metals (Al, As, Cd, Cr, Cu, Hg, Pb, Ni, Mn, V, and Zn) in different compartments and human health risk in the Sundarbans mangrove ecosystems. The literature suggested relatively higher contamination of soils and sediments than fish, crustaceans, and water. Cd, Fe, Ni, and Pb are most likely to accumulate in roots of mangrove trees, while Al, As, Co, Cr, Cu, Mn, and Zn tend to accumulate in the leaves. According to human health risk studies, fish consumption is the main route of trace metals exposure to human. Majority of the studies conducted in the Indian Sundarbans; whereas, in Bangladesh part, there is an evident lack of such kind of studies. Finally, this review highlights the foremost data and research gaps, which will help to refine the risk of trace metals and scarcity of researches in the Sundarbans mangrove ecosystem.

Geochemical and probabilistic human health risk of chromium in mangrove sediments: A case study in Fujian, China

Deciphering the mobility and transfer of heavy metals in transition buffers is vital to understanding their behavior in mangrove forests. As one of the most redox-sensitive metals, the geochemical fractionation of sediment Chromium in mangrove forests and its health risks to the coastal fishermen folk is not clearly understood. This study investigated the current levels, enrichment, geochemical fractionation, and eco-toxicity on organisms of sediment Chromium from three mangrove forests in southeast China. A health risk assessment for different exposure pathways were also determined with Monte Carlo simulations technique. The results revealed that the concentration of sediment Chromium ranged from 30.75 mg kg^-1 to 99.28 mg kg^-1. The geochemical fractionations of sediment Chromium were mainly associated with amorphous Fe fraction, crystalline Fe fraction and residual fraction. Notably, 83.12% of samples analyzed in the residual phases of Chromium exceeded the background value of 40.7 mg kg^-1. Adverse effect index revealed a considerably negative effect on benthos occurrence in the mangroves. Values of non-carcinogenic risks were below unity at all samples, whereas the cancer risks associated with Cr(VI) exposure via fish consumption at median were close to 1.73 ×10^-5. A sensitivity analysis indicated that sediment Cr(VI) concentration and exposure frequency were the most relevant variables in the risk model. As the first attempt to provide information on the human health risks of sediment Chromium in mangrove forests in China, findings from this study can help track potential adverse effects and avoid risks from sediment Chromium.

Magnetic properties and correlation with heavy metals in mangrove sediments, the case study on the coast of Fujian, China

To characterize the magnetic signature of sediment heavy metal contamination and identify sources of heavy metals in mangroves, 83 sediment specimens were collected from three mangroves in Fujian, China; various magnetic parameters and heavy metal concentrations were then determined. Variation in magnetic magnetization among specimens was linked to changes in pseudo-single-domain magnetite. Average values of Co, Cu, Ni, and Zn (but not Cr or Pb) were slightly lower than background levels. Geochemical evidence suggested that Co, Cr, Ni, Ti, and V were associated with lithogenic minerals in the sediment, while Cu, Pb, and Zn were associated with terrigenous minerals. A strong positive correlation was seen between magnetic concentration-dependent parameters and metal concentrations (Cu, Pb, and Zn), suggesting enrichment of metal-containing magnetic minerals with heavy metal pollution. The combined assessment of both sediment magnetic properties and heavy metal concentrations thus provides insight into the pollution status of mangrove sediments under complex conditions.

In situ arsenic speciation and the release kinetics in coastal sediments: A case study in Daya Bay, South China Sea

In-situ study on arsenic speciation and the release kinetics in marine sediments was scarce. In this study, the distributions of labile As and their speciation in coastal sediments of Daya Bay were obtained by separate diffusive gradients in thin films (DGT) probes. Results showed that the DGT-labile As(V) was the main speciation in surface sediments (from -20 to 0 mm) with a concentration range of 0.07-3.05 μg·L^-1, while the labile As(III) was the main speciation in deep layers of sediments (from -100 to -20 mm). In coastal areas, mariculture farms was the most dominated contributor to As(V) contamination in surface sediments. Both the apparent diffusion flux estimation and the DGT induced flux in sediments (DIFS) simulation indicated that As(V) contamination in surface sediments of mariculture, harbor and petrochemical areas suffered the potential risk of As(V) release into the overlying water from sediments. DIFS modeling also found that the sediments of mariculture farms were the main sediment As pools. Linear regression analysis indicated that the mobility of As mainly attributed to the As(V) in sediments.

Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments

Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] - [AVS])/f_oc, and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

Eichhornia crassipes mediated copper phytoremediation and its success using catfish bioassay

Copper (Cu) pollution in aquaculture ponds poses substantial ecological threats. Most phytoremediation studies deal with the efforts of removing Cu from water, but seldom, such endeavors are validated by suitable bioassays. The present study undertook a two-pronged effort to remediate Cu by phytoextraction with an aquatic macrophyte, Eichhornia crassipes, and establish the efficacy of such endeavors by Clarias batrachus bioassay. For phytoextraction trials, E. crassipes was exposed to Cu concentration 0, 5, 10, 15 and 20 mg L^-1 in Hoagland solution for 21 days. The highest uptake of 2168 μg g^-1 dw was at 10 mg L^-1 Cu exposure, and efficient root to leaf translocation was seen for 5-10 mg Cu L^-1. For these doses, there was 55-57% decline in Cu from test waters. We evaluated morphological, physiological and biochemical response of plants towards Cu stress to gauge its phytomediation capacity. For bioassays, fish were reared for 7 days in phytoremediated Cu doses of 5 and 10 mg L^-1. The accumulation of Cu followed the pattern: kidney > liver > gill > muscle. Fish muscle accumulated 21.8-27.0 μg Cu g^-1 dw after 7 d, however, for E. crassipes remediated doses, muscle accumulated 8.2-10.9 μg Cu g^-1 dw, which was within the safe levels of Cu in edible tissues. Metal doses declined protein contents and augmented malondialdehyde, superoxide dismutase, catalase and peroxidase concentrations in tissues. Although their concentrations in remediated groups failed to reach the levels of control fish, significant recovery in these parameters were observed. The results pointed towards the efficacy of Cu phytoextration by E. crassipes.

Metals in mangrove ecosystems and associated biota: A global perspective

Mangrove forests prevalent along the intertidal regions of tropical and sub-tropical coastlines are inimitable and dynamic ecosystems. They protect and stabilize coastal areas from deleterious consequences of natural disasters such as hurricanes and tsunamis. Although there are reviews on ecological aspects, industrial uses of mangrove-associated microorganisms and occurrence of pollutants in a region-specific manner, there is no exclusive review detailing the incidence of metals in mangrove sediments and associated biota in these ecosystems on a global level. In this review, mangrove forests have been classified in a continent-wise manner. Most of the investigations detail the distribution of metals such as zinc, chromium, arsenic, copper, cobalt, manganese, nickel, lead and mercury although in some cases levels of vanadium, strontium, zirconium and uranium have also been studied. Seasonal, tidal, marine, riverine, and terrestrial components are seen to influence occurrence, speciation, bioavailability and fate of metals in these ecosystems. In most of the cases, associated plants and animals also accumulate metals to different extents and are of ecotoxicological relevance. Levels of metals vary in a region specific manner and there is disparity in the pollution status of different mangrove areas. Protecting these vulnerable ecosystems from metal pollutants is important from environmental safety point of view.

Contamination level, chemical fraction and ecological risk of heavy metals in sediments from Daya Bay, South China Sea

Contamination level, chemical fraction and ecological risk of heavy metals in sediments from Daya Bay (DYB) were conducted in this study. The results revealed that the concentration of Cr, Cu, Zn, As, Cd and Pb in sediments were in the range of 36.38-90.33, 9.54-61.32, 33.54-207.33, 7.80-18.43, 0.13-0.43 and 15.89-30.01 mg kg^-1, respectively, with bioavailable fractions of 13.29, 54.16, 47.60, 32.74, 68.14, 26.59%, respectively. A modified potential ecological risk index (MRI) was used for the ecological risk assessment, with ecological risk contribution ratios of 75.73, 14.29, 5.47, 1.74, 1.57 and 1.21% for Cd, As, Cu, Cr, Pb and Zn, respectively. The main contaminants were Cd and As, with their ecological risks "High" and "Moderate" levels, and their enrichment degrees "Moderately Severe" and "Moderate", respectively. The multivariate statistical analysis suggested that the various anthropogenic activities along the bay might contribute mainly to the heavy metals contamination in DYB.

Heavy metal pollution in immobile and mobile components of lentic ecosystems-a review

With growing population and urbanization, there is an increasing exploitation of natural resources, and this often results to environmental pollution. In this review, the levels of heavy metal in lentic compartments (water, sediment, fishes, and aquatic plants) over the past two decades (1997-2017) have been summarized to evaluate the current pollution status of this ecosystem. In all the compartments, the heavy metals dominated are zinc followed by iron. The major reason could be area mineralogy and lithogenic sources. Enormous quantity of metals like iron in estuarine sediment is a very natural incident due to the permanently reducing condition of organic substances. Contamination of cadmium, lead, and chromium was closely associated with anthropogenic origin. In addition, surrounding land use and atmospheric deposition could have been responsible for substantial pollution. The accumulation of heavy metals in fishes and aquatic plants is the result of time-dependent deposition in lentic ecosystems. Moreover, various potential risk assessment methods for heavy metals were discussed. This review concludes that natural phenomena dominate the accumulation of essential heavy metals in lentic ecosystems compared to anthropogenic sources. Amongst other recent reviews on heavy metals from other parts of the world, the present review is executed in such a way that it explains the presence of heavy metals not only in water environment, but also in the whole of the lentic system comprising sediment, fishes, and aquatic plants.

Contamination and ecological risk assessment of trace elements in sediments of the rivers of Sundarban mangrove forest, Bangladesh

In this study, total concentrations of 16 trace elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sb, Hg, Pb, Th and U) in sediments of the rivers of the Sundarban mangrove forest, after the catastrophic oil spill accident in the Sela river of Sundarban, were determined. The overall mean concentrations of V, Cr, Fe and Cd in surface sediments of the Sundarban are remarkably higher than available literature data of those elements. Trace element contamination assessment, using different environmental contamination indices, reveals that As, Sb, Th and U are low to moderately contaminated while Cd is moderately to severely contaminated in the sediments of this area. The multivariate statistical analyses were applied to reveal the origin and behavior of the elements during their transport in the mangrove ecosystem. High Cr, Ni, Cu and As concentrations suggest the risk of potentially adverse biological effects in the ecosystem.