Accumulation of toxic metals and organic micro-pollutants in sediments from tropical urban rivers, Kinshasa, Democratic Republic of the Congo

Review on heavy metal contaminants in freshwater fish in South India: current situation and future perspective

The primary natural resource we use in our daily lives for a variety of activities is freshwater for drinking and various developmental goals. Furthermore, the pace of human population increase worldwide is rising rapidly and has a great impact on the Earth's natural resources. Natural water quality has diminished owing to various anthropogenic activities. Water is crucial to the life cycle. On the other hand, chemical and agricultural industries pollute heavy metals. Acute and chronic diseases caused by heavy metals, such as slow metabolism and damage to the gills and epithelial layer of fish species, are divided into two categories. Pollutants can also harm liver tissues and result in ulceration as well as diseases such as fin rot, tail rot, and gill disease. The most prevalent heavy metals are As, Cr, Pb, and Hg, which are systemic toxicants that affect human health. These metals are categorized as carcinogens by the US Environmental Protection Agency and the worldwide agency for cancer research because they cause organ damage even at low exposure levels. The focus of the current study is to review various freshwater sources of heavy metal pollution.

Identification of the Contamination Sources by PCBs Using Multivariate Analyses: The Case Study of the Annaba Bay (Algeria) Basin

Persistent Organic Pollutants (POPs), particularly the indicator polychlorinated biphenyls (PCBs), were first quantified in water and sediments of two wadis, Boujemaâ and Seybouse, as well as in the effluents from a fertilizer and phytosanitary production industrial plant (Fertial). Since these contaminated discharges end in Annaba Bay (Algeria) in the Mediterranean Sea, with a significant level of contamination, all the potential sources should be identified. In this work, this task is conducted by a multivariate analysis. Liquid-liquid extraction and gas chromatography/mass spectrometry (GC-MS) methods were applied to quantify seven PCB congeners, usually taken as indicators of contamination. The sum of the PCB concentrations in the sediments ranged from 1 to 6.4 μg/kg dw (dry weight) and up to 0.027 μg/L in waters. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used for the multivariate analysis, indicating that the main sources of PCB emissions in the bay are urban/domestic and agricultural/industrial. The outfalls that mostly contribute to the pollution of the gulf are the Boujemaâ wadi, followed by the Seybouse wadi, and finally by the Fertial cluster and more precisely the annex basin of the plant. Although referring to a specific site of local importance, the work aims to present a procedure and a methodological analysis that can be potentially applicable to further case studies all over the world.

Assessment of metal bioavailability in sediments and bioaccumulation in edible bivalves, and phyto-remediation potential of mangrove plants in the tropical (Kali) estuary, India

The bioavailability of metals (Fe, Mn, Zn, Cu, Co and Ni) in sediment cores (K-1, K-2, K-3 and K-4) and bioaccumulation in edible bivalves were studied to determine the toxicity of metals in the Kali Estuary, India. Enrichment Factor (EF) construed anthropogenic sources of Zn, Co and Ni, while Geo-accumulation Index (Igeo) revealed pollution of Zn and Ni based on total metal analysis. The Pollution Load Index (PLI >1) supported anthropogenic origin of metals in estuary. Metal speciation study indicated bioavailability of metals in sediments. The bioavailable Mn and Co equalled/exceeded the Apparent Effect Threshold (AET) limit (cores K-1, K-3 and K-4) and indicated toxicity to estuarine biota. The metals in Metetrix casta (Fe, Mn, Zn, Cu, and Ni), Saccostrea cucullata (Fe, Mn, Zn, Cu, Co and Ni) and Villorita cyprinoides (Fe, Mn, Zn, Cu, Co and Ni) exceeded the permissible bioaccumulation limit. Thus, revealed metal toxicity to bivalves and labelled them un-safe for human consumption. Translocation Factor (TF > 1) indicated the use of Kandelia candel in phyto-remediation of Fe, Zn, Cu, Co and Ni at station K-3, and Sonnaretia caseoloris in phyto-remediation of Fe, Zn and Ni at station K-4.

A tale of two rivers: development, destruction, and despair in Ongata Rongai, Kenya

Introduction

Ongata Rongai is a rapidly growing peri-urban space in Nairobi Metropolitan, Kenya. The last 10 years have seen exponential population growth and building development leading to overcrowding and pressure on water and environmental resources. This original research sheds light on interactions among humans, animals, and this rapidly changing urban environment. It is therefore a quintessentially One Health study.

Methods

Qualitative and ethnographically informed methods are employed to better understand the impact of rapid growth on the riparian environment and the effect of this on those who depend on it. The reflexive use of archival material and a historical ethnographic approach enabled in-depth narratives to address these issues within a longitudinal context, and the use of deliberate walking alongside visual methodologies and more traditional anthropological methods make this study novel both in terms of methodological approach and findings.

Results

This study finds that people cite high levels of pollution from solid waste and sewage have made the rivers almost unusable and a hazardous place for both humans and animals. Yet, in the past, these rivers played key roles in daily life. There is frustration with structural-level actors' moribund attitude to the environment. The poor health of the rivers and riparian environment leads to human and animal health challenges, increased pressure on water resources, and economic pressure due to a loss of livelihoods.

Discussion

The study contributes to what is currently a fairly small literature on urban riparian spaces globally, but one which is of growing and vital importance given the rapidly increasing percentage of humans who now reside in urban spaces. It contributes to WASH and urban clean water knowledge as well as One Health, public health, and urban growth narratives, and directly addresses challenges faced by SDG 6.

Microplastic-sorbed persistent organic pollutants in coastal Mediterranean Sea areas of Tunisia

Microplastics (MPs) are emerging pollutants of global concern due to their pervasiveness, high sorption ability for persistent organic pollutants (POPs) and direct and indirect toxicity to marine organisms, ecosystems, as well as humans. As one of the major coastal interfaces, beaches are considered among the most affected ecosystems by MPs pollution. The morphological characteristics of MPs (pellets and fragments) collected from four beaches along the Tunisian coast and sorbed POPs, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), were investigated in this study. The results showed that the MPs varied greatly in color, polymer composition and degradation degree. The color varied from colored to transparent and the most prevalent polymer identified using Raman spectroscopy was polyethylene. Scanning electron microscope (SEM) images exhibited various surface degradation features including cavities, cracks, attached diatom remains, etc. The concentrations of Σ12PCBs over all beaches ranged from 14 to 632 ng g-1 and 26 to 112 ng g-1 in the pellets and fragments, respectively, with a notable presence and dominance of highly-chlorinated PCBs such as CB-153 and -138. Among the OCPs, γ-HCH is the only compound detected with concentrations ranging from 0.4 to 9.7 ng g-1 and 0.7 to 4.2 ng g-1 in the pellets and fragments, respectively. Our findings indicate that MPs found on the Tunisian coast may pose a chemical risk to marine organisms as the concentrations of PCBs and γ-HCH in most of the analysed samples exceeded the sediment-quality guidelines (SQG), especially the effects range medium (ERM) and the probable effects level (PEL). As the first report of its kind, the information gathered in this study can serve as the baseline and starting point for future monitoring work for Tunisia and neighbouring countries, as well as for stakeholders and coastal managers in decision-making processes.

Organic matter degradation determines the concentrations of polybrominated diphenyl ethers in sediments. Multivariate learning on environmental and experimental models

Sediment organic matter (SOM) plays an important role in capturing polybrominated diphenyl ethers (PBDEs) due to its affinity to hydrophobic and lipophilic compounds. Previous publications about correlations between PBDE concentrations and SOM content showed discrepancies among the results, reporting either significant positive correlations or no correlations at all. This work aimed to provide a deeper insight into SOM characteristics that might determine the concentrations of PBDEs in sediments. Sediment samples from Mendoza province, Argentina, were analyzed to contrast two models, environmental and experimental, using multivariate learning methods. Mendoza has been going through increasing events of drought and water scarcity, hence the occurrence, transport, and fate of contaminants as PBDEs in aquatic environments is of superlative importance. Principal component analysis (PCA) and partial least squares regression (PLS) were used to evaluate the correlations between physicochemical properties of sediments, semi-quantitative Fourier transform infrared (FTIR) area ratios obtained from SOM spectra, and PBDE concentrations in sediments. Moreover, a linear model was proposed to determine SOM density using FTIR area ratios and it was used as an additional variable in multivariate analyses. The results obtained from PCA and PLS were consistent and revealed that PBDE concentrations in sediments were correlated with a more degraded SOM, characterized by shorter and more branched hydrocarbon chains. PBDE concentrations were also correlated with higher SOM density values, which in turn were correlated with SOM degradation. These findings extend previous understanding and emphasize that not only is the organic matter content a factor in determining PBDE concentrations in sediments, but also and more significantly, its degree of degradation.

Environmental quality and ecotoxicity of sediments from the lower Salado River basin (Santa Fe, Argentina) on amphibian larvae

The lower Salado River basin receive agricultural, industrial and domestic waste water. So, the aim was to evaluate the quality of three sampling sites that belong to the Salado River basin (S1: Cululú stream; S2: Salado River, at Esperanza City, S3: Salado River at Santo Tomé City) based on physicochemical parameters, metals and pesticides analyses and ecotoxicity on Rhinella arenarum larvae. R. arenarum larvae (Gosner Stage -GS- 25) were chronically exposed (504h) to complex matrixes of surface water and sediment samples of each site for the determination of the survival rate. Biomarkers of oxidative stress, neurotoxicity and genotoxicity were analyzed in R. arenarum larvae (GS. 25) after exposure (96h) to the complex matrix of water and sediment. The water quality index showed a marginal quality for all sites, influenced mainly by low dissolved oxygen, high total suspended solid, phosphate, nitrite, conductivity, Pb, Cr and Cu levels. Metal concentrations were higher in sediment than in water samples (˜34-35000 times). In total, thirty different pesticides were detected in all water and sediment samples, S1 presented the greatest variety (26). Glyphosate and AMPA were detected in sediments from all sites, being higher in S3. N,N-Diethyl-meta-toluamide (DEET) and atrazine were detected in all water samples. Greatest mortality was observed in larvae exposed to samples from S1 from 288h (43.3%), reaching a maximum value of 50% at 408h. Oxidative stress and genotoxicity were observed in larvae exposed to S1 and S3 matrix samples. Neurotoxicity was observed in larvae exposed to all matrix samples. The integrated biomarker response index showed that larvae exposed to S1 and S3 were the most affected. According to the physicochemical data and the ecotoxicity assessment, this important river basin is significantly degraded and may represent a risk to aquatic biota, especially for R. arenarum larvae.

Spatial Distribution, Source Identification, and Potential Ecological Risk Assessment of Heavy Metal in Surface Sediments from River-Reservoir System in the Feiyun River Basin, China

To investigate the pollution characteristics of the surface sediments of the river-reservoir system in the Feiyun River basin, a sediment heavy metal survey was conducted for the first time in the Feiyun River basin. Surface sediments from 21 sampling sites in the Feiyun River basin were collected, and the concentrations and spatial distribution characteristics of 15 heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Mn, V, Co, Mo, Sb, W, Fe, and Se) were analyzed. Three heavy metal ecological risk assessment methods were used to evaluate the potential risks of heavy metals in sediments, and the sources of major heavy metals were traced by correlation analysis and principal component analysis. The results show that (1) the average concentration of heavy metals (As) (212.64 mg/kg) and (Sb) (4.89 mg/kg) in Feiyun River Basin is 33.3 and 6.89 times the background value of Zhejiang Province; the overall spatial distribution of heavy metals is: the mainstream of Feiyun River > Zhaoshandu Reservoir > Shanxi Reservoir, thereby, the pollution is relatively significant; (2) by processing the geo-accumulation index and enrichment index methods, As and Sb are classified as 'severely polluted', 'moderately severely polluted' and 'severely polluted', 'very severe polluted' respectively; (3) the potential ecological index evaluates the surface sediments in the Feiyun River Basin as a very high risk level, the main environmental risk factors are As, Sb, Cd and Mo; (4) the principal component analysis results show that the heavy metals in the sediments of the Feiyun River Basin may be mainly affected by human activities such as sewage from domestic and agricultural activities, mining and smelting, and the others are affected by natural factors.

Seasonal distributions and risk assessment of polychlorinated biphenyls (PCBs) in the surficial sediments from the Turag River, Dhaka, Bangladesh

Polychlorinated biphenyls (PCBs) were determined in sediment samples collected from the Turag River, Dhaka city, Bangladesh. This river provides critical ecological services to agriculture, industry, and transportation. However, it is one of the most polluted rivers surrounding the capital city. This study analyzed six PCB congeners (PCB 10, PCB 28, PCB 52, PCB 138, PCB 153, and PCB 180) by GC-ECD at 9 sampling sites in two different seasons. The total concentrations of PCBs in studied samples varied from 344 to 0.217 ng/g dw and 10.6 to 1.68 ng/g dw in Monsoon-season and Dry-season, respectively. The paramount contributor-congener to the total PCBs was PCB 180, and it was found at all the study sites. The ecological risk assessment indicated a high potential risk in the Monsoon-season ([Formula: see text]= 277) and low potential risk in the Dry-season ([Formula: see text]= 25.7). Sediment quality guideline quotients (SQGQs) showed that PCBs in the Monsoon-season would cause "no" or "moderate" biological effects on organisms at every site except site-5 (S5) (high biological effects), while no adverse ecotoxicological effect was observed in the Dry-season. Considering both probable effect level (PEL) and threshold effect level (TEL), the new sediment quality guideline quotient (NSQGQ) showed that in the Dry-season PCB contamination would cause "moderate" biological effects. At the same time, in the Monsoon-season, the findings remained consistent with the findings of SQGQ. This study looked at the PCB contamination scenario in the Turag River sediments for the first time and allowed for a comparison with other rivers worldwide.

Protection against the Phytotoxic Effect of Mercury Chloride by Catechin and Quercetin

Plants when exposed to toxic levels of metals can suffer morphological or physiological damage because toxic metals can interact with several vital molecules in the plant. One possibility to remove these contaminants from the environment is through the phytoremediation technique, since secondary metabolites produced by plants can reverse these damages. To evaluate the cytoprotective activity, the dry mass and possible damage to the membranes of Lactuca sativa (lettuce) seedlings subjected to different concentrations of mercury chloride in association with catechin and quercetin in suballelopathic concentration were determined. The coordination of mercury chloride with substances was also evaluated using vibrational spectroscopy (Raman and FTIR). The interaction of the mentioned flavonoids with mercury chloride was evidenced through vibrational spectroscopy. When the metal was associated with catechin and quercetin, there was an increase in dry mass of almost 3 times when compared with the HgCl2 alone, demonstrating that these flavonoids act as cytoprotective agents. However, in the presence of catechin and quercetin, membrane damage caused by mercury chloride has a level similar to that observed in control plants, demonstrating none statistical difference. Comparing the highest concentration with the lowest concentration of the metal associated with quercetin, it can be seen that the intensity of the peaks in this region decreases when the concentration of the metal increases, indicating an interaction between the metallic compound and the flavonoid. In this context, the use of secondary metabolites can be an alternative in the process of remediation of areas contaminated by mercury chloride, as they mitigate the effects of mercury chloride on lettuce seedlings.

Occurrence of toxic metals and their selective pressure for antibiotic-resistant clinically relevant bacteria and antibiotic-resistant genes in river receiving systems under tropical conditions

The co-occurrence of heavy metals, antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) from hospital effluents spreading into the river receiving systems and evaluating associated risks are topics of scientific interest and still under-studied in developing countries under tropical conditions. To understand the selectors of the ARGs, we examined the occurrence of heavy metals (Cr, Co, Ni, Cu, Cd, Pb and Zn), associated ARB (β-lactam-resistant Escherichia coli, β-lactam-resistant Enterobacteriaceae, and carbapenem-resistant Enterobacteriaceae) and ARGs (bla_OXA, bla_CTX-M, bla_IMP, bla_TEM) in water and sediments from two sub-urban rivers receiving urban and hospital effluent waters in the Democratic Republic of the Congo (DRC). High abundances of ARB and ARGs were observed in all sediment samples. All the metal contents correlated negatively with grain size (- 0.94 ≤ r ≤  - 0.54, p < 0.05) except for Ni and positively with organic matter content and total copies of 16 s rRNA (0.42 ≤ r ≤ 0.79, p < 0.05), except for Ni and Zn. The metals had a significant positive correlation with the faecal indicator Enterococcus except for Ni and Cd (0.43 ≤ r ≤ 0.67, p < 0.05). Carbapenem-resistant Enterobacteriaceae correlated negatively with Zn (r =  - 0.44, p < 0.05) and positively with all the rest of toxic metals (0.58 ≤ r ≤ 1.0, p < 0.05). These results suggested that some metals had a great influence on the persistence of ARB and ARGs in sediments. Overall, this study strongly recommends the managing urban wastewater to preserve water resources used for human and agricultural purposes. Additionally, we recommend the utilizing biological indicators (faecal indicator bacteria, ARB, ARGs) when investigating urban wastewater pollutions.

Aquatic Ecological Risk of Heavy-Metal Pollution Associated with Degraded Mining Landscapes of the Southern Africa River Basins: A Review

Africa accounts for nearly 30% of the discovered world’s mineral reserves, with half of the world’s platinum group metals deposits, 36% of gold, and 20% of cobalt being in Southern Africa (SA). The intensification of heavy-metal production in the SA region has exacerbated negative human and environmental health impacts. In recent years, mining waste generated from industrial and artisanal mining has significantly affected the ecological integrity of SA aquatic ecosystems due to the accelerated introduction and deposition of heavy metals. However, the extent to which heavy-metal pollution associated with mining has impacted the aquatic ecosystems has not been adequately documented, particularly during bioassessments. This review explores the current aquatic ecological impacts on the heavily mined river basins of SA. It also discusses the approaches to assessing the ecological risks, inherent challenges, and potential for developing an integrated ecological risk assessment protocol for aquatic systems in the region. Progress has been made in developing rapid bioassessment schemes (RBS) for SA aquatic ecosystems. Nevertheless, method integration, which also involves heavy-metal pollution monitoring and molecular technology, is necessary to overcome the current challenges of the standardisation of RBS protocols. Citizenry science will also encourage community and stakeholder involvement in sustainable environmental management in SA.

Assessment of polycyclic aromatic hydrocarbons in three environmental components from a tropical estuary in Northeast Brazil

The evaluation of occurrence, risk quotient (RQ), bioaccumulation factor (BAF), and sources of PAH was conducted in Sergipe-Poxim estuarine system. PAH distribution that ranged from 7.1 to 30.9 ng L^-1 (surface water, SW), 5.4 to 19.5 ng g^-1 (sediment, S), and 4.3 to 18.1 ng g^-1 (oyster, O), characterized the environment with low contamination; 2-3 (SW), 5-6 (S), and 4 (O) PAH rings accounted for 54.5%, 68.7%, and 87.7%, respectively, along with naphthalene (SW), dibenzo(a,h)anthracene (S), and pyrene (O) as the prevailing compounds. PCA suggested the predominance of particular groups related to SW (LMW-PAH), S (HMW-PAH), and O (pyrene and fluoranthene). Furthermore, one sample of O presented a high PAH bioavailability as shown through the BAF, with emphasis on pyrene (BAF = 26.8). The RQ showed a low to moderate range in SW and S; hence, in-depth information about the possible toxic effect in organisms of this region is required.

Occurrence, distribution, and pollution indices of potentially toxic elements within the bed sediments of the riverine system in Pakistan

Potentially toxic elements (PTEs) are a major source of pollution due to their toxicity, persistence, and bio-accumulating nature in riverine bed sediments. The sediment, as the largest storage and source of PTEs, plays an important role in transformation of mercury (Hg), lead (Pb), nickel (Ni), chromium (Cr), copper (Cu), zinc (Zn), and other toxic PTEs. Several important industrial hubs that contain a large population along the banks of different rivers, such as Kabul, Sutlej, Ravi, Jhelum, and Chenab in Pakistan, are acting as major sources of PTEs. In this study, 150 bed sediment samples (n=30 from each river) were collected from different sites. Total (acid extracted) PTE (Hg, Cu, Cr, Ni, Zn, and Pb) concentrations in bed sediments were determined using inductively coupled plasma mass spectrometry (ICP-MS). Sediment pollution indices were calculated in the major rivers of Pakistan. The results demonstrated high levels of Hg and Ni concentrations which exceeded the guideline standards of river authorities in the world. The contamination factor (CF) and contamination degree (CD) indices for Hg, Ni, and Pb showed a moderate to high (CF≥6 and CD≥24) contamination level in all the selected rivers. The values of geo-accumulation index (I_geo) were also high (I_geo≥5) for Hg and Pb and heavily polluted for Ni, while Cr, Cu, and Zn showed low to unpolluted (I_geo) values. Similarly, the enrichment factor (EF) values were moderately severe (5≤EF≤10) for Hg, Pb, and Ni in Sutlej, Ravi, and Jhelum, and severe (10≤EF≤25) in Kabul and Jhelum. Moreover, Hg and Ni showed severe to very severe enrichment in all the sampling sites. The ecological risk index (ERI) values represented considerable, moderate, and low risks, respectively, for Hg (The ERI value should not be bold. Please unbold the  ERI in the whole paper. It should be same like RI, CD and EF. [Formula: see text]≥160), Pb and Ni (40≤[Formula: see text]≤80), and Cr, Cu, and Zn ([Formula: see text]≤40). Similarly, potential ecological risk index (PERI) values posed considerable (300≤RI≤600) risk in Ravi and moderate (150≤RI≤300) in Kabul and Jhelum, but low (RI≤150) risk in Ravi and Chenab. On the basis of the abovementioned results, it is concluded that bed sediment pollution can be dangerous for both ecological resources and human beings. Therefore, PTE contamination should be regularly monitored and a cost-effective and environmentally friendly wastewater treatment plant should be installed to ensure removal of PTEs before the discharge of effluents into the freshwater ecosystems.

Bioaccumulation and human health risk assessment of trace metals in the freshwater mussel Cristaria plicata in Dongting Lake, China

Trace metal contamination in water and bioaccumulation in aquatic organisms are human health risks of increasing concern. However, the bioaccumulation of trace metals in the organs of the mussel Cristaria plicata in Dongting Lake, China and the human health risks of mussel consumption are largely unknown. We investigated the concentrations of 15 trace metals and metalloids in surface water, sediments, and C. plicata organs (foot, gill, mantle, and visceral mass) and quantified the bioaccumulation and human health risk of these trace metals in specimens collected from Dongting Lake. The concentrations of most metals in surface water exceeded previously published background values. In contrast, the concentrations of most metals in sediments showed a decreasing trend. Overall, the metal concentrations in the gill and visceral masses of C. plicata were higher than those in the foot and mantle, and higher bioaccumulation capacities were observed for essential metals than for nonessential metals. The mean concentrations of the trace elements Zn, Pb, Cd, As, Cu, and Cr in C. plicata foot samples were lower than the threshold values established by international and Chinese organizations. The estimated daily intake (EDI) values of the essential metal Mn in C. plicata foot was higher than the recommended tolerable daily intake (TDI) values for juveniles. Only Mn for juveniles and As for both juveniles and adults may pose noncarcinogenic health risks through foot consumption. The hazard index (HI) values for adults and juveniles were higher than 1, suggesting significant risks of noncarcinogenic effects to humans by exposure to multiple metals.

Polycyclic aromatic hydrocarbons (PAHs) in urban stream sediments of Suzhou Industrial Park, an emerging eco-industrial park in China: Occurrence, sources and potential risk

In this study, urban stream sediment samples were collected in the Suzhou Industrial Park (SIP), one of the earliest national demonstration eco-industrial parks of China. PAHs were analyzed in these sediments, and concentrations of total PAHs were 180-81,000 ng g^-1 (5700 ± 14,000 ng g^-1). Medium molecular weight (4- ring) PAHs were predominant (42 ± 12%), followed by high molecular weight (5- and 6- ring) PAHs (31 ± 10%). No correlation was found between concentrations of PAHs and land uses of SIP in this study. Diagnostic ratios and a positive matrix factorization (PMF) model indicated that coal/biomass combustion might be the primary PAH source (61%), followed by non-combustion sources (21%) and vehicular emission (18%). According to the spatial analysis, PAHs in the sediments of SIP might be mainly associated with the coal/biomass combustion in the northeast industrial zone. Residential & commercial activities seem not to be the major causes of PAH contamination. Total PAH toxic equivalent concentrations, effect range low/effect range median values, and mean effects range-median quotient all showed that PAHs were present at a low toxicity risk level in most regions of the SIP. However, vigilance is required at some sampling sites with extremely high PAH concentrations or high mean effects range-median quotient.

Concentrations, distribution and risk of polycyclic aromatic hydrocarbons in sediments from seven major river basins in China over the past 20 years

Polycyclic aromatic hydrocarbons (PAHs) in river sediments in China have been extensively investigated. However, most previous studies only reported information about specific locations. As a result, the distribution and changes of these chemicals in sediments nationwide remain unknown. Based on published data during 1997-2020, we conducted a systematic meta-analysis to understand the concentration, risk and the spatiotemporal variation of PAHs in river sediments from the seven major river systems in China. The report provides a national picture of PAHs in river sediments of China. Among the seven river systems, higher concentrations of sediment PAHs are found in the basins of Liaohe River and Haihe River. In the study sediments, high-molecular-mass (4-6-ring) PAHs were predominated, reflecting the widespread combustion of coal and fossil fuels across China. In addition, PAH source assessment also suggests that raw coal and crude oil are important contributors to PAH concentrations in the rivers in northeastern China. Over the past 20 years, there is no downward trend in the concentrations of Σ₁₆PAHs in sediments in the seven river basins; but the contribution of high-temperature combustion to the pollution has declined. In addition, our calculated risks from sediment PAHs seem to decline between 1997-2006 and 2007-2017 periods, although the differences were not statistically significant (p > 0.05). Of note, the data collection and the risk assessment methods used in this preliminary survey may result in some uncertainty. Our results suggest that the PAHs in river sediments in China still need to be paid attention to due to the complexity of their sources and harms to aquatic organisms.

Occurrence of organic micropollutants and human health risk assessment based on consumption of Amaranthus viridis, Kinshasa in the Democratic Republic of the Congo

The contamination of water resource and food chain by persistent organic pollutants (POPs) constitutes a major environmental and human health concern worldwide. The aim of this study was to investigate the levels of POPs in irrigation water, soil and in Amaranthus viridis (A. viridis) from different gardening sites in Kinshasa to evaluate the potential environmental and human health risks. A survey study for the use of pesticides and fertilizers was carried out with 740 market gardeners. The levels of POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs)) were analyzed in irrigation water and 144 vegetable samples collected from different gardening sites. The assessment of potential human health risk was estimated by calculating daily intake and toxic equivalency to quantify the carcinogenicity. The results show highest PAH levels in A. viridis from all studied sites. The concentrations of the sum of seven PCBs (Σ7PCB_S) congeners in analyzed plants ranged between 15.89 and 401.36 ng g^-1. The distributions of OCPs in both water and A. viridis were congener specific, chlorpyrifos-ethyl and p,p'-DDE were predominantly detected. Among PBDEs, only BDE47 was quantified with noticeable concentration in A. viridis, while no PBDEs were detected in irrigation water. Higher estimated daily intake values indicate that consuming leafy vegetables might associate with increased human health risks. However, calculated incremental lifetime cancer risk values indicates no potential carcinogenic risk for the local population. The results of this study provide important information on A. viridis contamination by POPs and strongly recommend implementing the appropriate measures to control the use of chemicals used in studied gardening areas. Thus in Kinshasa, urban agriculture control programs for POPs and fertilizers is very important in order to protect the public health through direct and dietary exposure pathways.

Role of Biofilms in Contaminant Bioaccumulation and Trophic Transfer in Aquatic Ecosystems: Current State of Knowledge and Future Challenges

In freshwater environments, microbial assemblages attached to submerged substrates play an essential role in ecosystem processes such as primary production, supported by periphyton, or organic matter decomposition, supported by microbial communities attached to leaf litter or sediments. These microbial assemblages, also called biofilms, are not only involved in nutrients fluxes but also in contaminants dynamics. Biofilms can accumulate metals and organic contaminants transported by the water flow and/or adsorbed onto substrates. Furthermore, due to their high metabolic activity and their role in aquatic food webs, microbial biofilms are also likely to influence contaminant fate in aquatic ecosystems. In this review, we provide (1) a critical overview of the analytical methods currently in use for detecting and quantifying metals and organic micropollutants in microbial biofilms attached to benthic substrata (rocks, sediments, leaf litter); (2) a review of the distribution of those contaminants within aquatic biofilms and the role of these benthic microbial communities in contaminant fate; (3) a set of future challenges concerning the role of biofilms in contaminant accumulation and trophic transfers in the aquatic food web. This literature review highlighted that most knowledge on the interaction between biofilm and contaminants is focused on contaminants dynamics in periphyton while technical limitations are still preventing a thorough estimation of contaminants accumulation in biofilms attached to leaf litter or sediments. In addition, microbial biofilms represent an important food resource in freshwater ecosystems, yet their role in dietary contaminant exposure has been neglected for a long time, and the importance of biofilms in trophic transfer of contaminants is still understudied.

Environmental assessment of persistent organic pollutants in surface sediments of the Danshui River basin, Taipei, Taiwan

Surface sediments from the Danshui River basin were collected and analyzed for persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dichloro-diphenyl-trichloroethanes (DDTs). The total concentrations of each category ranged from 96 to 3803 ng g^-1 for PAHs, 0.02 to 54.9 ng g^-1 for PCBs, and from below the detection limit to 10.3 ng g^-1 for DDTs. These values are within the ranges observed for river and estuarine sediments of industrial and urbanized areas in Taiwan and worldwide. A decreasing trend of POP levels was observed in comparison with the levels reported in previous studies. Significant correlations between the levels of compounds and black carbon (BC) were found, suggesting that these POPs and BC may have similar transport processes. Based on sediment quality guidelines (SQGs), the ecological risk posed by these POPs toward sediment-dwelling organisms in the Danshui River basin is relatively low. Long-term monitoring of contaminant levels is necessary to develop appropriate management tools due to the importance of the Danshui river basin as a water source for metropolitan areas.

Persistent organic pollutants in sediments of the Wouri Estuary Mangrove, Cameroon: Levels, patterns and ecotoxicological significance

The anthropogenic impact in the Wouri Estuary Mangrove located in the rapidly developing urban area of Douala, Cameroon, Africa, was studied. A set of 45 Persistent Organic Pollutant were analysed in surficial mangrove sediments at 21 stations. Chlorinated Pesticides (CLPs), Polychlorinated Biphenyls (PCBs) and Polycyclic Aromatic Hydrocarbons (PAHs) have concentrations ranging from 2.2 - 27.4, and 83 - 544 ng/g, respectively. The most abundant CLPs were endosulfan, alachlor, heptachlor, lindane (γ-HCH) and DDT, which metabolites pattern revealed recent use. Selected PAHs diagnostic ratios show pyrolytic input predominantly. The sum of 7 carcinogenic PAHs (ΣC-PAHs) represented 30 to 50% of Total PAHs (TPAHs). According to effect-based sediment quality guidelines, the studied POPs levels imply low to moderate predictive biological toxicity. This study contributes to depict how far water resources are shifting within what is now termed the Anthropocene due to increasing local pressures in developing countries or African countries.

Geochemical behaviour and risk assessment of trace elements in a tropical river, Northwest Borneo

By convention, dissolved trace elements in the river water are considered to be the fraction that passes through a 0.45 μm filter. However, several researchers have considered filtration cut-off other than 0.45 μm for the separation of dissolved trace elements from particulate fraction. Recent research indicated that trace elements could exist in particulate form as colloids and natural nanoparticles. Moreover, the trace elements in the continental dust (aerosols) constitute a significant component in their geochemical cycling. Due to their high mobility, the trace elements in the micron and sub-micron scale have biogeochemical significance in the coastal zone. In this context, this study focuses on the highly mobile fraction of trace elements in particulates (<11 μm) and dissolved form in the Lower Baram River. A factor model utilizing trace elements in the dissolved and mobile phase in the particulates (<11 μm) along with water column characteristics and the partition coefficient (K_d) of the trace elements indicated a more significant role for manganese oxyhydroxides in trace element transport. Perhaps, iron oxyhydroxides play a secondary role. The factor model further illustrated the dissolution of aluminium and authigenic clay formation. Except for Fe and Al, the contamination risk of mobile trace elements in particulates (<11 μm) together with dissolved form are within the permissible limits of the Malaysian water quality standards during monsoon (MON) and postmonsoon (POM) seasons.

Heavy metals and persistent organic pollutants contamination in river, estuary, and marine sediments from Atlantic Coast of Democratic Republic of the Congo

The pollution assessment and the evaluation of potential risks in the Atlantic Coastal Region of the Democratic Republic of the Congo are still very limited. Consequently, the present study investigates for the first time the concentrations of heavy metals and persistent organic pollutants (organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs)) in river, estuary, and marine sediments from this area. The results highlighted high concentrations of Cr, Zn, As, and Pb exceeding the probable effect level (PEL) on aquatic life. Zn was the most dominant element detected at a range of 180-480 mg kg^-1 in marine sediment, 132-382 mg kg^-1 in estuary sediment, and 121-687 mg kg^-1 in river sediment. Total PCBs (∑7 × 4.3) ranged from 1995 to 20,156 μg kg^-1, 2013-12,058 μg kg^-1, and 1861-36,417 μg kg^-1 in marine, estuary, and river sediments, respectively. Total PCBs (∑7 × 4.3) were above PEL for all sediments, suggesting potential adverse effects on benthic organisms. The OCP, PBDE, and PAH levels were low to moderate for all sediments. Taking into consideration, the concentrations of Zn, Pb, PCBs, and DDTs, probable environmental risks, are present.

Contribution of heavy metal in driving microbial distribution in a eutrophic river

Urban rivers represent an important source of freshwater. Accelerated urban development has resulted in imbalances in the water ecological environment and even eutrophication. Moreover, both natural and anthropogenic sources result in frequent heavy metal pollution in urban rivers. However, the combined impact of eutrophication and heavy metal pollution on the diversity and structure of the river microbial communities has not been adequately addressed. The microbial community distribution and predicted functions were examined in six water and sediment samples from the Laojingshui (LJS) River using metagenomic sequencing. The results showed that there were distinct differences in the microbial composition along the river. Redundancy analysis (RDA) revealed that the redox potential (Eh) was the most influential factor, explaining 76.5% of the variation (p = 0.002), and the heavy metals Zn and Cu explained 4.5 and 3.9%, respectively (p < 0.05). The results revealed that high nitrogen and phosphorus concentrations may have affected the proliferation of opportunistic plant species, such as Eichhornia crassipes, but Eh and heavy metals may have had greater impacts than N and P on the microorganisms in the water and sediment. The sensitivities of Deltaproteobacteria, Acidobacteria, Gemmatimonadetes and Nitrospira were most significant under Zn and Cu contamination when accompanied by eutrophic conditions. The expression ratio of the CYS (Cystain) gene might explain why the spatial distribution of each metal differed. This study suggests that heavy metals in eutrophication water continue to be the main factors determining the composition of microbial community, so the treatment of eutrophic water still needs to attach great importance to the complex pollution of heavy metals.

Occurrence and treatment of contaminants of emerging concern in the African aquatic environment: Literature review and a look ahead

Awareness about the rising detection and reported (eco)toxicological effects of contaminants of emerging concern (CECs, e.g. pharmaceuticals and personal care products - PPCPs - and modern pesticides) in the aquatic environment is growing. CECs are increasingly reported in the African aquatic environment, although the amount of data available is still limited. In this work, a comprehensive review is presented on the occurrence of CECs in wastewater, sludge, surface water, sediment, groundwater and drinking water of Africa. Further attention is given to the performance of wastewater stabilization ponds (WSPs) and trickling filters (TF) with respect to CECs removal. For the first time, we also look at the state of knowledge on the performance of point-of-use technologies (POUs) regarding the removal of CECs in drinking water. Generally, CECs in Africa occur at the same order of magnitude as in the Western world. However, for particular groups of compounds and at specific locations such as informal settlements, clearly higher concentrations are reported in Africa. Whereas antiretroviral and antimalarial drugs are rarely detected in the Western world, occurrence patterns in Africa reveal concentrations up to >100 μg L^-1. Removal efficiencies of WSPs and TFs focus mainly on PPCPs and vary significantly, ranging from no removal (e.g. carbamazepine) to better than 99.9% (e.g. paracetamol). Despite the rising adoption of POUs, limited but promising information is available on their performance regarding CECs treatment in drinking water, particularly for the low-cost devices (e.g. ceramic filters and solar disinfection - SODIS) being adopted in Africa and other developing countries.

Influence of Human Activities on Broad-Scale Estuarine-Marine Habitats Using Omics-Based Approaches Applied to Marine Sediments

Rapid urban expansion and increased human activities have led to the progressive deterioration of many marine ecosystems. The diverse microbial communities that inhabit these ecosystems are believed to influence large-scale geochemical processes and, as such, analyzing their composition and functional metabolism can be a means to assessing an ecosystem’s resilience to physical and chemical perturbations, or at the very least provide baseline information and insight into future research needs. Here we show the utilization of organic and inorganic contaminant screening coupled with metabolomics and bacterial 16S rRNA gene sequencing to assess the microbial community structure of marine sediments and their functional metabolic output. The sediments collected from Moreton Bay (Queensland, Australia) contained low levels of organic and inorganic contaminants, typically below guideline levels. The sequencing dataset suggest that sulfur and nitrite reduction, dehalogenation, ammonia oxidation, and xylan degradation were the major metabolic functions. The community metabolites suggest a level of functional homogeneity down the 40-cm core depth sampled, with sediment habitat identified as a significant driver for metabolic differences. The communities present in river and sandy channel samples were found to be the most active, with the river habitats likely to be dominated by photoheterotrophs that utilized carbohydrates, fatty acids and alcohols as well as reduce nitrates to release atmospheric nitrogen and oxidize sulfur. Bioturbated mud habitats showed overlapping faunal activity between riverine and sandy ecosystems. Nitrogen-fixing bacteria and lignin-degrading bacteria were most abundant in the sandy channel and bioturbated mud, respectively. The use of omics-based approaches provide greater insight into the functional metabolism of these impacted habitats, extending beyond discrete monitoring to encompassing whole community profiling that represents true phenotypical outputs. Ongoing omics-based monitoring that focuses on more targeted pathway analyses is recommended in order to quantify the flux changes within these systems and establish variations from these baseline measurements.

Deriving aquatic life criteria for galaxolide (HHCB) and ecological risk assessment

The polycyclic musk galaxolide (HHCB) is widely used as fragrances in personal care products (PCPs) and has been detected in various environmental media. There is an urgent need to derive aquatic life criteria (ALC) of HHCB for the protection of aquatic organisms. Toxicity tests with 8 Chinese resident aquatic organisms from 3 phyla and 8 families were conducted, and three methods were used for deriving the ALC. A criterion maximum concentration (CMC) of 8.33 μg/L and a criterion continuous concentration (CCC) of 2.20 μg/L were derived according to the USEPA guidelines. The acute predicted no effect concentrations (PNECs) values derived by log-normal species sensitivity distribution (SSD) and log-logistic SSD method were 77.41 and 66.47 μg/L, respectively. In addition, a significant sensitivity difference was observed between the planktonic crustacean and benthic crustacean, and there was no significant difference (p > 0.05) among SSDs based on resident and non-resident species. A comparison of chronic SSDs between HHCB, tonalide (AHTN) and musk ketone (MK) showed that nitro musk (MK) was more toxic to aquatic organisms than polycyclic musks (HHCB and AHTN). Finally, an assessment of risk to aquatic organisms in surface waters and effluents of wastewater treatment plants (WWTPs) worldwide showed that potential risk may exist at several locations. HHCB concentrations in 4.08 and 46.17% of the WWTP effluents in China and 1.71 and 16.13% of the WWTP effluents in other countries exceed the hazard concentration for 5% and 1% aquatic species.

Occurrence, distribution and ecological risk of trace metals and organic pollutants in surface sediments from a Southeastern European river (Someşu Mic River, Romania)

The increasing contamination of fresh water resources by trace metals and persistent organic pollutants is a major environmental concern. In the present study, we investigated, for the first time, the distribution, sources and ecological risk of trace metals and organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), in surface sediments from a Southeastern European river (Someşu Mic River, Romania). Concentrations of Cd, Cr, Cu, Pb, Ni and Zn ranged from 0.04 to 0.4, 9.4 to 43.15, 7.2 to 65.6, 12.3 to 131.4, 14.7 to 47.7 and 42.1 to 236.8 mg kg^-1 dw, respectively. Concentrations of total PAHs, PCBs and OCPs ranged from 24.8 to 575.6, 2.7 to 252.7 and 2.1 to 44.3 ng g^-1 dw, respectively. Some sediment parameters, i.e., pH, total organic carbon (TOC) and total organic matter (OM) contents, played a significant role in the spatial distribution of contaminants. A combined analysis based on diagnostic ratios and multivariate analyses revealed PAHs originating mainly from pyrolytic sources. PCB compositions showed distinct contamination signatures for tri- to tetra-chlorinated PCBs, characteristic of contamination by Aroclor-1016 and -1254 technical mixtures. The dominant OCP congeners were α-HCH and p,p'-DDD, reflecting past use of technical HCHs and DDTs in agricultural practices. Metal source and pollution status was assessed using geoaccumulation index and enrichment factor, which indicate widespread pollution by Pb, Cd, Zn, Ni and Cu. The use of Sediments Quality Guidelines (SQGs), mean effect range-median quotient (m-ERM-Q) and toxic equivalent factor (TEF) indicated that the highest ecological risks occurred for PCBs and DDTs. This work presents not only initial baseline information on the extent of organic and inorganic contaminations in a river of ecological and economical interest, but also provides a diagnostic ratio/statistical combined approach that can be used to evaluate sediment quality in similar environments.

Where has the pollution gone? A survey of organic contaminants in Ho Chi Minh city / Saigon River (Vietnam) bed sediments

A wide range of persistent organic chemicals, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), some insecticides, as well as polybrominated diphenyl ethers (PBDEs) and some perfluoroalkyl substances (PFASs) were analyzed in 17 bed sediments collected along the Saigon River and at adjacent canal mouths from upstream to downstream in Ho Chi Minh City (Vietnam). Concentrations were rather low for PAHs, as well as for legacy PCBs and dichloro-diphenyl-trichlorethane and metabolites (DDTs), or below detection limits for several PFASs and all PBDEs measured. Several insecticides (chlorpyrifos-ethyl, and the pyrethroids cypermethrin and λ-cyhalothrin) displayed rather high concentrations at a few sites within the city. There was no distinct upstream - downstream trend for PAHs, (DDTs) or PCBs. Although adjacent canal sediments tended to be more contaminated than Saigon River sediments, the differences were not significant. Emissions are almost certainly substantial for PAHs, and probably also for other contaminants such as PBDEs and some PFASs. During the dry season, contaminants are presumably stored in the city, either in canals or on urban surfaces. Heavy rainfall during the monsoon period carries away contaminated particle flows into the canals and then the Saigon River. The strong tidal influence in the river channel hinders the accumulation of contaminated particles. Contaminated deposits should accordingly be investigated further downstream in depositional environments, such as the mangrove.

Historical Pollution of an Urban Watershed Based in Geochemical, Geoacumulation, and EROD Activity in PLHC-1 Analyses in Sediment Cores

In the present study, the environmental changes over the past 100 years in the Cambé River watershed in Southern Brazil were investigated. For this, a sediment core was collected to examine the distribution of metals, polycyclic aromatic hydrocarbons (PAHs), and ecotoxicological markers. The core corresponds from 1914 to 2012, which was obtained by the decay of ²¹⁰Pb. Changes in the study area also were examined by: Geoaccumulation index (Igeo) and enrichment factor (EF), sediment quality guidelines (SGQs), and ethoxyresorufin-O-deethylase (EROD) activity in Poeciliopsis lucida hepatocellular carcinoma (PLHC-1) cells line. The Σ16 PAHs ranged from 242.6 to 40,775 ng g^-1, with pyrogenic source at the beginning of the core, which likely corresponds to the burning of forests to establish the city and the later use of fossil fuels from 1960 to 2012. In the 1930s, most of metals presented a concentration below the background. After the 1930s, high concentrations can be associated with the intense use of fertilizers (Cd, Cu, Zn, Hg) and increases in urban traffic (Zn and Pb). Igeo showed that the distribution of Cu is considered moderately to strongly polluted, and the EF of Pb was considered as moderately polluted. Statistical analyses showed a strong relation between the presence of the ANP, FLU, PHE, BaP, IND, and Bghi compounds and the induction of EROD activity, and no correlation with heavy metals. A prediction model for the linear regression was obtained between the ANP and BaP concentrations and the EROD activity, with an accuracy of 99%.

Deriving aquatic life criteria for PBDEs in China and comparison of species sensitivity distribution with TBBPA and HBCD

Polybrominated diphenyl ethers (PBDEs) are important industrial brominated flame retardants. PBDEs have raised great concerns for their persistence, bioaccumulation, and harm to aquatic life and human health. Pentabromodiphenyl ether (PeBDE), octabromodiphenyl ether (OcBDE), and decabromodiphenyl ether (DeBDE) are three main commercial PBDEs congeners. In this study, published ecotoxicity data of these three PBDEs congeners for Chinese freshwater species were collected, and several acute and chronic toxicity tests for the three PBDEs congeners were performed. Using the derivation method for aquatic life criteria developed by the United States Environmental Protection Agency (USEPA), we determined that the criterion maximum concentration (CMC) for PeBDE, OcBDE and DeBDE for protection of freshwater organisms were 0.0492 mg/L, 0.197 mg/L and 0.239 mg/L, respectively. The criterion continuous concentration (CCC) for PeBDE, OcBDE and DeBDE were 0.0103 mg/L, 0.0224 mg/L and 0.0267 mg/L, respectively. The results provided a good reference for the derivation of PBDEs' water quality criteria and a basis for ecological risk assessment of PBDEs. In addition, the results of species sensitivity distribution comparison showed that the toxicity rank of five brominated flame retardants was TBBPA > PeBDE > OcBDE > DeBDE > HBCD.

Distribution and source analysis of heavy metal pollutants in sediments of a rapid developing urban river system

Heavy metal pollution of aquatic environments in rapidly developing industrial regions is of considerable global concern due to its potential to cause serious harm to aquatic ecosystems and human health. This study assessed heavy metal contamination of sediments in a highly industrialized urban watershed of eastern China containing several historically unregulated manufacturing enterprises. Total concentrations and solid-phase fractionation of Cu, Zn, Pb, Cr and Cd were investigated for 39 river sediments using multivariate statistical analysis and geographically weighted regression (GWR) methods to quantitatively examine the relationship between land use and heavy metal pollution at the watershed scale. Results showed distinct spatial patterns of heavy metal contamination within the watershed, such as higher concentrations of Zn, Pb and Cd in the southwest and higher Cu concentration in the east, indicating links to specific pollution sources within the watershed. Correlation and PCA analyses revealed that Zn, Pb and Cd were dominantly contributed by anthropogenic activities; Cu originated from both industrial and agricultural sources; and Cr has been altered by recent pollution control strategies. The GWR model indicated that several heavy metal fractions were strongly correlated with industrial land proportion and this correlation varied with the level of industrialization as demonstrated by variations in local GWR R² values. This study provides important information for assessing heavy metal contaminated areas, identifying heavy metal pollutant sources, and developing regional-scale remediation strategies.

Role of fluoranthene and pyrene associated with suspended particles in their bioaccumulation by zebrafish (Danio rerio)

Hydrophobic organic compounds (HOCs) tend to be associated with suspended particles in surface aquatic systems, however, the bioavailability of HOCs on suspended particles to fish is not well understood. In this study, a passive dosing device was used to control the freely dissolved concentrations (C_free) of polycyclic aromatic hydrocarbons (PAHs) including fluoranthene and pyrene, and the influence of particle-associated PAHs on their bioaccumulation by zebrafish was investigated. The results showed that, when the C_free of PAHs were kept constant, the presence of suspended particles did not significantly affect the steady state of PAH bioaccumulation in zebrafish tissues excluding head and digestive tracts, suggesting that the bioaccumulation steady state was controlled by the freely dissolved concentrations of PAHs. However, suspended particles promoted the uptake and elimination rate constants of PAHs in zebrafish body excluding head and digestive tracts. The uptake rate constants with 0.5 g/L suspended particles were approximately twice of those without suspended particles, and the body burden in zebrafish increased by 16.4% - 109.3% for pyrene and 21.8% - 490.4% for fluoranthene during the first 8-d exposure. This was due to the reasons that suspended particles could be ingested, and part of PAHs associated with them could be desorbed in digestive tract and absorbed by the zebfrafish, leading to the enhancement of uptake rates of PAHs in zebfrafish. The findings obtained from this study indicate that PAHs on suspended particles are partly bioavailable to zebrafish and particle ingestion is an important route in PAH bioaccumulation. Therefore, it is important to consider the bioavailability of HOCs on suspended particles to improve ecological risk assessment.

Construction of a Self-Powered System for Simultaneous In Situ Remediation of Nitrate and Cr(VI) Contaminated Synthetic Groundwater and River Sediment

A novel self-powered system was constructed to in situ remove nitrate and Cr(VI) from synthetic groundwater and achieve river sediment remediation simultaneously. The sediment organic matter in an anodic chamber was used as a carbon source to provide self-powered energy to reduce the cathode’s contaminants. With the acceptance of protons and electrons, nitrate and Cr(VI) were transformed into nitrite and Cr(III), respectively. In a 72 h test with both nitrate and Cr(VI) present, nitrate was removed at a rate of 70.96 mg/m3·h and Cr(VI) at a rate of 8.95 mg/m3·h. When a phosphate buffer was used in the test, their removal rates were changed to 140.83 mg/m3·h and 8.33 mg/m3·h, respectively. The results showed that the self-powered system could achieve the simultaneous reduction of nitrate and Cr(VI), although the presence of Cr(VI) hindered nitrate reduction. This system could realize simultaneous in situ groundwater and sediment remediation, with no need for additional energy or materials.

Seasonal metabolic analysis of marine sediments collected from Moreton Bay in South East Queensland, Australia, using a multi-omics-based approach

Anthropogenic effects of urban density have altered natural ecosystems. Such changes include eutrophication of freshwater and adjoining coastal habitats, and increased levels of inorganic nutrients and pollutants into waterways. In Australia, these changes are intensified by large-scale ocean-atmospheric events, leading to considerable abiotic stress on the natural flora and fauna. Bacterial communities in marine sediments from Moreton Bay (South East Queensland, Australia) were examined in order to assess the impact of rainfall changes, chemical pollution, and subsequent abiotic stress on living organisms within a marine ecosystem. Sediments were collected during the wet and dry seasons and analyzed using bacterial metagenomics and community metabolomics techniques. Physicochemical data were also analyzed to account for biological variance that may be due to non-rainfall-based abiotic stresses. Wet-dry seasonality was the dominant control on bacterial community structure and metabolic function. Changes in the availability of nutrients, organic matter and light appeared to be the major seasonal stressors. In contrast, urban and industrial pollutants appeared to be minor stressors at the sites sampled. During the wet season, the bacterial community composition reflected organisms that utilize biogeochemical pathways with fast kinetics, such as aerobic metabolism, direct assimilation of inorganic compounds, and primary production. The transition to the dry season saw the bacterial community composition shift towards organisms that utilize more complex organic energy sources, such as carbohydrates and fatty acids, and anaerobic redox processes.

High contamination in the areas surrounding abandoned mines and mining activities: An impact assessment of the Dilala, Luilu and Mpingiri Rivers, Democratic Republic of the Congo

Abandoned mines and mining activities constitute important sources of toxic metals and Rare Earth Elements (REEs) affecting surrounding environmental compartments and biota. This study investigates the contamination degree and distribution of toxic metals and REEs in contrasting sediment, soil and plant samples surrounding rivers in the African copperbelt area characterized by the presence of numerous abandoned mines, artisanal and industrial mining activities. ICP-MS results highlighted the highest concentration of Cu, Co and Pb in sediments reaching values of 146,801, 18,434 and 899 mg kg^-1, respectively. In soil, the values of 175,859, 21,134 and 1164 mg kg^-1 were found for Cu, Co and Pb, respectively. These values are much higher than the sediment guidelines for the protection of aquatic life and international soil clean-up standards. Enrichment factor and geoaccumulation index results indicated important contribution of mining activities to the study sites pollution in addition to natural background. Highest metal accumulation in leaves of Phalaris arundinacea L., was observed, reaching values of 34,061, 5050 and 230 mg kg^-1 for Cu, Co, and Pb, respectively. The ∑REE concentration reached values of 2306, 733, 2796 mg kg^-1 in sediment, soil and plant samples, respectively. The above results were combined with geographical information including satellite imagery, hydrography and mining concessions. Maps were produced to present the results in a comprehensive and compelling visual format. The results will be disseminated through an innovative mapping online platform to simplify access to data and to facilitate dialogue between stakeholders.

A multi-omics based ecological analysis of coastal marine sediments from Gladstone, in Australia's Central Queensland, and Heron Island, a nearby fringing platform reef

The impact of anthropogenic factors arising from point and non-point pollution sources at a multi commodity marine port and its surrounding ecosystems were studied using sediment samples collected from a number of onshore (Gladstone Harbour and Facing Island) and offshore (Heron Island and Fitzroy Reefs) sites in Australia's Central Queensland. Sediment samples were analyzed for trace metals, organic carbon, polycyclic aromatic hydrocarbons (PAH), emerging chemicals of concern (ECC) and sterols. Similarly, the biological and biochemical interaction between the reef and its environment was analyzed by the multi-omic tools of next-generation sequencing characterization of the bacterial community and microbial community metabolic profiling. Overall, the trace elements were observed at the lower end of the Australian environmental guideline values at the offshore sites, while higher values were observed for the onshore locations Nickel and copper were observed above the high trigger value threshold at the onshore sites. The levels of PAH were below limits of detection across all sites. However, some of the ECC and sterols were observed at higher concentrations at both onshore and offshore locations, notably, the cholesterol family sterols and 17α-ethynylestradiol. Multi-omic analyses also indicated possible thermal and photo irradiation stressors on the bacterial communities at all the tested sites. The observed populations of γ-proteobacteria were found in combination with an increased pool of fatty acids that indicate fatty acid synthesis and utilisation of the intermediates of the shikimate pathways. This study demonstrates the value of applying a multi-omics approach for ecological assessments, in which a more detailed assessment of physical and chemical contaminants and their impact on the community bacterial biome is obtained.

Detection of Organochlorine Pesticides in Contaminated Marine Environments via Cyclodextrin-Promoted Fluorescence Modulation

The development of practical and robust detection methods for pesticides is an important research objective owing to the known toxicity, carcinogenicity, and environmental persistence of these compounds. Pesticides have been found in bodies of water that are located near areas where pesticides are commonly used and easily spread to beaches, lakes, and rivers; affect the species living in those waterways; and harm humans who come into contact with or eat fish from such water. Reported herein is the rapid, sensitive, and selective detection of four organochlorine pesticides in a variety of water sources across the state of Rhode Island using cyclodextrin-promoted fluorescence detection. This method relies on the ability of cyclodextrin to promote analyte-specific fluorescence modulation of a high quantum yield fluorophore when a pesticide is in close proximity, combined with subsequent array-based statistical analyses of the measurable changes in the emission signals. This system operates with high sensitivity (low micromolar detection limits), selectivity (100% differentiation between structurally similar analytes), and general applicability (for different water samples with varying salinity and pH as well as for different water temperatures).

Occurrence, ecological risk assessment, and spatio-temporal variation of polychlorinated biphenyls (PCBs) in water and sediments along River Ravi and its northern tributaries, Pakistan

Ecological risk assessment, spatio-temporal variation, and source apportionment of polychlorinated biphenyls (PCBs) were studied in surface sediments and water from River Ravi and its three northern tributaries (Nullah Deg, Nullah Basantar, and Nullah Bein) in Pakistan. In total, 35 PCB congeners were analyzed along 27 sampling stations in pre-monsoon and post-monsoon seasons. The ∑₃₅PCB concentration ranged from 1.06 to 95.76 ng/g (dw) in sediments and 1.94 to 11.66 ng/L in water samples, with hexa-CBs and tetra-CBs as most dominant homologs in sediments and water matrixes, respectively. The ∑₈DL-PCB levels were 0.33-22.13 ng/g (dw) and 0.16-1.95 ng/L in sediments and water samples, respectively. The WHO-toxic equivalent values were ranged from 1.18 × 10^-6 to 0.012 ng/L and 1.8 × 10^-6 to 0.031 ng/g in water and sediments matrixes, respectively. The ecological risk assessment indicates considerable potential ecological risk during pre-monsoon season ([Formula: see text] = 95.17) and moderate potential ecological risk during post-monsoon season ([Formula: see text] = 49.11). The industrial and urban releases were recognized as key ongoing sources for high PCB levels in environment. Therefore, we recommend more freshwater ecological studies to be conducted in the study area and firm regulatory initiatives are required to be taken in debt to the Stockholm Convention, 2001 to cop up with PCB contamination on emergency basis.