Machine learning-based analysis of heavy metal contamination in Chinese lake basin sediments: Assessing influencing factors and policy implications.

Sediments are important heavy metal sinks in lakes, crucial for ensuring water environment safety. Existing studies mainly focused on well-studied lakes, leaving gaps in understanding pollution patterns in specific basins and influencing factors.We compiled comprehensive sediment contamination data from literature and public datasets, including hydro-geomorphological, climatic, soil, landscape, and anthropogenic factors. Using advanced machine learning, we analyzed typical pollution factors to infer potential sources and migration pathways of pollutants and predicted pollution levels in basins with limited data availability. Our analysis of pollutant distribution data revealed that Cd had the most extensive pollution range, with the most severe pollution occurring in the Huaihe and Yangtze River basins. Furthermore, we identified distinct groups of driving factors influencing various heavy metals. Cd, Cr, and Pb were primarily influenced by human activities, while Cu and Ni were affected by both anthropogenic and natural factors, and Zn tended more towards natural sources. Our predictions indicated that, in addition to the typical highly polluted areas, the potential risk of Cd, Cu and Ni is higher in Xinjiang, and in Tibet and Qinghai, the potential risk of Cd, Cr, Cu and Ni is higher. Pb and Zn presented lower risks, except in the Huaihe and Yangtze River Basins. Temperature, wind, precipitation, precipitation rate, and the cation exchange capacity of soil significantly impacted the predictions of heavy metal pollution in sediments, suggesting that particulate migration, rainfall runoff, and soil erosion are likely the main pathways for pollutant migration into sediments. Considering the migration, pathways, and sources of pollutants, we propose strategies such as low-impact development and promoting sustainable transportation to mitigate pollution. This study provides the latest insights into heavy metal pollution in Chinese lake sediments, offering references for policy-making and water resource management.

Soil erosion, sediment sources, connectivity and suspended sediment yields in UK temperate agricultural catchments: Discrepancies and reconciliation of field-based measurements.

Robust understanding of the fine-grained sediment cascades of temperate agricultural catchments is essential for supporting targeted management for addressing the widely reported sediment problem. Within the UK, many independent field-based measurements of soil erosion, sediment sources and catchment suspended sediment yields have been published. However, attempts to review and assess the compatibility of these measurements are limited. The data available suggest that landscape scale net soil erosion rates (∼38 t km-2 yr-1 for arable and ∼26 t km-2 yr-1 grassland) are comparable to the typical suspended sediment yield of a UK catchment (∼44 t km2 yr-1). This finding cannot, however, be reconciled easily with current prevailing knowledge that agricultural topsoils dominate sediment contributions to watercourses, and that catchment sediment delivery ratios are typically low. Channel bank erosion rates can be high at landscape scale (27 km-2 yr-1) and account for these discrepancies but would need to be the dominant sediment source in most catchments, which does not agree with a review of sediment sources for the UK made in the recent past. A simple and robust colour-based sediment source tracing method using hydrogen peroxide sample treatment is therefore used in fifteen catchments to investigate their key sediment sources. Only in two of the catchments are eroding arable fields likely to be important sediment sources, supporting the alternative hypothesis that bank erosion is likely to be the dominant source of sediment in many UK catchments. It is concluded that the existing lines of evidence on the individual components of the fine sediment cascade in temperate agricultural catchments in the UK are difficult to reconcile and run the risk of best management interventions being targeted inappropriately. Recommendations for future research to address paucities in measured erosion rates, sediment delivery ratios and suspended sediment yields, validate sediment source fingerprinting results, consider the sources of sediment-associated organic matter, and re-visit soil erosion and sediment cascade model parameterisation are therefore made.

Quantitative risk analysis of sediment heavy metals using the positive matrix factorization-based ecological risk index method: a case of the Kuye River, China.

Identifying the sources of heavy metals (HMs) in river sediments is crucial to effectively mitigate sediment HM pollution and control its associated ecological risks in coal-mining areas. In this study, ecological risks resulting from different pollution sources were evaluated using an integrated method combining the positive matrix factorization (PMF) and the potential ecological risk index (RI) model. A total of 59 sediment samples were collected from the Kuye River and analyzed for eight HMs (Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg). The obtained results showed that the sediment HM contents were higher than the corresponding soil background values in Shaanxi Province. The average sediment Hg content was 3.42 times higher than the corresponding background value. The PMF results indicated that HMs in the sediments were mainly derived from industrial, traffic, agricultural, and coal-mining sources. The RI values ranged from 26.15 to 483.70. Hg was the major contributor (75%) to the ecological risk in the vicinity of the Yanjiata Industrial Park. According to the PMF-based RI model, coal-mining activities exhibited the strongest impact on the river ecosystem (48.79%), followed, respectively, by traffic (34.41%), industrial (12.70%), and agricultural (4.10%) activities. These results indicated that the major anthropogenic sources contributing to the HM contents in the sediments are not necessarily those posing the greatest ecological risks. The proposed integrated approach in this study was useful in evaluating the ecological risks associated with different anthropogenic sources in the Kuye River, providing valuable suggestions for reducing sediment HM pollution and effectively protecting river ecosystems.

Oxygen micro-nanobubbles for mitigating eutrophication induced sediment pollution in freshwater bodies.

Sediment hypoxia is a growing problem and has negative ecological impacts on the aquatic ecosystem. Hypoxia can disturb the biodiversity and biogeochemical cycles of both phosphorus (P) and nitrogen (N) in water columns and sediments. Anthropogenic eutrophication and internal nutrient release from lakebed sediment accelerate hypoxia to form a dead zone. Thus, sediment hypoxia mitigation is necessary for ecological restoration and sustainable development. Conventional aeration practices to control sediment hypoxia, are not effective due to high cost, sediment disturbance and less sustainability. Owing to high solubility and stability, micro-nanobubbles (MNBs) offer several advantages over conventional water and wastewater treatment practices. Clay loaded oxygen micro-nanobubbles (OMNBs) can be delivered into deep water sediment by gravity and settling. Nanobubble technology provides a promising route for cost-effective oxygen delivery in large natural water systems. OMNBs also have the immense potential to manipulate biochemical pathways and microbial processes for remediating sediment pollution in natural waters. This review article aims to analyze recent trends employing OMNBs loaded materials to mitigate sediment hypoxia and subsequent pollution. The first part of the review highlights various minerals/materials used for the delivery of OMNBs into benthic sediments of freshwater bodies. Release of OMNBs at hypoxic sediment water interphase (SWI) can provide significant dissolved oxygen (DO) to remediate hypoxia induced sediment pollution Second part of the manuscript unveils the impacts of OMNBs on sediment pollutants (e.g., methylmercury, arsenic, and greenhouse gases) remediation and microbial processes for improved biogeochemical cycles. The review article will facilitate environmental engineers and ecologists to control sediment pollution along with ecological restoration.

Insights about levels and sources of organic pollution in an urbanized Amazon estuary (Belém, PA, Northern Brazil).

Amazon aquatic systems have been affected by organic pollution from urbanized regions. This study was conducted to determine the levels, sources, and distribution patterns of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 steroid markers in surficial sediments from an important urbanized Amazon estuarine system (Belém, PA, Northern Brazil). Total PAH concentration (∑PAH) ranged from 878.2 to 9905.7 ng g-1, 3295.2 ng g-1 on average, suggesting a highly contaminated environment. PAH molecular ratios and statistical analysis indicated that PAH originated from a mixture of local sources emissions, mainly related to the combustion of fossil fuels and biomass. Coprostanol levels (maximum concentration = 292.52 ng g-1) could be compared to the mid-range reported in the literature. Studied stations, except for one, presented sterol ratio data indicating organic matter related to untreated sewage. Sterols indicative of sewage contamination showed a correlation with pyrogenic PAH amounts which are transported by the same channels where sewage is discharged.

Water resources pollution associated with risks of heavy metals from Vatukoula Goldmine region, Fiji.

Although mining is essential for human economic development, is amongst the most polluting anthropogenic sources that influence seriously in water resources. Thus, understanding the presence and concentration of heavy metals in water and sediment in the vicinity of mines is important for the sustainability of the ecosystem. In this work, a multidisciplinary approach was developed to characterize the contamination level, source apportionment, co-existence, and degree of ecological and human health risks of HMs on water resources in the Vatukoula Goldmine region (VGR), Fiji. The outcomes suggested significant contamination by Cd (range: 0.01-0.95 g/L), Pb (range: 0.03-0.53 g/L), and Mn (range: 0.01-3.66 g/L) in water samples surpassed the level set by Fiji and international laws, whereas higher concentration of Cd (range: 2.60-23.16 mg/kg), Pb (range: 28.50-200.90 mg/kg) and Zn (range: 36.50-196.66 mg/kg) were detected in sediment samples. Lead demonstrated a strong significant co-existence network with other metals (e.g., Mn, Ni). Source apportionment recognized four source patterns (Cd, Pb, Ni, and Mn) for water and (Cr, Cd-Pb, Mn, and Zn) for sediment which was further confirmed by principal component analysis. The mine inputs source mainly contributed to Cd (66.07%) for water, while mineral processing mostly contributed to Zn (76.10%) for sediment. High non-carcinogenic (>1) and carcinogenic (>10-4) health risks, particularly in children, are related to the elevated Cd, Pb and Cr contents from the VGR. Uncertainty analysis demonstrates that the 90th quantile of Cd led to higher carcinogenic risk. Pollution indices disclosed a moderate to extremely contamination status mainly along the Toko dam which poses high ecological risks identified by index calculation. However, sediment quality indicators based on probable effect levels showed that there was a 75% of likelihood that the concentrations of Cd and Pb adjacent to the VGR have a severe toxic impact on aquatic lives.

Assessing pesticide, trace metal, and arsenic contamination in soils and dam sediments in a rapidly expanding horticultural area in Australia.

Industrial horticulture can release pesticides and trace metals/metalloids to terrestrial and aquatic environments. To assess long-term and more recent land contamination from an expanding horticultural region, we sampled soils from chemical mixing, crop production, and drainage areas, as well as retention reservoirs (dam) sediments, from 3 blueberry farms with varying land-use history in subtropical Australia. Soils were analysed for 97 different pesticides and trace metal/metalloid contents. The most recent farm had fungicides propiconazole and cyprodinil contents that may compromise soil invertebrate survival and/or nutrient recycling (5-125 mg kg-1). A site previously used to cultivate bananas had 6 dam sediment subsamples with arsenic contents over sediment quality guidelines (SQG); however, the soil content values were just below Australian health investigation levels (100 mg kg-1). Arsenic is suspected to originate from pesticide application during previous banana cultivation in the region. Dam sediment cores at all sites had mercury contents over the SQG likely due to fungicides or fertiliser impurities. Mean contents of mercury from dam sediments (141 ± 15.5 µg kg-1) were greater than terrestrial soils (78 ± 6.5 µg kg-1), and sediment profiles suggest mercury retention in anoxic sediments. Soils in chemical mixing areas at two sites were contaminated with copper and zinc which were above the national soil ecological investigation levels. Based on toxicity data, distribution, persistence, and mobility, we identified the fungicide cyprodinil, mercury, and phosphorus as contaminants of the greatest concern in this intensive horticulture area of Australia. Additional sampling (spatial, chemical speciation, biotic) is required to support mitigation efforts of the emerging contamination in the rapidly expanding blueberry farms of this region of Australia.

Anthropogenic influences on sedimentary geochemistry of Itapessoca Estuarine Complex, Pernambuco, Brazil.

The Itapessoca Estuarine Complex is characterized by a history of intense economic activities developed on the banks of its tributary rivers, often exercised without any control or planning. In order to relate natural and/or anthropic events to the sediment age, radiometric dating method was performed by determining excess 210Pb in the sediment using the proportional gas flow technique. To investigate possible disturbances in recent sedimentation processes in studied area, 20 surfaces sediment samples and 2 sediment cores were collected for determination of concentrations of the chemical elements. Al, Ca, Fe, K, Mg, Mn, Ni, Pb, Si, Sr, Ti and Zn concentrations were determined by the energy-dispersive X-ray fluorescence (EDXRF) technique. Through the enrichment factors and ratios among some elements associated with geochronological data, it was possible identify geochemical changes in sedimentation of sampled points, with increase of minerals associated with fine fractions and decrease of the proportions of elements associated with coarse fractions. The radiometric dating reveals that Pb enrichment and the exacerbated increase of Ca and Sr enrichment factors are strongly related to the anthropic activity in the region.

Trace element fractions in sediments of urbanised lakes of the arctic zone of Russia.

This paper presents the comprehensive evaluation of the level of accumulation of some of the most dangerous environmental pollutants (V, Co, Sn, Ni, Cr, Mn, Cd, Cu, Pb, Sb, Zn) and analyses their chemical forms in sediments of four small lakes located within Murmansk urban territory. Furthermore, the authors first studied morphology and chemical composition of industrial dust collected from the snow covering the ice of Lake Srednee. Fieldwork was carried out in April 2019. The results showed that sediments of the Murmansk urban lakes are significantly enriched in the content of the toxic metals and metalloids Cd, Pb, Sb, Zn, Cu, V, and Ni. An integrated assessment of anthropogenic impact using the pollution load index (PLI) and geoaccumulation index (Igeo) revealed a moderate to the extremely strong pollution level in recent sediment layers. The analysis of the fractions of the elements showed that they are mainly associated with stable compounds, such as primary minerals or persistent technogenic compounds (slag, matte, and dust). However, humic substances are a significant accumulative matrix for most studied elements. The share of the most mobile fractions does not exceed 30% for the vast majority of elements, even in the most polluted layers. The accumulation of the major part of pollutants can be attributed to the activities of the main industrial objects of the city (thermal power plant, coal port, transport infrastructure), and the impact of the global atmospheric transport of pollutants to the Arctic regions of Russia.

Assessment of mining activity on arsenic contamination in surface water and sediments in southwestern area of Santurbán paramo, Colombia.

The current emphasis of developing countries on policies that favor the intensification of mining exploitation as the main source of incomes, has generated negative consequences for ecosystems and rural communities, mainly due to the release of highly toxic elements into the environment. This study was carried out to evaluate the effect of the Vetas-California gold mining district on As distribution in stream sediments and surface water samples from Suratá River, located in the southwestern area of Santurbán paramo, Colombia. With this aim, samples distributed along the high Suratá River basin in areas near and far from mining areas were selected. Samples were chemically characterized. The As mobility, enrichment and sources were evaluated using sequential and single extractions, enrichment factor (EF), geoaccumulation index (Igeo), and hierarchical cluster analysis (HCA). The results highlight high As content (reaching up to 484 mg/kg) in stream sediment sampled near the gold mining district. For both sediment and water, the relative As content along the Suratá River exceeded the background content by 220 and 64.9 times, respectively. From the single-stage extractions performed, the reducible fractions found in As(NaOH) and As(HCl) were higher in all cases, meaning a high level of mobility and lixiviation of the As content in water samples by changes in pH and redox potentials. The correlations estimated using Spearman coefficients show that most of the bioavailable fraction of As(Exch) is related to main sediment constituents such as S, Fe2O3, SiO2, and Al2O3 and the relative As content. Calculation of the enrichment factor (EF) confirms high enrichments around active sites of gold mining such as the municipalities of Vetas, California and Matanza with EF values of 285, 204, and 133, respectively. In addition, the Igeo values suggest moderate to strong As pollution due to the high Igeo found at the major mining effect points. The findings from this study are valuable for providing effective management options for risk prevention and control of the persistent As accumulation in Santurbán paramo.

The ecological state of Boyuk Shor lake of Azerbaijan.

The article is devoted to the pollution problems and the identification of the main sources of pollution of Boyuk Shor lake of the Absheron Peninsula under the ever-increasing rate of industrial development and urbanization. The purpose of the research was to determine the current ecological state of Boyuk Shor lake and adjacent territories. For this purpose, in June-August 2018, 36 samples were taken for analysis from water, bottom sediments of the lake, and soils of adjacent territories. The laboratory analysis revealed a high content of total hydrocarbons, toxic metals (Cd, Co, Hg, Cu), suspended solids, and other pollutants in the lake water samples. Quantitative and qualitative indicators of the lake are presented. The number of suspended particles in water samples was found to be more than 27-250 times higher than the maximum permissible concentration, and the amount of Hg is 180-286 times, Cd is 1-3.3 times, Cu is 1.7-4.8 times, and Co is 1.5-2.4 times higher than MPC. The heavy metal pollution of the soil and the taxonomic composition of the mesofauna of the surrounding area of Boyuk Shor lake were also studied. It was found that the composition of the group of soil invertebrates is very scarce, consisting only of insects (Arthropoda) (85.7%) and mollusks (Mollusca) (14.3%). The research results showed that the long-term negative impact has led to a violation of the ecological balance of the lake; it has lost its natural qualities, has become unsuitable for the flora and fauna of the lake and the surrounding area, and needs thorough cleaning and restoration.

Geochemical anomalies for the determination of surface stream sediments pollution: case of Sierra de Cartagena-La Unión mining district, Spain.

This work explores the ability of the Spanish Geochemical Database to identify the existence of polluted stream sediments due to the presence of abandoned mine wastes. The mining district of Sierra de Cartagena-La Unión has been used as test area. A total of 18 abandoned tailings facilities were selected and samples were taken for analysis of the content in potential toxic elements. The results were contrasted with geochemical background values in order to identify which geochemical elements could entail anomalies potentially reflected in the Spanish Geochemical Database. For the study area, As, Cd, Pb, and Zn have been identified as potential toxic elements which can be used as geochemical indicators of sediment pollution processes originated in abandoned mine wastes. Furthermore, the correlation between Cd and Zn allows them to be considered as the best indicators of potential sediment contamination. The study of anomaly thresholds, through the analysis of accumulated frequencies of the contents of these elements in the sediments of the Spanish Geochemical Database, allows identifying sediments that may have been contaminated. A Mann-Whitney test contrasting the data of tailings, polluted sediments, and non-polluted sediments has been performed in order to verify differences among these types of samples. In addition, a geospatial analysis has demonstrated a very close relationship between contaminated sediments and the presence of mining wastes upstream. This methodology can be applied to any other mining region, to recognize the possible influence of pollution processes derived from the presence of abandoned mine wastes taking advantage of existing geochemical databases.

Quantitative assessment of metal contamination and associated pollution risk in sediments from the Mara River in Tanzania.

For most rivers in sub-Saharan Africa, information about pollution indices related to sediments is sparse. Sedimentological research of rivers that empty into Lake Victoria is highly patchy and wide apart. The present study determined the levels and associated risk of As, Cd, Cr, Hg, and Pb in sediments collected from four different sites along the Mara River that empties into Lake Victoria in Tanzania. Samples were collected in the dry and rainy months in 2019. Pollution indices, namely geo-accumulation index (Igeo), enrichment factor (EF), contamination factor (CF), modified contamination degree (mCd), pollution load index (PLI), potential ecological risk factor (Eri), and potential ecological risk index (RI) were used to evaluate the influence of heavy metal contamination in sediments. Dry month mean concentrations, in milligram per kilogram, of heavy metals were as follows: As (11.04 ± 0.13), Cr (1.02 ± 0.29), Cd (0.43 ± 0.05), and Hg (0.01) in the dry month. Respective sediment heavy metal concentrations for the rainy month were 22.22 ± 0.05 mg As/kg, 3.84 ± 0.34 mg Pb/kg, 1.53 ± 0.15 mg Cd/kg, 1.43 mg Cr/kg, and 0.03 mg Hg/kg. Generally, the risk indices showed high values in the rainy month and low values in the dry month, especially for As and Cd-an indication of anthropogenic influence. Correlation coefficient analysis for Pb and Cd showed a strong positive correlation (r = 0.99, p < 0.01)-this may suggest a similar source or similar transport behavior. Special attention needs to be paid with regard to rainy season As and Cd enrichment in the study area.

Multiple biomarker approach in the fiddler crab to assess anthropogenic pollution in tropical coastal environments.

CONTEXT: Fiddler crabs are important to the ecology of estuarine systems around the world, however, few studies have incorporated them as bioindicators. Urias estuary represents one of the most urbanized lagoons in the Gulf of California region and received discharges from different sources: shrimp farm, thermoelectric plant, fish processing plants, and untreated domestic and sewage wastes. OBJECTIVE: Assess the effects on anthropogenic contamination on female fiddler crabs reproduction, survival and genetic stability. METHODS: Exposition of wild crabs from a less impacted (reference) site to naturally contaminated sediments on under controlled laboratory conditions. Reproductive parameters, levels of DNA damage and mortality rates were measured, together with chemical analyses of sediments. RESULTS: The most contaminated sediments corresponded to the site where fish processing plants were located and the integrated biomarker response analysis revealed that the most adverse effects were produced by exposure to sediments from this site; these crabs showed higher mortality (67%) and poorer ovarian development than those crabs exposed to sediments from other sites. CONCLUSIONS: Female crabs under pollution stress are able to trade-off reproduction for survival, and surviving animals were able to restore genetic stability possibly by activating DNA repair mechanisms. Multiple biomarker approach discriminates different coastal contamination scenarios.

Quantifying pollutant loading from channel sources: Watershed-scale application of the River Erosion Model.

Phosphorus and fine sediment pollution are primary causes of water quality degradation. Streambank erosion is a potentially significant source of fine sediment and particulate phosphorus to watersheds, but it remains difficult to quantify the magnitude of this loading. A new, easily applied, watershed scale model was used to simulate the potential for future phosphorus and sediment loading from channel erosion in two watersheds: Big Dry Creek, Colorado and Lick Creek, North Carolina. The projected magnitude of loading for phosphorus is about an order of magnitude higher in Big Dry Creek compared to Lick Creek (∼280 kg/yr and ∼50 kg/yr, respectively), while sediment loading results are similar (∼950 ton/yr). In both watersheds, model results suggest that channel erosion will not contribute a significant amount of phosphorus to the watershed (∼1-4% of historic watershed total from all pollutant sources) but will contribute a large amount of sediment (30-100% of historic watershed total). Uncertainty in these estimates is high, but quantifying confidence in model projections is important for understanding and using model results. Importantly, modeling shows no decrease in loading over the 40-year model time frame in either watershed, suggesting that the channels are not adjusting to a new stable state and erosion will continue to be a pollutant source. Lick Creek model results are sensitive to upstream sediment supply while Big Dry Creek's are not, reinforcing the importance of considering alterations to both the hydrologic and sediment regimes when analyzing potential channel changes - at least in vertically active channels. This new modeling approach is useful for estimating historic and future phosphorus and sediment loading from channel erosion, an important first step in effective management to improve water quality.

Assessment of heavy metal contamination in surface sediments along the Mediterranean coast of Morocco.

In this paper, heavy metal contamination in surface sediments along the Mediterranean coast of Morocco was investigated. Determining pollution degree as well as heavy metal origins were the main objectives of this investigation. For this reason, concentrations of nine heavy metals (Cd, Cu, Cr, Ni, Pb, Zn, Hg, Fe, and Mn) were analyzed at ten stations sampled during three different periods. The obtained concentrations showed significant variation between sampling periods, which was controlled by several environmental and chemical processes. According to contamination indices results using pollution load index (PLI), modified contamination degree (mCd), geoaccumulation index (Igeo), enrichment factor (EF), and potential ecological risk index (RI), sampling stations were classified between uncontaminated and strongly contaminated without detecting any intense heavy metal pollution in surface sediment. Likewise, the EF values were comprised between no enrichment and moderate to severe enrichment. According to sediment quality guidelines, the calculated M-ERM-Q indicated that heavy metal mixtures have between 9 and 49% probability for being toxic. This result revealed lowest to medium-low potential of adverse effects to biota populations. Regarding heavy metal origins, multivariate statistical investigation showed that Cd, Cu, Hg, Pb, and Zn are derived mainly from anthropogenic activities, while Fe, Mn, Cr, and Ni were derived from natural sources. Despite Cd is considered as a typical anthropogenic metal, the very low concentrations obtained in this study support the involvement of natural factor in the enrichment with this metal. Therefore, the surface sediments contamination along the Mediterranean coasts of Morocco is particularly caused by a combination of anthropogenic and natural factors. As a result, the study area can be considered as not significantly enriched by human activities.

Vertebral column deformity in adult wild haddock (Melanogrammus aeglefinus).

This study describes radiological malformations in the vertebral column of adult sexually mature wild haddock, Melanogrammus aeglefinus collected from Masfjorden, Western Norway, in 2014 and 2015. There were seven deformed fish (33% of sampled fish), five with mild deformities and two with severe deformities. The deformity types discovered were lordosis, vertebra body asymmetry, compression, fusion (ankylosis), remodelling, and haemal spine hyperostosis. The two severely deformed fish were as follows: (a) one specimen with 29 deformed vertebrae within the region vertebrae nos. 1-30, including two sites of lordosis; (b) one specimen with 15 deformed vertebrae within the region vertebrae nos. 31-52 (most caudal vertebrae). The results of this study show that wild haddock can survive severe vertebra deformities, both in the trunk and tail region, and reach adulthood and sexual maturity. Whether normal nondeformed wild conspecifics would mate and spawn with these individuals and thereby complete the life cycle of the deformed individuals is, however, unknown. A possible link between bone fracture and fish hyperostosis is discussed.

Total and methyl mercury in the water, sediment, and fishes of Vembanad, a tropical backwater system in India.

Mercury contamination in the water bodies of developing countries is a serious concern due to its toxicity, persistence, and bioaccumulation. Vembanad, a tropical backwater lake situated at the southwest coast of India, is the largest Ramsar site in southern India. The lake supports thousands of people directly and indirectly through its resources and ecosystem services. It is highly polluted with toxic pollutants such as heavy metals, as it receives effluent discharges from Kerala's major industrial zone. In the present study, water, pore water, sediment, and fish samples collected from Vembanad Lake were analysed for total mercury (THg) and methyl mercury (MHg) contents. The maximum concentrations of THg and MHg in surface water samples were31.8 and 0.21 ng/L, respectively, and those in bottom water samples were 206 and 1.22 ng/L, respectively. Maximum concentration of THg in surface sediment was observed during monsoon season (2850 ng/g) followed by that in the pre-monsoon season (2730 ng/g) and the post-monsoon season (2140 ng/g). The highest sediment concentration of MHg (202.02 ng/g) was obtained during monsoon season. The spatial variation in the mercury contamination clearly indicates that the industrial discharge into the Periyar River is a major reason for pollution in the lake. The mercury pollution was found to be much higher in Vembanad Lake than in other wetlands in India. The bioaccumulation was high in carnivorous fishes, followed by benthic carnivores. The THg limit in fish for human consumption (0.5 mg/kg dry wt.) was exceeded for all fish species, except for Glossogobius guiris and Synaptura orientalis. The concentration of THg was five times higher in Megalops cyprinoides and four times higher in Gazza minuta. Significant variation was observed among species with different habits and habitats. Overall, risk assessment factors showed that the mercury levels in the edible fishes of Vembanad Lake can pose serious health impacts to the human population.

Modeling seasonal and spatial contamination of surface waters and upper sediments with trace metal elements across industrialized urban areas of the Seybouse watershed in North Africa.

Industrialization and urbanization are the main sources of pollutions worldwide and particularly in developing countries. This study aims the determination of anthropogenic inputs with trace metals in aquatic ecosystems at the Plain of Annaba (NE Algeria), which is known as one of the largest industrial areas in Africa. Samples of surface waters and upper sediments were conducted in six stations: four in Meboudja wadi and two in Seybouse wadi. Contents of iron, copper, chromium, nickel, zinc, and manganese were measured by atomic absorption spectrophotometry, whereas Cd and Pb were determined using electrothermal atomic absorption spectrometry. Measurements of Hg were carried out using atomic fluorescence. Spatiotemporal variations of metal concentrations were tested using generalized linear models (GLM), whereas the influence of water pollution on sediment contamination was tested with generalized additive models (GAMs). Metal contents measured in surface water and sediments varied differently from upstream to downstream of the study wadis and between seasons. The results showed that the surface water was polluted with high levels of iron, nickel, chromium, lead, and cadmium. Values of the contamination index revealed that the surface sediments were contaminated by iron, chromium, lead, and cadmium. The GAMs indicated that water-phase metal concentrations had no significant effects on trace metal concentrations in the sediment. This suggests that seasonal metal concentrations in water phase, which are measured during the study period (2012) and are time-dependent, contribute increasingly and gradually over time-not immediately-to the accumulation of metals into the sediments. Therefore, the long-term accumulation of metals in the sediments resulted from the continuous discharges of metals in the water phase. The anthropogenic impacts are marked by high contaminations of Meboudja wadi particularly in downstream areas of the steel factory and the nearby industrial areas. The direct industrial discharges into the water and atmosphere (iron, lead, cadmium) as well as urban disposals and agricultural activities are at the origin of these contaminations.

Sediment pollution characteristics and in situ control in a deep drinking water reservoir.

Sediment pollution characteristics, in situ sediment release potential, and in situ inhibition of sediment release were investigated in a drinking water reservoir. Results showed that organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) in sediments increased from the reservoir mouth to the main reservoir. Fraction analysis indicated that nitrogen in ion exchangeable form and NaOH-extractable P (Fe/Al-P) accounted for 43% and 26% of TN and TP in sediments of the main reservoir. The Risk Assessment Code for metal elements showed that Fe and Mn posed high to very high risk. The results of the in situ reactor experiment in the main reservoir showed the same trends as those observed in the natural state of the reservoir in 2011 and 2012; the maximum concentrations of total OC, TN, TP, Fe, and Mn reached 4.42mg/L, 3.33mg/L, 0.22mg/L, 2.56mg/L, and 0.61mg/L, respectively. An in situ sediment release inhibition technology, the water-lifting aerator, was utilized in the reservoir. The results of operating the water-lifting aerator indicated that sediment release was successfully inhibited and that OC, TN, TP, Fe, and Mn in surface sediment could be reduced by 13.25%, 15.23%, 14.10%, 5.32%, and 3.94%, respectively.