Cadmium In Sediments Research Articles

Assessment of biochar supported sulfidized iron-based nanoparticles for immobilization of cadmium in sediment: Effectiveness, contribution of iron reducing bacteria, and mechanism insight

Biochar supported sulfidized nanoscale zerovalent iron (S-nZVI-BC) has shown great potential for environmental remediation. However, the feasibility of S-nZVI-BC for the immobilization of cadmium (Cd) in sediment and concomitant ecological consequences remains unclear. Herein, this study systematically investigated the effectiveness, environmental impacts and mechanisms of S-nZVI-BC for remediating of Cd polluted sediment and evaluated the contribution of iron reducing bacteria (IRB) for Cd immobilization. The Cd immobilization by S-nZVI-BC was superior to nZVI, BC, nZVI-BC and S-nZVI, with a maximum residual percentage increasing by 56.93%, the leachability decreasing by 94.48% and the availability reducing by 88.25%. The sediment pH, Eh, dissolved organic carbon (DOC) and leaching Fe2+ played a vital role in Cd immobilization. Three enzyme activities (urease, sucrase, and cellulase) were enhanced after S-nZVI-BC treatment, suggesting an improvement in sediment quality. However, catalase activity decreased, possibly because of the influence of Fe2+ from S-nZVI-BC. The microbial community structure was changed and the abundance of some IRB was improved by S-nZVI-BC. The RT-qPCR results indicated that the absolute abundance of Clostridium (a typical IRB) increased by 1.66 log, which enhanced the iron cycle and Cd re-immobilization. The characterization results confirmed that Cd immobilization by S-nZVI-BC was achieved via adsorption, surface adsorption-complexation and precipitation. Therefore, S-nZVI-BC showed excellent Cd immobilization performance and long-term stability, being well adapted for the treatment of Cd polluted sediment.

Mitigating sediment cadmium contamination through combining PGPR Enterobacter ludwigii with the submerged macrophyte Vallisneria natans

Sediment cadmium contamination poses risks to aquatic ecosystems. Phytoremediation is an environmentally sustainable method to mitigate cadmium contamination. Submerged macrophytes are affected by cadmium stress, but plant growth-promoting rhizobacteria (PGPR) can restore the health status of submerged macrophytes. Herein, we aimed to reduce sediment cadmium concentration and reveal the mechanism by which the combined application of the PGPR Enterobacter ludwigii and the submerged macrophyte Vallisneria natans mitigates cadmium contamination. Sediment cadmium concentration decreased by 21.59% after submerged macrophytes were planted with PGPR, probably because the PGPR colonized the rhizosphere and roots of the macrophytes. The PGPR induced a 5.09-fold increase in submerged macrophyte biomass and enhanced plant antioxidant response to cadmium stress, as demonstrated by decreases in oxidative product levels (reactive oxygen species and malondialdehyde), which corresponded to shift in rhizosphere metabolism, notably in antioxidant defence systems (i.e., the peroxidation of linoleic acid into 9-hydroperoxy-10E,12Z-octadecadienoic acid) and in some amino acid metabolism pathways (i.e., arginine and proline). Additionally, PGPR mineralized carbon in the sediment to promote submerged macrophyte growth. Overall, PGPR mitigated sediment cadmium accumulation via a synergistic plantmicrobe mechanism. This work revealed the mechanism by which PGPR and submerged macrophytes control cadmium concentration in contaminated sediment.

Effect of molecular weight of humic acid on the release and chemical fraction of cadmium in sediments

Effect of molecular weight of humic acid on the release and chemical fraction of cadmium in sediments

Synergistic enhanced passivation of phosphorus and cadmium in sediment by Ca/Al co-modified biochar

Synergistic enhanced passivation of phosphorus and cadmium in sediment by Ca/Al co-modified biochar

Accumulation of Heavy Metals by Some Aquatic Macrophytes in Two Streams along the Tiko-Douala Highway, Cameroon

Aims: This study was aimed at determining the ecological health of two roadside streams across the Tiko-Douala highway, Cameroon, and investigating the phytoremediation potentials of dominant aquatic macrophytes within these streams.
 Study Design: Water, sediments, and aquatic plant samples were collected from Camp 7 and Moqouo streams, and analyzed for ammonium nitrogen, nitrate nitrogen, phosphates, magnesium, cadmium, and lead, including other relevant water quality parameters.
 Place and Duration of Study: In the Life Science Laboratory of the University of Buea, and Soil and Water Laboratory of the University of Dschang, Cameroon between June 2021 and June 2022.
 Methodology: Six water samples and six sediment samples were collected per stream, and two of the most dominant plant species (Pennisetum purpureum Schumach (Poaceae) and Dicanthelium clandestinum L. (Poaceae) from Camp 7, Commelina benghalensis L. (Commelinaceae) and Oldenlandia corymbosa L.(Rubiaceae) from Moqouo stream) were collected for heavy metal analysis. Heavy metal concentration and bioaccumulation factors were determined for each plant.
 
 Results: High concentrations of phosphates were recorded in Camp 7 (1.19 mg/L) and Moqouo (2.17 mg/L) streams. Dissolved oxygen levels were 0.69 mg/L and 0.80 mg/L in Camp 7 and Moqouo respectively. Sediment cadmium levels ranged from 0.33± 0.02 to 0.63± 0.16 mg/kg, and lead ranged from 0.34 ±0.03 to 0.37 ± 0.12 mg/kg in Moqouo and Camp 7 respectively. 
 Conclusion: The Mouqouo and Camp 7 streams are rich in phosphates and thus not suitable for drinking and irrigation. Cadmium and lead in stream water were within the permissible limits but sediments contained higher concentrations than water and therefore they could be released gradually into the water column. All plants in the study except (Dicanthelium cladestinum) accumulated cadmium and lead, and could be potential plants for the phytoremediation of these metals.

PERMODELAN SPASIAL PENCEMARAN LOGAM BERAT DI SUNGAI BERBEK KAWASAN INDUSTRI SIDOARJO

Berbek Industrial Area is the largest industrial area in Sidoarjo Regency. One of the environmental impacts of industrial activities is water quality. One of the water quality is pollution in the sediment. This study aims to map and analyze the pattern of the spatial distribution of cadmium in sediments which can provide information on distribution in the area and the potential impact of lead accumulation on the environment. The samples taken were sediments from rivers in the area of the Berbek industrial area, Waru District, Sidoarjo Regency. The method used is a survey and laboratory tests. The distribution pattern of lead content in the waters was carried out using spatial analysis by the Arcgis 10.1 program kriging interpolation method. The result of pollution with the highest cadmium content was in the Berbek Region, namely 1.36 ppm. The highest distribution of sediment cadmium content is in the Wadungasri area. The Wadungasri area is a dense industrial area.

Biogeochemical behaviour of cadmium in sediments and potential biological impact on mangroves under anthropogenic influence: A baseline survey from a protected nature reserve.

Cadmium is a toxic element and its effects are well understood for human health, but its biogeochemical behaviour is still poorly studied and understood in natural ecosystems. This work addresses knowledge gaps concerning its presence, biogeochemical behaviour and impacts in mangrove ecosystems. Through geochemical data and multivariate analysis (i.e., factor and cluster analysis) of data from mangroves of Isla del Carmen, one of the largest extents in Mexico we explored the biogeochemical behaviour of Cd, a potentially toxic element, to identify its anthropogenic sources and interactions with sediments. Pollution indices, including enrichment factor (EF), geo-accumulation index (Igeo), sediment quality guidelines (SQG) and toxicological studies were used to assess the biological impacts of Cd and infer the natural levels tolerated by mangrove trees that form the basis of this natural ecosystem. Our results highlighted that Cd accumulation is driven by interactions between organic matter (OM), sulphur and fine particles; whereas enrichment factor showed values of 6.9 (EF) and 3.5 (EF) associated with point sources and ranged between 2 and 2.9 (EF) in relation to non-point sources. Finally, our geochemical approach revealed that Cd enrichment originates from urban activities and from the poor management of urban residuals.

Effects of shipwrecks on spatiotemporal dynamics of metal/loids in sediments and seafood safety in the Bay of Bengal

Metal/loid pollution from shipwrecking activities has drawn significant concern due to their persistent threat to the marine ecosystem and human health. We investigated the spatiotemporal distribution, pollution characteristics, risks, sources, and potential impact of metal/loids in the sediments and seafood in the Bay of Bengal at nearby open beaching shipwrecking yards in Bangladesh. We collected 78 sediments and 208 seafood samples from the exposed and control sites from 2018 to 2020 during the dry and wet seasons. The concentrations of 16 elements, including cadmium, arsenic, lead, chromium, manganese, copper, zinc, iron, tin, antimony, nickel, cobalt, molybdenum, vanadium, selenium, and thallium were measured using validated inductively coupled plasma-mass spectrometry (ICP-MS) methods. Based on the pollution indices (enrichment factor, geoaccumulation index, pollution index, and pollution load index), lead, arsenic, cadmium, selenium, copper, zinc, and tin from the dry season showed higher contaminations compared to the wet and their concentrations were increased from 2018 to 2020 with seasonal fluctuations. Sediment cadmium and arsenic posed relatively higher and moderate ecological risks. Health risk analysis indicated that lead, cadmium, and inorganic arsenic (estimated) in seafood species pose a possible health threat to the general population. Further, there were possible ecological and health risks for the metal/loids in combination based on the ecological risk index in sediment and the hazard index in seafood, respectively. Source apportionment suggested that anthropogenic activities through uncontrolled shipwrecking operations over the last four decades were the largest polluting dominator, contributing 55–77% of the metal/loid concentrations. Therefore, the data may inform mitigation strategies for emission control at the shipwrecking yards to protect marine ecosystems and their local population.

The impact of river sand mining on remobilization of lead and cadmium in sediments – A case study of the Jialing River

Due to the fast pace of urbanization worldwide, industrial sand mining activities have imposed great pressure on the environment, and consequently, these activities have led to serious environmental problems in aquatic ecosystems. However, the current understanding of the effect of sand mining on heavy metal remobilization in river sediments remains incomplete. The present study employed sediment quality guidelines (SQGs) and the sequential extraction (SE) and diffusive gradients in thin films (DGT) techniques to comprehensively investigate the effect of sand mining on the remobilization process of heavy metals in the aquatic system of the Jialing River. The SQGs results indicated that stations (S1 to S4) with sand mining disturbance exhibited Pb and Cd accumulation in surface sediments. Both Ctotal-Pb (61.78–122.04 mg·kg−1) and Ctotal-Cd (0.85–3.96 mg·kg−1) were higher than CSQGI (60 mg·kg−1 for Pb and 0.5 mg·kg−1 for Cd) and TEC (35.8 mg·kg−1 for Pb and 0.99 mg·kg−1 for Cd) limitation in most of sand mining stations. Pb and Cd were mainly bounded in the acid-soluble/exchangeable fraction (F1) and oxidizable fraction (F3) of the surface sediments. At the four stations with sand mining disturbance, about 5–10 folds of DGT-labile Pb and Cd were released in deep sediments (−9 to −12 cm), and Pb and Cd exhibited a transport trend from the sediments into the overlying water, while the above phenomenon was not observed at the two stations without sand mining activities. Correlation analysis revealed that DGT-labile Pb and Cd were suitably correlated with the F1 and F3 fractions, indicating that the acid-soluble/exchangeable and oxidizable fractions were the main sources leading to Pb and Cd remobilization in the sediments. A potential mechanism explanation may be that (1) intense sediment stirring could result in remobilization of the weakly bound fraction, which is related to the contribution of the F1 fraction, and (2) Cd/Pb experienced a corelease process with sulfur due to O2 introduction (elevation of the dissolved oxygen level) attributed to sediment evacuation, which is related to the contribution of the F3 fraction. The above results suggested that sand mining in the Jialing River should be paid high attention to prevent heavy metal pollution in aquatic ecosystem.

The relationship between population attributes of the mud snail Amphibola crenata and sediment contamination: A multi-estuary assessment

This study assessed the potential of the New Zealand mud snail Amphibola crenata to act as a bioindicator of contaminated estuarine sediment. Seventeen sites with varying contaminant burdens were identified within six New Zealand regions. Attributes (population density, individual length distribution and individual dry weight condition index) were measured for field-collected A. crenata, and related to measurements of sediment trace metals and nutrients. Population density of the mud snail was relatively high in sites with elevated nutrients and organic matter. The length distribution of A. crenata showed significant regional and site-specific variations. Minimum, mean, and median shell length of A. crenata were positively correlated with sediment cadmium and zinc concentration. Overall, the sites were able to be distinguished by A. crenata population attributes and the sediment metal and nutrient content. These results suggest that A. crenata population information has potential value for assessing estuarine sediment metal and nutrient contamination.

Risk Assessment and Fractionation of Cadmium Contamination in Sediment of Saguling Lake in West Java Indonesia

This research focused on the speciation and distribution patterns of cadmium in surface sediment from Saguling Lake, which is located in the Upper Citarum River. Organic compounds and heavy metals from anthropogenic activities in the watershed have contaminated the river. Sample from the upper layer of the sediment from Saguling Lake were taken from 12 locations, representing the dry and the rainy seasons in the period 2015-2018. Sediment cadmium (Cd) classification was conducted through a sequential extraction technique to determine Cd’s bioavailability and its risk to the water environment. During the rainy season, the total Cd concentration in the upper layer of the sediment was higher than during the dry season. The average dry and rainy season concentrations were 11.12 ± 2.16 mg/kg and 14.82 ± 1.48 mg/kgm in the sampling locations, distributed differently with the following order of the largest to the smallest concentration: 10B > 1A > 4 > 3 > 2 > 1B > 10A > 7 > 9 > 5 > 6 > 8 for the dry season, and 4 > 1A > 1B > 2 > 7 > 5 > 9 > 3 > 6 > 10A > 8 > 10B for the rainy season. All sampling locations (>60%) showed Cd in the resistant fraction, indicating no significant anthropogenic input of Cd into the surface sediment but more geological input due to high erosion. The values of RAC, ICF, and GFC indicate that the Cd in the surface sediment can be categorized as low risk.

Ecogeochemical studies of the postindustrial sites of Minsk

In the article the results of studying the sites of industrial enterprises, which have stopped their activities fully or partially in Minsk, are discussed. It is shown that in most cases the re-development of industrial sites with a change of their functional purpose is carried out after 10 years or more. Based on the results of preliminary investigation of a number of the former industrial sites, it was established that such sites continue to be sources of pollutants after the completion of enterprises activity. The enrichment of technogenic substrates carried out from industrial sites by surface runoff (sediments near storm collectors and in topographic lows) with heavy metals is shown. The average content of cadmium in sediments is 2,6 (maximum – 3,9), lead – 3,1 (14), copper – 2,5 (2,2), zinc – 1,7 (2,8), nickel – 3,3 (8,0), chromium – 3,4 (6,6) times higher than in soils. The established standards for lead were exceeded in 63 % of cases, for cadmium – in 77 %, for zinc and copper – in 100 % of cases. The maximum permissible concentration was exceeded 5 times for at least one indicator in almost half of the samples (44 %). The dependence of heavy metals accumulation on the specialization of previously carried out industrial activities is shown. The need for improvement of scientific and methodological approaches to studying of contaminated and potentially contaminated post-industrial areas in connection with their planned re-profiling for urban planning purposes is discussed.

Assessment of cadmium concentration, bioavailability, and toxicity in sediments from Saguling reservoir, West Java Province

This study aims to assess the concentration, bioavailability, and toxicity of cadmium in sediments. Surface sediment samples were taken from 12 sampling locations during the rainy and dry seasons from 2015-2017. Cadmium concentrations were analyzed using ICP-OES. Potential ecological risk index (PERI) methods assess the quality of lake sediments concerning heavy metal contamination. Risk Assessment Code (RAC) is a method used to assess the bioavailability of metals in aquatic sediments. The concentration of cadmium in the sediments during the rainy and dry seasons is high compared to the standards. The average concentration in rainy season 14.82 ± 1.48 mg.kg-1 and dry season 11.12 ± 2.16 mg.kg-1. Based on the assessment of sediment quality is categorized as extremely polluted during the rainy and dry seasons. The sediment quality has been contaminated with cadmium with the serious ecological risk category in two seasons. This means that Cadmium pollution has had a serious impact on the reservoir ecosystem. The bioavailability of cadmium in the dry season is higher than in the rainy season. This suggests that in the dry season, cadmium is more bioavailable and more able to enter the food chain. The toxicity of cadmium is higher in the dry season.

Kandungan Logam Kadmium (Cd) pada Air Laut, Sedimen, dan Kerang Hijau di Perairan Tambak Lorok dan Perairan Morosari

Cadmium metal is dangerous for green mussel organisms because it can interfere with fertility. Green mussels are organisms widely distributed, can survive in poor environments, and sedentary organisms. Green shellfish is a filter feeder and is used as a bioindicator to monitor the concentration of Cd metal in the waters. The research objective was to measure the concentration of Cd metal in sea water, sediment, and green mussel meat in the waters of Tambak Lorok and Morosari. The Cd metal contents of seawater, sediments, and green mussels were measured using Atomic Absorption Spectrophotometer. The results showed that Cd metal concentrations in seawater in May, July, and August 2018 in Tambak Lorok and Morosari waters were below the detection limit (0.001mg/L); 0.002 mg/L; and 0.002 mg/L, respectively. The concentrations of cadmium in sediment in May, July, and August in Tambak Lorok waters were below the detection limit (0.004 mg/kg); 0.0023 mg/kg; and 0.0021 mg/kg, respectively, and in Morosari waters were below the detection limit (0.004 mg/kg); 0.002 mg/kg; and 0.0114 mg/kg, respectively. Cd metal concentrations in green mussel meats in May, July, and August in Tambak Lorok waters were below the detection limit (0.01mg/kg); 0.0060; and 0.1277 mg/kg, respectively, and in Morosari water were below the detection limit (0.01mg/kg); 0.0067 mg/kg; and 0.0493 mg/kg, respectively. Cd metal concentrations in sea water and green mussels in the waters of Tambak Lorok and Morosari were below the quality standard and the concentrations of Cd metal in seawater, sediments, and green mussel meat in the waters of Tambak Lorok and Morosari were not significantly different. Keywords: cadmium, green mussels, morosari, seawater, sediments, Tambak Lorok

Analysis of Heavy Metal Cadmium (Cd) Content on Mud Crab (<i>Scylla</i> sp.) at Wonorejo River Surabaya

The coastal waters of Wonorejo is part of the East Coast Surabaya which receive the brunt of watersheds (DAS) from other rivers. The main source of heavy metal wastes in the River on the downstream Wonorejo pass several industries suspected of disposing of hazardous waste. One of the main heavy metal which is a toxic element and effect on aquatic ecological systems are cadmium (Cd).Mud crab is one potential biota found in the mangrove area of Wonorejo River Surabaya can accumulate heavy metals. This research was carried out in April 2018 with sampling at three stations with time each week for three times.Analysis of heavy metals cadmium (Cd) in mud crabs ( Scylla sp.), water and sediments carried out in the laboratory of nutrition of the Faculty of public health University Airlangga. Research method using observation which is channeled in the waters and farmed in Wonorejo Surabaya. Mud crab meat samples, water and sediments tested using Atomic Absoption Spectrophotometry (AAS). The results of the test concentration of heavy metals cadmium (Cd) in mud crab meat on the river Wonorejo i.e. 0.032 mg.kg -1 where the value of these levels are still below the threshold of quality raw heavy metal Cd on crustaceans i.e. 1 mg.kg-1 (SNI 7387:2009). The Cd content in water of Wonorejo river in between 0.014-0.02 ppm and on sediments between 0.234-0.416 mg/kg. Correlation of cadmium content in water with crab meat in the correlation coefficient shows of Wonorejo -0.22 (a weak correlation, a negative direction). Then, the correlation of the content of cadmium in sediments with crab meat in the correlation coefficient shows of Wonorejo 0.285 (of correlation is weak, the positive direction).

Determination of cadmium in sediments by diluted HCI extraction and isotope dilution ICP-MS

Isotope dilution ICP-MS is proposed to measure the mass fraction of Cd extracted by diluted HCl in marine sediments, using a fast and simple extraction procedure based on ultrasonic probe agitation. The 111Cd isotope was added before the extraction to achieve isotope equilibration with native Cd solubilized from the sample. The parameters affecting trueness and precision of isotope ratio measurements were evaluated carefully and subsequently corrected in order to minimize errors; they were: detector dead time, spectral interferences, mass discrimination factor and optimum sample/spike ratio. The mass fraction of Cd extracted was compared with the sum of the certified contents of the three steps of the sequential extraction procedure of the Standards, Measurements and Testing Programme (SM&T) analysing the BCR 701 sediment to validate the method. The certified and measured values agreed, giving a measured / certified mass fraction ratio of 1.05. Further, the extraction procedure itself was studied by adding the enriched isotope after the extraction step, which allowed verifying that analyte losses occurred during this process. Two additional reference sediments with certified total cadmium contents were also analysed. The method provided very good precision (0.9%, RSD) and a low detection limit, 1.8 ng g−1. The procedural uncertainty budget was estimated following the EURACHEM Guide by means of the ‘GUM Workbench’ software, obtaining a relative expanded uncertainty of 1.5%. The procedure was applied to determine the bioaccessible mass fraction of Cd in sediments from two environmentally and economically important areas of Galicia (rias of Arousa and Vigo, NW of Spain).

Heavy metals in surficial sediments of the central Bohai Sea: their distribution, speciation and sources

The semi-enclosed Bohai Sea has received large amount of pollutants from surrounding rivers and sewage channels along the densely populated and industrializing Bohai coasts, as well as the offshore oil exploration in the sea. The concentrations of heavy metals copper, cobalt, nickel, zinc, lead, chromium and cadmium in 25 surface sediment samples from the central Bohai Sea are obtained by ICP-MS analysis. The speciation of these heavy metals is extracted and their distribution, fractionation, pollution status and sources are presented. High concentrations of copper, cobalt, nickel, zinc and chromium are found in the sediments off the coastal area of the Bohai Bay and the central Bohai Sea mud, while high concentrations of cadmium and lead are found in the sediments in the whole study area. The residual fraction is the dominant form of copper, cobalt, nickel, zinc and chromium in the surface sediments, while cadmium and lead have large proportions in the nonresidual fractions. The ecological risk assessment shows that the sediments in the study area are unpolluted with respect to the heavy metals of cobalt, nickel and chromium and unpolluted to moderately polluted with respect to copper, zinc, cadmium and lead. Cobalt, nickel and chromium mainly have natural origin and their concentrations significantly vary with the composition of the sediments. The contents of copper, zinc, lead and especially cadmium in sediments are suggested to be influenced by pollutants of human activities. The heavy metals in the surface sediments at most sampling stations are mainly come from the Huanghe River; the heavy metals in the sediments in the northernmost part of the study area are significantly affected by the sediment from the Luanhe River; while in the Bohai Bay and the central region they were affected by the sediment from the Haihe River and aerosol deposition.

Application of constrained mixture design and Doehlert matrix in the optimization of dispersive liquid-liquid microextraction assisted by ultrasound for preconcentration and determination of cadmium in sediment and water samples by FAAS

A dispersive liquid-liquid microextraction assisted by ultrasound (USADLLME) with 5-(4-Dimethylaminobenzylidene)Rhodanine procedure has been developed for preconcentration of cadmium in water and sediment samples by flame atomic absorption spectrometry (FAAS). The proportions of mixture composed of disperser, extractor solvents and complexing reagent was optimized using a constrained mixture design. The variables pH, concentration of NaCl and sonication time were optimized using a Doehlert matrix. The precision of method expressed as relative standard deviation (RSD) of 2.92 and 3.38% for 50 and 20μgL−1, respectively, the detection limit was 0.23μgL−1 and the limit of quantification of 0.76μgL−1. The accuracy was confirmed by the analysis of certified reference materials (Drinking Water Standard APS 1071, Fresh Water Sediment 3 RTC 016, Oyster Tissue NIST 1566b, Tomato Leaves NIST 1773a), the Spike test showed recoveries between 90 and 110%. The method was applied to river water, drinking water and sediment, the concentration of cadmium ranged from 1.46–4.60μgL−1 for water samples and from 0.90 to 1.23μgg−1 for sediment samples.

Molecular and phenotypic responses of Japanese medaka (Oryzias latipes) early life stages to environmental concentrations of cadmium in sediment.

Japanese medaka embryos were exposed to environmental concentrations of cadmium (Cd) to investigate adverse and adaptive responses in fish early life stages. Embryos were exposed during their whole development by static sediment-contact to environmental Cd concentrations (2 and 20μg/g dry weight). Cd bioaccumulation, developmental defects, biochemical and biomolecular (qRT-PCR) responses were analyzed in embryos and hatchlings. A dose-dependent increase of Cd bioaccumulation and developmental defects was observed at hatching. Cd had clear impacts on heartbeat and cardiac morphogenesis and also induced to spinal deformities. The profile and the level of gene transcription were differentially modulated according to the Cd concentration, the duration of exposure and/or the developmental stage of fish. Pro-apoptotic bax and DNA repair rad51 transcripts were significantly repressed in embryos exposed to the highest Cd concentration. Repression of these genes was correlated to the increase of heart rate in 6-day-old embryos. NADH-dehydrogenase nd5 gene transcription was inhibited in larvae at the lowest concentration suggesting mitochondrial respiratory chain impairment, in association with Cd-induced teratogenicity. Finally, wnt1 gene was overexpressed indicating putative deregulation of Wnt signaling pathway, and suggested to be implied in the occurrence of some spinal and cardiac deformities. Results of this study permitted to propose some promising markers at the transcriptional and phenotypical level, responding to environmental concentrations of Cd. The present work also highlights the usefulness of the modified version of the medaka embryo-larval assay with sediment-contact exposure (MELAc) to investigate the toxicity and the modes of action of sediment-bound pollutants.

Exposure–dose–response relationships of the freshwater bivalve Hyridella australis to cadmium spiked sediments

To understand how benthic biota may respond to the additive or antagonistic effects of metal mixtures in the environment it is first necessary to examine their responses to the individual metals. In this context, laboratory controlled single metal-spiked sediment toxicity tests are useful to assess this. The exposure–dose–response relationships of Hyridella australis to cadmium-spiked sediments were, therefore, investigated in laboratory microcosms. H. australis was exposed to individual cadmium spiked sediments (<0.05 (control), 4±0.3 (low) and 15±1 (high) μg/g dry mass) for 28 days. Dose was measured as cadmium accumulation in whole soft body and individual tissues at weekly intervals over the exposure period. Dose was further examined as sub-cellular localisation of cadmium in hepatopancreas tissues. The biological responses in terms of enzymatic and cellular biomarkers were measured in hepatopancreas tissues at day 28. H. australis accumulated cadmium from spiked sediments with an 8-fold (low exposure organisms) and 16-fold (high exposure organisms) increase at day 28 compared to control organisms. The accumulated tissue cadmium concentrations reflected the sediment cadmium exposure at day 28. Cadmium accumulation in high exposure organisms was inversely related to the tissue calcium concentrations. Gills of H. australis showed significantly higher cadmium accumulation than the other tissues. Accumulated cadmium in biologically active and biologically detoxified metal pools was not significantly different in cadmium exposed organisms, which suggests that H. australis has some tolerance to cadmium. The metallothionein like protein fraction played an important role in the sequestration and detoxification of cadmium and the amount sequestered in this fraction increased with increased cadmium exposure. The highest percentage of biologically active cadmium was associated with the lysosome+microsome and mitochondrial fractions. Cadmium concentrations in these two fractions of cadmium exposed organisms were significantly higher with respect to controls. Total antioxidant capacity decreased with increased cadmium exposure and tissue dose. Lipid peroxidation increased and lysosomal membrane stability decreased significantly with increased cadmium exposure and tissue dose. Based on exposure–dose–response analysis in this study, H. australis would be a suitable organism for assessing cadmium sediment exposure and toxicity.