Cadmium In Sediments Research Articles

CONTENT OF CADMIUM (CD) AND LEAD (PB) IN SEDIMENTS AND ORGANISMS (GREEN MUSSEL PERNA VIRIDIS LINNAEUS AND OYSTER CRASSOSTREA GIGAS THUNBERG) AT VUNG THUNG, DA NANG CITY

Through 2 sampling times (March and August, 2011), the results of analyzing content of Cd and Pb in sedimentary samples indicated the signs of heavy metal pollution (Cd and Pb) in Vung Thung area, Da Nang city. Specifically, Cd content ranged from 0.54 to 1.58mg/kg (dry weight), some sediment samples was from 1.23 to 2.26 times higher than TEL (threshold effect level; < 0.7mg/kg dry weight) of ISQGs (Interim marine sediment quality guide-lines, Canada). Concerning to Pb, its content was in the range of 18.37 - 87.29mg/kg (dry weight), of which most samples were from 1.13 to 2.74 times as high as TEL (≤ 30.3mg/kg dry weight). In regards to heavy metal content in tissue of oyster and green mussel, cadmium content in both of two species was lower than standard (≤ 2mg/kg wet weight) of Ministry of Health (QCVN 8-2:2011/BYT), however, lead content accumulated in oyster is from 2.21 to 2.56 times higher than the allowed limit of Ministry of Health (≤ 1.5mg/kg wet weight), in green mussel was from 1.01 to 3.28 times as much as the allowed limit. The results from correlation analysis showed that the correlation between cadmium in sediment and in tissues of both species was weak, but Pb content in sediment correlated significantly with Pb content in tissues of both species, specifically, correlation coefficient was equal to 0.76 within oyster and 0.72 within green mussel. Indeed, oyster and green mussel can be used as bio - monitoring to evaluate lead pollution in marine environment.

CONTENT OF CADMIUM (CD) AND LEAD (PB) IN SEDIMENTS AND ORGANISMS (GREEN MUSSEL PERNA VIRIDIS LINNAEUS AND OYSTER CRASSOSTREA GIGAS THUNBERG) AT VUNG THUNG, DA NANG CITY

Through 2 sampling times (March and August, 2011), the results of analyzing content of Cd and Pb in sedimentary samples indicated the signs of heavy metal pollution (Cd and Pb) in Vung Thung area, Da Nang city. Specifically, Cd content ranged from 0.54 to 1.58mg/kg (dry weight), some sediment samples was from 1.23 to 2.26 times higher than TEL (threshold effect level; < 0.7mg/kg dry weight) of ISQGs (Interim marine sediment quality guide-lines, Canada). Concerning to Pb, its content was in the range of 18.37 - 87.29mg/kg (dry weight), of which most samples were from 1.13 to 2.74 times as high as TEL (≤ 30.3mg/kg dry weight). In regards to heavy metal content in tissue of oyster and green mussel, cadmium content in both of two species was lower than standard (≤ 2mg/kg wet weight) of Ministry of Health (QCVN 8-2:2011/BYT), however, lead content accumulated in oyster is from 2.21 to 2.56 times higher than the allowed limit of Ministry of Health (≤ 1.5mg/kg wet weight), in green mussel was from 1.01 to 3.28 times as much as the allowed limit. The results from correlation analysis showed that the correlation between cadmium in sediment and in tissues of both species was weak, but Pb content in sediment correlated significantly with Pb content in tissues of both species, specifically, correlation coefficient was equal to 0.76 within oyster and 0.72 within green mussel. Indeed, oyster and green mussel can be used as bio - monitoring to evaluate lead pollution in marine environment.

Exposure-dose-response of Tellina deltoidalis to metal-contaminated estuarine sediments: 1. Cadmium spiked sediments

Cadmium is a ubiquitous environmental metal contaminant with an affinity for biological membranes; it can enter cells by facilitated transport and it binds therein to various biomolecules and affects membrane system function. The relationship between cadmium exposure, dose and response was investigated in the benthic, deposit feeding, marine bivalve Tellina deltoidalis, using 28 day microcosm spiked cadmium exposures. Tissue cadmium reached steady state with the exposure concentration. Half the accumulated cadmium was detoxified and with increased exposure more was converted into metal rich granules. Most biologically active cadmium was in the mitochondrial fraction, with up to 7320-fold cadmium increases in exposed organisms. Cadmium exposed T. deltoidalis generally had reduced glutathione peroxidase enzyme activity. An increase in total glutathione concentrations, due to a build up of oxidised glutathione, was indicated by the reduced to oxidised glutathione ratio. All cadmium exposed T. deltoidalis had reduced total antioxidant capacity that corresponded with increased lipid peroxidation, lysosomal destabilisation and micronuclei frequency. Clear exposure-dose-response relationships have been demonstrated for T. deltoidalis exposed to cadmium-spiked sediments, supporting this organism's suitability for laboratory or in situ evaluation of sediment cadmium toxicity.

Exposure–dose–response of Anadara trapezia to metal contaminated estuarine sediments. 1. Cadmium spiked sediments

The relationship between cadmium exposure dose and response was investigated in Anadara trapezia exposed to cadmium spiked sediment (10μg/g and 50μg/g dry mass) for 56 days. A. trapezia reached an equilibrium cadmium tissue concentration (13μg/g and 25μg/g, respectively) by day 42. Gills accumulated significantly more cadmium than the hepatopancreas and haemolymph. After 56 days exposure between 46 and 73% of accumulated gill and hepatopancreas cadmium was detoxified and in the metallothionein like protein fraction. Approximately half of the biologically active cadmium in both tissues was in the mitochondrial fraction which has the potential to cause dysfunction in mitochondrial activity. Cadmium exposed A. trapezia generally had reduced GPx activity with an associated increase in total glutathione concentrations and reduced GSH:GSSG ratios due to a build up of oxidised glutathione. The changes in the glutathione pathway were reflected in the total antioxidant capacity of cadmium exposed A. trapezia which were significantly reduced compared to control organisms. There was a trend of increased lipid peroxidation with increased cadmium exposure but this was not significant. Increased cadmium exposure resulted in significant lysosomal destabilisation and increased frequency of micronuclei. The significant exposure–dose–response relationship for A. trapezia exposed to cadmium enriched sediments indicates that elevated sediment cadmium concentrations have the potential to lead to increased biologically active cadmium burdens and impairment of individual A. trapezia at cellular and subcellular levels.

Impact of Metals on Macroinvertebrate Assemblages in the Forgotten Stretch of the Rio Grande

The objective of this study was to examine how changes in the benthic macroinvertebrate community structure and a variety of abiotic variables, such as conductivity and sediment metal concentrations, are modified along the Forgotten River stretch of the Rio Grande. This stretch receives industrial effluent, raw sewage, and agricultural return flow from the El Paso (TX, USA)-Ciudad Juárez (CHI, Mexico) metroplex and then flows relatively undisturbed for 320 km before its next significant input. The high degree of use, followed by the 320-km undisturbed stretch, makes the Forgotten River a unique study site to examine downstream attenuation of contaminants and other abiotic variables to determine their potential effects on macroinvertebrates. Five different sites along the Forgotten Stretch were sampled over a 2-year period. Metal concentrations were low throughout the stretch and were predominantly correlated to percent sediment organic matter rather than explained spatially. Several sensitive invertebrate species, such as Leptophlebiidae, increased in relative abundance downstream, whereas the percentage of tolerant invertebrates decreased. Nonmetric multidimensional scaling separated the macroinvertebrate communities upstream from those downstream, with the more sensitive species being found predominantly downstream and more tolerant taxa associated upstream. Additionally, there was a distinct seasonal gradient to the community. The most important drivers of the community assemblage appear to be distance downstream and seasonality, as well as water conductivity and concentrations of sediment cadmium, which was the only metal that exceeded protective criteria. This study did not provide evidence of the downstream attenuation of heavy metals in the sediments in the Forgotten Stretch; however, downstream changes in macroinvertebrates toward more sensitive taxa suggests that other, unmeasured contaminants might be affecting biological communities in this isolated stretch of an international waterway.

Discharge and the response of biofilms to metal exposure in Mediterranean rivers

The expected response of fluvial biofilms to the environment and metal pollution prevailing under different discharge conditions was investigated. The relationship between inter-annual hydrological variability and metal concentration in water and sediments was explored in Mediterranean rivers (Catalonia, NE Spain) affected by low but chronic metal pollution, using monitoring data provided by the Catalan Water Agency (ACA). During the period investigated (2000–2006), metal pollution was characterized by low water concentrations and high concentrations in sediments. The most consistent pattern was observed for sediment cadmium (Cd) concentrations, showing a positive relationship with annual discharge, reaching values of environmental concern (above ecotoxicological benchmarks). A different pattern was observed for Cu, Zn, and As increasing with flow in some sites and decreasing in others. While Cd seems to proceed from diffuse sources being washed by surface runoff, Zn, Pb, and As may proceed from either diffuse or point-sources in the different river sites investigated. The relevance of diffuse metal pollution in the area of study indicates that polluted landfills runoff might be an important source of metals causing repetitive pulses of high metal concentration in the receiving water courses. The experimental results presented demonstrate that metal effects in fluvial biofilms may be accumulative, increasing the toxicity after repetitive pulse exposures. Since draughts and extreme rain events are expected to increase at higher latitudes due to global change, the sources of metal pollution, its final concentration and potential effects on the fluvial ecosystem may also change following the patterns expected for human-impacted Mediterranean rivers.

Cadmium in False Bay: Monitoring potential of the marine snail, Oxystele tigrina (Mollusca)

Cadmium contamination levels in the False Bay intertidal zone in South Africa were assessed in the water and sediments over a period of one year. Samples were collected seasonally from six sites within the bay, and from a reference site situated just outside the eastern arm of False Bay in order to obtain a general overview of contamination levels to which invertebrates in the coastal areas are exposed. The results from the chemical analyses of water and sediment samples revealed that most contamination was associated with the northern shore of the bay between Strand and Muizenberg, where the most populated and industrialised catchments occur. The high contamination factors calculated for Cd for sediments from some sites suggested a strong input of industrial and other discharges containing this heavy metal. There were signifi cant seasonal and spatial differences in the cadmium concentrations, with spatial variations indicating localised contamination, while seasonal variations were assumed to be predominantly related to changes in precipitation and runoff at different times of the year. The mean cadmium concentrations in the water and sediments were occasionally higher than the levels recommended by the South African Water Quality Guidelines, and indicated an increase in the levels compared to the previous water quality surveys. Laboratory experiments were conducted to examine the uptake, accumulation and loss of cadmium by the different organs of the periwinkle, Oxystele tigrina, from the False Bay intertidal zone. Tissue-specific cadmium accumulation in the control and exposed individuals were compared over a 14-day exposure period to sub-lethal concentrations (0.2 and 0.4 µg/ml) of water-borne cadmium in the form of CdCl2. The animals were sampled at regular intervals and the cadmium concentrations in the different organs measured by atomic absorption spectrophotometry. The results showed a general pattern of cadmium increase in the exposed individuals over a relatively short period. Cadmium was detected in all the tissues, with varying degrees of bioaccumulation. A more or less linear pattern of cadmium accumulation indicated that the metal was not regulated by O. tigrina. The metal was partitioned differently into the soft tissues and shells, with the soft tissues generally displaying a higher rate of cadmium uptake. There was a loss of the accumulated cadmium from the organs of the contaminated individuals upon transfer to clean seawater, with variations in the percentage of cadmium loss probably indicating that only part of the accumulated cadmium was firmly bound to the different tissues. The cadmium loss in the group that was exposed to 0.40µg/ml was not significant, indicating that the cadmium may have been more tightly bound in the tissues of this group compared to the group exposed to 0.20 µg/L. The amounts of cadmium in sediments and animal bodies in some parts of False Bay were such that cadmium could at current relatively low levels be expected to accumulate over time in these animals. Under changed physical conditions that may increase bioavailability, body levels could be reached that could affect the long term survival of this species and possibly its predators.

Cadmium partition in river sediments from an area affected by mining activities

In this paper, the cadmium distribution in Certej River sediments in an area seriously affected by intense mining activities has been studied. The main objective of this study was the evaluation of partition of this metal into different operational defined fractions by sequential extractions. Community Bureau of Reference (BCR) sequential extraction was used to isolate different fractions. The sediment quality was assessed both upstream and downstream the pollution input points, along the Certej River, in order to reveal a possible accumulation of cadmium in sediments and the seasonal changes in cadmium concentrations in BCR sediment phases. Our results reveal that most of the cadmium content is divided between both the soluble and iron and manganese hydrated oxide fractions. Based on total cadmium concentrations in sediments, the enrichment factors were estimated using aluminum as normalizing element and the regression curve Cd/Al corresponding to the geochemical background of the studied area.

Cadmium concentration in sea bottom sediment and its potential risk in the upper Gulf of Thailand

Untreated or partially treated waste water discharge from industrial and domestic sources entering the Upper Gulf of Thailand have been reported to increase cadmium concentration in bottom sediment. This study was directed at providing a better understanding of cadmium transformation in the sediment from the area. Sediment samples collected from Chao Phraya River mouth (CPY), Bang Pakong River mouth (BPK) and Klong Dan estuary (KD) located in the Upper Gulf of Thailand were analyzed for cadmium concentration in various sediment particle size fractions. Using laboratory microcosms, cadmium release from sediment as affected by salinity and sediment redox condition was studied. A higher concentration of cadmium (0.2–0.6 μ g/g dry weight) was measured in finer sediment particle size fractions (< 0.075 mm) as compared to courser fractions at all sampling stations. Cadmium release from the sediment to water was influenced by both salinity and redox condition. Sediment was spiked with 10 ppm cadmium which is the cadmium level in sediment adopted by the Australia and New Zealand sediment quality guidelines which can cause adverse environmental impacts. Experiments conducted showed soluble cadmium concentration at sediment oxidation reduction conditions representative of bottom sediment were at levels that can adversely impact aquatic organisms, according to the PCADMIUM water quality guideline. In Thailand, there is no sediment quality guideline. Based on these experiments, 10 ppm of cadmium in sediment was recommended as a regulatory guidelines for allowable levels of cadmium in sediment in the study area.

Levels of Cadmium in Soil, Sediment and Water Samples from Tarkwa and Its Environs

Soil, sediment and water samples collected from the catchment areas of some selected rivers and streams in Tarkwa and its environs were investigated for the levels of cadmium using the Atomic Absorption spectrophometric technique. From the results, it was observed that cadmium levels were generally higher than the WHO (1993) recommended level of 2.0 mgkg-1. Cadmium levels in soil ranged from 1.23 ±0.21 mgKg-1 at N3 to 4.63 ± 1.13 mgkg-1 at K1. Soil pHw ranged from 4.99 ±1.16mgKg-1 at Bn2 to 6.60 ±1.39mgKg-1 at K4. Cadmium in sediments were generally very high. It ranged from 2.40 ± 0.06 mgkg-1 at Bn1 to 8.64 ±1.76 mgkg-1 at K4. Sediment pHw ranged from 4.59 ±2.49 at N2 to 5.87 ± 0.23 at K4. Cadmium levels in water were also higher than the WHO (1993) standard value of 0.003 mgL-1. However, the pHs of the water samples were very close to the minimum standard value of 6.5.

Submerged macrophytes as bioindicators for pollution in Lake Mariut along the Mediterranean coast of Egypt

The fact that Lake Mariut is the only coastal lake in Egypt with no natural connection with the Mediterranean Sea has further aggravated the situation through the accumulation of pollutants in the lake. The effect of different pollutants on the composition and distribution of submerged aquatic plant communities in Lake Mariut (Egypt) was studied. Effects of heavy metals, nitrates, nitrites and phosphorus in the water and sediments on the dry weight standing crop (DWSC) of submerged macrophytes and their spatial distributions were investigated. Seven stations (which include 20 sites) were selected to represent the different pollution sources. The species-environmental data were analyzed using Canonical Correspondence Analysis (CCA). Only five submerged macrophytes species were recorded in Lake Mariut. There was an obvious variation in the DWSC of the species according to the pollution source. Potamogeton pectinatus and Ceratophyllum demersum were the best growing species with maximum DWSC, while C. muricatum, Myriophyllum spicatum and Najas marina subap. armata were weakly growing in most stations particularly the heavily polluted ones. The CCA ordination showed that dissolved nitrite, iron, phosphate, salinity and sulphate as well as sediment copper and cadmium are the most effective variables on the DWSC of these macrophytes. C. demersum is more developed in agricultural polluted areas with high levels of water phosphate and sulphate and low levels of water and sediment copper, chromium and lead. On the other hand, P. pectinatus characterizes the industrial polluted areas, with high level of sediment cadmium and low levels of water copper and chromium. These results were discussed and compared with other related studies.

Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO 3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp ( Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m 2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO 3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

Cadmium in the Water and Sediments of the Chao Phraya River and Associated Waterways, Bangkok, Thailand

As part of a research programme designed to examine the effect of cadmium on various biochemical responses in fish, a preliminary survey was carried out of cadmium concentrations in water and sediments sampled at 26 sites within the Chao Phraya River system in the Bangkok area of Thailand. Compared with values in the literature, the results of total cadmium analysis of both river water and sediments gave no indication of extreme pollution with cadmium, although two sites were identified with substantially higher than average sediment cadmium concentrations. More detailed sampling at these sites, over several months, compared with nearby `pristine' sites, confirmed their elevated cadmium status. The forms of cadmium present in the sediments at these sites, as determined by sequential fractionation, also provided evidence for the presence of contamination. However, considerable temporal variations in water and sediment cadmium concentrations were observed at individual sites, most probably related to seasonal high water levels and sediment flushing.

Determination of cadmium in sediments and in sewage sludge by slurry sampling electrothermal atomic absorption spectrometry using iridium as permanent modifier

A procedure for the determination of Cd in sediment and sewage sludge as slurries by electrothermal atomic absorption spectrometry is proposed. The slurry, 1 mg mL-1, was prepared by mixing sample ground to a particle size £ 50 mm with 5% v/v nitric acid in an ultrasonic bath. The homogeneity of the slurries was assured by passing a constant flow of argon into the autosampler cup, just before transferring an aliquot to the graphite furnace. Two permanent modifiers deposited on the platform were tested: Ru and Ir. Modifiers in solution were also tested: Pd plus Mg and phosphate alone or plus Mg. The Ir-treated tube was adopted due to its good performance as modifier and also for practical reasons. About 80% of Cd is extracted to the water phase of the slurry. To test the accuracy of the method, three certified materials were analyzed: a marine sediment, a river sediment and a domestic sewage sludge. The concentrations obtained, using calibration against aqueous standards prepared in the same medium as the slurries, are in agreement with the certified values, at a confidence level of 95%, according to the Student-t test. The limit of detection (3s) was 43 ng g-1 in the solid sample and the relative standard deviation for the sediment MESS-2 was 2.3% (n = 10).

Determination of cadmium in sediment by isotope dilution inductively coupled plasma mass spectrometry using a co-precipitation separation technique

A co-precipitation separation method is described for the determination of cadmium in sediment by isotope dilution inductively coupled plasma mass spectrometry. A sediment sample is digested with HNO3, HClO4 and HF, and then ammonia solution is added. Zirconium and Sn, which are sources of spectral interference on Cd isotopes in ICP-MS measurements, are co-precipitated with hydrolysis compounds of Al and Fe (major constituents in the digested solution). However, cadmium is masked with ammonia and still remains in the supernatant. The efficiency of the removal of Zr and Sn in the co-precipitation separation are both around 99.5%, and the recovery of Cd is >80%. The measured n(111Cd)/n(112Cd) ratios in the unspiked digested solution of sediment reference materials (PACS-1 and NIES No. 2) after the co-precipitation and separation are in good agreement with those for a standard Cd solution, and the procedural blank of the co-precipitation separation is extremely low (below the detection limit of ICP-MS). The analytical results obtained for Cd in PACS-1 and NIES No. 2 were 2.396 ± 0.033 µg g−1 (value ± expanded uncertainty) and 0.819 ± 0.011 µg g−1, respectively, which are in good agreement with the certified values (PACS-1: 2.38 ± 0.20 µg g−1, and NIES No. 2: 0.82 ± 0.06 µg g−1). This pretreatment method is simple and reliable for the determination of Cd in sediments by ID-ICP-MS.

Whole‐lake burdens and spatial distribution of cadmium in sediments of Wisconsin seepage lakes, USA

AbstractCadmium was quantified in the surface sediments of six seepage lakes ranging from 8 to 70 ha in surface area, 6 to 20 m in maximum depth, 5.2 to 7.0 in mean epilimnetic pH, and 1.7 to 6.8 mg·L−1 in dissolved organic carbon. Within each lake, dry‐weight concentrations of cadmium (range, 0.02–7.17 μg·g−1) were positively correlated with volatile matter content of the sediments, which increased with water depth. Volumetric concentrations (i.e., mass per volume of wet sediment) were correlated with water depth in only one lake, and they more accurately represented the spatial distribution of sedimentary cadmium within the lakes. Analysis of sediment cores from two of the lakes indicated that surface sediments were enriched with cadmium. The source of cadmium and the within‐lake processes controlling deposition to the sediments were presumably similar among the lakes, as demonstrated by the strong correlation between lake area and whole‐lake burdens of cadmium in the surface sediments (range, 625–5785 g/lake). Hence, cadmium in these lakes appears to be derived largely from atmospheric deposition. When normalized for lake area, cadmium burdens in the surface sediments ranged from 62 to 92 g·ha−1 and were strongly correlated with dissolved organic carbon, but not with lake pH, which suggests a link between the transport of cadmium and organic matter to the sediments.

Biomarker studies with juvenile oysters (Crassostrea virginica) deployed in-situ

Hatchery-reared juvenile oysters (Crassostrea virginica) were deployed in situ for approximately 1 month from mid-May to mid-June of 1996 at sites that were classified as reference, agricultural, suburban, or urban/industrial. Cellular responses (lysosomal destabilization, glutathione concentrations, lipid peroxidation, heat shock proteins, metallothioneins, and multi-xenobiotic resistance proteins) were analysed, and their efficacy as biomarkers of stress was evaluated. Increased lysosomal destabilization, glutathione depletion, increased lipid peroxidation, and induction of heat shock proteins and metallothioneins were observed at many of the polluted sites, but increases in multixenobiotic resistance proteins were not. Significant correlations between sediment contaminants and lysosomal destabilization or glutathione concentrations were observed. Similarly, there were significant correlations between sediment cadmium and copper levels and metallothioneins. Although elevated lipid peroxidation products and heat shock proteins were observed at some of the contaminated sites, there were no significant correlations with contaminants. These studies suggest that lysosomal destabilization and glutathione depletion are sensitive, robust indicators of contaminant stress. Although lipid peroxidation and heat shock protein responses were not correlated with contaminants, they are still regarded as valuable indicators of stress. These studies demonstrate the value of using a suite of cellular biomarkers to identify and characterize stress responses related to anthropogenic perturbations.

Statistical process control in sediment pollutant analysis

Statistical process control (SPC) is proposed for application to monitoring environmental variables. SPC was used to identify long- and short-term trends and outliers of sediment cadmium (Cd) concentration at an ocean outfall and reference station on the San Pedro Shelf, California. SPC is based on parametric statistics, is easy to calculate, emphasizes visual display, and benefits from a suite of time-tested zone rules to objectively distinguish out-of-control conditions (OOC). Since temporal and spatial trends of sediment Cd obtained from SPC are consistent with conventional methods employed here, the advantages of SPC offer promise in analyses of environmental variables. Comments on management applications and quality control are included.

Bioavailability of copper and cadmium in sediment of nanjing section of Changjiang river to aquatic organisms

Bioavailabilities of metals in sediment to aquatic organisms depend on the strength of metal bonding to particulates. The accumulation tests of Cu and Cd in carp and in snails have been studied in vitro with the solution containing semisynthetic sediment samples in which the contents of various speciation of metal in sediment have been extended. For carp, the accumulation of Cu and Cd is related to the concentration of dissolved metal which in turn is affected by the distributions of speciations in sediment under given environmental conditions. It is another pattern for snails, various speciations of metal in sediment can contribute indirectly to metal accumulation. The contribution ratio, or relative importance of various speciations of metal in sediment can be expressed by multiple linear regression formulas. The contribution of ion‐exchangable speciation and coprecipition with carbonate speciation is 105 times larger than that of residue speciation in sediment.

Chronic effect of cadmium in sediments on colonization by benthic marine organisms: An evaluation of the role of interstitial cadmium and acid‐volatile sulfide in biological availability

AbstractThe role of interstitial cadmium and acid‐volatile sulfide (AVS) in controlling the bioavailability of sediment‐associated metal was examined using the chronic saltwater benthic colonization test. Sediments were spiked to achieve nominal cadmium/ AVS molar ratios of 0.0 (control), 0.1, 0.8, and 3.0 in this 118‐d test. Oxidation of AVS in the surficial 2.4 cm within 2 to 4 weeks resulted in sulfide profiles similar to those occurring naturally in local sediments. In the nominal 0.1 cadmium/AVS treatment, measured simultaneously extracted metal (SEMcd) was always less than AVS. Interstitial cadmium concentrations (&lt;3‐10 μg/L) were less than those likely to cause biological effects. No significant biological effects were detected. In the nominal 0.8 cadmium/ AVS treatment, measured SEMcd commonly exceeded AVS in the surficial 2.4 cm of sediment. Interstitial cadmium concentrations (24‐157 μg/L) were of likely toxicological significance to highly sensitive species. Shifts in the presence or absence over all taxa, and fewer macrobenthic polychaetes (Mediomastus ambiseta, Streblospio benedicti, and Podarke obscurd) and unidentified meio‐faunal nematodes, were observed. In the nominal 3.0 cadmium/AVS treatment, concentrations of SEMcd were always greater than AVS throughout the sediment column. Interstitial cadmium ranged from 28,000 to 174,000 μg/L. In addition to the effects above, these sediments were colonized by fewer macrobenthic species, polychaete species, and harpacticoids; had lower densities of diatoms; lacked bivalve molluscs; and exhibited other impacts. Over all treatments, the observed biological responses were consistent with SEMcd/AVS ratios in surficial sediments and interstitial water cadmium concentrations.