Mobilization kinetics of heavy metals from contaminated river sediment of northern Taiwan by complexing agents

A laboratory experiment was used to investigate the mobilization kinetics of heavy metals from the sediment of a contaminated river located in northern Taiwan with varied concentrations of NTA and EDTA. We found that there were two stages of desorption in the mobilization of heavy metals from the sediment. As the concentrations of NTA and EDTA ranged 0–3.9 x 10^‐4M (0–100mg/l) and 0–2.7 x 10^‐4M (0–100mg/l) respectively, the mobilization percentages of heavy metals were proportional to the logarithm values of the concentrations of NTA and EDTA. The physical meaning of the multiple first‐order reaction was significant for the actual condition, but occasionally, it had more errors for Cu and Zn in the initial phase. The two‐constant model was most appropriate for describing the rates of mobilization of Pb, Cu, Zn, and Cr. The agreement between the diffusion model and the experimental data was satisfactory for Pb, Cu, Zn, and Cr only in the initial 5 h.     

Crassostrea virginica as an indicator of cadmium pollution

As much as 89, 176 and 292 g Cd g^-1 dry weight were accumulated by adult Crassostrea virginica after treatment for 40 wk with 5, 10 and 15 g Cd kg^-1, respectively, in flowing seawater at ambient salinity and temperature without mortalities. Cadmium accumulation increased with increased concentration of cadmium in seawater; greater amounts were accumulated during the summer months. Uptake patterns measured as cadmium content were similar among the total soft parts, gill, mantle and visceral mass. A continuous increase of cadmium concentration in the visceral mass was observed. This differed from the uptake patterns observed as cadmium concentration in gill, mantle and total soft parts. Although cadmium accumulation in the total soft parts and the tissues was curvilinear over the entire study period, significant linear relations between cadmium concentration and time indicated a general increasing trend. At seawater temperatures below 6°C, when oysters were not actively feeding, cadmium concentrations in the total soft parts varied significantly between treatments, but not within treatments. In the tissues, the rate of uptake expressed as cadmium concentrations was visceral mass>gillmantle. Cadmium concentration in the total soft parts varied inversely with dry weight, whereas cadmium concentration in the total soft parts increased, whereas the content decreased. Cadmium concentration decreased in mantle and gill but increased in the visceral mass during spawning, whereas cadmium content decreased in all tissues. Regression analyses indicated that during spawning dry weight decreased at the same rate in gill and mantle, but they lost less weight and lost it more slowly than visceral mass. Also, during spawning, cadmium content decreased in mantle and gill at the same rate but more slowly than in the visceral mass. In mid-August, Cd concentration decreased despite the continuous addition of cadmium to the seawater; however, Cd content increased, suggesting that organism weight was responsible for fluctuations in cadmium concentrations.     

Cadmium and manganese flux in eelgrass Zostera marina II. Metal uptake by leaf and root-rhizome tissues

Cadmium and manganese radionuclide uptake by Zostera marina L. tissues and translocation between rootrhizomes and leaves was examined. Cadmium concentrations in root-rhizomes increased with incubation time but appeared to reach saturation levels at 24 h of exposure. Translocation of cadmium between root-rhizomes and leaves occurred in both directions. A greater flux of cadmium downward suggested that root-rhizomes were a cadmium sink. Cadmium flux in either direction could be enhanced by a salt gradient. Cadmium appears to move through eelgrass by diffusion or mass flow through vascular tissues and apparent free spaces. Manganese is less mobile but is more readily fixed by leaves. Manganese mobility is not enhanced by salt gradients. Incorporation of cadmium and manganese into root-rhizomes from labelled anoxic sediments was several orders of magnitude less than that from labelled anoxic seawater media.This research was supported by grants to B. H. Brinkhuis from the New York Sea Grant Institute and the Nassau-Suffolk Regional Planning Board, and by a Jessie Smith-Noyes Fellowship and Sigma Xi grant to W. F. PenelloMarine Research Center Contribution No. 248     

Calanoid copepod eggs in sea-bottom muds. IV. Effects of some environmental factors on the hatching of resting eggs

During cadmium uptake by the shore crab Carcinus maenas (L.), cadmium appears in both haemolymph and urine within 1 h, and comes into equilibrium with the haemolymp after some 60 h. The equilibrium concentration for haemolymph cadmium is always considerably less than that of the external medium, whether the latter is close to background level or at the artificially high concentration of 2.2 mg l^-1. Despite earlier evidence that cadmium entering the haemolymph is mainly bound to protein, current results show most of this to be freely labile and quickly displaced by cadmium taken up subsequently. There is some evidence to suggest that cadmium is passed on from the haemolymph to the hepatopancreas. A large proportion of whole-body cadmium is adsorbed onto the exoskeleton and gills. The comparatively rapid efflux of ¹⁰⁹Cd from loaded crabs over a period of 1 week is mainly due to desorption of this cadmium from the outer body surface.     

Sorption du cadmium par une population de la diatomée Phaeodactylum tricornutum en culture

The uptake of cadmium by the marine diatom Phaeodactylum tricornutum (Bohlin) maintained in batch culture was measured as a function of successive growth stages of the diatom, and of the chemical form of cadmium in the culture medium (10 g Cd.l^-1). The relative importance of adsorption and absorption of cadmium by the diatom was evaluated. When cadmium was chelated by ethylenediaminetetraacetate (EDTA) the uptake was negligible. In the absence of a chelating agent the uptake varied with the growth phase of the culture, and the major part of the uptake was by adsorption. Two opposite phenomena seen to be responsible for the processes observed: adsorption of cadmium on the cell walls followed by a gradual elution (desorption) by external metabolites.     

Relationship between cadmium concentrations in seawater and those in the mussel Mytilus edulis

Various forms of regression analysis are presented which show that there is a significant equilibrium relationship between total recoverable cadmium in seawater and its concentration in the mussel Mytilus edulis (P<0.001). The calculations show that the concentration of cadmium in seawater should not exceed 0.20 g l^-1 if the mussel is not to reach a cadmium concentration of 2 mg kg^-1 wet weight: a value frequently used as a food standard for human consumption. Further, when a cadmium value of 2 mg kg^-1 wet weight is reached, the concentration factor by mussels for cadmium from seawater is 9 950.     

Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. I. Accumulation from seawater and a food source

The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, 1 and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and 0.0412 mg Cd g^-1 dry weight after 40 days exposure to 0.1 and 1 ppm Cd, respectively, and 0.1115 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of obsorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.     

Long‐term desorption kinetics of Cu2+from biosorbent in water and seawater

A long‐term study of the desorption kinetics of Cu²⁺from biosorbent materials in water and seawater environments was carried out. The biosorbents were un‐treated and pre‐treated biomass of marine alga Durvillaea potatorum.The pre‐treatment of the biomass was carried out with calcium chloride (CaCl₂) solution followed by thermal treatment. The biosorbents were loaded with Cu²⁺in batch adsorption experiments and the desorption kinetics were measured in water and seawater in static batch desorption experiments for a period over 10 months. The physical and structure characteristics of the biosorbents were also examined under a microscope. The un‐treated biosorbent structure completely broke down in 2 and 1 months in water and seawater environments, respectively. The pre‐treatment procedure applied improved the biosorbent stability and its long term desorption rate was extremely low.     

Uptake and loss of radioactive cadmium by the sea-skater Halobates robustus (Heteroptera: Gerridae)

Sea-skaters, Halobates robustus Barber, caught around the Galápagos Islands, were exposed over a period of 3 days to radioactive cadmium dissolved in seawater. Although ^115mCd (metastable ¹¹⁵Cd) was accumulated by the insects, they did not concentrate it above the seawater level. The experiments clearly showed that cadmium is taken up into the body, not merely adsorbed onto surfaces. The uptake of Cd followed a biphasic time course. When sea-skaters labelled in this way were transferred back into unlabelled seawater, the rate of loss of Cd was likewise biphasic. During uptake and loss, the biological half-life times for the first compartments were almost identical (0.64 and 0.79 h), indicating that the same compartment might be involved. On the other hand, the biological half-life times for the second compartments were different (1.7 days during uptake, 19.5 days during loss), indicating that the site or chemical form of bound Cd in the sea-skater had changed. For an adult female, weighing about 8.5 mg wet weight, the drinking rate of seawater was estimated at 2.5 l day^-1, equivalent to 29% body weight.     

Uptake and accumulation of naphthalene by the oyster Ostrea edulis,in a flow-through system

A flow-through system was used to follow naphthalene and naphthalene metabolite accumulation in the seawater and in the tissue of the oyster Ostrea edulis. After 72 h, 82.5% of the naphthalene carbon was recovered from the system. Glucose was added to seawater to stimulate the pathways of glucose metabolism in the oysters. Streptomycin (100 ppm) reduced microbial oxidation of naphthalene and glucose, and reduced bacterial growth. However, even in the presence of streptomycin, microbial oxidation of naphthalene was considerable. The main oxidation product recovered from seawater was ¹⁴CO₂. Radioactivity was also associated with compounds which separated by TLC with 2- and 1- naphthol. The pattern of naphthalene uptake and accumulation in oyster tissues was relatively constant after only a few hours of exposure to naphthalene. The potential of tissues to accumulate naphthalene was shown to be a function of multiple variables such as nutritional state, lipid concentration, length of exposure to naphthalene, and the external naphthalene concentration. Carbon-14-labeled metabolites derived from ¹⁴C-naphthalene were consistently recovered from digests of the oyster tissues. Non-CO₂ alkaline-soluble substances were the primary metabolites. Hexane-extractable substances, which separated by TLC with known standards of 2- and 1- naphthol, were consistently recovered from seawater and tissue digests. It was not possible to conclude that these metabolites were a result of naphthalene metabolism by oyster enzyme systems.     

Coral calcification: Sources of error in radioisotope techniques

Isotopic exchange occurs between coral skeleton and ⁴⁵Ca⁺⁺ and H¹⁴CO ₃ ^- in seawater. Exchange of ¹⁴C onto skeletons is more rapid than exchange of ⁴⁵Ca⁺⁺. Exchange of ¹⁴C from skeletons to seawater takes place more slowly than exchange of ⁴⁵Ca⁺⁺ to seawater. When living coral is incubated in the dark with radioisotopes for 1 h, the tissues contain considerably more radioactivity than is associated with the skeleton. The tissue radioactivity reflects permeation of tissues and coelenteron by radioactive compounds from the incubation seawater. Addition of alkalis to cardioactive seawater results in a radioactive precipitate, part of which becomes associated with any coral skeleton present, and part of which forms on the wall of the containing vessel. Strong alkali removes biologically-deposited radioisotope from coral skeletons. Deposition, of ¹⁴C from H¹⁴CO ₃ ^- in skeletons of living coral incubated in the dark is greater than in dead coral. The reverse situation occurs with ⁴⁵Ca⁺⁺.     

Influence of physiological condition on cadmium transport from haemolymph to hepatopancreas inCarcinus maenas

Accumulation and binding of cadmium in the tissues of the shore crabCarcinus maenas (L.) were investigated in a series of laboratory experiments. The relation between the physiological condition of individual crabs and their ability to transport cadmium from haemolymph to hepatopancreas was specifically addressed. Cadmium was removed from the haemolymph with a half-life of approximately 10 h, and half of the cadmium removed from the haemolymph was taken up in the hepatopancreas. The efficiency with which individual crabs transported cadmium from the haemolymph to the hepatopancreas was strongly related to physiological parameters, such as concentrations of calcium and magnesium in the hepatopancreas and haemolymph volume and haemolymph protein concentration. The transport of cadmium from the haemolymph to the hepatopancreas was saturated in crabs exposed to more than 2 to 4 mg Cd l^–1 in the sea water. In the hepatopancreas of unexposed crabs, cadmium was bound mainly in the insoluble tissue fraction (40%) and in the protein fraction with a molecular weight of approximately 6000 D (50%). Exposure to 0.25 to 1.5 mg Cd l^–1 for 2 w led to dose-dependent increases of the amounts of cadmium bound in the high-molecular weight protein fraction and in the insoluble tissue fraction. Modes of internal cadmium transport and accumulation in tissues and variability in physiological parameters are discussed.     

Luminous bacteria of a monocentrid fish (Monocentris japonicus) and two anomalopid fishes (Photoblepharon palpebratus and Kryptophanaron alfredi): population sizes and growth within the light organs,and rates of release into the seawater

The light organs of monocentrid and anomalopid fishes consist of bacteria-filled tubular invaginations of the epidermis which are connected to the surrounding seawater by ducts. We used the release of bacteria from the light organs to estimate bacterial rates of growth in the light organs. For one monocentrid fish (4 specimens of Monocentris japonicus collected at Jogashima, Japan in 1980) and for two anomalopid fishes (2 specimens each of Photoblepharon palpebratus collected at Sebu, Phillipines in 1981 and Grand Comore Island in 1975 and Kryptophanaron alfredi collected at Parguera, Puerto Rico in 1982) we measured rates of release of bacteria into the surrounding seawater and the bacterial population sizes in the light organs; from this information we calculated doubling times of bacteria in the light organs. In addition, we determined the luminescence of bacteria after their release into the seawater. For M. japonicus, two specimens released 1.1 to 6×10⁶ and 2×10⁷ bacteria h^–1, respectively; the light organs contained about 1.5×10⁸ bacteria. For P. palpebratus, one specimen released 2.2×10⁸ bacteria h^–1; a second specimen had light organs containing 5.2×10⁹ bacteria. For K. alfredi, one specimen released 7×10⁷ bacteria h^–1 and had light organs containing 5.6×10⁸ bacteria; a second specimen released 3.6×10⁷ bacteria h^–1 and had light organs containing 7.3×10⁸ bacteria. Bacterial doubling times in the light organs of these three fishes were variable and ranged from 7.5 to 135 h in M. japonicus and 8 to 23 h in the anomalopids. Bacteria released from M. japonicus into the seawater remained viable, but bacteria from all of the fishes soon ceased to emit light.     

Influence of some parameters on adsorption rate and toxicity of cadmium in activated sludge

The influence of pH, competitor ions (NaNO₃) and aerobic and anaerobic stabilization of activated sludge on the cadmium uptake by activated sludge solids was investigated. Above 0.08 mg L^‐1 cadmium in solution, biosorption was found to follow the Freundlich isotherm. Active cellular uptake of soluble cadmium does not appear to be a significant mechanism of the biosorption. In addition, the cadmium uptake is not completely reversible. The adsorption of cadmium by activated sludge seems to involve a physico‐chemical mechanism with especially weak electrostatic interactions with ion‐exchange reaction. The optimum adsorption pH was 7.5. Adsorption is influenced by sodium ion concentrations up to an equivalent conductivity of 10 000 μS cm^‐1. Aerobic and anaerobic stabilization of activated sludge increase systematically the initial adsorption capacities. Respirometric measurements were done to evaluate the inhibitive effects of cadmium on activated sludge. Monod's equation and the equation of non‐competitive inhibition were used to describe the toxicity related to cadmium uptake. These two equations appear to be complementary.     

Influence of temperature and salinity on the uptake,distribution and depuration of mercury,cadmium and lead by the black-lip oyster Saccostrea echinata

Saccostrea echinata (Quoy and Gaimard) were exposed to 10 g 1^-1 of either mercury, cadmium or lead at 30 °C, 36S; 30 °C, 20S; 20°C, 36S and 20°C, 20S for 30 d and were then transferred to clean seawater for a further 30 d to depurate. Specimens were removed at regular intervals during the exposure and depuration periods, dissected into gills, mantle, visceral mass and adductor, and analysed for the appropriate metal by atomic absorption spectroscopy. Mercury was concentrated more than the other metals in all tissues under all conditions. Cadmium uptake was greater than lead in all tissue in the high-temperature experiments, whereas both metals were concentrated to similar extents at low temperature. The gill tissue generally accumulated the greatest amount of all 3 metals, whilst the adductor concentrated the least amount. At both salinities, mercury and cadmium accumulation by all tissues was significantly greater at the higher temperature whereas lead uptake was only marginally increased. The accumulation rates of mercury at high temperature were significantly greater in all tissues at low compared with high salinity, whereas at low temperature, differences were not significant. Accumulation rates of cadmium and lead in the majority of tissues examined were significantly greater in lowsalinity water at both temperatures. In general, lead was lost the most rapidly from oyster tissues, followed by mercury and then cadmium. The residence times for mercury and cadmium differed significantly between tissues, with the gills showing the highest turnover rate. In contrast, residence times for lead were similar between tissues. Losses of all 3 metals from oyster tissues were not obviously influenced by temperature and only mercury losses differed significantly between salinities.     

Influence of food quantity on the kinetics of cadmium uptake and loss via food and seawater in Mytilus edulis

The difference between the cadmium uptake via food and seawater in Mytilus edulis has been studied. This was done by labelling algae with Cd-109 and seawater with Cd-115m. Mussels were fed on six different quantities of Isochrysis galbana. Cadmium uptake via algae was more efficient at low food levels, while accumulation from seawater was linearly correlated with food quantities. Cadmium from food contributed only little to the body burden (0.2–0.5%). Half-lives for the elimination of cadmium ranged from 96–190 d and increased with decreasing availability of algae, presumably due to slowed down metabolism. Differences in elimination patterns suggest a release of both isotopes from different storage depots. A computer model shows that the food pathway can only play a significant role if algae are highly contaminated. It also demonstrates the paradox that in long-term studies the highest contribution of food-derived cadmium to the body burden must be expected near maintenance food concentrations.     

Crassostrea virginica as an indicator of lead pollution

After treatment with 1.0 and 3.3 g Pb kg^-1 for 20 weeks in flowing seawater at ambient salinity and temperature, Crassostrea virginica accumulated as much as 6.57 and 11.42 g g^-1 dry weight, respectively, and no mortalities were recorded. Lead uptake was curvilinear; however, the general trend was an increase in lead concentration over time. Dry weight of the oyster had no significant relation with tissue lead concentration (g g^-1); however, a significant positive relationship existed between weight and lead content (g). A decrease in lead concentration in the tissues occurred from mid-August to mid-September despite continuous addition of lead to the seawater. Addition of lead to the seawater was terminated after 20 weeks (October), and lead loss was studied for the following 12 weeks. Lead loss was studied well after spawning in an attempt to eliminate any influence this might have on lead concentration in the tissues. After 4 weeks, approximately 54% of the accumulated lead was lost under conditions of a natural temperature decline. The biological half-life of lead in C. virginica tissues was calculated to be 5.5 weeks. In the ensuing 8 weeks, little or no lead loss was observed. Larvae from each treatment developed to the straight-hinged stage within 48 h with no apparent abnormalities. Lead appeared to have no adverse effect on larvae when parents had been treated with 1.0 and 3.3 g kg^-1 seawater for 10 weeks.     

Modelling the kinetics and equilibrium properties of cadmium biosorption by river green alga and water hyacinth weed

Cadmium biosorption properties of non-living, dried river green alga from a river source, and water hyacinth weed, Eichhornia crassipes from a lake in Zimbabwe have been investigated. The cadmium uptake was found to depend on initial pH, uptake being apparently minimal at low pH values and increasing with an increase in pH. Cadmium biosorption kinetics by both samples is fast, with 80% of total uptake occurring within 60?min. The effect of initial solution pH and initial cadmium concentration on cadmium biosorption from a cadmium solution has been studied. The data for algal biomass fitted the Langmuir monolayer adsorption isotherm, while the biosorption of the metal by water hyacinth weed fitted the Freundlich adsorption isotherm with 1/n values all less than 1. Maximum metal uptake capacities were recorded using 0.35?g of biomass and a 250?mg?L^?1 cadmium solution at pH 6.5 and at 25°C and these were about 85 and 50?mg?L^?1 for water hyacinth weed and green alga, respectively, showing that water hyacinth weed offered a greater potential for cadmium uptake. The absorption was described by pseudo-second order rate model and the rate constant and equilibrium sorption capacity are reported.     

Symbiotic anemones can grow when starved: nitrogen budget for Anemonia viridis in ammonium-supplemented seawater

The ability of endosymbioses between anthozoans and dinoflagellate algae (zooxanthellae) to retain excretory nitrogen and take up ammonium from seawater has been well documented. However, the quantitative importance of these processes to the nitrogen budget of such symbioses is poorly understood. When starved symbiotic Anemonia viridis were incubated in a flow-through system in seawater supplemented with 20 μM ammonium for 91 d under a light regime of 12 h light at 150 μmol photons m⁻² s⁻¹ and 12 h darkness, they showed a mean net growth of 0.197% of their initial weight per day. Control anemones in unsupplemented seawater with an ammonium concentration of <1 μM lost weight by a mean of 0.263% of their initial weight per day. Attempts to construct a nitrogen budget showed that, over a 14 d period, ≃40% of the ammonium taken up could be accounted for by growth of zooxanthellae. It was assumed that the remainder was translocated from zooxanthellae to host. However, since the budget does not balance, only 60% of the growth of host tissue was accounted for by this translocation. The value for host excretory nitrogen which was recycled to the symbionts equalled that taken in by ammonium uptake from the supplemented seawater, indicating the importance of nitrogen retention to the symbiotic association. Received: 23 December 1997 / Accepted: 12 September 1998