Metal uptake by young trees from dredged brackish sediment: limitations and possibilities for phytoextraction and phytostabilisation

Five tree species (Acer pseudoplatanus L., Alnus glutinosa L. Gaertn., Fraxinus excelsior L., Populus alba L. and Robinia pseudoacacia L.) were planted on a mound constructed of dredged sediment. The sediment originated from a brackish river mouth and was slightly polluted with heavy metals. This preliminary study evaluated the use of trees for site reclamation by means of phytoextraction of metals or phytostabilisation. Although the brackish nature of the sediment caused slight salt damage, overall survival of the planted trees was satisfactory. Robinia and white poplar had the highest growth rates. Ash, maple and alder had the highest survival rates (>90%) but showed stunted growth. Ash, alder, maple and Robinia contained normal concentrations of Cd, Cu, Pb and Zn in their foliage. As a consequence these species reduce the risk of metal dispersal and are therefore suitable species for phytostabilisation under the given conditions. White poplar accumulated high concentrations of Cd (8.0 mg kg(-1)) and Zn (465 mg kg(-1)) in its leaves and might therefore cause a risk of Cd and Zn input into the ecosystem because of autumn litter fall. This species is thus unsuitable for phytostabilisation. Despite elevated metal concentrations in the leaves, phytoextraction of heavy metals from the soil by harvesting stem and/or leaf biomass of white poplar would not be a realistic option because it will require an excessive amount of time to be effective.     

Effects of willow stands on heavy metal concentrations and top soil properties of infrastructure spoil landfills and dredged sediment-derived sites

The effects of willow stand development on top soil properties of uncontaminated infrastructure spoil landfills (ISL) and contaminated dredged sediment landfills (DSL) were assessed. For the ISL, significant increases in Cd, Zn and organic C levels in the top soil (0-10 cm) were detected more than 20 years after disposal. The increases in Cd and Zn concentrations in the top soil were attributed to leaf-associated metal transfer and leaf fall: the relatively high Cd and Zn concentrations in willow leaves resulted in top soil enrichment for these elements. Higher absolute amounts of Cd, Zn and Mn were taken up and recycled during leaf fall on DSL than on ISL, but did not result in significant differences between top soil and deeper soil (10-30 cm) for the DSL. Direct comparison of top soil development between both types of sites is not possible due to differences in stand age and time since disposal. The DSL were characterised by a higher short-range variance for the Cd, Cr, Cu, Pb and Zn concentrations in the top soil than the ISL. During the first years of ripening and dewatering, significant sulphate leaching occurred in the top soil of the DSL.     

Cadmium adsorption by sediment in a turbulence tank.

The mechanism sediment motion that affects cadmium (Cd) adsorption on sediment particles was studied in a turbulence tank in the presence (and absence) of bed mud. The experimental results were verified by a mathematical model for heavy metal transport-transformation developed for the turbulence tank. The mathematical model includes the equations of water flow, sediment motion, heavy metal transport-transformation, heavy-metal reaction kinematics and equations for prescribing the initial conditions and boundary conditions for the experiment. The model conforms the transport-transformation of heavy-metal pollutants in surface waters to following the law of convective-diffusive of common tracers and the characteristics of fate and transport of sediment motion. Variations of dissolved Cd concentrations and suspended particulate Cd concentrations with time and in the water column were measured and computed. The experimental measurements correspond with the computed results. Both the experimental measurements and computed results show that it takes about 6 h to reach equilibrium condition for cadmium adsorption by sediment particles. This is different from the result obtained from experiments conducted in continuously stirred tank reactors (or batch reactors) in which adsorption equilibrium can be achieved in about 20 min. Determination of the model parameters for sediment adsorption-desorption of metals in the tank is discussed. The experimental and computed results obtained in this study are useful to solve practical engineering problems in surface waters.     

Cadmium and zinc response of the fungi Heliscus lugdunensis and Verticillium cf. alboatrum isolated from highly polluted water

The aquatic hyphomycete Heliscus lugdunensis and the terrestrial fungus Verticillium cf. alboatrum, both isolated from a highly polluted surface water, were investigated for their tolerance against Cd and Zn. Hl-H4 showed a 50% growth inhibition at 0.1 mM Cd, whereas at 0.7 mM Cd the growth of Va-H4 was only reduced by 30%. The fungi also showed a remarkable difference in their Zn-tolerance. The growth of Va-H4 was not inhibited at 1 mM Zn, whereas for Hl-H4 no growth occurred above 0.3 mM Zn. The biosorption and accumulation capacities for Cd or Zn of both fungi differed between the fungal species. In a 0.1 mM Cd-medium Hl-H4 biosorbed 15-fold and accumulated 39-fold more Cd than Va-H4. Exposure to 0.3 mM Zn resulted in a 13-fold higher biosorption and 11-fold higher accumulation for Hl-H4 than Va-H4. As glutathione (GSH) is known to be involved in the phytochelatin synthesis and other stress related processes we investigated its synthesis. Both fungi increased their synthesis of GSH in response to Cd. For Hl-H4 a concentration of 0.0125 mM Cd, corresponding to an intracellular Cd content of 2.1 nmol Cd mg(-1) dw, increased the GSH content, whereas Va-H4 only responded with a higher production of GSH at 1 mM Cd and a concomitant intracellular Cd content of 22.5 nmol Cd mg(-1) dw. An increased GSH synthesis under Zn-stress was only detectable for Va-H4 (20 mM).     

Polybrominated diphenyl ethers in fish and sediment from river polluted by electronic waste

The present study investigated contamination of polybrominated diphenyl ethers (PBDEs) in sediment and fish samples collected from rivers in Guiyu, China where electronic waste (e-waste) is recycled and disposed. PBDE congeners with mono-to hepta-brominated and deca-brominated substitutions were detected using (13)C(12) isotope dilution GC/MS/MS and GC/MS methods, respectively. The total PBDE concentrations ranged from 4434 to 16088 ng/g (dry weight) in Nanyang River bank sediment, from 55 to 445 ng/g in Nanyang River bottom sediment and 51.3 to 365 ng/g in Lianjiang River bottom sediment in Guiyu compared with those from 16.1 to 21.4 ng/g in wastewater discharged from a vehicle repairing workshop in Lo Uk Tsuen in Hong Kong. No PBDE congeners were detected in bottom sediment and fish from Mai Po Marshes in Hong Kong. The mean concentrations of total PBDEs in mixed muscles of tilapia (Oreochromis spp) from Lianjiang River were 115 ng/g wet weight (ww) and from wastewater in Hong Kong were 4.1 ng/g ww. Highest mean PBDE concentration was obtained in liver (2687 ng/g ww), followed by abdomen muscle (1088 ng/g ww) of bighead carp (Aristichthys nobilis) collected from Nanyang River. A significant correlation of concentration of each PBDE congener between sediment and muscle from Guiyu was observed. The present results of total PBDEs in sediment and fish were 10 and 1000 times higher than other studies. Open burning and dumping of e-waste are the major causes of PBDE contamination.     

利用水泥窑协同处置河道底泥工艺的研究与应用

针对含有超标污染物的河道底泥,利用回转窑协同处置技术生产水泥熟料是一种比较好的资源化途径.本文在对河道底泥的成分分析基础上,结合回转窑协同处置技术,对其进行了工艺改进研究.通过实际应用,在保证产品质量的前提下完成了6万m3河道底泥的减量化、资源化、无害化处置.     

Uptake of Cd, Zn and Mn by willow increases during terrestrialisation of initially ponded polluted sediments

Metal concentration of plants growing on contaminated soils among other factors may depend on changes in the hydrological regime of the soil. Foliar and stem metal concentrations in Salix cinerea (grey sallow) were measured in 2 consecutive growing seasons on a submerged sediment-derived soil that underwent gradual terrestrialisation. Foliar and stem cutting concentrations for Cd, Zn and Mn increased on plots that were submerged during the first year, but emerged in the second year of monitoring. The litter layer was sampled under the shrubs of a plot with a recent abrupt change in hydrological regime and on the reference plot. It was separated in three size fractions through sieving. Analysis of the litter fractions suggested that Cd and Zn concentrations remained constant during fragmentation. However, Cr, Cu, Ni and Pb concentrations increased, which was attributed to adhesion of mineral soil particles on the fine fraction. After correction for the metal content in the mineral fraction, an increase in Cd, Mn and Cu concentration during fragmentation of the organic part of the litter layer was observed for the polluted plot. Net litter layer decomposition rate was low, which may indicate low colonisation by the decomposing community. Terrestrialisation resulted in higher Cd, Mn and Zn uptake by willows. The deviant litter layer metal concentrations for Cd, Zn and Mn and low decomposition rate must be further monitored. Feasibility of measures aiming at re-establishing wetland conditions for the dredged sediment landfill must be considered.     

Mobile arsenic species in unpolluted and polluted soils

The fate and behaviour of total arsenic (As) and of As species in soils is of concern for the quality of drinking water. To estimate the relevance of organic As species and the mobility of different As species, we evaluated the vertical distribution of organic and inorganic As species in two uncontaminated and two contaminated upland soils. Dimethylarsinic acid (up to 6 ng As g(-1)), trimethylarsine oxide (up to 1.5 ng As g(-1)), 4 unidentified organic As species (up to 3 ng As g(-1)) and arsenobetaine (up to 15 ng As g(-1)), were detected in the forest soils. Arsenobetaine was the dominant organic As species in both unpolluted and polluted forest soils. No organic As species were detected in the contaminated grassland soil. The organic As species may account for up to 30% of the mobile fraction in the unpolluted forest floor, but never exceed 9% in the unpolluted mineral soil. Highest concentrations of organic As species were found in the forest floors. The concentrations of extractable arsenite were highest in the surface horizons of all soils and may represent up to 36% of total extractable As. The concentrations of extractable arsenate were also highest in the Oa layers in the forest soils and decreased steeply in the mineral soil. In conclusion, the investigated forest soils contain a number of organic As species. The organic As species in forest soils seem to result from throughfall and litterfall and are retained mostly in the forest floor. The relative high concentrations of extractable arsenite, one of the most toxic As species, and arsenate in the forest floor point to the risk of their transfer to surface water by superficial flow under heavy rain events.     

Improved facility management at landfills and waste disposal sites by cover system design analysis

The cover system is a key factor in the management of waste disposal sites. Traditional methods of cover design based on empirical and semi-quantitative analysis have been improved upon by the effective use of models to assess the evapotranspiration, runoff, and infiltration volumes associated with different cover configurations. The Hydrologic Evaluation of Landfill Performance (HELP) model developed for the United States Environmental Protection Agency allows cover performance prediction with a sound technical basis. The HELP model was used to assess four alternative cover designs ranging from simple, two-layer systems to more complex systems incorporating multiple drainage layers and synthetic membrane barriers. A sensitivity study was performed to determine the relative imcorporating cover design parameters such as clay barrier thickness and hydraulic conductivity, synthetic membrane leakage factor, and the length and slope of drainage layers. The results of the study can be used to identify cover designs that reduce infiltration, increase evapotranspiration, and provide manageable volumes of surface runoff within the site vicinity. The modelling indicated that more complex cover systems are not necessarily superior to simpler ones. Efficient cover systems can be achieved by concentrating the engineering design effort on several critical parameters such as the hydraulic conductivity of clay barriers and the leakage factor of synthetic membranes. Other factors, commonly considered important, such as clay barrier thickness and drainage layer design, appear to be less significant.     

Heavy metal contents in surface soils along the Upper Scheldt river (Belgium) affected by historical upland disposal of dredged materials

Concern about heavy metal accumulation in agricultural soils under long-term application of phosphate fertilizers and organic wastes makes investigation of heavy metals in agricultural soils imperative. This study examines the total, available and chemical forms of lead (Pb) in a savanna soil after 50 years of continuous cultivation and application of NPK fertilizers and farmyard manure (FYM). Total Pb concentration ranged from 28 to 42 mg kg(-1) over 2-3 times more than the average Pb concentration of non-polluted soils worldwide. Available Pb was, however, less than 2 mg kg(-1) indicating that Pb in the soils was largely insoluble. There were no detectable concentrations of water soluble and organically-bound Pb fractions. On average, residual Pb accounted for over 80% of total Pb. Compared to the natural site, cultivation and fertilization with NPK and FYM increased total Pb concentration by 19 and 17%, respectively, or, on mass basis, by 10 and 35 kg ha(-1), respectively, after 50 years. Soil Pb showed strong linear relations with sand fraction and inorganic phosphorus in the soils. Thermodynamic equilibrium relations provided some indirect evidence that the control on soluble Pb appeared to be chloropyromorphite [Pb5(PO4)3Cl], an insoluble lead phosphate mineral.     

Simultaneous toxic action of zinc and alachlor resulted in enhancement of zinc uptake by the filamentous fungus Paecilomyces marquandii

Microbial ability vary when pollutants exist together in the environment in comparison to the presence of single toxic compound. The influence of alachlor and zinc on the growth of the filamentous fungus Paecilomyces marquandii and its ability to eliminate alachlor and zinc has been studied. Their simultaneous presence in the polluted environment is very probable. In liquid cultures the pesticide (50 mg/l) was removed with the efficiency of 85% within 7 days. Beginning from the third day of culturing two derivatives of alachlor were found: N-(2',6'-diethylphenyl)-N-metoxymethyl-acetamide and unstable 2-chloro-N-(2',6'-diethylphenyl)-N-hydroxymethyl-acetamide, the first time detected as product of alachlor metabolisation by filamentous fungus. The herbicide elimination was not inhibited by zinc up to 1.0 mM of the metal content in the culture medium, 5.0-7.5 mM of the metal limited alachlor depletion by 30-50%, whereas a higher zinc concentration stopped this process. Zinc content in P. marquandii mycelium during the incubation in growth medium reached 10-20 mg/g of dry weight and was increased up to 99 mg/g by alachlor, however due to its presence a strong inhibitory effect on growth was observed. It was postulated that the increase in zinc binding by the growing mycelium of P. marquandii in the presence of the pesticide was connected with the changes in the wall and membrane composition induced by simultaneous toxic interaction of zinc and alachlor. Only 15-20% of bound zinc was detected in the cell wall of the fungus, whereas the amount of zinc loaded in the wall of mycelium originating from the cultures incubated in the alachlor presence increased to 60%. Additionally, changes in the profile of fatty acids of cultures with pesticide and metal addition were observed.P. marquandii strain seems to be promising for a potential industrial application. It can both effectively bind zinc and remove alachlor from the mixture of pollutants.     

Cadmium and zinc in soil solution extracts following the application of phosphate fertilizers

This study investigated the solubility of cadmium and zinc in soils after the application of phosphate fertilizers containing those two metals. The solubility of cadmium and zinc was assessed by measuring their concentration in soil water extracts. Three monoammonium phosphate fertilizers containing various amounts of metals were applied on cultivated fields for 3 years at three different rates. In order to investigate the effects of long-term applications of fertilizers on the solubility of Cd and Zn, a similar design was used to apply contaminated fertilizers to soils in a laboratory experiment using a single fertilizer addition equivalent to 15 years of application. Phosphate fertilizers increased the concentration of Cd in soil extracts compared to control in 87% and 80% of the treatments in field and laboratory experiments respectively. Both increasing the rate of application and using fertilizer containing more Cd lead to higher Cd concentrations in extracts for the field and the laboratory experiments. The addition of the equivalent of 15 years of fertilizer application in the laboratory results in higher Cd concentration in extracts compared to the field experiment. For Zn, the fertilizer treatments enhanced the metal solution concentration in 83% of field treatments, but no significant correlations could be found between Zn inputs and its concentration in solution. In the laboratory, fertilizer additions increase the Zn concentrations in 53% of the treatments and decrease it in most of the other treatments. The decrease in Zn concentrations in the laboratory trial is attributed to the higher phosphate concentrations in the soil solution; which is presumed to have contributed to the precipitation of Zn-phosphates. For both trials, the metal concentrations in soil extracts cannot be related to the Zn concentration in the fertilizer or the rate of application. The high Zn to Cd ratio is presumably responsible for the Cd increase in the soil extracts due to competitive displacement by Zn. Finally, the observed acidification of soils with fertilizer application will also contribute to metal solubilisation.     

Cadmium and zinc concentrations in drinking water supplies of Dhaka City, Bangladesh

The cadmium concentration in different drinking water supplies of Dhaka City is reported. In this study, cadmium was extracted from water into chloroform after chelation with sodium diethyldithiocarbamate and then back extracted into water for determination by atomic absorption spectrophotometry (AAS). The concentration of cadmium in source water is below the detection limit (51 micrograms l-1) and that in supply water (tap water) and tube-well water ranges from 1.03 to 1.58 and 1.71 to 2.24 ppb, respectively. The corresponding zinc content ranges from 0.013 to 0.30, 0.018 to 3.8 and 0.042 to 0.37 ppm. The implications of these findings are discussed.     

Cadmium and zinc interactions and their transfer in soil-crop system under actual field conditions

The transfer of Cd and Zn from calcareous soils nearby a non-ferrous mining and smelting bases to the spring wheat (Triticum aestivum L.) and corn (Zea mays L.) tissues and the interactions between the two metals concerned were investigated under actual field conditions. Samples of soils and entire crops were randomly collected during harvest time in 1998 in the Baiyin region. The soil metal contents showed that the furrows had been polluted (mean values: 3.16 mg kg(-1) for Cd; 146.78 mg kg(-1) for Zn) and the significant spatial variation of the soil contamination existed here (ranges, Cd: 0.14-19.3 mg kg(-1); Zn: 43.5-565.0 mg kg(-1)). The translocation ratios of the two metals from soil to crop parts in the region studied were relatively lower and the order of the element transfer in different plant tissues was root > stem > grain. The transfer ratio of element Cd was lower than that of element Zn. Cd and Zn uptake by the crop structures could be best described by four models (P < 0.01): linear; exponential; quadratic; and cubic. Apart from a linear relationship between the element Cd in the corn grains and soils, models were generally non-lincar. An analysis of Cd-Zn interaction mechanism led to the conclusion that the effects of the two metals were synergistic to each other under field conditions, in which increasing Cd and Zn contents in soils could increase the accumulations of Zn or Cd in the two crops.     

Semi-empirical approach to modeling of soil flushing: model development, application to soil polluted by zinc and copper

This paper describes a semi-empirical approach to modeling the soil flushing technology. A new mathematical model aimed at predicting the course of the continuous soil flushing process by use of the input data obtained from simple batch laboratory experiments is described in the theoretical part. An objective of the study is to apply this new model to soil polluted by zinc and copper (11949 mg kg(-1) and 1895 mg kg(-1), respectively) by flushing the soil with an ammonia nitrogen solution. A set of batch experiments provided both equilibrium and kinetic data characterizing the leaching ability of both metals. By use of the model, the optimal ammonia concentration in the flushing solution was estimated (0.6 mol L(-1)). For this concentration, validity of the model results was verified by a column experiment. The removal efficiency obtained was 44% (zinc) and 54% (copper). The model correctly predicted the period of time needed for the removal of weakly bound metal fractions as well as the estimate of the overall removal efficiency of metals from the soil during the flushing process. It has also proven that it is possible to use the column experiment for model calibration through the modification of the input data. Agreement of the model and experimental results can be further improved this way.     

DNA can sediment TiO2 particles and decrease the uptake potential by mammalian cells

Titanium dioxide (TiO₂) is an important material used in a broad range of industries. As TiO₂ particles used in industries have recently become smaller as technology develops, problems specific to small size are increasing. One such problem is the difficulty of recovering TiO₂ particles suspended in solution. Particles not recovered during their manufacture would be released in the environment and might be taken up by living organisms, leading to “small-size specific toxicity”, which has recently become a concern in numerous industries. To prevent environmental release of small-size TiO₂, separation and complete recovery of the particles are important. In this study, we showed that DNA could be used to separate TiO₂ particles (60-500 nm) from an aqueous solution. Although TiO₂ particles (20 mg/10 ml) were kept in suspension in a standing solution for 72 h, addition of small amounts of DNA (25-100 μg/10 ml) completely sedimented all particles within 4 h. Analysis with transmission electron microscopy suggested that the enhanced sedimentation with DNA was due to the formation of aggregates of TiO₂ particles with DNA. Conveniently, DNA-treated TiO₂ particles had difficulty translocating into human cell lines (keratinocytes and skin fibroblasts), suggesting that “small-size specific toxicity” can be prevented. DNA is a useful tool for separating TiO₂ particles which would prevent “small-size specific toxicity” by allowing quick and complete recovery and suppression of uptake by living organisms.     

Effect of dissolved organic carbon on the mobility of cadmium, nickel and zinc in leachate polluted groundwater

The ability of dissolved organic carbon (DOC) from landfill leachate polluted groundwater to form complexes with the heavy metals cadmium (Cd), nickel (Ni) and zinc (Zn) was investigated. The DOC samples originated from the leachate pollution plume at Vejen Landfill, Denmark and were studied in the original matrix with a minimum of manipulation. The experiments were performed as batch sorption experiments and the metal distribution between the aquifer material and the solution (K_d) was determined in the leachate polluted groundwater samples and in reference solutions of synthetic inorganic leachate. The difference in distribution coefficients was a direct indication of complex formation between DOC and heavy metals. The results showed, that DOC from landfill leachate polluted groundwater has the ability to form complexes with Cd, Ni and Zn, and the distribution coefficients were a factor of 2–6 lower in the presence of DOC. Based on the distribution coefficients, the relative migration velocities of the heavy metals were estimated. The migration velocity of the metals was increased by the presence of DOC but did not exceed 1.2% of the water migration velocity, indicating that the effect of DOC on the mobility of Cd, Ni and Zn may have only minor environmental importance. Conditional complex formation constants (log K_c) were estimated from the K_d-values. The constants for 1:1 complexes increased slightly in the following order Zn < Cd < Ni. However, increasing the metal concentration into the mg l⁻¹ level decreased the constants by about one order of magnitude, showing the importance of determining the constants at environmentally relevant metal concentrations.     

Influence of chemical conditioning on the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite

Aim of this study was to evaluate the feasibility of the use of clinoptilolite as a barrier material to eliminate heavy metals from roof runoff. The effect of chemical conditioning with 1 M NaCl solution upon the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite has been investigated. According to the batch experiments the modified clinoptilolite has up to 100% higher sorption capacity, regarding Zn than the natural material. The pre-treatment of clinoptilolite results in an acceleration of the ion exchange process up to 40% regarding zinc. In order to define the reasons of this behaviour, both materials, modified and natural, were analysed for: (i) chemical composition, (ii) density, (iii) pore size distribution and (iv) zeta potential. The clogging of the pores, the charge of the grain surface, the pH of the initial metal solution and the ion metal concentration are the factors which are mainly affecting the ion exchange capacity and the rate of zinc uptake by clinoptilolite.     

Influence of organic matter on the uptake of cadmium, zinc, copper and iron by sorghum plants

This article describes an experiment, carried out under controlled environment conditions, to investigate the effects of a fulvic acid fraction of soil organic matter on growth, cadmium (Cd) uptake and redistribution by sorghum. In addition the uptake of copper (Cu), zinc (Zn) and iron (Fe) was also determined. Sorghum was grown in nutrient solutions with 0, 0.1, 1 and 10 mg Cd dm(-3), in the absence and presence of organic matter (32 mg C dm(-3)), for various periods up to 20 days. A decrease in sorghum biomass due to Cd toxicity was observed at 10 mg Cd dm(-3), but for concentrations of 0.1 and 1 mg Cd dm(-3) the biomass was increased compared with control, without visual toxicity symptoms. The presence of organic matter (OM) further increased biomass production. Cadmium was mainly retained in sorghum roots, as usually found in tolerant plants, but Cd accumulation in sorghum was greater than in other Gramineae, or even more tolerant plants such as lettuce. The presence of OM decreased the bioavailability of Cd that was partially retained in solution by the OM ligands. However, OM promoted the translocation of Cd to shoots, an effect that may pose a risk to public health because plant-animal transfer of Cd could be enhanced. The presence of OM decreased the uptake of Cu, Zn and Fe. The presence (vs. absence) of 0.1 mg Cd dm(-3) enhanced the uptake of Fe, both in the absence and presence of OM.     

Cadmium and lead in selected tissues of two commercially important fish species from the Adriatic Sea

Baseline levels of cadmium and lead were determined in muscle tissue and liver of hake (Merluccius merluccius) and red mullet (Mullus barbatus), two commercially important fish species from the eastern Adriatic. Concentrations of trace metals in liver (Cd: 6–183 μg kg⁻¹ w. wt. ; Pb: 39–970 μg kg⁻¹ w. wt.) were within the range of recently published data for the Mediterranean. In the muscle tissue, cadmium concentrations (4.1–29 μg kg⁻¹ w. wt.) were among the lowest reported values for the Mediterranean, whereas lead levels (49–158 μg kg⁻¹ w. wt.) were within the range of values reported for various coastal areas of the Mediterranean. Presented data on cadmium and lead content in the studied fish species provide no proof of the general pollution of the Adriatic. Obtained data were tested in relation to fish length. Metal concentrations in liver decreased with the increase in fish size, whereas no significant correlation was found between trace metal levels in the muscle tissue and the length of both species. Relationships between metal concentrations and sex were also tested, but they gave no significant results. A comparison of contaminant concentrations in the edible tissue of hake and red mullet with the Croatian legislation shows that the consumption of their meat is not harmful for humans, not even for the most endangered population from the coastal region.