Effects of cadmium and zinc on microbial activity in soil; influence of clay minerals. Part I: Metals added individually

Investigations were conducted to determine the effects of Cd and Zn on carbon mineralization and the mycoflora, in glucose supplemented soils and to determine the mediating influence of clay minerals on metal toxicity. Soil amended with either 9% kaolinite (K), 9% montmorillonite (M), or not amended (C) was treated with 0, 100, or 1,000 ppm cadmium (Cd) or 0, 1,000, 5,000, or 10,000 ppm zinc (Zn) (as the sulfate salt). 5,000 and 10,000 ppm Zn significantly increased the length of the lag period of CO₂ evolution and reduced the amount of carbon mineralized whereas 1,000 ppm Zn or 100 and 1,000 ppm Cd had no significant effect. When subsequent additions of 2,400 and 4,000 ppm Cd and 1% glucose were made after 16 days of incubation to soils pretreated with 100 and 1,000 ppm Cd, respectively, the rate and extent of glucose degradation was decreased more in the clay-amended soils, particularly with M. The addition of 9,000 ppm Zn to soils pretreated with 1,000 ppm Zn had little effect on glucose degradation, but the addition of 10,000 ppm Zn to soils pretreated with 5,000 ppm Zn substantially reduced the amount of carbon mineralized. K and M protected fungi in soil from the toxic effects of 15,000 ppm Zn and 5,000 ppm Cd. However, fungi isolated from Cd-treated K- and M-soils were more sensitive to the effects of Cd added to the growth medium than were those isolated from the Cd-treated C-soil. Fungi isolated from Zn-treated K-soil were also more sensitive to the effects of Zn added to the growth medium than those from Zn-treated C-soil.     

Responses of the marine bacterium Pseudomonas fluorescens to an excess of heavy metals: physiological and biochemical aspects

A Pseudomonas fluorescens strain was isolated from oxic marine sediments obtained from the strand zone of the St Anne Bay (a moderately metal-contaminated site to the west of Cherbourg harbour). The strain, which exhibited a high tolerance to metal contamination when cultivated (minimal inhibitory concentration=950 microM [62 mg L(-1)] for Zn, 660 microM [42 mg L(-1)] for Cu, and 505 microM [57 mg L(-1)] for Cd), was further characterized by its physiological and biochemical responses to metal additions to the culture medium. Bacterial growth was significantly disturbed by 380 microM Zn (25 mg L(-1)), 315 microM Cu (20 mg L(-1)) and 90 microM Cd (10 mg L(-1)). The Zn-containing alkaline phosphatase was studied as an intoxication biomarker. Its activity was stimulated (+9%) by an excess of Zn, but inhibited by Cd (-55%) and Cu (-10%), these two elements could displace the native Zn or/and disturb the enzyme 3D-structure. Bacterial O(2) consumption was recorded as a global physiological response to metal stress. This parameter dropped with increasing Cd and Cu contamination (-49% and -45%, respectively, at 20 mg L(-1)). By contrast, Zn increased O2 consumption (approximately +40% for the different tested concentrations). The proteomes of bacteria grown in the presence or absence of 20 mg metal L(-1) were characterized by 2D-gel electrophoresis. The number of spots exhibiting a difference in intensity between the contaminated sample and the control was 65, 68, and 103, for Zn, Cu and Cd, respectively. Among them, 45, 61 and 82 spots respectively appeared de novo or increased in intensity, indicative of metal-stimulated synthesis, particularly for Cu and Cd. In summary, whereas Cd and Cu treatments both stressed cells and slowed down primary metabolism to differing extents, Zn has a stimulating action on several physiological and biochemical parameters.     

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.     

Factors influencing inactivation of Klebsiella pneumoniae by chlorine and chloramine

Inactivation of Klebsiella pneumoniae cultures by chlorine and chloramine was evaluated under different growth conditions by varying nutrient media dilution, concentrations of essential inorganic nutrients (FeCl3, MgSO4, phosphate, and ammonium salts), and temperature. All inactivation assays were performed at room temperature (22-23 degrees C) and near neutral pH (7.2-7.5). C*T(99.9) values for chlorine increased >20-fold and for chloramine increased 2.6-fold when cells were grown in 100-fold diluted nutrient broth (2NB) solutions (final TOC of 35-40 mg/L). Background levels of Mg: 6.75 x 10(-2) mM and Fe: 3.58 x 10(-5) mM or high levels of FeCl3 (0.01 mM) and MgSO4 (1 mM) during growth resulted in the highest resistances to chlorine with C*T(99.9) values of 13.06 (+/-0.91) and 13.78 (+/-1.97) mg-min/L, respectively. Addition of low levels of FeCl3 (0.001 mM) and MgSO4 (0.1 mM) to K. pneumoniae cultures during growth resulted in the lowest bacterial resistances to inactivation; C*T(99.9) values ranged from 0.28 (+/-0.06) to 1.88 (+/-0.53)mg-min/L in these cultures. Increase in growth temperature from 22.5 degrees C to 35 degrees C for unamended 2NB cultures resulted in a 42-fold decrease in C*T(99.9) values for chlorine. A similar change in temperature resulted in no significant change in C*T(99.9) values for chloramine. These results indicate that inactivation of K. pneumoniae cultures by chlorine was highly sensitive to changes in growth conditions unlike inactivation by chloramine.     

The effect of graded doses of cadmium on lead,zinc and copper content of target and indicator organs in rats

Eleven groups of inbred Wistar rats, five males and five females in each group, received graded doses of CdCl₂, from 0–25 ppm, in the drinking water from conception until sacrifice at the age of ten weeks. The Pb, Zn and Cu levels of various indicators and target organs were recorded by atomic absorption spectrophotometry. Cd concentrations above 5 ppm caused a significant increase in Zn content of kidneys, liver, spleen, heart and adrenal glands in most of the experimental groups, and in addition a significant positive correlation between Cd and Zn in the same tissues. With concentrations above 10 ppm, Zn contents of epiphyses and diaphyses decreased significantly, and through all groups there was a significant negative correlation between Zn and Cd in diaphysis. This local Zn deficit may cause a retarded growth of long bones. Cd supply resulted in a significant decrease in Zn content of incisors and molars, but did not significantly affect the Cu content. Neither were Zn nor Cu concentrations in hair affected. Cd supply led to a significantly increased storage of Cu in liver, spleen, heart and skeletal muscle and a positive correlation between Cd and Cu content in the same tissues. Cd administration caused a significant decrease of Pb concentrations in molars, hair, kidney cortex, heart, skeletal muscle and adrenal glands in several of the experimental groups, and also a significant negative correlation between Pb and Cd content of molars, hair, kidney cortex, liver and heart. This can be a result of decreased uptake, increased excretion or changes in the distribution pattern of Pb.     

The use of the aquatic moss Fontinalis antipyretica L. ex Hedw. as a bioindicator for heavy metals: 3. Cd2+ accumulation capacities and biochemical stress response of two Fontinalis species

We studied heavy metal stress responses of two Fontinalis species, F. antipyretica and F. dalecarlica, collected from two habitats in Germany and Canada. The capacities of the two species for extracellular adsorption (biosorption) and intracellular uptake (bioaccumulation) of Cadmium (Cd2+) were investigated in the laboratory. Time-dependent Cd2+ adsorption by cell wall and intracellular uptake differed significantly between the two species. These differences were related to the number of Cd2+ binding sites, resulting from differences in leaflet surface and cell wall composition. Glutathione (GSH) levels in response to Cd2+ exposure were monitored over a 10-day period. GSH synthesis differed significantly between the two species. Both Fontinalis species appear to be suitable for heavy metal biomonitoring in aquatic habitats.     

Effects of cadmium and zinc on microbial activity in soil; influence of clay minerals. Part II: Metals added simultaneously

Investigations were conducted to determine the effects of combinations of zinc (Zn) and cadmium (Cd) on heterotrophic microbial activity in soil and on the mediating influence of clay minerals. Soil was treated with 0, 1,000, 5,000, 10,000, or 15,000 ppm Zn alone and in combination with 100 or 1,000 ppm Cd. There was a sequential lag in the initiation of glucose degradation with increasing concentrations of both metals: the greatest lag was with 15,000 ppm Zn plus 1,000 ppm Cd, where CO₂ evolution began approximately 2 days after it began in the untreated soil. The effect on the lag period of the two metals together was additive rather than synergistic. The addition of kaolinite (K) or montmorillonite (M) slightly reduced the extension of the lag induced by the addition of 10,000 ppm Zn + 1,000 ppm Cd. The inhibitory effect of Zn on the total amount of carbon mineralized was not affected by the concomitant addition of 100 ppm Cd, but when added with 1,000 ppm Cd, Zn either had no effect on or increased the total amount of carbon mineralized. 10,000 ppm Zn + 1,000 ppm Cd reduced the number of eubacteria and actinomycetes isolated from the soil to a greater extent than the number of fungi. K and M protected the fungi and M protected the actinomycetes, but neither clay protected the eubacteria from the toxic effects of these two metals. Exposure to Cd alone and in combination with Zn in soil reduced the sensitivity of the isolated fungi to Zn and Cd.     

Geochemical survey and metal bioaccumulation of three bivalve species (Crassostrea gigas, Cerastoderma edule and Ruditapes philippinarum) in the Nord Medoc salt marshes (Gironde estuary, France)

A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation study for three filter-feeding bivalve species (oysters, Crassostrea gigas; cockles, Cerastoderma edule; and clams, Ruditapes philippinarum) was conducted in a breeding basin of the Nord Medoc salt marshes connected to the Gironde estuary, which is affected by historic polymetallic pollution. Regular manual surface measurements of temperature, salinity, pH and dissolved O(2) concentration and hourly multiprobe in situ measurements throughout several periods for 6-8 weeks were performed. The geochemical behavior of metals in water, suspended particulate matter and sediment and their ecotoxicological impact on the three bivalve species were evaluated by in situ exposure of juvenile oysters (water column) and adult cockles and clams (sediment surface). The physico-chemical parameters reflected seasonal variations and basin management. A distinct daily periodicity (except salinity) indicated intense photosynthesis and respiration. In summer, low dissolved O(2) saturations ( approximately 40-50%) occurred in the early morning at 30 cm above the sediment, whereas in depressions, the water column near the sediment surface was suboxic. Cadmium, Zn and Cu concentrations in suspended particulate matter exceeded typical estuarine values and were much higher than the homogeneously distributed concentrations in different depth ranges of the basin sediment. Particles collected in sediment traps showed intermediate metal concentrations close to sediment values. These results suggest trace metal recycling due to reductive dissolution under suboxic conditions at the sediment surface resulting in trace metal release to the water column and adsorption onto suspended particles. Dissolved Cd, Zn and Hg concentrations (e.g. 13-136 ng l(-1); 0.3-25.1 microg l(-1) and 0.5-2.0 ng l(-1), respectively) in the basin corresponded to the concentration range typically observed in the Gironde estuary, except for some maximum values attributed to metal recycling. In contrast, dissolved Cu concentrations (1.08-6.08 microg l(-1)) were mostly higher than typical estuarine values, probably due to recycled Cu complexation by dissolved organic matter. Growth, bioaccumulation rates and kinetics in the whole soft body of the bivalves were analyzed every 40 days. Although Cd bioaccumulation of oysters was lower in the basin than in the estuary during the same period (27,000 ng g(-1), dry weight and 40,000 ng g(-1), respectively) these values are largely above the new human consumption safety level (5000 ng g(-1), dw; European Community, 2002). For cockles and clams, Cd bioaccumulation was lower, reaching 1400 ng g(-1) and 950 ng g(-1), respectively. Similar results were obtained for Zn and Cu suggesting physiological differences between the species and/or differences in the exposure of the organisms due to physico-chemical conditions and metal distribution between dissolved and particulate phases. In contrast, Hg bioaccumulation was highest for cockles reaching bioconcentration factors of approximately 200,000, which even exceeded that of Cd in oysters (50,000) for the same exposition period. Nevertheless, Hg concentrations remained relatively low in the three bivalve species.     

Cadmium solubility in paddy soils: effects of soil oxidation, metal sulfides and competitive ions

Cadmium (Cd) is a non-essential element for human nutrition and is an agricultural soil contaminant. Cadmium solubility in paddy soils affects Cd accumulation in the grain of rice. This is a human health risk, exacerbated by the fact that rice grains are deficient in iron (Fe) and zinc (Zn) for human nutrition. To find ways of limiting this potential risk, we investigated factors influencing Cd solubility relative to Fe and Zn during pre-harvest drainage of paddy soils, in which soil oxidation is accompanied by the grain-filling stage of rice growth. This was simulated in temperature-controlled “reaction cell” experiments by first excluding oxygen to incubate soil suspensions anaerobically, then inducing aerobic conditions. In treatments without sulfur addition, the ratios of Cd:Fe and Cd:Zn in solution increased during the aerobic phase while Cd concentrations were unaffected and the Fe and Zn concentrations decreased. However, in treatments with added sulfur (as sulfate), up to 34 % of sulfur (S) was precipitated as sulfide minerals during the anaerobic phase and the Cd:Fe and Cd:Zn ratios in solution during the aerobic phase were lower than for treatments without S addition. When S was added, Cd solubility decreased whereas Fe and Zn were unaffected. When soil was spiked with Zn the Cd:Zn ratio was lower in solution during the aerobic phase, due to higher Zn concentrations. Decreased Cd:Fe and Cd:Zn ratios during the grain filling stage could potentially limit Cd enrichment in paddy rice grain due to competitive ion effects for root uptake.     

Metal burdens in surface sediments of limed and nonlimed lakes

Acidification has been shown to increase the concentrations of many metals in lake water as a result of increased mobility at lower pH, whereas liming has been found to decrease lake water metal concentrations. We hypothesise that increased sedimentation as a result of liming increases the metal burdens in the sediments of limed lakes, but especially those that have been treated directly on the lake surface. We also hypothesise that acidification results in decreased metal burdens in the sediments, whereas near neutral reference lakes and lakes where the lime has been applied on wetlands or upstream have intermediate metal burdens in the sediments. In order to test the hypothesis, we statistically compare the areal metal and P burdens in the sediments of four groups of lakes: (1) Mainly surface limed lakes, (2) Mainly upstream/wetland limed lakes, (3) Near neutral reference lakes and, (4) Acidified reference lakes. The statistical analysis reveals that the surface limed group have significantly higher areal burdens of As, Cd, Co and Zn in the sediment compared to the acidified reference group, despite large variations within the groups. The investigation indicates that surface liming increases the areal burdens in the sediments of Cd and Pb, probably of As, Ca and Mn and possibly Co and Zn, whereas acidification decreases the areal burdens in sediments of Cd, Fe, Mn and possibly Co, P and Zn. The results of the study confirm the hypothesis.     

Enhanced phytoextraction of uranium and selected heavy metals by Indian mustard and ryegrass using biodegradable soil amendments

The applicability of biodegradable amendments in phytoremediation to increase the uptake of uranium (U), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) by Indian mustard (Brassica juncea) and ryegrass (Lolium perenne) was tested in a greenhouse experiment. Plants were cultivated during one month on two soils with naturally or industrially increased contaminant levels of U. Treatments with citric acid, NH₄-citrate/citric acid, oxalic acid, S,S-ethylenediamine disuccinic acid (EDDS) or nitrilotriacetic acid (NTA) at a rate of 5 mmol kg^− 1 dry soil caused increases in soil solution concentrations that were up to 18 times higher for U and up to 1570 times higher for other heavy metals, compared to the controls. Shoot concentrations increased to a much smaller extent. With EDDS, 19-, 34-, and 37-fold increases were achieved in shoots of Indian mustard for U, Pb and Cu, respectively. The increases in plant uptake of Cd, Cr and Zn were limited to a factor of four at most. Ryegrass generally extracted less U and metals than Indian mustard. Despite a marked increase of U and metal concentrations in shoots after addition of amendments, the estimated time required to obtain an acceptable reduction in soil contaminant concentrations was impractically long. Only for Cu and Zn in one of the studied soils, could the Flemish standards for clean soil theoretically be attained in less than 100 years.     

Heavy metal biosorption by gellan gum gel beads

The Ni(2+) accumulation in batch mode from diluted solutions by gel beads of gellan gum (GG), alginate, kappa-carrageenan, agar, agarose, silica gel, polyacrylamide and two mixtures of GG+agar was investigated. All polymeric materials studied accumulated Ni(2+), but gel beads of GG were stable, easily obtainable and showed the highest Ni(2+) accumulation. The pH of the Ni(2+) solution was not critical for Ni(2+) accumulation. Accumulation of metals Cu(2+), Co(2+), Ni(2+), Pb(2+), Cd(2+) and Zn(2+) by GG gel beads reached the equilibrium after 24h. The removal of Pb(2+) and Cu(2+) from the aqueous solution was very efficient, with maximum metal uptake (q(max)) of 0.85 and 0.75 mmol/g dw GG, respectively. The general q(max) sequence was Pb>Cu>Ni approximately Zn=Co>Cd. In an equimolar metal mixture sorption experiment a clear reduction in accumulation was observed, except for Pb(2+) (30%). Heavy metals were desorbed with 100mM sodium citrate.     

Trace elements in fruiting bodies of ectomycorrhizal fungi growing in Scots pine (Pinus sylvestris L.) stands in Poland

The trace metal contents in fruiting bodies of ectomycorrhizal (ECM) fungi, symbiotic partners of Scots pine, were studied on three sites situated in west-central Poland. Elements were determined by atomic absorption spectrometry in 123 samples of 16 species. The study explored the differences in metal accumulation in relation to site, fungal species, age and part of the fruiting body and results were related to metal content in soil and plant material (roots and needles). Soil analysis revealed that results were obtained under environmental conditions not subject to strong anthropogenic pressure. Median metal concentrations did not differ disparately between sites, although the concentrations of each of the tested metals in the individual species varied to a large extent. Extremely high levels of Al with a large bioconcentration factor (BCF) were found in sporocarps of Thelephora terrestris. The spread between the highest and the lowest concentration (max/min) was very wide in Al, Cd and Pb and these elements may be considered to be absorbed preferentially by fruiting bodies of some species whereas Fe, Mn and Zn, with relatively low values of max/min, are normally absorbed by the majority of fungi. There was no clear relationship between caps and stipes in metal content. However, a tendency to higher metal concentration in the caps was observed. The metal content in young and older fruiting bodies of five different fungi was species dependent. In order to estimate the degree of accumulation of each element by plant and mushrooms, bioconcentration factors (BCFs) were calculated. In plant material (roots and needles), highest values of BCFs were noted for essential metals, like Zn and Mn. Lead showed a definite exclusion pattern (BCF below 1). In fruiting bodies of tested fungi, especially in Amanita muscaria, cadmium was the most intensively accumulated metal. Lead was excluded by plants but was accumulated or excluded by fungi depending on the species. The significance of mycological observation and quantification of the metal content in monitoring of the forest ecosystem is discussed.     

Zinc,copper, cadmium and chromium in polished and unpolished rice

One hundred samples of polished and 27 of unpolished rice were collected from 22 countries and areas and analyzed for Zn and Cu by flame atomic absorption, for Cd by carbon furnace atomic absorption, and for Cr by neutron activation. Unpolished rice contains on average 16.4 μg/g Zn, 4 μg/g Cu, 0.029 μg/g Cd and 0.011 μg/g Cr. Polished rice contains 13.7 μg/g Zn, 3 μg/g Cu, 0.029 μg/g Cd and 0.012 μg/g Cr. Thus, polishing brings about a loss of the essential elements Zn and Cu, but not of Cd, a toxic pollutant. Japanese rice has high Cd content. In countries where rice is a major staple food, high Cd content in rice may cause excessive absorption of this toxic metal.     

The distribution of cadmium,copper, lead,and zinc in eelgrass (Zostera marina L.)

The distribution of Cd, Cu, Pb, and Zn in eelgrass (Zostera marina L.) was studied at three locations with different heavy metal loads in the Limfjord, Denmark.The eelgrass was fractionated into roots, rhizome, stem, and leaves according to age, and the heavy metal concentrations in each fraction were determined. The distribution patterns of the four heavy metals in eelgrass were independent of the heavy metal loads at the sampling stations. The concentrations of all metals were greater in the roots than in the rhizomes. In the aerial¹ parts two different age-dependent distribution patterns were observed. The concentrations of Cd, Pb, and Zn increased with age while the opposite was true for Cu. The distribution of lead correlated with the distribution of ash content. These age-dependent distribution patterns were maintained throughout the observation period and were most pronounced for Cu and Zn in winter.The heavy metal distribution in eelgrass is discussed in relation to gross morphology, especially age-structure. It is suggested that the accumulation of Cd, Pb, and Zn is due to a slow irreversible uptake or to the existence of more binding sites in old leaves. The distribution of Cu can be explained by translocation within the plant, dilution due to growth or leakage from the older leaves.     

Interactions between endogenous and dietary antioxidants against Pb-induced oxidative stress in wild ungulates from a Pb polluted mining area

Certain physiologic disorders, attributed to lead (Pb) exposure are related to the generation of oxidative stress. Organisms rely on a complex antioxidant system, composed of endogenously produced compounds such as glutathione (GSH), superoxide dismutase (SOD) and GSH peroxidase (GPX); and dietary antioxidants such as vitamins A and E. The aim of this work was to study the interactions between both groups of antioxidants and to evaluate their role in fighting Pb-induced oxidative stress in wild ungulates living in a Pb mining area. We studied red deer (n = 54) and wild boar (n = 60) from mining and control sites. Liver Pb, copper (Cu) and selenium (Se) levels were measured in liver and bone. Levels of GSH, oxidized GSH (GSSG), lipid peroxidation (TBARS), α-tocopherol, free retinol and retinyl esters, and the activities of SOD and GPX were measured in liver. Wild boar and red deer from the mining sites had higher bone (geometric means: 7.36 vs. 1.23 μg/g dw for boar; and 0.46 vs. 0.11 μg/g dw for deer) and liver Pb levels (0.81 vs. 0.24 μg/g dw for boar; and 0.35 vs. 0.11 μg/g dw for deer) than the controls. Pb exposure in deer was associated with lower GSH, α-tocopherol and retinyl esters, and higher free retinol and TBARS. A similar effect on vitamin A balance was observed in wild boar, but this was accompanied with an increase in GSH and α-tocopherol. GPX activity and Se levels were higher in wild boar (mean in controls: 670 IU/mg protein and 1.3 μg/g dw, respectively) than in red deer (150 IU/mg protein and 0.3 μg/g). These differences may indicate that red deer is more sensitive to Pb-induced oxidative stress than wild boar. Both endogenous and nutritional antioxidants may be negatively affected by Pb exposure, and their interactions are essential to fight against Pb-mediated oxidative damage.     

Alkaline biosolids and EDTA for phytoremediation of an acidic loamy soil spiked with cadmium

A greenhouse experiment was conducted to investigate the growth of Brassica juncea and Cd phytoextraction in a mimicked Cd contaminated acidic loamy soil amended with alkaline biosolids, prepared from sewage sludge and coal fly ash, in the presence and absence of EDTA at 2 mmol kg(-1). The acidic loamy soil was spiked with 0, 5, 20, 50 and 100 mg Cd kg(-1) in the form of CdCO(3) and then amended with 4% alkaline biosolids (w/w). Alkaline biosolids and 0.12% CaCO(3) amendments resulted in a higher biomass than unamended soil spiked with 20 mg kg(-1) Cd where plants did not survive and of the two amendments, alkaline biosolids amendment had higher plant dry weight yield and phytoextraction of Cd. Adding 2 mmol kg(-1) EDTA to alkaline biosolids amended soil significantly increased the solubility of Cd ions by 9- to 29-fold, but plant Cd accumulation decreased by a factor of 24-48%. The results indicate that alkaline biosolids amendment is an effective approach for assisting growth of B. juncea and phytoextraction of Cd from the contaminated acidic loamy soil, but further application of chelating agents did not enhance the phytoextraction efficiency of Cd.     

Aromatic plant production on metal contaminated soils

Field and container experiments were conducted to assess the feasibility of growing aromatic crops in metal contaminated areas and the effect of metals on herbage and oil productivity. The field experiments were conducted in the vicinities of the Non-Ferrous Metals Combine (Zn-Cu smelter) near Plovdiv, Bulgaria using coriander, sage, dill, basil, hyssop, lemon balm, and chamomile grown at various distances from the smelter. Herbage essential oil yields of basil, chamomile, dill, and sage were reduced when they were grown closer to the smelter. Metal removal from the site with the harvestable plant parts was as high as 180 g ha(-1) for Cd, 660 g ha(-1) for Pb, 180 g ha(-1) for Cu, 350 g ha(-1) for Mn, and 205 g ha(-1) for Zn. Sequential extraction of soil demonstrated that metal fractionation was affected by the distance to the smelter. With decreasing distance to the smelter, the transfer factor (TF) for Cu and Zn decreased but increased for Cd, while the bioavailability factor (BF) for Cd, Pb, Cu, Mn, and Zn decreased. Scanning electron microscopy and X-ray microanalyses of contaminated soil verified that most of the Pb, Cd, Mn, Cu, and Zn were in the form of small (<1 microm) particles, although there were larger particles (1-5 microm) with high concentrations of individual metals. This study demonstrated that high concentrations of heavy metals in soil or growth medium did not result in metal transfer into the essential oil. Of the tested metals, only Cu at high concentrations may reduce oil content. Our results demonstrated that aromatic crops may not have significant phytoremediation potential, but growth of these crops in metal contaminated agricultural soils is a feasible alternative. Aromatic crops can provide economic return and metal-free final product, the essential oil.     

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.     

Benthic fluxes of cadmium, lead, copper and nitrogen species in the northern Adriatic Sea in front of the River Po outflow, Italy

Trace heavy metal (Cd, Pb and Cu) and nitrogen species (N-NO3, N-NO2 and N-NH4) fluxes between sediment and water were examined for approximately 4 days, in a coastal marine station located in the northern Adriatic Sea in front of the River Po outflow. An in situ benthic chamber, equipped with electronic devices for monitoring and adjustment of oxygen and pH and with a temperature detector, was used. The benthic chamber experiment enabled study of the temporal trend of metals and nutrients when oxygen concentration varied in a controlled environment. Although particular care was devoted to chamber deposition and parameter control, sediment resuspension occurred at the beginning of the experiment and O2 fluctuations were observed during the course of the experiment. Pb concentration was affected by both resuspension and oxic conditions in bottom water, which prevented determination of any reasonable Pb flux value. Cd and Cu, not influenced by oxygen fluctuations, reached an equilibrium phase in a short period with initial positive fluxes from sediment of 0.68 (S.D. = 0.07) and 6.9 (S.D. = 5.6) pmol cm(-2) h(-1), respectively. With regard to nitrogen species, the highest positive flux was that of N-NH4 (10.5, S.D. = 2.4, nmol cm(-2) h(-1)) whose concentration increased in the chamber, while nitrate concentration (initial flux of -5.7, S.D. = 1.5, nmol cm(-2) h(-1)) immediately decreased after the beginning of the experiment. Nitrite concentration was almost constant throughout the experiment and its flux was generally low (initial flux 0.1, S.D. = 0.9, nmol cm(-2) h(-1)).