Heavy metal bioaccumulation by the organs of Phragmites australis (common reed) and their potential use as contamination indicators

The concentrations of heavy metals in the roots, rhizomes, stems and leaves of the aquatic macrophyte Phragmites australis (common reed), and in the corresponding water and sediment samples from the mouth area of the Imera Meridionale River (Sicily, Italy), were investigated to ascertain whether plant organs are characterized by differential accumulation, and to test the suitability of the various organs for heavy metal biomonitoring of water and soil. Heavy metals considered were Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn. Results showed that belowground organs were the primary areas of metal accumulation. In particular, metal concentrations in plant organs decreased in the order of root > rhizome ≥ leaf > stem. All four organs showed significant differences in concentration for Cr, Hg, Mn, Zn, thus suggesting low mobility from roots to rhizomes and to aboveground organs. Although the organs followed different decreasing trends of metal concentration, the trend Mn > Zn > Pb > Cu was found in each plant organ. Mn showed the highest concentrations in all organs whereas the lowest concentrations regarded Cd and Cr in the belowground and aboveground organs, respectively. The toxic threshold was exceeded by Cr in roots, rhizomes and leaves, Mn in roots and leaves, Ni in roots. The highest average concentrations were found as follows: Cd, Hg, Pb, Zn in root, Cr, Mn, Ni in sediment, Cu in water. Positive linear relationships were found between heavy metal concentrations in all plant organs and those in water and sediment, thus indicating the potential use of such organs for pollution monitoring of water and sediment. Advantages of using plant species as biomonitors, especially Phragmites australis, were also discussed.     

Metal accumulation and metallothionein induction in the spotted dogfish Scyliorhinus canicula

Recent studies indicate that elasmobranch fish respond differently to metal exposure than marine teleosts. Accumulation rates can be high, which despite the fact that normal background levels for metals in the marine environment are low, is worrying due to the long life span and late fecundity of most shark. The goals of the present study were to examine differences in accumulation rates and toxicity of a range of metals at equimolar concentrations (10 µM) in the Mediterranean or spotted dogfish, Scyliorhinus canicula. For this purpose, we exposed the dogfish to Ni (587 µg/L), Cd (1124 µg/L), Pb (2072 µg/L), Cu (635 µg/L), and Ag (1079 µg/L and two additional exposures at 10 µg/L and 1 µg/L) for one week and measured total metal accumulation, metallothionein induction, and parameters related to osmoregulation. Our study confirms the high toxicity and accumulation rates of Ag for elasmobranch fish, even at levels 100 to 1000 times lower than exposure levels of other metals. Also Pb accumulated readily in all organs, but did not cause any osmoregulatory disturbance at the exposure levels used. Ni and Cd seem to accumulate primarily in the kidney while Cu mainly accumulated in liver. In contrast to Ni and Cd, the three other metals Ag, Cu and Pb accumulated in the rectal gland, an important organ for osmoregulation and possible target organ for metal toxicity. Only Cu succeeded in initiating a protective response by inducing MT synthesis in liver and gills.     

Heavy metals in wetland soils along a wetland-forming chronosequence in the Yellow River Delta of China: Levels,sources and toxic risks

Surface soil (0–20 cm) samples were collected from four chronological sequences of wetlands (i.e., >50-yr-old wetlands, 40-yr-old wetlands, 30-yr-old wetlands and 10-yr-old wetlands) in the Yellow River Delta of China in May and June of 2007. Total contents of Al, As, Cd, Cr, Cu, Ni, Pb and Zn were determined using inductively coupled plasma atomic absorption spectrometry (ICP-AAS) to investigate the levels, sources and toxic risks of heavy metals in these wetlands. Our results showed an increasing trend for Pb, Cu and Zn along the wetland-forming chronosequence although their pollution levels were low. Both As and Cd exhibited significant enrichment due to their high enrichment factor (EF) values (EF > 5), especially in older wetlands (i.e., >50-yr-old and 40-yr-old wetlands), whereas other heavy metals were minimally or moderately enriched in this region. The results of principal component analysis showed that 83.09% of total variance based on eigenvalues (eigenvalue > 1) could be explained by three principal components (PCs) in four wetlands. The source of Al, Cu, Pb and Zn was different from Cd, Cr and Ni. According to the sediment quality guidelines (SQGs) of China, soil samples in the younger wetlands, especially the 10-yr-old wetlands, were moderately polluted by As, Cd and Ni. According to the SQGs of US EPA, all soil samples were heavily polluted by As and moderately polluted by Ni and soil samples in the older wetlands were moderately polluted by Cr. However, with the exception of As and Ni, the contents of other heavy metals in the four wetlands did not exceed the probable effect level (PEL) values. As, Cd and Ni were identified as heavy metals of primary concerns in four wetlands, Cr were of moderate concern in older wetlands, and Pb, Cu and Zn should be paid more attention in younger wetland (i.e., 10-yr-old and 30-yr-old wetlands). A new and sensitive toxic risk index (TRI) is developed for the accurate assessment of toxic risk for heavy metals in wetland soils compared with the sum of the toxic units (∑TUs), and As, Cr, Ni and Cd showed higher contributions to TRI.     

Desarrollo de un bioadsorbente laminar con Phanerochaete chrysosporium hipertolerante al cadmio,al níquel y al plomo para el tratamiento de aguas

BackgroundThe use of basidiomycetes for metal removal is an alternative to traditional methods. In this, the biomass acts as a natural ionic exchanger removing metals from solution.ObjectiveTo develop a laminar biosorbent using a basidiomycete fungus resistant to high Cd, Ni and Pb concentrations.MethodsThe tolerance of Trametes versicolor, Pleurotus ostreatus and Phanerochaete chrysosporium was evaluated using increasing concentrations of the heavy metal salts, cadmium sulphate, lead acetate and nickel chloride. A biosorbent system was developed based on polyethylene sheets with a fungal biomass. It was evaluated in bubble columns using synthetic wastewater with the 3 metal salts at a rate of 300 mg/l. Finally, in a complementary experiment using shake flasks, the effect of a higher amount of biomass related to the metal removal efficiency was evaluated.ResultsP. chrysosporium strain was more tolerant to C₄H₆O₄Pb (10,000 mg/l), Cl₂Ni (300 mg/l) and CdSO₄·8H₂O (1,500 mg/l). In a reactor, under non-ligninolytic conditions, the fungus removed 69% of the chemical oxygen demand and produced enzymes such as LiP (0.01 U/l) and MnP (0.6 U/l.). An accumulation of metals in the wall was observed. By increasing the biomass to 1.6 (w/v), the metal biosorption was favored in the mixture (57% Pb, 74% Cd, and 98% Ni) and separately (95% Pb, 60% Cd, and 56% Ni). Competition between Ni and Pb by ligands of the wall was observed.ConclusionA novel laminar system based on P. chrysosporium viable biomass was developed. It has a large surface area and tolerance to high concentrations of Cd, Ni and Pb. It seems to be an alternative for the removal of metals from water.     

Heavy metal pollution in surface water and sediment: A preliminary assessment of an urban river in a developing country

The concentration and chemical fractionation of globally alarming six heavy metals (Cr, Ni, Cu, As, Cd and Pb) were measured in surface water and sediment of an urban river in Bangladesh. The decreasing trend of metals were observed in water as Cr > Cu > As > Ni > Pb > Cd and in sediment as Cr > Ni > Cu > Pb > As > Cd. The level of studied metals exceeded the safe limits of drinking water, indicated that water from this river is not safe for drinking and/or cooking purposes. However, the investigated metals showed low mobility except for Cd and Pb which could pose a severe threat to the aquatic environment. Contamination factor (CF) and geoaccumulation index (I_geo) demonstrated that most of the sediment samples were moderately to heavily contaminated by Cr, As, Cd and Pb. The pollution load index (PLI) values were above one (>1) indicates progressive deterioration of the sediment quality. The extent of pollution by heavy metals in the river Korotoa implies that the condition is much frightening to the biota and inhabitants in the vicinity of the river as well.     

Role of the Ca-pectates on the accumulation of heavy metals in the root apoplasm

In order to better understand the processes that regulate the accumulation in the apoplasm of heavy metals and their mobilization by the plant metabolites it is essential to study the mechanisms that regulate the interactions between metal ions and pectins. In such a context, the sorption of Cd(II), Zn(II), Cu(II) and Pb(II) from single and multi-metal solutions, by a Ca-polygalacturonate gel with a degree of esterification of 18.0 (PGAM₁) and 65.5% (PGAM₂) was studied in the 3.0–6.0 pH range in the presence of CaCl₂ 2.5 mM. The sorption of Cr(III) from single metal solution was also considered. The results show that the amount of each metal ion sorbed increases with increasing the initial metal ion concentration and pH. The data from the single metal solution tests show that at pH 6.0 the affinity of the metal ions towards the PGAM₁ matrix follows the order: Cr(III) > Cu(II) ? Pb(II) ? Zn(II) ? Cd(II). The simultaneous sorption of the bivalent metal ions by the PGAM₁ gels indicates that Pb(II) is selectively sorbed. The FT-IR spectra show that the carboxylate groups are mainly responsible for the metal ion coordination. The ability of PGAM₂ to accumulate Cr(III), Cu(II), and Pb(II) was lower than that found in the PGAM₁ systems whereas the sorption of Zn(II) and Cd(II) was negligible.     

Distribution and enrichment of heavy metals among sediments,water body and plants in Hengshuihu Wetland of Northern China

In this study, a survey for the spatial distribution of heavy metals in Hengshuihu Wetland of China was conducted. Samples were collected from three compartments, water, sediment, and reed (Phragmites communis Trin), at different sites, and their contents of heavy metals, including mercury (Hg), arsenic (As), chromium (Cr), lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd), were analyzed. The results showed heavy metals in the sediments distributed in the Buffer Zone and Wangkou Sluice area at concentrations relatively higher than those in other areas, while concentrations in the Core Zone were lower. The heavy metal concentrations of water bodies in all areas, except those for Hg and Pb, were lower than the cutoff values for the first-grade water quality that was set as the highest standard to protect the national nature reserves. The heavy metal distributions among the three compartments were significantly different, with the following order: sediment > plant > water. In the reeds, accumulated amounts of different heavy metals varied in the following order: Hg > Zn > As > Cu > Cr. Concentrations of heavy metals only showed weak correlations between the water bodies and the sediments. Concentrations of heavy metals (except Hg and Cr) had no corrections between the sediments and the reeds. The distribution of mercury indicated that it enters the lake mainly from the atmosphere and outside water bodies. The concentrations of As, Hg, Cr, Cu and Zn in different parts of the reeds were detected and their abundances were ranked in the following order: root > leaf > stem.     

Physiologically based extraction of heavy metals in compost: Preliminary results

A physiologically based extraction test (PBET) was run for the extraction of six metals (Cu, Zn, Cd, Cr, Ni and Pb) in four composts containing high concentrations of heavy metals. An aqueous solution of pepsin plus citric, acetic, and malic acids buffered to pH 2 was used to simulate the gastric mixture, and an extraction of 1 h at 37 °C was run with a solid:liquid ratio of 1:100. The results were compared to those obtained using water and CaCl₂–DTPA solution. The PBET extracted far more metals than water, but less than CaCl₂–DTPA for Cu, Pb and Cr, while giving similar or slightly lower results for Cd, Zn, and Ni.     

Continuous fixed-bed column study and adsorption modeling: Removal of cadmium (II) and lead (II) ions in aqueous solution by dead calcareous skeletons

The sorption of Cd(II) and Pb(II) ions was conducted in a continuous fixed-bed column by using dead calcareous skeletons (CS). The column performances were evaluated by varying the adsorbent bed height, influent flow rate and metals initial concentration. The breakthrough curve for the bed height indicated that a longer bed column prolonged the life span of the column with a maximum capacity of 26.447 and 38.460 mg/g for the Cd(II) and Pb(II) column, respectively. The increased flow rate and initial concentration caused the column exhaustion time to occur earlier. The experimental column data were also expressed in column adsorption models, namely, the Thomas, Yoon–Nelson and Adam–Bohart models. The Thomas model fitted well with the Cd(II) data with the correlated curve (r² > 0.9). The Yoon–Nelson model was selected to predict the 50% breakthrough time achieved by the column system and provided the estimated breakthrough time for the columns that were not exhausted during the operation. The Adam–Bohart model was applicable for the initial part of adsorption with the saturation concentration data at the equilibrium. The saturation index of aragonite and calcite depicted that dissolution of calcium occurred in the aqueous solution. The experimental and theoretical data were correlated with a significant relationship trend (p < 0.01), which showed that the trend of experimental data fit well with the modeling trend. The trends of both the experimental and theoretical data were strongly and significantly correlated due to involving the column parameters and the components of CS.     

Lead,zinc, cadmium hyperaccumulation and growth stimulation in Arabis paniculata Franch

Metal hyperaccumulation is of great interest in recent years because of its potential application for phytoremediation of heavy metal contaminated soils. In this study, a field survey and a hydroponic experiment were conducted to study the accumulation characteristics of lead (Pb), zinc (Zn) and cadmium (Cd) in Arabis paniculata Franch., which was found in Yunnan Province, China. The field survey showed that the wild population of A. paniculata was hyper-tolerant to extremely high concentrations of Pb, Zn and Cd, and could accumulate in shoots an average level of 2300 mg kg^?1 dry weight (DW) Pb, 20,800 mg kg^?1 Zn and 434 mg kg^?1 Cd, with their translocation factors (TFs) all above one. Under the hydroponic culture, stimulatory effects of Pb, Zn and Cd on shoot dry biomass were noted from 24 to 193 μM Pb, 9 to 178 μM Cd and all Zn supply levels in nutrient solution, while the effects were not obvious in the roots. Chlorophyll concentrations in Pb, Zn and Cd treatments showed an inverted U-shaped pattern, consistent with the change of plant biomass. Pb, Zn and Cd concentrations in the shoots and roots increased sharply with increasing Pb, Zn and Cd supply levels. They reached > 1000 mg kg^?1 Pb, 10,000 mg kg^?1 Zn and 100 mg kg^?1 Cd DW in the 24 μM Pb, 1223 μM Zn and 9 μM Cd treatment, respectively, in which the plants grew healthy and did not show any symptoms of phytotoxicity. The TFs of Zn were basically higher than one and the amount of Zn taken by shoots ranged from 78.7 to 90.4% of the total Zn. However, the TFs of Pb and Cd were well below one, and 55.0–67.5% of total Pb and 57.8–83.5% of total Cd was accumulated in the shoots. These results indicate that A. paniculata has a strong ability to tolerate and hyperaccumulate Pb, Zn and Cd. Meanwhile, suitable levels of Pb, Zn and Cd could stimulate the biomass production and chlorophyll concentrations of A. paniculata. Thus, it provides a new plant material for understanding the mechanisms of stimulatory effect and co-hyperaccumulation of multiple heavy metals.     

Metal uptake by medicinal plant species grown in soils contaminated by a smelter

The hypothesis tested in this study was if medicinal plants could be grown as alternative crops in heavy metal polluted soils without contamination of the final marketable produce. Furthermore, medicinal crops may offer a phytoremediation option for mildly heavy metal polluted agricultural soils. The effect of metal-enriched soils was evaluated in five medicinal species (Bidens tripartita L., Leonurus cardiaca L., Marrubium vulgare L., Melissa officinalis L. and Origanum heracleoticum L.). Soils were sampled in the vicinities of the Non-Ferrous Metals Combine (Pb–Zn smelter) near Plovdiv, Bulgaria, from plots at 0.5 km (soil 1), 3 km (soil 2), 6 km (soil 3) and 9 km (control soil) from the smelter. Cadmium, Pb and Zn concentration in soil 1 were above the critical total (HNO₃-extractable) concentrations for these elements in soils. Generally, heavy metals in soil 1 decreased dry mater yields of the five species relative to the control. However, the essential oil content of M. vulgare, M. officinalis and O. heracleoticum was within the usual range for respective species and was not affected by the treatments. The overall metal uptake was in the order: B. tripartita > M. vulgare > O. heracleoticum > L. cardiaca > M. officinalis for Cd, L. cardiaca = M. vulgare > B. tripartita = M. officinalis = O. heracleoticum for Pb, L. cardiaca = M. vulgare > O. heracleoticum > B. tripartita = M. officinalis for Cu and B. tripartita > L. cardiaca = M. vulgare > M. officinalis = O. heracleoticum for Mn and Zn. Overall, metal concentration in plant parts was in the order: roots > leaves > flowers > stems for Cd, Pb and Cu, leaves > roots > flowers > stems for Mn and Zn. The concentration of Cd, Pb, Cu and Zn in plant tissue correlated to the exchangeable (EXCH) and the carbonate (CARB) bound fractions of metals in soil. Heavy metals caused disruptions of the plasma membrane of some root cortical cells and alterations in chloroplasts thylakoids in plants grown in soil 1. Metal content in teas prepared from the species was negligible, the essential oils were free of metals. Generally, the transfer factor (TF) was less than 1, indicating the tested species did not have a significant phytoextraction potential. This study demonstrated the three essential oil species M. vulgare, M. officinalis and O. heracleoticum can be grown as alternative high-value crops in metal polluted agricultural soils around the smelter and provide metal-free marketable produce.     

Metal uptake by medicinal plant species grown in soils contaminated by a smelter

The hypothesis tested in this study was if medicinal plants could be grown as alternative crops in heavy metal polluted soils without contamination of the final marketable produce. Furthermore, medicinal crops may offer a phytoremediation option for mildly heavy metal polluted agricultural soils. The effect of metal-enriched soils was evaluated in five medicinal species (Bidens tripartita L., Leonurus cardiaca L., Marrubium vulgare L., Melissa officinalis L. and Origanum heracleoticum L.). Soils were sampled in the vicinities of the Non-Ferrous Metals Combine (Pb–Zn smelter) near Plovdiv, Bulgaria, from plots at 0.5 km (soil 1), 3 km (soil 2), 6 km (soil 3) and 9 km (control soil) from the smelter. Cadmium, Pb and Zn concentration in soil 1 were above the critical total (HNO₃-extractable) concentrations for these elements in soils. Generally, heavy metals in soil 1 decreased dry mater yields of the five species relative to the control. However, the essential oil content of M. vulgare, M. officinalis and O. heracleoticum was within the usual range for respective species and was not affected by the treatments. The overall metal uptake was in the order: B. tripartita > M. vulgare > O. heracleoticum > L. cardiaca > M. officinalis for Cd, L. cardiaca = M. vulgare > B. tripartita = M. officinalis = O. heracleoticum for Pb, L. cardiaca = M. vulgare > O. heracleoticum > B. tripartita = M. officinalis for Cu and B. tripartita > L. cardiaca = M. vulgare > M. officinalis = O. heracleoticum for Mn and Zn. Overall, metal concentration in plant parts was in the order: roots > leaves > flowers > stems for Cd, Pb and Cu, leaves > roots > flowers > stems for Mn and Zn. The concentration of Cd, Pb, Cu and Zn in plant tissue correlated to the exchangeable (EXCH) and the carbonate (CARB) bound fractions of metals in soil. Heavy metals caused disruptions of the plasma membrane of some root cortical cells and alterations in chloroplasts thylakoids in plants grown in soil 1. Metal content in teas prepared from the species was negligible, the essential oils were free of metals. Generally, the transfer factor (TF) was less than 1, indicating the tested species did not have a significant phytoextraction potential. This study demonstrated the three essential oil species M. vulgare, M. officinalis and O. heracleoticum can be grown as alternative high-value crops in metal polluted agricultural soils around the smelter and provide metal-free marketable produce.     

Biochemical responses of the aquatic moss Fontinalis antipyretica to Cd,Cu, Pb and Zn determined by chlorophyll fluorescence and protein levels

Biochemical reactions to Cu, Cd, Zn and Pb in the aquatic moss Fontinalis antipyretica were studied in order to characterize the physiological background of the metal response. Chlorophyll fluorescence and intracellular metal localization and stress protein levels were measured. Exposure to 25 or 100 μM Cu over a 7-day period resulted in a decline of chlorophyll fluorescence to about 70% and 52%, respectively. Up to 100 μM Cd caused a decrease in chlorophyll fluorescence to 75%. With all metals used at 25–100 μM concentrations, the intracellular uptake increased. For all metals investigated at 25–100 μM, the intracellular uptake increased. Maximum values were reached at 100 μM Cu, Pb, Zn or Cd exposure. As shown by analytical electron microscopy (EDX, EELS) moss material treated with 50 μM Cu exhibited reduced sulphur levels in the cytoplasm and an increase in phosphate in vacuolar dense particles. EEL-spectra indicated that Cu is chelated in the cytoplasm by SH-groups and coprecipitated with orthophosphate in vacuoles. To monitor the stress response at the protein level, heavy metal induced heat shock protein 70 (hsp70) was measured. An antibody was raised against conserved plant metallothionein p2 motifs derived from Brassica juncea. In all metal-treated samples the antibody bound to proteins of about 8 kDa. However, sequencing failed to reveal significant homologies to known proteins. These experiments provide for the first time results on protein level after heavy metal stress in the aquatic bioindicator moss.     

Bioaccumulation of heavy elements by Armadillidium vulgare (Crustacea,Isopoda) exposed to fallout of a municipal solid waste landfill

This paper reports the response of isopods exposed to fallout of a municipal solid waste landfill located in central Italy. Soil samples and specimens of Armadillidium vulgare were collected at different distances from the landfill and analyzed to determine the concentrations of heavy elements such as As, Cd, Co, Cr, Cu, Ni, Pb, Sb, V and Zn. The isopod analysis was performed on unpurged and purged specimens. Analytical data indicate that the soil contents of heavy elements were quite uniform and within the respective local geochemical background. Slight enrichments of Cu and Pb were found in some soils collected within the solid waste. Purged isopods showed an accumulation of As, Co, Cr, Ni, Sb and V whose body levels decreased as the distance from the landfill increased. Cd, Cu, Pb and Zn concentrations in purged specimens were rather uniform and no significant variation trend occurred. This result probably was due to the fact that the isopods are provided with physiological mechanisms of regulation for these heavy elements. Analytical data also indicate the ability of A. vulgare to adsorb differently the heavy elements according to the following order: As > Co > Ni > Pb > V. The contents of heavy elements in unpurged specimens were higher than in purged ones. This finding suggested that the defecation has marked effects on the tissue levels of heavy elements in isopods. This study indicates that the isopods provide useful information about environmental quality in areas characterized by low and discontinuous emission of heavy elements and their low accumulation in soil.     

Response of native grasses and Cicer arietinum to soil polluted with mining wastes: Implications for the management of land adjacent to mine sites

Mine tailings are an environmental problem in Southern Spain because wind and water erosion of bare surfaces results in the dispersal of toxic metals over nearby urban or agricultural areas. Revegetation with tolerant native species may reduce this risk. We grew two grasses, Lygeum spartum and Piptatherum miliaceum, and the crop species Cicer arietinum (chickpea) under controlled conditions in pots containing a mine tailings mixed into non-polluted soil to give treatments of 0%, 25%, 50%, 75% and 100% mine tailings. We tested a neutral (pH 7.4) mine tailings which contained high concentrations of Cd, Cu, Pb and Zn. Water-extractable metal concentrations increased in proportion to the amount of tailings added. The biomass of the two grasses decreased in proportion to the rate of neutral mine-tailing addition, while the biomass of C. arietinum only decreased in relation to the control treatment. Neutron radiography revealed that root development of C. arietinum was perturbed in soil amended with the neutral tailings compared to those of the control treatment, despite a lack of toxicity symptoms in the shoots. In all treatments and for all metals, the plants accumulated higher concentrations in the roots than in shoots. The highest concentrations occurred in the roots of P. miliaceum (2500 mg kg^?1 Pb, 146 mg kg^?1 Cd, 185 mg kg^?1 Cu, 2700 mg kg^?1 Zn). C. arietinum seeds had normal concentrations of Zn (70–90 mg kg^?1) and Cu (6–9 mg kg^?1). However, the Cd concentration in this species was ～1 mg kg^?1 in the seeds and 14.5 mg kg^?1 in shoots. Consumption of these plant species by cattle and wild fauna may present a risk of toxic metals entering the food chain.     

Monitoring of trace metals in tissues of Wallago attu (lanchi) from the Indus River as an indicator of environmental pollution

We aimed to assess the bioaccumulation of selected four trace metals (Cd, Ni, Zn and Co) in four tissues (muscles, skin, gills and liver) of a freshwater fish Wallago attu (lanchi) from three different sites (upstream, middle stream and downstream) of the Indus River in Mianwali district of Pakistan. Heavy metal contents in water samples and from different selected tissues of fish were examined by using flame atomic absorption spectrometry. The data were statistically compared to study the effects of the site and fish organs and their interaction on the bioaccumulation pattern of these metals at P < 0.05. In W. attu the level of cadmium ranged from 0.004 to 0.24; nickel 0.003–0.708; cobalt 0.002–0.768 and zinc 47.4–1147.5 μg/g wet weight. The magnitude of metal bioaccumulation in different organs of fish species had the following order gills > liver > skin > muscle. The order of bioaccumulation of these metals was Ni < Zn < Co < Cd. Heavy metal concentrations were increased during the dry season as compared to the wet season. The results of this study indicate that freshwater fish produced and marketed in Mianwali have concentrations below the standards of FEPA/WHO for these toxic metals.     

Earthworms as bioindicator of metals (Zn,Fe, Mn,Cu, Pb and Cd) in soils: Is metal bioaccumulation affected by their ecological category?

The importance of earthworms in metal pollution monitoring is widely recognized in terrestrial ecosystems. Metal bioaccumulation by soil-dwelling earthworms can be used as an ecological indicator of metal availability in soils. In this study, we quantify the level of DTPA extractable metals in casts and tissues of earthworms (endogeic: Metaphire posthuma (Vaillant) and anecic: Lampito mauritii Kinberg) and ingesting soils, collected form cultivated land, urban garden and sewage soils. Soil and worm casts collected from sewage and cultivated land showed the greater metal concentrations. The concentration of Zn, Fe, Pb and Mn in earthworm casts was in the order: sewage soil > cultivated land > urban garden, while for Cu and Cd the order was cultivated land > sewage soil > urban garden. Data suggested that the level of DTPA extractable metals was higher than that of surrounding soils. We got close relationships between metal concentration in worm tissues and surrounding soils: Zn (r² = 0.94 and 0.89, P < 0.01 for both), Fe (r² = 0.95 and 0.97, P < 0.01 for both), Cu (r² = 0.93 and 0.96, P < 0.01), Pb (0.63, P < 0.01 and 0.57, P > 0.05), and Cd (r² = 0.15, P > 0.01 and 0.75, P < 0.01), respectively, for M. posthuma and L. mauritii. The study clearly indicates that earthworms have efficient potentials for bioaccumulation of metals in their tissues which can be used as an ecological indicator of soil contaminations. A species-specific metal accumulation pattern was observed in studied earthworms. Comparatively, endogeic showed the higher metal contents in their tissues than anecic (t-test: P < 0.05); collected form different habitats studied. Data suggested that species-specific feeding behaviour, earthworm niche structure, ecological category of inhabiting earthworm and even horizontal distribution of contaminants in soil layers are some major determinant for metal accumulation patterns in soil dwelling earthworms. The difference in burrowing patterns can influence the patterns of metal bioaccumulations between endogeic and anecic, although other factors are also contributory. Further more detailed study is still required to elaborate the proposed hypothesis.     

Role and characteristics of problematic biofilms within the removal and mobility of trace metals in a pilot-scale membrane bioreactor

The characteristics of problematic biofilms (i.e., fouling and clogging layers) were studied with regards to the removal and fate of trace metals (contents well under 100 μg/L) during the long-term operation of a pilot-scale membrane bioreactor for the treatment of real wastewaters from a large industrial area.Results showed that clogging layer was more effective than suspended activated sludge in the biosorption of As > Zn > Ni > Cd > Sb > Fe > Se due to the synergic effects of extracellular polymeric compounds and metal-resistant bacteria. In fact the selective microbial speciation of the phylum of Bacteroidetes, which is highly resistant to heavy metals, was observed in the clogging sludge in spite of the very low concentration of dissolved metals in the bioreactor.Compared to the suspended activated sludge, the clogging layer enhanced the biosorption of very toxic substances such as As, Cd and Ni. In fact, the metal contents were respectively: 7.9–7.4 vs. 690–840 μgAs/kgTS; 1.5–2.2 vs. 149–219 μgCd/kgTS; 58.8–71.7 vs. 227–298 μgNi/kgTS. Then, the potential desorption of metals during the membrane acid cleanings was estimated as relevant as 10–15% of the metals associated to the clogging sludge. The combined effects of pH and the selected microbial community, and the minor effect of the redox potential, let us conclude on the major importance of bio-sorption/desorption mechanisms with respect to bio-precipitation/dissolution.     

Population health risk due to dietary intake of toxic heavy metals from Spinacia oleracea harvested from soils collected in and around Tshwane,South Africa

In order to assess the possible health risk associated with the consumption of vegetables harvested from waste dump sites, trace metal levels in Spinacia oleracea planted in soils collected from waste dump sites were investigated. Soil samples from different waste dump sites and mining areas were collected and placed in different pots. Seedlings of S. oleracea were introduced into the pots, harvested after 3 months and analysed for trace metal contents using ICP-MS. From the leaves of the plants, the concentration of Fe was found to be significantly higher than all other trace metals (p < 0.05). The trend in trace metal accumulation from the leaves was in the order Fe > Mn > Zn > Pb > Cu > Cr > Ni > Cd. A significantly different concentration of trace metals in the plant was noticed from different soils in different pots used (p < 0.05). Trace metal concentration from plant parts showed roots > leaves > stem. The risk to human health indicated as Hazard Quotient (HQ) was highest for Zn followed by Cu from all the plant parts. The HQ result showed that humans might be at risk if they consume spinach from these waste dump sites. From the study it was concluded that harvesting/consuming spinach from soil around a waste dump site may be extremely dangerous.     

The concentrations of major and trace elements in rat kidney: Aging effects and mutual relationships

The concentrations of 26 major to trace elements in rat kidneys aging from 5 to 113 weeks old were determined. The rats investigated were the same rats used previously reported to have 29 elements in bones (femurs). The samples were decomposed by high purity nitric acid and hydrogen peroxide. Eight elements (Na, Mg, Si, P, K, Ca, Fe and Zn) were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES) and 18 elements (Mn, Co, Ni, Cu, As, Se, Rb, Sr, Mo, Cd, Sn, Sb, Cs, Ba, Tl, Pb, Bi and U) were determined using inductively coupled plasma mass spectrometry (ICP-MS). The aging effects on the concentrations of these elements and mutual elemental relationships were investigated. Analysis of variance (ANOVA) for age variations indicated that the concentrations of P, K, Mn and Mo were almost constant across the age of rats (p > 0.3). The concentration of many elements such as Na, Mg, Ca, Fe, Co, Cu, Zn, As, Se, Cd, Sn, Sb, Tl, Pb and Bi, showed significant increasing trends (p < 0.01) with different patterns. Rubidium, Cs, Pb and Bi showed significant age variations but not monotonic trends. Silicon, Ni, Sr, Ba and U showed large concentration scatterings without any significant trends (p > 0.01). The metabolism of these elements may not be well established in the kidney. Many toxic elements such as As, Cd, Sn, Pb and Bi showed a narrow concentration range among age-matched rats. The kidney may have established metabolic mechanisms to confine or accumulate these toxic elements even though their concentrations are very low (e.g., 10 ng g^?1 of Cd). These elements also closely coupled with Fe. A cluster analysis was performed using an elemental correlation matrix and indicated that these elements, including Fe, formed a cluster. However, another cluster analysis using “an aging effect eliminated” elemental correlation showed different clustering in which the Fe, Cd cluster disappeared.