The interaction of heavy metals with urban soils: sorption behaviour of Cd, Cu, Cr, Pb and Zn with a typical mixed brownfield deposit

This study investigated the sorption characteristics and release of selected heavy metals (Cd, Cu, Cr, Pb and Zn) from a typical urban soil material from a derelict brownfield site in Western Scotland, UK. The study aimed to evaluate contaminant interactions with an urban substrate, comprising a mix of mineral soil and residue materials (e.g. brick, concrete, wood). This type of material has received little consideration in the literature to date. Soil samples were subject to a sequence of test involving batch equilibration and dynamic leaching, in single (non-competitive) and multi-element (competitive) solutions. The batch experiments were carried out in unadjusted and close to soil field pH conditions (pH 2 and 7, respectively). The equilibrium adsorption capacity for heavy metals was measured and extrapolated using the Langmuir isotherm. The parameters of the isotherms x(m) (the maximum amount adsorbed per unit mass of adsorbent (mg/g)) and b (adsorption constant (m(3)/g)) were calculated for Cd, Cu, Cr, Pb as single-element and multi-element solutions. The adsorption from the single-element solution was more effective than adsorption under multi-element conditions, due to competitive effects. For example, the adsorption of copper from a single-element solution was over four times greater than for a multi-element solution. In the case of Cr and Zn, migration of metal from soil to solution was observed. Adsorption capacity at pH 2 followed the order Cr>Cu>Pb>Cd and at pH 7 Cd>Zn, with precipitation affecting Cu and Pb behaviour. During the column leaching experiment, most of the heavy metals were irreversibly bound to the soil, but in the case of Cr some movement from soil into solution was observed. The results also showed that Cd, Cu, Pb and Zn were removed from the solution and adsorbed on the soil. No significant difference in the metal removal from single- and multi-element solutions was observed. Overall, the urban residue behaved in a similar manner to mineral soils despite a significant component of anthropogenic solid materials.     

Evaluation of the sensitivity of marine microalgal strains to the heavy metals, Cu, As, Sb, Pb and Cd

The sensitivity of nine marine microalgal species (consisting of five divisions and seven genera) to the five heavy metals, Cu(II), As(V), Sb(III), Pb(II) and Cd(II) was studied by using a fluorometric growth-inhibition assay with 96-well microplates. The algal strains studied were Cylindrotheca sp. and the LPP group that respectively characterize aggregating and filamentous types, and Chlorococcum littorale, Chlorococcum sp., Isochrysis galbana, Tetraselmis tetrathele, Heterocapsa sp., Synechococcus sp. and Prasinococcus sp. for types that occur as single cells. A good linear relationship was observed between the chlorophyll a concentration and intensity of chlorophyll fluorescence (485-nm excitation filter and 645-nm emission filter) when the chlorophyll a concentration was within the range of 0.10-5.0 microg ml(-1). A starting cell concentration of 0.10 or 0.25 microg Chl a ml(-1) was therefore selected. In accordance with OECD 201 standard procedures, the IC(50) value (concentration of a metal producing 50% growth inhibition relative to the control) was determined 72 h after adding a heavy metal by using the biomass integral. The microplate toxicity test used in this study is considered to be applicable to diverse algae, not only enumerating species but also hardly enumerating ones.     

Study on the behavior of the heavy metals Cu, Cr, Ni, Zn, Fe, Mn and 137Cs in an estuarine ecosystem using Mytilus galloprovincialis as a bioindicator species: the case of Thermaikos gulf, Greece

Mussels are worldwide recognized as pollution bioindicators and used in Mussel Watch programs, because they accumulate pollutants in their tissues at elevated levels in relation to pollutant biological availability in the marine environment. The present study deals with the use of Mytilus galloprovincialis as a local bioindicator of heavy metal and (137)Cs contamination in an estuarine ecosystem (Thermaikos gulf, Greece in Eastern Mediterranean). M. galloprovincialis samples were collected monthly from two aquaculture farms during the period April to October 2000. Analyses for the heavy metals Cu, Cr, Ni, Zn, Fe, Mn and (137)Cs showed that the concentrations measured were low and similar to those from other non-polluted Mediterranean areas. In terms of the two sampling stations, there were no statistically significant differences between them. On the contrary, the seasonal evolution of either heavy metals or (137)Cs levels presented high variation. The levels were found to increase during the cold period of the year, especially for Cu, Zn, Mn and Cr which are essential for life. Stable metals were positively inter-related and moreover, metals more involved in biochemical activities seem to present more correlations than others with less significant role in the metabolism of the organisms.     

The relationship of dissolved Pb to some dissolved trace metals (Al, Cr, Mn, and Zn) and to dissolved nitrate and phosphate in a freshwater aquatic system in Mauritius

The relationship of some dissolved trace metals (Al, Cr, Mn, Zn, and Pb) with one another and to dissolved phosphate and nitrate in a freshwater aquatic system at Flic en Flac and Grand River North West (GRNW) in Mauritius (1850 km2, 20 degrees S and 57 degrees E, Western Indian ocean) is reported following trace metal determination using inductively coupled plasma mass spectrometry (ICP-MS). Dissolved Al (<200 ng ml(-1)), Cr (<50 ng ml(-1)), Mn (<50 ng ml(-1)), Zn (< 100 ng ml(-1)), and Pb (<50 ng ml(-1)) upstream, downstream GRNW and in the marshes and rivulet at Flic en Flac were found to be below the recommended EEC maximum admissible concentrations and within the ambient drinking water quality standards in Mauritius. Dissolved Pb was significantly positively correlated to both dissolved Cr and Zn suggesting that the cycling for dissolved Pb is linked to the cycling of both dissolved Cr and Zn along GRNW. The common influential cycling of Pb and Zn was further reinforced as both dissolved Pb and Zn were significantly positively correlated to dissolved phosphate, which suggested a biological role in the cycling of Zn and Pb. The role of biological activity or adsorption to biological systems in Pb cycling along GRNW is further suggested as dissolved Pb was significantly correlated to dissolved nitrate. The apparent absence of the dissolved Al, Cr, and Mn with dissolved nitrate and phosphate could be attributed to factors such as the lower sensitivity of the GRNW to metal uptake during biological activity during the time frame considered. The cycling of dissolved Al and Mn was also not linked to the cycling of Cr, Zn, and Pb as no significant correlation was found along GRNW.     

Accumulation of Cu,Zn, Cd,and Pb by Scenedesmus obliquus under nongrowth conditions

The aim of this work has been to assess the accumulation of copper, zinc, cadmium and lead by a test alga, Scenedesmus obliquus, under nongrowth conditions. The results provide an evidence that metals can be readily accumulated by algae and that accumulation is a function of the metal-to-algae exposure ratio. When the metals were added in combination in equimolar concentrations, the following order of affinity to algal surface was detected Zn > Cu ? Cd > Pb. However, when EDTA was added to the test water, metal accumulation was greatly retarded. Moreover, when algae loaded with one of the metals were washed with EDTA solution the major part of the accumulated metal was mobilized, indicating that EDTA had stronger metal binding affinity than any ligands liable to exist on algal surface. Metal accumulation by algal cells isolated from a culture in the logarithmic growth phase was of much higher magnitude than that displayed by cells isolated from a culture in the decline phase.     

Accumulation of Pb, Cd, Cu and Zn in plants and hyperaccumulator choice in Lanping lead-zinc mine area, China

A field survey of higher terrestrial plants growing on Lanping lead-zinc mine, China were conducted to identify species accumulating exceptionally large concentrations of Pb, Cd, Cu and Zn of 20 samples of 17 plant species. Concentrations of Pb and Zn in soil and in plant were higher than that of Cu and Cd. Significant difference was observed among the average concentrations of four heavy metals in plants (except Cd and Cu) and in soil (except Pb and Zn) (P<0.05). For the enrichment coefficient of the four heavy metals in plant, the order of average was Pbtree>herbaceous, and herbaceous grew in soil with the highest concentrations of four heavy metals. In different areas, the concentrations of Pb, Cd, Cu and Zn in plants and soils and enrichment coefficient were different. Plants in Paomaping had more accumulating ability to Pb, Cd and Zn, and plants in Jinfeng River had more accumulating ability to Cu. Six plant species, i.e. S. cathayana, Lithocarpus dealbatus, L. plyneura, Fargesia dura, Arundinella yunnanensis and R. annae in Paomaping, had high accumulation capacity. R. annae in Paomaping had hyperaccumulating capacity to Pb, Cd and Zn, L. plyneura to Pb and Cd, and S. cathayana to Cd, respectively.     

Chemical speciation and phytoavailability of Zn, Cu, Ni and Cd in soil amended with fly ash-stabilized sewage sludge

A sequential extraction method was used to determine chemical forms of Cu, Zn, Ni and Cd in fly ash-stabilized sludge. A loamy acid soil amended with fly ash-stabilized sludge was used to grow corn under greenhouse conditions. Sewage sludge amended with coal fly ash can reduce the availability of Cu, Zn, Ni and Cd in the sludge. Increasing fly ash amendment rate significantly reduced DTPA-extractable Cu, Zn, Ni and Cd concentrations. Percentages of Cu, Zn and Ni in residual fraction increased with an increase in fly ash amendment rates. Majority of Cu was associated with organic form, but Zn and Ni were associated with Fe-Mn oxide and residual forms. Addition of ash-amended sludge to soil significantly increased dry mass of corn. With coal fly ash amendment rate increasing, concentrations of Zn and Cu in shoot tissues of corn decreased significantly, but concentrations of Cd and Ni did not change significantly. Significant correlations were found between concentrations of Cu and Zn in corn shoot and oxide and total Cu fractions, and all chemical fractions of Zn in fly ash-stabilized sludge, respectively. Hence, ash amendment significantly reduced the availability of heavy metals by chemical modification of their chemical speciation into less available forms.     

Toxicities and tolerances of Cd, Cu, Pb and Zn in a primary producer (Isochrysis galbana) and in a primary consumer (Perna viridis)

Studies on toxicities and tolerances of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in the brown alga Isochrysis galbana and in the green-lipped mussel Perna viridis were conducted by short-term bioassays using endpoints growth production and mortality, respectively. The 5-day EC(50) and 24-h LC(50) of these heavy metals were determined in the brown alga and mussel, respectively. The EC(50) values calculated for the alga were 0.74 mg/l for Cd, 0.91 mg/l for Cu, 1.40 mg/l for Pb and 0.60 mg/l for Zn. The LC(50) values for the mussels were 1.53 mg/l for Cd, 0.25 mg/l for Cu, 4.12 mg/l for Pb and 3.20 mg/l for Zn. These LC(50) values were within the concentration ranges as reported by other authors who used P. viridis as the test organism. Based on these EC(50) and LC(50) values, the alga was most sensitive to Zn, followed by Cd, Cu and Pb while the mussel was most sensitive to Cu, followed by Cd, Zn and Pb. Differences in the trophic levels, metal handling strategies, biology and ecology of the primary producer (brown alga) and the primary consumer (mussel) are believed to be the plausible causes for the different toxicities and tolerances of the metals studied.     

The effect of operating conditions on the capture of metals with limestone during incineration

The objective of this work was to experimentally study the effect of different operating conditions on sorbent (limestone) to capture metals and the formation of hexavalent chromium during fluidized bed incineration of wastes containing Pb, Cd, Cu, and Cr. The operating parameters evaluated included: 1) addition of organic chloride (PVC); 2) addition of inorganic chloride (NaCl); 3) addition of sulfide (Na₂S); 4) size of sorbent; and, 5) air factor. The experiments were carried out in a pilot scale fluidized bed incinerator with air pollution control devices of two consecutive cyclones and a wet scrubber. Experimental results indicated that limestone could effectively capture most heavy metals Pb, Cr, and Cd in the sand bed. The addition of organic chloride (PVC) and inorganic chloride (NaCl) in feedstock caused different consequences. The former decreased the adsorption efficiency, while the latter increased the adsorption efficiency of limestone in the sand bed. Moreover, the presence of sulfide (Na₂S) was helpful in controlling metals during incineration. Little hexavalent chromium is formed during incineration, but the presence of organic chloride PVC produced more Cr(VI) than inorganic chloride NaCl.     

Correlation of the partitioning of dissolved organic matter fractions with the desorption of Cd,Cu, Ni,Pb and Zn from 18 Dutch soils

Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was also concentrated onto a macroreticular resin and fractionation into three operationally defined fractions: hydrophilic acids (Hyd), humic acids (HA) and fulvic acids (FA). In this manner, change in absolute solution concentration and relative percentage for each fraction could be calculated as a function of extraction equilibrium pH. The soils were also analyzed for solid phase total organic carbon and total recoverable metals (EPA Method 3051). Partitioning coefficients were calculated for the metals and organic carbon (OC) based on solid phase concentrations (less the metal or OC removed by the extraction) divided by solution concentrations. Cu and Pb concentrations in solution as a function of extract equilibrium pH are greatest at low and high pH resulting in parabolic desorption/dissolution curves. While processes such as proton competition and proton promoted dissolution can account for high solution metal concentrations at low pH, these processes cannot account for higher Cu and Pb concentrations at high pH. DOC increases with increasing pH, concurrently with the increase in Cu and Pb solution concentrations. While the absolute concentrations of FA and HA generally increase with increasing pH, the relative proportional increase is greatest for HA . Variation in HA concentrations spans three orders of magnitude while FA concentrations vary an order of magnitude over the pH range examined. Correlation analysis strongly suggests that HA plays a major role in increasing the concentration of solution Cu and Pb with increasing pH in the 18 soils studied. The percentage of the OC that was due to FA was nearly constant over a wide pH range although the FA concentration increased with increasing pH and its concentration was greater than that of the HA fraction at lower pH values (pH = 3-5). Thus, in more acidic environments, FA may play a larger role than HA in governing organo-metallic interactions. For Cd, Ni, and Zn, the desorption/dissolution pattern shows high metal solution concentrations at low pH with slight increases in solution concentrations at extremely high pH values (pH>10). The results presented here suggest that the effects of dissolved organic carbon on the mobilization of Cd, Ni, and Zn may only occur in systems governed by very high pH. At high pH, it is difficult to distinguish in this study whether the slightly increased solution-phase concentrations of these cations is due to DOC or hydrolysis reactions. These high pH environments would rarely occur in natural settings.     

Distribution of Cd,Cu, Fe,Mn, Pb and Zn in selected tissues of juvenile whales stranded in the SE Gulf of California (Mexico)

With the aim of knowing the concentration and distribution of essential and nonessential metals in selected tissues of whales, analysis of Cd, Cu, Fe, Mn, Pb and Zn were carried out in kidney, liver and muscle of the gray whale Eschrichtius robustus and the sperm whale Physeter catodon. Whales were found stranded in the southeast Gulf of California. Individuals were in a juvenile stage; mean length of whales was 9.3 m for E. robustus and 7 m for P. catodon. Sequence of metal concentrations was Fe>Zn>Cu>Mn>Cd>Pb in E. robustus, and Fe>Zn>Cu>Cd>Mn>Pb in P. catodon. In E. robustus, highest concentrations of Cu, Mn, Pb and Zn (17.2, 19.6, 0.9 and 388 microg g(-1), respectively) were measured in liver, Cd (5.7 microg g(-1)) in kidney and Fe (1009 microg g(-1)) in muscle. In P. catodon, the highest levels of Cu, Fe and Pb (48.6, 5200 and 4.2 microg g(-1), respectively) were found in liver, Cd and Zn (94 and 183 microg g(-1)) in kidney and Mn (8 microg g(-1)) in muscle. Metal concentrations reported here were not considered to contribute to the stranding of specimens.     

Photosynthesis and growth responses of giant reed (Arundo donax L.) to the heavy metals Cd and Ni

Giant reed (Arundo donax L.) was grown on surface soil and irrigated with mixed heavy metal solutions of Cd(II) and Ni(II) to study the impact of these heavy metals on its growth and photosynthesis. The tested concentrations were 5, 50, and 100 ppm for each heavy metal against the control and resulted in high cadmium and nickel (DTPA extractable) concentrations in the top zone of the pot soil. The examined parameters, namely, stem height and diameter, number of nodes, fresh and dry weight of leaves, and net photosynthesis (Pn) were not affected, indicating that plants tolerate the high concentrations of Cd and Ni. As giant reed plants are very promising energy plants, they can be cultivated in contaminated soils to provide biomass for energy production purposes.     

The effect of complex formation on the adsorption characteristics of heavy metals

In most aqueous environmental systems, inorganic and organic metal complexes represent a significant contribution to the total soluble metal. Metal adsorption is often a highly pH-dependent phenomena. Such behavior can generally be attributed to changes in metal speciation with solution acidity as well as variation in the extent of surface protonation. Thus, because adsorbability may vary drastically between different metal species, (e.g. Cu²⁺ (aq) compared to CuOH⁺) a knowledge of metal species distribution is essential to understanding and interpreting metal adsorption behavior.Organic complexation has been reported to enhance, suppress and have no perceptible effect on trace metal adsorption. Such differences arise because adsorption depends on factors such as the ligand/metal ratio, adsorbability of the free ligand, and various solution parameters (e.g. pH). Most important in determining the effect of complexation on adsorption is the adsorbability of the resulting complexes. Thus, it is difficult to make generalizations about the influence of organic complexation on metal adsorption.Adsorption of metal complexes is frequently reported to be predominantly coulombic in nature; that is, binding of an anionic or cationic complex to an oppositely charged colloidal particle. However, electrostatic forces can often represent an insignificant contribution to the total free energy of adsorption and can be overshadowed by chemical reactions with the surface, hydrogen bonding, and hydrophobic effects.     

Hyperaccumulation of Pb, Zn and Cd in herbaceous grown on lead-zinc mining area in Yunnan, China

A field survey of herbaceous growing on lead-zinc mining area in Yunnan, China were conducted to identify species accumulating exceptionally large concentrations of Pb, Zn and Cd in shoots. In total, 220 plant samples of 129 species of 50 families and 220 soil samples in which the plants were growing were collected. According to accumulation concentration in plant shoots and the concentration time levels compared to plants from non-polluted environments, 21 plant samples of 16 species were chosen as best-performing specimens, 11 plant samples of 10 species for Pb, 5 plant samples of 4 species for Zn and 5 plant samples of 5 species for Cd. Sonchus asper (L.) Hill in Qilinkeng had hyperaccumulation capacity to Pb and Zn. Corydalis pterygopetala Franch in Paomaping had hyperaccumulation capacity to Zn and Cd. All 5 Cd hyperaccumulators came from Lanping lead-zinc mining area. Out of 11 Pb hyperaccumulators, 7 came from Minbingying of Huice lead-zinc mining area. The average of the concentration time levels compared to plants from non-polluted environments were higher than 10 times in all plant samples, the concentration time levels changed from 203 times to 620 times for Pb, from 50 times to 70 times for Zn and from 145 times to 330 times for Cd. Out of 21 plant samples, translocation factor changed from 0.35 to 1.90, only translocation factor of 7 plant samples were higher than 1. Enrichment coefficients of all samples were lower than 1. These plant species were primarily heavy metal hyperaccumulator, and will be used in phytoremediation of the metallic pollutants in soils after further research in accumulation mechanism.     

Effects of Se and Zn supplementation on the antagonism against Pb and Cd in vegetables

The antagonistic effects of supplementation of Zn and Se to the soil on vegetables were studied in this work. In the pot experiment, Se (Se4+) and Zn (Zn2+) were applied, respectively, to the soil, in which the Chinese cabbage (Brassica rapa) and the lettuce (Lactuca sativa L.) were planted. As a result, Se and Zn were enriched evidently in the two vegetables. The contents of Pb and Cd in the two vegetables were decreased markedly while contents of some healthy mineral elements, like Mn and Mg, were increased to some extent when Se and Zn were applied. The antagonism of Se and Zn against Pb and Cd in plants was suggested. The farmland experiment on the lettuce was conducted to explore further the effect of supplementation of Zn and Se under the actual field conditions. Result came out to be that the enrichment of Zn and Se restrained the accumulation of Pb and Cd in the lettuce remarkably, as well as enhanced the absorption of some other nutritional elements, like Fe, Mn, Cu, Ca and Mg. Therefore, application of Se and Zn was proved to be an effective and feasible method to improve trace elements nutrition in the vegetables.     

Effects of readily dispersible colloid on adsorption and transport of Zn, Cu, and Pb in soils

Soil colloids (<0.002 mm) were extracted from three types of soils to make the colloid-bound forms of Zn, Cu, and Pb solution. The clay mineral types and composition of the colloids, the adsorption characteristics of the colloids, and the effect of readily dispersible colloid on the transport of metals and the quality of the soils and groundwater were studied. The results showed that the adsorption capacity of Cu, Zn, and Pb was greater for the Aquic Vertisols (Shajiang Black soil) as compared to the Udic Luvisols (Brown soil) and Usdic Luvisols (Cinnamon soil), due to the difference of clay content and clay mineral composition in the different soils. The adsorption capacity of Pb was much higher than that of Zn and Cu for the same soils, which would contribute to the chemical properties of metals and specific adsorption characters of the colloids. The mobility of Zn in soils was greater than that of Cu and Pb, while similar trend was found in the transportation processes for Zn and Cu. The concentration of Zn and Cu in leachates increased as the leaching solution volume increased, but the migration of Pb was negligible, and the concentration of Pb could not been detected in leachates even after 7.5 pore volume leaching solution. The influence of mobility on Zn and Cu transport was different for different type of colloids. The mobility caused by readily dispersible colloids from Aquic Vertisols was greater as compared to that of Udic Luvisols and Usdic Luvisols. Analysis of soils after column leaching indicated that Zn was distributed much deeper than Cu, but Pb was almost not migrated, and mainly accumulated in the soil surface. Therefore, Zn had greater tendency for the groundwater pollution than Cu and Pb, and Pb tends to contaminate the surface soils.     

Comparative studies on the concentration of rare earth elements and heavy metals in the atmospheric particulate matter in Beijing, China, and in Delft, The Netherlands

Atmospheric particulate matter (APM) was collected at three sampling sites in Beijing, China, from February to June 1998. The concentrations of rare earth elements (REE) and cobalt (Co), zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the APM were determined by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained in Beijing, China, were compared to that obtained in Delft, the Netherlands, in 1997. The influence of coal combustion was considered. The results demonstrated that the content of APM, the concentrations of REE and Co, Zn, Cd, Pb in the APM in Beijing, China, were higher than that in Delft, the Netherlands. From the ratios of La to Ce, and La to Sm, which may be used as tracers for the origin of the REE, it is concluded that the origins of REE in China differ from those in the Netherlands.     

Correlations between speciation of Cd,Cu, Pb And Zn in sediment and their concentrations in total soft tissue of green-lipped mussel Perna viridis from the west coast of Peninsular Malaysia

Total concentrations and speciation of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in surface sediment samples were correlated with the respective metal measured in the total soft tissue of the green-lipped mussel Perna viridis, collected from water off the west coast of Peninsular Malaysia. The aim of this study is to relate the possible differences in the accumulation patterns of the heavy metals in P. viridis to those in the surface sediment. The sequential extraction technique was employed to fractionate the sediment into 'freely leachable and exchangeable' (EFLE), 'acid-reducible,' 'oxidisable-organic' and 'resistant' fractions. The results showed that significant (P<.05) correlations were observed between Cd in P. viridis and Cd in the sediment (EFLE fraction and total Cd), Cu in P viridis and Cu in the sediment (EFLE and 'acid-reducible' fractions and total Cu) and Pb in P viridis and Pb in the sediment ('oxidisable-organic' fraction and total Pb). No significant correlation (P > .05) was found between Zn in P viridis and all the sediment geochemical fractions of Zn and total Zn in the sediment. This indicated that Zn was possibly regulated from the soft tissue of P. viridis. The present results supported the use of P viridis as a suitable biomonitoring agent for Cd, Cu and Pb.